feat(dir2config): defaults
This commit is contained in:
Mikaël Cluseau
353
vendor/golang.org/x/crypto/ssh/transport.go
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vendored
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353
vendor/golang.org/x/crypto/ssh/transport.go
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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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"bufio"
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"bytes"
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"errors"
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"io"
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"log"
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)
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// debugTransport if set, will print packet types as they go over the
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// wire. No message decoding is done, to minimize the impact on timing.
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const debugTransport = false
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const (
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gcmCipherID = "aes128-gcm@openssh.com"
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aes128cbcID = "aes128-cbc"
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tripledescbcID = "3des-cbc"
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)
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// packetConn represents a transport that implements packet based
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// operations.
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type packetConn interface {
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// Encrypt and send a packet of data to the remote peer.
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writePacket(packet []byte) error
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// Read a packet from the connection. The read is blocking,
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// i.e. if error is nil, then the returned byte slice is
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// always non-empty.
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readPacket() ([]byte, error)
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// Close closes the write-side of the connection.
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Close() error
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}
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// transport is the keyingTransport that implements the SSH packet
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// protocol.
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type transport struct {
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reader connectionState
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writer connectionState
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bufReader *bufio.Reader
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bufWriter *bufio.Writer
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rand io.Reader
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isClient bool
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io.Closer
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}
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// packetCipher represents a combination of SSH encryption/MAC
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// protocol. A single instance should be used for one direction only.
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type packetCipher interface {
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// writePacket encrypts the packet and writes it to w. The
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// contents of the packet are generally scrambled.
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writePacket(seqnum uint32, w io.Writer, rand io.Reader, packet []byte) error
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// readPacket reads and decrypts a packet of data. The
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// returned packet may be overwritten by future calls of
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// readPacket.
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readPacket(seqnum uint32, r io.Reader) ([]byte, error)
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}
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// connectionState represents one side (read or write) of the
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// connection. This is necessary because each direction has its own
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// keys, and can even have its own algorithms
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type connectionState struct {
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packetCipher
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seqNum uint32
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dir direction
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pendingKeyChange chan packetCipher
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}
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// prepareKeyChange sets up key material for a keychange. The key changes in
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// both directions are triggered by reading and writing a msgNewKey packet
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// respectively.
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func (t *transport) prepareKeyChange(algs *algorithms, kexResult *kexResult) error {
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ciph, err := newPacketCipher(t.reader.dir, algs.r, kexResult)
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if err != nil {
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return err
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}
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t.reader.pendingKeyChange <- ciph
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ciph, err = newPacketCipher(t.writer.dir, algs.w, kexResult)
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if err != nil {
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return err
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}
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t.writer.pendingKeyChange <- ciph
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return nil
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}
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func (t *transport) printPacket(p []byte, write bool) {
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if len(p) == 0 {
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return
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}
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who := "server"
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if t.isClient {
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who = "client"
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}
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what := "read"
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if write {
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what = "write"
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}
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log.Println(what, who, p[0])
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}
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// Read and decrypt next packet.
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func (t *transport) readPacket() (p []byte, err error) {
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for {
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p, err = t.reader.readPacket(t.bufReader)
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if err != nil {
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break
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}
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if len(p) == 0 || (p[0] != msgIgnore && p[0] != msgDebug) {
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break
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}
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}
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if debugTransport {
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t.printPacket(p, false)
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}
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return p, err
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}
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func (s *connectionState) readPacket(r *bufio.Reader) ([]byte, error) {
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packet, err := s.packetCipher.readPacket(s.seqNum, r)
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s.seqNum++
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if err == nil && len(packet) == 0 {
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err = errors.New("ssh: zero length packet")
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}
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if len(packet) > 0 {
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switch packet[0] {
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case msgNewKeys:
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select {
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case cipher := <-s.pendingKeyChange:
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s.packetCipher = cipher
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default:
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return nil, errors.New("ssh: got bogus newkeys message")
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}
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case msgDisconnect:
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// Transform a disconnect message into an
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// error. Since this is lowest level at which
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// we interpret message types, doing it here
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// ensures that we don't have to handle it
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// elsewhere.
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var msg disconnectMsg
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if err := Unmarshal(packet, &msg); err != nil {
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return nil, err
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}
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return nil, &msg
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}
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}
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// The packet may point to an internal buffer, so copy the
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// packet out here.
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fresh := make([]byte, len(packet))
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copy(fresh, packet)
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return fresh, err
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}
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func (t *transport) writePacket(packet []byte) error {
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if debugTransport {
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t.printPacket(packet, true)
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}
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return t.writer.writePacket(t.bufWriter, t.rand, packet)
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}
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func (s *connectionState) writePacket(w *bufio.Writer, rand io.Reader, packet []byte) error {
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changeKeys := len(packet) > 0 && packet[0] == msgNewKeys
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err := s.packetCipher.writePacket(s.seqNum, w, rand, packet)
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if err != nil {
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return err
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}
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if err = w.Flush(); err != nil {
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return err
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}
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s.seqNum++
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if changeKeys {
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select {
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case cipher := <-s.pendingKeyChange:
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s.packetCipher = cipher
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default:
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panic("ssh: no key material for msgNewKeys")
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}
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}
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return err
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}
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func newTransport(rwc io.ReadWriteCloser, rand io.Reader, isClient bool) *transport {
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t := &transport{
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bufReader: bufio.NewReader(rwc),
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bufWriter: bufio.NewWriter(rwc),
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rand: rand,
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reader: connectionState{
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packetCipher: &streamPacketCipher{cipher: noneCipher{}},
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pendingKeyChange: make(chan packetCipher, 1),
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},
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writer: connectionState{
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packetCipher: &streamPacketCipher{cipher: noneCipher{}},
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pendingKeyChange: make(chan packetCipher, 1),
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},
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Closer: rwc,
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}
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t.isClient = isClient
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if isClient {
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t.reader.dir = serverKeys
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t.writer.dir = clientKeys
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} else {
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t.reader.dir = clientKeys
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t.writer.dir = serverKeys
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}
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return t
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}
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type direction struct {
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ivTag []byte
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keyTag []byte
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macKeyTag []byte
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}
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var (
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serverKeys = direction{[]byte{'B'}, []byte{'D'}, []byte{'F'}}
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clientKeys = direction{[]byte{'A'}, []byte{'C'}, []byte{'E'}}
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)
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// setupKeys sets the cipher and MAC keys from kex.K, kex.H and sessionId, as
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// described in RFC 4253, section 6.4. direction should either be serverKeys
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// (to setup server->client keys) or clientKeys (for client->server keys).
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func newPacketCipher(d direction, algs directionAlgorithms, kex *kexResult) (packetCipher, error) {
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cipherMode := cipherModes[algs.Cipher]
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macMode := macModes[algs.MAC]
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iv := make([]byte, cipherMode.ivSize)
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key := make([]byte, cipherMode.keySize)
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macKey := make([]byte, macMode.keySize)
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generateKeyMaterial(iv, d.ivTag, kex)
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generateKeyMaterial(key, d.keyTag, kex)
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generateKeyMaterial(macKey, d.macKeyTag, kex)
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return cipherModes[algs.Cipher].create(key, iv, macKey, algs)
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}
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// generateKeyMaterial fills out with key material generated from tag, K, H
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// and sessionId, as specified in RFC 4253, section 7.2.
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func generateKeyMaterial(out, tag []byte, r *kexResult) {
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var digestsSoFar []byte
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h := r.Hash.New()
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for len(out) > 0 {
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h.Reset()
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h.Write(r.K)
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h.Write(r.H)
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if len(digestsSoFar) == 0 {
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h.Write(tag)
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h.Write(r.SessionID)
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} else {
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h.Write(digestsSoFar)
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}
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digest := h.Sum(nil)
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n := copy(out, digest)
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out = out[n:]
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if len(out) > 0 {
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digestsSoFar = append(digestsSoFar, digest...)
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}
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}
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}
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const packageVersion = "SSH-2.0-Go"
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// Sends and receives a version line. The versionLine string should
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// be US ASCII, start with "SSH-2.0-", and should not include a
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// newline. exchangeVersions returns the other side's version line.
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func exchangeVersions(rw io.ReadWriter, versionLine []byte) (them []byte, err error) {
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// Contrary to the RFC, we do not ignore lines that don't
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// start with "SSH-2.0-" to make the library usable with
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// nonconforming servers.
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for _, c := range versionLine {
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// The spec disallows non US-ASCII chars, and
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// specifically forbids null chars.
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if c < 32 {
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return nil, errors.New("ssh: junk character in version line")
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}
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}
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if _, err = rw.Write(append(versionLine, '\r', '\n')); err != nil {
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return
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}
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them, err = readVersion(rw)
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return them, err
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}
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// maxVersionStringBytes is the maximum number of bytes that we'll
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// accept as a version string. RFC 4253 section 4.2 limits this at 255
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// chars
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const maxVersionStringBytes = 255
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// Read version string as specified by RFC 4253, section 4.2.
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func readVersion(r io.Reader) ([]byte, error) {
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versionString := make([]byte, 0, 64)
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var ok bool
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var buf [1]byte
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for length := 0; length < maxVersionStringBytes; length++ {
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_, err := io.ReadFull(r, buf[:])
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if err != nil {
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return nil, err
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}
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// The RFC says that the version should be terminated with \r\n
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// but several SSH servers actually only send a \n.
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if buf[0] == '\n' {
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if !bytes.HasPrefix(versionString, []byte("SSH-")) {
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// RFC 4253 says we need to ignore all version string lines
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// except the one containing the SSH version (provided that
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// all the lines do not exceed 255 bytes in total).
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versionString = versionString[:0]
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continue
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}
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ok = true
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break
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}
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// non ASCII chars are disallowed, but we are lenient,
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// since Go doesn't use null-terminated strings.
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// The RFC allows a comment after a space, however,
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// all of it (version and comments) goes into the
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// session hash.
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versionString = append(versionString, buf[0])
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}
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if !ok {
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return nil, errors.New("ssh: overflow reading version string")
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}
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// There might be a '\r' on the end which we should remove.
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if len(versionString) > 0 && versionString[len(versionString)-1] == '\r' {
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versionString = versionString[:len(versionString)-1]
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}
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return versionString, nil
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}
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