mirror of
https://github.com/cwinfo/matterbridge.git
synced 2024-11-30 06:11:36 +00:00
783 lines
21 KiB
Go
783 lines
21 KiB
Go
// Copyright 2013 The Go Authors. All rights reserved.
|
|
// Use of this source code is governed by a BSD-style
|
|
// license that can be found in the LICENSE file.
|
|
|
|
package ssh
|
|
|
|
import (
|
|
"crypto"
|
|
"crypto/ecdsa"
|
|
"crypto/elliptic"
|
|
"crypto/rand"
|
|
"crypto/subtle"
|
|
"encoding/binary"
|
|
"errors"
|
|
"fmt"
|
|
"io"
|
|
"math/big"
|
|
|
|
"golang.org/x/crypto/curve25519"
|
|
)
|
|
|
|
const (
|
|
kexAlgoDH1SHA1 = "diffie-hellman-group1-sha1"
|
|
kexAlgoDH14SHA1 = "diffie-hellman-group14-sha1"
|
|
kexAlgoECDH256 = "ecdh-sha2-nistp256"
|
|
kexAlgoECDH384 = "ecdh-sha2-nistp384"
|
|
kexAlgoECDH521 = "ecdh-sha2-nistp521"
|
|
kexAlgoCurve25519SHA256 = "curve25519-sha256@libssh.org"
|
|
|
|
// For the following kex only the client half contains a production
|
|
// ready implementation. The server half only consists of a minimal
|
|
// implementation to satisfy the automated tests.
|
|
kexAlgoDHGEXSHA1 = "diffie-hellman-group-exchange-sha1"
|
|
kexAlgoDHGEXSHA256 = "diffie-hellman-group-exchange-sha256"
|
|
)
|
|
|
|
// kexResult captures the outcome of a key exchange.
|
|
type kexResult struct {
|
|
// Session hash. See also RFC 4253, section 8.
|
|
H []byte
|
|
|
|
// Shared secret. See also RFC 4253, section 8.
|
|
K []byte
|
|
|
|
// Host key as hashed into H.
|
|
HostKey []byte
|
|
|
|
// Signature of H.
|
|
Signature []byte
|
|
|
|
// A cryptographic hash function that matches the security
|
|
// level of the key exchange algorithm. It is used for
|
|
// calculating H, and for deriving keys from H and K.
|
|
Hash crypto.Hash
|
|
|
|
// The session ID, which is the first H computed. This is used
|
|
// to derive key material inside the transport.
|
|
SessionID []byte
|
|
}
|
|
|
|
// handshakeMagics contains data that is always included in the
|
|
// session hash.
|
|
type handshakeMagics struct {
|
|
clientVersion, serverVersion []byte
|
|
clientKexInit, serverKexInit []byte
|
|
}
|
|
|
|
func (m *handshakeMagics) write(w io.Writer) {
|
|
writeString(w, m.clientVersion)
|
|
writeString(w, m.serverVersion)
|
|
writeString(w, m.clientKexInit)
|
|
writeString(w, m.serverKexInit)
|
|
}
|
|
|
|
// 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)
|
|
|
|
// Client runs the client-side key agreement. Caller is
|
|
// responsible for verifying the host key signature.
|
|
Client(p packetConn, rand io.Reader, magics *handshakeMagics) (*kexResult, error)
|
|
}
|
|
|
|
// dhGroup is a multiplicative group suitable for implementing Diffie-Hellman key agreement.
|
|
type dhGroup struct {
|
|
g, p, pMinus1 *big.Int
|
|
}
|
|
|
|
func (group *dhGroup) diffieHellman(theirPublic, myPrivate *big.Int) (*big.Int, error) {
|
|
if theirPublic.Cmp(bigOne) <= 0 || theirPublic.Cmp(group.pMinus1) >= 0 {
|
|
return nil, errors.New("ssh: DH parameter out of bounds")
|
|
}
|
|
return new(big.Int).Exp(theirPublic, myPrivate, group.p), nil
|
|
}
|
|
|
|
func (group *dhGroup) Client(c packetConn, randSource io.Reader, magics *handshakeMagics) (*kexResult, error) {
|
|
hashFunc := crypto.SHA1
|
|
|
|
var x *big.Int
|
|
for {
|
|
var err error
|
|
if x, err = rand.Int(randSource, group.pMinus1); err != nil {
|
|
return nil, err
|
|
}
|
|
if x.Sign() > 0 {
|
|
break
|
|
}
|
|
}
|
|
|
|
X := new(big.Int).Exp(group.g, x, group.p)
|
|
kexDHInit := kexDHInitMsg{
|
|
X: X,
|
|
}
|
|
if err := c.writePacket(Marshal(&kexDHInit)); err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
packet, err := c.readPacket()
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
var kexDHReply kexDHReplyMsg
|
|
if err = Unmarshal(packet, &kexDHReply); err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
ki, err := group.diffieHellman(kexDHReply.Y, x)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
h := hashFunc.New()
|
|
magics.write(h)
|
|
writeString(h, kexDHReply.HostKey)
|
|
writeInt(h, X)
|
|
writeInt(h, kexDHReply.Y)
|
|
K := make([]byte, intLength(ki))
|
|
marshalInt(K, ki)
|
|
h.Write(K)
|
|
|
|
return &kexResult{
|
|
H: h.Sum(nil),
|
|
K: K,
|
|
HostKey: kexDHReply.HostKey,
|
|
Signature: kexDHReply.Signature,
|
|
Hash: crypto.SHA1,
|
|
}, nil
|
|
}
|
|
|
|
func (group *dhGroup) Server(c packetConn, randSource io.Reader, magics *handshakeMagics, priv Signer) (result *kexResult, err error) {
|
|
hashFunc := crypto.SHA1
|
|
packet, err := c.readPacket()
|
|
if err != nil {
|
|
return
|
|
}
|
|
var kexDHInit kexDHInitMsg
|
|
if err = Unmarshal(packet, &kexDHInit); err != nil {
|
|
return
|
|
}
|
|
|
|
var y *big.Int
|
|
for {
|
|
if y, err = rand.Int(randSource, group.pMinus1); err != nil {
|
|
return
|
|
}
|
|
if y.Sign() > 0 {
|
|
break
|
|
}
|
|
}
|
|
|
|
Y := new(big.Int).Exp(group.g, y, group.p)
|
|
ki, err := group.diffieHellman(kexDHInit.X, y)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
hostKeyBytes := priv.PublicKey().Marshal()
|
|
|
|
h := hashFunc.New()
|
|
magics.write(h)
|
|
writeString(h, hostKeyBytes)
|
|
writeInt(h, kexDHInit.X)
|
|
writeInt(h, Y)
|
|
|
|
K := make([]byte, intLength(ki))
|
|
marshalInt(K, ki)
|
|
h.Write(K)
|
|
|
|
H := h.Sum(nil)
|
|
|
|
// H is already a hash, but the hostkey signing will apply its
|
|
// own key-specific hash algorithm.
|
|
sig, err := signAndMarshal(priv, randSource, H)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
kexDHReply := kexDHReplyMsg{
|
|
HostKey: hostKeyBytes,
|
|
Y: Y,
|
|
Signature: sig,
|
|
}
|
|
packet = Marshal(&kexDHReply)
|
|
|
|
err = c.writePacket(packet)
|
|
return &kexResult{
|
|
H: H,
|
|
K: K,
|
|
HostKey: hostKeyBytes,
|
|
Signature: sig,
|
|
Hash: crypto.SHA1,
|
|
}, err
|
|
}
|
|
|
|
// ecdh performs Elliptic Curve Diffie-Hellman key exchange as
|
|
// described in RFC 5656, section 4.
|
|
type ecdh struct {
|
|
curve elliptic.Curve
|
|
}
|
|
|
|
func (kex *ecdh) Client(c packetConn, rand io.Reader, magics *handshakeMagics) (*kexResult, error) {
|
|
ephKey, err := ecdsa.GenerateKey(kex.curve, rand)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
kexInit := kexECDHInitMsg{
|
|
ClientPubKey: elliptic.Marshal(kex.curve, ephKey.PublicKey.X, ephKey.PublicKey.Y),
|
|
}
|
|
|
|
serialized := Marshal(&kexInit)
|
|
if err := c.writePacket(serialized); err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
packet, err := c.readPacket()
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
var reply kexECDHReplyMsg
|
|
if err = Unmarshal(packet, &reply); err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
x, y, err := unmarshalECKey(kex.curve, reply.EphemeralPubKey)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
// generate shared secret
|
|
secret, _ := kex.curve.ScalarMult(x, y, ephKey.D.Bytes())
|
|
|
|
h := ecHash(kex.curve).New()
|
|
magics.write(h)
|
|
writeString(h, reply.HostKey)
|
|
writeString(h, kexInit.ClientPubKey)
|
|
writeString(h, reply.EphemeralPubKey)
|
|
K := make([]byte, intLength(secret))
|
|
marshalInt(K, secret)
|
|
h.Write(K)
|
|
|
|
return &kexResult{
|
|
H: h.Sum(nil),
|
|
K: K,
|
|
HostKey: reply.HostKey,
|
|
Signature: reply.Signature,
|
|
Hash: ecHash(kex.curve),
|
|
}, nil
|
|
}
|
|
|
|
// unmarshalECKey parses and checks an EC key.
|
|
func unmarshalECKey(curve elliptic.Curve, pubkey []byte) (x, y *big.Int, err error) {
|
|
x, y = elliptic.Unmarshal(curve, pubkey)
|
|
if x == nil {
|
|
return nil, nil, errors.New("ssh: elliptic.Unmarshal failure")
|
|
}
|
|
if !validateECPublicKey(curve, x, y) {
|
|
return nil, nil, errors.New("ssh: public key not on curve")
|
|
}
|
|
return x, y, nil
|
|
}
|
|
|
|
// validateECPublicKey checks that the point is a valid public key for
|
|
// the given curve. See [SEC1], 3.2.2
|
|
func validateECPublicKey(curve elliptic.Curve, x, y *big.Int) bool {
|
|
if x.Sign() == 0 && y.Sign() == 0 {
|
|
return false
|
|
}
|
|
|
|
if x.Cmp(curve.Params().P) >= 0 {
|
|
return false
|
|
}
|
|
|
|
if y.Cmp(curve.Params().P) >= 0 {
|
|
return false
|
|
}
|
|
|
|
if !curve.IsOnCurve(x, y) {
|
|
return false
|
|
}
|
|
|
|
// We don't check if N * PubKey == 0, since
|
|
//
|
|
// - the NIST curves have cofactor = 1, so this is implicit.
|
|
// (We don't foresee an implementation that supports non NIST
|
|
// curves)
|
|
//
|
|
// - for ephemeral keys, we don't need to worry about small
|
|
// subgroup attacks.
|
|
return true
|
|
}
|
|
|
|
func (kex *ecdh) Server(c packetConn, rand io.Reader, magics *handshakeMagics, priv Signer) (result *kexResult, err error) {
|
|
packet, err := c.readPacket()
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
var kexECDHInit kexECDHInitMsg
|
|
if err = Unmarshal(packet, &kexECDHInit); err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
clientX, clientY, err := unmarshalECKey(kex.curve, kexECDHInit.ClientPubKey)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
// We could cache this key across multiple users/multiple
|
|
// connection attempts, but the benefit is small. OpenSSH
|
|
// generates a new key for each incoming connection.
|
|
ephKey, err := ecdsa.GenerateKey(kex.curve, rand)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
hostKeyBytes := priv.PublicKey().Marshal()
|
|
|
|
serializedEphKey := elliptic.Marshal(kex.curve, ephKey.PublicKey.X, ephKey.PublicKey.Y)
|
|
|
|
// generate shared secret
|
|
secret, _ := kex.curve.ScalarMult(clientX, clientY, ephKey.D.Bytes())
|
|
|
|
h := ecHash(kex.curve).New()
|
|
magics.write(h)
|
|
writeString(h, hostKeyBytes)
|
|
writeString(h, kexECDHInit.ClientPubKey)
|
|
writeString(h, serializedEphKey)
|
|
|
|
K := make([]byte, intLength(secret))
|
|
marshalInt(K, secret)
|
|
h.Write(K)
|
|
|
|
H := h.Sum(nil)
|
|
|
|
// H is already a hash, but the hostkey signing will apply its
|
|
// own key-specific hash algorithm.
|
|
sig, err := signAndMarshal(priv, rand, H)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
reply := kexECDHReplyMsg{
|
|
EphemeralPubKey: serializedEphKey,
|
|
HostKey: hostKeyBytes,
|
|
Signature: sig,
|
|
}
|
|
|
|
serialized := Marshal(&reply)
|
|
if err := c.writePacket(serialized); err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
return &kexResult{
|
|
H: H,
|
|
K: K,
|
|
HostKey: reply.HostKey,
|
|
Signature: sig,
|
|
Hash: ecHash(kex.curve),
|
|
}, nil
|
|
}
|
|
|
|
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)
|
|
kexAlgoMap[kexAlgoDH1SHA1] = &dhGroup{
|
|
g: new(big.Int).SetInt64(2),
|
|
p: p,
|
|
pMinus1: new(big.Int).Sub(p, bigOne),
|
|
}
|
|
|
|
// 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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
|
|
|
|
kexAlgoMap[kexAlgoDH14SHA1] = &dhGroup{
|
|
g: new(big.Int).SetInt64(2),
|
|
p: p,
|
|
pMinus1: new(big.Int).Sub(p, bigOne),
|
|
}
|
|
|
|
kexAlgoMap[kexAlgoECDH521] = &ecdh{elliptic.P521()}
|
|
kexAlgoMap[kexAlgoECDH384] = &ecdh{elliptic.P384()}
|
|
kexAlgoMap[kexAlgoECDH256] = &ecdh{elliptic.P256()}
|
|
kexAlgoMap[kexAlgoCurve25519SHA256] = &curve25519sha256{}
|
|
kexAlgoMap[kexAlgoDHGEXSHA1] = &dhGEXSHA{hashFunc: crypto.SHA1}
|
|
kexAlgoMap[kexAlgoDHGEXSHA256] = &dhGEXSHA{hashFunc: crypto.SHA256}
|
|
}
|
|
|
|
// curve25519sha256 implements the curve25519-sha256@libssh.org key
|
|
// agreement protocol, as described in
|
|
// https://git.libssh.org/projects/libssh.git/tree/doc/curve25519-sha256@libssh.org.txt
|
|
type curve25519sha256 struct{}
|
|
|
|
type curve25519KeyPair struct {
|
|
priv [32]byte
|
|
pub [32]byte
|
|
}
|
|
|
|
func (kp *curve25519KeyPair) generate(rand io.Reader) error {
|
|
if _, err := io.ReadFull(rand, kp.priv[:]); err != nil {
|
|
return err
|
|
}
|
|
curve25519.ScalarBaseMult(&kp.pub, &kp.priv)
|
|
return nil
|
|
}
|
|
|
|
// curve25519Zeros is just an array of 32 zero bytes so that we have something
|
|
// convenient to compare against in order to reject curve25519 points with the
|
|
// wrong order.
|
|
var curve25519Zeros [32]byte
|
|
|
|
func (kex *curve25519sha256) Client(c packetConn, rand io.Reader, magics *handshakeMagics) (*kexResult, error) {
|
|
var kp curve25519KeyPair
|
|
if err := kp.generate(rand); err != nil {
|
|
return nil, err
|
|
}
|
|
if err := c.writePacket(Marshal(&kexECDHInitMsg{kp.pub[:]})); err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
packet, err := c.readPacket()
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
var reply kexECDHReplyMsg
|
|
if err = Unmarshal(packet, &reply); err != nil {
|
|
return nil, err
|
|
}
|
|
if len(reply.EphemeralPubKey) != 32 {
|
|
return nil, errors.New("ssh: peer's curve25519 public value has wrong length")
|
|
}
|
|
|
|
var servPub, secret [32]byte
|
|
copy(servPub[:], reply.EphemeralPubKey)
|
|
curve25519.ScalarMult(&secret, &kp.priv, &servPub)
|
|
if subtle.ConstantTimeCompare(secret[:], curve25519Zeros[:]) == 1 {
|
|
return nil, errors.New("ssh: peer's curve25519 public value has wrong order")
|
|
}
|
|
|
|
h := crypto.SHA256.New()
|
|
magics.write(h)
|
|
writeString(h, reply.HostKey)
|
|
writeString(h, kp.pub[:])
|
|
writeString(h, reply.EphemeralPubKey)
|
|
|
|
ki := new(big.Int).SetBytes(secret[:])
|
|
K := make([]byte, intLength(ki))
|
|
marshalInt(K, ki)
|
|
h.Write(K)
|
|
|
|
return &kexResult{
|
|
H: h.Sum(nil),
|
|
K: K,
|
|
HostKey: reply.HostKey,
|
|
Signature: reply.Signature,
|
|
Hash: crypto.SHA256,
|
|
}, nil
|
|
}
|
|
|
|
func (kex *curve25519sha256) Server(c packetConn, rand io.Reader, magics *handshakeMagics, priv Signer) (result *kexResult, err error) {
|
|
packet, err := c.readPacket()
|
|
if err != nil {
|
|
return
|
|
}
|
|
var kexInit kexECDHInitMsg
|
|
if err = Unmarshal(packet, &kexInit); err != nil {
|
|
return
|
|
}
|
|
|
|
if len(kexInit.ClientPubKey) != 32 {
|
|
return nil, errors.New("ssh: peer's curve25519 public value has wrong length")
|
|
}
|
|
|
|
var kp curve25519KeyPair
|
|
if err := kp.generate(rand); err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
var clientPub, secret [32]byte
|
|
copy(clientPub[:], kexInit.ClientPubKey)
|
|
curve25519.ScalarMult(&secret, &kp.priv, &clientPub)
|
|
if subtle.ConstantTimeCompare(secret[:], curve25519Zeros[:]) == 1 {
|
|
return nil, errors.New("ssh: peer's curve25519 public value has wrong order")
|
|
}
|
|
|
|
hostKeyBytes := priv.PublicKey().Marshal()
|
|
|
|
h := crypto.SHA256.New()
|
|
magics.write(h)
|
|
writeString(h, hostKeyBytes)
|
|
writeString(h, kexInit.ClientPubKey)
|
|
writeString(h, kp.pub[:])
|
|
|
|
ki := new(big.Int).SetBytes(secret[:])
|
|
K := make([]byte, intLength(ki))
|
|
marshalInt(K, ki)
|
|
h.Write(K)
|
|
|
|
H := h.Sum(nil)
|
|
|
|
sig, err := signAndMarshal(priv, rand, H)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
reply := kexECDHReplyMsg{
|
|
EphemeralPubKey: kp.pub[:],
|
|
HostKey: hostKeyBytes,
|
|
Signature: sig,
|
|
}
|
|
if err := c.writePacket(Marshal(&reply)); err != nil {
|
|
return nil, err
|
|
}
|
|
return &kexResult{
|
|
H: H,
|
|
K: K,
|
|
HostKey: hostKeyBytes,
|
|
Signature: sig,
|
|
Hash: crypto.SHA256,
|
|
}, nil
|
|
}
|
|
|
|
// dhGEXSHA implements the diffie-hellman-group-exchange-sha1 and
|
|
// diffie-hellman-group-exchange-sha256 key agreement protocols,
|
|
// as described in RFC 4419
|
|
type dhGEXSHA struct {
|
|
g, p *big.Int
|
|
hashFunc crypto.Hash
|
|
}
|
|
|
|
const (
|
|
dhGroupExchangeMinimumBits = 2048
|
|
dhGroupExchangePreferredBits = 2048
|
|
dhGroupExchangeMaximumBits = 8192
|
|
)
|
|
|
|
func (gex *dhGEXSHA) diffieHellman(theirPublic, myPrivate *big.Int) (*big.Int, error) {
|
|
if theirPublic.Sign() <= 0 || theirPublic.Cmp(gex.p) >= 0 {
|
|
return nil, fmt.Errorf("ssh: DH parameter out of bounds")
|
|
}
|
|
return new(big.Int).Exp(theirPublic, myPrivate, gex.p), nil
|
|
}
|
|
|
|
func (gex dhGEXSHA) Client(c packetConn, randSource io.Reader, magics *handshakeMagics) (*kexResult, error) {
|
|
// Send GexRequest
|
|
kexDHGexRequest := kexDHGexRequestMsg{
|
|
MinBits: dhGroupExchangeMinimumBits,
|
|
PreferedBits: dhGroupExchangePreferredBits,
|
|
MaxBits: dhGroupExchangeMaximumBits,
|
|
}
|
|
if err := c.writePacket(Marshal(&kexDHGexRequest)); err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
// Receive GexGroup
|
|
packet, err := c.readPacket()
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
var kexDHGexGroup kexDHGexGroupMsg
|
|
if err = Unmarshal(packet, &kexDHGexGroup); err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
// reject if p's bit length < dhGroupExchangeMinimumBits or > dhGroupExchangeMaximumBits
|
|
if kexDHGexGroup.P.BitLen() < dhGroupExchangeMinimumBits || kexDHGexGroup.P.BitLen() > dhGroupExchangeMaximumBits {
|
|
return nil, fmt.Errorf("ssh: server-generated gex p is out of range (%d bits)", kexDHGexGroup.P.BitLen())
|
|
}
|
|
|
|
gex.p = kexDHGexGroup.P
|
|
gex.g = kexDHGexGroup.G
|
|
|
|
// Check if g is safe by verifing that g > 1 and g < p - 1
|
|
one := big.NewInt(1)
|
|
var pMinusOne = &big.Int{}
|
|
pMinusOne.Sub(gex.p, one)
|
|
if gex.g.Cmp(one) != 1 && gex.g.Cmp(pMinusOne) != -1 {
|
|
return nil, fmt.Errorf("ssh: server provided gex g is not safe")
|
|
}
|
|
|
|
// Send GexInit
|
|
var pHalf = &big.Int{}
|
|
pHalf.Rsh(gex.p, 1)
|
|
x, err := rand.Int(randSource, pHalf)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
X := new(big.Int).Exp(gex.g, x, gex.p)
|
|
kexDHGexInit := kexDHGexInitMsg{
|
|
X: X,
|
|
}
|
|
if err := c.writePacket(Marshal(&kexDHGexInit)); err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
// Receive GexReply
|
|
packet, err = c.readPacket()
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
var kexDHGexReply kexDHGexReplyMsg
|
|
if err = Unmarshal(packet, &kexDHGexReply); err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
kInt, err := gex.diffieHellman(kexDHGexReply.Y, x)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
// Check if k is safe by verifing that k > 1 and k < p - 1
|
|
if kInt.Cmp(one) != 1 && kInt.Cmp(pMinusOne) != -1 {
|
|
return nil, fmt.Errorf("ssh: derived k is not safe")
|
|
}
|
|
|
|
h := gex.hashFunc.New()
|
|
magics.write(h)
|
|
writeString(h, kexDHGexReply.HostKey)
|
|
binary.Write(h, binary.BigEndian, uint32(dhGroupExchangeMinimumBits))
|
|
binary.Write(h, binary.BigEndian, uint32(dhGroupExchangePreferredBits))
|
|
binary.Write(h, binary.BigEndian, uint32(dhGroupExchangeMaximumBits))
|
|
writeInt(h, gex.p)
|
|
writeInt(h, gex.g)
|
|
writeInt(h, X)
|
|
writeInt(h, kexDHGexReply.Y)
|
|
K := make([]byte, intLength(kInt))
|
|
marshalInt(K, kInt)
|
|
h.Write(K)
|
|
|
|
return &kexResult{
|
|
H: h.Sum(nil),
|
|
K: K,
|
|
HostKey: kexDHGexReply.HostKey,
|
|
Signature: kexDHGexReply.Signature,
|
|
Hash: gex.hashFunc,
|
|
}, nil
|
|
}
|
|
|
|
// 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) {
|
|
// Receive GexRequest
|
|
packet, err := c.readPacket()
|
|
if err != nil {
|
|
return
|
|
}
|
|
var kexDHGexRequest kexDHGexRequestMsg
|
|
if err = Unmarshal(packet, &kexDHGexRequest); err != nil {
|
|
return
|
|
}
|
|
|
|
// smoosh the user's preferred size into our own limits
|
|
if kexDHGexRequest.PreferedBits > dhGroupExchangeMaximumBits {
|
|
kexDHGexRequest.PreferedBits = dhGroupExchangeMaximumBits
|
|
}
|
|
if kexDHGexRequest.PreferedBits < dhGroupExchangeMinimumBits {
|
|
kexDHGexRequest.PreferedBits = dhGroupExchangeMinimumBits
|
|
}
|
|
// fix min/max if they're inconsistent. technically, we could just pout
|
|
// and hang up, but there's no harm in giving them the benefit of the
|
|
// doubt and just picking a bitsize for them.
|
|
if kexDHGexRequest.MinBits > kexDHGexRequest.PreferedBits {
|
|
kexDHGexRequest.MinBits = kexDHGexRequest.PreferedBits
|
|
}
|
|
if kexDHGexRequest.MaxBits < kexDHGexRequest.PreferedBits {
|
|
kexDHGexRequest.MaxBits = kexDHGexRequest.PreferedBits
|
|
}
|
|
|
|
// 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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
|
|
gex.p = p
|
|
gex.g = big.NewInt(2)
|
|
|
|
kexDHGexGroup := kexDHGexGroupMsg{
|
|
P: gex.p,
|
|
G: gex.g,
|
|
}
|
|
if err := c.writePacket(Marshal(&kexDHGexGroup)); err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
// Receive GexInit
|
|
packet, err = c.readPacket()
|
|
if err != nil {
|
|
return
|
|
}
|
|
var kexDHGexInit kexDHGexInitMsg
|
|
if err = Unmarshal(packet, &kexDHGexInit); err != nil {
|
|
return
|
|
}
|
|
|
|
var pHalf = &big.Int{}
|
|
pHalf.Rsh(gex.p, 1)
|
|
|
|
y, err := rand.Int(randSource, pHalf)
|
|
if err != nil {
|
|
return
|
|
}
|
|
|
|
Y := new(big.Int).Exp(gex.g, y, gex.p)
|
|
kInt, err := gex.diffieHellman(kexDHGexInit.X, y)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
hostKeyBytes := priv.PublicKey().Marshal()
|
|
|
|
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))
|
|
writeInt(h, gex.p)
|
|
writeInt(h, gex.g)
|
|
writeInt(h, kexDHGexInit.X)
|
|
writeInt(h, Y)
|
|
|
|
K := make([]byte, intLength(kInt))
|
|
marshalInt(K, kInt)
|
|
h.Write(K)
|
|
|
|
H := h.Sum(nil)
|
|
|
|
// H is already a hash, but the hostkey signing will apply its
|
|
// own key-specific hash algorithm.
|
|
sig, err := signAndMarshal(priv, randSource, H)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
kexDHGexReply := kexDHGexReplyMsg{
|
|
HostKey: hostKeyBytes,
|
|
Y: Y,
|
|
Signature: sig,
|
|
}
|
|
packet = Marshal(&kexDHGexReply)
|
|
|
|
err = c.writePacket(packet)
|
|
|
|
return &kexResult{
|
|
H: H,
|
|
K: K,
|
|
HostKey: hostKeyBytes,
|
|
Signature: sig,
|
|
Hash: gex.hashFunc,
|
|
}, err
|
|
}
|