ssh: export supported algorithms

Fixes golang/go#61537

Change-Id: If3478121e3ae445391e3faeceeb889d75e9e3214
Reviewed-on: https://go-review.googlesource.com/c/crypto/+/531935
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Nicola Murino <nicola.murino@gmail.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
Reviewed-by: Filippo Valsorda <filippo@golang.org>

ssh/test/recording_client_test.go

@@ -236,7 +236,7 @@ func recordingsClientConfig() *ssh.ClientConfig {
 	config := clientConfig()
 	config.SetDefaults()
 	// Remove ML-KEM since it only works with Go 1.24.
-	if config.KeyExchanges[0] == "mlkem768x25519-sha256" {
+	if config.KeyExchanges[0] == ssh.KeyExchangeMLKEM768X25519 {
 		config.KeyExchanges = config.KeyExchanges[1:]
 	}
 	config.Auth = []ssh.AuthMethod{
@@ -352,7 +352,7 @@ func TestHostKeyCheck(t *testing.T) {
 
 	// change the keys.
 	hostDB.keys[ssh.KeyAlgoRSA][25]++
-	hostDB.keys[ssh.KeyAlgoDSA][25]++
+	hostDB.keys[ssh.InsecureKeyAlgoDSA][25]++
 	hostDB.keys[ssh.KeyAlgoECDSA256][25]++
 
 	test := clientTest{

ssh/test/recording_server_test.go

@@ -219,7 +219,7 @@ func recordingsServerConfig() *ssh.ServerConfig {
 	config.SetDefaults()
 	// Remove ML-KEM since it only works with Go 1.24.
 	config.SetDefaults()
-	if config.KeyExchanges[0] == "mlkem768x25519-sha256" {
+	if config.KeyExchanges[0] == ssh.KeyExchangeMLKEM768X25519 {
 		config.KeyExchanges = config.KeyExchanges[1:]
 	}
 	config.AddHostKey(testSigners["rsa"])

ssh/test/recording_test.go

@@ -128,7 +128,7 @@ func clientConfig() *ssh.ClientConfig {
 		HostKeyCallback: hostKeyDB().Check,
 		HostKeyAlgorithms: []string{ // by default, don't allow certs as this affects the hostKeyDB checker
 			ssh.KeyAlgoECDSA256, ssh.KeyAlgoECDSA384, ssh.KeyAlgoECDSA521,
-			ssh.KeyAlgoRSA, ssh.KeyAlgoDSA,
+			ssh.KeyAlgoRSA, ssh.InsecureKeyAlgoDSA,
 			ssh.KeyAlgoED25519,
 		},
 	}

ssh/test/session_test.go

@@ -224,8 +224,8 @@ func testOneCipher(t *testing.T, cipher string, cipherOrder []string) {
 }
 
 var deprecatedCiphers = []string{
-	"aes128-cbc", "3des-cbc",
-	"arcfour128", "arcfour256",
+	ssh.InsecureCipherAES128CBC, ssh.InsecureCipherTripleDESCBC,
+	ssh.InsecureCipherRC4128, ssh.InsecureCipherRC4256,
 }
 
 func TestCiphers(t *testing.T) {