go.mod: update golang.org/x dependencies

Update golang.org/x dependencies to their latest tagged versions.

Change-Id: Ib20227810c7e72942dd6fc33731fc613784aedec
Reviewed-on: https://go-review.googlesource.com/c/crypto/+/576515
Reviewed-by: Than McIntosh <thanm@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Gopher Robot <gobot@golang.org>

acme/version_go112.go

@@ -3,7 +3,6 @@
 // license that can be found in the LICENSE file.
 
 //go:build go1.12
-// +build go1.12
 
 package acme
 

argon2/blamka_amd64.go

@@ -3,7 +3,6 @@
 // license that can be found in the LICENSE file.
 
 //go:build amd64 && gc && !purego
-// +build amd64,gc,!purego
 
 package argon2
 

argon2/blamka_amd64.s

@@ -3,7 +3,6 @@
 // license that can be found in the LICENSE file.
 
 //go:build amd64 && gc && !purego
-// +build amd64,gc,!purego
 
 #include "textflag.h"
 
@@ -200,8 +199,8 @@ TEXT ·mixBlocksSSE2(SB), 4, $0-32
 	MOVQ out+0(FP), DX
 	MOVQ a+8(FP), AX
 	MOVQ b+16(FP), BX
-	MOVQ a+24(FP), CX
-	MOVQ $128, BP
+	MOVQ c+24(FP), CX
+	MOVQ $128, DI
 
 loop:
 	MOVOU 0(AX), X0
@@ -214,7 +213,7 @@ loop:
 	ADDQ  $16, BX
 	ADDQ  $16, CX
 	ADDQ  $16, DX
-	SUBQ  $2, BP
+	SUBQ  $2, DI
 	JA    loop
 	RET
 
@@ -223,8 +222,8 @@ TEXT ·xorBlocksSSE2(SB), 4, $0-32
 	MOVQ out+0(FP), DX
 	MOVQ a+8(FP), AX
 	MOVQ b+16(FP), BX
-	MOVQ a+24(FP), CX
-	MOVQ $128, BP
+	MOVQ c+24(FP), CX
+	MOVQ $128, DI
 
 loop:
 	MOVOU 0(AX), X0
@@ -239,6 +238,6 @@ loop:
 	ADDQ  $16, BX
 	ADDQ  $16, CX
 	ADDQ  $16, DX
-	SUBQ  $2, BP
+	SUBQ  $2, DI
 	JA    loop
 	RET

argon2/blamka_ref.go

@@ -3,7 +3,6 @@
 // license that can be found in the LICENSE file.
 
 //go:build !amd64 || purego || !gc
-// +build !amd64 purego !gc
 
 package argon2
 

blake2b/blake2bAVX2_amd64.go

@@ -2,8 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:build go1.7 && amd64 && gc && !purego
-// +build go1.7,amd64,gc,!purego
+//go:build amd64 && gc && !purego
 
 package blake2b
 

blake2b/blake2bAVX2_amd64.s

@@ -2,8 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:build go1.7 && amd64 && gc && !purego
-// +build go1.7,amd64,gc,!purego
+//go:build amd64 && gc && !purego
 
 #include "textflag.h"
 

blake2b/blake2b_amd64.go

@@ -1,25 +0,0 @@
-// Copyright 2016 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-//go:build !go1.7 && amd64 && gc && !purego
-// +build !go1.7,amd64,gc,!purego
-
-package blake2b
-
-import "golang.org/x/sys/cpu"
-
-func init() {
-	useSSE4 = cpu.X86.HasSSE41
-}
-
-//go:noescape
-func hashBlocksSSE4(h *[8]uint64, c *[2]uint64, flag uint64, blocks []byte)
-
-func hashBlocks(h *[8]uint64, c *[2]uint64, flag uint64, blocks []byte) {
-	if useSSE4 {
-		hashBlocksSSE4(h, c, flag, blocks)
-	} else {
-		hashBlocksGeneric(h, c, flag, blocks)
-	}
-}

blake2b/blake2b_amd64.s

@@ -3,7 +3,6 @@
 // license that can be found in the LICENSE file.
 
 //go:build amd64 && gc && !purego
-// +build amd64,gc,!purego
 
 #include "textflag.h"
 

blake2b/blake2b_ref.go

@@ -3,7 +3,6 @@
 // license that can be found in the LICENSE file.
 
 //go:build !amd64 || purego || !gc
-// +build !amd64 purego !gc
 
 package blake2b
 

blake2b/register.go

@@ -2,9 +2,6 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:build go1.9
-// +build go1.9
-
 package blake2b
 
 import (

blake2s/blake2s_386.go

@@ -3,7 +3,6 @@
 // license that can be found in the LICENSE file.
 
 //go:build 386 && gc && !purego
-// +build 386,gc,!purego
 
 package blake2s
 

blake2s/blake2s_386.s

@@ -3,7 +3,6 @@
 // license that can be found in the LICENSE file.
 
 //go:build 386 && gc && !purego
-// +build 386,gc,!purego
 
 #include "textflag.h"
 

blake2s/blake2s_amd64.go

@@ -3,7 +3,6 @@
 // license that can be found in the LICENSE file.
 
 //go:build amd64 && gc && !purego
-// +build amd64,gc,!purego
 
 package blake2s
 

blake2s/blake2s_amd64.s

@@ -3,7 +3,6 @@
 // license that can be found in the LICENSE file.
 
 //go:build amd64 && gc && !purego
-// +build amd64,gc,!purego
 
 #include "textflag.h"
 

blake2s/blake2s_ref.go

@@ -3,7 +3,6 @@
 // license that can be found in the LICENSE file.
 
 //go:build (!amd64 && !386) || !gc || purego
-// +build !amd64,!386 !gc purego
 
 package blake2s
 

blake2s/register.go

@@ -3,7 +3,6 @@
 // license that can be found in the LICENSE file.
 
 //go:build go1.9
-// +build go1.9
 
 package blake2s
 

chacha20/chacha_arm64.go

@@ -3,7 +3,6 @@
 // license that can be found in the LICENSE file.
 
 //go:build gc && !purego
-// +build gc,!purego
 
 package chacha20
 

chacha20/chacha_arm64.s

@@ -3,7 +3,6 @@
 // license that can be found in the LICENSE file.
 
 //go:build gc && !purego
-// +build gc,!purego
 
 #include "textflag.h"
 

chacha20/chacha_noasm.go

@@ -3,7 +3,6 @@
 // license that can be found in the LICENSE file.
 
 //go:build (!arm64 && !s390x && !ppc64le) || !gc || purego
-// +build !arm64,!s390x,!ppc64le !gc purego
 
 package chacha20
 

chacha20/chacha_ppc64le.go

@@ -3,7 +3,6 @@
 // license that can be found in the LICENSE file.
 
 //go:build gc && !purego
-// +build gc,!purego
 
 package chacha20
 

chacha20/chacha_ppc64le.s

@@ -20,7 +20,6 @@
 // due to the calling conventions and initialization of constants.
 
 //go:build gc && !purego
-// +build gc,!purego
 
 #include "textflag.h"
 
@@ -34,6 +33,9 @@
 #define CONSTBASE  R16
 #define BLOCKS R17
 
+// for VPERMXOR
+#define MASK  R18
+
 DATA consts<>+0x00(SB)/8, $0x3320646e61707865
 DATA consts<>+0x08(SB)/8, $0x6b20657479622d32
 DATA consts<>+0x10(SB)/8, $0x0000000000000001
@@ -54,7 +56,11 @@ DATA consts<>+0x80(SB)/8, $0x6b2065746b206574
 DATA consts<>+0x88(SB)/8, $0x6b2065746b206574
 DATA consts<>+0x90(SB)/8, $0x0000000100000000
 DATA consts<>+0x98(SB)/8, $0x0000000300000002
-GLOBL consts<>(SB), RODATA, $0xa0
+DATA consts<>+0xa0(SB)/8, $0x5566774411223300
+DATA consts<>+0xa8(SB)/8, $0xddeeffcc99aabb88
+DATA consts<>+0xb0(SB)/8, $0x6677445522330011
+DATA consts<>+0xb8(SB)/8, $0xeeffccddaabb8899
+GLOBL consts<>(SB), RODATA, $0xc0
 
 //func chaCha20_ctr32_vsx(out, inp *byte, len int, key *[8]uint32, counter *uint32)
 TEXT ·chaCha20_ctr32_vsx(SB),NOSPLIT,$64-40
@@ -71,6 +77,9 @@ TEXT ·chaCha20_ctr32_vsx(SB),NOSPLIT,$64-40
 	MOVD $48, R10
 	MOVD $64, R11
 	SRD $6, LEN, BLOCKS
+	// for VPERMXOR
+	MOVD $consts<>+0xa0(SB), MASK
+	MOVD $16, R20
 	// V16
 	LXVW4X (CONSTBASE)(R0), VS48
 	ADD $80,CONSTBASE
@@ -88,6 +97,10 @@ TEXT ·chaCha20_ctr32_vsx(SB),NOSPLIT,$64-40
 	// V28
 	LXVW4X (CONSTBASE)(R11), VS60
 
+	// Load mask constants for VPERMXOR
+	LXVW4X (MASK)(R0), V20
+	LXVW4X (MASK)(R20), V21
+
 	// splat slot from V19 -> V26
 	VSPLTW $0, V19, V26
 
@@ -98,7 +111,7 @@ TEXT ·chaCha20_ctr32_vsx(SB),NOSPLIT,$64-40
 
 	MOVD $10, R14
 	MOVD R14, CTR
-
+	PCALIGN $16
 loop_outer_vsx:
 	// V0, V1, V2, V3
 	LXVW4X (R0)(CONSTBASE), VS32
@@ -129,22 +142,17 @@ loop_outer_vsx:
 	VSPLTISW $12, V28
 	VSPLTISW $8, V29
 	VSPLTISW $7, V30
-
+	PCALIGN $16
 loop_vsx:
 	VADDUWM V0, V4, V0
 	VADDUWM V1, V5, V1
 	VADDUWM V2, V6, V2
 	VADDUWM V3, V7, V3
 
-	VXOR V12, V0, V12
-	VXOR V13, V1, V13
-	VXOR V14, V2, V14
-	VXOR V15, V3, V15
-
-	VRLW V12, V27, V12
-	VRLW V13, V27, V13
-	VRLW V14, V27, V14
-	VRLW V15, V27, V15
+	VPERMXOR V12, V0, V21, V12
+	VPERMXOR V13, V1, V21, V13
+	VPERMXOR V14, V2, V21, V14
+	VPERMXOR V15, V3, V21, V15
 
 	VADDUWM V8, V12, V8
 	VADDUWM V9, V13, V9
@@ -166,15 +174,10 @@ loop_vsx:
 	VADDUWM V2, V6, V2
 	VADDUWM V3, V7, V3
 
-	VXOR V12, V0, V12
-	VXOR V13, V1, V13
-	VXOR V14, V2, V14
-	VXOR V15, V3, V15
-
-	VRLW V12, V29, V12
-	VRLW V13, V29, V13
-	VRLW V14, V29, V14
-	VRLW V15, V29, V15
+	VPERMXOR V12, V0, V20, V12
+	VPERMXOR V13, V1, V20, V13
+	VPERMXOR V14, V2, V20, V14
+	VPERMXOR V15, V3, V20, V15
 
 	VADDUWM V8, V12, V8
 	VADDUWM V9, V13, V9
@@ -196,15 +199,10 @@ loop_vsx:
 	VADDUWM V2, V7, V2
 	VADDUWM V3, V4, V3
 
-	VXOR V15, V0, V15
-	VXOR V12, V1, V12
-	VXOR V13, V2, V13
-	VXOR V14, V3, V14
-
-	VRLW V15, V27, V15
-	VRLW V12, V27, V12
-	VRLW V13, V27, V13
-	VRLW V14, V27, V14
+	VPERMXOR V15, V0, V21, V15
+	VPERMXOR V12, V1, V21, V12
+	VPERMXOR V13, V2, V21, V13
+	VPERMXOR V14, V3, V21, V14
 
 	VADDUWM V10, V15, V10
 	VADDUWM V11, V12, V11
@@ -226,15 +224,10 @@ loop_vsx:
 	VADDUWM V2, V7, V2
 	VADDUWM V3, V4, V3
 
-	VXOR V15, V0, V15
-	VXOR V12, V1, V12
-	VXOR V13, V2, V13
-	VXOR V14, V3, V14
-
-	VRLW V15, V29, V15
-	VRLW V12, V29, V12
-	VRLW V13, V29, V13
-	VRLW V14, V29, V14
+	VPERMXOR V15, V0, V20, V15
+	VPERMXOR V12, V1, V20, V12
+	VPERMXOR V13, V2, V20, V13
+	VPERMXOR V14, V3, V20, V14
 
 	VADDUWM V10, V15, V10
 	VADDUWM V11, V12, V11
@@ -250,48 +243,48 @@ loop_vsx:
 	VRLW V6, V30, V6
 	VRLW V7, V30, V7
 	VRLW V4, V30, V4
-	BC   16, LT, loop_vsx
+	BDNZ   loop_vsx
 
 	VADDUWM V12, V26, V12
 
-	WORD $0x13600F8C		// VMRGEW V0, V1, V27
-	WORD $0x13821F8C		// VMRGEW V2, V3, V28
+	VMRGEW V0, V1, V27
+	VMRGEW V2, V3, V28
 
-	WORD $0x10000E8C		// VMRGOW V0, V1, V0
-	WORD $0x10421E8C		// VMRGOW V2, V3, V2
+	VMRGOW V0, V1, V0
+	VMRGOW V2, V3, V2
 
-	WORD $0x13A42F8C		// VMRGEW V4, V5, V29
-	WORD $0x13C63F8C		// VMRGEW V6, V7, V30
+	VMRGEW V4, V5, V29
+	VMRGEW V6, V7, V30
 
 	XXPERMDI VS32, VS34, $0, VS33
 	XXPERMDI VS32, VS34, $3, VS35
 	XXPERMDI VS59, VS60, $0, VS32
 	XXPERMDI VS59, VS60, $3, VS34
 
-	WORD $0x10842E8C		// VMRGOW V4, V5, V4
-	WORD $0x10C63E8C		// VMRGOW V6, V7, V6
+	VMRGOW V4, V5, V4
+	VMRGOW V6, V7, V6
 
-	WORD $0x13684F8C		// VMRGEW V8, V9, V27
-	WORD $0x138A5F8C		// VMRGEW V10, V11, V28
+	VMRGEW V8, V9, V27
+	VMRGEW V10, V11, V28
 
 	XXPERMDI VS36, VS38, $0, VS37
 	XXPERMDI VS36, VS38, $3, VS39
 	XXPERMDI VS61, VS62, $0, VS36
 	XXPERMDI VS61, VS62, $3, VS38
 
-	WORD $0x11084E8C		// VMRGOW V8, V9, V8
-	WORD $0x114A5E8C		// VMRGOW V10, V11, V10
+	VMRGOW V8, V9, V8
+	VMRGOW V10, V11, V10
 
-	WORD $0x13AC6F8C		// VMRGEW V12, V13, V29
-	WORD $0x13CE7F8C		// VMRGEW V14, V15, V30
+	VMRGEW V12, V13, V29
+	VMRGEW V14, V15, V30
 
 	XXPERMDI VS40, VS42, $0, VS41
 	XXPERMDI VS40, VS42, $3, VS43
 	XXPERMDI VS59, VS60, $0, VS40
 	XXPERMDI VS59, VS60, $3, VS42
 
-	WORD $0x118C6E8C		// VMRGOW V12, V13, V12
-	WORD $0x11CE7E8C		// VMRGOW V14, V15, V14
+	VMRGOW V12, V13, V12
+	VMRGOW V14, V15, V14
 
 	VSPLTISW $4, V27
 	VADDUWM V26, V27, V26
@@ -432,7 +425,7 @@ tail_vsx:
 	ADD $-1, R11, R12
 	ADD $-1, INP
 	ADD $-1, OUT
-
+	PCALIGN $16
 looptail_vsx:
 	// Copying the result to OUT
 	// in bytes.
@@ -440,7 +433,7 @@ looptail_vsx:
 	MOVBZU 1(INP), TMP
 	XOR    KEY, TMP, KEY
 	MOVBU  KEY, 1(OUT)
-	BC     16, LT, looptail_vsx
+	BDNZ   looptail_vsx
 
 	// Clear the stack values
 	STXVW4X VS48, (R11)(R0)

chacha20/chacha_s390x.go

@@ -3,7 +3,6 @@
 // license that can be found in the LICENSE file.
 
 //go:build gc && !purego
-// +build gc,!purego
 
 package chacha20
 

chacha20/chacha_s390x.s

@@ -3,7 +3,6 @@
 // license that can be found in the LICENSE file.
 
 //go:build gc && !purego
-// +build gc,!purego
 
 #include "go_asm.h"
 #include "textflag.h"

chacha20poly1305/chacha20poly1305_amd64.go

@@ -3,7 +3,6 @@
 // license that can be found in the LICENSE file.
 
 //go:build gc && !purego
-// +build gc,!purego
 
 package chacha20poly1305
 

chacha20poly1305/chacha20poly1305_amd64.s

@@ -5,7 +5,6 @@
 // This file was originally from https://golang.org/cl/24717 by Vlad Krasnov of CloudFlare.
 
 //go:build gc && !purego
-// +build gc,!purego
 
 #include "textflag.h"
 // General register allocation
@@ -184,11 +183,31 @@ GLOBL ·andMask<>(SB), (NOPTR+RODATA), $240
 #define shiftD1Right BYTE $0x66; BYTE $0x45; BYTE $0x0f; BYTE $0x3a; BYTE $0x0f; BYTE $0xd2; BYTE $0x04 // PALIGNR $4, X10, X10
 #define shiftD2Right BYTE $0x66; BYTE $0x45; BYTE $0x0f; BYTE $0x3a; BYTE $0x0f; BYTE $0xdb; BYTE $0x04 // PALIGNR $4, X11, X11
 #define shiftD3Right BYTE $0x66; BYTE $0x45; BYTE $0x0f; BYTE $0x3a; BYTE $0x0f; BYTE $0xff; BYTE $0x04 // PALIGNR $4, X15, X15
+
 // Some macros
+
+// ROL rotates the uint32s in register R left by N bits, using temporary T.
+#define ROL(N, R, T) \
+	MOVO R, T; PSLLL $(N), T; PSRLL $(32-(N)), R; PXOR T, R
+
+// ROL16 rotates the uint32s in register R left by 16, using temporary T if needed.
+#ifdef GOAMD64_v2
+#define ROL16(R, T) PSHUFB ·rol16<>(SB), R
+#else
+#define ROL16(R, T) ROL(16, R, T)
+#endif
+
+// ROL8 rotates the uint32s in register R left by 8, using temporary T if needed.
+#ifdef GOAMD64_v2
+#define ROL8(R, T) PSHUFB ·rol8<>(SB), R
+#else
+#define ROL8(R, T) ROL(8, R, T)
+#endif
+
 #define chachaQR(A, B, C, D, T) \
-	PADDD B, A; PXOR A, D; PSHUFB ·rol16<>(SB), D                            \
+	PADDD B, A; PXOR A, D; ROL16(D, T) \
 	PADDD D, C; PXOR C, B; MOVO B, T; PSLLL $12, T; PSRLL $20, B; PXOR T, B \
-	PADDD B, A; PXOR A, D; PSHUFB ·rol8<>(SB), D                             \
+	PADDD B, A; PXOR A, D; ROL8(D, T) \
 	PADDD D, C; PXOR C, B; MOVO B, T; PSLLL $7, T; PSRLL $25, B; PXOR T, B
 
 #define chachaQR_AVX2(A, B, C, D, T) \

chacha20poly1305/chacha20poly1305_noasm.go

@@ -3,7 +3,6 @@
 // license that can be found in the LICENSE file.
 
 //go:build !amd64 || !gc || purego
-// +build !amd64 !gc purego
 
 package chacha20poly1305
 

cryptobyte/asn1.go

@@ -733,13 +733,14 @@ func (s *String) ReadOptionalASN1OctetString(out *[]byte, outPresent *bool, tag
 	return true
 }
 
-// ReadOptionalASN1Boolean sets *out to the value of the next ASN.1 BOOLEAN or,
-// if the next bytes are not an ASN.1 BOOLEAN, to the value of defaultValue.
-// It reports whether the operation was successful.
-func (s *String) ReadOptionalASN1Boolean(out *bool, defaultValue bool) bool {
+// ReadOptionalASN1Boolean attempts to read an optional ASN.1 BOOLEAN
+// explicitly tagged with tag into out and advances. If no element with a
+// matching tag is present, it sets "out" to defaultValue instead. It reports
+// whether the read was successful.
+func (s *String) ReadOptionalASN1Boolean(out *bool, tag asn1.Tag, defaultValue bool) bool {
 	var present bool
 	var child String
-	if !s.ReadOptionalASN1(&child, &present, asn1.BOOLEAN) {
+	if !s.ReadOptionalASN1(&child, &present, tag) {
 		return false
 	}
 
@@ -748,7 +749,7 @@ func (s *String) ReadOptionalASN1Boolean(out *bool, defaultValue bool) bool {
 		return true
 	}
 
-	return s.ReadASN1Boolean(out)
+	return child.ReadASN1Boolean(out)
 }
 
 func (s *String) readASN1(out *String, outTag *asn1.Tag, skipHeader bool) bool {

cryptobyte/asn1_test.go

@@ -115,6 +115,28 @@ func TestReadASN1OptionalInteger(t *testing.T) {
 	}
 }
 
+const defaultBool = false
+
+var optionalBoolTestData = []readASN1Test{
+	{"empty", []byte{}, 0xa0, true, false},
+	{"invalid", []byte{0xa1, 0x3, 0x1, 0x2, 0x7f}, 0xa1, false, defaultBool},
+	{"missing", []byte{0xa1, 0x3, 0x1, 0x1, 0x7f}, 0xa0, true, defaultBool},
+	{"present", []byte{0xa1, 0x3, 0x1, 0x1, 0xff}, 0xa1, true, true},
+}
+
+func TestReadASN1OptionalBoolean(t *testing.T) {
+	for _, test := range optionalBoolTestData {
+		t.Run(test.name, func(t *testing.T) {
+			in := String(test.in)
+			var out bool
+			ok := in.ReadOptionalASN1Boolean(&out, test.tag, defaultBool)
+			if ok != test.ok || ok && out != test.out.(bool) {
+				t.Errorf("in.ReadOptionalASN1Boolean() = %v, want %v; out = %v, want %v", ok, test.ok, out, test.out)
+			}
+		})
+	}
+}
+
 func TestReadASN1IntegerSigned(t *testing.T) {
 	testData64 := []struct {
 		in  []byte

curve25519/internal/field/_asm/go.mod

@@ -1,10 +1,16 @@
 module asm
 
-go 1.16
+go 1.18
 
 require (
-	github.com/mmcloughlin/avo v0.4.0
-	golang.org/x/crypto v0.0.0
+	github.com/mmcloughlin/avo v0.5.0
+	golang.org/x/crypto v0.1.0
 )
 
-replace golang.org/x/crypto v0.0.0 => ../../../..
+require (
+	golang.org/x/mod v0.8.0 // indirect
+	golang.org/x/sys v0.14.0 // indirect
+	golang.org/x/tools v0.6.0 // indirect
+)
+
+replace golang.org/x/crypto v0.1.0 => ../../../..

curve25519/internal/field/_asm/go.sum

@@ -1,34 +1,51 @@
-github.com/mmcloughlin/avo v0.4.0 h1:jeHDRktVD+578ULxWpQHkilor6pkdLF7u7EiTzDbfcU=
-github.com/mmcloughlin/avo v0.4.0/go.mod h1:RW9BfYA3TgO9uCdNrKU2h6J8cPD8ZLznvfgHAeszb1s=
-github.com/yuin/goldmark v1.4.0/go.mod h1:mwnBkeHKe2W/ZEtQ+71ViKU8L12m81fl3OWwC1Zlc8k=
-golang.org/x/arch v0.0.0-20210923205945-b76863e36670/go.mod h1:5om86z9Hs0C8fWVUuoMHwpExlXzs5Tkyp9hOrfG7pp8=
+github.com/mmcloughlin/avo v0.5.0 h1:nAco9/aI9Lg2kiuROBY6BhCI/z0t5jEvJfjWbL8qXLU=
+github.com/mmcloughlin/avo v0.5.0/go.mod h1:ChHFdoV7ql95Wi7vuq2YT1bwCJqiWdZrQ1im3VujLYM=
+github.com/yuin/goldmark v1.4.13/go.mod h1:6yULJ656Px+3vBD8DxQVa3kxgyrAnzto9xy5taEt/CY=
+golang.org/x/arch v0.1.0/go.mod h1:5om86z9Hs0C8fWVUuoMHwpExlXzs5Tkyp9hOrfG7pp8=
 golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
-golang.org/x/crypto v0.0.0-20191011191535-87dc89f01550/go.mod h1:yigFU9vqHzYiE8UmvKecakEJjdnWj3jj499lnFckfCI=
-golang.org/x/mod v0.4.2 h1:Gz96sIWK3OalVv/I/qNygP42zyoKp3xptRVCWRFEBvo=
-golang.org/x/mod v0.4.2/go.mod h1:s0Qsj1ACt9ePp/hMypM3fl4fZqREWJwdYDEqhRiZZUA=
-golang.org/x/net v0.0.0-20190404232315-eb5bcb51f2a3/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
+golang.org/x/crypto v0.0.0-20210921155107-089bfa567519/go.mod h1:GvvjBRRGRdwPK5ydBHafDWAxML/pGHZbMvKqRZ5+Abc=
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 golang.org/x/net v0.0.0-20190620200207-3b0461eec859/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
-golang.org/x/net v0.0.0-20210805182204-aaa1db679c0d/go.mod h1:9nx3DQGgdP8bBQD5qxJ1jj9UTztislL4KSBs9R2vV5Y=
-golang.org/x/net v0.0.0-20211112202133-69e39bad7dc2/go.mod h1:9nx3DQGgdP8bBQD5qxJ1jj9UTztislL4KSBs9R2vV5Y=
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 golang.org/x/sync v0.0.0-20190423024810-112230192c58/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
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 golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
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 golang.org/x/sys v0.0.0-20201119102817-f84b799fce68/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
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 golang.org/x/sys v0.0.0-20210615035016-665e8c7367d1/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
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 golang.org/x/term v0.0.0-20201126162022-7de9c90e9dd1/go.mod h1:bj7SfCRtBDWHUb9snDiAeCFNEtKQo2Wmx5Cou7ajbmo=
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 golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
-golang.org/x/text v0.3.6/go.mod h1:5Zoc/QRtKVWzQhOtBMvqHzDpF6irO9z98xDceosuGiQ=
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 golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
 golang.org/x/tools v0.0.0-20191119224855-298f0cb1881e/go.mod h1:b+2E5dAYhXwXZwtnZ6UAqBI28+e2cm9otk0dWdXHAEo=
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+golang.org/x/tools v0.6.0/go.mod h1:Xwgl3UAJ/d3gWutnCtw505GrjyAbvKui8lOU390QaIU=
 golang.org/x/xerrors v0.0.0-20190717185122-a985d3407aa7/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
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 rsc.io/pdf v0.1.1/go.mod h1:n8OzWcQ6Sp37PL01nO98y4iUCRdTGarVfzxY20ICaU4=

curve25519/internal/field/fe_amd64.go

@@ -1,7 +1,6 @@
 // Code generated by command: go run fe_amd64_asm.go -out ../fe_amd64.s -stubs ../fe_amd64.go -pkg field. DO NOT EDIT.
 
 //go:build amd64 && gc && !purego
-// +build amd64,gc,!purego
 
 package field
 

curve25519/internal/field/fe_amd64.s

@@ -1,7 +1,6 @@
 // Code generated by command: go run fe_amd64_asm.go -out ../fe_amd64.s -stubs ../fe_amd64.go -pkg field. DO NOT EDIT.
 
 //go:build amd64 && gc && !purego
-// +build amd64,gc,!purego
 
 #include "textflag.h"
 

curve25519/internal/field/fe_amd64_noasm.go

@@ -3,7 +3,6 @@
 // license that can be found in the LICENSE file.
 
 //go:build !amd64 || !gc || purego
-// +build !amd64 !gc purego
 
 package field
 

curve25519/internal/field/fe_arm64.go

@@ -3,7 +3,6 @@
 // license that can be found in the LICENSE file.
 
 //go:build arm64 && gc && !purego
-// +build arm64,gc,!purego
 
 package field
 

curve25519/internal/field/fe_arm64.s

@@ -3,7 +3,6 @@
 // license that can be found in the LICENSE file.
 
 //go:build arm64 && gc && !purego
-// +build arm64,gc,!purego
 
 #include "textflag.h"
 

curve25519/internal/field/fe_arm64_noasm.go

@@ -3,7 +3,6 @@
 // license that can be found in the LICENSE file.
 
 //go:build !arm64 || !gc || purego
-// +build !arm64 !gc purego
 
 package field
 

go.mod

@@ -1,11 +1,11 @@
 module golang.org/x/crypto
 
-go 1.17
+go 1.18
 
 require (
-	golang.org/x/net v0.10.0 // tagx:ignore
-	golang.org/x/sys v0.13.0
-	golang.org/x/term v0.13.0
+	golang.org/x/net v0.21.0 // tagx:ignore
+	golang.org/x/sys v0.19.0
+	golang.org/x/term v0.19.0
 )
 
-require golang.org/x/text v0.13.0 // indirect
+require golang.org/x/text v0.14.0 // indirect

go.sum

@@ -1,41 +1,8 @@
-github.com/yuin/goldmark v1.4.13/go.mod h1:6yULJ656Px+3vBD8DxQVa3kxgyrAnzto9xy5taEt/CY=
-golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
-golang.org/x/crypto v0.0.0-20210921155107-089bfa567519/go.mod h1:GvvjBRRGRdwPK5ydBHafDWAxML/pGHZbMvKqRZ5+Abc=
-golang.org/x/mod v0.6.0-dev.0.20220419223038-86c51ed26bb4/go.mod h1:jJ57K6gSWd91VN4djpZkiMVwK6gcyfeH4XE8wZrZaV4=
-golang.org/x/mod v0.8.0/go.mod h1:iBbtSCu2XBx23ZKBPSOrRkjjQPZFPuis4dIYUhu/chs=
-golang.org/x/net v0.0.0-20190620200207-3b0461eec859/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
-golang.org/x/net v0.0.0-20210226172049-e18ecbb05110/go.mod h1:m0MpNAwzfU5UDzcl9v0D8zg8gWTRqZa9RBIspLL5mdg=
-golang.org/x/net v0.0.0-20220722155237-a158d28d115b/go.mod h1:XRhObCWvk6IyKnWLug+ECip1KBveYUHfp+8e9klMJ9c=
-golang.org/x/net v0.6.0/go.mod h1:2Tu9+aMcznHK/AK1HMvgo6xiTLG5rD5rZLDS+rp2Bjs=
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+golang.org/x/sys v0.19.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
+golang.org/x/term v0.19.0 h1:+ThwsDv+tYfnJFhF4L8jITxu1tdTWRTZpdsWgEgjL6Q=
+golang.org/x/term v0.19.0/go.mod h1:2CuTdWZ7KHSQwUzKva0cbMg6q2DMI3Mmxp+gKJbskEk=
+golang.org/x/text v0.14.0 h1:ScX5w1eTa3QqT8oi6+ziP7dTV1S2+ALU0bI+0zXKWiQ=
+golang.org/x/text v0.14.0/go.mod h1:18ZOQIKpY8NJVqYksKHtTdi31H5itFRjB5/qKTNYzSU=

hkdf/hkdf.go

@@ -56,7 +56,9 @@ func (f *hkdf) Read(p []byte) (int, error) {
 
 	// Fill the rest of the buffer
 	for len(p) > 0 {
-		f.expander.Reset()
+		if f.counter > 1 {
+			f.expander.Reset()
+		}
 		f.expander.Write(f.prev)
 		f.expander.Write(f.info)
 		f.expander.Write([]byte{f.counter})

internal/alias/alias.go

@@ -3,7 +3,6 @@
 // license that can be found in the LICENSE file.
 
 //go:build !purego
-// +build !purego
 
 // Package alias implements memory aliasing tests.
 package alias

internal/alias/alias_purego.go

@@ -3,7 +3,6 @@
 // license that can be found in the LICENSE file.
 
 //go:build purego
-// +build purego
 
 // Package alias implements memory aliasing tests.
 package alias

internal/poly1305/bits_compat.go

@@ -1,40 +0,0 @@
-// Copyright 2019 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-//go:build !go1.13
-// +build !go1.13
-
-package poly1305
-
-// Generic fallbacks for the math/bits intrinsics, copied from
-// src/math/bits/bits.go. They were added in Go 1.12, but Add64 and Sum64 had
-// variable time fallbacks until Go 1.13.
-
-func bitsAdd64(x, y, carry uint64) (sum, carryOut uint64) {
-	sum = x + y + carry
-	carryOut = ((x & y) | ((x | y) &^ sum)) >> 63
-	return
-}
-
-func bitsSub64(x, y, borrow uint64) (diff, borrowOut uint64) {
-	diff = x - y - borrow
-	borrowOut = ((^x & y) | (^(x ^ y) & diff)) >> 63
-	return
-}
-
-func bitsMul64(x, y uint64) (hi, lo uint64) {
-	const mask32 = 1<<32 - 1
-	x0 := x & mask32
-	x1 := x >> 32
-	y0 := y & mask32
-	y1 := y >> 32
-	w0 := x0 * y0
-	t := x1*y0 + w0>>32
-	w1 := t & mask32
-	w2 := t >> 32
-	w1 += x0 * y1
-	hi = x1*y1 + w2 + w1>>32
-	lo = x * y
-	return
-}

internal/poly1305/bits_go1.13.go

@@ -1,22 +0,0 @@
-// Copyright 2019 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-//go:build go1.13
-// +build go1.13
-
-package poly1305
-
-import "math/bits"
-
-func bitsAdd64(x, y, carry uint64) (sum, carryOut uint64) {
-	return bits.Add64(x, y, carry)
-}
-
-func bitsSub64(x, y, borrow uint64) (diff, borrowOut uint64) {
-	return bits.Sub64(x, y, borrow)
-}
-
-func bitsMul64(x, y uint64) (hi, lo uint64) {
-	return bits.Mul64(x, y)
-}

internal/poly1305/mac_noasm.go

@@ -3,7 +3,6 @@
 // license that can be found in the LICENSE file.
 
 //go:build (!amd64 && !ppc64le && !s390x) || !gc || purego
-// +build !amd64,!ppc64le,!s390x !gc purego
 
 package poly1305
 

internal/poly1305/sum_amd64.go

@@ -3,7 +3,6 @@
 // license that can be found in the LICENSE file.
 
 //go:build gc && !purego
-// +build gc,!purego
 
 package poly1305
 

internal/poly1305/sum_amd64.s

@@ -3,7 +3,6 @@
 // license that can be found in the LICENSE file.
 
 //go:build gc && !purego
-// +build gc,!purego
 
 #include "textflag.h"
 

internal/poly1305/sum_generic.go

@@ -7,7 +7,10 @@
 
 package poly1305
 
-import "encoding/binary"
+import (
+	"encoding/binary"
+	"math/bits"
+)
 
 // Poly1305 [RFC 7539] is a relatively simple algorithm: the authentication tag
 // for a 64 bytes message is approximately
@@ -114,13 +117,13 @@ type uint128 struct {
 }
 
 func mul64(a, b uint64) uint128 {
-	hi, lo := bitsMul64(a, b)
+	hi, lo := bits.Mul64(a, b)
 	return uint128{lo, hi}
 }
 
 func add128(a, b uint128) uint128 {
-	lo, c := bitsAdd64(a.lo, b.lo, 0)
-	hi, c := bitsAdd64(a.hi, b.hi, c)
+	lo, c := bits.Add64(a.lo, b.lo, 0)
+	hi, c := bits.Add64(a.hi, b.hi, c)
 	if c != 0 {
 		panic("poly1305: unexpected overflow")
 	}
@@ -155,8 +158,8 @@ func updateGeneric(state *macState, msg []byte) {
 		// hide leading zeroes. For full chunks, that's 1 << 128, so we can just
 		// add 1 to the most significant (2¹²⁸) limb, h2.
 		if len(msg) >= TagSize {
-			h0, c = bitsAdd64(h0, binary.LittleEndian.Uint64(msg[0:8]), 0)
-			h1, c = bitsAdd64(h1, binary.LittleEndian.Uint64(msg[8:16]), c)
+			h0, c = bits.Add64(h0, binary.LittleEndian.Uint64(msg[0:8]), 0)
+			h1, c = bits.Add64(h1, binary.LittleEndian.Uint64(msg[8:16]), c)
 			h2 += c + 1
 
 			msg = msg[TagSize:]
@@ -165,8 +168,8 @@ func updateGeneric(state *macState, msg []byte) {
 			copy(buf[:], msg)
 			buf[len(msg)] = 1
 
-			h0, c = bitsAdd64(h0, binary.LittleEndian.Uint64(buf[0:8]), 0)
-			h1, c = bitsAdd64(h1, binary.LittleEndian.Uint64(buf[8:16]), c)
+			h0, c = bits.Add64(h0, binary.LittleEndian.Uint64(buf[0:8]), 0)
+			h1, c = bits.Add64(h1, binary.LittleEndian.Uint64(buf[8:16]), c)
 			h2 += c
 
 			msg = nil
@@ -219,9 +222,9 @@ func updateGeneric(state *macState, msg []byte) {
 		m3 := h2r1
 
 		t0 := m0.lo
-		t1, c := bitsAdd64(m1.lo, m0.hi, 0)
-		t2, c := bitsAdd64(m2.lo, m1.hi, c)
-		t3, _ := bitsAdd64(m3.lo, m2.hi, c)
+		t1, c := bits.Add64(m1.lo, m0.hi, 0)
+		t2, c := bits.Add64(m2.lo, m1.hi, c)
+		t3, _ := bits.Add64(m3.lo, m2.hi, c)
 
 		// Now we have the result as 4 64-bit limbs, and we need to reduce it
 		// modulo 2¹³⁰ - 5. The special shape of this Crandall prime lets us do
@@ -243,14 +246,14 @@ func updateGeneric(state *macState, msg []byte) {
 
 		// To add c * 5 to h, we first add cc = c * 4, and then add (cc >> 2) = c.
 
-		h0, c = bitsAdd64(h0, cc.lo, 0)
-		h1, c = bitsAdd64(h1, cc.hi, c)
+		h0, c = bits.Add64(h0, cc.lo, 0)
+		h1, c = bits.Add64(h1, cc.hi, c)
 		h2 += c
 
 		cc = shiftRightBy2(cc)
 
-		h0, c = bitsAdd64(h0, cc.lo, 0)
-		h1, c = bitsAdd64(h1, cc.hi, c)
+		h0, c = bits.Add64(h0, cc.lo, 0)
+		h1, c = bits.Add64(h1, cc.hi, c)
 		h2 += c
 
 		// h2 is at most 3 + 1 + 1 = 5, making the whole of h at most
@@ -287,9 +290,9 @@ func finalize(out *[TagSize]byte, h *[3]uint64, s *[2]uint64) {
 	// in constant time, we compute t = h - (2¹³⁰ - 5), and select h as the
 	// result if the subtraction underflows, and t otherwise.
 
-	hMinusP0, b := bitsSub64(h0, p0, 0)
-	hMinusP1, b := bitsSub64(h1, p1, b)
-	_, b = bitsSub64(h2, p2, b)
+	hMinusP0, b := bits.Sub64(h0, p0, 0)
+	hMinusP1, b := bits.Sub64(h1, p1, b)
+	_, b = bits.Sub64(h2, p2, b)
 
 	// h = h if h < p else h - p
 	h0 = select64(b, h0, hMinusP0)
@@ -301,8 +304,8 @@ func finalize(out *[TagSize]byte, h *[3]uint64, s *[2]uint64) {
 	//
 	// by just doing a wide addition with the 128 low bits of h and discarding
 	// the overflow.
-	h0, c := bitsAdd64(h0, s[0], 0)
-	h1, _ = bitsAdd64(h1, s[1], c)
+	h0, c := bits.Add64(h0, s[0], 0)
+	h1, _ = bits.Add64(h1, s[1], c)
 
 	binary.LittleEndian.PutUint64(out[0:8], h0)
 	binary.LittleEndian.PutUint64(out[8:16], h1)

internal/poly1305/sum_ppc64le.go

@@ -3,7 +3,6 @@
 // license that can be found in the LICENSE file.
 
 //go:build gc && !purego
-// +build gc,!purego
 
 package poly1305
 

internal/poly1305/sum_ppc64le.s

@@ -3,7 +3,6 @@
 // license that can be found in the LICENSE file.
 
 //go:build gc && !purego
-// +build gc,!purego
 
 #include "textflag.h"
 
@@ -20,15 +19,14 @@
 
 #define POLY1305_MUL(h0, h1, h2, r0, r1, t0, t1, t2, t3, t4, t5) \
 	MULLD  r0, h0, t0;  \
-	MULLD  r0, h1, t4;  \
 	MULHDU r0, h0, t1;  \
+	MULLD  r0, h1, t4;  \
 	MULHDU r0, h1, t5;  \
 	ADDC   t4, t1, t1;  \
 	MULLD  r0, h2, t2;  \
-	ADDZE  t5;          \
 	MULHDU r1, h0, t4;  \
 	MULLD  r1, h0, h0;  \
-	ADD    t5, t2, t2;  \
+	ADDE   t5, t2, t2;  \
 	ADDC   h0, t1, t1;  \
 	MULLD  h2, r1, t3;  \
 	ADDZE  t4, h0;      \
@@ -38,13 +36,11 @@
 	ADDE   t5, t3, t3;  \
 	ADDC   h0, t2, t2;  \
 	MOVD   $-4, t4;     \
-	MOVD   t0, h0;      \
-	MOVD   t1, h1;      \
 	ADDZE  t3;          \
-	ANDCC  $3, t2, h2;  \
-	AND    t2, t4, t0;  \
+	RLDICL $0, t2, $62, h2; \
+	AND    t2, t4, h0;  \
 	ADDC   t0, h0, h0;  \
-	ADDE   t3, h1, h1;  \
+	ADDE   t3, t1, h1;  \
 	SLD    $62, t3, t4; \
 	SRD    $2, t2;      \
 	ADDZE  h2;          \
@@ -76,6 +72,7 @@ TEXT ·update(SB), $0-32
 loop:
 	POLY1305_ADD(R4, R8, R9, R10, R20, R21, R22)
 
+	PCALIGN $16
 multiply:
 	POLY1305_MUL(R8, R9, R10, R11, R12, R16, R17, R18, R14, R20, R21)
 	ADD $-16, R5

internal/poly1305/sum_s390x.go

@@ -3,7 +3,6 @@
 // license that can be found in the LICENSE file.
 
 //go:build gc && !purego
-// +build gc,!purego
 
 package poly1305
 

internal/poly1305/sum_s390x.s

@@ -3,7 +3,6 @@
 // license that can be found in the LICENSE file.
 
 //go:build gc && !purego
-// +build gc,!purego
 
 #include "textflag.h"
 

internal/testenv/exec.go

@@ -57,8 +57,8 @@ func CommandContext(t testing.TB, ctx context.Context, name string, args ...stri
 			// grace periods to clean up: one for the delay between the first
 			// termination signal being sent (via the Cancel callback when the Context
 			// expires) and the process being forcibly terminated (via the WaitDelay
-			// field), and a second one for the delay becween the process being
-			// terminated and and the test logging its output for debugging.
+			// field), and a second one for the delay between the process being
+			// terminated and the test logging its output for debugging.
 			//
 			// (We want to ensure that the test process itself has enough time to
 			// log the output before it is also terminated.)

internal/wycheproof/eddsa_test.go

@@ -3,7 +3,6 @@
 // license that can be found in the LICENSE file.
 
 //go:build go1.13
-// +build go1.13
 
 package wycheproof
 

md4/md4.go

@@ -4,7 +4,7 @@
 
 // Package md4 implements the MD4 hash algorithm as defined in RFC 1320.
 //
-// Deprecated: MD4 is cryptographically broken and should should only be used
+// Deprecated: MD4 is cryptographically broken and should only be used
 // where compatibility with legacy systems, not security, is the goal. Instead,
 // use a secure hash like SHA-256 (from crypto/sha256).
 package md4 // import "golang.org/x/crypto/md4"

ocsp/ocsp.go

@@ -279,21 +279,22 @@ func getOIDFromHashAlgorithm(target crypto.Hash) asn1.ObjectIdentifier {
 
 // This is the exposed reflection of the internal OCSP structures.
 
-// The status values that can be expressed in OCSP.  See RFC 6960.
+// The status values that can be expressed in OCSP. See RFC 6960.
+// These are used for the Response.Status field.
 const (
 	// Good means that the certificate is valid.
-	Good = iota
+	Good = 0
 	// Revoked means that the certificate has been deliberately revoked.
-	Revoked
+	Revoked = 1
 	// Unknown means that the OCSP responder doesn't know about the certificate.
-	Unknown
+	Unknown = 2
 	// ServerFailed is unused and was never used (see
 	// https://go-review.googlesource.com/#/c/18944). ParseResponse will
 	// return a ResponseError when an error response is parsed.
-	ServerFailed
+	ServerFailed = 3
 )
 
-// The enumerated reasons for revoking a certificate.  See RFC 5280.
+// The enumerated reasons for revoking a certificate. See RFC 5280.
 const (
 	Unspecified          = 0
 	KeyCompromise        = 1

ocsp/ocsp_test.go

@@ -3,7 +3,6 @@
 // license that can be found in the LICENSE file.
 
 //go:build go1.7
-// +build go1.7
 
 package ocsp
 

otr/libotr_test_helper.c

@@ -5,7 +5,7 @@
 // This code can be compiled and used to test the otr package against libotr.
 // See otr_test.go.
 
-// +build ignore
+//go:build ignore
 
 #include <stdio.h>
 #include <stdlib.h>

salsa20/salsa/salsa20_amd64.go

@@ -3,7 +3,6 @@
 // license that can be found in the LICENSE file.
 
 //go:build amd64 && !purego && gc
-// +build amd64,!purego,gc
 
 package salsa
 

salsa20/salsa/salsa20_amd64.s

@@ -3,7 +3,6 @@
 // license that can be found in the LICENSE file.
 
 //go:build amd64 && !purego && gc
-// +build amd64,!purego,gc
 
 // This code was translated into a form compatible with 6a from the public
 // domain sources in SUPERCOP: https://bench.cr.yp.to/supercop.html

salsa20/salsa/salsa20_amd64_test.go

@@ -3,7 +3,6 @@
 // license that can be found in the LICENSE file.
 
 //go:build amd64 && !purego && gc
-// +build amd64,!purego,gc
 
 package salsa
 

salsa20/salsa/salsa20_noasm.go

@@ -3,7 +3,6 @@
 // license that can be found in the LICENSE file.
 
 //go:build !amd64 || purego || !gc
-// +build !amd64 purego !gc
 
 package salsa
 

sha3/hashes_generic.go

@@ -3,7 +3,6 @@
 // license that can be found in the LICENSE file.
 
 //go:build !gc || purego || !s390x
-// +build !gc purego !s390x
 
 package sha3
 

sha3/keccakf.go

@@ -3,7 +3,6 @@
 // license that can be found in the LICENSE file.
 
 //go:build !amd64 || purego || !gc
-// +build !amd64 purego !gc
 
 package sha3
 

sha3/keccakf_amd64.go

@@ -3,7 +3,6 @@
 // license that can be found in the LICENSE file.
 
 //go:build amd64 && !purego && gc
-// +build amd64,!purego,gc
 
 package sha3
 

sha3/keccakf_amd64.s

@@ -3,7 +3,6 @@
 // license that can be found in the LICENSE file.
 
 //go:build amd64 && !purego && gc
-// +build amd64,!purego,gc
 
 // This code was translated into a form compatible with 6a from the public
 // domain sources at https://github.com/gvanas/KeccakCodePackage
@@ -320,9 +319,9 @@
 	MOVQ rDi, _si(oState); \
 	MOVQ rDo, _so(oState)  \
 
-// func keccakF1600(state *[25]uint64)
+// func keccakF1600(a *[25]uint64)
 TEXT ·keccakF1600(SB), 0, $200-8
-	MOVQ state+0(FP), rpState
+	MOVQ a+0(FP), rpState
 
 	// Convert the user state into an internal state
 	NOTQ _be(rpState)

sha3/register.go

@@ -3,7 +3,6 @@
 // license that can be found in the LICENSE file.
 
 //go:build go1.4
-// +build go1.4
 
 package sha3
 

sha3/sha3_s390x.go

@@ -3,7 +3,6 @@
 // license that can be found in the LICENSE file.
 
 //go:build gc && !purego
-// +build gc,!purego
 
 package sha3
 

sha3/sha3_s390x.s

@@ -3,7 +3,6 @@
 // license that can be found in the LICENSE file.
 
 //go:build gc && !purego
-// +build gc,!purego
 
 #include "textflag.h"
 

sha3/shake_generic.go

@@ -3,7 +3,6 @@
 // license that can be found in the LICENSE file.
 
 //go:build !gc || purego || !s390x
-// +build !gc purego !s390x
 
 package sha3
 

sha3/xor.go

@@ -3,7 +3,6 @@
 // license that can be found in the LICENSE file.
 
 //go:build (!amd64 && !386 && !ppc64le) || purego
-// +build !amd64,!386,!ppc64le purego
 
 package sha3
 

sha3/xor_unaligned.go

@@ -3,8 +3,6 @@
 // license that can be found in the LICENSE file.
 
 //go:build (amd64 || 386 || ppc64le) && !purego
-// +build amd64 386 ppc64le
-// +build !purego
 
 package sha3
 

ssh/agent/client.go

@@ -141,9 +141,14 @@ const (
 	agentAddSmartcardKeyConstrained = 26
 
 	// 3.7 Key constraint identifiers
-	agentConstrainLifetime  = 1
-	agentConstrainConfirm   = 2
-	agentConstrainExtension = 3
+	agentConstrainLifetime = 1
+	agentConstrainConfirm  = 2
+	// Constraint extension identifier up to version 2 of the protocol. A
+	// backward incompatible change will be required if we want to add support
+	// for SSH_AGENT_CONSTRAIN_MAXSIGN which uses the same ID.
+	agentConstrainExtensionV00 = 3
+	// Constraint extension identifier in version 3 and later of the protocol.
+	agentConstrainExtension = 255
 )
 
 // maxAgentResponseBytes is the maximum agent reply size that is accepted. This
@@ -205,7 +210,7 @@ type constrainLifetimeAgentMsg struct {
 }
 
 type constrainExtensionAgentMsg struct {
-	ExtensionName    string `sshtype:"3"`
+	ExtensionName    string `sshtype:"255|3"`
 	ExtensionDetails []byte
 
 	// Rest is a field used for parsing, not part of message

ssh/agent/client_test.go

@@ -164,15 +164,23 @@ func testAgentInterface(t *testing.T, agent ExtendedAgent, key interface{}, cert
 	data := []byte("hello")
 	sig, err := agent.Sign(pubKey, data)
 	if err != nil {
-		t.Fatalf("Sign(%s): %v", pubKey.Type(), err)
-	}
-
-	if err := pubKey.Verify(data, sig); err != nil {
-		t.Fatalf("Verify(%s): %v", pubKey.Type(), err)
+		t.Logf("sign failed with key type %q", pubKey.Type())
+		// In integration tests ssh-dss and ssh-rsa (SHA1 signatures) may be
+		// disabled for security reasons, we check SHA-2 variants later.
+		if pubKey.Type() != ssh.KeyAlgoDSA && pubKey.Type() != ssh.KeyAlgoRSA && pubKey.Type() != ssh.CertAlgoRSAv01 {
+			t.Fatalf("Sign(%s): %v", pubKey.Type(), err)
+		}
+	} else {
+		if err := pubKey.Verify(data, sig); err != nil {
+			t.Logf("verify failed with key type %q", pubKey.Type())
+			if pubKey.Type() != ssh.KeyAlgoRSA {
+				t.Fatalf("Verify(%s): %v", pubKey.Type(), err)
+			}
+		}
 	}
 
 	// For tests on RSA keys, try signing with SHA-256 and SHA-512 flags
-	if pubKey.Type() == "ssh-rsa" {
+	if pubKey.Type() == ssh.KeyAlgoRSA {
 		sshFlagTest := func(flag SignatureFlags, expectedSigFormat string) {
 			sig, err = agent.SignWithFlags(pubKey, data, flag)
 			if err != nil {
@@ -185,7 +193,6 @@ func testAgentInterface(t *testing.T, agent ExtendedAgent, key interface{}, cert
 				t.Fatalf("Verify(%s): %v", pubKey.Type(), err)
 			}
 		}
-		sshFlagTest(0, ssh.KeyAlgoRSA)
 		sshFlagTest(SignatureFlagRsaSha256, ssh.KeyAlgoRSASHA256)
 		sshFlagTest(SignatureFlagRsaSha512, ssh.KeyAlgoRSASHA512)
 	}

ssh/agent/server.go

@@ -208,7 +208,7 @@ func parseConstraints(constraints []byte) (lifetimeSecs uint32, confirmBeforeUse
 		case agentConstrainConfirm:
 			confirmBeforeUse = true
 			constraints = constraints[1:]
-		case agentConstrainExtension:
+		case agentConstrainExtension, agentConstrainExtensionV00:
 			var msg constrainExtensionAgentMsg
 			if err = ssh.Unmarshal(constraints, &msg); err != nil {
 				return 0, false, nil, err

ssh/agent/server_test.go

@@ -243,7 +243,11 @@ func TestParseConstraints(t *testing.T) {
 			ExtensionDetails: []byte(fmt.Sprintf("details: %d", i)),
 		}
 		expect = append(expect, ext)
-		data = append(data, agentConstrainExtension)
+		if i%2 == 0 {
+			data = append(data, agentConstrainExtension)
+		} else {
+			data = append(data, agentConstrainExtensionV00)
+		}
 		data = append(data, ssh.Marshal(ext)...)
 	}
 	_, _, extensions, err := parseConstraints(data)

ssh/certs_test.go

@@ -367,21 +367,21 @@ func TestCertTypes(t *testing.T) {
 
 func TestCertSignWithMultiAlgorithmSigner(t *testing.T) {
 	type testcase struct {
-		sigAlgo   string
-		algoritms []string
+		sigAlgo    string
+		algorithms []string
 	}
 	cases := []testcase{
 		{
-			sigAlgo:   KeyAlgoRSA,
-			algoritms: []string{KeyAlgoRSA, KeyAlgoRSASHA512},
+			sigAlgo:    KeyAlgoRSA,
+			algorithms: []string{KeyAlgoRSA, KeyAlgoRSASHA512},
 		},
 		{
-			sigAlgo:   KeyAlgoRSASHA256,
-			algoritms: []string{KeyAlgoRSASHA256, KeyAlgoRSA, KeyAlgoRSASHA512},
+			sigAlgo:    KeyAlgoRSASHA256,
+			algorithms: []string{KeyAlgoRSASHA256, KeyAlgoRSA, KeyAlgoRSASHA512},
 		},
 		{
-			sigAlgo:   KeyAlgoRSASHA512,
-			algoritms: []string{KeyAlgoRSASHA512, KeyAlgoRSASHA256},
+			sigAlgo:    KeyAlgoRSASHA512,
+			algorithms: []string{KeyAlgoRSASHA512, KeyAlgoRSASHA256},
 		},
 	}
 
@@ -393,7 +393,7 @@ func TestCertSignWithMultiAlgorithmSigner(t *testing.T) {
 
 	for _, c := range cases {
 		t.Run(c.sigAlgo, func(t *testing.T) {
-			signer, err := NewSignerWithAlgorithms(testSigners["rsa"].(AlgorithmSigner), c.algoritms)
+			signer, err := NewSignerWithAlgorithms(testSigners["rsa"].(AlgorithmSigner), c.algorithms)
 			if err != nil {
 				t.Fatalf("NewSignerWithAlgorithms error: %v", err)
 			}

ssh/channel.go

@@ -187,9 +187,11 @@ type channel struct {
 	pending    *buffer
 	extPending *buffer
 
-	// windowMu protects myWindow, the flow-control window.
-	windowMu sync.Mutex
-	myWindow uint32
+	// windowMu protects myWindow, the flow-control window, and myConsumed,
+	// the number of bytes consumed since we last increased myWindow
+	windowMu   sync.Mutex
+	myWindow   uint32
+	myConsumed uint32
 
 	// writeMu serializes calls to mux.conn.writePacket() and
 	// protects sentClose and packetPool. This mutex must be
@@ -332,14 +334,24 @@ func (ch *channel) handleData(packet []byte) error {
 	return nil
 }
 
-func (c *channel) adjustWindow(n uint32) error {
+func (c *channel) adjustWindow(adj uint32) error {
 	c.windowMu.Lock()
-	// Since myWindow is managed on our side, and can never exceed
-	// the initial window setting, we don't worry about overflow.
-	c.myWindow += uint32(n)
+	// Since myConsumed and myWindow are managed on our side, and can never
+	// exceed the initial window setting, we don't worry about overflow.
+	c.myConsumed += adj
+	var sendAdj uint32
+	if (channelWindowSize-c.myWindow > 3*c.maxIncomingPayload) ||
+		(c.myWindow < channelWindowSize/2) {
+		sendAdj = c.myConsumed
+		c.myConsumed = 0
+		c.myWindow += sendAdj
+	}
 	c.windowMu.Unlock()
+	if sendAdj == 0 {
+		return nil
+	}
 	return c.sendMessage(windowAdjustMsg{
-		AdditionalBytes: uint32(n),
+		AdditionalBytes: sendAdj,
 	})
 }
 

ssh/client.go

@@ -82,7 +82,7 @@ func NewClientConn(c net.Conn, addr string, config *ClientConfig) (Conn, <-chan
 
 	if err := conn.clientHandshake(addr, &fullConf); err != nil {
 		c.Close()
-		return nil, nil, nil, fmt.Errorf("ssh: handshake failed: %v", err)
+		return nil, nil, nil, fmt.Errorf("ssh: handshake failed: %w", err)
 	}
 	conn.mux = newMux(conn.transport)
 	return conn, conn.mux.incomingChannels, conn.mux.incomingRequests, nil

ssh/client_auth.go

@@ -307,7 +307,10 @@ func (cb publicKeyCallback) auth(session []byte, user string, c packetConn, rand
 	}
 	var methods []string
 	var errSigAlgo error
-	for _, signer := range signers {
+
+	origSignersLen := len(signers)
+	for idx := 0; idx < len(signers); idx++ {
+		signer := signers[idx]
 		pub := signer.PublicKey()
 		as, algo, err := pickSignatureAlgorithm(signer, extensions)
 		if err != nil && errSigAlgo == nil {
@@ -321,6 +324,21 @@ func (cb publicKeyCallback) auth(session []byte, user string, c packetConn, rand
 		if err != nil {
 			return authFailure, nil, err
 		}
+		// OpenSSH 7.2-7.7 advertises support for rsa-sha2-256 and rsa-sha2-512
+		// in the "server-sig-algs" extension but doesn't support these
+		// algorithms for certificate authentication, so if the server rejects
+		// the key try to use the obtained algorithm as if "server-sig-algs" had
+		// not been implemented if supported from the algorithm signer.
+		if !ok && idx < origSignersLen && isRSACert(algo) && algo != CertAlgoRSAv01 {
+			if contains(as.Algorithms(), KeyAlgoRSA) {
+				// We retry using the compat algorithm after all signers have
+				// been tried normally.
+				signers = append(signers, &multiAlgorithmSigner{
+					AlgorithmSigner:     as,
+					supportedAlgorithms: []string{KeyAlgoRSA},
+				})
+			}
+		}
 		if !ok {
 			continue
 		}

ssh/client_test.go

@@ -7,6 +7,9 @@ package ssh
 import (
 	"bytes"
 	"crypto/rand"
+	"errors"
+	"fmt"
+	"net"
 	"strings"
 	"testing"
 )
@@ -207,9 +210,12 @@ func TestBannerCallback(t *testing.T) {
 }
 
 func TestNewClientConn(t *testing.T) {
+	errHostKeyMismatch := errors.New("host key mismatch")
+
 	for _, tt := range []struct {
-		name string
-		user string
+		name                    string
+		user                    string
+		simulateHostKeyMismatch HostKeyCallback
 	}{
 		{
 			name: "good user field for ConnMetadata",
@@ -219,6 +225,13 @@ func TestNewClientConn(t *testing.T) {
 			name: "empty user field for ConnMetadata",
 			user: "",
 		},
+		{
+			name: "host key mismatch",
+			user: "testuser",
+			simulateHostKeyMismatch: func(hostname string, remote net.Addr, key PublicKey) error {
+				return fmt.Errorf("%w: %s", errHostKeyMismatch, bytes.TrimSpace(MarshalAuthorizedKey(key)))
+			},
+		},
 	} {
 		t.Run(tt.name, func(t *testing.T) {
 			c1, c2, err := netPipe()
@@ -243,8 +256,16 @@ func TestNewClientConn(t *testing.T) {
 				},
 				HostKeyCallback: InsecureIgnoreHostKey(),
 			}
+
+			if tt.simulateHostKeyMismatch != nil {
+				clientConf.HostKeyCallback = tt.simulateHostKeyMismatch
+			}
+
 			clientConn, _, _, err := NewClientConn(c2, "", clientConf)
 			if err != nil {
+				if tt.simulateHostKeyMismatch != nil && errors.Is(err, errHostKeyMismatch) {
+					return
+				}
 				t.Fatal(err)
 			}
 

ssh/common.go

@@ -10,7 +10,6 @@ import (
 	"fmt"
 	"io"
 	"math"
-	"strings"
 	"sync"
 
 	_ "crypto/sha1"
@@ -128,6 +127,14 @@ func isRSA(algo string) bool {
 	return contains(algos, underlyingAlgo(algo))
 }
 
+func isRSACert(algo string) bool {
+	_, ok := certKeyAlgoNames[algo]
+	if !ok {
+		return false
+	}
+	return isRSA(algo)
+}
+
 // supportedPubKeyAuthAlgos specifies the supported client public key
 // authentication algorithms. Note that this doesn't include certificate types
 // since those use the underlying algorithm. This list is sent to the client if
@@ -140,8 +147,6 @@ var supportedPubKeyAuthAlgos = []string{
 	KeyAlgoDSA,
 }
 
-var supportedPubKeyAuthAlgosList = strings.Join(supportedPubKeyAuthAlgos, ",")
-
 // unexpectedMessageError results when the SSH message that we received didn't
 // match what we wanted.
 func unexpectedMessageError(expected, got uint8) error {

ssh/example_test.go

@@ -16,6 +16,7 @@ import (
 	"os"
 	"path/filepath"
 	"strings"
+	"sync"
 
 	"golang.org/x/crypto/ssh"
 	"golang.org/x/crypto/ssh/terminal"
@@ -98,8 +99,15 @@ func ExampleNewServerConn() {
 	}
 	log.Printf("logged in with key %s", conn.Permissions.Extensions["pubkey-fp"])
 
+	var wg sync.WaitGroup
+	defer wg.Wait()
+
 	// The incoming Request channel must be serviced.
-	go ssh.DiscardRequests(reqs)
+	wg.Add(1)
+	go func() {
+		ssh.DiscardRequests(reqs)
+		wg.Done()
+	}()
 
 	// Service the incoming Channel channel.
 	for newChannel := range chans {
@@ -119,16 +127,22 @@ func ExampleNewServerConn() {
 		// Sessions have out-of-band requests such as "shell",
 		// "pty-req" and "env".  Here we handle only the
 		// "shell" request.
+		wg.Add(1)
 		go func(in <-chan *ssh.Request) {
 			for req := range in {
 				req.Reply(req.Type == "shell", nil)
 			}
+			wg.Done()
 		}(requests)
 
 		term := terminal.NewTerminal(channel, "> ")
 
+		wg.Add(1)
 		go func() {
-			defer channel.Close()
+			defer func() {
+				channel.Close()
+				wg.Done()
+			}()
 			for {
 				line, err := term.ReadLine()
 				if err != nil {
@@ -370,7 +384,7 @@ func ExampleCertificate_SignCert() {
 	}
 	mas, err := ssh.NewSignerWithAlgorithms(signer.(ssh.AlgorithmSigner), []string{ssh.KeyAlgoRSASHA256})
 	if err != nil {
-		log.Fatal("unable to create signer with algoritms: ", err)
+		log.Fatal("unable to create signer with algorithms: ", err)
 	}
 	certificate := ssh.Certificate{
 		Key:      publicKey,

ssh/handshake.go

@@ -11,6 +11,7 @@ import (
 	"io"
 	"log"
 	"net"
+	"strings"
 	"sync"
 )
 
@@ -34,6 +35,16 @@ type keyingTransport interface {
 	// direction will be effected if a msgNewKeys message is sent
 	// or received.
 	prepareKeyChange(*algorithms, *kexResult) error
+
+	// setStrictMode sets the strict KEX mode, notably triggering
+	// sequence number resets on sending or receiving msgNewKeys.
+	// If the sequence number is already > 1 when setStrictMode
+	// is called, an error is returned.
+	setStrictMode() error
+
+	// setInitialKEXDone indicates to the transport that the initial key exchange
+	// was completed
+	setInitialKEXDone()
 }
 
 // handshakeTransport implements rekeying on top of a keyingTransport
@@ -50,6 +61,10 @@ type handshakeTransport struct {
 	// connection.
 	hostKeys []Signer
 
+	// publicKeyAuthAlgorithms is non-empty if we are the server. In that case,
+	// it contains the supported client public key authentication algorithms.
+	publicKeyAuthAlgorithms []string
+
 	// hostKeyAlgorithms is non-empty if we are the client. In that case,
 	// we accept these key types from the server as host key.
 	hostKeyAlgorithms []string
@@ -95,6 +110,10 @@ type handshakeTransport struct {
 
 	// The session ID or nil if first kex did not complete yet.
 	sessionID []byte
+
+	// strictMode indicates if the other side of the handshake indicated
+	// that we should be following the strict KEX protocol restrictions.
+	strictMode bool
 }
 
 type pendingKex struct {
@@ -141,6 +160,7 @@ func newClientTransport(conn keyingTransport, clientVersion, serverVersion []byt
 func newServerTransport(conn keyingTransport, clientVersion, serverVersion []byte, config *ServerConfig) *handshakeTransport {
 	t := newHandshakeTransport(conn, &config.Config, clientVersion, serverVersion)
 	t.hostKeys = config.hostKeys
+	t.publicKeyAuthAlgorithms = config.PublicKeyAuthAlgorithms
 	go t.readLoop()
 	go t.kexLoop()
 	return t
@@ -203,7 +223,10 @@ func (t *handshakeTransport) readLoop() {
 			close(t.incoming)
 			break
 		}
-		if p[0] == msgIgnore || p[0] == msgDebug {
+		// If this is the first kex, and strict KEX mode is enabled,
+		// we don't ignore any messages, as they may be used to manipulate
+		// the packet sequence numbers.
+		if !(t.sessionID == nil && t.strictMode) && (p[0] == msgIgnore || p[0] == msgDebug) {
 			continue
 		}
 		t.incoming <- p
@@ -435,6 +458,11 @@ func (t *handshakeTransport) readOnePacket(first bool) ([]byte, error) {
 	return successPacket, nil
 }
 
+const (
+	kexStrictClient = "kex-strict-c-v00@openssh.com"
+	kexStrictServer = "kex-strict-s-v00@openssh.com"
+)
+
 // sendKexInit sends a key change message.
 func (t *handshakeTransport) sendKexInit() error {
 	t.mu.Lock()
@@ -448,7 +476,6 @@ func (t *handshakeTransport) sendKexInit() error {
 	}
 
 	msg := &kexInitMsg{
-		KexAlgos:                t.config.KeyExchanges,
 		CiphersClientServer:     t.config.Ciphers,
 		CiphersServerClient:     t.config.Ciphers,
 		MACsClientServer:        t.config.MACs,
@@ -458,6 +485,13 @@ func (t *handshakeTransport) sendKexInit() error {
 	}
 	io.ReadFull(rand.Reader, msg.Cookie[:])
 
+	// We mutate the KexAlgos slice, in order to add the kex-strict extension algorithm,
+	// and possibly to add the ext-info extension algorithm. Since the slice may be the
+	// user owned KeyExchanges, we create our own slice in order to avoid using user
+	// owned memory by mistake.
+	msg.KexAlgos = make([]string, 0, len(t.config.KeyExchanges)+2) // room for kex-strict and ext-info
+	msg.KexAlgos = append(msg.KexAlgos, t.config.KeyExchanges...)
+
 	isServer := len(t.hostKeys) > 0
 	if isServer {
 		for _, k := range t.hostKeys {
@@ -482,17 +516,24 @@ func (t *handshakeTransport) sendKexInit() error {
 				msg.ServerHostKeyAlgos = append(msg.ServerHostKeyAlgos, keyFormat)
 			}
 		}
+
+		if t.sessionID == nil {
+			msg.KexAlgos = append(msg.KexAlgos, kexStrictServer)
+		}
 	} else {
 		msg.ServerHostKeyAlgos = t.hostKeyAlgorithms
 
 		// As a client we opt in to receiving SSH_MSG_EXT_INFO so we know what
 		// algorithms the server supports for public key authentication. See RFC
 		// 8308, Section 2.1.
+		//
+		// We also send the strict KEX mode extension algorithm, in order to opt
+		// into the strict KEX mode.
 		if firstKeyExchange := t.sessionID == nil; firstKeyExchange {
-			msg.KexAlgos = make([]string, 0, len(t.config.KeyExchanges)+1)
-			msg.KexAlgos = append(msg.KexAlgos, t.config.KeyExchanges...)
 			msg.KexAlgos = append(msg.KexAlgos, "ext-info-c")
+			msg.KexAlgos = append(msg.KexAlgos, kexStrictClient)
 		}
+
 	}
 
 	packet := Marshal(msg)
@@ -598,6 +639,13 @@ func (t *handshakeTransport) enterKeyExchange(otherInitPacket []byte) error {
 		return err
 	}
 
+	if t.sessionID == nil && ((isClient && contains(serverInit.KexAlgos, kexStrictServer)) || (!isClient && contains(clientInit.KexAlgos, kexStrictClient))) {
+		t.strictMode = true
+		if err := t.conn.setStrictMode(); err != nil {
+			return err
+		}
+	}
+
 	// We don't send FirstKexFollows, but we handle receiving it.
 	//
 	// RFC 4253 section 7 defines the kex and the agreement method for
@@ -649,6 +697,7 @@ func (t *handshakeTransport) enterKeyExchange(otherInitPacket []byte) error {
 	// message with the server-sig-algs extension if the client supports it. See
 	// RFC 8308, Sections 2.4 and 3.1, and [PROTOCOL], Section 1.9.
 	if !isClient && firstKeyExchange && contains(clientInit.KexAlgos, "ext-info-c") {
+		supportedPubKeyAuthAlgosList := strings.Join(t.publicKeyAuthAlgorithms, ",")
 		extInfo := &extInfoMsg{
 			NumExtensions: 2,
 			Payload:       make([]byte, 0, 4+15+4+len(supportedPubKeyAuthAlgosList)+4+16+4+1),
@@ -672,6 +721,12 @@ func (t *handshakeTransport) enterKeyExchange(otherInitPacket []byte) error {
 		return unexpectedMessageError(msgNewKeys, packet[0])
 	}
 
+	if firstKeyExchange {
+		// Indicates to the transport that the first key exchange is completed
+		// after receiving SSH_MSG_NEWKEYS.
+		t.conn.setInitialKEXDone()
+	}
+
 	return nil
 }
 

ssh/handshake_test.go

@@ -395,6 +395,10 @@ func (n *errorKeyingTransport) readPacket() ([]byte, error) {
 	return n.packetConn.readPacket()
 }
 
+func (n *errorKeyingTransport) setStrictMode() error { return nil }
+
+func (n *errorKeyingTransport) setInitialKEXDone() {}
+
 func TestHandshakeErrorHandlingRead(t *testing.T) {
 	for i := 0; i < 20; i++ {
 		testHandshakeErrorHandlingN(t, i, -1, false)
@@ -710,3 +714,308 @@ func TestPickIncompatibleHostKeyAlgo(t *testing.T) {
 		t.Fatal("incompatible signer returned")
 	}
 }
+
+func TestStrictKEXResetSeqFirstKEX(t *testing.T) {
+	if runtime.GOOS == "plan9" {
+		t.Skip("see golang.org/issue/7237")
+	}
+
+	checker := &syncChecker{
+		waitCall: make(chan int, 10),
+		called:   make(chan int, 10),
+	}
+
+	checker.waitCall <- 1
+	trC, trS, err := handshakePair(&ClientConfig{HostKeyCallback: checker.Check}, "addr", false)
+	if err != nil {
+		t.Fatalf("handshakePair: %v", err)
+	}
+	<-checker.called
+
+	t.Cleanup(func() {
+		trC.Close()
+		trS.Close()
+	})
+
+	// Throw away the msgExtInfo packet sent during the handshake by the server
+	_, err = trC.readPacket()
+	if err != nil {
+		t.Fatalf("readPacket failed: %s", err)
+	}
+
+	// close the handshake transports before checking the sequence number to
+	// avoid races.
+	trC.Close()
+	trS.Close()
+
+	// check that the sequence number counters. We reset after msgNewKeys, but
+	// then the server immediately writes msgExtInfo, and we close the
+	// transports so we expect read 2, write 0 on the client and read 1, write 1
+	// on the server.
+	if trC.conn.(*transport).reader.seqNum != 2 || trC.conn.(*transport).writer.seqNum != 0 ||
+		trS.conn.(*transport).reader.seqNum != 1 || trS.conn.(*transport).writer.seqNum != 1 {
+		t.Errorf(
+			"unexpected sequence counters:\nclient: reader %d (expected 2), writer %d (expected 0)\nserver: reader %d (expected 1), writer %d (expected 1)",
+			trC.conn.(*transport).reader.seqNum,
+			trC.conn.(*transport).writer.seqNum,
+			trS.conn.(*transport).reader.seqNum,
+			trS.conn.(*transport).writer.seqNum,
+		)
+	}
+}
+
+func TestStrictKEXResetSeqSuccessiveKEX(t *testing.T) {
+	if runtime.GOOS == "plan9" {
+		t.Skip("see golang.org/issue/7237")
+	}
+
+	checker := &syncChecker{
+		waitCall: make(chan int, 10),
+		called:   make(chan int, 10),
+	}
+
+	checker.waitCall <- 1
+	trC, trS, err := handshakePair(&ClientConfig{HostKeyCallback: checker.Check}, "addr", false)
+	if err != nil {
+		t.Fatalf("handshakePair: %v", err)
+	}
+	<-checker.called
+
+	t.Cleanup(func() {
+		trC.Close()
+		trS.Close()
+	})
+
+	// Throw away the msgExtInfo packet sent during the handshake by the server
+	_, err = trC.readPacket()
+	if err != nil {
+		t.Fatalf("readPacket failed: %s", err)
+	}
+
+	// write and read five packets on either side to bump the sequence numbers
+	for i := 0; i < 5; i++ {
+		if err := trC.writePacket([]byte{msgRequestSuccess}); err != nil {
+			t.Fatalf("writePacket failed: %s", err)
+		}
+		if _, err := trS.readPacket(); err != nil {
+			t.Fatalf("readPacket failed: %s", err)
+		}
+		if err := trS.writePacket([]byte{msgRequestSuccess}); err != nil {
+			t.Fatalf("writePacket failed: %s", err)
+		}
+		if _, err := trC.readPacket(); err != nil {
+			t.Fatalf("readPacket failed: %s", err)
+		}
+	}
+
+	// Request a key exchange, which should cause the sequence numbers to reset
+	checker.waitCall <- 1
+	trC.requestKeyExchange()
+	<-checker.called
+
+	// write a packet on the client, and then read it, to verify the key change has actually happened, since
+	// the HostKeyCallback is called _during_ the handshake, so isn't actually indicative of the handshake
+	// finishing.
+	dummyPacket := []byte{99}
+	if err := trS.writePacket(dummyPacket); err != nil {
+		t.Fatalf("writePacket failed: %s", err)
+	}
+	if p, err := trC.readPacket(); err != nil {
+		t.Fatalf("readPacket failed: %s", err)
+	} else if !bytes.Equal(p, dummyPacket) {
+		t.Fatalf("unexpected packet: got %x, want %x", p, dummyPacket)
+	}
+
+	// close the handshake transports before checking the sequence number to
+	// avoid races.
+	trC.Close()
+	trS.Close()
+
+	if trC.conn.(*transport).reader.seqNum != 2 || trC.conn.(*transport).writer.seqNum != 0 ||
+		trS.conn.(*transport).reader.seqNum != 1 || trS.conn.(*transport).writer.seqNum != 1 {
+		t.Errorf(
+			"unexpected sequence counters:\nclient: reader %d (expected 2), writer %d (expected 0)\nserver: reader %d (expected 1), writer %d (expected 1)",
+			trC.conn.(*transport).reader.seqNum,
+			trC.conn.(*transport).writer.seqNum,
+			trS.conn.(*transport).reader.seqNum,
+			trS.conn.(*transport).writer.seqNum,
+		)
+	}
+}
+
+func TestSeqNumIncrease(t *testing.T) {
+	if runtime.GOOS == "plan9" {
+		t.Skip("see golang.org/issue/7237")
+	}
+
+	checker := &syncChecker{
+		waitCall: make(chan int, 10),
+		called:   make(chan int, 10),
+	}
+
+	checker.waitCall <- 1
+	trC, trS, err := handshakePair(&ClientConfig{HostKeyCallback: checker.Check}, "addr", false)
+	if err != nil {
+		t.Fatalf("handshakePair: %v", err)
+	}
+	<-checker.called
+
+	t.Cleanup(func() {
+		trC.Close()
+		trS.Close()
+	})
+
+	// Throw away the msgExtInfo packet sent during the handshake by the server
+	_, err = trC.readPacket()
+	if err != nil {
+		t.Fatalf("readPacket failed: %s", err)
+	}
+
+	// write and read five packets on either side to bump the sequence numbers
+	for i := 0; i < 5; i++ {
+		if err := trC.writePacket([]byte{msgRequestSuccess}); err != nil {
+			t.Fatalf("writePacket failed: %s", err)
+		}
+		if _, err := trS.readPacket(); err != nil {
+			t.Fatalf("readPacket failed: %s", err)
+		}
+		if err := trS.writePacket([]byte{msgRequestSuccess}); err != nil {
+			t.Fatalf("writePacket failed: %s", err)
+		}
+		if _, err := trC.readPacket(); err != nil {
+			t.Fatalf("readPacket failed: %s", err)
+		}
+	}
+
+	// close the handshake transports before checking the sequence number to
+	// avoid races.
+	trC.Close()
+	trS.Close()
+
+	if trC.conn.(*transport).reader.seqNum != 7 || trC.conn.(*transport).writer.seqNum != 5 ||
+		trS.conn.(*transport).reader.seqNum != 6 || trS.conn.(*transport).writer.seqNum != 6 {
+		t.Errorf(
+			"unexpected sequence counters:\nclient: reader %d (expected 7), writer %d (expected 5)\nserver: reader %d (expected 6), writer %d (expected 6)",
+			trC.conn.(*transport).reader.seqNum,
+			trC.conn.(*transport).writer.seqNum,
+			trS.conn.(*transport).reader.seqNum,
+			trS.conn.(*transport).writer.seqNum,
+		)
+	}
+}
+
+func TestStrictKEXUnexpectedMsg(t *testing.T) {
+	if runtime.GOOS == "plan9" {
+		t.Skip("see golang.org/issue/7237")
+	}
+
+	// Check that unexpected messages during the handshake cause failure
+	_, _, err := handshakePair(&ClientConfig{HostKeyCallback: func(hostname string, remote net.Addr, key PublicKey) error { return nil }}, "addr", true)
+	if err == nil {
+		t.Fatal("handshake should fail when there are unexpected messages during the handshake")
+	}
+
+	trC, trS, err := handshakePair(&ClientConfig{HostKeyCallback: func(hostname string, remote net.Addr, key PublicKey) error { return nil }}, "addr", false)
+	if err != nil {
+		t.Fatalf("handshake failed: %s", err)
+	}
+
+	// Check that ignore/debug pacekts are still ignored outside of the handshake
+	if err := trC.writePacket([]byte{msgIgnore}); err != nil {
+		t.Fatalf("writePacket failed: %s", err)
+	}
+	if err := trC.writePacket([]byte{msgDebug}); err != nil {
+		t.Fatalf("writePacket failed: %s", err)
+	}
+	dummyPacket := []byte{99}
+	if err := trC.writePacket(dummyPacket); err != nil {
+		t.Fatalf("writePacket failed: %s", err)
+	}
+
+	if p, err := trS.readPacket(); err != nil {
+		t.Fatalf("readPacket failed: %s", err)
+	} else if !bytes.Equal(p, dummyPacket) {
+		t.Fatalf("unexpected packet: got %x, want %x", p, dummyPacket)
+	}
+}
+
+func TestStrictKEXMixed(t *testing.T) {
+	// Test that we still support a mixed connection, where one side sends kex-strict but the other
+	// side doesn't.
+
+	a, b, err := netPipe()
+	if err != nil {
+		t.Fatalf("netPipe failed: %s", err)
+	}
+
+	var trC, trS keyingTransport
+
+	trC = newTransport(a, rand.Reader, true)
+	trS = newTransport(b, rand.Reader, false)
+	trS = addNoiseTransport(trS)
+
+	clientConf := &ClientConfig{HostKeyCallback: func(hostname string, remote net.Addr, key PublicKey) error { return nil }}
+	clientConf.SetDefaults()
+
+	v := []byte("version")
+	client := newClientTransport(trC, v, v, clientConf, "addr", a.RemoteAddr())
+
+	serverConf := &ServerConfig{}
+	serverConf.AddHostKey(testSigners["ecdsa"])
+	serverConf.AddHostKey(testSigners["rsa"])
+	serverConf.SetDefaults()
+
+	transport := newHandshakeTransport(trS, &serverConf.Config, []byte("version"), []byte("version"))
+	transport.hostKeys = serverConf.hostKeys
+	transport.publicKeyAuthAlgorithms = serverConf.PublicKeyAuthAlgorithms
+
+	readOneFailure := make(chan error, 1)
+	go func() {
+		if _, err := transport.readOnePacket(true); err != nil {
+			readOneFailure <- err
+		}
+	}()
+
+	// Basically sendKexInit, but without the kex-strict extension algorithm
+	msg := &kexInitMsg{
+		KexAlgos:                transport.config.KeyExchanges,
+		CiphersClientServer:     transport.config.Ciphers,
+		CiphersServerClient:     transport.config.Ciphers,
+		MACsClientServer:        transport.config.MACs,
+		MACsServerClient:        transport.config.MACs,
+		CompressionClientServer: supportedCompressions,
+		CompressionServerClient: supportedCompressions,
+		ServerHostKeyAlgos:      []string{KeyAlgoRSASHA256, KeyAlgoRSASHA512, KeyAlgoRSA},
+	}
+	packet := Marshal(msg)
+	// writePacket destroys the contents, so save a copy.
+	packetCopy := make([]byte, len(packet))
+	copy(packetCopy, packet)
+	if err := transport.pushPacket(packetCopy); err != nil {
+		t.Fatalf("pushPacket: %s", err)
+	}
+	transport.sentInitMsg = msg
+	transport.sentInitPacket = packet
+
+	if err := transport.getWriteError(); err != nil {
+		t.Fatalf("getWriteError failed: %s", err)
+	}
+	var request *pendingKex
+	select {
+	case err = <-readOneFailure:
+		t.Fatalf("server readOnePacket failed: %s", err)
+	case request = <-transport.startKex:
+		break
+	}
+
+	// We expect the following calls to fail if the side which does not support
+	// kex-strict sends unexpected/ignored packets during the handshake, even if
+	// the other side does support kex-strict.
+
+	if err := transport.enterKeyExchange(request.otherInit); err != nil {
+		t.Fatalf("enterKeyExchange failed: %s", err)
+	}
+	if err := client.waitSession(); err != nil {
+		t.Fatalf("client.waitSession: %v", err)
+	}
+}

ssh/keys.go

@@ -1232,16 +1232,27 @@ func ParseRawPrivateKeyWithPassphrase(pemBytes, passphrase []byte) (interface{},
 		return nil, fmt.Errorf("ssh: cannot decode encrypted private keys: %v", err)
 	}
 
+	var result interface{}
+
 	switch block.Type {
 	case "RSA PRIVATE KEY":
-		return x509.ParsePKCS1PrivateKey(buf)
+		result, err = x509.ParsePKCS1PrivateKey(buf)
 	case "EC PRIVATE KEY":
-		return x509.ParseECPrivateKey(buf)
+		result, err = x509.ParseECPrivateKey(buf)
 	case "DSA PRIVATE KEY":
-		return ParseDSAPrivateKey(buf)
+		result, err = ParseDSAPrivateKey(buf)
 	default:
-		return nil, fmt.Errorf("ssh: unsupported key type %q", block.Type)
+		err = fmt.Errorf("ssh: unsupported key type %q", block.Type)
 	}
+	// Because of deficiencies in the format, DecryptPEMBlock does not always
+	// detect an incorrect password. In these cases decrypted DER bytes is
+	// random noise. If the parsing of the key returns an asn1.StructuralError
+	// we return x509.IncorrectPasswordError.
+	if _, ok := err.(asn1.StructuralError); ok {
+		return nil, x509.IncorrectPasswordError
+	}
+
+	return result, err
 }
 
 // ParseDSAPrivateKey returns a DSA private key from its ASN.1 DER encoding, as

ssh/keys_test.go

@@ -16,6 +16,7 @@ import (
 	"encoding/base64"
 	"encoding/hex"
 	"encoding/pem"
+	"errors"
 	"fmt"
 	"io"
 	"reflect"
@@ -221,6 +222,16 @@ func TestParseEncryptedPrivateKeysWithPassphrase(t *testing.T) {
 	}
 }
 
+func TestParseEncryptedPrivateKeysWithIncorrectPassphrase(t *testing.T) {
+	pem := testdata.PEMEncryptedKeys[0].PEMBytes
+	for i := 0; i < 4096; i++ {
+		_, err := ParseRawPrivateKeyWithPassphrase(pem, []byte(fmt.Sprintf("%d", i)))
+		if !errors.Is(err, x509.IncorrectPasswordError) {
+			t.Fatalf("expected error: %v, got: %v", x509.IncorrectPasswordError, err)
+		}
+	}
+}
+
 func TestParseDSA(t *testing.T) {
 	// We actually exercise the ParsePrivateKey codepath here, as opposed to
 	// using the ParseRawPrivateKey+NewSignerFromKey path that testdata_test.go
@@ -599,7 +610,7 @@ func TestKnownHostsParsing(t *testing.T) {
 func TestFingerprintLegacyMD5(t *testing.T) {
 	pub, _ := getTestKey()
 	fingerprint := FingerprintLegacyMD5(pub)
-	want := "fb:61:6d:1a:e3:f0:95:45:3c:a0:79:be:4a:93:63:66" // ssh-keygen -lf -E md5 rsa
+	want := "b7:ef:d3:d5:89:29:52:96:9f:df:47:41:4d:15:37:f4" // ssh-keygen -lf -E md5 rsa
 	if fingerprint != want {
 		t.Errorf("got fingerprint %q want %q", fingerprint, want)
 	}
@@ -608,7 +619,7 @@ func TestFingerprintLegacyMD5(t *testing.T) {
 func TestFingerprintSHA256(t *testing.T) {
 	pub, _ := getTestKey()
 	fingerprint := FingerprintSHA256(pub)
-	want := "SHA256:Anr3LjZK8YVpjrxu79myrW9Hrb/wpcMNpVvTq/RcBm8" // ssh-keygen -lf rsa
+	want := "SHA256:fi5+D7UmDZDE9Q2sAVvvlpcQSIakN4DERdINgXd2AnE" // ssh-keygen -lf rsa
 	if fingerprint != want {
 		t.Errorf("got fingerprint %q want %q", fingerprint, want)
 	}

ssh/mempipe_test.go

@@ -13,9 +13,10 @@ import (
 // An in-memory packetConn. It is safe to call Close and writePacket
 // from different goroutines.
 type memTransport struct {
-	eof     bool
-	pending [][]byte
-	write   *memTransport
+	eof        bool
+	pending    [][]byte
+	write      *memTransport
+	writeCount uint64
 	sync.Mutex
 	*sync.Cond
 }
@@ -63,9 +64,16 @@ func (t *memTransport) writePacket(p []byte) error {
 	copy(c, p)
 	t.write.pending = append(t.write.pending, c)
 	t.write.Cond.Signal()
+	t.writeCount++
 	return nil
 }
 
+func (t *memTransport) getWriteCount() uint64 {
+	t.write.Lock()
+	defer t.write.Unlock()
+	return t.writeCount
+}
+
 func memPipe() (a, b packetConn) {
 	t1 := memTransport{}
 	t2 := memTransport{}
@@ -81,6 +89,9 @@ func TestMemPipe(t *testing.T) {
 	if err := a.writePacket([]byte{42}); err != nil {
 		t.Fatalf("writePacket: %v", err)
 	}
+	if wc := a.(*memTransport).getWriteCount(); wc != 1 {
+		t.Fatalf("got %v, want 1", wc)
+	}
 	if err := a.Close(); err != nil {
 		t.Fatal("Close: ", err)
 	}
@@ -95,6 +106,9 @@ func TestMemPipe(t *testing.T) {
 	if err != io.EOF {
 		t.Fatalf("got %v, %v, want EOF", p, err)
 	}
+	if wc := b.(*memTransport).getWriteCount(); wc != 0 {
+		t.Fatalf("got %v, want 0", wc)
+	}
 }
 
 func TestDoubleClose(t *testing.T) {

ssh/mux_test.go

@@ -10,7 +10,6 @@ import (
 	"io"
 	"sync"
 	"testing"
-	"time"
 )
 
 func muxPair() (*mux, *mux) {
@@ -112,7 +111,11 @@ func TestMuxReadWrite(t *testing.T) {
 
 	magic := "hello world"
 	magicExt := "hello stderr"
+	var wg sync.WaitGroup
+	t.Cleanup(wg.Wait)
+	wg.Add(1)
 	go func() {
+		defer wg.Done()
 		_, err := s.Write([]byte(magic))
 		if err != nil {
 			t.Errorf("Write: %v", err)
@@ -152,13 +155,15 @@ func TestMuxChannelOverflow(t *testing.T) {
 	defer writer.Close()
 	defer mux.Close()
 
-	wDone := make(chan int, 1)
+	var wg sync.WaitGroup
+	t.Cleanup(wg.Wait)
+	wg.Add(1)
 	go func() {
+		defer wg.Done()
 		if _, err := writer.Write(make([]byte, channelWindowSize)); err != nil {
 			t.Errorf("could not fill window: %v", err)
 		}
 		writer.Write(make([]byte, 1))
-		wDone <- 1
 	}()
 	writer.remoteWin.waitWriterBlocked()
 
@@ -175,7 +180,40 @@ func TestMuxChannelOverflow(t *testing.T) {
 	if _, err := reader.SendRequest("hello", true, nil); err == nil {
 		t.Errorf("SendRequest succeeded.")
 	}
-	<-wDone
+}
+
+func TestMuxChannelReadUnblock(t *testing.T) {
+	reader, writer, mux := channelPair(t)
+	defer reader.Close()
+	defer writer.Close()
+	defer mux.Close()
+
+	var wg sync.WaitGroup
+	t.Cleanup(wg.Wait)
+	wg.Add(1)
+	go func() {
+		defer wg.Done()
+		if _, err := writer.Write(make([]byte, channelWindowSize)); err != nil {
+			t.Errorf("could not fill window: %v", err)
+		}
+		if _, err := writer.Write(make([]byte, 1)); err != nil {
+			t.Errorf("Write: %v", err)
+		}
+		writer.Close()
+	}()
+
+	writer.remoteWin.waitWriterBlocked()
+
+	buf := make([]byte, 32768)
+	for {
+		_, err := reader.Read(buf)
+		if err == io.EOF {
+			break
+		}
+		if err != nil {
+			t.Fatalf("Read: %v", err)
+		}
+	}
 }
 
 func TestMuxChannelCloseWriteUnblock(t *testing.T) {
@@ -184,20 +222,21 @@ func TestMuxChannelCloseWriteUnblock(t *testing.T) {
 	defer writer.Close()
 	defer mux.Close()
 
-	wDone := make(chan int, 1)
+	var wg sync.WaitGroup
+	t.Cleanup(wg.Wait)
+	wg.Add(1)
 	go func() {
+		defer wg.Done()
 		if _, err := writer.Write(make([]byte, channelWindowSize)); err != nil {
 			t.Errorf("could not fill window: %v", err)
 		}
 		if _, err := writer.Write(make([]byte, 1)); err != io.EOF {
 			t.Errorf("got %v, want EOF for unblock write", err)
 		}
-		wDone <- 1
 	}()
 
 	writer.remoteWin.waitWriterBlocked()
 	reader.Close()
-	<-wDone
 }
 
 func TestMuxConnectionCloseWriteUnblock(t *testing.T) {
@@ -206,20 +245,21 @@ func TestMuxConnectionCloseWriteUnblock(t *testing.T) {
 	defer writer.Close()
 	defer mux.Close()
 
-	wDone := make(chan int, 1)
+	var wg sync.WaitGroup
+	t.Cleanup(wg.Wait)
+	wg.Add(1)
 	go func() {
+		defer wg.Done()
 		if _, err := writer.Write(make([]byte, channelWindowSize)); err != nil {
 			t.Errorf("could not fill window: %v", err)
 		}
 		if _, err := writer.Write(make([]byte, 1)); err != io.EOF {
 			t.Errorf("got %v, want EOF for unblock write", err)
 		}
-		wDone <- 1
 	}()
 
 	writer.remoteWin.waitWriterBlocked()
 	mux.Close()
-	<-wDone
 }
 
 func TestMuxReject(t *testing.T) {
@@ -227,7 +267,12 @@ func TestMuxReject(t *testing.T) {
 	defer server.Close()
 	defer client.Close()
 
+	var wg sync.WaitGroup
+	t.Cleanup(wg.Wait)
+	wg.Add(1)
 	go func() {
+		defer wg.Done()
+
 		ch, ok := <-server.incomingChannels
 		if !ok {
 			t.Error("cannot accept channel")
@@ -267,6 +312,7 @@ func TestMuxChannelRequest(t *testing.T) {
 
 	var received int
 	var wg sync.WaitGroup
+	t.Cleanup(wg.Wait)
 	wg.Add(1)
 	go func() {
 		for r := range server.incomingRequests {
@@ -295,7 +341,6 @@ func TestMuxChannelRequest(t *testing.T) {
 	}
 	if ok {
 		t.Errorf("SendRequest(no): %v", ok)
-
 	}
 
 	client.Close()
@@ -389,13 +434,8 @@ func TestMuxUnknownChannelRequests(t *testing.T) {
 
 	// Wait for the server to send the keepalive message and receive back a
 	// response.
-	select {
-	case err := <-kDone:
-		if err != nil {
-			t.Fatal(err)
-		}
-	case <-time.After(10 * time.Second):
-		t.Fatalf("server never received ack")
+	if err := <-kDone; err != nil {
+		t.Fatal(err)
 	}
 
 	// Confirm client hasn't closed.
@@ -403,13 +443,9 @@ func TestMuxUnknownChannelRequests(t *testing.T) {
 		t.Fatalf("failed to send keepalive: %v", err)
 	}
 
-	select {
-	case err := <-kDone:
-		if err != nil {
-			t.Fatal(err)
-		}
-	case <-time.After(10 * time.Second):
-		t.Fatalf("server never shut down")
+	// Wait for the server to shut down.
+	if err := <-kDone; err != nil {
+		t.Fatal(err)
 	}
 }
 
@@ -525,11 +561,7 @@ func TestMuxClosedChannel(t *testing.T) {
 	defer ch.Close()
 
 	// Wait for the server to close the channel and send the keepalive.
-	select {
-	case <-kDone:
-	case <-time.After(10 * time.Second):
-		t.Fatalf("server never received ack")
-	}
+	<-kDone
 
 	// Make sure the channel closed.
 	if _, ok := <-ch.incomingRequests; ok {
@@ -541,22 +573,29 @@ func TestMuxClosedChannel(t *testing.T) {
 		t.Fatalf("failed to send keepalive: %v", err)
 	}
 
-	select {
-	case <-kDone:
-	case <-time.After(10 * time.Second):
-		t.Fatalf("server never shut down")
-	}
+	// Wait for the server to shut down.
+	<-kDone
 }
 
 func TestMuxGlobalRequest(t *testing.T) {
+	var sawPeek bool
+	var wg sync.WaitGroup
+	defer func() {
+		wg.Wait()
+		if !sawPeek {
+			t.Errorf("never saw 'peek' request")
+		}
+	}()
+
 	clientMux, serverMux := muxPair()
 	defer serverMux.Close()
 	defer clientMux.Close()
 
-	var seen bool
+	wg.Add(1)
 	go func() {
+		defer wg.Done()
 		for r := range serverMux.incomingRequests {
-			seen = seen || r.Type == "peek"
+			sawPeek = sawPeek || r.Type == "peek"
 			if r.WantReply {
 				err := r.Reply(r.Type == "yes",
 					append([]byte(r.Type), r.Payload...))
@@ -586,10 +625,6 @@ func TestMuxGlobalRequest(t *testing.T) {
 		t.Errorf("SendRequest(\"no\", true, \"a\"): %v %v %v",
 			ok, data, err)
 	}
-
-	if !seen {
-		t.Errorf("never saw 'peek' request")
-	}
 }
 
 func TestMuxGlobalRequestUnblock(t *testing.T) {
@@ -739,7 +774,13 @@ func TestMuxMaxPacketSize(t *testing.T) {
 		t.Errorf("could not send packet")
 	}
 
-	go a.SendRequest("hello", false, nil)
+	var wg sync.WaitGroup
+	t.Cleanup(wg.Wait)
+	wg.Add(1)
+	go func() {
+		a.SendRequest("hello", false, nil)
+		wg.Done()
+	}()
 
 	_, ok := <-b.incomingRequests
 	if ok {
@@ -747,6 +788,43 @@ func TestMuxMaxPacketSize(t *testing.T) {
 	}
 }
 
+func TestMuxChannelWindowDeferredUpdates(t *testing.T) {
+	s, c, mux := channelPair(t)
+	cTransport := mux.conn.(*memTransport)
+	defer s.Close()
+	defer c.Close()
+	defer mux.Close()
+
+	var wg sync.WaitGroup
+	t.Cleanup(wg.Wait)
+
+	data := make([]byte, 1024)
+
+	wg.Add(1)
+	go func() {
+		defer wg.Done()
+		_, err := s.Write(data)
+		if err != nil {
+			t.Errorf("Write: %v", err)
+			return
+		}
+	}()
+	cWritesInit := cTransport.getWriteCount()
+	buf := make([]byte, 1)
+	for i := 0; i < len(data); i++ {
+		n, err := c.Read(buf)
+		if n != len(buf) || err != nil {
+			t.Fatalf("Read: %v, %v", n, err)
+		}
+	}
+	cWrites := cTransport.getWriteCount() - cWritesInit
+	// reading 1 KiB should not cause any window updates to be sent, but allow
+	// for some unexpected writes
+	if cWrites > 30 {
+		t.Fatalf("reading 1 KiB from channel caused %v writes", cWrites)
+	}
+}
+
 // Don't ship code with debug=true.
 func TestDebug(t *testing.T) {
 	if debugMux {

ssh/server.go

@@ -64,6 +64,13 @@ type ServerConfig struct {
 	// Config contains configuration shared between client and server.
 	Config
 
+	// PublicKeyAuthAlgorithms specifies the supported client public key
+	// authentication algorithms. Note that this should not include certificate
+	// types since those use the underlying algorithm. This list is sent to the
+	// client if it supports the server-sig-algs extension. Order is irrelevant.
+	// If unspecified then a default set of algorithms is used.
+	PublicKeyAuthAlgorithms []string
+
 	hostKeys []Signer
 
 	// NoClientAuth is true if clients are allowed to connect without
@@ -201,9 +208,20 @@ func NewServerConn(c net.Conn, config *ServerConfig) (*ServerConn, <-chan NewCha
 	if fullConf.MaxAuthTries == 0 {
 		fullConf.MaxAuthTries = 6
 	}
+	if len(fullConf.PublicKeyAuthAlgorithms) == 0 {
+		fullConf.PublicKeyAuthAlgorithms = supportedPubKeyAuthAlgos
+	} else {
+		for _, algo := range fullConf.PublicKeyAuthAlgorithms {
+			if !contains(supportedPubKeyAuthAlgos, algo) {
+				c.Close()
+				return nil, nil, nil, fmt.Errorf("ssh: unsupported public key authentication algorithm %s", algo)
+			}
+		}
+	}
 	// Check if the config contains any unsupported key exchanges
 	for _, kex := range fullConf.KeyExchanges {
 		if _, ok := serverForbiddenKexAlgos[kex]; ok {
+			c.Close()
 			return nil, nil, nil, fmt.Errorf("ssh: unsupported key exchange %s for server", kex)
 		}
 	}
@@ -321,7 +339,7 @@ func checkSourceAddress(addr net.Addr, sourceAddrs string) error {
 	return fmt.Errorf("ssh: remote address %v is not allowed because of source-address restriction", addr)
 }
 
-func gssExchangeToken(gssapiConfig *GSSAPIWithMICConfig, firstToken []byte, s *connection,
+func gssExchangeToken(gssapiConfig *GSSAPIWithMICConfig, token []byte, s *connection,
 	sessionID []byte, userAuthReq userAuthRequestMsg) (authErr error, perms *Permissions, err error) {
 	gssAPIServer := gssapiConfig.Server
 	defer gssAPIServer.DeleteSecContext()
@@ -331,7 +349,7 @@ func gssExchangeToken(gssapiConfig *GSSAPIWithMICConfig, firstToken []byte, s *c
 			outToken     []byte
 			needContinue bool
 		)
-		outToken, srcName, needContinue, err = gssAPIServer.AcceptSecContext(firstToken)
+		outToken, srcName, needContinue, err = gssAPIServer.AcceptSecContext(token)
 		if err != nil {
 			return err, nil, nil
 		}
@@ -353,6 +371,7 @@ func gssExchangeToken(gssapiConfig *GSSAPIWithMICConfig, firstToken []byte, s *c
 		if err := Unmarshal(packet, userAuthGSSAPITokenReq); err != nil {
 			return nil, nil, err
 		}
+		token = userAuthGSSAPITokenReq.Token
 	}
 	packet, err := s.transport.readPacket()
 	if err != nil {
@@ -407,6 +426,35 @@ func (l ServerAuthError) Error() string {
 	return "[" + strings.Join(errs, ", ") + "]"
 }
 
+// ServerAuthCallbacks defines server-side authentication callbacks.
+type ServerAuthCallbacks struct {
+	// PasswordCallback behaves like [ServerConfig.PasswordCallback].
+	PasswordCallback func(conn ConnMetadata, password []byte) (*Permissions, error)
+
+	// PublicKeyCallback behaves like [ServerConfig.PublicKeyCallback].
+	PublicKeyCallback func(conn ConnMetadata, key PublicKey) (*Permissions, error)
+
+	// KeyboardInteractiveCallback behaves like [ServerConfig.KeyboardInteractiveCallback].
+	KeyboardInteractiveCallback func(conn ConnMetadata, client KeyboardInteractiveChallenge) (*Permissions, error)
+
+	// GSSAPIWithMICConfig behaves like [ServerConfig.GSSAPIWithMICConfig].
+	GSSAPIWithMICConfig *GSSAPIWithMICConfig
+}
+
+// PartialSuccessError can be returned by any of the [ServerConfig]
+// authentication callbacks to indicate to the client that authentication has
+// partially succeeded, but further steps are required.
+type PartialSuccessError struct {
+	// Next defines the authentication callbacks to apply to further steps. The
+	// available methods communicated to the client are based on the non-nil
+	// ServerAuthCallbacks fields.
+	Next ServerAuthCallbacks
+}
+
+func (p *PartialSuccessError) Error() string {
+	return "ssh: authenticated with partial success"
+}
+
 // ErrNoAuth is the error value returned if no
 // authentication method has been passed yet. This happens as a normal
 // part of the authentication loop, since the client first tries
@@ -420,8 +468,18 @@ func (s *connection) serverAuthenticate(config *ServerConfig) (*Permissions, err
 	var perms *Permissions
 
 	authFailures := 0
+	noneAuthCount := 0
 	var authErrs []error
 	var displayedBanner bool
+	partialSuccessReturned := false
+	// Set the initial authentication callbacks from the config. They can be
+	// changed if a PartialSuccessError is returned.
+	authConfig := ServerAuthCallbacks{
+		PasswordCallback:            config.PasswordCallback,
+		PublicKeyCallback:           config.PublicKeyCallback,
+		KeyboardInteractiveCallback: config.KeyboardInteractiveCallback,
+		GSSAPIWithMICConfig:         config.GSSAPIWithMICConfig,
+	}
 
 userAuthLoop:
 	for {
@@ -452,6 +510,11 @@ userAuthLoop:
 			return nil, errors.New("ssh: client attempted to negotiate for unknown service: " + userAuthReq.Service)
 		}
 
+		if s.user != userAuthReq.User && partialSuccessReturned {
+			return nil, fmt.Errorf("ssh: client changed the user after a partial success authentication, previous user %q, current user %q",
+				s.user, userAuthReq.User)
+		}
+
 		s.user = userAuthReq.User
 
 		if !displayedBanner && config.BannerCallback != nil {
@@ -472,20 +535,18 @@ userAuthLoop:
 
 		switch userAuthReq.Method {
 		case "none":
-			if config.NoClientAuth {
+			noneAuthCount++
+			// We don't allow none authentication after a partial success
+			// response.
+			if config.NoClientAuth && !partialSuccessReturned {
 				if config.NoClientAuthCallback != nil {
 					perms, authErr = config.NoClientAuthCallback(s)
 				} else {
 					authErr = nil
 				}
 			}
-
-			// allow initial attempt of 'none' without penalty
-			if authFailures == 0 {
-				authFailures--
-			}
 		case "password":
-			if config.PasswordCallback == nil {
+			if authConfig.PasswordCallback == nil {
 				authErr = errors.New("ssh: password auth not configured")
 				break
 			}
@@ -499,17 +560,17 @@ userAuthLoop:
 				return nil, parseError(msgUserAuthRequest)
 			}
 
-			perms, authErr = config.PasswordCallback(s, password)
+			perms, authErr = authConfig.PasswordCallback(s, password)
 		case "keyboard-interactive":
-			if config.KeyboardInteractiveCallback == nil {
+			if authConfig.KeyboardInteractiveCallback == nil {
 				authErr = errors.New("ssh: keyboard-interactive auth not configured")
 				break
 			}
 
 			prompter := &sshClientKeyboardInteractive{s}
-			perms, authErr = config.KeyboardInteractiveCallback(s, prompter.Challenge)
+			perms, authErr = authConfig.KeyboardInteractiveCallback(s, prompter.Challenge)
 		case "publickey":
-			if config.PublicKeyCallback == nil {
+			if authConfig.PublicKeyCallback == nil {
 				authErr = errors.New("ssh: publickey auth not configured")
 				break
 			}
@@ -524,7 +585,7 @@ userAuthLoop:
 				return nil, parseError(msgUserAuthRequest)
 			}
 			algo := string(algoBytes)
-			if !contains(supportedPubKeyAuthAlgos, underlyingAlgo(algo)) {
+			if !contains(config.PublicKeyAuthAlgorithms, underlyingAlgo(algo)) {
 				authErr = fmt.Errorf("ssh: algorithm %q not accepted", algo)
 				break
 			}
@@ -543,11 +604,18 @@ userAuthLoop:
 			if !ok {
 				candidate.user = s.user
 				candidate.pubKeyData = pubKeyData
-				candidate.perms, candidate.result = config.PublicKeyCallback(s, pubKey)
-				if candidate.result == nil && candidate.perms != nil && candidate.perms.CriticalOptions != nil && candidate.perms.CriticalOptions[sourceAddressCriticalOption] != "" {
-					candidate.result = checkSourceAddress(
+				candidate.perms, candidate.result = authConfig.PublicKeyCallback(s, pubKey)
+				_, isPartialSuccessError := candidate.result.(*PartialSuccessError)
+
+				if (candidate.result == nil || isPartialSuccessError) &&
+					candidate.perms != nil &&
+					candidate.perms.CriticalOptions != nil &&
+					candidate.perms.CriticalOptions[sourceAddressCriticalOption] != "" {
+					if err := checkSourceAddress(
 						s.RemoteAddr(),
-						candidate.perms.CriticalOptions[sourceAddressCriticalOption])
+						candidate.perms.CriticalOptions[sourceAddressCriticalOption]); err != nil {
+						candidate.result = err
+					}
 				}
 				cache.add(candidate)
 			}
@@ -559,8 +627,8 @@ userAuthLoop:
 				if len(payload) > 0 {
 					return nil, parseError(msgUserAuthRequest)
 				}
-
-				if candidate.result == nil {
+				_, isPartialSuccessError := candidate.result.(*PartialSuccessError)
+				if candidate.result == nil || isPartialSuccessError {
 					okMsg := userAuthPubKeyOkMsg{
 						Algo:   algo,
 						PubKey: pubKeyData,
@@ -591,7 +659,7 @@ userAuthLoop:
 				// algorithm name that corresponds to algo with
 				// sig.Format.  This is usually the same, but
 				// for certs, the names differ.
-				if !contains(supportedPubKeyAuthAlgos, sig.Format) {
+				if !contains(config.PublicKeyAuthAlgorithms, sig.Format) {
 					authErr = fmt.Errorf("ssh: algorithm %q not accepted", sig.Format)
 					break
 				}
@@ -610,11 +678,11 @@ userAuthLoop:
 				perms = candidate.perms
 			}
 		case "gssapi-with-mic":
-			if config.GSSAPIWithMICConfig == nil {
+			if authConfig.GSSAPIWithMICConfig == nil {
 				authErr = errors.New("ssh: gssapi-with-mic auth not configured")
 				break
 			}
-			gssapiConfig := config.GSSAPIWithMICConfig
+			gssapiConfig := authConfig.GSSAPIWithMICConfig
 			userAuthRequestGSSAPI, err := parseGSSAPIPayload(userAuthReq.Payload)
 			if err != nil {
 				return nil, parseError(msgUserAuthRequest)
@@ -670,49 +738,70 @@ userAuthLoop:
 			break userAuthLoop
 		}
 
-		authFailures++
-		if config.MaxAuthTries > 0 && authFailures >= config.MaxAuthTries {
-			// If we have hit the max attempts, don't bother sending the
-			// final SSH_MSG_USERAUTH_FAILURE message, since there are
-			// no more authentication methods which can be attempted,
-			// and this message may cause the client to re-attempt
-			// authentication while we send the disconnect message.
-			// Continue, and trigger the disconnect at the start of
-			// the loop.
-			//
-			// The SSH specification is somewhat confusing about this,
-			// RFC 4252 Section 5.1 requires each authentication failure
-			// be responded to with a respective SSH_MSG_USERAUTH_FAILURE
-			// message, but Section 4 says the server should disconnect
-			// after some number of attempts, but it isn't explicit which
-			// message should take precedence (i.e. should there be a failure
-			// message than a disconnect message, or if we are going to
-			// disconnect, should we only send that message.)
-			//
-			// Either way, OpenSSH disconnects immediately after the last
-			// failed authnetication attempt, and given they are typically
-			// considered the golden implementation it seems reasonable
-			// to match that behavior.
-			continue
+		var failureMsg userAuthFailureMsg
+
+		if partialSuccess, ok := authErr.(*PartialSuccessError); ok {
+			// After a partial success error we don't allow changing the user
+			// name and execute the NoClientAuthCallback.
+			partialSuccessReturned = true
+
+			// In case a partial success is returned, the server may send
+			// a new set of authentication methods.
+			authConfig = partialSuccess.Next
+
+			// Reset pubkey cache, as the new PublicKeyCallback might
+			// accept a different set of public keys.
+			cache = pubKeyCache{}
+
+			// Send back a partial success message to the user.
+			failureMsg.PartialSuccess = true
+		} else {
+			// Allow initial attempt of 'none' without penalty.
+			if authFailures > 0 || userAuthReq.Method != "none" || noneAuthCount != 1 {
+				authFailures++
+			}
+			if config.MaxAuthTries > 0 && authFailures >= config.MaxAuthTries {
+				// If we have hit the max attempts, don't bother sending the
+				// final SSH_MSG_USERAUTH_FAILURE message, since there are
+				// no more authentication methods which can be attempted,
+				// and this message may cause the client to re-attempt
+				// authentication while we send the disconnect message.
+				// Continue, and trigger the disconnect at the start of
+				// the loop.
+				//
+				// The SSH specification is somewhat confusing about this,
+				// RFC 4252 Section 5.1 requires each authentication failure
+				// be responded to with a respective SSH_MSG_USERAUTH_FAILURE
+				// message, but Section 4 says the server should disconnect
+				// after some number of attempts, but it isn't explicit which
+				// message should take precedence (i.e. should there be a failure
+				// message than a disconnect message, or if we are going to
+				// disconnect, should we only send that message.)
+				//
+				// Either way, OpenSSH disconnects immediately after the last
+				// failed authentication attempt, and given they are typically
+				// considered the golden implementation it seems reasonable
+				// to match that behavior.
+				continue
+			}
 		}
 
-		var failureMsg userAuthFailureMsg
-		if config.PasswordCallback != nil {
+		if authConfig.PasswordCallback != nil {
 			failureMsg.Methods = append(failureMsg.Methods, "password")
 		}
-		if config.PublicKeyCallback != nil {
+		if authConfig.PublicKeyCallback != nil {
 			failureMsg.Methods = append(failureMsg.Methods, "publickey")
 		}
-		if config.KeyboardInteractiveCallback != nil {
+		if authConfig.KeyboardInteractiveCallback != nil {
 			failureMsg.Methods = append(failureMsg.Methods, "keyboard-interactive")
 		}
-		if config.GSSAPIWithMICConfig != nil && config.GSSAPIWithMICConfig.Server != nil &&
-			config.GSSAPIWithMICConfig.AllowLogin != nil {
+		if authConfig.GSSAPIWithMICConfig != nil && authConfig.GSSAPIWithMICConfig.Server != nil &&
+			authConfig.GSSAPIWithMICConfig.AllowLogin != nil {
 			failureMsg.Methods = append(failureMsg.Methods, "gssapi-with-mic")
 		}
 
 		if len(failureMsg.Methods) == 0 {
-			return nil, errors.New("ssh: no authentication methods configured but NoClientAuth is also false")
+			return nil, errors.New("ssh: no authentication methods available")
 		}
 
 		if err := s.transport.writePacket(Marshal(&failureMsg)); err != nil {

ssh/server_multi_auth_test.go

@@ -0,0 +1,412 @@
+// Copyright 2024 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ssh
+
+import (
+	"bytes"
+	"errors"
+	"fmt"
+	"strings"
+	"testing"
+)
+
+func doClientServerAuth(t *testing.T, serverConfig *ServerConfig, clientConfig *ClientConfig) ([]error, error) {
+	c1, c2, err := netPipe()
+	if err != nil {
+		t.Fatalf("netPipe: %v", err)
+	}
+	defer c1.Close()
+	defer c2.Close()
+
+	var serverAuthErrors []error
+
+	serverConfig.AddHostKey(testSigners["rsa"])
+	serverConfig.AuthLogCallback = func(conn ConnMetadata, method string, err error) {
+		serverAuthErrors = append(serverAuthErrors, err)
+	}
+	go newServer(c1, serverConfig)
+	c, _, _, err := NewClientConn(c2, "", clientConfig)
+	if err == nil {
+		c.Close()
+	}
+	return serverAuthErrors, err
+}
+
+func TestMultiStepAuth(t *testing.T) {
+	// This user can login with password, public key or public key + password.
+	username := "testuser"
+	// This user can login with public key + password only.
+	usernameSecondFactor := "testuser_second_factor"
+	errPwdAuthFailed := errors.New("password auth failed")
+	errWrongSequence := errors.New("wrong sequence")
+
+	serverConfig := &ServerConfig{
+		PasswordCallback: func(conn ConnMetadata, password []byte) (*Permissions, error) {
+			if conn.User() == usernameSecondFactor {
+				return nil, errWrongSequence
+			}
+			if conn.User() == username && string(password) == clientPassword {
+				return nil, nil
+			}
+			return nil, errPwdAuthFailed
+		},
+		PublicKeyCallback: func(conn ConnMetadata, key PublicKey) (*Permissions, error) {
+			if bytes.Equal(key.Marshal(), testPublicKeys["rsa"].Marshal()) {
+				if conn.User() == usernameSecondFactor {
+					return nil, &PartialSuccessError{
+						Next: ServerAuthCallbacks{
+							PasswordCallback: func(conn ConnMetadata, password []byte) (*Permissions, error) {
+								if string(password) == clientPassword {
+									return nil, nil
+								}
+								return nil, errPwdAuthFailed
+							},
+						},
+					}
+				}
+				return nil, nil
+			}
+			return nil, fmt.Errorf("pubkey for %q not acceptable", conn.User())
+		},
+	}
+
+	clientConfig := &ClientConfig{
+		User: usernameSecondFactor,
+		Auth: []AuthMethod{
+			PublicKeys(testSigners["rsa"]),
+			Password(clientPassword),
+		},
+		HostKeyCallback: InsecureIgnoreHostKey(),
+	}
+
+	serverAuthErrors, err := doClientServerAuth(t, serverConfig, clientConfig)
+	if err != nil {
+		t.Fatalf("client login error: %s", err)
+	}
+
+	// The error sequence is:
+	// - no auth passed yet
+	// - partial success
+	// - nil
+	if len(serverAuthErrors) != 3 {
+		t.Fatalf("unexpected number of server auth errors: %v, errors: %+v", len(serverAuthErrors), serverAuthErrors)
+	}
+	if _, ok := serverAuthErrors[1].(*PartialSuccessError); !ok {
+		t.Fatalf("expected partial success error, got: %v", serverAuthErrors[1])
+	}
+	// Now test a wrong sequence.
+	clientConfig.Auth = []AuthMethod{
+		Password(clientPassword),
+		PublicKeys(testSigners["rsa"]),
+	}
+
+	serverAuthErrors, err = doClientServerAuth(t, serverConfig, clientConfig)
+	if err == nil {
+		t.Fatal("client login with wrong sequence must fail")
+	}
+	// The error sequence is:
+	// - no auth passed yet
+	// - wrong sequence
+	// - partial success
+	if len(serverAuthErrors) != 3 {
+		t.Fatalf("unexpected number of server auth errors: %v, errors: %+v", len(serverAuthErrors), serverAuthErrors)
+	}
+	if serverAuthErrors[1] != errWrongSequence {
+		t.Fatal("server not returned wrong sequence")
+	}
+	if _, ok := serverAuthErrors[2].(*PartialSuccessError); !ok {
+		t.Fatalf("expected partial success error, got: %v", serverAuthErrors[2])
+	}
+	// Now test using a correct sequence but a wrong password before the right
+	// one.
+	n := 0
+	passwords := []string{"WRONG", "WRONG", clientPassword}
+	clientConfig.Auth = []AuthMethod{
+		PublicKeys(testSigners["rsa"]),
+		RetryableAuthMethod(PasswordCallback(func() (string, error) {
+			p := passwords[n]
+			n++
+			return p, nil
+		}), 3),
+	}
+
+	serverAuthErrors, err = doClientServerAuth(t, serverConfig, clientConfig)
+	if err != nil {
+		t.Fatalf("client login error: %s", err)
+	}
+	// The error sequence is:
+	// - no auth passed yet
+	// - partial success
+	// - wrong password
+	// - wrong password
+	// - nil
+	if len(serverAuthErrors) != 5 {
+		t.Fatalf("unexpected number of server auth errors: %v, errors: %+v", len(serverAuthErrors), serverAuthErrors)
+	}
+	if _, ok := serverAuthErrors[1].(*PartialSuccessError); !ok {
+		t.Fatal("server not returned partial success")
+	}
+	if serverAuthErrors[2] != errPwdAuthFailed {
+		t.Fatal("server not returned password authentication failed")
+	}
+	if serverAuthErrors[3] != errPwdAuthFailed {
+		t.Fatal("server not returned password authentication failed")
+	}
+	// Only password authentication should fail.
+	clientConfig.Auth = []AuthMethod{
+		Password(clientPassword),
+	}
+
+	serverAuthErrors, err = doClientServerAuth(t, serverConfig, clientConfig)
+	if err == nil {
+		t.Fatal("client login with password only must fail")
+	}
+	// The error sequence is:
+	// - no auth passed yet
+	// - wrong sequence
+	if len(serverAuthErrors) != 2 {
+		t.Fatalf("unexpected number of server auth errors: %v, errors: %+v", len(serverAuthErrors), serverAuthErrors)
+	}
+	if serverAuthErrors[1] != errWrongSequence {
+		t.Fatal("server not returned wrong sequence")
+	}
+
+	// Only public key authentication should fail.
+	clientConfig.Auth = []AuthMethod{
+		PublicKeys(testSigners["rsa"]),
+	}
+
+	serverAuthErrors, err = doClientServerAuth(t, serverConfig, clientConfig)
+	if err == nil {
+		t.Fatal("client login with public key only must fail")
+	}
+	// The error sequence is:
+	// - no auth passed yet
+	// - partial success
+	if len(serverAuthErrors) != 2 {
+		t.Fatalf("unexpected number of server auth errors: %v, errors: %+v", len(serverAuthErrors), serverAuthErrors)
+	}
+	if _, ok := serverAuthErrors[1].(*PartialSuccessError); !ok {
+		t.Fatal("server not returned partial success")
+	}
+
+	// Public key and wrong password.
+	clientConfig.Auth = []AuthMethod{
+		PublicKeys(testSigners["rsa"]),
+		Password("WRONG"),
+	}
+
+	serverAuthErrors, err = doClientServerAuth(t, serverConfig, clientConfig)
+	if err == nil {
+		t.Fatal("client login with wrong password after public key must fail")
+	}
+	// The error sequence is:
+	// - no auth passed yet
+	// - partial success
+	// - password auth failed
+	if len(serverAuthErrors) != 3 {
+		t.Fatalf("unexpected number of server auth errors: %v, errors: %+v", len(serverAuthErrors), serverAuthErrors)
+	}
+	if _, ok := serverAuthErrors[1].(*PartialSuccessError); !ok {
+		t.Fatal("server not returned partial success")
+	}
+	if serverAuthErrors[2] != errPwdAuthFailed {
+		t.Fatal("server not returned password authentication failed")
+	}
+
+	// Public key, public key again and then correct password. Public key
+	// authentication is attempted only once because the partial success error
+	// returns only "password" as the allowed authentication method.
+	clientConfig.Auth = []AuthMethod{
+		PublicKeys(testSigners["rsa"]),
+		PublicKeys(testSigners["rsa"]),
+		Password(clientPassword),
+	}
+
+	serverAuthErrors, err = doClientServerAuth(t, serverConfig, clientConfig)
+	if err != nil {
+		t.Fatalf("client login error: %s", err)
+	}
+	// The error sequence is:
+	// - no auth passed yet
+	// - partial success
+	// - nil
+	if len(serverAuthErrors) != 3 {
+		t.Fatalf("unexpected number of server auth errors: %v, errors: %+v", len(serverAuthErrors), serverAuthErrors)
+	}
+	if _, ok := serverAuthErrors[1].(*PartialSuccessError); !ok {
+		t.Fatal("server not returned partial success")
+	}
+
+	// The unrestricted username can do anything
+	clientConfig = &ClientConfig{
+		User: username,
+		Auth: []AuthMethod{
+			PublicKeys(testSigners["rsa"]),
+			Password(clientPassword),
+		},
+		HostKeyCallback: InsecureIgnoreHostKey(),
+	}
+
+	_, err = doClientServerAuth(t, serverConfig, clientConfig)
+	if err != nil {
+		t.Fatalf("unrestricted client login error: %s", err)
+	}
+
+	clientConfig = &ClientConfig{
+		User: username,
+		Auth: []AuthMethod{
+			PublicKeys(testSigners["rsa"]),
+		},
+		HostKeyCallback: InsecureIgnoreHostKey(),
+	}
+
+	_, err = doClientServerAuth(t, serverConfig, clientConfig)
+	if err != nil {
+		t.Fatalf("unrestricted client login error: %s", err)
+	}
+
+	clientConfig = &ClientConfig{
+		User: username,
+		Auth: []AuthMethod{
+			Password(clientPassword),
+		},
+		HostKeyCallback: InsecureIgnoreHostKey(),
+	}
+
+	_, err = doClientServerAuth(t, serverConfig, clientConfig)
+	if err != nil {
+		t.Fatalf("unrestricted client login error: %s", err)
+	}
+}
+
+func TestDynamicAuthCallbacks(t *testing.T) {
+	user1 := "user1"
+	user2 := "user2"
+	errInvalidCredentials := errors.New("invalid credentials")
+
+	serverConfig := &ServerConfig{
+		NoClientAuth: true,
+		NoClientAuthCallback: func(conn ConnMetadata) (*Permissions, error) {
+			switch conn.User() {
+			case user1:
+				return nil, &PartialSuccessError{
+					Next: ServerAuthCallbacks{
+						PasswordCallback: func(conn ConnMetadata, password []byte) (*Permissions, error) {
+							if conn.User() == user1 && string(password) == clientPassword {
+								return nil, nil
+							}
+							return nil, errInvalidCredentials
+						},
+					},
+				}
+			case user2:
+				return nil, &PartialSuccessError{
+					Next: ServerAuthCallbacks{
+						PublicKeyCallback: func(conn ConnMetadata, key PublicKey) (*Permissions, error) {
+							if bytes.Equal(key.Marshal(), testPublicKeys["rsa"].Marshal()) {
+								if conn.User() == user2 {
+									return nil, nil
+								}
+							}
+							return nil, errInvalidCredentials
+						},
+					},
+				}
+			default:
+				return nil, errInvalidCredentials
+			}
+		},
+	}
+
+	clientConfig := &ClientConfig{
+		User: user1,
+		Auth: []AuthMethod{
+			Password(clientPassword),
+		},
+		HostKeyCallback: InsecureIgnoreHostKey(),
+	}
+
+	serverAuthErrors, err := doClientServerAuth(t, serverConfig, clientConfig)
+	if err != nil {
+		t.Fatalf("client login error: %s", err)
+	}
+	// The error sequence is:
+	// - partial success
+	// - nil
+	if len(serverAuthErrors) != 2 {
+		t.Fatalf("unexpected number of server auth errors: %v, errors: %+v", len(serverAuthErrors), serverAuthErrors)
+	}
+	if _, ok := serverAuthErrors[0].(*PartialSuccessError); !ok {
+		t.Fatal("server not returned partial success")
+	}
+
+	clientConfig = &ClientConfig{
+		User: user2,
+		Auth: []AuthMethod{
+			PublicKeys(testSigners["rsa"]),
+		},
+		HostKeyCallback: InsecureIgnoreHostKey(),
+	}
+
+	serverAuthErrors, err = doClientServerAuth(t, serverConfig, clientConfig)
+	if err != nil {
+		t.Fatalf("client login error: %s", err)
+	}
+	// The error sequence is:
+	// - partial success
+	// - nil
+	if len(serverAuthErrors) != 2 {
+		t.Fatalf("unexpected number of server auth errors: %v, errors: %+v", len(serverAuthErrors), serverAuthErrors)
+	}
+	if _, ok := serverAuthErrors[0].(*PartialSuccessError); !ok {
+		t.Fatal("server not returned partial success")
+	}
+
+	// user1 cannot login with public key
+	clientConfig = &ClientConfig{
+		User: user1,
+		Auth: []AuthMethod{
+			PublicKeys(testSigners["rsa"]),
+		},
+		HostKeyCallback: InsecureIgnoreHostKey(),
+	}
+
+	serverAuthErrors, err = doClientServerAuth(t, serverConfig, clientConfig)
+	if err == nil {
+		t.Fatal("user1 login with public key must fail")
+	}
+	if !strings.Contains(err.Error(), "no supported methods remain") {
+		t.Errorf("got %v, expected 'no supported methods remain'", err)
+	}
+	if len(serverAuthErrors) != 1 {
+		t.Fatalf("unexpected number of server auth errors: %v, errors: %+v", len(serverAuthErrors), serverAuthErrors)
+	}
+	if _, ok := serverAuthErrors[0].(*PartialSuccessError); !ok {
+		t.Fatal("server not returned partial success")
+	}
+	// user2 cannot login with password
+	clientConfig = &ClientConfig{
+		User: user2,
+		Auth: []AuthMethod{
+			Password(clientPassword),
+		},
+		HostKeyCallback: InsecureIgnoreHostKey(),
+	}
+
+	serverAuthErrors, err = doClientServerAuth(t, serverConfig, clientConfig)
+	if err == nil {
+		t.Fatal("user2 login with password must fail")
+	}
+	if !strings.Contains(err.Error(), "no supported methods remain") {
+		t.Errorf("got %v, expected 'no supported methods remain'", err)
+	}
+	if len(serverAuthErrors) != 1 {
+		t.Fatalf("unexpected number of server auth errors: %v, errors: %+v", len(serverAuthErrors), serverAuthErrors)
+	}
+	if _, ok := serverAuthErrors[0].(*PartialSuccessError); !ok {
+		t.Fatal("server not returned partial success")
+	}
+}

ssh/server_test.go

@@ -0,0 +1,269 @@
+// Copyright 2023 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package ssh
+
+import (
+	"errors"
+	"io"
+	"net"
+	"strings"
+	"sync/atomic"
+	"testing"
+	"time"
+)
+
+func TestClientAuthRestrictedPublicKeyAlgos(t *testing.T) {
+	for _, tt := range []struct {
+		name      string
+		key       Signer
+		wantError bool
+	}{
+		{"rsa", testSigners["rsa"], false},
+		{"dsa", testSigners["dsa"], true},
+		{"ed25519", testSigners["ed25519"], true},
+	} {
+		c1, c2, err := netPipe()
+		if err != nil {
+			t.Fatalf("netPipe: %v", err)
+		}
+		defer c1.Close()
+		defer c2.Close()
+		serverConf := &ServerConfig{
+			PublicKeyAuthAlgorithms: []string{KeyAlgoRSASHA256, KeyAlgoRSASHA512},
+			PublicKeyCallback: func(conn ConnMetadata, key PublicKey) (*Permissions, error) {
+				return nil, nil
+			},
+		}
+		serverConf.AddHostKey(testSigners["ecdsap256"])
+
+		done := make(chan struct{})
+		go func() {
+			defer close(done)
+			NewServerConn(c1, serverConf)
+		}()
+
+		clientConf := ClientConfig{
+			User: "user",
+			Auth: []AuthMethod{
+				PublicKeys(tt.key),
+			},
+			HostKeyCallback: InsecureIgnoreHostKey(),
+		}
+
+		_, _, _, err = NewClientConn(c2, "", &clientConf)
+		if err != nil {
+			if !tt.wantError {
+				t.Errorf("%s: got unexpected error %q", tt.name, err.Error())
+			}
+		} else if tt.wantError {
+			t.Errorf("%s: succeeded, but want error", tt.name)
+		}
+		<-done
+	}
+}
+
+func TestMaxAuthTriesNoneMethod(t *testing.T) {
+	username := "testuser"
+	serverConfig := &ServerConfig{
+		MaxAuthTries: 2,
+		PasswordCallback: func(conn ConnMetadata, password []byte) (*Permissions, error) {
+			if conn.User() == username && string(password) == clientPassword {
+				return nil, nil
+			}
+			return nil, errors.New("invalid credentials")
+		},
+	}
+	c1, c2, err := netPipe()
+	if err != nil {
+		t.Fatalf("netPipe: %v", err)
+	}
+	defer c1.Close()
+	defer c2.Close()
+
+	var serverAuthErrors []error
+
+	serverConfig.AddHostKey(testSigners["rsa"])
+	serverConfig.AuthLogCallback = func(conn ConnMetadata, method string, err error) {
+		serverAuthErrors = append(serverAuthErrors, err)
+	}
+	go newServer(c1, serverConfig)
+
+	clientConfig := ClientConfig{
+		User:            username,
+		HostKeyCallback: InsecureIgnoreHostKey(),
+	}
+	clientConfig.SetDefaults()
+	// Our client will send 'none' auth only once, so we need to send the
+	// requests manually.
+	c := &connection{
+		sshConn: sshConn{
+			conn:          c2,
+			user:          username,
+			clientVersion: []byte(packageVersion),
+		},
+	}
+	c.serverVersion, err = exchangeVersions(c.sshConn.conn, c.clientVersion)
+	if err != nil {
+		t.Fatalf("unable to exchange version: %v", err)
+	}
+	c.transport = newClientTransport(
+		newTransport(c.sshConn.conn, clientConfig.Rand, true /* is client */),
+		c.clientVersion, c.serverVersion, &clientConfig, "", c.sshConn.RemoteAddr())
+	if err := c.transport.waitSession(); err != nil {
+		t.Fatalf("unable to wait session: %v", err)
+	}
+	c.sessionID = c.transport.getSessionID()
+	if err := c.transport.writePacket(Marshal(&serviceRequestMsg{serviceUserAuth})); err != nil {
+		t.Fatalf("unable to send ssh-userauth message: %v", err)
+	}
+	packet, err := c.transport.readPacket()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(packet) > 0 && packet[0] == msgExtInfo {
+		packet, err = c.transport.readPacket()
+		if err != nil {
+			t.Fatal(err)
+		}
+	}
+	var serviceAccept serviceAcceptMsg
+	if err := Unmarshal(packet, &serviceAccept); err != nil {
+		t.Fatal(err)
+	}
+	for i := 0; i <= serverConfig.MaxAuthTries; i++ {
+		auth := new(noneAuth)
+		_, _, err := auth.auth(c.sessionID, clientConfig.User, c.transport, clientConfig.Rand, nil)
+		if i < serverConfig.MaxAuthTries {
+			if err != nil {
+				t.Fatal(err)
+			}
+			continue
+		}
+		if err == nil {
+			t.Fatal("client: got no error")
+		} else if !strings.Contains(err.Error(), "too many authentication failures") {
+			t.Fatalf("client: got unexpected error: %v", err)
+		}
+	}
+	if len(serverAuthErrors) != 3 {
+		t.Fatalf("unexpected number of server auth errors: %v, errors: %+v", len(serverAuthErrors), serverAuthErrors)
+	}
+	for _, err := range serverAuthErrors {
+		if !errors.Is(err, ErrNoAuth) {
+			t.Errorf("go error: %v; want: %v", err, ErrNoAuth)
+		}
+	}
+}
+
+func TestMaxAuthTriesFirstNoneAuthErrorIgnored(t *testing.T) {
+	username := "testuser"
+	serverConfig := &ServerConfig{
+		MaxAuthTries: 1,
+		PasswordCallback: func(conn ConnMetadata, password []byte) (*Permissions, error) {
+			if conn.User() == username && string(password) == clientPassword {
+				return nil, nil
+			}
+			return nil, errors.New("invalid credentials")
+		},
+	}
+	clientConfig := &ClientConfig{
+		User: username,
+		Auth: []AuthMethod{
+			Password(clientPassword),
+		},
+		HostKeyCallback: InsecureIgnoreHostKey(),
+	}
+
+	serverAuthErrors, err := doClientServerAuth(t, serverConfig, clientConfig)
+	if err != nil {
+		t.Fatalf("client login error: %s", err)
+	}
+	if len(serverAuthErrors) != 2 {
+		t.Fatalf("unexpected number of server auth errors: %v, errors: %+v", len(serverAuthErrors), serverAuthErrors)
+	}
+	if !errors.Is(serverAuthErrors[0], ErrNoAuth) {
+		t.Errorf("go error: %v; want: %v", serverAuthErrors[0], ErrNoAuth)
+	}
+	if serverAuthErrors[1] != nil {
+		t.Errorf("unexpected error: %v", serverAuthErrors[1])
+	}
+}
+
+func TestNewServerConnValidationErrors(t *testing.T) {
+	serverConf := &ServerConfig{
+		PublicKeyAuthAlgorithms: []string{CertAlgoRSAv01},
+	}
+	c := &markerConn{}
+	_, _, _, err := NewServerConn(c, serverConf)
+	if err == nil {
+		t.Fatal("NewServerConn with invalid public key auth algorithms succeeded")
+	}
+	if !c.isClosed() {
+		t.Fatal("NewServerConn with invalid public key auth algorithms left connection open")
+	}
+	if c.isUsed() {
+		t.Fatal("NewServerConn with invalid public key auth algorithms used connection")
+	}
+
+	serverConf = &ServerConfig{
+		Config: Config{
+			KeyExchanges: []string{kexAlgoDHGEXSHA256},
+		},
+	}
+	c = &markerConn{}
+	_, _, _, err = NewServerConn(c, serverConf)
+	if err == nil {
+		t.Fatal("NewServerConn with unsupported key exchange succeeded")
+	}
+	if !c.isClosed() {
+		t.Fatal("NewServerConn with unsupported key exchange left connection open")
+	}
+	if c.isUsed() {
+		t.Fatal("NewServerConn with unsupported key exchange used connection")
+	}
+}
+
+type markerConn struct {
+	closed uint32
+	used   uint32
+}
+
+func (c *markerConn) isClosed() bool {
+	return atomic.LoadUint32(&c.closed) != 0
+}
+
+func (c *markerConn) isUsed() bool {
+	return atomic.LoadUint32(&c.used) != 0
+}
+
+func (c *markerConn) Close() error {
+	atomic.StoreUint32(&c.closed, 1)
+	return nil
+}
+
+func (c *markerConn) Read(b []byte) (n int, err error) {
+	atomic.StoreUint32(&c.used, 1)
+	if atomic.LoadUint32(&c.closed) != 0 {
+		return 0, net.ErrClosed
+	} else {
+		return 0, io.EOF
+	}
+}
+
+func (c *markerConn) Write(b []byte) (n int, err error) {
+	atomic.StoreUint32(&c.used, 1)
+	if atomic.LoadUint32(&c.closed) != 0 {
+		return 0, net.ErrClosed
+	} else {
+		return 0, io.ErrClosedPipe
+	}
+}
+
+func (*markerConn) LocalAddr() net.Addr  { return nil }
+func (*markerConn) RemoteAddr() net.Addr { return nil }
+
+func (*markerConn) SetDeadline(t time.Time) error      { return nil }
+func (*markerConn) SetReadDeadline(t time.Time) error  { return nil }
+func (*markerConn) SetWriteDeadline(t time.Time) error { return nil }

ssh/session_test.go

@@ -13,6 +13,7 @@ import (
 	"io"
 	"math/rand"
 	"net"
+	"sync"
 	"testing"
 
 	"golang.org/x/crypto/ssh/terminal"
@@ -27,8 +28,14 @@ func dial(handler serverType, t *testing.T) *Client {
 		t.Fatalf("netPipe: %v", err)
 	}
 
+	var wg sync.WaitGroup
+	t.Cleanup(wg.Wait)
+	wg.Add(1)
 	go func() {
-		defer c1.Close()
+		defer func() {
+			c1.Close()
+			wg.Done()
+		}()
 		conf := ServerConfig{
 			NoClientAuth: true,
 		}
@@ -39,7 +46,11 @@ func dial(handler serverType, t *testing.T) *Client {
 			t.Errorf("Unable to handshake: %v", err)
 			return
 		}
-		go DiscardRequests(reqs)
+		wg.Add(1)
+		go func() {
+			DiscardRequests(reqs)
+			wg.Done()
+		}()
 
 		for newCh := range chans {
 			if newCh.ChannelType() != "session" {
@@ -52,8 +63,10 @@ func dial(handler serverType, t *testing.T) *Client {
 				t.Errorf("Accept: %v", err)
 				continue
 			}
+			wg.Add(1)
 			go func() {
 				handler(ch, inReqs, t)
+				wg.Done()
 			}()
 		}
 		if err := conn.Wait(); err != io.EOF {
@@ -338,8 +351,13 @@ func TestServerWindow(t *testing.T) {
 		t.Fatal(err)
 	}
 	defer session.Close()
-	result := make(chan []byte)
 
+	serverStdin, err := session.StdinPipe()
+	if err != nil {
+		t.Fatalf("StdinPipe failed: %v", err)
+	}
+
+	result := make(chan []byte)
 	go func() {
 		defer close(result)
 		echoedBuf := bytes.NewBuffer(make([]byte, 0, windowTestBytes))
@@ -355,10 +373,6 @@ func TestServerWindow(t *testing.T) {
 		result <- echoedBuf.Bytes()
 	}()
 
-	serverStdin, err := session.StdinPipe()
-	if err != nil {
-		t.Fatalf("StdinPipe failed: %v", err)
-	}
 	written, err := copyNRandomly("stdin", serverStdin, origBuf, windowTestBytes)
 	if err != nil {
 		t.Errorf("failed to copy origBuf to serverStdin: %v", err)
@@ -648,29 +662,44 @@ func TestSessionID(t *testing.T) {
 		User:            "user",
 	}
 
+	var wg sync.WaitGroup
+	t.Cleanup(wg.Wait)
+
 	srvErrCh := make(chan error, 1)
+	wg.Add(1)
 	go func() {
+		defer wg.Done()
 		conn, chans, reqs, err := NewServerConn(c1, serverConf)
 		srvErrCh <- err
 		if err != nil {
 			return
 		}
 		serverID <- conn.SessionID()
-		go DiscardRequests(reqs)
+		wg.Add(1)
+		go func() {
+			DiscardRequests(reqs)
+			wg.Done()
+		}()
 		for ch := range chans {
 			ch.Reject(Prohibited, "")
 		}
 	}()
 
 	cliErrCh := make(chan error, 1)
+	wg.Add(1)
 	go func() {
+		defer wg.Done()
 		conn, chans, reqs, err := NewClientConn(c2, "", clientConf)
 		cliErrCh <- err
 		if err != nil {
 			return
 		}
 		clientID <- conn.SessionID()
-		go DiscardRequests(reqs)
+		wg.Add(1)
+		go func() {
+			DiscardRequests(reqs)
+			wg.Done()
+		}()
 		for ch := range chans {
 			ch.Reject(Prohibited, "")
 		}
@@ -738,6 +767,8 @@ func TestHostKeyAlgorithms(t *testing.T) {
 	serverConf.AddHostKey(testSigners["rsa"])
 	serverConf.AddHostKey(testSigners["ecdsa"])
 
+	var wg sync.WaitGroup
+	t.Cleanup(wg.Wait)
 	connect := func(clientConf *ClientConfig, want string) {
 		var alg string
 		clientConf.HostKeyCallback = func(h string, a net.Addr, key PublicKey) error {
@@ -751,7 +782,11 @@ func TestHostKeyAlgorithms(t *testing.T) {
 		defer c1.Close()
 		defer c2.Close()
 
-		go NewServerConn(c1, serverConf)
+		wg.Add(1)
+		go func() {
+			NewServerConn(c1, serverConf)
+			wg.Done()
+		}()
 		_, _, _, err = NewClientConn(c2, "", clientConf)
 		if err != nil {
 			t.Fatalf("NewClientConn: %v", err)
@@ -785,7 +820,11 @@ func TestHostKeyAlgorithms(t *testing.T) {
 	defer c1.Close()
 	defer c2.Close()
 
-	go NewServerConn(c1, serverConf)
+	wg.Add(1)
+	go func() {
+		NewServerConn(c1, serverConf)
+		wg.Done()
+	}()
 	clientConf.HostKeyAlgorithms = []string{"nonexistent-hostkey-algo"}
 	_, _, _, err = NewClientConn(c2, "", clientConf)
 	if err == nil {
@@ -818,14 +857,22 @@ func TestServerClientAuthCallback(t *testing.T) {
 		User:            someUsername,
 	}
 
+	var wg sync.WaitGroup
+	t.Cleanup(wg.Wait)
+	wg.Add(1)
 	go func() {
+		defer wg.Done()
 		_, chans, reqs, err := NewServerConn(c1, serverConf)
 		if err != nil {
 			t.Errorf("server handshake: %v", err)
 			userCh <- "error"
 			return
 		}
-		go DiscardRequests(reqs)
+		wg.Add(1)
+		go func() {
+			DiscardRequests(reqs)
+			wg.Done()
+		}()
 		for ch := range chans {
 			ch.Reject(Prohibited, "")
 		}

ssh/tcpip.go

@@ -5,6 +5,7 @@
 package ssh
 
 import (
+	"context"
 	"errors"
 	"fmt"
 	"io"
@@ -332,6 +333,40 @@ func (l *tcpListener) Addr() net.Addr {
 	return l.laddr
 }
 
+// DialContext initiates a connection to the addr from the remote host.
+//
+// The provided Context must be non-nil. If the context expires before the
+// connection is complete, an error is returned. Once successfully connected,
+// any expiration of the context will not affect the connection.
+//
+// See func Dial for additional information.
+func (c *Client) DialContext(ctx context.Context, n, addr string) (net.Conn, error) {
+	if err := ctx.Err(); err != nil {
+		return nil, err
+	}
+	type connErr struct {
+		conn net.Conn
+		err  error
+	}
+	ch := make(chan connErr)
+	go func() {
+		conn, err := c.Dial(n, addr)
+		select {
+		case ch <- connErr{conn, err}:
+		case <-ctx.Done():
+			if conn != nil {
+				conn.Close()
+			}
+		}
+	}()
+	select {
+	case res := <-ch:
+		return res.conn, res.err
+	case <-ctx.Done():
+		return nil, ctx.Err()
+	}
+}
+
 // Dial initiates a connection to the addr from the remote host.
 // The resulting connection has a zero LocalAddr() and RemoteAddr().
 func (c *Client) Dial(n, addr string) (net.Conn, error) {

ssh/tcpip_test.go

@@ -5,7 +5,10 @@
 package ssh
 
 import (
+	"context"
+	"net"
 	"testing"
+	"time"
 )
 
 func TestAutoPortListenBroken(t *testing.T) {
@@ -18,3 +21,33 @@ func TestAutoPortListenBroken(t *testing.T) {
 		t.Errorf("version %q marked as broken", works)
 	}
 }
+
+func TestClientImplementsDialContext(t *testing.T) {
+	type ContextDialer interface {
+		DialContext(context.Context, string, string) (net.Conn, error)
+	}
+	// Belt and suspenders assertion, since package net does not
+	// declare a ContextDialer type.
+	var _ ContextDialer = &net.Dialer{}
+	var _ ContextDialer = &Client{}
+}
+
+func TestClientDialContextWithCancel(t *testing.T) {
+	c := &Client{}
+	ctx, cancel := context.WithCancel(context.Background())
+	cancel()
+	_, err := c.DialContext(ctx, "tcp", "localhost:1000")
+	if err != context.Canceled {
+		t.Errorf("DialContext: got nil error, expected %v", context.Canceled)
+	}
+}
+
+func TestClientDialContextWithDeadline(t *testing.T) {
+	c := &Client{}
+	ctx, cancel := context.WithDeadline(context.Background(), time.Now())
+	defer cancel()
+	_, err := c.DialContext(ctx, "tcp", "localhost:1000")
+	if err != context.DeadlineExceeded {
+		t.Errorf("DialContext: got nil error, expected %v", context.DeadlineExceeded)
+	}
+}

ssh/test/agent_unix_test.go

@@ -3,7 +3,6 @@
 // license that can be found in the LICENSE file.
 
 //go:build aix || darwin || dragonfly || freebsd || linux || netbsd || openbsd || solaris
-// +build aix darwin dragonfly freebsd linux netbsd openbsd solaris
 
 package test
 
@@ -35,6 +34,7 @@ func TestAgentForward(t *testing.T) {
 
 	sess, err := conn.NewSession()
 	if err != nil {
+		skipIfIssue64959(t, err)
 		t.Fatalf("NewSession: %v", err)
 	}
 	if err := agent.RequestAgentForwarding(sess); err != nil {

ssh/test/banner_test.go

@@ -3,7 +3,6 @@
 // license that can be found in the LICENSE file.
 
 //go:build aix || darwin || dragonfly || freebsd || linux || netbsd || openbsd || solaris
-// +build aix darwin dragonfly freebsd linux netbsd openbsd solaris
 
 package test
 

ssh/test/cert_test.go

@@ -3,7 +3,6 @@
 // license that can be found in the LICENSE file.
 
 //go:build aix || darwin || dragonfly || freebsd || linux || netbsd || openbsd || solaris
-// +build aix darwin dragonfly freebsd linux netbsd openbsd solaris
 
 package test
 
@@ -20,7 +19,7 @@ func TestCertLogin(t *testing.T) {
 	s := newServer(t)
 
 	// Use a key different from the default.
-	clientKey := testSigners["dsa"]
+	clientKey := testSigners["ed25519"]
 	caAuthKey := testSigners["ecdsa"]
 	cert := &ssh.Certificate{
 		Key:             clientKey.PublicKey(),

ssh/test/dial_unix_test.go

@@ -3,13 +3,13 @@
 // license that can be found in the LICENSE file.
 
 //go:build !windows && !js && !wasip1
-// +build !windows,!js,!wasip1
 
 package test
 
 // direct-tcpip and direct-streamlocal functional tests
 
 import (
+	"context"
 	"fmt"
 	"io"
 	"net"
@@ -47,8 +47,13 @@ func testDial(t *testing.T, n, listenAddr string, x dialTester) {
 		}
 	}()
 
-	conn, err := sshConn.Dial(n, l.Addr().String())
+	ctx, cancel := context.WithCancel(context.Background())
+	conn, err := sshConn.DialContext(ctx, n, l.Addr().String())
+	// Canceling the context after dial should have no effect
+	// on the opened connection.
+	cancel()
 	if err != nil {
+		skipIfIssue64959(t, err)
 		t.Fatalf("Dial: %v", err)
 	}
 	x.TestClientConn(t, conn)

ssh/test/forward_unix_test.go

@@ -3,7 +3,6 @@
 // license that can be found in the LICENSE file.
 
 //go:build aix || darwin || dragonfly || freebsd || linux || netbsd || openbsd || solaris
-// +build aix darwin dragonfly freebsd linux netbsd openbsd solaris
 
 package test
 
@@ -13,6 +12,7 @@ import (
 	"io"
 	"math/rand"
 	"net"
+	"runtime"
 	"testing"
 	"time"
 )
@@ -28,6 +28,9 @@ func testPortForward(t *testing.T, n, listenAddr string) {
 
 	sshListener, err := conn.Listen(n, listenAddr)
 	if err != nil {
+		if runtime.GOOS == "darwin" && err == io.EOF {
+			t.Skipf("skipping test broken on some versions of macOS; see https://go.dev/issue/64959")
+		}
 		t.Fatal(err)
 	}
 
@@ -123,6 +126,9 @@ func testAcceptClose(t *testing.T, n, listenAddr string) {
 
 	sshListener, err := conn.Listen(n, listenAddr)
 	if err != nil {
+		if runtime.GOOS == "darwin" && err == io.EOF {
+			t.Skipf("skipping test broken on some versions of macOS; see https://go.dev/issue/64959")
+		}
 		t.Fatal(err)
 	}
 
@@ -164,6 +170,9 @@ func testPortForwardConnectionClose(t *testing.T, n, listenAddr string) {
 
 	sshListener, err := client.Listen(n, listenAddr)
 	if err != nil {
+		if runtime.GOOS == "darwin" && err == io.EOF {
+			t.Skipf("skipping test broken on some versions of macOS; see https://go.dev/issue/64959")
+		}
 		t.Fatal(err)
 	}
 

ssh/test/multi_auth_test.go

@@ -15,7 +15,6 @@
 // (for linux) in file ./sshd_test_pw.c.
 
 //go:build linux
-// +build linux
 
 package test