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// 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 tls
import (
"bytes"
"crypto/cipher"
"crypto/subtle"
"crypto/x509"
"errors"
"fmt"
"io"
"net"
"sync"
"sync/atomic"
"time"
)
// 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
// handshakeCond, if not nil, indicates that a goroutine is committed
// to running the handshake for this Conn. Other goroutines that need
// to wait for the handshake can wait on this, under handshakeMutex.
handshakeCond *sync.Cond
handshakeErr error // error resulting from handshake
vers uint16 // TLS version
haveVers bool // version has been negotiated
config *Config // configuration passed to constructor
// handshakeComplete is true if the connection is currently transferring
// application data (i.e. is not currently processing a handshake).
handshakeComplete bool
// handshakes counts the number of handshakes performed on the
// connection so far. If renegotiation is disabled then this is either
// zero or one.
handshakes int
didResume bool // whether this connection was a session resumption
cipherSuite uint16
ocspResponse []byte // stapled OCSP response
scts [][]byte // signed certificate timestamps from server
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
// secureRenegotiation is true if the server echoed the secure
// renegotiation extension. (This is meaningless as a server because
// renegotiation is not supported in that case.)
secureRenegotiation bool
// clientFinishedIsFirst is true if the client sent the first Finished
// message during the most recent handshake. This is recorded because
// the first transmitted Finished message is the tls-unique
// channel-binding value.
clientFinishedIsFirst bool
// closeNotifyErr is any error from sending the alertCloseNotify record.
closeNotifyErr error
// closeNotifySent is true if the Conn attempted to send an
// alertCloseNotify record.
closeNotifySent bool
// clientFinished and serverFinished contain the Finished message sent
// by the client or server in the most recent handshake. This is
// retained to support the renegotiation extension and tls-unique
// channel-binding.
clientFinished [12]byte
serverFinished [12]byte
clientProtocol string
clientProtocolFallback bool
// 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
buffering bool // whether records are buffered in sendBuf
sendBuf []byte // a buffer of records waiting to be sent
// bytesSent counts the bytes of application data sent.
// packetsSent counts packets.
bytesSent int64
packetsSent int64
// warnCount counts the number of consecutive warning alerts received
// by Conn.readRecord. Protected by in.Mutex.
warnCount int
// activeCall is an atomic int32; the low bit is whether Close has
// been called. the rest of the bits are the number of goroutines
// in Conn.Write.
activeCall int32
tmp [16]byte
}
// 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 connection.
// 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
cipher interface{} // cipher algorithm
mac macFunction
seq [8]byte // 64-bit sequence number
bfree *block // list of free blocks
additionalData [13]byte // to avoid allocs; interface method args escape
nextCipher interface{} // next encryption state
nextMac macFunction // next MAC algorithm
// used to save allocating a new buffer for each MAC.
inDigestBuf, outDigestBuf []byte
}
func (hc *halfConn) setErrorLocked(err error) error {
hc.err = 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() error {
if hc.nextCipher == nil {
return alertInternalError
}
hc.cipher = hc.nextCipher
hc.mac = hc.nextMac
hc.nextCipher = nil
hc.nextMac = nil
for i := range hc.seq {
hc.seq[i] = 0
}
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")
}
// extractPadding returns, in constant time, the length of the padding to remove
// from the end of payload. 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 extractPadding(payload []byte) (toRemove int, good byte) {
if len(payload) < 1 {
return 0, 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)
// The maximum possible padding length plus the actual length field
toCheck := 256
// The length of the padded data is public, so we can use an if here
if toCheck > len(payload) {
toCheck = len(payload)
}
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 = int(paddingLen) + 1
return
}
// extractPaddingSSL30 is a replacement for extractPadding in the case that the
// protocol version is SSLv3. In this version, the contents of the padding
// are random and cannot be checked.
func extractPaddingSSL30(payload []byte) (toRemove int, good byte) {
if len(payload) < 1 {
return 0, 0
}
paddingLen := int(payload[len(payload)-1]) + 1
if paddingLen > len(payload) {
return 0, 0
}
return 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) {
// pull out payload
payload := b.data[recordHeaderLen:]
macSize := 0
if hc.mac != nil {
macSize = hc.mac.Size()
}
paddingGood := byte(255)
paddingLen := 0
explicitIVLen := 0
// decrypt
if hc.cipher != nil {
switch c := hc.cipher.(type) {
case cipher.Stream:
c.XORKeyStream(payload, payload)
case aead:
explicitIVLen = c.explicitNonceLen()
if len(payload) < explicitIVLen {
return false, 0, alertBadRecordMAC
}
nonce := payload[:explicitIVLen]
payload = payload[explicitIVLen:]
if len(nonce) == 0 {
nonce = hc.seq[:]
}
copy(hc.additionalData[:], hc.seq[:])
copy(hc.additionalData[8:], b.data[:3])
n := len(payload) - c.Overhead()
hc.additionalData[11] = byte(n >> 8)
hc.additionalData[12] = byte(n)
var err error
payload, err = c.Open(payload[:0], nonce, payload, hc.additionalData[:])
if err != nil {
return false, 0, alertBadRecordMAC
}
b.resize(recordHeaderLen + explicitIVLen + len(payload))
case cbcMode:
blockSize := c.BlockSize()
if hc.version >= VersionTLS11 {
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 {
paddingLen, paddingGood = extractPaddingSSL30(payload)
} else {
paddingLen, paddingGood = extractPadding(payload)
// To protect against CBC padding oracles like Lucky13, the data
// past paddingLen (which is secret) is passed to the MAC
// function as extra data, to be fed into the HMAC after
// computing the digest. This makes the MAC constant time as
// long as the digest computation is constant time and does not
// affect the subsequent write.
}
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 - paddingLen
n = subtle.ConstantTimeSelect(int(uint32(n)>>31), 0, n) // if n < 0 { n = 0 }
b.data[3] = byte(n >> 8)
b.data[4] = byte(n)
remoteMAC := payload[n : n+macSize]
localMAC := hc.mac.MAC(hc.inDigestBuf, hc.seq[0:], b.data[:recordHeaderLen], payload[:n], payload[n+macSize:])
if subtle.ConstantTimeCompare(localMAC, remoteMAC) != 1 || paddingGood != 255 {
return false, 0, alertBadRecordMAC
}
hc.inDigestBuf = localMAC
b.resize(recordHeaderLen + explicitIVLen + n)
}
hc.incSeq()
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) (prefix, finalBlock []byte) {
overrun := len(payload) % blockSize
paddingLen := blockSize - overrun
prefix = payload[:len(payload)-overrun]
finalBlock = make([]byte, blockSize)
copy(finalBlock, payload[len(payload)-overrun:])
for i := overrun; i < blockSize; i++ {
finalBlock[i] = byte(paddingLen - 1)
}
return
}
// encrypt encrypts and macs the data in b.
func (hc *halfConn) encrypt(b *block, explicitIVLen int) (bool, alert) {
// mac
if hc.mac != nil {
mac := hc.mac.MAC(hc.outDigestBuf, hc.seq[0:], b.data[:recordHeaderLen], b.data[recordHeaderLen+explicitIVLen:], nil)
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 aead:
payloadLen := len(b.data) - recordHeaderLen - explicitIVLen
b.resize(len(b.data) + c.Overhead())
nonce := b.data[recordHeaderLen : recordHeaderLen+explicitIVLen]
if len(nonce) == 0 {
nonce = hc.seq[:]
}
payload := b.data[recordHeaderLen+explicitIVLen:]
payload = payload[:payloadLen]
copy(hc.additionalData[:], hc.seq[:])
copy(hc.additionalData[8:], b.data[:3])
hc.additionalData[11] = byte(payloadLen >> 8)
hc.additionalData[12] = byte(payloadLen)
c.Seal(payload[:0], nonce, payload, hc.additionalData[:])
case cbcMode:
blockSize := c.BlockSize()
if explicitIVLen > 0 {
c.SetIV(payload[:explicitIVLen])
payload = payload[explicitIVLen:]
}
prefix, finalBlock := padToBlockSize(payload, blockSize)
b.resize(recordHeaderLen + explicitIVLen + len(prefix) + len(finalBlock))
c.CryptBlocks(b.data[recordHeaderLen+explicitIVLen:], prefix)
c.CryptBlocks(b.data[recordHeaderLen+explicitIVLen+len(prefix):], finalBlock)
default:
panic("unknown cipher type")
}
}
// update length to include MAC and any block padding needed.
n := len(b.data) - recordHeaderLen
b.data[3] = byte(n >> 8)
b.data[4] = byte(n)
hc.incSeq()
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
}
// RecordHeaderError results when a TLS record header is invalid.
type RecordHeaderError struct {
// Msg contains a human readable string that describes the error.
Msg string
// RecordHeader contains the five bytes of TLS record header that
// triggered the error.
RecordHeader [5]byte
}
func (e RecordHeaderError) Error() string { return "tls: " + e.Msg }
func (c *Conn) newRecordHeaderError(msg string) (err RecordHeaderError) {
err.Msg = msg
copy(err.RecordHeader[:], c.rawInput.data)
return err
}
// 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 while not in handshake"))
}
case recordTypeApplicationData:
if !c.handshakeComplete {
c.sendAlert(alertInternalError)
return c.in.setErrorLocked(errors.New("tls: application data record requested while in handshake"))
}
}
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 == io.EOF {
// err = io.ErrUnexpectedEOF
// }
if e, ok := err.(net.Error); !ok || !e.Temporary() {
c.in.setErrorLocked(err)
}
return 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 c.in.setErrorLocked(c.newRecordHeaderError("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 && vers != c.vers {
c.sendAlert(alertProtocolVersion)
msg := fmt.Sprintf("received record with version %x when expecting version %x", vers, c.vers)
return c.in.setErrorLocked(c.newRecordHeaderError(msg))
}
if n > maxCiphertext {
c.sendAlert(alertRecordOverflow)
msg := fmt.Sprintf("oversized record received with length %d", n)
return c.in.setErrorLocked(c.newRecordHeaderError(msg))
}
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 3.3 so if the version is >= 16.0,
// it's probably not real.
if (typ != recordTypeAlert && typ != want) || vers >= 0x1000 {
c.sendAlert(alertUnexpectedMessage)
return c.in.setErrorLocked(c.newRecordHeaderError("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 err
}
// Process message.
b, c.rawInput = c.in.splitBlock(b, recordHeaderLen+n)
ok, off, alertValue := c.in.decrypt(b)
if !ok {
c.in.freeBlock(b)
return c.in.setErrorLocked(c.sendAlert(alertValue))
}
b.off = off
data := b.data[b.off:]
if len(data) > maxPlaintext {
err := c.sendAlert(alertRecordOverflow)
c.in.freeBlock(b)
return c.in.setErrorLocked(err)
}
if typ != recordTypeAlert && len(data) > 0 {
// this is a valid non-alert message: reset the count of alerts
c.warnCount = 0
}
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)
c.warnCount++
if c.warnCount > maxWarnAlertCount {
c.sendAlert(alertUnexpectedMessage)
return c.in.setErrorLocked(errors.New("tls: too many warn alerts"))
}
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
}
// Handshake messages are not allowed to fragment across the CCS
if c.hand.Len() > 0 {
c.in.setErrorLocked(c.sendAlert(alertUnexpectedMessage))
break
}
err := c.in.changeCipherSpec()
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 && !(c.isClient && c.config.Renegotiation != RenegotiateNever) {
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(err alert) error {
switch err {
case alertNoRenegotiation, alertCloseNotify:
c.tmp[0] = alertLevelWarning
default:
c.tmp[0] = alertLevelError
}
c.tmp[1] = byte(err)
_, writeErr := c.writeRecordLocked(recordTypeAlert, c.tmp[0:2])
if err == alertCloseNotify {
// closeNotify is a special case in that it isn't an error.
return writeErr
}
return c.out.setErrorLocked(&net.OpError{Op: "local error", Err: err})
}
// sendAlert sends a TLS alert message.
// L < c.out.Mutex.
func (c *Conn) sendAlert(err alert) error {
c.out.Lock()
defer c.out.Unlock()
return c.sendAlertLocked(err)
}
const (
// tcpMSSEstimate is a conservative estimate of the TCP maximum segment
// size (MSS). A constant is used, rather than querying the kernel for
// the actual MSS, to avoid complexity. The value here is the IPv6
// minimum MTU (1280 bytes) minus the overhead of an IPv6 header (40
// bytes) and a TCP header with timestamps (32 bytes).
tcpMSSEstimate = 1208
// recordSizeBoostThreshold is the number of bytes of application data
// sent after which the TLS record size will be increased to the
// maximum.
recordSizeBoostThreshold = 128 * 1024
)
// maxPayloadSizeForWrite returns the maximum TLS payload size to use for the
// next application data record. There is the following trade-off:
//
// - For latency-sensitive applications, such as web browsing, each TLS
// record should fit in one TCP segment.
// - For throughput-sensitive applications, such as large file transfers,
// larger TLS records better amortize framing and encryption overheads.
//
// A simple heuristic that works well in practice is to use small records for
// the first 1MB of data, then use larger records for subsequent data, and
// reset back to smaller records after the connection becomes idle. See "High
// Performance Web Networking", Chapter 4, or:
// https://www.igvita.com/2013/10/24/optimizing-tls-record-size-and-buffering-latency/
//
// In the interests of simplicity and determinism, this code does not attempt
// to reset the record size once the connection is idle, however.
//
// c.out.Mutex <= L.
func (c *Conn) maxPayloadSizeForWrite(typ recordType, explicitIVLen int) int {
if c.config.DynamicRecordSizingDisabled || typ != recordTypeApplicationData {
return maxPlaintext
}
if c.bytesSent >= recordSizeBoostThreshold {
return maxPlaintext
}
// Subtract TLS overheads to get the maximum payload size.
macSize := 0
if c.out.mac != nil {
macSize = c.out.mac.Size()
}
payloadBytes := tcpMSSEstimate - recordHeaderLen - explicitIVLen
if c.out.cipher != nil {
switch ciph := c.out.cipher.(type) {
case cipher.Stream:
payloadBytes -= macSize
case cipher.AEAD:
payloadBytes -= ciph.Overhead()
case cbcMode:
blockSize := ciph.BlockSize()
// The payload must fit in a multiple of blockSize, with
// room for at least one padding byte.
payloadBytes = (payloadBytes & ^(blockSize - 1)) - 1
// The MAC is appended before padding so affects the
// payload size directly.
payloadBytes -= macSize
default:
panic("unknown cipher type")
}
}
// Allow packet growth in arithmetic progression up to max.
pkt := c.packetsSent
c.packetsSent++
if pkt > 1000 {
return maxPlaintext // avoid overflow in multiply below
}
n := payloadBytes * int(pkt+1)
if n > maxPlaintext {
n = maxPlaintext
}
return n
}
// c.out.Mutex <= L.
func (c *Conn) write(data []byte) (int, error) {
if c.buffering {
c.sendBuf = append(c.sendBuf, data...)
return len(data), nil
}
n, err := c.conn.Write(data)
c.bytesSent += int64(n)
return n, err
}
func (c *Conn) flush() (int, error) {
if len(c.sendBuf) == 0 {
return 0, nil
}
n, err := c.conn.Write(c.sendBuf)
c.bytesSent += int64(n)
c.sendBuf = nil
c.buffering = false
return n, err
}
// writeRecordLocked 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) writeRecordLocked(typ recordType, data []byte) (int, error) {
b := c.out.newBlock()
defer c.out.freeBlock(b)
var n int
for len(data) > 0 {
explicitIVLen := 0
explicitIVIsSeq := 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 c, ok := c.out.cipher.(aead); ok {
explicitIVLen = c.explicitNonceLen()
// 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 = explicitIVLen > 0
}
}
m := len(data)
if maxPayload := c.maxPayloadSizeForWrite(typ, explicitIVLen); m > maxPayload {
m = maxPayload
}
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 {
return n, err
}
}
}
copy(b.data[recordHeaderLen+explicitIVLen:], data)
c.out.encrypt(b, explicitIVLen)
if _, err := c.write(b.data); err != nil {
return n, err
}
n += m
data = data[m:]
}
if typ == recordTypeChangeCipherSpec {
if err := c.out.changeCipherSpec(); err != nil {
return n, c.sendAlertLocked(err.(alert))
}
}
return n, nil
}
// writeRecord writes a TLS record with the given type and payload to the
// connection and updates the record layer state.
// L < c.out.Mutex.
func (c *Conn) writeRecord(typ recordType, data []byte) (int, error) {
c.out.Lock()
defer c.out.Unlock()
return c.writeRecordLocked(typ, data)
}
// readHandshake reads the next handshake message from
// the record layer.
// c.in.Mutex < L; c.out.Mutex < L.
func (c *Conn) readHandshake() (interface{}, error) {
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 {
c.sendAlertLocked(alertInternalError)
return nil, c.in.setErrorLocked(fmt.Errorf("tls: handshake message of length %d bytes exceeds maximum of %d bytes", n, maxHandshake))
}
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
}
}
data = c.hand.Next(4 + n)
var m handshakeMessage
switch data[0] {
case typeHelloRequest:
m = new(helloRequestMsg)
case typeClientHello:
m = new(clientHelloMsg)
case typeServerHello:
m = new(serverHelloMsg)
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)
default:
return nil, c.in.setErrorLocked(c.sendAlert(alertUnexpectedMessage))
}
// The handshake message unmarshalers
// 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
}
var (
errClosed = errors.New("tls: use of closed connection")
errShutdown = errors.New("tls: protocol is shutdown")
)
// Write writes data to the connection.
func (c *Conn) Write(b []byte) (int, error) {
// interlock with Close below
for {
x := atomic.LoadInt32(&c.activeCall)
if x&1 != 0 {
return 0, errClosed
}
if atomic.CompareAndSwapInt32(&c.activeCall, x, x+2) {
defer atomic.AddInt32(&c.activeCall, -2)
break
}
}
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.closeNotifySent {
return 0, errShutdown
}
// 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 {
if _, ok := c.out.cipher.(cipher.BlockMode); ok {
n, err := c.writeRecordLocked(recordTypeApplicationData, b[:1])
if err != nil {
return n, c.out.setErrorLocked(err)
}
m, b = 1, b[1:]
}
}
n, err := c.writeRecordLocked(recordTypeApplicationData, b)
return n + m, c.out.setErrorLocked(err)
}
// handleRenegotiation processes a HelloRequest handshake message.
// c.in.Mutex <= L
func (c *Conn) handleRenegotiation() error {
msg, err := c.readHandshake()
if err != nil {
return err
}
_, ok := msg.(*helloRequestMsg)
if !ok {
c.sendAlert(alertUnexpectedMessage)
return alertUnexpectedMessage
}
if !c.isClient {
return c.sendAlert(alertNoRenegotiation)
}
switch c.config.Renegotiation {
case RenegotiateNever:
return c.sendAlert(alertNoRenegotiation)
case RenegotiateOnceAsClient:
if c.handshakes > 1 {
return c.sendAlert(alertNoRenegotiation)
}
case RenegotiateFreelyAsClient:
// Ok.
default:
c.sendAlert(alertInternalError)
return errors.New("tls: unknown Renegotiation value")
}
c.handshakeMutex.Lock()
defer c.handshakeMutex.Unlock()
c.handshakeComplete = false
if c.handshakeErr = c.clientHandshake(); c.handshakeErr == nil {
c.handshakes++
}
return c.handshakeErr
}
// 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
}
if len(b) == 0 {
// Put this after Handshake, in case people were calling
// Read(nil) for the side effect of the Handshake.
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
}
}
}
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.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 https://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 {
// Interlock with Conn.Write above.
var x int32
for {
x = atomic.LoadInt32(&c.activeCall)
if x&1 != 0 {
return errClosed
}
if atomic.CompareAndSwapInt32(&c.activeCall, x, x|1) {
break
}
}
if x != 0 {
// io.Writer and io.Closer should not be used concurrently.
// If Close is called while a Write is currently in-flight,
// interpret that as a sign that this Close is really just
// being used to break the Write and/or clean up resources and
// avoid sending the alertCloseNotify, which may block
// waiting on handshakeMutex or the c.out mutex.
return c.conn.Close()
}
var alertErr error
c.handshakeMutex.Lock()
if c.handshakeComplete {
alertErr = c.closeNotify()
}
c.handshakeMutex.Unlock()
if err := c.conn.Close(); err != nil {
return err
}
return alertErr
}
var errEarlyCloseWrite = errors.New("tls: CloseWrite called before handshake complete")
// CloseWrite shuts down the writing side of the connection. It should only be
// called once the handshake has completed and does not call CloseWrite on the
// underlying connection. Most callers should just use Close.
func (c *Conn) CloseWrite() error {
c.handshakeMutex.Lock()
defer c.handshakeMutex.Unlock()
if !c.handshakeComplete {
return errEarlyCloseWrite
}
return c.closeNotify()
}
func (c *Conn) closeNotify() error {
c.out.Lock()
defer c.out.Unlock()
if !c.closeNotifySent {
c.closeNotifyErr = c.sendAlertLocked(alertCloseNotify)
c.closeNotifySent = true
}
return c.closeNotifyErr
}
// 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.handshakeErr and c.handshakeComplete are protected by
// c.handshakeMutex. In order to perform a handshake, we need to lock
// c.in also and c.handshakeMutex must be locked after c.in.
//
// However, if a Read() operation is hanging then it'll be holding the
// lock on c.in and so taking it here would cause all operations that
// need to check whether a handshake is pending (such as Write) to
// block.
//
// Thus we first take c.handshakeMutex to check whether a handshake is
// needed.
//
// If so then, previously, this code would unlock handshakeMutex and
// then lock c.in and handshakeMutex in the correct order to run the
// handshake. The problem was that it was possible for a Read to
// complete the handshake once handshakeMutex was unlocked and then
// keep c.in while waiting for network data. Thus a concurrent
// operation could be blocked on c.in.
//
// Thus handshakeCond is used to signal that a goroutine is committed
// to running the handshake and other goroutines can wait on it if they
// need. handshakeCond is protected by handshakeMutex.
c.handshakeMutex.Lock()
defer c.handshakeMutex.Unlock()
for {
if err := c.handshakeErr; err != nil {
return err
}
if c.handshakeComplete {
return nil
}
if c.handshakeCond == nil {
break
}
c.handshakeCond.Wait()
}
// Set handshakeCond to indicate that this goroutine is committing to
// running the handshake.
c.handshakeCond = sync.NewCond(&c.handshakeMutex)
c.handshakeMutex.Unlock()
c.in.Lock()
defer c.in.Unlock()
c.handshakeMutex.Lock()
// The handshake cannot have completed when handshakeMutex was unlocked
// because this goroutine set handshakeCond.
if c.handshakeErr != nil || c.handshakeComplete {
panic("handshake should not have been able to complete after handshakeCond was set")
}
if c.isClient {
c.handshakeErr = c.clientHandshake()
} else {
c.handshakeErr = c.serverHandshake()
}
if c.handshakeErr == nil {
c.handshakes++
} else {
// If an error occurred during the hadshake try to flush the
// alert that might be left in the buffer.
c.flush()
}
if c.handshakeErr == nil && !c.handshakeComplete {
panic("handshake should have had a result.")
}
// Wake any other goroutines that are waiting for this handshake to
// complete.
c.handshakeCond.Broadcast()
c.handshakeCond = nil
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
state.ServerName = c.serverName
if c.handshakeComplete {
state.Version = c.vers
state.NegotiatedProtocol = c.clientProtocol
state.DidResume = c.didResume
state.NegotiatedProtocolIsMutual = !c.clientProtocolFallback
state.CipherSuite = c.cipherSuite
state.PeerCertificates = c.peerCertificates
state.VerifiedChains = c.verifiedChains
state.SignedCertificateTimestamps = c.scts
state.OCSPResponse = c.ocspResponse
if !c.didResume {
if c.clientFinishedIsFirst {
state.TLSUnique = c.clientFinished[:]
} else {
state.TLSUnique = c.serverFinished[:]
}
}
}
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")
}
if len(c.verifiedChains) == 0 {
return errors.New("tls: handshake did not verify certificate chain")
}
return c.peerCertificates[0].VerifyHostname(host)
}