add ext-info-s to KEX algorithms only in the first key exchange

drakkan · drakkan · commit 2b413598b393 · 2022-03-30T16:02:13.000+02:00
Signed-off-by: Nicola Murino &lt;nicola.murino@gmail.com&gt;
diff --git a/ssh/handshake.go b/ssh/handshake.go
@@ -479,7 +479,11 @@ func (t *handshakeTransport) sendKexInit() error {
 				msg.ServerHostKeyAlgos = append(msg.ServerHostKeyAlgos, keyFormat)
 			}
 		}
-		msg.KexAlgos = append(msg.KexAlgos, extInfoServer)
+		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, extInfoServer)
+		}
 	} else {
 		msg.ServerHostKeyAlgos = t.hostKeyAlgorithms
 

Original file line number	Diff line number	Diff line change
`@@ -479,7 +479,11 @@ func (t *handshakeTransport) sendKexInit() error {`
`479`	`479`	`msg.ServerHostKeyAlgos = append(msg.ServerHostKeyAlgos, keyFormat)`
`480`	`480`	`}`
`481`	`481`	`}`
`482`		`- msg.KexAlgos = append(msg.KexAlgos, extInfoServer)`
	`482`	`+ if firstKeyExchange := t.sessionID == nil; firstKeyExchange {`
	`483`	`+ msg.KexAlgos = make([]string, 0, len(t.config.KeyExchanges)+1)`
	`484`	`+ msg.KexAlgos = append(msg.KexAlgos, t.config.KeyExchanges...)`
	`485`	`+ msg.KexAlgos = append(msg.KexAlgos, extInfoServer)`
	`486`	`+ }`
`483`	`487`	`} else {`
`484`	`488`	`msg.ServerHostKeyAlgos = t.hostKeyAlgorithms`
`485`	`489`