diff --git a/ssh/certs.go b/ssh/certs.go index 17d4f6ed..c7a4dd0a 100644 --- a/ssh/certs.go +++ b/ssh/certs.go @@ -440,10 +440,14 @@ func (c *Certificate) SignCert(rand io.Reader, authority Signer) error { } c.SignatureKey = authority.PublicKey() - if v, ok := authority.(AlgorithmSigner); ok { - if v.PublicKey().Type() == KeyAlgoRSA { - authority = &rsaSigner{v, KeyAlgoRSASHA512} + // Default to KeyAlgoRSASHA512 for ssh-rsa signers. + if v, ok := authority.(AlgorithmSigner); ok && v.PublicKey().Type() == KeyAlgoRSA { + sig, err := v.SignWithAlgorithm(rand, c.bytesForSigning(), KeyAlgoRSASHA512) + if err != nil { + return err } + c.Signature = sig + return nil } sig, err := authority.Sign(rand, c.bytesForSigning()) @@ -454,30 +458,29 @@ func (c *Certificate) SignCert(rand io.Reader, authority Signer) error { return nil } -// certAlgoNames includes a mapping from signature algorithms to the -// corresponding certificate signature algorithm. -var certAlgoNames = map[string]string{ - KeyAlgoRSA: CertAlgoRSAv01, - KeyAlgoRSASHA256: CertAlgoRSASHA256v01, - KeyAlgoRSASHA512: CertAlgoRSASHA512v01, - KeyAlgoDSA: CertAlgoDSAv01, - KeyAlgoECDSA256: CertAlgoECDSA256v01, - KeyAlgoECDSA384: CertAlgoECDSA384v01, - KeyAlgoECDSA521: CertAlgoECDSA521v01, - KeyAlgoSKECDSA256: CertAlgoSKECDSA256v01, - KeyAlgoED25519: CertAlgoED25519v01, - KeyAlgoSKED25519: CertAlgoSKED25519v01, +// certKeyAlgoNames is a mapping from known certificate algorithm names to the +// corresponding public key signature algorithm. +var certKeyAlgoNames = map[string]string{ + CertAlgoRSAv01: KeyAlgoRSA, + CertAlgoRSASHA256v01: KeyAlgoRSASHA256, + CertAlgoRSASHA512v01: KeyAlgoRSASHA512, + CertAlgoDSAv01: KeyAlgoDSA, + CertAlgoECDSA256v01: KeyAlgoECDSA256, + CertAlgoECDSA384v01: KeyAlgoECDSA384, + CertAlgoECDSA521v01: KeyAlgoECDSA521, + CertAlgoSKECDSA256v01: KeyAlgoSKECDSA256, + CertAlgoED25519v01: KeyAlgoED25519, + CertAlgoSKED25519v01: KeyAlgoSKED25519, } -// certToPrivAlgo returns the underlying algorithm for a certificate algorithm. -// Panics if a non-certificate algorithm is passed. -func certToPrivAlgo(algo string) string { - for privAlgo, pubAlgo := range certAlgoNames { - if pubAlgo == algo { - return privAlgo - } +// underlyingAlgo returns the signature algorithm associated with algo (which is +// an advertised or negotiated public key or host key algorithm). These are +// usually the same, except for certificate algorithms. +func underlyingAlgo(algo string) string { + if a, ok := certKeyAlgoNames[algo]; ok { + return a } - panic("unknown cert algorithm") + return algo } func (cert *Certificate) bytesForSigning() []byte { @@ -523,11 +526,13 @@ func (c *Certificate) Marshal() []byte { // Type returns the certificate algorithm name. It is part of the PublicKey interface. func (c *Certificate) Type() string { - algo, ok := certAlgoNames[c.Key.Type()] - if !ok { - panic("unknown cert key type " + c.Key.Type()) + keyType := c.Key.Type() + for certName, keyName := range certKeyAlgoNames { + if keyName == keyType { + return certName + } } - return algo + panic("unknown certificate type for key type " + keyType) } // Verify verifies a signature against the certificate's public diff --git a/ssh/certs_test.go b/ssh/certs_test.go index 12c1afd5..ba6dbcac 100644 --- a/ssh/certs_test.go +++ b/ssh/certs_test.go @@ -216,12 +216,12 @@ func TestHostKeyCert(t *testing.T) { _, _, _, err = NewClientConn(c2, test.addr, config) if (err == nil) != test.succeed { - t.Fatalf("NewClientConn(%q): %v", test.addr, err) + t.Errorf("NewClientConn(%q): %v", test.addr, err) } err = <-errc if (err == nil) != test.succeed { - t.Fatalf("NewServerConn(%q): %v", test.addr, err) + t.Errorf("NewServerConn(%q): %v", test.addr, err) } } } @@ -249,9 +249,7 @@ func TestCertTypes(t *testing.T) { {CertAlgoECDSA521v01, testSigners["ecdsap521"], ""}, {CertAlgoED25519v01, testSigners["ed25519"], ""}, {CertAlgoRSAv01, testSigners["rsa"], KeyAlgoRSASHA512}, - {CertAlgoRSAv01, &legacyRSASigner{testSigners["rsa"]}, KeyAlgoRSA}, - {CertAlgoRSAv01, testSigners["rsa-sha2-256"], KeyAlgoRSASHA512}, - {CertAlgoRSAv01, testSigners["rsa-sha2-512"], KeyAlgoRSASHA512}, + {"legacyRSASigner", &legacyRSASigner{testSigners["rsa"]}, KeyAlgoRSA}, {CertAlgoDSAv01, testSigners["dsa"], ""}, } diff --git a/ssh/client.go b/ssh/client.go index 43fbe252..bdc356cb 100644 --- a/ssh/client.go +++ b/ssh/client.go @@ -113,25 +113,16 @@ func (c *connection) clientHandshake(dialAddress string, config *ClientConfig) e return c.clientAuthenticate(config) } -// verifyHostKeySignature verifies the host key obtained in the key -// exchange. +// verifyHostKeySignature verifies the host key obtained in the key exchange. +// algo is the negotiated algorithm, and may be a certificate type. func verifyHostKeySignature(hostKey PublicKey, algo string, result *kexResult) error { sig, rest, ok := parseSignatureBody(result.Signature) if len(rest) > 0 || !ok { return errors.New("ssh: signature parse error") } - // For keys, underlyingAlgo is exactly algo. For certificates, - // we have to look up the underlying key algorithm that SSH - // uses to evaluate signatures. - underlyingAlgo := algo - for sigAlgo, certAlgo := range certAlgoNames { - if certAlgo == algo { - underlyingAlgo = sigAlgo - } - } - if sig.Format != underlyingAlgo { - return fmt.Errorf("ssh: invalid signature algorithm %q, expected %q", sig.Format, underlyingAlgo) + if a := underlyingAlgo(algo); sig.Format != a { + return fmt.Errorf("ssh: invalid signature algorithm %q, expected %q", sig.Format, a) } return hostKey.Verify(result.H, sig) diff --git a/ssh/common.go b/ssh/common.go index 768641fb..d6d9bf96 100644 --- a/ssh/common.go +++ b/ssh/common.go @@ -89,23 +89,33 @@ var supportedMACs = []string{ var supportedCompressions = []string{compressionNone} -// hashFuncs keeps the mapping of supported algorithms to their respective -// hashes needed for signature verification. +// hashFuncs keeps the mapping of supported signature algorithms to their +// respective hashes needed for signing and verification. var hashFuncs = map[string]crypto.Hash{ - KeyAlgoRSA: crypto.SHA1, - KeyAlgoRSASHA256: crypto.SHA256, - KeyAlgoRSASHA512: crypto.SHA512, - KeyAlgoDSA: crypto.SHA1, - KeyAlgoECDSA256: crypto.SHA256, - KeyAlgoECDSA384: crypto.SHA384, - KeyAlgoECDSA521: crypto.SHA512, - CertAlgoRSAv01: crypto.SHA1, - CertAlgoRSASHA256v01: crypto.SHA256, - CertAlgoRSASHA512v01: crypto.SHA512, - CertAlgoDSAv01: crypto.SHA1, - CertAlgoECDSA256v01: crypto.SHA256, - CertAlgoECDSA384v01: crypto.SHA384, - CertAlgoECDSA521v01: crypto.SHA512, + KeyAlgoRSA: crypto.SHA1, + KeyAlgoRSASHA256: crypto.SHA256, + KeyAlgoRSASHA512: crypto.SHA512, + KeyAlgoDSA: crypto.SHA1, + KeyAlgoECDSA256: crypto.SHA256, + KeyAlgoECDSA384: crypto.SHA384, + KeyAlgoECDSA521: crypto.SHA512, + // KeyAlgoED25519 doesn't pre-hash. + KeyAlgoSKECDSA256: crypto.SHA256, + KeyAlgoSKED25519: crypto.SHA256, +} + +// algorithmsForKeyFormat returns the supported signature algorithms for a given +// public key format (PublicKey.Type), in order of preference. See RFC 8332, +// Section 2. See also the note in sendKexInit on backwards compatibility. +func algorithmsForKeyFormat(keyFormat string) []string { + switch keyFormat { + case KeyAlgoRSA: + return []string{KeyAlgoRSASHA256, KeyAlgoRSASHA512, KeyAlgoRSA} + case CertAlgoRSAv01: + return []string{CertAlgoRSASHA256v01, CertAlgoRSASHA512v01, CertAlgoRSAv01} + default: + return []string{keyFormat} + } } // unexpectedMessageError results when the SSH message that we received didn't diff --git a/ssh/handshake.go b/ssh/handshake.go index 5eeddb3e..4bceb331 100644 --- a/ssh/handshake.go +++ b/ssh/handshake.go @@ -455,21 +455,29 @@ func (t *handshakeTransport) sendKexInit() error { } io.ReadFull(rand.Reader, msg.Cookie[:]) - if len(t.hostKeys) > 0 { + isServer := len(t.hostKeys) > 0 + if isServer { for _, k := range t.hostKeys { - algo := k.PublicKey().Type() - switch algo { - case KeyAlgoRSA: - msg.ServerHostKeyAlgos = append(msg.ServerHostKeyAlgos, []string{KeyAlgoRSASHA512, KeyAlgoRSASHA256, KeyAlgoRSA}...) - case CertAlgoRSAv01: - msg.ServerHostKeyAlgos = append(msg.ServerHostKeyAlgos, []string{CertAlgoRSASHA512v01, CertAlgoRSASHA256v01, CertAlgoRSAv01}...) - default: - msg.ServerHostKeyAlgos = append(msg.ServerHostKeyAlgos, algo) + // If k is an AlgorithmSigner, presume it supports all signature algorithms + // associated with the key format. (Ideally AlgorithmSigner would have a + // method to advertise supported algorithms, but it doesn't. This means that + // adding support for a new algorithm is a breaking change, as we will + // immediately negotiate it even if existing implementations don't support + // it. If that ever happens, we'll have to figure something out.) + // If k is not an AlgorithmSigner, we can only assume it only supports the + // algorithms that matches the key format. (This means that Sign can't pick + // a different default.) + keyFormat := k.PublicKey().Type() + if _, ok := k.(AlgorithmSigner); ok { + msg.ServerHostKeyAlgos = append(msg.ServerHostKeyAlgos, algorithmsForKeyFormat(keyFormat)...) + } else { + msg.ServerHostKeyAlgos = append(msg.ServerHostKeyAlgos, keyFormat) } } } else { msg.ServerHostKeyAlgos = t.hostKeyAlgorithms } + packet := Marshal(msg) // writePacket destroys the contents, so save a copy. @@ -589,9 +597,9 @@ func (t *handshakeTransport) enterKeyExchange(otherInitPacket []byte) error { var result *kexResult if len(t.hostKeys) > 0 { - result, err = t.server(kex, t.algorithms, &magics) + result, err = t.server(kex, &magics) } else { - result, err = t.client(kex, t.algorithms, &magics) + result, err = t.client(kex, &magics) } if err != nil { @@ -618,33 +626,52 @@ func (t *handshakeTransport) enterKeyExchange(otherInitPacket []byte) error { return nil } -func (t *handshakeTransport) server(kex kexAlgorithm, algs *algorithms, magics *handshakeMagics) (*kexResult, error) { - var hostKey Signer - for _, k := range t.hostKeys { - kt := k.PublicKey().Type() - if kt == algs.hostKey { - hostKey = k - } else if signer, ok := k.(AlgorithmSigner); ok { - // Some signature algorithms don't show up as key types - // so we have to manually check for a compatible host key. - switch kt { - case KeyAlgoRSA: - if algs.hostKey == KeyAlgoRSASHA256 || algs.hostKey == KeyAlgoRSASHA512 { - hostKey = &rsaSigner{signer, algs.hostKey} - } - case CertAlgoRSAv01: - if algs.hostKey == CertAlgoRSASHA256v01 || algs.hostKey == CertAlgoRSASHA512v01 { - hostKey = &rsaSigner{signer, certToPrivAlgo(algs.hostKey)} - } +// algorithmSignerWrapper is an AlgorithmSigner that only supports the default +// key format algorithm. +// +// This is technically a violation of the AlgorithmSigner interface, but it +// should be unreachable given where we use this. Anyway, at least it returns an +// error instead of panicing or producing an incorrect signature. +type algorithmSignerWrapper struct { + Signer +} + +func (a algorithmSignerWrapper) SignWithAlgorithm(rand io.Reader, data []byte, algorithm string) (*Signature, error) { + if algorithm != underlyingAlgo(a.PublicKey().Type()) { + return nil, errors.New("ssh: internal error: algorithmSignerWrapper invoked with non-default algorithm") + } + return a.Sign(rand, data) +} + +func pickHostKey(hostKeys []Signer, algo string) AlgorithmSigner { + for _, k := range hostKeys { + if algo == k.PublicKey().Type() { + return algorithmSignerWrapper{k} + } + k, ok := k.(AlgorithmSigner) + if !ok { + continue + } + for _, a := range algorithmsForKeyFormat(k.PublicKey().Type()) { + if algo == a { + return k } } } + return nil +} - r, err := kex.Server(t.conn, t.config.Rand, magics, hostKey) +func (t *handshakeTransport) server(kex kexAlgorithm, magics *handshakeMagics) (*kexResult, error) { + hostKey := pickHostKey(t.hostKeys, t.algorithms.hostKey) + if hostKey == nil { + return nil, errors.New("ssh: internal error: negotiated unsupported signature type") + } + + r, err := kex.Server(t.conn, t.config.Rand, magics, hostKey, t.algorithms.hostKey) return r, err } -func (t *handshakeTransport) client(kex kexAlgorithm, algs *algorithms, magics *handshakeMagics) (*kexResult, error) { +func (t *handshakeTransport) client(kex kexAlgorithm, magics *handshakeMagics) (*kexResult, error) { result, err := kex.Client(t.conn, t.config.Rand, magics) if err != nil { return nil, err @@ -655,7 +682,7 @@ func (t *handshakeTransport) client(kex kexAlgorithm, algs *algorithms, magics * return nil, err } - if err := verifyHostKeySignature(hostKey, algs.hostKey, result); err != nil { + if err := verifyHostKeySignature(hostKey, t.algorithms.hostKey, result); err != nil { return nil, err } diff --git a/ssh/handshake_test.go b/ssh/handshake_test.go index 46bfd6dd..b05aab30 100644 --- a/ssh/handshake_test.go +++ b/ssh/handshake_test.go @@ -583,3 +583,38 @@ func TestHandshakeAEADCipherNoMAC(t *testing.T) { <-checker.called } } + +// TestNoSHA2Support tests a host key Signer that is not an AlgorithmSigner and +// therefore can't do SHA-2 signatures. Ensures the server does not advertise +// support for them in this case. +func TestNoSHA2Support(t *testing.T) { + c1, c2, err := netPipe() + if err != nil { + t.Fatalf("netPipe: %v", err) + } + defer c1.Close() + defer c2.Close() + + serverConf := &ServerConfig{ + PasswordCallback: func(conn ConnMetadata, password []byte) (*Permissions, error) { + return &Permissions{}, nil + }, + } + serverConf.AddHostKey(&legacyRSASigner{testSigners["rsa"]}) + go func() { + _, _, _, err := NewServerConn(c1, serverConf) + if err != nil { + t.Error(err) + } + }() + + clientConf := &ClientConfig{ + User: "test", + Auth: []AuthMethod{Password("testpw")}, + HostKeyCallback: FixedHostKey(testSigners["rsa"].PublicKey()), + } + + if _, _, _, err := NewClientConn(c2, "", clientConf); err != nil { + t.Fatal(err) + } +} diff --git a/ssh/kex.go b/ssh/kex.go index 94287e44..927a90cd 100644 --- a/ssh/kex.go +++ b/ssh/kex.go @@ -77,8 +77,9 @@ func (m *handshakeMagics) write(w io.Writer) { // kexAlgorithm abstracts different key exchange algorithms. type kexAlgorithm interface { // Server runs server-side key agreement, signing the result - // with a hostkey. - Server(p packetConn, rand io.Reader, magics *handshakeMagics, s Signer) (*kexResult, error) + // with a hostkey. algo is the negotiated algorithm, and may + // be a certificate type. + Server(p packetConn, rand io.Reader, magics *handshakeMagics, s AlgorithmSigner, algo string) (*kexResult, error) // Client runs the client-side key agreement. Caller is // responsible for verifying the host key signature. @@ -151,7 +152,7 @@ func (group *dhGroup) Client(c packetConn, randSource io.Reader, magics *handsha }, nil } -func (group *dhGroup) Server(c packetConn, randSource io.Reader, magics *handshakeMagics, priv Signer) (result *kexResult, err error) { +func (group *dhGroup) Server(c packetConn, randSource io.Reader, magics *handshakeMagics, priv AlgorithmSigner, algo string) (result *kexResult, err error) { packet, err := c.readPacket() if err != nil { return @@ -193,7 +194,7 @@ func (group *dhGroup) Server(c packetConn, randSource io.Reader, magics *handsha // H is already a hash, but the hostkey signing will apply its // own key-specific hash algorithm. - sig, err := signAndMarshal(priv, randSource, H) + sig, err := signAndMarshal(priv, randSource, H, algo) if err != nil { return nil, err } @@ -314,7 +315,7 @@ func validateECPublicKey(curve elliptic.Curve, x, y *big.Int) bool { return true } -func (kex *ecdh) Server(c packetConn, rand io.Reader, magics *handshakeMagics, priv Signer) (result *kexResult, err error) { +func (kex *ecdh) Server(c packetConn, rand io.Reader, magics *handshakeMagics, priv AlgorithmSigner, algo string) (result *kexResult, err error) { packet, err := c.readPacket() if err != nil { return nil, err @@ -359,7 +360,7 @@ func (kex *ecdh) Server(c packetConn, rand io.Reader, magics *handshakeMagics, p // H is already a hash, but the hostkey signing will apply its // own key-specific hash algorithm. - sig, err := signAndMarshal(priv, rand, H) + sig, err := signAndMarshal(priv, rand, H, algo) if err != nil { return nil, err } @@ -384,6 +385,19 @@ func (kex *ecdh) Server(c packetConn, rand io.Reader, magics *handshakeMagics, p }, nil } +// ecHash returns the hash to match the given elliptic curve, see RFC +// 5656, section 6.2.1 +func ecHash(curve elliptic.Curve) crypto.Hash { + bitSize := curve.Params().BitSize + switch { + case bitSize <= 256: + return crypto.SHA256 + case bitSize <= 384: + return crypto.SHA384 + } + return crypto.SHA512 +} + var kexAlgoMap = map[string]kexAlgorithm{} func init() { @@ -496,7 +510,7 @@ func (kex *curve25519sha256) Client(c packetConn, rand io.Reader, magics *handsh }, nil } -func (kex *curve25519sha256) Server(c packetConn, rand io.Reader, magics *handshakeMagics, priv Signer) (result *kexResult, err error) { +func (kex *curve25519sha256) Server(c packetConn, rand io.Reader, magics *handshakeMagics, priv AlgorithmSigner, algo string) (result *kexResult, err error) { packet, err := c.readPacket() if err != nil { return @@ -537,7 +551,7 @@ func (kex *curve25519sha256) Server(c packetConn, rand io.Reader, magics *handsh H := h.Sum(nil) - sig, err := signAndMarshal(priv, rand, H) + sig, err := signAndMarshal(priv, rand, H, algo) if err != nil { return nil, err } @@ -666,7 +680,7 @@ func (gex *dhGEXSHA) Client(c packetConn, randSource io.Reader, magics *handshak // Server half implementation of the Diffie Hellman Key Exchange with SHA1 and SHA256. // // This is a minimal implementation to satisfy the automated tests. -func (gex dhGEXSHA) Server(c packetConn, randSource io.Reader, magics *handshakeMagics, priv Signer) (result *kexResult, err error) { +func (gex dhGEXSHA) Server(c packetConn, randSource io.Reader, magics *handshakeMagics, priv AlgorithmSigner, algo string) (result *kexResult, err error) { // Receive GexRequest packet, err := c.readPacket() if err != nil { @@ -736,7 +750,7 @@ func (gex dhGEXSHA) Server(c packetConn, randSource io.Reader, magics *handshake // H is already a hash, but the hostkey signing will apply its // own key-specific hash algorithm. - sig, err := signAndMarshal(priv, randSource, H) + sig, err := signAndMarshal(priv, randSource, H, algo) if err != nil { return nil, err } diff --git a/ssh/kex_test.go b/ssh/kex_test.go index 1416b171..327013b7 100644 --- a/ssh/kex_test.go +++ b/ssh/kex_test.go @@ -41,7 +41,7 @@ func TestKexes(t *testing.T) { c <- kexResultErr{r, e} }() go func() { - r, e := kex.Server(b, rand.Reader, &magics, testSigners["ecdsa"]) + r, e := kex.Server(b, rand.Reader, &magics, testSigners["ecdsa"].(AlgorithmSigner), testSigners["ecdsa"].PublicKey().Type()) b.Close() s <- kexResultErr{r, e} }() diff --git a/ssh/keys.go b/ssh/keys.go index 17b46a49..1c7de1a6 100644 --- a/ssh/keys.go +++ b/ssh/keys.go @@ -76,7 +76,7 @@ func parsePubKey(in []byte, algo string) (pubKey PublicKey, rest []byte, err err case KeyAlgoSKED25519: return parseSKEd25519(in) case CertAlgoRSAv01, CertAlgoDSAv01, CertAlgoECDSA256v01, CertAlgoECDSA384v01, CertAlgoECDSA521v01, CertAlgoSKECDSA256v01, CertAlgoED25519v01, CertAlgoSKED25519v01: - cert, err := parseCert(in, certToPrivAlgo(algo)) + cert, err := parseCert(in, certKeyAlgoNames[algo]) if err != nil { return nil, nil, err } @@ -295,18 +295,21 @@ func MarshalAuthorizedKey(key PublicKey) []byte { return b.Bytes() } -// PublicKey is an abstraction of different types of public keys. +// PublicKey represents a public key using an unspecified algorithm. +// +// Some PublicKeys provided by this package also implement CryptoPublicKey. type PublicKey interface { - // Type returns the key's type, e.g. "ssh-rsa". + // Type returns the key format name, e.g. "ssh-rsa". Type() string - // Marshal returns the serialized key data in SSH wire format, - // with the name prefix. To unmarshal the returned data, use - // the ParsePublicKey function. + // Marshal returns the serialized key data in SSH wire format, with the name + // prefix. To unmarshal the returned data, use the ParsePublicKey function. Marshal() []byte - // Verify that sig is a signature on the given data using this - // key. This function will hash the data appropriately first. + // Verify that sig is a signature on the given data using this key. This + // method will hash the data appropriately first. sig.Format is allowed to + // be any signature algorithm compatible with the key type, the caller + // should check if it has more stringent requirements. Verify(data []byte, sig *Signature) error } @@ -317,23 +320,32 @@ type CryptoPublicKey interface { } // A Signer can create signatures that verify against a public key. +// +// Some Signers provided by this package also implement AlgorithmSigner. type Signer interface { - // PublicKey returns an associated PublicKey instance. + // PublicKey returns the associated PublicKey. PublicKey() PublicKey - // Sign returns raw signature for the given data. This method - // will apply the hash specified for the keytype to the data. + // Sign returns a signature for the given data. This method will hash the + // data appropriately first. The signature algorithm is expected to match + // the key format returned by the PublicKey.Type method (and not to be any + // alternative algorithm supported by the key format). Sign(rand io.Reader, data []byte) (*Signature, error) } -// A AlgorithmSigner is a Signer that also supports specifying a specific -// algorithm to use for signing. +// An AlgorithmSigner is a Signer that also supports specifying an algorithm to +// use for signing. +// +// An AlgorithmSigner can't advertise the algorithms it supports, so it should +// be prepared to be invoked with every algorithm supported by the public key +// format. type AlgorithmSigner interface { Signer // SignWithAlgorithm is like Signer.Sign, but allows specifying a desired // signing algorithm. Callers may pass an empty string for the algorithm in - // which case the AlgorithmSigner will use a default algorithm. + // which case the AlgorithmSigner will use a default algorithm. This default + // doesn't currently control any behavior in this package. SignWithAlgorithm(rand io.Reader, data []byte, algorithm string) (*Signature, error) } @@ -385,17 +397,11 @@ func (r *rsaPublicKey) Marshal() []byte { } func (r *rsaPublicKey) Verify(data []byte, sig *Signature) error { - var hash crypto.Hash - switch sig.Format { - case KeyAlgoRSA: - hash = crypto.SHA1 - case KeyAlgoRSASHA256: - hash = crypto.SHA256 - case KeyAlgoRSASHA512: - hash = crypto.SHA512 - default: + supportedAlgos := algorithmsForKeyFormat(r.Type()) + if !contains(supportedAlgos, sig.Format) { return fmt.Errorf("ssh: signature type %s for key type %s", sig.Format, r.Type()) } + hash := hashFuncs[sig.Format] h := hash.New() h.Write(data) digest := h.Sum(nil) @@ -470,7 +476,7 @@ func (k *dsaPublicKey) Verify(data []byte, sig *Signature) error { if sig.Format != k.Type() { return fmt.Errorf("ssh: signature type %s for key type %s", sig.Format, k.Type()) } - h := crypto.SHA1.New() + h := hashFuncs[sig.Format].New() h.Write(data) digest := h.Sum(nil) @@ -503,7 +509,7 @@ func (k *dsaPrivateKey) PublicKey() PublicKey { } func (k *dsaPrivateKey) Sign(rand io.Reader, data []byte) (*Signature, error) { - return k.SignWithAlgorithm(rand, data, "") + return k.SignWithAlgorithm(rand, data, k.PublicKey().Type()) } func (k *dsaPrivateKey) SignWithAlgorithm(rand io.Reader, data []byte, algorithm string) (*Signature, error) { @@ -511,7 +517,7 @@ func (k *dsaPrivateKey) SignWithAlgorithm(rand io.Reader, data []byte, algorithm return nil, fmt.Errorf("ssh: unsupported signature algorithm %s", algorithm) } - h := crypto.SHA1.New() + h := hashFuncs[k.PublicKey().Type()].New() h.Write(data) digest := h.Sum(nil) r, s, err := dsa.Sign(rand, k.PrivateKey, digest) @@ -607,19 +613,6 @@ func supportedEllipticCurve(curve elliptic.Curve) bool { return curve == elliptic.P256() || curve == elliptic.P384() || curve == elliptic.P521() } -// ecHash returns the hash to match the given elliptic curve, see RFC -// 5656, section 6.2.1 -func ecHash(curve elliptic.Curve) crypto.Hash { - bitSize := curve.Params().BitSize - switch { - case bitSize <= 256: - return crypto.SHA256 - case bitSize <= 384: - return crypto.SHA384 - } - return crypto.SHA512 -} - // parseECDSA parses an ECDSA key according to RFC 5656, section 3.1. func parseECDSA(in []byte) (out PublicKey, rest []byte, err error) { var w struct { @@ -675,7 +668,7 @@ func (k *ecdsaPublicKey) Verify(data []byte, sig *Signature) error { return fmt.Errorf("ssh: signature type %s for key type %s", sig.Format, k.Type()) } - h := ecHash(k.Curve).New() + h := hashFuncs[sig.Format].New() h.Write(data) digest := h.Sum(nil) @@ -779,7 +772,7 @@ func (k *skECDSAPublicKey) Verify(data []byte, sig *Signature) error { return fmt.Errorf("ssh: signature type %s for key type %s", sig.Format, k.Type()) } - h := ecHash(k.Curve).New() + h := hashFuncs[sig.Format].New() h.Write([]byte(k.application)) appDigest := h.Sum(nil) @@ -878,7 +871,7 @@ func (k *skEd25519PublicKey) Verify(data []byte, sig *Signature) error { return fmt.Errorf("invalid size %d for Ed25519 public key", l) } - h := sha256.New() + h := hashFuncs[sig.Format].New() h.Write([]byte(k.application)) appDigest := h.Sum(nil) @@ -943,15 +936,6 @@ func newDSAPrivateKey(key *dsa.PrivateKey) (Signer, error) { return &dsaPrivateKey{key}, nil } -type rsaSigner struct { - AlgorithmSigner - defaultAlgorithm string -} - -func (s *rsaSigner) Sign(rand io.Reader, data []byte) (*Signature, error) { - return s.AlgorithmSigner.SignWithAlgorithm(rand, data, s.defaultAlgorithm) -} - type wrappedSigner struct { signer crypto.Signer pubKey PublicKey @@ -974,44 +958,20 @@ func (s *wrappedSigner) PublicKey() PublicKey { } func (s *wrappedSigner) Sign(rand io.Reader, data []byte) (*Signature, error) { - return s.SignWithAlgorithm(rand, data, "") + return s.SignWithAlgorithm(rand, data, s.pubKey.Type()) } func (s *wrappedSigner) SignWithAlgorithm(rand io.Reader, data []byte, algorithm string) (*Signature, error) { - var hashFunc crypto.Hash - - if _, ok := s.pubKey.(*rsaPublicKey); ok { - // RSA keys support a few hash functions determined by the requested signature algorithm - switch algorithm { - case "", KeyAlgoRSA: - algorithm = KeyAlgoRSA - hashFunc = crypto.SHA1 - case KeyAlgoRSASHA256: - hashFunc = crypto.SHA256 - case KeyAlgoRSASHA512: - hashFunc = crypto.SHA512 - default: - return nil, fmt.Errorf("ssh: unsupported signature algorithm %s", algorithm) - } - } else { - // The only supported algorithm for all other key types is the same as the type of the key - if algorithm == "" { - algorithm = s.pubKey.Type() - } else if algorithm != s.pubKey.Type() { - return nil, fmt.Errorf("ssh: unsupported signature algorithm %s", algorithm) - } - - switch key := s.pubKey.(type) { - case *dsaPublicKey: - hashFunc = crypto.SHA1 - case *ecdsaPublicKey: - hashFunc = ecHash(key.Curve) - case ed25519PublicKey: - default: - return nil, fmt.Errorf("ssh: unsupported key type %T", key) - } + if algorithm == "" { + algorithm = s.pubKey.Type() } + supportedAlgos := algorithmsForKeyFormat(s.pubKey.Type()) + if !contains(supportedAlgos, algorithm) { + return nil, fmt.Errorf("ssh: unsupported signature algorithm %q for key format %q", algorithm, s.pubKey.Type()) + } + + hashFunc := hashFuncs[algorithm] var digest []byte if hashFunc != 0 { h := hashFunc.New() diff --git a/ssh/server.go b/ssh/server.go index e70c5925..d28e1ad4 100644 --- a/ssh/server.go +++ b/ssh/server.go @@ -212,9 +212,10 @@ func NewServerConn(c net.Conn, config *ServerConfig) (*ServerConn, <-chan NewCha } // signAndMarshal signs the data with the appropriate algorithm, -// and serializes the result in SSH wire format. -func signAndMarshal(k Signer, rand io.Reader, data []byte) ([]byte, error) { - sig, err := k.Sign(rand, data) +// and serializes the result in SSH wire format. algo is the negotiate +// algorithm and may be a certificate type. +func signAndMarshal(k AlgorithmSigner, rand io.Reader, data []byte, algo string) ([]byte, error) { + sig, err := k.SignWithAlgorithm(rand, data, underlyingAlgo(algo)) if err != nil { return nil, err } diff --git a/ssh/testdata/keys.go b/ssh/testdata/keys.go index 4f2f3a4a..ad95a819 100644 --- a/ssh/testdata/keys.go +++ b/ssh/testdata/keys.go @@ -60,38 +60,6 @@ NDvRS0rjwt6lJGv7zPZoqDc65VfrK2aNyHx2PgFyzwrEOtuF57bu7pnvEIxpLTeM z26i6XVMeYXAWZMTloMCQBbpGgEERQpeUknLBqUHhg/wXF6+lFA+vEGnkY+Dwab2 KCXFGd+SQ5GdUcEMe9isUH6DYj/6/yCDoFrXXmpQb+M= -----END RSA PRIVATE KEY----- -`), - "rsa-sha2-256": []byte(`-----BEGIN RSA PRIVATE KEY----- -MIICXAIBAAKBgQC8A6FGHDiWCSREAXCq6yBfNVr0xCVG2CzvktFNRpue+RXrGs/2 -a6ySEJQb3IYquw7HlJgu6fg3WIWhOmHCjfpG0PrL4CRwbqQ2LaPPXhJErWYejcD8 -Di00cF3677+G10KMZk9RXbmHtuBFZT98wxg8j+ZsBMqGM1+7yrWUvynswQIDAQAB -AoGAJMCk5vqfSRzyXOTXLGIYCuR4Kj6pdsbNSeuuRGfYBeR1F2c/XdFAg7D/8s5R -38p/Ih52/Ty5S8BfJtwtvgVY9ecf/JlU/rl/QzhG8/8KC0NG7KsyXklbQ7gJT8UT -Ojmw5QpMk+rKv17ipDVkQQmPaj+gJXYNAHqImke5mm/K/h0CQQDciPmviQ+DOhOq -2ZBqUfH8oXHgFmp7/6pXw80DpMIxgV3CwkxxIVx6a8lVH9bT/AFySJ6vXq4zTuV9 -6QmZcZzDAkEA2j/UXJPIs1fQ8z/6sONOkU/BjtoePFIWJlRxdN35cZjXnBraX5UR -fFHkePv4YwqmXNqrBOvSu+w2WdSDci+IKwJAcsPRc/jWmsrJW1q3Ha0hSf/WG/Bu -X7MPuXaKpP/DkzGoUmb8ks7yqj6XWnYkPNLjCc8izU5vRwIiyWBRf4mxMwJBAILa -NDvRS0rjwt6lJGv7zPZoqDc65VfrK2aNyHx2PgFyzwrEOtuF57bu7pnvEIxpLTeM -z26i6XVMeYXAWZMTloMCQBbpGgEERQpeUknLBqUHhg/wXF6+lFA+vEGnkY+Dwab2 -KCXFGd+SQ5GdUcEMe9isUH6DYj/6/yCDoFrXXmpQb+M= ------END RSA PRIVATE KEY----- -`), - "rsa-sha2-512": []byte(`-----BEGIN RSA PRIVATE KEY----- -MIICXAIBAAKBgQC8A6FGHDiWCSREAXCq6yBfNVr0xCVG2CzvktFNRpue+RXrGs/2 -a6ySEJQb3IYquw7HlJgu6fg3WIWhOmHCjfpG0PrL4CRwbqQ2LaPPXhJErWYejcD8 -Di00cF3677+G10KMZk9RXbmHtuBFZT98wxg8j+ZsBMqGM1+7yrWUvynswQIDAQAB -AoGAJMCk5vqfSRzyXOTXLGIYCuR4Kj6pdsbNSeuuRGfYBeR1F2c/XdFAg7D/8s5R -38p/Ih52/Ty5S8BfJtwtvgVY9ecf/JlU/rl/QzhG8/8KC0NG7KsyXklbQ7gJT8UT -Ojmw5QpMk+rKv17ipDVkQQmPaj+gJXYNAHqImke5mm/K/h0CQQDciPmviQ+DOhOq -2ZBqUfH8oXHgFmp7/6pXw80DpMIxgV3CwkxxIVx6a8lVH9bT/AFySJ6vXq4zTuV9 -6QmZcZzDAkEA2j/UXJPIs1fQ8z/6sONOkU/BjtoePFIWJlRxdN35cZjXnBraX5UR -fFHkePv4YwqmXNqrBOvSu+w2WdSDci+IKwJAcsPRc/jWmsrJW1q3Ha0hSf/WG/Bu -X7MPuXaKpP/DkzGoUmb8ks7yqj6XWnYkPNLjCc8izU5vRwIiyWBRf4mxMwJBAILa -NDvRS0rjwt6lJGv7zPZoqDc65VfrK2aNyHx2PgFyzwrEOtuF57bu7pnvEIxpLTeM -z26i6XVMeYXAWZMTloMCQBbpGgEERQpeUknLBqUHhg/wXF6+lFA+vEGnkY+Dwab2 -KCXFGd+SQ5GdUcEMe9isUH6DYj/6/yCDoFrXXmpQb+M= ------END RSA PRIVATE KEY----- `), "pkcs8": []byte(`-----BEGIN PRIVATE KEY----- MIIEvgIBADANBgkqhkiG9w0BAQEFAASCBKgwggSkAgEAAoIBAQCitzS2KiRQTccf @@ -226,7 +194,7 @@ var SSHCertificates = map[string][]byte{ `), "rsa-sha2-256": []byte(`ssh-rsa-cert-v01@openssh.com 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 host.example.com `), - "rsa-sha2-512": []byte(`ssh-rsa-cert-v01@openssh.com AAAAHHNzaC1yc2EtY2VydC12MDFAb3BlbnNzaC5jb20AAAAgFGv4IpXfs4L/Y0b3rmUdPFhWoUrVnXuPxXr6aHGs7wgAAAADAQABAAAAgQC8A6FGHDiWCSREAXCq6yBfNVr0xCVG2CzvktFNRpue+RXrGs/2a6ySEJQb3IYquw7HlJgu6fg3WIWhOmHCjfpG0PrL4CRwbqQ2LaPPXhJErWYejcD8Di00cF3677+G10KMZk9RXbmHtuBFZT98wxg8j+ZsBMqGM1+7yrWUvynswQAAAAAAAAAAAAAAAgAAABRob3N0LmV4YW1wbGUuY29tLWtleQAAABQAAAAQaG9zdC5leGFtcGxlLmNvbQAAAABeSMRYAAAAAHBPBp4AAAAAAAAAAAAAAAAAAAEXAAAAB3NzaC1yc2EAAAADAQABAAABAQC+D11D0hEbn2Vglv4YRJ8pZNyHjIGmvth3DWOQrq++2vH2MujmGQDxfr4SVE9GpMBlKU3lwGbpgIBxAg6yZcNSfo6PWVU9ACg6NMFO+yMzc2MaG+/naQdNjSewywF5j2rkNO2XOaViRVSrZroe2B/aY2LTV0jDl8nu5NOjwRs1/s7SLe5z1rw/X0dpmXk0qJY3gQhmR8HZZ1dhEkJUGwaBCPd0T8asSYf1Ag2rUD4aQ28r3q69mbwfWOOa6rMemVZruUV5dzHwVNVNtVv+ImtnYtz8m8g+K0plaGptHn3KsaOnASkh3tujhaE7kvc4HR9Igli9+76jhZie3h/dTN5zAAABFAAAAAxyc2Etc2hhMi01MTIAAAEAnF4fVj6mm+UFeNCIf9AKJCv9WzymjjPvzzmaMWWkPWqoV0P0m5SiYfvbY9SbA73Blpv8SOr0DmpublF183kodREia4KyVuC8hLhSCV2Y16hy9MBegOZMepn80w+apj7Rn9QCz5OfEakDdztp6OWTBtqxnZFcTQ4XrgFkNWeWRElGdEvAVNn2WHwHi4EIdz0mdv48Imv5SPlOuW862ZdFG4Do1dUfDIiGsBofLlgcyIYlf+eNHul6sBeUkuwFxisMpI5DQzNp8PX1g/QJA2wzwT674PTqDXNttKjyh50Fdr4sXxm9Gz1+jVLoESvFNa55ERdSyAqNu4wTy11MZsWwSA== host.example.com + "rsa-sha2-512": []byte(`ssh-rsa-cert-v01@openssh.com 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 host.example.com `), } diff --git a/ssh/testdata_test.go b/ssh/testdata_test.go index 26fe248d..2da8c79d 100644 --- a/ssh/testdata_test.go +++ b/ssh/testdata_test.go @@ -34,14 +34,6 @@ func init() { panic(fmt.Sprintf("Unable to parse test key %s: %v", t, err)) } testSigners[t], err = NewSignerFromKey(testPrivateKeys[t]) - if v, ok := testSigners[t].(*rsaSigner); ok { - switch t { - case "rsa-sha2-256": - testSigners[t] = &rsaSigner{v, KeyAlgoRSASHA256} - case "rsa-sha2-512": - testSigners[t] = &rsaSigner{v, KeyAlgoRSASHA512} - } - } if err != nil { panic(fmt.Sprintf("Unable to create signer for test key %s: %v", t, err)) }