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// 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"
"io"
"math/big"
"reflect"
)
// These are SSH message type numbers. They are scattered around several
// documents but many were taken from
// http://www.iana.org/assignments/ssh-parameters/ssh-parameters.xml#ssh-parameters-1
const (
msgDisconnect = 1
msgIgnore = 2
msgUnimplemented = 3
msgDebug = 4
msgServiceRequest = 5
msgServiceAccept = 6
msgKexInit = 20
msgNewKeys = 21
msgKexDHInit = 30
msgKexDHReply = 31
msgUserAuthRequest = 50
msgUserAuthFailure = 51
msgUserAuthSuccess = 52
msgUserAuthBanner = 53
msgUserAuthPubKeyOk = 60
msgGlobalRequest = 80
msgRequestSuccess = 81
msgRequestFailure = 82
msgChannelOpen = 90
msgChannelOpenConfirm = 91
msgChannelOpenFailure = 92
msgChannelWindowAdjust = 93
msgChannelData = 94
msgChannelExtendedData = 95
msgChannelEOF = 96
msgChannelClose = 97
msgChannelRequest = 98
msgChannelSuccess = 99
msgChannelFailure = 100
)
// SSH messages:
//
// These structures mirror the wire format of the corresponding SSH messages.
// They are marshaled using reflection with the marshal and unmarshal functions
// in this file. The only wrinkle is that a final member of type []byte with a
// ssh tag of "rest" receives the remainder of a packet when unmarshaling.
// See RFC 4253, section 11.1.
type disconnectMsg struct {
Reason uint32
Message string
Language string
}
// See RFC 4253, section 7.1.
type kexInitMsg struct {
Cookie [16]byte
KexAlgos []string
ServerHostKeyAlgos []string
CiphersClientServer []string
CiphersServerClient []string
MACsClientServer []string
MACsServerClient []string
CompressionClientServer []string
CompressionServerClient []string
LanguagesClientServer []string
LanguagesServerClient []string
FirstKexFollows bool
Reserved uint32
}
// See RFC 4253, section 8.
type kexDHInitMsg struct {
X *big.Int
}
type kexDHReplyMsg struct {
HostKey []byte
Y *big.Int
Signature []byte
}
// See RFC 4253, section 10.
type serviceRequestMsg struct {
Service string
}
// See RFC 4253, section 10.
type serviceAcceptMsg struct {
Service string
}
// See RFC 4252, section 5.
type userAuthRequestMsg struct {
User string
Service string
Method string
Payload []byte `ssh:"rest"`
}
// See RFC 4252, section 5.1
type userAuthFailureMsg struct {
Methods []string
PartialSuccess bool
}
// See RFC 4254, section 5.1.
type channelOpenMsg struct {
ChanType string
PeersId uint32
PeersWindow uint32
MaxPacketSize uint32
TypeSpecificData []byte `ssh:"rest"`
}
// See RFC 4254, section 5.1.
type channelOpenConfirmMsg struct {
PeersId uint32
MyId uint32
MyWindow uint32
MaxPacketSize uint32
TypeSpecificData []byte `ssh:"rest"`
}
// See RFC 4254, section 5.1.
type channelOpenFailureMsg struct {
PeersId uint32
Reason uint32
Message string
Language string
}
type channelRequestMsg struct {
PeersId uint32
Request string
WantReply bool
RequestSpecificData []byte `ssh:"rest"`
}
// See RFC 4254, section 5.4.
type channelRequestSuccessMsg struct {
PeersId uint32
}
// See RFC 4254, section 5.4.
type channelRequestFailureMsg struct {
PeersId uint32
}
// See RFC 4254, section 5.3
type channelCloseMsg struct {
PeersId uint32
}
// See RFC 4254, section 5.3
type channelEOFMsg struct {
PeersId uint32
}
// See RFC 4254, section 4
type globalRequestMsg struct {
Type string
WantReply bool
}
// See RFC 4254, section 5.2
type windowAdjustMsg struct {
PeersId uint32
AdditionalBytes uint32
}
// See RFC 4252, section 7
type userAuthPubKeyOkMsg struct {
Algo string
PubKey string
}
// unmarshal parses the SSH wire data in packet into out using reflection.
// expectedType is the expected SSH message type. It either returns nil on
// success, or a ParseError or UnexpectedMessageError on error.
func unmarshal(out interface{}, packet []byte, expectedType uint8) error {
if len(packet) == 0 {
return ParseError{expectedType}
}
if packet[0] != expectedType {
return UnexpectedMessageError{expectedType, packet[0]}
}
packet = packet[1:]
v := reflect.ValueOf(out).Elem()
structType := v.Type()
var ok bool
for i := 0; i < v.NumField(); i++ {
field := v.Field(i)
t := field.Type()
switch t.Kind() {
case reflect.Bool:
if len(packet) < 1 {
return ParseError{expectedType}
}
field.SetBool(packet[0] != 0)
packet = packet[1:]
case reflect.Array:
if t.Elem().Kind() != reflect.Uint8 {
panic("array of non-uint8")
}
if len(packet) < t.Len() {
return ParseError{expectedType}
}
for j := 0; j < t.Len(); j++ {
field.Index(j).Set(reflect.ValueOf(packet[j]))
}
packet = packet[t.Len():]
case reflect.Uint32:
var u32 uint32
if u32, packet, ok = parseUint32(packet); !ok {
return ParseError{expectedType}
}
field.SetUint(uint64(u32))
case reflect.String:
var s []byte
if s, packet, ok = parseString(packet); !ok {
return ParseError{expectedType}
}
field.SetString(string(s))
case reflect.Slice:
switch t.Elem().Kind() {
case reflect.Uint8:
if structType.Field(i).Tag.Get("ssh") == "rest" {
field.Set(reflect.ValueOf(packet))
packet = nil
} else {
var s []byte
if s, packet, ok = parseString(packet); !ok {
return ParseError{expectedType}
}
field.Set(reflect.ValueOf(s))
}
case reflect.String:
var nl []string
if nl, packet, ok = parseNameList(packet); !ok {
return ParseError{expectedType}
}
field.Set(reflect.ValueOf(nl))
default:
panic("slice of unknown type")
}
case reflect.Ptr:
if t == bigIntType {
var n *big.Int
if n, packet, ok = parseInt(packet); !ok {
return ParseError{expectedType}
}
field.Set(reflect.ValueOf(n))
} else {
panic("pointer to unknown type")
}
default:
panic("unknown type")
}
}
if len(packet) != 0 {
return ParseError{expectedType}
}
return nil
}
// marshal serializes the message in msg, using the given message type.
func marshal(msgType uint8, msg interface{}) []byte {
var out []byte
out = append(out, msgType)
v := reflect.ValueOf(msg)
structType := v.Type()
for i := 0; i < v.NumField(); i++ {
field := v.Field(i)
t := field.Type()
switch t.Kind() {
case reflect.Bool:
var v uint8
if field.Bool() {
v = 1
}
out = append(out, v)
case reflect.Array:
if t.Elem().Kind() != reflect.Uint8 {
panic("array of non-uint8")
}
for j := 0; j < t.Len(); j++ {
out = append(out, byte(field.Index(j).Uint()))
}
case reflect.Uint32:
u32 := uint32(field.Uint())
out = append(out, byte(u32>>24))
out = append(out, byte(u32>>16))
out = append(out, byte(u32>>8))
out = append(out, byte(u32))
case reflect.String:
s := field.String()
out = append(out, byte(len(s)>>24))
out = append(out, byte(len(s)>>16))
out = append(out, byte(len(s)>>8))
out = append(out, byte(len(s)))
out = append(out, s...)
case reflect.Slice:
switch t.Elem().Kind() {
case reflect.Uint8:
length := field.Len()
if structType.Field(i).Tag.Get("ssh") != "rest" {
out = append(out, byte(length>>24))
out = append(out, byte(length>>16))
out = append(out, byte(length>>8))
out = append(out, byte(length))
}
for j := 0; j < length; j++ {
out = append(out, byte(field.Index(j).Uint()))
}
case reflect.String:
var length int
for j := 0; j < field.Len(); j++ {
if j != 0 {
length++ /* comma */
}
length += len(field.Index(j).String())
}
out = append(out, byte(length>>24))
out = append(out, byte(length>>16))
out = append(out, byte(length>>8))
out = append(out, byte(length))
for j := 0; j < field.Len(); j++ {
if j != 0 {
out = append(out, ',')
}
out = append(out, field.Index(j).String()...)
}
default:
panic("slice of unknown type")
}
case reflect.Ptr:
if t == bigIntType {
var n *big.Int
nValue := reflect.ValueOf(&n)
nValue.Elem().Set(field)
needed := intLength(n)
oldLength := len(out)
if cap(out)-len(out) < needed {
newOut := make([]byte, len(out), 2*(len(out)+needed))
copy(newOut, out)
out = newOut
}
out = out[:oldLength+needed]
marshalInt(out[oldLength:], n)
} else {
panic("pointer to unknown type")
}
}
}
return out
}
var bigOne = big.NewInt(1)
func parseString(in []byte) (out, rest []byte, ok bool) {
if len(in) < 4 {
return
}
length := uint32(in[0])<<24 | uint32(in[1])<<16 | uint32(in[2])<<8 | uint32(in[3])
if uint32(len(in)) < 4+length {
return
}
out = in[4 : 4+length]
rest = in[4+length:]
ok = true
return
}
var comma = []byte{','}
func parseNameList(in []byte) (out []string, rest []byte, ok bool) {
contents, rest, ok := parseString(in)
if !ok {
return
}
if len(contents) == 0 {
return
}
parts := bytes.Split(contents, comma)
out = make([]string, len(parts))
for i, part := range parts {
out[i] = string(part)
}
return
}
func parseInt(in []byte) (out *big.Int, rest []byte, ok bool) {
contents, rest, ok := parseString(in)
if !ok {
return
}
out = new(big.Int)
if len(contents) > 0 && contents[0]&0x80 == 0x80 {
// This is a negative number
notBytes := make([]byte, len(contents))
for i := range notBytes {
notBytes[i] = ^contents[i]
}
out.SetBytes(notBytes)
out.Add(out, bigOne)
out.Neg(out)
} else {
// Positive number
out.SetBytes(contents)
}
ok = true
return
}
func parseUint32(in []byte) (out uint32, rest []byte, ok bool) {
if len(in) < 4 {
return
}
out = uint32(in[0])<<24 | uint32(in[1])<<16 | uint32(in[2])<<8 | uint32(in[3])
rest = in[4:]
ok = true
return
}
const maxPacketSize = 36000
func nameListLength(namelist []string) int {
length := 4 /* uint32 length prefix */
for i, name := range namelist {
if i != 0 {
length++ /* comma */
}
length += len(name)
}
return length
}
func intLength(n *big.Int) int {
length := 4 /* length bytes */
if n.Sign() < 0 {
nMinus1 := new(big.Int).Neg(n)
nMinus1.Sub(nMinus1, bigOne)
bitLen := nMinus1.BitLen()
if bitLen%8 == 0 {
// The number will need 0xff padding
length++
}
length += (bitLen + 7) / 8
} else if n.Sign() == 0 {
// A zero is the zero length string
} else {
bitLen := n.BitLen()
if bitLen%8 == 0 {
// The number will need 0x00 padding
length++
}
length += (bitLen + 7) / 8
}
return length
}
func marshalInt(to []byte, n *big.Int) []byte {
lengthBytes := to
to = to[4:]
length := 0
if n.Sign() < 0 {
// A negative number has to be converted to two's-complement
// form. So we'll subtract 1 and invert. If the
// most-significant-bit isn't set then we'll need to pad the
// beginning with 0xff in order to keep the number negative.
nMinus1 := new(big.Int).Neg(n)
nMinus1.Sub(nMinus1, bigOne)
bytes := nMinus1.Bytes()
for i := range bytes {
bytes[i] ^= 0xff
}
if len(bytes) == 0 || bytes[0]&0x80 == 0 {
to[0] = 0xff
to = to[1:]
length++
}
nBytes := copy(to, bytes)
to = to[nBytes:]
length += nBytes
} else if n.Sign() == 0 {
// A zero is the zero length string
} else {
bytes := n.Bytes()
if len(bytes) > 0 && bytes[0]&0x80 != 0 {
// We'll have to pad this with a 0x00 in order to
// stop it looking like a negative number.
to[0] = 0
to = to[1:]
length++
}
nBytes := copy(to, bytes)
to = to[nBytes:]
length += nBytes
}
lengthBytes[0] = byte(length >> 24)
lengthBytes[1] = byte(length >> 16)
lengthBytes[2] = byte(length >> 8)
lengthBytes[3] = byte(length)
return to
}
func writeInt(w io.Writer, n *big.Int) {
length := intLength(n)
buf := make([]byte, length)
marshalInt(buf, n)
w.Write(buf)
}
func writeString(w io.Writer, s []byte) {
var lengthBytes [4]byte
lengthBytes[0] = byte(len(s) >> 24)
lengthBytes[1] = byte(len(s) >> 16)
lengthBytes[2] = byte(len(s) >> 8)
lengthBytes[3] = byte(len(s))
w.Write(lengthBytes[:])
w.Write(s)
}
func stringLength(s []byte) int {
return 4 + len(s)
}
func marshalString(to []byte, s []byte) []byte {
to[0] = byte(len(s) >> 24)
to[1] = byte(len(s) >> 16)
to[2] = byte(len(s) >> 8)
to[3] = byte(len(s))
to = to[4:]
copy(to, s)
return to[len(s):]
}
var bigIntType = reflect.TypeOf((*big.Int)(nil))
// Decode a packet into it's corresponding message.
func decode(packet []byte) interface{} {
var msg interface{}
switch packet[0] {
case msgDisconnect:
msg = new(disconnectMsg)
case msgServiceRequest:
msg = new(serviceRequestMsg)
case msgServiceAccept:
msg = new(serviceAcceptMsg)
case msgKexInit:
msg = new(kexInitMsg)
case msgKexDHInit:
msg = new(kexDHInitMsg)
case msgKexDHReply:
msg = new(kexDHReplyMsg)
case msgUserAuthRequest:
msg = new(userAuthRequestMsg)
case msgUserAuthFailure:
msg = new(userAuthFailureMsg)
case msgUserAuthPubKeyOk:
msg = new(userAuthPubKeyOkMsg)
case msgGlobalRequest:
msg = new(globalRequestMsg)
case msgRequestSuccess:
msg = new(channelRequestSuccessMsg)
case msgRequestFailure:
msg = new(channelRequestFailureMsg)
case msgChannelOpen:
msg = new(channelOpenMsg)
case msgChannelOpenConfirm:
msg = new(channelOpenConfirmMsg)
case msgChannelOpenFailure:
msg = new(channelOpenFailureMsg)
case msgChannelWindowAdjust:
msg = new(windowAdjustMsg)
case msgChannelEOF:
msg = new(channelEOFMsg)
case msgChannelClose:
msg = new(channelCloseMsg)
case msgChannelRequest:
msg = new(channelRequestMsg)
case msgChannelSuccess:
msg = new(channelRequestSuccessMsg)
case msgChannelFailure:
msg = new(channelRequestFailureMsg)
default:
return UnexpectedMessageError{0, packet[0]}
}
if err := unmarshal(msg, packet, packet[0]); err != nil {
return err
}
return msg
}
|