| // TLS low level connection and record layer |
| |
| package tls |
| |
| import ( |
| "bytes" |
| "crypto/subtle" |
| "crypto/x509" |
| "hash" |
| "io" |
| "net" |
| "os" |
| "sync" |
| ) |
| |
| // A Conn represents a secured connection. |
| // It implements the net.Conn interface. |
| type Conn struct { |
| // constant |
| conn net.Conn |
| isClient bool |
| |
| // constant after handshake; protected by handshakeMutex |
| handshakeMutex sync.Mutex // handshakeMutex < in.Mutex, out.Mutex, errMutex |
| vers uint16 // TLS version |
| haveVers bool // version has been negotiated |
| config *Config // configuration passed to constructor |
| handshakeComplete bool |
| cipherSuite uint16 |
| ocspResponse []byte // stapled OCSP response |
| peerCertificates []*x509.Certificate |
| |
| clientProtocol string |
| |
| // first permanent error |
| errMutex sync.Mutex |
| err os.Error |
| |
| // input/output |
| in, out halfConn // in.Mutex < out.Mutex |
| rawInput *block // raw input, right off the wire |
| input *block // application data waiting to be read |
| hand bytes.Buffer // handshake data waiting to be read |
| |
| tmp [16]byte |
| } |
| |
| func (c *Conn) setError(err os.Error) os.Error { |
| c.errMutex.Lock() |
| defer c.errMutex.Unlock() |
| |
| if c.err == nil { |
| c.err = err |
| } |
| return err |
| } |
| |
| func (c *Conn) error() os.Error { |
| c.errMutex.Lock() |
| defer c.errMutex.Unlock() |
| |
| return c.err |
| } |
| |
| // Access to net.Conn methods. |
| // Cannot just embed net.Conn because that would |
| // export the struct field too. |
| |
| // LocalAddr returns the local network address. |
| func (c *Conn) LocalAddr() net.Addr { |
| return c.conn.LocalAddr() |
| } |
| |
| // RemoteAddr returns the remote network address. |
| func (c *Conn) RemoteAddr() net.Addr { |
| return c.conn.RemoteAddr() |
| } |
| |
| // SetTimeout sets the read deadline associated with the connection. |
| // There is no write deadline. |
| func (c *Conn) SetTimeout(nsec int64) os.Error { |
| return c.conn.SetTimeout(nsec) |
| } |
| |
| // SetReadTimeout sets the time (in nanoseconds) that |
| // Read will wait for data before returning os.EAGAIN. |
| // Setting nsec == 0 (the default) disables the deadline. |
| func (c *Conn) SetReadTimeout(nsec int64) os.Error { |
| return c.conn.SetReadTimeout(nsec) |
| } |
| |
| // SetWriteTimeout exists to satisfy the net.Conn interface |
| // but is not implemented by TLS. It always returns an error. |
| func (c *Conn) SetWriteTimeout(nsec int64) os.Error { |
| return os.NewError("TLS does not support SetWriteTimeout") |
| } |
| |
| // A halfConn represents one direction of the record layer |
| // connection, either sending or receiving. |
| type halfConn struct { |
| sync.Mutex |
| crypt encryptor // encryption state |
| mac hash.Hash // MAC algorithm |
| seq [8]byte // 64-bit sequence number |
| bfree *block // list of free blocks |
| |
| nextCrypt encryptor // next encryption state |
| nextMac hash.Hash // next MAC algorithm |
| } |
| |
| // prepareCipherSpec sets the encryption and MAC states |
| // that a subsequent changeCipherSpec will use. |
| func (hc *halfConn) prepareCipherSpec(crypt encryptor, mac hash.Hash) { |
| hc.nextCrypt = crypt |
| hc.nextMac = mac |
| } |
| |
| // changeCipherSpec changes the encryption and MAC states |
| // to the ones previously passed to prepareCipherSpec. |
| func (hc *halfConn) changeCipherSpec() os.Error { |
| if hc.nextCrypt == nil { |
| return alertInternalError |
| } |
| hc.crypt = hc.nextCrypt |
| hc.mac = hc.nextMac |
| hc.nextCrypt = nil |
| hc.nextMac = nil |
| return nil |
| } |
| |
| // incSeq increments the sequence number. |
| func (hc *halfConn) incSeq() { |
| for i := 7; i >= 0; i-- { |
| hc.seq[i]++ |
| if hc.seq[i] != 0 { |
| return |
| } |
| } |
| |
| // Not allowed to let sequence number wrap. |
| // Instead, must renegotiate before it does. |
| // Not likely enough to bother. |
| panic("TLS: sequence number wraparound") |
| } |
| |
| // resetSeq resets the sequence number to zero. |
| func (hc *halfConn) resetSeq() { |
| for i := range hc.seq { |
| hc.seq[i] = 0 |
| } |
| } |
| |
| // decrypt checks and strips the mac and decrypts the data in b. |
| func (hc *halfConn) decrypt(b *block) (bool, alert) { |
| // pull out payload |
| payload := b.data[recordHeaderLen:] |
| |
| // decrypt |
| if hc.crypt != nil { |
| hc.crypt.XORKeyStream(payload) |
| } |
| |
| // check, strip mac |
| if hc.mac != nil { |
| if len(payload) < hc.mac.Size() { |
| return false, alertBadRecordMAC |
| } |
| |
| // strip mac off payload, b.data |
| n := len(payload) - hc.mac.Size() |
| b.data[3] = byte(n >> 8) |
| b.data[4] = byte(n) |
| b.data = b.data[0 : recordHeaderLen+n] |
| remoteMAC := payload[n:] |
| |
| hc.mac.Reset() |
| hc.mac.Write(hc.seq[0:]) |
| hc.incSeq() |
| hc.mac.Write(b.data) |
| |
| if subtle.ConstantTimeCompare(hc.mac.Sum(), remoteMAC) != 1 { |
| return false, alertBadRecordMAC |
| } |
| } |
| |
| return true, 0 |
| } |
| |
| // encrypt encrypts and macs the data in b. |
| func (hc *halfConn) encrypt(b *block) (bool, alert) { |
| // mac |
| if hc.mac != nil { |
| hc.mac.Reset() |
| hc.mac.Write(hc.seq[0:]) |
| hc.incSeq() |
| hc.mac.Write(b.data) |
| mac := hc.mac.Sum() |
| n := len(b.data) |
| b.resize(n + len(mac)) |
| copy(b.data[n:], mac) |
| |
| // update length to include mac |
| n = len(b.data) - recordHeaderLen |
| b.data[3] = byte(n >> 8) |
| b.data[4] = byte(n) |
| } |
| |
| // encrypt |
| if hc.crypt != nil { |
| hc.crypt.XORKeyStream(b.data[recordHeaderLen:]) |
| } |
| |
| return true, 0 |
| } |
| |
| // A block is a simple data buffer. |
| type block struct { |
| data []byte |
| off int // index for Read |
| link *block |
| } |
| |
| // resize resizes block to be n bytes, growing if necessary. |
| func (b *block) resize(n int) { |
| if n > cap(b.data) { |
| b.reserve(n) |
| } |
| b.data = b.data[0:n] |
| } |
| |
| // reserve makes sure that block contains a capacity of at least n bytes. |
| func (b *block) reserve(n int) { |
| if cap(b.data) >= n { |
| return |
| } |
| m := cap(b.data) |
| if m == 0 { |
| m = 1024 |
| } |
| for m < n { |
| m *= 2 |
| } |
| data := make([]byte, len(b.data), m) |
| copy(data, b.data) |
| b.data = data |
| } |
| |
| // readFromUntil reads from r into b until b contains at least n bytes |
| // or else returns an error. |
| func (b *block) readFromUntil(r io.Reader, n int) os.Error { |
| // quick case |
| if len(b.data) >= n { |
| return nil |
| } |
| |
| // read until have enough. |
| b.reserve(n) |
| for { |
| m, err := r.Read(b.data[len(b.data):cap(b.data)]) |
| b.data = b.data[0 : len(b.data)+m] |
| if len(b.data) >= n { |
| break |
| } |
| if err != nil { |
| return err |
| } |
| } |
| return nil |
| } |
| |
| func (b *block) Read(p []byte) (n int, err os.Error) { |
| n = copy(p, b.data[b.off:]) |
| b.off += n |
| return |
| } |
| |
| // newBlock allocates a new block, from hc's free list if possible. |
| func (hc *halfConn) newBlock() *block { |
| b := hc.bfree |
| if b == nil { |
| return new(block) |
| } |
| hc.bfree = b.link |
| b.link = nil |
| b.resize(0) |
| return b |
| } |
| |
| // freeBlock returns a block to hc's free list. |
| // The protocol is such that each side only has a block or two on |
| // its free list at a time, so there's no need to worry about |
| // trimming the list, etc. |
| func (hc *halfConn) freeBlock(b *block) { |
| b.link = hc.bfree |
| hc.bfree = b |
| } |
| |
| // splitBlock splits a block after the first n bytes, |
| // returning a block with those n bytes and a |
| // block with the remaindec. the latter may be nil. |
| func (hc *halfConn) splitBlock(b *block, n int) (*block, *block) { |
| if len(b.data) <= n { |
| return b, nil |
| } |
| bb := hc.newBlock() |
| bb.resize(len(b.data) - n) |
| copy(bb.data, b.data[n:]) |
| b.data = b.data[0:n] |
| return b, bb |
| } |
| |
| // readRecord reads the next TLS record from the connection |
| // and updates the record layer state. |
| // c.in.Mutex <= L; c.input == nil. |
| func (c *Conn) readRecord(want recordType) os.Error { |
| // Caller must be in sync with connection: |
| // handshake data if handshake not yet completed, |
| // else application data. (We don't support renegotiation.) |
| switch want { |
| default: |
| return c.sendAlert(alertInternalError) |
| case recordTypeHandshake, recordTypeChangeCipherSpec: |
| if c.handshakeComplete { |
| return c.sendAlert(alertInternalError) |
| } |
| case recordTypeApplicationData: |
| if !c.handshakeComplete { |
| return c.sendAlert(alertInternalError) |
| } |
| } |
| |
| Again: |
| if c.rawInput == nil { |
| c.rawInput = c.in.newBlock() |
| } |
| b := c.rawInput |
| |
| // Read header, payload. |
| if err := b.readFromUntil(c.conn, recordHeaderLen); err != nil { |
| // RFC suggests that EOF without an alertCloseNotify is |
| // an error, but popular web sites seem to do this, |
| // so we can't make it an error. |
| // if err == os.EOF { |
| // err = io.ErrUnexpectedEOF |
| // } |
| if e, ok := err.(net.Error); !ok || !e.Temporary() { |
| c.setError(err) |
| } |
| return err |
| } |
| typ := recordType(b.data[0]) |
| vers := uint16(b.data[1])<<8 | uint16(b.data[2]) |
| n := int(b.data[3])<<8 | int(b.data[4]) |
| if c.haveVers && vers != c.vers { |
| return c.sendAlert(alertProtocolVersion) |
| } |
| if n > maxCiphertext { |
| return c.sendAlert(alertRecordOverflow) |
| } |
| if err := b.readFromUntil(c.conn, recordHeaderLen+n); err != nil { |
| if err == os.EOF { |
| err = io.ErrUnexpectedEOF |
| } |
| if e, ok := err.(net.Error); !ok || !e.Temporary() { |
| c.setError(err) |
| } |
| return err |
| } |
| |
| // Process message. |
| b, c.rawInput = c.in.splitBlock(b, recordHeaderLen+n) |
| b.off = recordHeaderLen |
| if ok, err := c.in.decrypt(b); !ok { |
| return c.sendAlert(err) |
| } |
| data := b.data[b.off:] |
| if len(data) > maxPlaintext { |
| c.sendAlert(alertRecordOverflow) |
| c.in.freeBlock(b) |
| return c.error() |
| } |
| |
| switch typ { |
| default: |
| c.sendAlert(alertUnexpectedMessage) |
| |
| case recordTypeAlert: |
| if len(data) != 2 { |
| c.sendAlert(alertUnexpectedMessage) |
| break |
| } |
| if alert(data[1]) == alertCloseNotify { |
| c.setError(os.EOF) |
| break |
| } |
| switch data[0] { |
| case alertLevelWarning: |
| // drop on the floor |
| c.in.freeBlock(b) |
| goto Again |
| case alertLevelError: |
| c.setError(&net.OpError{Op: "remote error", Error: alert(data[1])}) |
| default: |
| c.sendAlert(alertUnexpectedMessage) |
| } |
| |
| case recordTypeChangeCipherSpec: |
| if typ != want || len(data) != 1 || data[0] != 1 { |
| c.sendAlert(alertUnexpectedMessage) |
| break |
| } |
| err := c.in.changeCipherSpec() |
| if err != nil { |
| c.sendAlert(err.(alert)) |
| } |
| |
| case recordTypeApplicationData: |
| if typ != want { |
| c.sendAlert(alertUnexpectedMessage) |
| break |
| } |
| c.input = b |
| b = nil |
| |
| case recordTypeHandshake: |
| // TODO(rsc): Should at least pick off connection close. |
| if typ != want { |
| return c.sendAlert(alertNoRenegotiation) |
| } |
| c.hand.Write(data) |
| } |
| |
| if b != nil { |
| c.in.freeBlock(b) |
| } |
| return c.error() |
| } |
| |
| // sendAlert sends a TLS alert message. |
| // c.out.Mutex <= L. |
| func (c *Conn) sendAlertLocked(err alert) os.Error { |
| c.tmp[0] = alertLevelError |
| if err == alertNoRenegotiation { |
| c.tmp[0] = alertLevelWarning |
| } |
| c.tmp[1] = byte(err) |
| c.writeRecord(recordTypeAlert, c.tmp[0:2]) |
| // closeNotify is a special case in that it isn't an error: |
| if err != alertCloseNotify { |
| return c.setError(&net.OpError{Op: "local error", Error: err}) |
| } |
| return nil |
| } |
| |
| // sendAlert sends a TLS alert message. |
| // L < c.out.Mutex. |
| func (c *Conn) sendAlert(err alert) os.Error { |
| c.out.Lock() |
| defer c.out.Unlock() |
| return c.sendAlertLocked(err) |
| } |
| |
| // writeRecord writes a TLS record with the given type and payload |
| // to the connection and updates the record layer state. |
| // c.out.Mutex <= L. |
| func (c *Conn) writeRecord(typ recordType, data []byte) (n int, err os.Error) { |
| b := c.out.newBlock() |
| for len(data) > 0 { |
| m := len(data) |
| if m > maxPlaintext { |
| m = maxPlaintext |
| } |
| b.resize(recordHeaderLen + m) |
| b.data[0] = byte(typ) |
| vers := c.vers |
| if vers == 0 { |
| vers = maxVersion |
| } |
| b.data[1] = byte(vers >> 8) |
| b.data[2] = byte(vers) |
| b.data[3] = byte(m >> 8) |
| b.data[4] = byte(m) |
| copy(b.data[recordHeaderLen:], data) |
| c.out.encrypt(b) |
| _, err = c.conn.Write(b.data) |
| if err != nil { |
| break |
| } |
| n += m |
| data = data[m:] |
| } |
| c.out.freeBlock(b) |
| |
| if typ == recordTypeChangeCipherSpec { |
| err = c.out.changeCipherSpec() |
| if err != nil { |
| // Cannot call sendAlert directly, |
| // because we already hold c.out.Mutex. |
| c.tmp[0] = alertLevelError |
| c.tmp[1] = byte(err.(alert)) |
| c.writeRecord(recordTypeAlert, c.tmp[0:2]) |
| c.err = &net.OpError{Op: "local error", Error: err} |
| return n, c.err |
| } |
| } |
| return |
| } |
| |
| // readHandshake reads the next handshake message from |
| // the record layer. |
| // c.in.Mutex < L; c.out.Mutex < L. |
| func (c *Conn) readHandshake() (interface{}, os.Error) { |
| for c.hand.Len() < 4 { |
| if c.err != nil { |
| return nil, c.err |
| } |
| c.readRecord(recordTypeHandshake) |
| } |
| |
| data := c.hand.Bytes() |
| n := int(data[1])<<16 | int(data[2])<<8 | int(data[3]) |
| if n > maxHandshake { |
| c.sendAlert(alertInternalError) |
| return nil, c.err |
| } |
| for c.hand.Len() < 4+n { |
| if c.err != nil { |
| return nil, c.err |
| } |
| c.readRecord(recordTypeHandshake) |
| } |
| data = c.hand.Next(4 + n) |
| var m handshakeMessage |
| switch data[0] { |
| case typeClientHello: |
| m = new(clientHelloMsg) |
| case typeServerHello: |
| m = new(serverHelloMsg) |
| case typeCertificate: |
| m = new(certificateMsg) |
| case typeCertificateRequest: |
| m = new(certificateRequestMsg) |
| case typeCertificateStatus: |
| m = new(certificateStatusMsg) |
| case typeServerHelloDone: |
| m = new(serverHelloDoneMsg) |
| case typeClientKeyExchange: |
| m = new(clientKeyExchangeMsg) |
| case typeCertificateVerify: |
| m = new(certificateVerifyMsg) |
| case typeNextProtocol: |
| m = new(nextProtoMsg) |
| case typeFinished: |
| m = new(finishedMsg) |
| default: |
| c.sendAlert(alertUnexpectedMessage) |
| return nil, alertUnexpectedMessage |
| } |
| |
| // The handshake message unmarshallers |
| // expect to be able to keep references to data, |
| // so pass in a fresh copy that won't be overwritten. |
| data = append([]byte(nil), data...) |
| |
| if !m.unmarshal(data) { |
| c.sendAlert(alertUnexpectedMessage) |
| return nil, alertUnexpectedMessage |
| } |
| return m, nil |
| } |
| |
| // Write writes data to the connection. |
| func (c *Conn) Write(b []byte) (n int, err os.Error) { |
| if err = c.Handshake(); err != nil { |
| return |
| } |
| |
| c.out.Lock() |
| defer c.out.Unlock() |
| |
| if !c.handshakeComplete { |
| return 0, alertInternalError |
| } |
| if c.err != nil { |
| return 0, c.err |
| } |
| return c.writeRecord(recordTypeApplicationData, b) |
| } |
| |
| // Read can be made to time out and return err == os.EAGAIN |
| // after a fixed time limit; see SetTimeout and SetReadTimeout. |
| func (c *Conn) Read(b []byte) (n int, err os.Error) { |
| if err = c.Handshake(); err != nil { |
| return |
| } |
| |
| c.in.Lock() |
| defer c.in.Unlock() |
| |
| for c.input == nil && c.err == nil { |
| if err := c.readRecord(recordTypeApplicationData); err != nil { |
| // Soft error, like EAGAIN |
| return 0, err |
| } |
| } |
| if c.err != nil { |
| return 0, c.err |
| } |
| n, err = c.input.Read(b) |
| if c.input.off >= len(c.input.data) { |
| c.in.freeBlock(c.input) |
| c.input = nil |
| } |
| return n, nil |
| } |
| |
| // Close closes the connection. |
| func (c *Conn) Close() os.Error { |
| if err := c.Handshake(); err != nil { |
| return err |
| } |
| return c.sendAlert(alertCloseNotify) |
| } |
| |
| // Handshake runs the client or server handshake |
| // protocol if it has not yet been run. |
| // Most uses of this package need not call Handshake |
| // explicitly: the first Read or Write will call it automatically. |
| func (c *Conn) Handshake() os.Error { |
| c.handshakeMutex.Lock() |
| defer c.handshakeMutex.Unlock() |
| if err := c.error(); err != nil { |
| return err |
| } |
| if c.handshakeComplete { |
| return nil |
| } |
| if c.isClient { |
| return c.clientHandshake() |
| } |
| return c.serverHandshake() |
| } |
| |
| // ConnectionState returns basic TLS details about the connection. |
| func (c *Conn) ConnectionState() ConnectionState { |
| c.handshakeMutex.Lock() |
| defer c.handshakeMutex.Unlock() |
| |
| var state ConnectionState |
| state.HandshakeComplete = c.handshakeComplete |
| if c.handshakeComplete { |
| state.NegotiatedProtocol = c.clientProtocol |
| state.CipherSuite = c.cipherSuite |
| } |
| |
| return state |
| } |
| |
| // OCSPResponse returns the stapled OCSP response from the TLS server, if |
| // any. (Only valid for client connections.) |
| func (c *Conn) OCSPResponse() []byte { |
| c.handshakeMutex.Lock() |
| defer c.handshakeMutex.Unlock() |
| |
| return c.ocspResponse |
| } |
| |
| // PeerCertificates returns the certificate chain that was presented by the |
| // other side. |
| func (c *Conn) PeerCertificates() []*x509.Certificate { |
| c.handshakeMutex.Lock() |
| defer c.handshakeMutex.Unlock() |
| |
| return c.peerCertificates |
| } |
| |
| // VerifyHostname checks that the peer certificate chain is valid for |
| // connecting to host. If so, it returns nil; if not, it returns an os.Error |
| // describing the problem. |
| func (c *Conn) VerifyHostname(host string) os.Error { |
| c.handshakeMutex.Lock() |
| defer c.handshakeMutex.Unlock() |
| if !c.isClient { |
| return os.ErrorString("VerifyHostname called on TLS server connection") |
| } |
| if !c.handshakeComplete { |
| return os.ErrorString("TLS handshake has not yet been performed") |
| } |
| return c.peerCertificates[0].VerifyHostname(host) |
| } |