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Diffstat (limited to 'vendor/golang.org/x/crypto/ssh/transport.go')
-rw-r--r-- | vendor/golang.org/x/crypto/ssh/transport.go | 353 |
1 files changed, 353 insertions, 0 deletions
diff --git a/vendor/golang.org/x/crypto/ssh/transport.go b/vendor/golang.org/x/crypto/ssh/transport.go new file mode 100644 index 000000000..f6fae1db4 --- /dev/null +++ b/vendor/golang.org/x/crypto/ssh/transport.go @@ -0,0 +1,353 @@ +// 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 ( + "bufio" + "bytes" + "errors" + "io" + "log" +) + +// debugTransport if set, will print packet types as they go over the +// wire. No message decoding is done, to minimize the impact on timing. +const debugTransport = false + +const ( + gcmCipherID = "aes128-gcm@openssh.com" + aes128cbcID = "aes128-cbc" + tripledescbcID = "3des-cbc" +) + +// packetConn represents a transport that implements packet based +// operations. +type packetConn interface { + // Encrypt and send a packet of data to the remote peer. + writePacket(packet []byte) error + + // Read a packet from the connection. The read is blocking, + // i.e. if error is nil, then the returned byte slice is + // always non-empty. + readPacket() ([]byte, error) + + // Close closes the write-side of the connection. + Close() error +} + +// transport is the keyingTransport that implements the SSH packet +// protocol. +type transport struct { + reader connectionState + writer connectionState + + bufReader *bufio.Reader + bufWriter *bufio.Writer + rand io.Reader + isClient bool + io.Closer +} + +// packetCipher represents a combination of SSH encryption/MAC +// protocol. A single instance should be used for one direction only. +type packetCipher interface { + // writePacket encrypts the packet and writes it to w. The + // contents of the packet are generally scrambled. + writePacket(seqnum uint32, w io.Writer, rand io.Reader, packet []byte) error + + // readPacket reads and decrypts a packet of data. The + // returned packet may be overwritten by future calls of + // readPacket. + readPacket(seqnum uint32, r io.Reader) ([]byte, error) +} + +// connectionState represents one side (read or write) of the +// connection. This is necessary because each direction has its own +// keys, and can even have its own algorithms +type connectionState struct { + packetCipher + seqNum uint32 + dir direction + pendingKeyChange chan packetCipher +} + +// prepareKeyChange sets up key material for a keychange. The key changes in +// both directions are triggered by reading and writing a msgNewKey packet +// respectively. +func (t *transport) prepareKeyChange(algs *algorithms, kexResult *kexResult) error { + ciph, err := newPacketCipher(t.reader.dir, algs.r, kexResult) + if err != nil { + return err + } + t.reader.pendingKeyChange <- ciph + + ciph, err = newPacketCipher(t.writer.dir, algs.w, kexResult) + if err != nil { + return err + } + t.writer.pendingKeyChange <- ciph + + return nil +} + +func (t *transport) printPacket(p []byte, write bool) { + if len(p) == 0 { + return + } + who := "server" + if t.isClient { + who = "client" + } + what := "read" + if write { + what = "write" + } + + log.Println(what, who, p[0]) +} + +// Read and decrypt next packet. +func (t *transport) readPacket() (p []byte, err error) { + for { + p, err = t.reader.readPacket(t.bufReader) + if err != nil { + break + } + if len(p) == 0 || (p[0] != msgIgnore && p[0] != msgDebug) { + break + } + } + if debugTransport { + t.printPacket(p, false) + } + + return p, err +} + +func (s *connectionState) readPacket(r *bufio.Reader) ([]byte, error) { + packet, err := s.packetCipher.readPacket(s.seqNum, r) + s.seqNum++ + if err == nil && len(packet) == 0 { + err = errors.New("ssh: zero length packet") + } + + if len(packet) > 0 { + switch packet[0] { + case msgNewKeys: + select { + case cipher := <-s.pendingKeyChange: + s.packetCipher = cipher + default: + return nil, errors.New("ssh: got bogus newkeys message") + } + + case msgDisconnect: + // Transform a disconnect message into an + // error. Since this is lowest level at which + // we interpret message types, doing it here + // ensures that we don't have to handle it + // elsewhere. + var msg disconnectMsg + if err := Unmarshal(packet, &msg); err != nil { + return nil, err + } + return nil, &msg + } + } + + // The packet may point to an internal buffer, so copy the + // packet out here. + fresh := make([]byte, len(packet)) + copy(fresh, packet) + + return fresh, err +} + +func (t *transport) writePacket(packet []byte) error { + if debugTransport { + t.printPacket(packet, true) + } + return t.writer.writePacket(t.bufWriter, t.rand, packet) +} + +func (s *connectionState) writePacket(w *bufio.Writer, rand io.Reader, packet []byte) error { + changeKeys := len(packet) > 0 && packet[0] == msgNewKeys + + err := s.packetCipher.writePacket(s.seqNum, w, rand, packet) + if err != nil { + return err + } + if err = w.Flush(); err != nil { + return err + } + s.seqNum++ + if changeKeys { + select { + case cipher := <-s.pendingKeyChange: + s.packetCipher = cipher + default: + panic("ssh: no key material for msgNewKeys") + } + } + return err +} + +func newTransport(rwc io.ReadWriteCloser, rand io.Reader, isClient bool) *transport { + t := &transport{ + bufReader: bufio.NewReader(rwc), + bufWriter: bufio.NewWriter(rwc), + rand: rand, + reader: connectionState{ + packetCipher: &streamPacketCipher{cipher: noneCipher{}}, + pendingKeyChange: make(chan packetCipher, 1), + }, + writer: connectionState{ + packetCipher: &streamPacketCipher{cipher: noneCipher{}}, + pendingKeyChange: make(chan packetCipher, 1), + }, + Closer: rwc, + } + t.isClient = isClient + + if isClient { + t.reader.dir = serverKeys + t.writer.dir = clientKeys + } else { + t.reader.dir = clientKeys + t.writer.dir = serverKeys + } + + return t +} + +type direction struct { + ivTag []byte + keyTag []byte + macKeyTag []byte +} + +var ( + serverKeys = direction{[]byte{'B'}, []byte{'D'}, []byte{'F'}} + clientKeys = direction{[]byte{'A'}, []byte{'C'}, []byte{'E'}} +) + +// setupKeys sets the cipher and MAC keys from kex.K, kex.H and sessionId, as +// described in RFC 4253, section 6.4. direction should either be serverKeys +// (to setup server->client keys) or clientKeys (for client->server keys). +func newPacketCipher(d direction, algs directionAlgorithms, kex *kexResult) (packetCipher, error) { + cipherMode := cipherModes[algs.Cipher] + macMode := macModes[algs.MAC] + + iv := make([]byte, cipherMode.ivSize) + key := make([]byte, cipherMode.keySize) + macKey := make([]byte, macMode.keySize) + + generateKeyMaterial(iv, d.ivTag, kex) + generateKeyMaterial(key, d.keyTag, kex) + generateKeyMaterial(macKey, d.macKeyTag, kex) + + return cipherModes[algs.Cipher].create(key, iv, macKey, algs) +} + +// generateKeyMaterial fills out with key material generated from tag, K, H +// and sessionId, as specified in RFC 4253, section 7.2. +func generateKeyMaterial(out, tag []byte, r *kexResult) { + var digestsSoFar []byte + + h := r.Hash.New() + for len(out) > 0 { + h.Reset() + h.Write(r.K) + h.Write(r.H) + + if len(digestsSoFar) == 0 { + h.Write(tag) + h.Write(r.SessionID) + } else { + h.Write(digestsSoFar) + } + + digest := h.Sum(nil) + n := copy(out, digest) + out = out[n:] + if len(out) > 0 { + digestsSoFar = append(digestsSoFar, digest...) + } + } +} + +const packageVersion = "SSH-2.0-Go" + +// Sends and receives a version line. The versionLine string should +// be US ASCII, start with "SSH-2.0-", and should not include a +// newline. exchangeVersions returns the other side's version line. +func exchangeVersions(rw io.ReadWriter, versionLine []byte) (them []byte, err error) { + // Contrary to the RFC, we do not ignore lines that don't + // start with "SSH-2.0-" to make the library usable with + // nonconforming servers. + for _, c := range versionLine { + // The spec disallows non US-ASCII chars, and + // specifically forbids null chars. + if c < 32 { + return nil, errors.New("ssh: junk character in version line") + } + } + if _, err = rw.Write(append(versionLine, '\r', '\n')); err != nil { + return + } + + them, err = readVersion(rw) + return them, err +} + +// maxVersionStringBytes is the maximum number of bytes that we'll +// accept as a version string. RFC 4253 section 4.2 limits this at 255 +// chars +const maxVersionStringBytes = 255 + +// Read version string as specified by RFC 4253, section 4.2. +func readVersion(r io.Reader) ([]byte, error) { + versionString := make([]byte, 0, 64) + var ok bool + var buf [1]byte + + for length := 0; length < maxVersionStringBytes; length++ { + _, err := io.ReadFull(r, buf[:]) + if err != nil { + return nil, err + } + // The RFC says that the version should be terminated with \r\n + // but several SSH servers actually only send a \n. + if buf[0] == '\n' { + if !bytes.HasPrefix(versionString, []byte("SSH-")) { + // RFC 4253 says we need to ignore all version string lines + // except the one containing the SSH version (provided that + // all the lines do not exceed 255 bytes in total). + versionString = versionString[:0] + continue + } + ok = true + break + } + + // non ASCII chars are disallowed, but we are lenient, + // since Go doesn't use null-terminated strings. + + // The RFC allows a comment after a space, however, + // all of it (version and comments) goes into the + // session hash. + versionString = append(versionString, buf[0]) + } + + if !ok { + return nil, errors.New("ssh: overflow reading version string") + } + + // There might be a '\r' on the end which we should remove. + if len(versionString) > 0 && versionString[len(versionString)-1] == '\r' { + versionString = versionString[:len(versionString)-1] + } + return versionString, nil +} |