ssh: add AlgorithmNegotiationError
Fixes golang/go#61536 Change-Id: Id38cc6d46879dbe2bdea04dec061596387ec6cfe Reviewed-on: https://go-review.googlesource.com/c/crypto/+/559056 LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com> Reviewed-by: Filippo Valsorda <filippo@golang.org> Reviewed-by: David Chase <drchase@google.com> Auto-Submit: Nicola Murino <nicola.murino@gmail.com> Reviewed-by: Carlos Amedee <carlos@golang.org>
This commit is contained in:
Nicola Murino
committed by
Gopher Robot
Gopher Robot
parent
b3790b8d91
commit
74e709ad8a
+1
-1
@@ -289,7 +289,7 @@ func pickSignatureAlgorithm(signer Signer, extensions map[string][]byte) (MultiA
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}
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}
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algo, err := findCommon("public key signature algorithm", keyAlgos, serverAlgos)
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algo, err := findCommon("public key signature algorithm", keyAlgos, serverAlgos, true)
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if err != nil {
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// If there is no overlap, return the fallback algorithm to support
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// servers that fail to list all supported algorithms.
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+35
-10
@@ -336,7 +336,7 @@ func parseError(tag uint8) error {
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return fmt.Errorf("ssh: parse error in message type %d", tag)
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}
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func findCommon(what string, client []string, server []string) (common string, err error) {
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func findCommon(what string, client []string, server []string, isClient bool) (string, error) {
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for _, c := range client {
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for _, s := range server {
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if c == s {
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@@ -344,7 +344,32 @@ func findCommon(what string, client []string, server []string) (common string, e
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}
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}
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}
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return "", fmt.Errorf("ssh: no common algorithm for %s; client offered: %v, server offered: %v", what, client, server)
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err := &AlgorithmNegotiationError{
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What: what,
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}
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if isClient {
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err.SupportedAlgorithms = client
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err.RequestedAlgorithms = server
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} else {
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err.SupportedAlgorithms = server
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err.RequestedAlgorithms = client
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}
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return "", err
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}
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// AlgorithmNegotiationError defines the error returned if the client and the
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// server cannot agree on an algorithm for key exchange, host key, cipher, MAC.
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type AlgorithmNegotiationError struct {
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What string
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// RequestedAlgorithms lists the algorithms supported by the peer.
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RequestedAlgorithms []string
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// SupportedAlgorithms lists the algorithms supported on our side.
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SupportedAlgorithms []string
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}
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func (a *AlgorithmNegotiationError) Error() string {
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return fmt.Sprintf("ssh: no common algorithm for %s; we offered: %v, peer offered: %v",
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a.What, a.SupportedAlgorithms, a.RequestedAlgorithms)
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}
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// DirectionAlgorithms defines the algorithms negotiated in one direction
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@@ -379,12 +404,12 @@ var aeadCiphers = map[string]bool{
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func findAgreedAlgorithms(isClient bool, clientKexInit, serverKexInit *kexInitMsg) (algs *NegotiatedAlgorithms, err error) {
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result := &NegotiatedAlgorithms{}
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result.KeyExchange, err = findCommon("key exchange", clientKexInit.KexAlgos, serverKexInit.KexAlgos)
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result.KeyExchange, err = findCommon("key exchange", clientKexInit.KexAlgos, serverKexInit.KexAlgos, isClient)
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if err != nil {
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return
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}
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result.HostKey, err = findCommon("host key", clientKexInit.ServerHostKeyAlgos, serverKexInit.ServerHostKeyAlgos)
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result.HostKey, err = findCommon("host key", clientKexInit.ServerHostKeyAlgos, serverKexInit.ServerHostKeyAlgos, isClient)
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if err != nil {
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return
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}
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@@ -394,36 +419,36 @@ func findAgreedAlgorithms(isClient bool, clientKexInit, serverKexInit *kexInitMs
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ctos, stoc = stoc, ctos
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}
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ctos.Cipher, err = findCommon("client to server cipher", clientKexInit.CiphersClientServer, serverKexInit.CiphersClientServer)
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ctos.Cipher, err = findCommon("client to server cipher", clientKexInit.CiphersClientServer, serverKexInit.CiphersClientServer, isClient)
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if err != nil {
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return
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}
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stoc.Cipher, err = findCommon("server to client cipher", clientKexInit.CiphersServerClient, serverKexInit.CiphersServerClient)
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stoc.Cipher, err = findCommon("server to client cipher", clientKexInit.CiphersServerClient, serverKexInit.CiphersServerClient, isClient)
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if err != nil {
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return
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}
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if !aeadCiphers[ctos.Cipher] {
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ctos.MAC, err = findCommon("client to server MAC", clientKexInit.MACsClientServer, serverKexInit.MACsClientServer)
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ctos.MAC, err = findCommon("client to server MAC", clientKexInit.MACsClientServer, serverKexInit.MACsClientServer, isClient)
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if err != nil {
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return
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}
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}
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if !aeadCiphers[stoc.Cipher] {
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stoc.MAC, err = findCommon("server to client MAC", clientKexInit.MACsServerClient, serverKexInit.MACsServerClient)
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stoc.MAC, err = findCommon("server to client MAC", clientKexInit.MACsServerClient, serverKexInit.MACsServerClient, isClient)
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if err != nil {
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return
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}
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}
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ctos.compression, err = findCommon("client to server compression", clientKexInit.CompressionClientServer, serverKexInit.CompressionClientServer)
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ctos.compression, err = findCommon("client to server compression", clientKexInit.CompressionClientServer, serverKexInit.CompressionClientServer, isClient)
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if err != nil {
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return
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}
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stoc.compression, err = findCommon("server to client compression", clientKexInit.CompressionServerClient, serverKexInit.CompressionServerClient)
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stoc.compression, err = findCommon("server to client compression", clientKexInit.CompressionServerClient, serverKexInit.CompressionServerClient, isClient)
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if err != nil {
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return
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}
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@@ -1294,3 +1294,73 @@ func TestNegotiatedAlgorithms(t *testing.T) {
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}
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}
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}
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func TestAlgorithmNegotiationError(t *testing.T) {
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c1, c2, err := netPipe()
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if err != nil {
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t.Fatalf("netPipe: %v", err)
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}
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defer c1.Close()
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defer c2.Close()
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serverConf := &ServerConfig{
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Config: Config{
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Ciphers: []string{CipherAES128CTR, CipherAES256CTR},
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},
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PasswordCallback: func(conn ConnMetadata, password []byte) (*Permissions, error) {
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return &Permissions{}, nil
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},
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}
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serverConf.AddHostKey(testSigners["rsa"])
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srvErrCh := make(chan error, 1)
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go func() {
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_, _, _, err := NewServerConn(c1, serverConf)
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srvErrCh <- err
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}()
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clientConf := &ClientConfig{
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Config: Config{
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Ciphers: []string{CipherAES128GCM, CipherAES256GCM},
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},
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User: "test",
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Auth: []AuthMethod{Password("testpw")},
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HostKeyCallback: FixedHostKey(testSigners["rsa"].PublicKey()),
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}
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_, _, _, err = NewClientConn(c2, "", clientConf)
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if err == nil {
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t.Fatal("client connection succeded expected algorithm negotiation error")
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}
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var negotiationError *AlgorithmNegotiationError
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if !errors.As(err, &negotiationError) {
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t.Fatalf("expected algorithm negotiation error, got %v", err)
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}
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expectedErrorString := fmt.Sprintf("ssh: handshake failed: ssh: no common algorithm for client to server cipher; we offered: %v, peer offered: %v",
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clientConf.Ciphers, serverConf.Ciphers)
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if err.Error() != expectedErrorString {
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t.Fatalf("expected error string %q, got %q", expectedErrorString, err.Error())
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}
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if !reflect.DeepEqual(negotiationError.RequestedAlgorithms, serverConf.Ciphers) {
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t.Fatalf("expected requested algorithms %v, got %v", serverConf.Ciphers, negotiationError.RequestedAlgorithms)
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}
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if !reflect.DeepEqual(negotiationError.SupportedAlgorithms, clientConf.Ciphers) {
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t.Fatalf("expected supported algorithms %v, got %v", clientConf.Ciphers, negotiationError.SupportedAlgorithms)
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}
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err = <-srvErrCh
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negotiationError = nil
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if !errors.As(err, &negotiationError) {
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t.Fatalf("expected algorithm negotiation error, got %v", err)
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}
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expectedErrorString = fmt.Sprintf("ssh: no common algorithm for client to server cipher; we offered: %v, peer offered: %v",
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serverConf.Ciphers, clientConf.Ciphers)
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if err.Error() != expectedErrorString {
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t.Fatalf("expected error string %q, got %q", expectedErrorString, err.Error())
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}
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if !reflect.DeepEqual(negotiationError.RequestedAlgorithms, clientConf.Ciphers) {
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t.Fatalf("expected requested algorithms %v, got %v", clientConf.Ciphers, negotiationError.RequestedAlgorithms)
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}
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if !reflect.DeepEqual(negotiationError.SupportedAlgorithms, serverConf.Ciphers) {
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t.Fatalf("expected supported algorithms %v, got %v", serverConf.Ciphers, negotiationError.SupportedAlgorithms)
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}
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}
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