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ssh: add support for FIPS mode

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Unsupported algoritms are silently ignored and not negotiated, or
rejected

Fixes golang/go#75061

Change-Id: I08d50d10a97c08e78aedead89ca61beceff88918
Reviewed-on: https://go-review.googlesource.com/c/crypto/+/698795
Reviewed-by: Mio Mio <miomio0086@gmail.com>
Reviewed-by: Junyang Shao <shaojunyang@google.com>
Reviewed-by: Filippo Valsorda <filippo@golang.org>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
This commit is contained in:
Nicola Murino
2025-09-27 12:36:52 -07:00
parent ddb4e80c6a
commit 66c3d8ce71
8 changed files with 163 additions and 69 deletions
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ssh/mac.go
+29 -13
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@@ -7,11 +7,13 @@ package ssh
// Message authentication support
import (
"crypto/fips140"
"crypto/hmac"
"crypto/sha1"
"crypto/sha256"
"crypto/sha512"
"hash"
"slices"
)
type macMode struct {
@@ -46,23 +48,37 @@ func (t truncatingMAC) Size() int {
func (t truncatingMAC) BlockSize() int { return t.hmac.BlockSize() }
var macModes = map[string]*macMode{
HMACSHA512ETM: {64, true, func(key []byte) hash.Hash {
// macModes defines the supported MACs. MACs not included are not supported
// and will not be negotiated, even if explicitly configured. When FIPS mode is
// enabled, only FIPS-approved algorithms are included.
var macModes = map[string]*macMode{}
func init() {
macModes[HMACSHA512ETM] = &macMode{64, true, func(key []byte) hash.Hash {
return hmac.New(sha512.New, key)
}},
HMACSHA256ETM: {32, true, func(key []byte) hash.Hash {
}}
macModes[HMACSHA256ETM] = &macMode{32, true, func(key []byte) hash.Hash {
return hmac.New(sha256.New, key)
}},
HMACSHA512: {64, false, func(key []byte) hash.Hash {
}}
macModes[HMACSHA512] = &macMode{64, false, func(key []byte) hash.Hash {
return hmac.New(sha512.New, key)
}},
HMACSHA256: {32, false, func(key []byte) hash.Hash {
}}
macModes[HMACSHA256] = &macMode{32, false, func(key []byte) hash.Hash {
return hmac.New(sha256.New, key)
}},
HMACSHA1: {20, false, func(key []byte) hash.Hash {
}}
if fips140.Enabled() {
defaultMACs = slices.DeleteFunc(defaultMACs, func(algo string) bool {
_, ok := macModes[algo]
return !ok
})
return
}
macModes[HMACSHA1] = &macMode{20, false, func(key []byte) hash.Hash {
return hmac.New(sha1.New, key)
}},
InsecureHMACSHA196: {20, false, func(key []byte) hash.Hash {
}}
macModes[InsecureHMACSHA196] = &macMode{20, false, func(key []byte) hash.Hash {
return truncatingMAC{12, hmac.New(sha1.New, key)}
}},
}}
}