diff options
Diffstat (limited to 'vendor/golang.org/x/crypto/ssh/server.go')
| -rw-r--r-- | vendor/golang.org/x/crypto/ssh/server.go | 21 |
1 files changed, 20 insertions, 1 deletions
diff --git a/vendor/golang.org/x/crypto/ssh/server.go b/vendor/golang.org/x/crypto/ssh/server.go index 9e387029..b21322af 100644 --- a/vendor/golang.org/x/crypto/ssh/server.go +++ b/vendor/golang.org/x/crypto/ssh/server.go @@ -370,6 +370,25 @@ func gssExchangeToken(gssapiConfig *GSSAPIWithMICConfig, firstToken []byte, s *c return authErr, perms, nil } +// isAlgoCompatible checks if the signature format is compatible with the +// selected algorithm taking into account edge cases that occur with old +// clients. +func isAlgoCompatible(algo, sigFormat string) bool { + // Compatibility for old clients. + // + // For certificate authentication with OpenSSH 7.2-7.7 signature format can + // be rsa-sha2-256 or rsa-sha2-512 for the algorithm + // ssh-rsa-cert-v01@openssh.com. + // + // With gpg-agent < 2.2.6 the algorithm can be rsa-sha2-256 or rsa-sha2-512 + // for signature format ssh-rsa. + if isRSA(algo) && isRSA(sigFormat) { + return true + } + // Standard case: the underlying algorithm must match the signature format. + return underlyingAlgo(algo) == sigFormat +} + // ServerAuthError represents server authentication errors and is // sometimes returned by NewServerConn. It appends any authentication // errors that may occur, and is returned if all of the authentication @@ -567,7 +586,7 @@ userAuthLoop: authErr = fmt.Errorf("ssh: algorithm %q not accepted", sig.Format) break } - if underlyingAlgo(algo) != sig.Format { + if !isAlgoCompatible(algo, sig.Format) { authErr = fmt.Errorf("ssh: signature %q not compatible with selected algorithm %q", sig.Format, algo) break } |