ssh: support new curve25519-sha256 kex name

RFC 8731 standardized [email protected] as curve25519-sha256, and some systems only advertise support for the new name. Fixes golang/go#48756 Change-Id: Ice35874cd8c07ad48752686ac368bf11ab793f77 Co-authored-by: Filippo Valsorda <[email protected]> Reviewed-on: https://go-review.googlesource.com/c/crypto/+/385394 Trust: Filippo Valsorda <[email protected]> Run-TryBot: Filippo Valsorda <[email protected]> Trust: Matt Layher <[email protected]> TryBot-Result: Gopher Robot <[email protected]> Reviewed-by: Roland Shoemaker <[email protected]>
affordablemobiles · Aug 2, 2022 · 0e77833 · 0e77833
1 parent 56e3008
commit 0e77833
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Showing 2 changed files with 12 additions and 11 deletions.
diff --git a/ssh/common.go b/ssh/common.go
@@ -60,7 +60,7 @@ var preferredCiphers = []string{
 // supportedKexAlgos specifies the supported key-exchange algorithms in
 // preference order.
 var supportedKexAlgos = []string{
-	kexAlgoCurve25519SHA256,
+	kexAlgoCurve25519SHA256, kexAlgoCurve25519SHA256LibSSH,
 	// P384 and P521 are not constant-time yet, but since we don't
 	// reuse ephemeral keys, using them for ECDH should be OK.
 	kexAlgoECDH256, kexAlgoECDH384, kexAlgoECDH521,
@@ -77,7 +77,7 @@ var serverForbiddenKexAlgos = map[string]struct{}{
 // preferredKexAlgos specifies the default preference for key-exchange algorithms
 // in preference order.
 var preferredKexAlgos = []string{
-	kexAlgoCurve25519SHA256,
+	kexAlgoCurve25519SHA256, kexAlgoCurve25519SHA256LibSSH,
 	kexAlgoECDH256, kexAlgoECDH384, kexAlgoECDH521,
 	kexAlgoDH14SHA1,
 }

diff --git a/ssh/kex.go b/ssh/kex.go
@@ -20,12 +20,13 @@ import (
 )
 
 const (
-	kexAlgoDH1SHA1          = "diffie-hellman-group1-sha1"
-	kexAlgoDH14SHA1         = "diffie-hellman-group14-sha1"
-	kexAlgoECDH256          = "ecdh-sha2-nistp256"
-	kexAlgoECDH384          = "ecdh-sha2-nistp384"
-	kexAlgoECDH521          = "ecdh-sha2-nistp521"
-	kexAlgoCurve25519SHA256 = "[email protected]"
+	kexAlgoDH1SHA1                = "diffie-hellman-group1-sha1"
+	kexAlgoDH14SHA1               = "diffie-hellman-group14-sha1"
+	kexAlgoECDH256                = "ecdh-sha2-nistp256"
+	kexAlgoECDH384                = "ecdh-sha2-nistp384"
+	kexAlgoECDH521                = "ecdh-sha2-nistp521"
+	kexAlgoCurve25519SHA256LibSSH = "[email protected]"
+	kexAlgoCurve25519SHA256       = "curve25519-sha256"
 
 	// For the following kex only the client half contains a production
 	// ready implementation. The server half only consists of a minimal
@@ -410,13 +411,13 @@ func init() {
 	kexAlgoMap[kexAlgoECDH384] = &ecdh{elliptic.P384()}
 	kexAlgoMap[kexAlgoECDH256] = &ecdh{elliptic.P256()}
 	kexAlgoMap[kexAlgoCurve25519SHA256] = &curve25519sha256{}
+	kexAlgoMap[kexAlgoCurve25519SHA256LibSSH] = &curve25519sha256{}
 	kexAlgoMap[kexAlgoDHGEXSHA1] = &dhGEXSHA{hashFunc: crypto.SHA1}
 	kexAlgoMap[kexAlgoDHGEXSHA256] = &dhGEXSHA{hashFunc: crypto.SHA256}
 }
 
-// curve25519sha256 implements the [email protected] key
-// agreement protocol, as described in
-// https://git.libssh.org/projects/libssh.git/tree/doc/[email protected]
+// curve25519sha256 implements the curve25519-sha256 (formerly known as
+// [email protected]) key exchange method, as described in RFC 8731.
 type curve25519sha256 struct{}
 
 type curve25519KeyPair struct {