diff options
Diffstat (limited to 'ssh/kex.go')
| -rw-r--r-- | ssh/kex.go | 73 |
1 files changed, 49 insertions, 24 deletions
@@ -19,6 +19,21 @@ import ( "golang.org/x/crypto/curve25519" ) +const ( + // This is the group called diffie-hellman-group1-sha1 in RFC 4253 and + // Oakley Group 2 in RFC 2409. + oakleyGroup2 = "FFFFFFFFFFFFFFFFC90FDAA22168C234C4C6628B80DC1CD129024E088A67CC74020BBEA63B139B22514A08798E3404DDEF9519B3CD3A431B302B0A6DF25F14374FE1356D6D51C245E485B576625E7EC6F44C42E9A637ED6B0BFF5CB6F406B7EDEE386BFB5A899FA5AE9F24117C4B1FE649286651ECE65381FFFFFFFFFFFFFFFF" + // This is the group called diffie-hellman-group14-sha1 in RFC 4253 and + // Oakley Group 14 in RFC 3526. + oakleyGroup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his is the group called diffie-hellman-group15-sha512 in RFC 8268 and + // Oakley Group 15 in RFC 3526. + oakleyGroup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his is the group called diffie-hellman-group16-sha512 in RFC 8268 and + // Oakley Group 16 in RFC 3526. + oakleyGroup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kexResult captures the outcome of a key exchange. type kexResult struct { // Session hash. See also RFC 4253, section 8. @@ -384,9 +399,7 @@ func ecHash(curve elliptic.Curve) crypto.Hash { var kexAlgoMap = map[string]kexAlgorithm{} func init() { - // This is the group called diffie-hellman-group1-sha1 in - // RFC 4253 and Oakley Group 2 in RFC 2409. - p, _ := new(big.Int).SetString("FFFFFFFFFFFFFFFFC90FDAA22168C234C4C6628B80DC1CD129024E088A67CC74020BBEA63B139B22514A08798E3404DDEF9519B3CD3A431B302B0A6DF25F14374FE1356D6D51C245E485B576625E7EC6F44C42E9A637ED6B0BFF5CB6F406B7EDEE386BFB5A899FA5AE9F24117C4B1FE649286651ECE65381FFFFFFFFFFFFFFFF", 16) + p, _ := new(big.Int).SetString(oakleyGroup2, 16) kexAlgoMap[InsecureKeyExchangeDH1SHA1] = &dhGroup{ g: new(big.Int).SetInt64(2), p: p, @@ -394,10 +407,7 @@ func init() { hashFunc: crypto.SHA1, } - // This are the groups called diffie-hellman-group14-sha1 and - // diffie-hellman-group14-sha256 in RFC 4253 and RFC 8268, - // and Oakley Group 14 in RFC 3526. - p, _ = new(big.Int).SetString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p, _ = new(big.Int).SetString(oakleyGroup14, 16) group14 := &dhGroup{ g: new(big.Int).SetInt64(2), p: p, @@ -413,9 +423,7 @@ func init() { hashFunc: crypto.SHA256, } - // This is the group called diffie-hellman-group16-sha512 in RFC - // 8268 and Oakley Group 16 in RFC 3526. - p, _ = new(big.Int).SetString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p, _ = new(big.Int).SetString(oakleyGroup16, 16) kexAlgoMap[KeyExchangeDH16SHA512] = &dhGroup{ g: new(big.Int).SetInt64(2), @@ -583,9 +591,9 @@ const ( func (gex *dhGEXSHA) Client(c packetConn, randSource io.Reader, magics *handshakeMagics) (*kexResult, error) { // Send GexRequest kexDHGexRequest := kexDHGexRequestMsg{ - MinBits: dhGroupExchangeMinimumBits, - PreferedBits: dhGroupExchangePreferredBits, - MaxBits: dhGroupExchangeMaximumBits, + MinBits: dhGroupExchangeMinimumBits, + PreferredBits: dhGroupExchangePreferredBits, + MaxBits: dhGroupExchangeMaximumBits, } if err := c.writePacket(Marshal(&kexDHGexRequest)); err != nil { return nil, err @@ -672,9 +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 AlgorithmSigner, algo string) (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 { @@ -684,13 +690,32 @@ func (gex dhGEXSHA) Server(c packetConn, randSource io.Reader, magics *handshake if err = Unmarshal(packet, &kexDHGexRequest); err != nil { return } + // We check that the request received is valid and that the MaxBits + // requested are at least equal to our supported minimum. This is the same + // check done in OpenSSH: + // https://github.com/openssh/openssh-portable/blob/80a2f64b/kexgexs.c#L94 + // + // Furthermore, we also check that the required MinBits are less than or + // equal to 4096 because we can use up to Oakley Group 16. + if kexDHGexRequest.MaxBits < kexDHGexRequest.MinBits || kexDHGexRequest.PreferredBits < kexDHGexRequest.MinBits || + kexDHGexRequest.MaxBits < kexDHGexRequest.PreferredBits || kexDHGexRequest.MaxBits < dhGroupExchangeMinimumBits || + kexDHGexRequest.MinBits > 4096 { + return nil, fmt.Errorf("ssh: DH GEX request out of range, min: %d, max: %d, preferred: %d", kexDHGexRequest.MinBits, + kexDHGexRequest.MaxBits, kexDHGexRequest.PreferredBits) + } - // Send GexGroup - // This is the group called diffie-hellman-group14-sha1 in RFC - // 4253 and Oakley Group 14 in RFC 3526. - p, _ := new(big.Int).SetString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g := big.NewInt(2) + var p *big.Int + // We hardcode sending Oakley Group 14 (2048 bits), Oakley Group 15 (3072 + // bits) or Oakley Group 16 (4096 bits), based on the requested max size. + if kexDHGexRequest.MaxBits < 3072 { + p, _ = new(big.Int).SetString(oakleyGroup14, 16) + } else if kexDHGexRequest.MaxBits < 4096 { + p, _ = new(big.Int).SetString(oakleyGroup15, 16) + } else { + p, _ = new(big.Int).SetString(oakleyGroup16, 16) + } + g := big.NewInt(2) msg := &kexDHGexGroupMsg{ P: p, G: g, @@ -728,9 +753,9 @@ func (gex dhGEXSHA) Server(c packetConn, randSource io.Reader, magics *handshake h := gex.hashFunc.New() magics.write(h) writeString(h, hostKeyBytes) - binary.Write(h, binary.BigEndian, uint32(dhGroupExchangeMinimumBits)) - binary.Write(h, binary.BigEndian, uint32(dhGroupExchangePreferredBits)) - binary.Write(h, binary.BigEndian, uint32(dhGroupExchangeMaximumBits)) + binary.Write(h, binary.BigEndian, kexDHGexRequest.MinBits) + binary.Write(h, binary.BigEndian, kexDHGexRequest.PreferredBits) + binary.Write(h, binary.BigEndian, kexDHGexRequest.MaxBits) writeInt(h, p) writeInt(h, g) writeInt(h, kexDHGexInit.X) |