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exp/ssh: add client side support for publickey auth

Browse Source 
client.go/client_auth.go:
* add support for publickey key auth using the interface
  outlined by rsc in the previous auth CL

client_auth_test.go:
* password and publickey tests against server.go

common.go/server.go:
* move some helper methods from server.go into common.go
* generalise serializeRSASignature

R=rsc, agl, huin
CC=cw, golang-dev, n13m3y3r
https://golang.org/cl/5373055
This commit is contained in:
Dave Cheney 2011-11-13 14:48:22 -05:00 committed by Adam Langley
parent 90ec203318
commit 3ee171d174
5 changed files with 483 additions and 52 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

9
src/pkg/exp/ssh/client.go
View File

@ -35,10 +35,6 @@ func Client(c net.Conn, config *ClientConfig) (*ClientConn, error) {
conn.Close()
return nil, err
}
if err := conn.authenticate(); err != nil {
conn.Close()
return nil, err
}
go conn.mainLoop()
return conn, nil
}
@ -128,7 +124,10 @@ func (c *ClientConn) handshake() error {
if packet[0] != msgNewKeys {
return UnexpectedMessageError{msgNewKeys, packet[0]}
}
return c.transport.reader.setupKeys(serverKeys, K, H, H, hashFunc)
if err := c.transport.reader.setupKeys(serverKeys, K, H, H, hashFunc); err != nil {
return err
}
return c.authenticate(H)
}
// kexDH performs Diffie-Hellman key agreement on a ClientConn. The

150
src/pkg/exp/ssh/client_auth.go
View File

@ -5,11 +5,13 @@
package ssh
import (
"crypto/rand"
"errors"
"io"
)
// authenticate authenticates with the remote server. See RFC 4252.
func (c *ClientConn) authenticate() error {
func (c *ClientConn) authenticate(session []byte) error {
// initiate user auth session
if err := c.writePacket(marshal(msgServiceRequest, serviceRequestMsg{serviceUserAuth})); err != nil {
return err
@ -26,7 +28,7 @@ func (c *ClientConn) authenticate() error {
// then any untried methods suggested by the server.
tried, remain := make(map[string]bool), make(map[string]bool)
for auth := ClientAuth(new(noneAuth)); auth != nil; {
ok, methods, err := auth.auth(c.config.User, c.transport)
ok, methods, err := auth.auth(session, c.config.User, c.transport)
if err != nil {
return err
}
@ -60,7 +62,7 @@ type ClientAuth interface {
// Returns true if authentication is successful.
// If authentication is not successful, a []string of alternative
// method names is returned.
auth(user string, t *transport) (bool, []string, error)
auth(session []byte, user string, t *transport) (bool, []string, error)
// method returns the RFC 4252 method name.
method() string
@ -69,7 +71,7 @@ type ClientAuth interface {
// "none" authentication, RFC 4252 section 5.2.
type noneAuth int
func (n *noneAuth) auth(user string, t *transport) (bool, []string, error) {
func (n *noneAuth) auth(session []byte, user string, t *transport) (bool, []string, error) {
if err := t.writePacket(marshal(msgUserAuthRequest, userAuthRequestMsg{
User: user,
Service: serviceSSH,
@ -102,7 +104,7 @@ type passwordAuth struct {
ClientPassword
}
func (p *passwordAuth) auth(user string, t *transport) (bool, []string, error) {
func (p *passwordAuth) auth(session []byte, user string, t *transport) (bool, []string, error) {
type passwordAuthMsg struct {
User string
Service string
@ -155,3 +157,141 @@ type ClientPassword interface {
func ClientAuthPassword(impl ClientPassword) ClientAuth {
return &passwordAuth{impl}
}
// ClientKeyring implements access to a client key ring.
type ClientKeyring interface {
// Key returns the i'th rsa.Publickey or dsa.Publickey, or nil if
// no key exists at i.
Key(i int) (key interface{}, err error)
// Sign returns a signature of the given data using the i'th key
// and the supplied random source.
Sign(i int, rand io.Reader, data []byte) (sig []byte, err error)
}
// "publickey" authentication, RFC 4252 Section 7.
type publickeyAuth struct {
ClientKeyring
}
func (p *publickeyAuth) auth(session []byte, user string, t *transport) (bool, []string, error) {
type publickeyAuthMsg struct {
User string
Service string
Method string
// HasSig indicates to the reciver packet that the auth request is signed and
// should be used for authentication of the request.
HasSig bool
Algoname string
Pubkey string
// Sig is defined as []byte so marshal will exclude it during the query phase
Sig []byte `ssh:"rest"`
}
// Authentication is performed in two stages. The first stage sends an
// enquiry to test if each key is acceptable to the remote. The second
// stage attempts to authenticate with the valid keys obtained in the
// first stage.
var index int
// a map of public keys to their index in the keyring
validKeys := make(map[int]interface{})
for {
key, err := p.Key(index)
if err != nil {
return false, nil, err
}
if key == nil {
// no more keys in the keyring
break
}
pubkey := serializePublickey(key)
algoname := algoName(key)
msg := publickeyAuthMsg{
User: user,
Service: serviceSSH,
Method: p.method(),
HasSig: false,
Algoname: algoname,
Pubkey: string(pubkey),
}
if err := t.writePacket(marshal(msgUserAuthRequest, msg)); err != nil {
return false, nil, err
}
packet, err := t.readPacket()
if err != nil {
return false, nil, err
}
switch packet[0] {
case msgUserAuthPubKeyOk:
msg := decode(packet).(*userAuthPubKeyOkMsg)
if msg.Algo != algoname || msg.PubKey != string(pubkey) {
continue
}
validKeys[index] = key
case msgUserAuthFailure:
default:
return false, nil, UnexpectedMessageError{msgUserAuthSuccess, packet[0]}
}
index++
}
// methods that may continue if this auth is not successful.
var methods []string
for i, key := range validKeys {
pubkey := serializePublickey(key)
algoname := algoName(key)
// TODO(dfc) use random source from the ClientConfig
sign, err := p.Sign(i, rand.Reader, buildDataSignedForAuth(session, userAuthRequestMsg{
User: user,
Service: serviceSSH,
Method: p.method(),
}, []byte(algoname), pubkey))
if err != nil {
return false, nil, err
}
// manually wrap the serialized signature in a string
s := serializeSignature(algoname, sign)
sig := make([]byte, stringLength(s))
marshalString(sig, s)
msg := publickeyAuthMsg{
User: user,
Service: serviceSSH,
Method: p.method(),
HasSig: true,
Algoname: algoname,
Pubkey: string(pubkey),
Sig: sig,
}
p := marshal(msgUserAuthRequest, msg)
if err := t.writePacket(p); err != nil {
return false, nil, err
}
packet, err := t.readPacket()
if err != nil {
return false, nil, err
}
switch packet[0] {
case msgUserAuthSuccess:
return true, nil, nil
case msgUserAuthFailure:
msg := decode(packet).(*userAuthFailureMsg)
methods = msg.Methods
continue
case msgDisconnect:
return false, nil, io.EOF
default:
return false, nil, UnexpectedMessageError{msgUserAuthSuccess, packet[0]}
}
}
return false, methods, nil
}
func (p *publickeyAuth) method() string {
return "publickey"
}
// ClientAuthPublickey returns a ClientAuth using public key authentication.
func ClientAuthPublickey(impl ClientKeyring) ClientAuth {
return &publickeyAuth{impl}
}

248
src/pkg/exp/ssh/client_auth_test.go Normal file
View File

@ -0,0 +1,248 @@
// Copyright 2011 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 (
"bytes"
"crypto"
"crypto/rand"
"crypto/rsa"
"crypto/x509"
"encoding/pem"
"errors"
"io"
"io/ioutil"
"testing"
)
const _pem = `-----BEGIN RSA PRIVATE KEY-----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-----END RSA PRIVATE KEY-----`
// reused internally by tests
var serverConfig = new(ServerConfig)
func init() {
if err := serverConfig.SetRSAPrivateKey([]byte(_pem)); err != nil {
panic("unable to set private key: " + err.Error())
}
}
// keychain implements the ClientPublickey interface
type keychain struct {
keys []*rsa.PrivateKey
}
func (k *keychain) Key(i int) (interface{}, error) {
if i < 0 || i >= len(k.keys) {
return nil, nil
}
return k.keys[i].PublicKey, nil
}
func (k *keychain) Sign(i int, rand io.Reader, data []byte) (sig []byte, err error) {
hashFunc := crypto.SHA1
h := hashFunc.New()
h.Write(data)
digest := h.Sum()
return rsa.SignPKCS1v15(rand, k.keys[i], hashFunc, digest)
}
func (k *keychain) loadPEM(file string) error {
buf, err := ioutil.ReadFile(file)
if err != nil {
return err
}
block, _ := pem.Decode(buf)
if block == nil {
return errors.New("ssh: no key found")
}
r, err := x509.ParsePKCS1PrivateKey(block.Bytes)
if err != nil {
return err
}
k.keys = append(k.keys, r)
return nil
}
var pkey *rsa.PrivateKey
func init() {
var err error
pkey, err = rsa.GenerateKey(rand.Reader, 512)
if err != nil {
panic("unable to generate public key")
}
}
func TestClientAuthPublickey(t *testing.T) {
k := new(keychain)
k.keys = append(k.keys, pkey)
serverConfig.PubKeyCallback = func(user, algo string, pubkey []byte) bool {
expected := []byte(serializePublickey(k.keys[0].PublicKey))
algoname := algoName(k.keys[0].PublicKey)
return user == "testuser" && algo == algoname && bytes.Equal(pubkey, expected)
}
serverConfig.PasswordCallback = nil
l, err := Listen("tcp", "0.0.0.0:0", serverConfig)
if err != nil {
t.Fatalf("unable to listen: %s", err)
}
defer l.Close()
done := make(chan bool)
go func() {
c, err := l.Accept()
if err != nil {
t.Fatal(err)
}
if err := c.Handshake(); err != nil {
t.Error(err)
}
defer c.Close()
done <- true
}()
config := &ClientConfig{
User: "testuser",
Auth: []ClientAuth{
ClientAuthPublickey(k),
},
}
c, err := Dial("tcp", l.Addr().String(), config)
if err != nil {
t.Errorf("unable to dial remote side: %s", err)
}
defer c.Close()
<-done
}
// password implements the ClientPassword interface
type password string
func (p password) Password(user string) (string, error) {
return string(p), nil
}
func TestClientAuthPassword(t *testing.T) {
pw := password("tiger")
serverConfig.PasswordCallback = func(user, pass string) bool {
return user == "testuser" && pass == string(pw)
}
serverConfig.PubKeyCallback = nil
l, err := Listen("tcp", "0.0.0.0:0", serverConfig)
if err != nil {
t.Fatalf("unable to listen: %s", err)
}
defer l.Close()
done := make(chan bool)
go func() {
c, err := l.Accept()
if err != nil {
t.Fatal(err)
}
if err := c.Handshake(); err != nil {
t.Error(err)
}
defer c.Close()
done <- true
}()
config := &ClientConfig{
User: "testuser",
Auth: []ClientAuth{
ClientAuthPassword(pw),
},
}
c, err := Dial("tcp", l.Addr().String(), config)
if err != nil {
t.Errorf("unable to dial remote side: %s", err)
}
defer c.Close()
<-done
}
func TestClientAuthPasswordAndPublickey(t *testing.T) {
pw := password("tiger")
serverConfig.PasswordCallback = func(user, pass string) bool {
return user == "testuser" && pass == string(pw)
}
k := new(keychain)
k.keys = append(k.keys, pkey)
serverConfig.PubKeyCallback = func(user, algo string, pubkey []byte) bool {
expected := []byte(serializePublickey(k.keys[0].PublicKey))
algoname := algoName(k.keys[0].PublicKey)
return user == "testuser" && algo == algoname && bytes.Equal(pubkey, expected)
}
l, err := Listen("tcp", "0.0.0.0:0", serverConfig)
if err != nil {
t.Fatalf("unable to listen: %s", err)
}
defer l.Close()
done := make(chan bool)
go func() {
c, err := l.Accept()
if err != nil {
t.Fatal(err)
}
if err := c.Handshake(); err != nil {
t.Error(err)
}
defer c.Close()
done <- true
}()
wrongPw := password("wrong")
config := &ClientConfig{
User: "testuser",
Auth: []ClientAuth{
ClientAuthPassword(wrongPw),
ClientAuthPublickey(k),
},
}
c, err := Dial("tcp", l.Addr().String(), config)
if err != nil {
t.Errorf("unable to dial remote side: %s", err)
}
defer c.Close()
<-done
}

85
src/pkg/exp/ssh/common.go
View File

@ -5,6 +5,8 @@
package ssh
import (
"crypto/dsa"
"crypto/rsa"
"math/big"
"strconv"
"sync"
@ -127,3 +129,86 @@ func findAgreedAlgorithms(transport *transport, clientKexInit, serverKexInit *ke
ok = true
return
}
// serialize a signed slice according to RFC 4254 6.6.
func serializeSignature(algoname string, sig []byte) []byte {
length := stringLength([]byte(algoname))
length += stringLength(sig)
ret := make([]byte, length)
r := marshalString(ret, []byte(algoname))
r = marshalString(r, sig)
return ret
}
// serialize an rsa.PublicKey or dsa.PublicKey according to RFC 4253 6.6.
func serializePublickey(key interface{}) []byte {
algoname := algoName(key)
switch key := key.(type) {
case rsa.PublicKey:
e := new(big.Int).SetInt64(int64(key.E))
length := stringLength([]byte(algoname))
length += intLength(e)
length += intLength(key.N)
ret := make([]byte, length)
r := marshalString(ret, []byte(algoname))
r = marshalInt(r, e)
marshalInt(r, key.N)
return ret
case dsa.PublicKey:
length := stringLength([]byte(algoname))
length += intLength(key.P)
length += intLength(key.Q)
length += intLength(key.G)
length += intLength(key.Y)
ret := make([]byte, length)
r := marshalString(ret, []byte(algoname))
r = marshalInt(r, key.P)
r = marshalInt(r, key.Q)
r = marshalInt(r, key.G)
marshalInt(r, key.Y)
return ret
}
panic("unexpected key type")
}
func algoName(key interface{}) string {
switch key.(type) {
case rsa.PublicKey:
return "ssh-rsa"
case dsa.PublicKey:
return "ssh-dss"
}
panic("unexpected key type")
}
// buildDataSignedForAuth returns the data that is signed in order to prove
// posession of a private key. See RFC 4252, section 7.
func buildDataSignedForAuth(sessionId []byte, req userAuthRequestMsg, algo, pubKey []byte) []byte {
user := []byte(req.User)
service := []byte(req.Service)
method := []byte(req.Method)
length := stringLength(sessionId)
length += 1
length += stringLength(user)
length += stringLength(service)
length += stringLength(method)
length += 1
length += stringLength(algo)
length += stringLength(pubKey)
ret := make([]byte, length)
r := marshalString(ret, sessionId)
r[0] = msgUserAuthRequest
r = r[1:]
r = marshalString(r, user)
r = marshalString(r, service)
r = marshalString(r, method)
r[0] = 1
r = r[1:]
r = marshalString(r, algo)
r = marshalString(r, pubKey)
return ret
}

43
src/pkg/exp/ssh/server.go
View File

@ -221,7 +221,7 @@ func (s *ServerConn) kexDH(group *dhGroup, hashFunc crypto.Hash, magics *handsha
return nil, nil, errors.New("internal error")
}
serializedSig := serializeRSASignature(sig)
serializedSig := serializeSignature(hostAlgoRSA, sig)
kexDHReply := kexDHReplyMsg{
HostKey: serializedHostKey,
@ -234,50 +234,9 @@ func (s *ServerConn) kexDH(group *dhGroup, hashFunc crypto.Hash, magics *handsha
return
}
func serializeRSASignature(sig []byte) []byte {
length := stringLength([]byte(hostAlgoRSA))
length += stringLength(sig)
ret := make([]byte, length)
r := marshalString(ret, []byte(hostAlgoRSA))
r = marshalString(r, sig)
return ret
}
// serverVersion is the fixed identification string that Server will use.
var serverVersion = []byte("SSH-2.0-Go\r\n")
// buildDataSignedForAuth returns the data that is signed in order to prove
// posession of a private key. See RFC 4252, section 7.
func buildDataSignedForAuth(sessionId []byte, req userAuthRequestMsg, algo, pubKey []byte) []byte {
user := []byte(req.User)
service := []byte(req.Service)
method := []byte(req.Method)
length := stringLength(sessionId)
length += 1
length += stringLength(user)
length += stringLength(service)
length += stringLength(method)
length += 1
length += stringLength(algo)
length += stringLength(pubKey)
ret := make([]byte, length)
r := marshalString(ret, sessionId)
r[0] = msgUserAuthRequest
r = r[1:]
r = marshalString(r, user)
r = marshalString(r, service)
r = marshalString(r, method)
r[0] = 1
r = r[1:]
r = marshalString(r, algo)
r = marshalString(r, pubKey)
return ret
}
// Handshake performs an SSH transport and client authentication on the given ServerConn.
func (s *ServerConn) Handshake() error {
var magics handshakeMagics