// Copyright 2010 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. // TLS low level connection and record layer package main import ( "bytes" "crypto/cipher" "crypto/ecdsa" "crypto/subtle" "crypto/x509" "encoding/binary" "errors" "fmt" "io" "net" "sync" "time" ) // A Conn represents a secured connection. // It implements the net.Conn interface. type Conn struct { // constant conn net.Conn isDTLS bool isClient bool // constant after handshake; protected by handshakeMutex handshakeMutex sync.Mutex // handshakeMutex < in.Mutex, out.Mutex, errMutex handshakeErr error // error resulting from handshake vers uint16 // TLS version haveVers bool // version has been negotiated config *Config // configuration passed to constructor handshakeComplete bool didResume bool // whether this connection was a session resumption extendedMasterSecret bool // whether this session used an extended master secret cipherSuite *cipherSuite ocspResponse []byte // stapled OCSP response sctList []byte // signed certificate timestamp list peerCertificates []*x509.Certificate // verifiedChains contains the certificate chains that we built, as // opposed to the ones presented by the server. verifiedChains [][]*x509.Certificate // serverName contains the server name indicated by the client, if any. serverName string // firstFinished contains the first Finished hash sent during the // handshake. This is the "tls-unique" channel binding value. firstFinished [12]byte // clientCertSignatureHash contains the TLS hash id for the hash that // was used by the client to sign the handshake with a client // certificate. This is only set by a server and is zero if no client // certificates were used. clientCertSignatureHash uint8 clientRandom, serverRandom [32]byte masterSecret [48]byte clientProtocol string clientProtocolFallback bool usedALPN bool // verify_data values for the renegotiation extension. clientVerify []byte serverVerify []byte channelID *ecdsa.PublicKey srtpProtectionProfile uint16 clientVersion uint16 // input/output in, out halfConn // in.Mutex < out.Mutex rawInput *block // raw input, right off the wire input *block // application record waiting to be read hand bytes.Buffer // handshake record waiting to be read // DTLS state sendHandshakeSeq uint16 recvHandshakeSeq uint16 handMsg []byte // pending assembled handshake message handMsgLen int // handshake message length, not including the header pendingFragments [][]byte // pending outgoing handshake fragments. tmp [16]byte } func (c *Conn) init() { c.in.isDTLS = c.isDTLS c.out.isDTLS = c.isDTLS c.in.config = c.config c.out.config = c.config c.out.updateOutSeq() } // 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() } // SetDeadline sets the read and write deadlines associated with the connection. // A zero value for t means Read and Write will not time out. // After a Write has timed out, the TLS state is corrupt and all future writes will return the same error. func (c *Conn) SetDeadline(t time.Time) error { return c.conn.SetDeadline(t) } // SetReadDeadline sets the read deadline on the underlying connection. // A zero value for t means Read will not time out. func (c *Conn) SetReadDeadline(t time.Time) error { return c.conn.SetReadDeadline(t) } // SetWriteDeadline sets the write deadline on the underlying conneciton. // A zero value for t means Write will not time out. // After a Write has timed out, the TLS state is corrupt and all future writes will return the same error. func (c *Conn) SetWriteDeadline(t time.Time) error { return c.conn.SetWriteDeadline(t) } // A halfConn represents one direction of the record layer // connection, either sending or receiving. type halfConn struct { sync.Mutex err error // first permanent error version uint16 // protocol version isDTLS bool cipher interface{} // cipher algorithm mac macFunction seq [8]byte // 64-bit sequence number outSeq [8]byte // Mapped sequence number bfree *block // list of free blocks nextCipher interface{} // next encryption state nextMac macFunction // next MAC algorithm nextSeq [6]byte // next epoch's starting sequence number in DTLS // used to save allocating a new buffer for each MAC. inDigestBuf, outDigestBuf []byte config *Config } func (hc *halfConn) setErrorLocked(err error) error { hc.err = err return err } func (hc *halfConn) error() error { // This should be locked, but I've removed it for the renegotiation // tests since we don't concurrently read and write the same tls.Conn // in any case during testing. err := hc.err return err } // prepareCipherSpec sets the encryption and MAC states // that a subsequent changeCipherSpec will use. func (hc *halfConn) prepareCipherSpec(version uint16, cipher interface{}, mac macFunction) { hc.version = version hc.nextCipher = cipher hc.nextMac = mac } // changeCipherSpec changes the encryption and MAC states // to the ones previously passed to prepareCipherSpec. func (hc *halfConn) changeCipherSpec(config *Config) error { if hc.nextCipher == nil { return alertInternalError } hc.cipher = hc.nextCipher hc.mac = hc.nextMac hc.nextCipher = nil hc.nextMac = nil hc.config = config hc.incEpoch() return nil } // incSeq increments the sequence number. func (hc *halfConn) incSeq(isOutgoing bool) { limit := 0 increment := uint64(1) if hc.isDTLS { // Increment up to the epoch in DTLS. limit = 2 } for i := 7; i >= limit; i-- { increment += uint64(hc.seq[i]) hc.seq[i] = byte(increment) increment >>= 8 } // Not allowed to let sequence number wrap. // Instead, must renegotiate before it does. // Not likely enough to bother. if increment != 0 { panic("TLS: sequence number wraparound") } hc.updateOutSeq() } // incNextSeq increments the starting sequence number for the next epoch. func (hc *halfConn) incNextSeq() { for i := len(hc.nextSeq) - 1; i >= 0; i-- { hc.nextSeq[i]++ if hc.nextSeq[i] != 0 { return } } panic("TLS: sequence number wraparound") } // incEpoch resets the sequence number. In DTLS, it also increments the epoch // half of the sequence number. func (hc *halfConn) incEpoch() { if hc.isDTLS { for i := 1; i >= 0; i-- { hc.seq[i]++ if hc.seq[i] != 0 { break } if i == 0 { panic("TLS: epoch number wraparound") } } copy(hc.seq[2:], hc.nextSeq[:]) for i := range hc.nextSeq { hc.nextSeq[i] = 0 } } else { for i := range hc.seq { hc.seq[i] = 0 } } hc.updateOutSeq() } func (hc *halfConn) updateOutSeq() { if hc.config.Bugs.SequenceNumberMapping != nil { seqU64 := binary.BigEndian.Uint64(hc.seq[:]) seqU64 = hc.config.Bugs.SequenceNumberMapping(seqU64) binary.BigEndian.PutUint64(hc.outSeq[:], seqU64) // The DTLS epoch cannot be changed. copy(hc.outSeq[:2], hc.seq[:2]) return } copy(hc.outSeq[:], hc.seq[:]) } func (hc *halfConn) recordHeaderLen() int { if hc.isDTLS { return dtlsRecordHeaderLen } return tlsRecordHeaderLen } // removePadding returns an unpadded slice, in constant time, which is a prefix // of the input. It also returns a byte which is equal to 255 if the padding // was valid and 0 otherwise. See RFC 2246, section 6.2.3.2 func removePadding(payload []byte) ([]byte, byte) { if len(payload) < 1 { return payload, 0 } paddingLen := payload[len(payload)-1] t := uint(len(payload)-1) - uint(paddingLen) // if len(payload) >= (paddingLen - 1) then the MSB of t is zero good := byte(int32(^t) >> 31) toCheck := 255 // the maximum possible padding length // The length of the padded data is public, so we can use an if here if toCheck+1 > len(payload) { toCheck = len(payload) - 1 } for i := 0; i < toCheck; i++ { t := uint(paddingLen) - uint(i) // if i <= paddingLen then the MSB of t is zero mask := byte(int32(^t) >> 31) b := payload[len(payload)-1-i] good &^= mask&paddingLen ^ mask&b } // We AND together the bits of good and replicate the result across // all the bits. good &= good << 4 good &= good << 2 good &= good << 1 good = uint8(int8(good) >> 7) toRemove := good&paddingLen + 1 return payload[:len(payload)-int(toRemove)], good } // removePaddingSSL30 is a replacement for removePadding in the case that the // protocol version is SSLv3. In this version, the contents of the padding // are random and cannot be checked. func removePaddingSSL30(payload []byte) ([]byte, byte) { if len(payload) < 1 { return payload, 0 } paddingLen := int(payload[len(payload)-1]) + 1 if paddingLen > len(payload) { return payload, 0 } return payload[:len(payload)-paddingLen], 255 } func roundUp(a, b int) int { return a + (b-a%b)%b } // cbcMode is an interface for block ciphers using cipher block chaining. type cbcMode interface { cipher.BlockMode SetIV([]byte) } // decrypt checks and strips the mac and decrypts the data in b. Returns a // success boolean, the number of bytes to skip from the start of the record in // order to get the application payload, and an optional alert value. func (hc *halfConn) decrypt(b *block) (ok bool, prefixLen int, alertValue alert) { recordHeaderLen := hc.recordHeaderLen() // pull out payload payload := b.data[recordHeaderLen:] macSize := 0 if hc.mac != nil { macSize = hc.mac.Size() } paddingGood := byte(255) explicitIVLen := 0 seq := hc.seq[:] if hc.isDTLS { // DTLS sequence numbers are explicit. seq = b.data[3:11] } // decrypt if hc.cipher != nil { switch c := hc.cipher.(type) { case cipher.Stream: c.XORKeyStream(payload, payload) case *tlsAead: nonce := seq if c.explicitNonce { explicitIVLen = 8 if len(payload) < explicitIVLen { return false, 0, alertBadRecordMAC } nonce = payload[:8] payload = payload[8:] } var additionalData [13]byte copy(additionalData[:], seq) copy(additionalData[8:], b.data[:3]) n := len(payload) - c.Overhead() additionalData[11] = byte(n >> 8) additionalData[12] = byte(n) var err error payload, err = c.Open(payload[:0], nonce, payload, additionalData[:]) if err != nil { return false, 0, alertBadRecordMAC } b.resize(recordHeaderLen + explicitIVLen + len(payload)) case cbcMode: blockSize := c.BlockSize() if hc.version >= VersionTLS11 || hc.isDTLS { explicitIVLen = blockSize } if len(payload)%blockSize != 0 || len(payload) < roundUp(explicitIVLen+macSize+1, blockSize) { return false, 0, alertBadRecordMAC } if explicitIVLen > 0 { c.SetIV(payload[:explicitIVLen]) payload = payload[explicitIVLen:] } c.CryptBlocks(payload, payload) if hc.version == VersionSSL30 { payload, paddingGood = removePaddingSSL30(payload) } else { payload, paddingGood = removePadding(payload) } b.resize(recordHeaderLen + explicitIVLen + len(payload)) // note that we still have a timing side-channel in the // MAC check, below. An attacker can align the record // so that a correct padding will cause one less hash // block to be calculated. Then they can iteratively // decrypt a record by breaking each byte. See // "Password Interception in a SSL/TLS Channel", Brice // Canvel et al. // // However, our behavior matches OpenSSL, so we leak // only as much as they do. case nullCipher: break default: panic("unknown cipher type") } } // check, strip mac if hc.mac != nil { if len(payload) < macSize { return false, 0, alertBadRecordMAC } // strip mac off payload, b.data n := len(payload) - macSize b.data[recordHeaderLen-2] = byte(n >> 8) b.data[recordHeaderLen-1] = byte(n) b.resize(recordHeaderLen + explicitIVLen + n) remoteMAC := payload[n:] localMAC := hc.mac.MAC(hc.inDigestBuf, seq, b.data[:3], b.data[recordHeaderLen-2:recordHeaderLen], payload[:n]) if subtle.ConstantTimeCompare(localMAC, remoteMAC) != 1 || paddingGood != 255 { return false, 0, alertBadRecordMAC } hc.inDigestBuf = localMAC } hc.incSeq(false) return true, recordHeaderLen + explicitIVLen, 0 } // padToBlockSize calculates the needed padding block, if any, for a payload. // On exit, prefix aliases payload and extends to the end of the last full // block of payload. finalBlock is a fresh slice which contains the contents of // any suffix of payload as well as the needed padding to make finalBlock a // full block. func padToBlockSize(payload []byte, blockSize int, config *Config) (prefix, finalBlock []byte) { overrun := len(payload) % blockSize prefix = payload[:len(payload)-overrun] paddingLen := blockSize - overrun finalSize := blockSize if config.Bugs.MaxPadding { for paddingLen+blockSize <= 256 { paddingLen += blockSize } finalSize = 256 } finalBlock = make([]byte, finalSize) for i := range finalBlock { finalBlock[i] = byte(paddingLen - 1) } if config.Bugs.PaddingFirstByteBad || config.Bugs.PaddingFirstByteBadIf255 && paddingLen == 256 { finalBlock[overrun] ^= 0xff } copy(finalBlock, payload[len(payload)-overrun:]) return } // encrypt encrypts and macs the data in b. func (hc *halfConn) encrypt(b *block, explicitIVLen int) (bool, alert) { recordHeaderLen := hc.recordHeaderLen() // mac if hc.mac != nil { mac := hc.mac.MAC(hc.outDigestBuf, hc.outSeq[0:], b.data[:3], b.data[recordHeaderLen-2:recordHeaderLen], b.data[recordHeaderLen+explicitIVLen:]) n := len(b.data) b.resize(n + len(mac)) copy(b.data[n:], mac) hc.outDigestBuf = mac } payload := b.data[recordHeaderLen:] // encrypt if hc.cipher != nil { switch c := hc.cipher.(type) { case cipher.Stream: c.XORKeyStream(payload, payload) case *tlsAead: payloadLen := len(b.data) - recordHeaderLen - explicitIVLen b.resize(len(b.data) + c.Overhead()) nonce := hc.outSeq[:] if c.explicitNonce { nonce = b.data[recordHeaderLen : recordHeaderLen+explicitIVLen] } payload := b.data[recordHeaderLen+explicitIVLen:] payload = payload[:payloadLen] var additionalData [13]byte copy(additionalData[:], hc.outSeq[:]) copy(additionalData[8:], b.data[:3]) additionalData[11] = byte(payloadLen >> 8) additionalData[12] = byte(payloadLen) c.Seal(payload[:0], nonce, payload, additionalData[:]) case cbcMode: blockSize := c.BlockSize() if explicitIVLen > 0 { c.SetIV(payload[:explicitIVLen]) payload = payload[explicitIVLen:] } prefix, finalBlock := padToBlockSize(payload, blockSize, hc.config) b.resize(recordHeaderLen + explicitIVLen + len(prefix) + len(finalBlock)) c.CryptBlocks(b.data[recordHeaderLen+explicitIVLen:], prefix) c.CryptBlocks(b.data[recordHeaderLen+explicitIVLen+len(prefix):], finalBlock) case nullCipher: break default: panic("unknown cipher type") } } // update length to include MAC and any block padding needed. n := len(b.data) - recordHeaderLen b.data[recordHeaderLen-2] = byte(n >> 8) b.data[recordHeaderLen-1] = byte(n) hc.incSeq(true) 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) 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 { // TODO(bradfitz,agl): slightly suspicious // that we're throwing away r.Read's err here. break } if err != nil { return err } } return nil } func (b *block) Read(p []byte) (n int, err 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 remainder. 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 } func (c *Conn) doReadRecord(want recordType) (recordType, *block, error) { if c.isDTLS { return c.dtlsDoReadRecord(want) } recordHeaderLen := tlsRecordHeaderLen 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, outside of tests. if err == io.EOF && c.config.Bugs.ExpectCloseNotify { err = io.ErrUnexpectedEOF } if e, ok := err.(net.Error); !ok || !e.Temporary() { c.in.setErrorLocked(err) } return 0, nil, err } typ := recordType(b.data[0]) // No valid TLS record has a type of 0x80, however SSLv2 handshakes // start with a uint16 length where the MSB is set and the first record // is always < 256 bytes long. Therefore typ == 0x80 strongly suggests // an SSLv2 client. if want == recordTypeHandshake && typ == 0x80 { c.sendAlert(alertProtocolVersion) return 0, nil, c.in.setErrorLocked(errors.New("tls: unsupported SSLv2 handshake received")) } vers := uint16(b.data[1])<<8 | uint16(b.data[2]) n := int(b.data[3])<<8 | int(b.data[4]) if c.haveVers { if vers != c.vers { c.sendAlert(alertProtocolVersion) return 0, nil, c.in.setErrorLocked(fmt.Errorf("tls: received record with version %x when expecting version %x", vers, c.vers)) } } else { if expect := c.config.Bugs.ExpectInitialRecordVersion; expect != 0 && vers != expect { c.sendAlert(alertProtocolVersion) return 0, nil, c.in.setErrorLocked(fmt.Errorf("tls: received record with version %x when expecting version %x", vers, expect)) } } if n > maxCiphertext { c.sendAlert(alertRecordOverflow) return 0, nil, c.in.setErrorLocked(fmt.Errorf("tls: oversized record received with length %d", n)) } if !c.haveVers { // First message, be extra suspicious: // this might not be a TLS client. // Bail out before reading a full 'body', if possible. // The current max version is 3.1. // If the version is >= 16.0, it's probably not real. // Similarly, a clientHello message encodes in // well under a kilobyte. If the length is >= 12 kB, // it's probably not real. if (typ != recordTypeAlert && typ != want) || vers >= 0x1000 || n >= 0x3000 { c.sendAlert(alertUnexpectedMessage) return 0, nil, c.in.setErrorLocked(fmt.Errorf("tls: first record does not look like a TLS handshake")) } } if err := b.readFromUntil(c.conn, recordHeaderLen+n); err != nil { if err == io.EOF { err = io.ErrUnexpectedEOF } if e, ok := err.(net.Error); !ok || !e.Temporary() { c.in.setErrorLocked(err) } return 0, nil, err } // Process message. b, c.rawInput = c.in.splitBlock(b, recordHeaderLen+n) ok, off, err := c.in.decrypt(b) if !ok { c.in.setErrorLocked(c.sendAlert(err)) } b.off = off return typ, b, nil } // 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) error { // Caller must be in sync with connection: // handshake data if handshake not yet completed, // else application data. switch want { default: c.sendAlert(alertInternalError) return c.in.setErrorLocked(errors.New("tls: unknown record type requested")) case recordTypeHandshake, recordTypeChangeCipherSpec: if c.handshakeComplete { c.sendAlert(alertInternalError) return c.in.setErrorLocked(errors.New("tls: handshake or ChangeCipherSpec requested after handshake complete")) } case recordTypeApplicationData: if !c.handshakeComplete && !c.config.Bugs.ExpectFalseStart { c.sendAlert(alertInternalError) return c.in.setErrorLocked(errors.New("tls: application data record requested before handshake complete")) } case recordTypeAlert: // Looking for a close_notify. Note: unlike a real // implementation, this is not tolerant of additional records. // See the documentation for ExpectCloseNotify. } Again: typ, b, err := c.doReadRecord(want) if err != nil { return err } data := b.data[b.off:] if len(data) > maxPlaintext { err := c.sendAlert(alertRecordOverflow) c.in.freeBlock(b) return c.in.setErrorLocked(err) } switch typ { default: c.in.setErrorLocked(c.sendAlert(alertUnexpectedMessage)) case recordTypeAlert: if len(data) != 2 { c.in.setErrorLocked(c.sendAlert(alertUnexpectedMessage)) break } if alert(data[1]) == alertCloseNotify { c.in.setErrorLocked(io.EOF) break } switch data[0] { case alertLevelWarning: // drop on the floor c.in.freeBlock(b) goto Again case alertLevelError: c.in.setErrorLocked(&net.OpError{Op: "remote error", Err: alert(data[1])}) default: c.in.setErrorLocked(c.sendAlert(alertUnexpectedMessage)) } case recordTypeChangeCipherSpec: if typ != want || len(data) != 1 || data[0] != 1 { c.in.setErrorLocked(c.sendAlert(alertUnexpectedMessage)) break } err := c.in.changeCipherSpec(c.config) if err != nil { c.in.setErrorLocked(c.sendAlert(err.(alert))) } case recordTypeApplicationData: if typ != want { c.in.setErrorLocked(c.sendAlert(alertUnexpectedMessage)) break } c.input = b b = nil case recordTypeHandshake: // TODO(rsc): Should at least pick off connection close. if typ != want { // A client might need to process a HelloRequest from // the server, thus receiving a handshake message when // application data is expected is ok. if !c.isClient || want != recordTypeApplicationData { return c.in.setErrorLocked(c.sendAlert(alertNoRenegotiation)) } } c.hand.Write(data) } if b != nil { c.in.freeBlock(b) } return c.in.err } // sendAlert sends a TLS alert message. // c.out.Mutex <= L. func (c *Conn) sendAlertLocked(level byte, err alert) error { c.tmp[0] = level c.tmp[1] = byte(err) if c.config.Bugs.FragmentAlert { c.writeRecord(recordTypeAlert, c.tmp[0:1]) c.writeRecord(recordTypeAlert, c.tmp[1:2]) } else { c.writeRecord(recordTypeAlert, c.tmp[0:2]) } // Error alerts are fatal to the connection. if level == alertLevelError { return c.out.setErrorLocked(&net.OpError{Op: "local error", Err: err}) } return nil } // sendAlert sends a TLS alert message. // L < c.out.Mutex. func (c *Conn) sendAlert(err alert) error { level := byte(alertLevelError) if err == alertNoRenegotiation || err == alertCloseNotify { level = alertLevelWarning } return c.SendAlert(level, err) } func (c *Conn) SendAlert(level byte, err alert) error { c.out.Lock() defer c.out.Unlock() return c.sendAlertLocked(level, err) } // writeV2Record writes a record for a V2ClientHello. func (c *Conn) writeV2Record(data []byte) (n int, err error) { record := make([]byte, 2+len(data)) record[0] = uint8(len(data)>>8) | 0x80 record[1] = uint8(len(data)) copy(record[2:], data) return c.conn.Write(record) } // 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 error) { if c.isDTLS { return c.dtlsWriteRecord(typ, data) } recordHeaderLen := tlsRecordHeaderLen b := c.out.newBlock() first := true isClientHello := typ == recordTypeHandshake && len(data) > 0 && data[0] == typeClientHello for len(data) > 0 || first { m := len(data) if m > maxPlaintext && !c.config.Bugs.SendLargeRecords { m = maxPlaintext } if typ == recordTypeHandshake && c.config.Bugs.MaxHandshakeRecordLength > 0 && m > c.config.Bugs.MaxHandshakeRecordLength { m = c.config.Bugs.MaxHandshakeRecordLength // By default, do not fragment the client_version or // server_version, which are located in the first 6 // bytes. if first && isClientHello && !c.config.Bugs.FragmentClientVersion && m < 6 { m = 6 } } explicitIVLen := 0 explicitIVIsSeq := false first = false var cbc cbcMode if c.out.version >= VersionTLS11 { var ok bool if cbc, ok = c.out.cipher.(cbcMode); ok { explicitIVLen = cbc.BlockSize() } } if explicitIVLen == 0 { if aead, ok := c.out.cipher.(*tlsAead); ok && aead.explicitNonce { explicitIVLen = 8 // The AES-GCM construction in TLS has an // explicit nonce so that the nonce can be // random. However, the nonce is only 8 bytes // which is too small for a secure, random // nonce. Therefore we use the sequence number // as the nonce. explicitIVIsSeq = true } } b.resize(recordHeaderLen + explicitIVLen + m) b.data[0] = byte(typ) vers := c.vers if vers == 0 { // Some TLS servers fail if the record version is // greater than TLS 1.0 for the initial ClientHello. vers = VersionTLS10 } b.data[1] = byte(vers >> 8) b.data[2] = byte(vers) b.data[3] = byte(m >> 8) b.data[4] = byte(m) if explicitIVLen > 0 { explicitIV := b.data[recordHeaderLen : recordHeaderLen+explicitIVLen] if explicitIVIsSeq { copy(explicitIV, c.out.seq[:]) } else { if _, err = io.ReadFull(c.config.rand(), explicitIV); err != nil { break } } } copy(b.data[recordHeaderLen+explicitIVLen:], data) c.out.encrypt(b, explicitIVLen) _, 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(c.config) 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]) return n, c.out.setErrorLocked(&net.OpError{Op: "local error", Err: err}) } } return } func (c *Conn) doReadHandshake() ([]byte, error) { if c.isDTLS { return c.dtlsDoReadHandshake() } for c.hand.Len() < 4 { if err := c.in.err; err != nil { return nil, err } if err := c.readRecord(recordTypeHandshake); err != nil { return nil, err } } data := c.hand.Bytes() n := int(data[1])<<16 | int(data[2])<<8 | int(data[3]) if n > maxHandshake { return nil, c.in.setErrorLocked(c.sendAlert(alertInternalError)) } for c.hand.Len() < 4+n { if err := c.in.err; err != nil { return nil, err } if err := c.readRecord(recordTypeHandshake); err != nil { return nil, err } } return c.hand.Next(4 + n), nil } // readHandshake reads the next handshake message from // the record layer. // c.in.Mutex < L; c.out.Mutex < L. func (c *Conn) readHandshake() (interface{}, error) { data, err := c.doReadHandshake() if err != nil { return nil, err } var m handshakeMessage switch data[0] { case typeHelloRequest: m = new(helloRequestMsg) case typeClientHello: m = &clientHelloMsg{ isDTLS: c.isDTLS, } case typeServerHello: m = &serverHelloMsg{ isDTLS: c.isDTLS, } case typeNewSessionTicket: m = new(newSessionTicketMsg) case typeCertificate: m = new(certificateMsg) case typeCertificateRequest: m = &certificateRequestMsg{ hasSignatureAndHash: c.vers >= VersionTLS12, } case typeCertificateStatus: m = new(certificateStatusMsg) case typeServerKeyExchange: m = new(serverKeyExchangeMsg) case typeServerHelloDone: m = new(serverHelloDoneMsg) case typeClientKeyExchange: m = new(clientKeyExchangeMsg) case typeCertificateVerify: m = &certificateVerifyMsg{ hasSignatureAndHash: c.vers >= VersionTLS12, } case typeNextProtocol: m = new(nextProtoMsg) case typeFinished: m = new(finishedMsg) case typeHelloVerifyRequest: m = new(helloVerifyRequestMsg) case typeEncryptedExtensions: m = new(encryptedExtensionsMsg) default: return nil, c.in.setErrorLocked(c.sendAlert(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) { return nil, c.in.setErrorLocked(c.sendAlert(alertUnexpectedMessage)) } return m, nil } // skipPacket processes all the DTLS records in packet. It updates // sequence number expectations but otherwise ignores them. func (c *Conn) skipPacket(packet []byte) error { for len(packet) > 0 { if len(packet) < 13 { return errors.New("tls: bad packet") } // Dropped packets are completely ignored save to update // expected sequence numbers for this and the next epoch. (We // don't assert on the contents of the packets both for // simplicity and because a previous test with one shorter // timeout schedule would have done so.) epoch := packet[3:5] seq := packet[5:11] length := uint16(packet[11])<<8 | uint16(packet[12]) if bytes.Equal(c.in.seq[:2], epoch) { if !bytes.Equal(c.in.seq[2:], seq) { return errors.New("tls: sequence mismatch") } c.in.incSeq(false) } else { if !bytes.Equal(c.in.nextSeq[:], seq) { return errors.New("tls: sequence mismatch") } c.in.incNextSeq() } if len(packet) < 13+int(length) { return errors.New("tls: bad packet") } packet = packet[13+length:] } return nil } // simulatePacketLoss simulates the loss of a handshake leg from the // peer based on the schedule in c.config.Bugs. If resendFunc is // non-nil, it is called after each simulated timeout to retransmit // handshake messages from the local end. This is used in cases where // the peer retransmits on a stale Finished rather than a timeout. func (c *Conn) simulatePacketLoss(resendFunc func()) error { if len(c.config.Bugs.TimeoutSchedule) == 0 { return nil } if !c.isDTLS { return errors.New("tls: TimeoutSchedule may only be set in DTLS") } if c.config.Bugs.PacketAdaptor == nil { return errors.New("tls: TimeoutSchedule set without PacketAdapter") } for _, timeout := range c.config.Bugs.TimeoutSchedule { // Simulate a timeout. packets, err := c.config.Bugs.PacketAdaptor.SendReadTimeout(timeout) if err != nil { return err } for _, packet := range packets { if err := c.skipPacket(packet); err != nil { return err } } if resendFunc != nil { resendFunc() } } return nil } // Write writes data to the connection. func (c *Conn) Write(b []byte) (int, error) { if err := c.Handshake(); err != nil { return 0, err } c.out.Lock() defer c.out.Unlock() if err := c.out.err; err != nil { return 0, err } if !c.handshakeComplete { return 0, alertInternalError } if c.config.Bugs.SendSpuriousAlert != 0 { c.sendAlertLocked(alertLevelError, c.config.Bugs.SendSpuriousAlert) } // SSL 3.0 and TLS 1.0 are susceptible to a chosen-plaintext // attack when using block mode ciphers due to predictable IVs. // This can be prevented by splitting each Application Data // record into two records, effectively randomizing the IV. // // http://www.openssl.org/~bodo/tls-cbc.txt // https://bugzilla.mozilla.org/show_bug.cgi?id=665814 // http://www.imperialviolet.org/2012/01/15/beastfollowup.html var m int if len(b) > 1 && c.vers <= VersionTLS10 && !c.isDTLS { if _, ok := c.out.cipher.(cipher.BlockMode); ok { n, err := c.writeRecord(recordTypeApplicationData, b[:1]) if err != nil { return n, c.out.setErrorLocked(err) } m, b = 1, b[1:] } } n, err := c.writeRecord(recordTypeApplicationData, b) return n + m, c.out.setErrorLocked(err) } func (c *Conn) handleRenegotiation() error { c.handshakeComplete = false if !c.isClient { panic("renegotiation should only happen for a client") } msg, err := c.readHandshake() if err != nil { return err } _, ok := msg.(*helloRequestMsg) if !ok { c.sendAlert(alertUnexpectedMessage) return alertUnexpectedMessage } return c.Handshake() } func (c *Conn) Renegotiate() error { if !c.isClient { helloReq := new(helloRequestMsg) c.writeRecord(recordTypeHandshake, helloReq.marshal()) } c.handshakeComplete = false return c.Handshake() } // Read can be made to time out and return a net.Error with Timeout() == true // after a fixed time limit; see SetDeadline and SetReadDeadline. func (c *Conn) Read(b []byte) (n int, err error) { if err = c.Handshake(); err != nil { return } c.in.Lock() defer c.in.Unlock() // Some OpenSSL servers send empty records in order to randomize the // CBC IV. So this loop ignores a limited number of empty records. const maxConsecutiveEmptyRecords = 100 for emptyRecordCount := 0; emptyRecordCount <= maxConsecutiveEmptyRecords; emptyRecordCount++ { for c.input == nil && c.in.err == nil { if err := c.readRecord(recordTypeApplicationData); err != nil { // Soft error, like EAGAIN return 0, err } if c.hand.Len() > 0 { // We received handshake bytes, indicating the // start of a renegotiation. if err := c.handleRenegotiation(); err != nil { return 0, err } continue } } if err := c.in.err; err != nil { return 0, err } n, err = c.input.Read(b) if c.input.off >= len(c.input.data) || c.isDTLS { c.in.freeBlock(c.input) c.input = nil } // If a close-notify alert is waiting, read it so that // we can return (n, EOF) instead of (n, nil), to signal // to the HTTP response reading goroutine that the // connection is now closed. This eliminates a race // where the HTTP response reading goroutine would // otherwise not observe the EOF until its next read, // by which time a client goroutine might have already // tried to reuse the HTTP connection for a new // request. // See https://codereview.appspot.com/76400046 // and http://golang.org/issue/3514 if ri := c.rawInput; ri != nil && n != 0 && err == nil && c.input == nil && len(ri.data) > 0 && recordType(ri.data[0]) == recordTypeAlert { if recErr := c.readRecord(recordTypeApplicationData); recErr != nil { err = recErr // will be io.EOF on closeNotify } } if n != 0 || err != nil { return n, err } } return 0, io.ErrNoProgress } // Close closes the connection. func (c *Conn) Close() error { var alertErr error c.handshakeMutex.Lock() defer c.handshakeMutex.Unlock() if c.handshakeComplete && !c.config.Bugs.NoCloseNotify { alertErr = c.sendAlert(alertCloseNotify) } // Consume a close_notify from the peer if one hasn't been received // already. This avoids the peer from failing |SSL_shutdown| due to a // write failing. if c.handshakeComplete && alertErr == nil && c.config.Bugs.ExpectCloseNotify { for c.in.error() == nil { c.readRecord(recordTypeAlert) } if c.in.error() != io.EOF { alertErr = c.in.error() } } if err := c.conn.Close(); err != nil { return err } return alertErr } // 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() error { c.handshakeMutex.Lock() defer c.handshakeMutex.Unlock() if err := c.handshakeErr; err != nil { return err } if c.handshakeComplete { return nil } if c.isDTLS && c.config.Bugs.SendSplitAlert { c.conn.Write([]byte{ byte(recordTypeAlert), // type 0xfe, 0xff, // version 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, // sequence 0x0, 0x2, // length }) c.conn.Write([]byte{alertLevelError, byte(alertInternalError)}) } if data := c.config.Bugs.AppDataBeforeHandshake; data != nil { c.writeRecord(recordTypeApplicationData, data) } if c.isClient { c.handshakeErr = c.clientHandshake() } else { c.handshakeErr = c.serverHandshake() } if c.handshakeErr == nil && c.config.Bugs.SendInvalidRecordType { c.writeRecord(recordType(42), []byte("invalid record")) } return c.handshakeErr } // 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.Version = c.vers state.NegotiatedProtocol = c.clientProtocol state.DidResume = c.didResume state.NegotiatedProtocolIsMutual = !c.clientProtocolFallback state.NegotiatedProtocolFromALPN = c.usedALPN state.CipherSuite = c.cipherSuite.id state.PeerCertificates = c.peerCertificates state.VerifiedChains = c.verifiedChains state.ServerName = c.serverName state.ChannelID = c.channelID state.SRTPProtectionProfile = c.srtpProtectionProfile state.TLSUnique = c.firstFinished[:] state.SCTList = c.sctList state.ClientCertSignatureHash = c.clientCertSignatureHash } 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 } // VerifyHostname checks that the peer certificate chain is valid for // connecting to host. If so, it returns nil; if not, it returns an error // describing the problem. func (c *Conn) VerifyHostname(host string) error { c.handshakeMutex.Lock() defer c.handshakeMutex.Unlock() if !c.isClient { return errors.New("tls: VerifyHostname called on TLS server connection") } if !c.handshakeComplete { return errors.New("tls: handshake has not yet been performed") } return c.peerCertificates[0].VerifyHostname(host) } // ExportKeyingMaterial exports keying material from the current connection // state, as per RFC 5705. func (c *Conn) ExportKeyingMaterial(length int, label, context []byte, useContext bool) ([]byte, error) { c.handshakeMutex.Lock() defer c.handshakeMutex.Unlock() if !c.handshakeComplete { return nil, errors.New("tls: handshake has not yet been performed") } seedLen := len(c.clientRandom) + len(c.serverRandom) if useContext { seedLen += 2 + len(context) } seed := make([]byte, 0, seedLen) seed = append(seed, c.clientRandom[:]...) seed = append(seed, c.serverRandom[:]...) if useContext { seed = append(seed, byte(len(context)>>8), byte(len(context))) seed = append(seed, context...) } result := make([]byte, length) prfForVersion(c.vers, c.cipherSuite)(result, c.masterSecret[:], label, seed) return result, nil }