Add support for "hmac-sha2-512-etm@openssh.com"

Change-Id: I0203881afd7ad72e68f76650817451d7e292c91b
GitHub-Last-Rev: 42b4119e1987e7a46aa06a2b142d5fd3ef6f216a
GitHub-Pull-Request: golang/crypto#129
Reviewed-on: https://go-review.googlesource.com/c/crypto/+/226982
Run-TryBot: Han-Wen Nienhuys <hanwen@google.com>
Reviewed-by: Han-Wen Nienhuys <hanwen@google.com>
Auto-Submit: Han-Wen Nienhuys <hanwen@google.com>
Reviewed-by: David Chase <drchase@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>

ssh/common.go

@@ -85,7 +85,7 @@ var supportedHostKeyAlgos = []string{
 // This is based on RFC 4253, section 6.4, but with hmac-md5 variants removed
 // because they have reached the end of their useful life.
 var supportedMACs = []string{
-	"hmac-sha2-256-etm@openssh.com", "hmac-sha2-256", "hmac-sha1", "hmac-sha1-96",
+	"hmac-sha2-512-etm@openssh.com", "hmac-sha2-256-etm@openssh.com", "hmac-sha2-256", "hmac-sha1", "hmac-sha1-96",
 }
 
 var supportedCompressions = []string{compressionNone}

ssh/mac.go

@@ -10,6 +10,7 @@ import (
 	"crypto/hmac"
 	"crypto/sha1"
 	"crypto/sha256"
+	"crypto/sha512"
 	"hash"
 )
 
@@ -46,6 +47,9 @@ func (t truncatingMAC) Size() int {
 func (t truncatingMAC) BlockSize() int { return t.hmac.BlockSize() }
 
 var macModes = map[string]*macMode{
+	"hmac-sha2-512-etm@openssh.com": {64, true, func(key []byte) hash.Hash {
+		return hmac.New(sha512.New, key)
+	}},
 	"hmac-sha2-256-etm@openssh.com": {32, true, func(key []byte) hash.Hash {
 		return hmac.New(sha256.New, key)
 	}},