From bae9f6d2fd5eb5bc80929bd393932b23f14d7c93 Mon Sep 17 00:00:00 2001 From: Jake Champlin Date: Tue, 6 Jun 2017 12:40:07 -0400 Subject: Initial transfer of provider code --- vendor/golang.org/x/crypto/ssh/handshake.go | 625 ++++++++++++++++++++++++++++ 1 file changed, 625 insertions(+) create mode 100644 vendor/golang.org/x/crypto/ssh/handshake.go (limited to 'vendor/golang.org/x/crypto/ssh/handshake.go') diff --git a/vendor/golang.org/x/crypto/ssh/handshake.go b/vendor/golang.org/x/crypto/ssh/handshake.go new file mode 100644 index 0000000..8de6506 --- /dev/null +++ b/vendor/golang.org/x/crypto/ssh/handshake.go @@ -0,0 +1,625 @@ +// Copyright 2013 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 ( + "crypto/rand" + "errors" + "fmt" + "io" + "log" + "net" + "sync" +) + +// debugHandshake, if set, prints messages sent and received. Key +// exchange messages are printed as if DH were used, so the debug +// messages are wrong when using ECDH. +const debugHandshake = false + +// chanSize sets the amount of buffering SSH connections. This is +// primarily for testing: setting chanSize=0 uncovers deadlocks more +// quickly. +const chanSize = 16 + +// keyingTransport is a packet based transport that supports key +// changes. It need not be thread-safe. It should pass through +// msgNewKeys in both directions. +type keyingTransport interface { + packetConn + + // prepareKeyChange sets up a key change. The key change for a + // direction will be effected if a msgNewKeys message is sent + // or received. + prepareKeyChange(*algorithms, *kexResult) error +} + +// handshakeTransport implements rekeying on top of a keyingTransport +// and offers a thread-safe writePacket() interface. +type handshakeTransport struct { + conn keyingTransport + config *Config + + serverVersion []byte + clientVersion []byte + + // hostKeys is non-empty if we are the server. In that case, + // it contains all host keys that can be used to sign the + // connection. + hostKeys []Signer + + // hostKeyAlgorithms is non-empty if we are the client. In that case, + // we accept these key types from the server as host key. + hostKeyAlgorithms []string + + // On read error, incoming is closed, and readError is set. + incoming chan []byte + readError error + + mu sync.Mutex + writeError error + sentInitPacket []byte + sentInitMsg *kexInitMsg + pendingPackets [][]byte // Used when a key exchange is in progress. + + // If the read loop wants to schedule a kex, it pings this + // channel, and the write loop will send out a kex + // message. + requestKex chan struct{} + + // If the other side requests or confirms a kex, its kexInit + // packet is sent here for the write loop to find it. + startKex chan *pendingKex + + // data for host key checking + hostKeyCallback func(hostname string, remote net.Addr, key PublicKey) error + dialAddress string + remoteAddr net.Addr + + // Algorithms agreed in the last key exchange. + algorithms *algorithms + + readPacketsLeft uint32 + readBytesLeft int64 + + writePacketsLeft uint32 + writeBytesLeft int64 + + // The session ID or nil if first kex did not complete yet. + sessionID []byte +} + +type pendingKex struct { + otherInit []byte + done chan error +} + +func newHandshakeTransport(conn keyingTransport, config *Config, clientVersion, serverVersion []byte) *handshakeTransport { + t := &handshakeTransport{ + conn: conn, + serverVersion: serverVersion, + clientVersion: clientVersion, + incoming: make(chan []byte, chanSize), + requestKex: make(chan struct{}, 1), + startKex: make(chan *pendingKex, 1), + + config: config, + } + + // We always start with a mandatory key exchange. + t.requestKex <- struct{}{} + return t +} + +func newClientTransport(conn keyingTransport, clientVersion, serverVersion []byte, config *ClientConfig, dialAddr string, addr net.Addr) *handshakeTransport { + t := newHandshakeTransport(conn, &config.Config, clientVersion, serverVersion) + t.dialAddress = dialAddr + t.remoteAddr = addr + t.hostKeyCallback = config.HostKeyCallback + if config.HostKeyAlgorithms != nil { + t.hostKeyAlgorithms = config.HostKeyAlgorithms + } else { + t.hostKeyAlgorithms = supportedHostKeyAlgos + } + go t.readLoop() + go t.kexLoop() + return t +} + +func newServerTransport(conn keyingTransport, clientVersion, serverVersion []byte, config *ServerConfig) *handshakeTransport { + t := newHandshakeTransport(conn, &config.Config, clientVersion, serverVersion) + t.hostKeys = config.hostKeys + go t.readLoop() + go t.kexLoop() + return t +} + +func (t *handshakeTransport) getSessionID() []byte { + return t.sessionID +} + +// waitSession waits for the session to be established. This should be +// the first thing to call after instantiating handshakeTransport. +func (t *handshakeTransport) waitSession() error { + p, err := t.readPacket() + if err != nil { + return err + } + if p[0] != msgNewKeys { + return fmt.Errorf("ssh: first packet should be msgNewKeys") + } + + return nil +} + +func (t *handshakeTransport) id() string { + if len(t.hostKeys) > 0 { + return "server" + } + return "client" +} + +func (t *handshakeTransport) printPacket(p []byte, write bool) { + action := "got" + if write { + action = "sent" + } + + if p[0] == msgChannelData || p[0] == msgChannelExtendedData { + log.Printf("%s %s data (packet %d bytes)", t.id(), action, len(p)) + } else { + msg, err := decode(p) + log.Printf("%s %s %T %v (%v)", t.id(), action, msg, msg, err) + } +} + +func (t *handshakeTransport) readPacket() ([]byte, error) { + p, ok := <-t.incoming + if !ok { + return nil, t.readError + } + return p, nil +} + +func (t *handshakeTransport) readLoop() { + first := true + for { + p, err := t.readOnePacket(first) + first = false + if err != nil { + t.readError = err + close(t.incoming) + break + } + if p[0] == msgIgnore || p[0] == msgDebug { + continue + } + t.incoming <- p + } + + // Stop writers too. + t.recordWriteError(t.readError) + + // Unblock the writer should it wait for this. + close(t.startKex) + + // Don't close t.requestKex; it's also written to from writePacket. +} + +func (t *handshakeTransport) pushPacket(p []byte) error { + if debugHandshake { + t.printPacket(p, true) + } + return t.conn.writePacket(p) +} + +func (t *handshakeTransport) getWriteError() error { + t.mu.Lock() + defer t.mu.Unlock() + return t.writeError +} + +func (t *handshakeTransport) recordWriteError(err error) { + t.mu.Lock() + defer t.mu.Unlock() + if t.writeError == nil && err != nil { + t.writeError = err + } +} + +func (t *handshakeTransport) requestKeyExchange() { + select { + case t.requestKex <- struct{}{}: + default: + // something already requested a kex, so do nothing. + } +} + +func (t *handshakeTransport) kexLoop() { + +write: + for t.getWriteError() == nil { + var request *pendingKex + var sent bool + + for request == nil || !sent { + var ok bool + select { + case request, ok = <-t.startKex: + if !ok { + break write + } + case <-t.requestKex: + break + } + + if !sent { + if err := t.sendKexInit(); err != nil { + t.recordWriteError(err) + break + } + sent = true + } + } + + if err := t.getWriteError(); err != nil { + if request != nil { + request.done <- err + } + break + } + + // We're not servicing t.requestKex, but that is OK: + // we never block on sending to t.requestKex. + + // We're not servicing t.startKex, but the remote end + // has just sent us a kexInitMsg, so it can't send + // another key change request, until we close the done + // channel on the pendingKex request. + + err := t.enterKeyExchange(request.otherInit) + + t.mu.Lock() + t.writeError = err + t.sentInitPacket = nil + t.sentInitMsg = nil + t.writePacketsLeft = packetRekeyThreshold + if t.config.RekeyThreshold > 0 { + t.writeBytesLeft = int64(t.config.RekeyThreshold) + } else if t.algorithms != nil { + t.writeBytesLeft = t.algorithms.w.rekeyBytes() + } + + // we have completed the key exchange. Since the + // reader is still blocked, it is safe to clear out + // the requestKex channel. This avoids the situation + // where: 1) we consumed our own request for the + // initial kex, and 2) the kex from the remote side + // caused another send on the requestKex channel, + clear: + for { + select { + case <-t.requestKex: + // + default: + break clear + } + } + + request.done <- t.writeError + + // kex finished. Push packets that we received while + // the kex was in progress. Don't look at t.startKex + // and don't increment writtenSinceKex: if we trigger + // another kex while we are still busy with the last + // one, things will become very confusing. + for _, p := range t.pendingPackets { + t.writeError = t.pushPacket(p) + if t.writeError != nil { + break + } + } + t.pendingPackets = t.pendingPackets[:0] + t.mu.Unlock() + } + + // drain startKex channel. We don't service t.requestKex + // because nobody does blocking sends there. + go func() { + for init := range t.startKex { + init.done <- t.writeError + } + }() + + // Unblock reader. + t.conn.Close() +} + +// The protocol uses uint32 for packet counters, so we can't let them +// reach 1<<32. We will actually read and write more packets than +// this, though: the other side may send more packets, and after we +// hit this limit on writing we will send a few more packets for the +// key exchange itself. +const packetRekeyThreshold = (1 << 31) + +func (t *handshakeTransport) readOnePacket(first bool) ([]byte, error) { + p, err := t.conn.readPacket() + if err != nil { + return nil, err + } + + if t.readPacketsLeft > 0 { + t.readPacketsLeft-- + } else { + t.requestKeyExchange() + } + + if t.readBytesLeft > 0 { + t.readBytesLeft -= int64(len(p)) + } else { + t.requestKeyExchange() + } + + if debugHandshake { + t.printPacket(p, false) + } + + if first && p[0] != msgKexInit { + return nil, fmt.Errorf("ssh: first packet should be msgKexInit") + } + + if p[0] != msgKexInit { + return p, nil + } + + firstKex := t.sessionID == nil + + kex := pendingKex{ + done: make(chan error, 1), + otherInit: p, + } + t.startKex <- &kex + err = <-kex.done + + if debugHandshake { + log.Printf("%s exited key exchange (first %v), err %v", t.id(), firstKex, err) + } + + if err != nil { + return nil, err + } + + t.readPacketsLeft = packetRekeyThreshold + if t.config.RekeyThreshold > 0 { + t.readBytesLeft = int64(t.config.RekeyThreshold) + } else { + t.readBytesLeft = t.algorithms.r.rekeyBytes() + } + + // By default, a key exchange is hidden from higher layers by + // translating it into msgIgnore. + successPacket := []byte{msgIgnore} + if firstKex { + // sendKexInit() for the first kex waits for + // msgNewKeys so the authentication process is + // guaranteed to happen over an encrypted transport. + successPacket = []byte{msgNewKeys} + } + + return successPacket, nil +} + +// sendKexInit sends a key change message. +func (t *handshakeTransport) sendKexInit() error { + t.mu.Lock() + defer t.mu.Unlock() + if t.sentInitMsg != nil { + // kexInits may be sent either in response to the other side, + // or because our side wants to initiate a key change, so we + // may have already sent a kexInit. In that case, don't send a + // second kexInit. + return nil + } + + msg := &kexInitMsg{ + KexAlgos: t.config.KeyExchanges, + CiphersClientServer: t.config.Ciphers, + CiphersServerClient: t.config.Ciphers, + MACsClientServer: t.config.MACs, + MACsServerClient: t.config.MACs, + CompressionClientServer: supportedCompressions, + CompressionServerClient: supportedCompressions, + } + io.ReadFull(rand.Reader, msg.Cookie[:]) + + if len(t.hostKeys) > 0 { + for _, k := range t.hostKeys { + msg.ServerHostKeyAlgos = append( + msg.ServerHostKeyAlgos, k.PublicKey().Type()) + } + } else { + msg.ServerHostKeyAlgos = t.hostKeyAlgorithms + } + packet := Marshal(msg) + + // writePacket destroys the contents, so save a copy. + packetCopy := make([]byte, len(packet)) + copy(packetCopy, packet) + + if err := t.pushPacket(packetCopy); err != nil { + return err + } + + t.sentInitMsg = msg + t.sentInitPacket = packet + + return nil +} + +func (t *handshakeTransport) writePacket(p []byte) error { + switch p[0] { + case msgKexInit: + return errors.New("ssh: only handshakeTransport can send kexInit") + case msgNewKeys: + return errors.New("ssh: only handshakeTransport can send newKeys") + } + + t.mu.Lock() + defer t.mu.Unlock() + if t.writeError != nil { + return t.writeError + } + + if t.sentInitMsg != nil { + // Copy the packet so the writer can reuse the buffer. + cp := make([]byte, len(p)) + copy(cp, p) + t.pendingPackets = append(t.pendingPackets, cp) + return nil + } + + if t.writeBytesLeft > 0 { + t.writeBytesLeft -= int64(len(p)) + } else { + t.requestKeyExchange() + } + + if t.writePacketsLeft > 0 { + t.writePacketsLeft-- + } else { + t.requestKeyExchange() + } + + if err := t.pushPacket(p); err != nil { + t.writeError = err + } + + return nil +} + +func (t *handshakeTransport) Close() error { + return t.conn.Close() +} + +func (t *handshakeTransport) enterKeyExchange(otherInitPacket []byte) error { + if debugHandshake { + log.Printf("%s entered key exchange", t.id()) + } + + otherInit := &kexInitMsg{} + if err := Unmarshal(otherInitPacket, otherInit); err != nil { + return err + } + + magics := handshakeMagics{ + clientVersion: t.clientVersion, + serverVersion: t.serverVersion, + clientKexInit: otherInitPacket, + serverKexInit: t.sentInitPacket, + } + + clientInit := otherInit + serverInit := t.sentInitMsg + if len(t.hostKeys) == 0 { + clientInit, serverInit = serverInit, clientInit + + magics.clientKexInit = t.sentInitPacket + magics.serverKexInit = otherInitPacket + } + + var err error + t.algorithms, err = findAgreedAlgorithms(clientInit, serverInit) + if err != nil { + return err + } + + // We don't send FirstKexFollows, but we handle receiving it. + // + // RFC 4253 section 7 defines the kex and the agreement method for + // first_kex_packet_follows. It states that the guessed packet + // should be ignored if the "kex algorithm and/or the host + // key algorithm is guessed wrong (server and client have + // different preferred algorithm), or if any of the other + // algorithms cannot be agreed upon". The other algorithms have + // already been checked above so the kex algorithm and host key + // algorithm are checked here. + if otherInit.FirstKexFollows && (clientInit.KexAlgos[0] != serverInit.KexAlgos[0] || clientInit.ServerHostKeyAlgos[0] != serverInit.ServerHostKeyAlgos[0]) { + // other side sent a kex message for the wrong algorithm, + // which we have to ignore. + if _, err := t.conn.readPacket(); err != nil { + return err + } + } + + kex, ok := kexAlgoMap[t.algorithms.kex] + if !ok { + return fmt.Errorf("ssh: unexpected key exchange algorithm %v", t.algorithms.kex) + } + + var result *kexResult + if len(t.hostKeys) > 0 { + result, err = t.server(kex, t.algorithms, &magics) + } else { + result, err = t.client(kex, t.algorithms, &magics) + } + + if err != nil { + return err + } + + if t.sessionID == nil { + t.sessionID = result.H + } + result.SessionID = t.sessionID + + t.conn.prepareKeyChange(t.algorithms, result) + if err = t.conn.writePacket([]byte{msgNewKeys}); err != nil { + return err + } + if packet, err := t.conn.readPacket(); err != nil { + return err + } else if packet[0] != msgNewKeys { + return unexpectedMessageError(msgNewKeys, packet[0]) + } + + return nil +} + +func (t *handshakeTransport) server(kex kexAlgorithm, algs *algorithms, magics *handshakeMagics) (*kexResult, error) { + var hostKey Signer + for _, k := range t.hostKeys { + if algs.hostKey == k.PublicKey().Type() { + hostKey = k + } + } + + r, err := kex.Server(t.conn, t.config.Rand, magics, hostKey) + return r, err +} + +func (t *handshakeTransport) client(kex kexAlgorithm, algs *algorithms, magics *handshakeMagics) (*kexResult, error) { + result, err := kex.Client(t.conn, t.config.Rand, magics) + if err != nil { + return nil, err + } + + hostKey, err := ParsePublicKey(result.HostKey) + if err != nil { + return nil, err + } + + if err := verifyHostKeySignature(hostKey, result); err != nil { + return nil, err + } + + if t.hostKeyCallback != nil { + err = t.hostKeyCallback(t.dialAddress, t.remoteAddr, hostKey) + if err != nil { + return nil, err + } + } + + return result, nil +} -- cgit v1.2.3