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exp/ssh: improved client authentication support
This CL adds an API for handling the various SSH authenticaton methods. None and password continue to be the only supported methods. R=bradfitz, agl, n13m3y3r, rsc, cw CC=golang-dev https://golang.org/cl/5328045
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@ -8,6 +8,7 @@ TARG=exp/ssh
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GOFILES=\
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channel.go\
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client.go\
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client_auth.go\
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common.go\
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messages.go\
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transport.go\
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@ -131,56 +131,6 @@ func (c *ClientConn) handshake() error {
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return c.transport.reader.setupKeys(serverKeys, K, H, H, hashFunc)
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}
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// authenticate authenticates with the remote server. See RFC 4252.
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// Only "password" authentication is supported.
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func (c *ClientConn) authenticate() error {
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if err := c.writePacket(marshal(msgServiceRequest, serviceRequestMsg{serviceUserAuth})); err != nil {
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return err
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}
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packet, err := c.readPacket()
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if err != nil {
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return err
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}
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var serviceAccept serviceAcceptMsg
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if err = unmarshal(&serviceAccept, packet, msgServiceAccept); err != nil {
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return err
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}
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// TODO(dfc) support proper authentication method negotation
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method := "none"
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if c.config.Password != "" {
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method = "password"
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}
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if err := c.sendUserAuthReq(method); err != nil {
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return err
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}
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if packet, err = c.readPacket(); err != nil {
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return err
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}
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if packet[0] != msgUserAuthSuccess {
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return UnexpectedMessageError{msgUserAuthSuccess, packet[0]}
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}
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return nil
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}
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func (c *ClientConn) sendUserAuthReq(method string) error {
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length := stringLength([]byte(c.config.Password)) + 1
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payload := make([]byte, length)
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// always false for password auth, see RFC 4252 Section 8.
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payload[0] = 0
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marshalString(payload[1:], []byte(c.config.Password))
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return c.writePacket(marshal(msgUserAuthRequest, userAuthRequestMsg{
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User: c.config.User,
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Service: serviceSSH,
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Method: method,
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Payload: payload,
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}))
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}
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// kexDH performs Diffie-Hellman key agreement on a ClientConn. The
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// returned values are given the same names as in RFC 4253, section 8.
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func (c *ClientConn) kexDH(group *dhGroup, hashFunc crypto.Hash, magics *handshakeMagics, hostKeyAlgo string) ([]byte, []byte, error) {
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@ -348,8 +298,9 @@ type ClientConfig struct {
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// The username to authenticate.
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User string
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// Used for "password" method authentication.
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Password string
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// A slice of ClientAuth methods. Only the first instance
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// of a particular RFC 4252 method will be used during authentication.
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Auth []ClientAuth
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}
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func (c *ClientConfig) rand() io.Reader {
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157
src/pkg/exp/ssh/client_auth.go
Normal file
157
src/pkg/exp/ssh/client_auth.go
Normal file
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@ -0,0 +1,157 @@
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// Copyright 2011 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package ssh
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import (
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"errors"
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)
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// authenticate authenticates with the remote server. See RFC 4252.
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func (c *ClientConn) authenticate() error {
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// initiate user auth session
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if err := c.writePacket(marshal(msgServiceRequest, serviceRequestMsg{serviceUserAuth})); err != nil {
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return err
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}
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packet, err := c.readPacket()
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if err != nil {
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return err
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}
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var serviceAccept serviceAcceptMsg
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if err := unmarshal(&serviceAccept, packet, msgServiceAccept); err != nil {
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return err
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}
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// during the authentication phase the client first attempts the "none" method
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// then any untried methods suggested by the server.
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tried, remain := make(map[string]bool), make(map[string]bool)
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for auth := ClientAuth(new(noneAuth)); auth != nil; {
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ok, methods, err := auth.auth(c.config.User, c.transport)
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if err != nil {
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return err
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}
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if ok {
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// success
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return nil
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}
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tried[auth.method()] = true
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delete(remain, auth.method())
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for _, meth := range methods {
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if tried[meth] {
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// if we've tried meth already, skip it.
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continue
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}
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remain[meth] = true
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}
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auth = nil
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for _, a := range c.config.Auth {
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if remain[a.method()] {
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auth = a
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break
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}
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}
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}
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return errors.New("ssh: unable to authenticate, no supported methods remain")
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}
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// A ClientAuth represents an instance of an RFC 4252 authentication method.
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type ClientAuth interface {
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// auth authenticates user over transport t.
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// Returns true if authentication is successful.
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// If authentication is not successful, a []string of alternative
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// method names is returned.
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auth(user string, t *transport) (bool, []string, error)
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// method returns the RFC 4252 method name.
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method() string
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}
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// "none" authentication, RFC 4252 section 5.2.
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type noneAuth int
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func (n *noneAuth) auth(user string, t *transport) (bool, []string, error) {
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if err := t.writePacket(marshal(msgUserAuthRequest, userAuthRequestMsg{
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User: user,
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Service: serviceSSH,
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Method: "none",
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})); err != nil {
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return false, nil, err
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}
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packet, err := t.readPacket()
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if err != nil {
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return false, nil, err
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}
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switch packet[0] {
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case msgUserAuthSuccess:
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return true, nil, nil
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case msgUserAuthFailure:
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msg := decode(packet).(*userAuthFailureMsg)
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return false, msg.Methods, nil
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}
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return false, nil, UnexpectedMessageError{msgUserAuthSuccess, packet[0]}
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}
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func (n *noneAuth) method() string {
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return "none"
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}
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// "password" authentication, RFC 4252 Section 8.
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type passwordAuth struct {
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ClientPassword
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}
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func (p *passwordAuth) auth(user string, t *transport) (bool, []string, error) {
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type passwordAuthMsg struct {
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User string
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Service string
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Method string
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Reply bool
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Password string
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}
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pw, err := p.Password(user)
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if err != nil {
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return false, nil, err
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}
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if err := t.writePacket(marshal(msgUserAuthRequest, passwordAuthMsg{
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User: user,
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Service: serviceSSH,
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Method: "password",
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Reply: false,
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Password: pw,
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})); err != nil {
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return false, nil, err
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}
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packet, err := t.readPacket()
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if err != nil {
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return false, nil, err
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}
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switch packet[0] {
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case msgUserAuthSuccess:
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return true, nil, nil
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case msgUserAuthFailure:
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msg := decode(packet).(*userAuthFailureMsg)
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return false, msg.Methods, nil
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}
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return false, nil, UnexpectedMessageError{msgUserAuthSuccess, packet[0]}
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}
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func (p *passwordAuth) method() string {
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return "password"
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}
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// A ClientPassword implements access to a client's passwords.
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type ClientPassword interface {
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// Password returns the password to use for user.
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Password(user string) (password string, err error)
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}
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// ClientAuthPassword returns a ClientAuth using password authentication.
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func ClientAuthPassword(impl ClientPassword) ClientAuth {
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return &passwordAuth{impl}
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}
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@ -83,7 +83,7 @@ authentication method is supported.
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config := &ClientConfig{
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User: "username",
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Password: "123456",
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Auth: []ClientAuth{ ... },
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}
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client, err := Dial("yourserver.com:22", config)
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