Source file src/crypto/tls/conn.go

     1  // Copyright 2010 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  // TLS low level connection and record layer
     6  
     7  package tls
     8  
     9  import (
    10  	"bytes"
    11  	"context"
    12  	"crypto/cipher"
    13  	"crypto/subtle"
    14  	"crypto/x509"
    15  	"errors"
    16  	"fmt"
    17  	"hash"
    18  	"io"
    19  	"net"
    20  	"sync"
    21  	"sync/atomic"
    22  	"time"
    23  )
    24  
    25  // A Conn represents a secured connection.
    26  // It implements the net.Conn interface.
    27  type Conn struct {
    28  	// constant
    29  	conn        net.Conn
    30  	isClient    bool
    31  	handshakeFn func(context.Context) error // (*Conn).clientHandshake or serverHandshake
    32  
    33  	// handshakeStatus is 1 if the connection is currently transferring
    34  	// application data (i.e. is not currently processing a handshake).
    35  	// This field is only to be accessed with sync/atomic.
    36  	handshakeStatus uint32
    37  	// constant after handshake; protected by handshakeMutex
    38  	handshakeMutex sync.Mutex
    39  	handshakeErr   error   // error resulting from handshake
    40  	vers           uint16  // TLS version
    41  	haveVers       bool    // version has been negotiated
    42  	config         *Config // configuration passed to constructor
    43  	// handshakes counts the number of handshakes performed on the
    44  	// connection so far. If renegotiation is disabled then this is either
    45  	// zero or one.
    46  	handshakes       int
    47  	didResume        bool // whether this connection was a session resumption
    48  	cipherSuite      uint16
    49  	ocspResponse     []byte   // stapled OCSP response
    50  	scts             [][]byte // signed certificate timestamps from server
    51  	peerCertificates []*x509.Certificate
    52  	// verifiedChains contains the certificate chains that we built, as
    53  	// opposed to the ones presented by the server.
    54  	verifiedChains [][]*x509.Certificate
    55  	// serverName contains the server name indicated by the client, if any.
    56  	serverName string
    57  	// secureRenegotiation is true if the server echoed the secure
    58  	// renegotiation extension. (This is meaningless as a server because
    59  	// renegotiation is not supported in that case.)
    60  	secureRenegotiation bool
    61  	// ekm is a closure for exporting keying material.
    62  	ekm func(label string, context []byte, length int) ([]byte, error)
    63  	// resumptionSecret is the resumption_master_secret for handling
    64  	// NewSessionTicket messages. nil if config.SessionTicketsDisabled.
    65  	resumptionSecret []byte
    66  
    67  	// ticketKeys is the set of active session ticket keys for this
    68  	// connection. The first one is used to encrypt new tickets and
    69  	// all are tried to decrypt tickets.
    70  	ticketKeys []ticketKey
    71  
    72  	// clientFinishedIsFirst is true if the client sent the first Finished
    73  	// message during the most recent handshake. This is recorded because
    74  	// the first transmitted Finished message is the tls-unique
    75  	// channel-binding value.
    76  	clientFinishedIsFirst bool
    77  
    78  	// closeNotifyErr is any error from sending the alertCloseNotify record.
    79  	closeNotifyErr error
    80  	// closeNotifySent is true if the Conn attempted to send an
    81  	// alertCloseNotify record.
    82  	closeNotifySent bool
    83  
    84  	// clientFinished and serverFinished contain the Finished message sent
    85  	// by the client or server in the most recent handshake. This is
    86  	// retained to support the renegotiation extension and tls-unique
    87  	// channel-binding.
    88  	clientFinished [12]byte
    89  	serverFinished [12]byte
    90  
    91  	// clientProtocol is the negotiated ALPN protocol.
    92  	clientProtocol string
    93  
    94  	// input/output
    95  	in, out   halfConn
    96  	rawInput  bytes.Buffer // raw input, starting with a record header
    97  	input     bytes.Reader // application data waiting to be read, from rawInput.Next
    98  	hand      bytes.Buffer // handshake data waiting to be read
    99  	buffering bool         // whether records are buffered in sendBuf
   100  	sendBuf   []byte       // a buffer of records waiting to be sent
   101  
   102  	// bytesSent counts the bytes of application data sent.
   103  	// packetsSent counts packets.
   104  	bytesSent   int64
   105  	packetsSent int64
   106  
   107  	// retryCount counts the number of consecutive non-advancing records
   108  	// received by Conn.readRecord. That is, records that neither advance the
   109  	// handshake, nor deliver application data. Protected by in.Mutex.
   110  	retryCount int
   111  
   112  	// activeCall is an atomic int32; the low bit is whether Close has
   113  	// been called. the rest of the bits are the number of goroutines
   114  	// in Conn.Write.
   115  	activeCall int32
   116  
   117  	tmp [16]byte
   118  }
   119  
   120  // Access to net.Conn methods.
   121  // Cannot just embed net.Conn because that would
   122  // export the struct field too.
   123  
   124  // LocalAddr returns the local network address.
   125  func (c *Conn) LocalAddr() net.Addr {
   126  	return c.conn.LocalAddr()
   127  }
   128  
   129  // RemoteAddr returns the remote network address.
   130  func (c *Conn) RemoteAddr() net.Addr {
   131  	return c.conn.RemoteAddr()
   132  }
   133  
   134  // SetDeadline sets the read and write deadlines associated with the connection.
   135  // A zero value for t means Read and Write will not time out.
   136  // After a Write has timed out, the TLS state is corrupt and all future writes will return the same error.
   137  func (c *Conn) SetDeadline(t time.Time) error {
   138  	return c.conn.SetDeadline(t)
   139  }
   140  
   141  // SetReadDeadline sets the read deadline on the underlying connection.
   142  // A zero value for t means Read will not time out.
   143  func (c *Conn) SetReadDeadline(t time.Time) error {
   144  	return c.conn.SetReadDeadline(t)
   145  }
   146  
   147  // SetWriteDeadline sets the write deadline on the underlying connection.
   148  // A zero value for t means Write will not time out.
   149  // After a Write has timed out, the TLS state is corrupt and all future writes will return the same error.
   150  func (c *Conn) SetWriteDeadline(t time.Time) error {
   151  	return c.conn.SetWriteDeadline(t)
   152  }
   153  
   154  // NetConn returns the underlying connection that is wrapped by c.
   155  // Note that writing to or reading from this connection directly will corrupt the
   156  // TLS session.
   157  func (c *Conn) NetConn() net.Conn {
   158  	return c.conn
   159  }
   160  
   161  // A halfConn represents one direction of the record layer
   162  // connection, either sending or receiving.
   163  type halfConn struct {
   164  	sync.Mutex
   165  
   166  	err     error  // first permanent error
   167  	version uint16 // protocol version
   168  	cipher  any    // cipher algorithm
   169  	mac     hash.Hash
   170  	seq     [8]byte // 64-bit sequence number
   171  
   172  	scratchBuf [13]byte // to avoid allocs; interface method args escape
   173  
   174  	nextCipher any       // next encryption state
   175  	nextMac    hash.Hash // next MAC algorithm
   176  
   177  	trafficSecret []byte // current TLS 1.3 traffic secret
   178  }
   179  
   180  type permanentError struct {
   181  	err net.Error
   182  }
   183  
   184  func (e *permanentError) Error() string   { return e.err.Error() }
   185  func (e *permanentError) Unwrap() error   { return e.err }
   186  func (e *permanentError) Timeout() bool   { return e.err.Timeout() }
   187  func (e *permanentError) Temporary() bool { return false }
   188  
   189  func (hc *halfConn) setErrorLocked(err error) error {
   190  	if e, ok := err.(net.Error); ok {
   191  		hc.err = &permanentError{err: e}
   192  	} else {
   193  		hc.err = err
   194  	}
   195  	return hc.err
   196  }
   197  
   198  // prepareCipherSpec sets the encryption and MAC states
   199  // that a subsequent changeCipherSpec will use.
   200  func (hc *halfConn) prepareCipherSpec(version uint16, cipher any, mac hash.Hash) {
   201  	hc.version = version
   202  	hc.nextCipher = cipher
   203  	hc.nextMac = mac
   204  }
   205  
   206  // changeCipherSpec changes the encryption and MAC states
   207  // to the ones previously passed to prepareCipherSpec.
   208  func (hc *halfConn) changeCipherSpec() error {
   209  	if hc.nextCipher == nil || hc.version == VersionTLS13 {
   210  		return alertInternalError
   211  	}
   212  	hc.cipher = hc.nextCipher
   213  	hc.mac = hc.nextMac
   214  	hc.nextCipher = nil
   215  	hc.nextMac = nil
   216  	for i := range hc.seq {
   217  		hc.seq[i] = 0
   218  	}
   219  	return nil
   220  }
   221  
   222  func (hc *halfConn) setTrafficSecret(suite *cipherSuiteTLS13, secret []byte) {
   223  	hc.trafficSecret = secret
   224  	key, iv := suite.trafficKey(secret)
   225  	hc.cipher = suite.aead(key, iv)
   226  	for i := range hc.seq {
   227  		hc.seq[i] = 0
   228  	}
   229  }
   230  
   231  // incSeq increments the sequence number.
   232  func (hc *halfConn) incSeq() {
   233  	for i := 7; i >= 0; i-- {
   234  		hc.seq[i]++
   235  		if hc.seq[i] != 0 {
   236  			return
   237  		}
   238  	}
   239  
   240  	// Not allowed to let sequence number wrap.
   241  	// Instead, must renegotiate before it does.
   242  	// Not likely enough to bother.
   243  	panic("TLS: sequence number wraparound")
   244  }
   245  
   246  // explicitNonceLen returns the number of bytes of explicit nonce or IV included
   247  // in each record. Explicit nonces are present only in CBC modes after TLS 1.0
   248  // and in certain AEAD modes in TLS 1.2.
   249  func (hc *halfConn) explicitNonceLen() int {
   250  	if hc.cipher == nil {
   251  		return 0
   252  	}
   253  
   254  	switch c := hc.cipher.(type) {
   255  	case cipher.Stream:
   256  		return 0
   257  	case aead:
   258  		return c.explicitNonceLen()
   259  	case cbcMode:
   260  		// TLS 1.1 introduced a per-record explicit IV to fix the BEAST attack.
   261  		if hc.version >= VersionTLS11 {
   262  			return c.BlockSize()
   263  		}
   264  		return 0
   265  	default:
   266  		panic("unknown cipher type")
   267  	}
   268  }
   269  
   270  // extractPadding returns, in constant time, the length of the padding to remove
   271  // from the end of payload. It also returns a byte which is equal to 255 if the
   272  // padding was valid and 0 otherwise. See RFC 2246, Section 6.2.3.2.
   273  func extractPadding(payload []byte) (toRemove int, good byte) {
   274  	if len(payload) < 1 {
   275  		return 0, 0
   276  	}
   277  
   278  	paddingLen := payload[len(payload)-1]
   279  	t := uint(len(payload)-1) - uint(paddingLen)
   280  	// if len(payload) >= (paddingLen - 1) then the MSB of t is zero
   281  	good = byte(int32(^t) >> 31)
   282  
   283  	// The maximum possible padding length plus the actual length field
   284  	toCheck := 256
   285  	// The length of the padded data is public, so we can use an if here
   286  	if toCheck > len(payload) {
   287  		toCheck = len(payload)
   288  	}
   289  
   290  	for i := 0; i < toCheck; i++ {
   291  		t := uint(paddingLen) - uint(i)
   292  		// if i <= paddingLen then the MSB of t is zero
   293  		mask := byte(int32(^t) >> 31)
   294  		b := payload[len(payload)-1-i]
   295  		good &^= mask&paddingLen ^ mask&b
   296  	}
   297  
   298  	// We AND together the bits of good and replicate the result across
   299  	// all the bits.
   300  	good &= good << 4
   301  	good &= good << 2
   302  	good &= good << 1
   303  	good = uint8(int8(good) >> 7)
   304  
   305  	// Zero the padding length on error. This ensures any unchecked bytes
   306  	// are included in the MAC. Otherwise, an attacker that could
   307  	// distinguish MAC failures from padding failures could mount an attack
   308  	// similar to POODLE in SSL 3.0: given a good ciphertext that uses a
   309  	// full block's worth of padding, replace the final block with another
   310  	// block. If the MAC check passed but the padding check failed, the
   311  	// last byte of that block decrypted to the block size.
   312  	//
   313  	// See also macAndPaddingGood logic below.
   314  	paddingLen &= good
   315  
   316  	toRemove = int(paddingLen) + 1
   317  	return
   318  }
   319  
   320  func roundUp(a, b int) int {
   321  	return a + (b-a%b)%b
   322  }
   323  
   324  // cbcMode is an interface for block ciphers using cipher block chaining.
   325  type cbcMode interface {
   326  	cipher.BlockMode
   327  	SetIV([]byte)
   328  }
   329  
   330  // decrypt authenticates and decrypts the record if protection is active at
   331  // this stage. The returned plaintext might overlap with the input.
   332  func (hc *halfConn) decrypt(record []byte) ([]byte, recordType, error) {
   333  	var plaintext []byte
   334  	typ := recordType(record[0])
   335  	payload := record[recordHeaderLen:]
   336  
   337  	// In TLS 1.3, change_cipher_spec messages are to be ignored without being
   338  	// decrypted. See RFC 8446, Appendix D.4.
   339  	if hc.version == VersionTLS13 && typ == recordTypeChangeCipherSpec {
   340  		return payload, typ, nil
   341  	}
   342  
   343  	paddingGood := byte(255)
   344  	paddingLen := 0
   345  
   346  	explicitNonceLen := hc.explicitNonceLen()
   347  
   348  	if hc.cipher != nil {
   349  		switch c := hc.cipher.(type) {
   350  		case cipher.Stream:
   351  			c.XORKeyStream(payload, payload)
   352  		case aead:
   353  			if len(payload) < explicitNonceLen {
   354  				return nil, 0, alertBadRecordMAC
   355  			}
   356  			nonce := payload[:explicitNonceLen]
   357  			if len(nonce) == 0 {
   358  				nonce = hc.seq[:]
   359  			}
   360  			payload = payload[explicitNonceLen:]
   361  
   362  			var additionalData []byte
   363  			if hc.version == VersionTLS13 {
   364  				additionalData = record[:recordHeaderLen]
   365  			} else {
   366  				additionalData = append(hc.scratchBuf[:0], hc.seq[:]...)
   367  				additionalData = append(additionalData, record[:3]...)
   368  				n := len(payload) - c.Overhead()
   369  				additionalData = append(additionalData, byte(n>>8), byte(n))
   370  			}
   371  
   372  			var err error
   373  			plaintext, err = c.Open(payload[:0], nonce, payload, additionalData)
   374  			if err != nil {
   375  				return nil, 0, alertBadRecordMAC
   376  			}
   377  		case cbcMode:
   378  			blockSize := c.BlockSize()
   379  			minPayload := explicitNonceLen + roundUp(hc.mac.Size()+1, blockSize)
   380  			if len(payload)%blockSize != 0 || len(payload) < minPayload {
   381  				return nil, 0, alertBadRecordMAC
   382  			}
   383  
   384  			if explicitNonceLen > 0 {
   385  				c.SetIV(payload[:explicitNonceLen])
   386  				payload = payload[explicitNonceLen:]
   387  			}
   388  			c.CryptBlocks(payload, payload)
   389  
   390  			// In a limited attempt to protect against CBC padding oracles like
   391  			// Lucky13, the data past paddingLen (which is secret) is passed to
   392  			// the MAC function as extra data, to be fed into the HMAC after
   393  			// computing the digest. This makes the MAC roughly constant time as
   394  			// long as the digest computation is constant time and does not
   395  			// affect the subsequent write, modulo cache effects.
   396  			paddingLen, paddingGood = extractPadding(payload)
   397  		default:
   398  			panic("unknown cipher type")
   399  		}
   400  
   401  		if hc.version == VersionTLS13 {
   402  			if typ != recordTypeApplicationData {
   403  				return nil, 0, alertUnexpectedMessage
   404  			}
   405  			if len(plaintext) > maxPlaintext+1 {
   406  				return nil, 0, alertRecordOverflow
   407  			}
   408  			// Remove padding and find the ContentType scanning from the end.
   409  			for i := len(plaintext) - 1; i >= 0; i-- {
   410  				if plaintext[i] != 0 {
   411  					typ = recordType(plaintext[i])
   412  					plaintext = plaintext[:i]
   413  					break
   414  				}
   415  				if i == 0 {
   416  					return nil, 0, alertUnexpectedMessage
   417  				}
   418  			}
   419  		}
   420  	} else {
   421  		plaintext = payload
   422  	}
   423  
   424  	if hc.mac != nil {
   425  		macSize := hc.mac.Size()
   426  		if len(payload) < macSize {
   427  			return nil, 0, alertBadRecordMAC
   428  		}
   429  
   430  		n := len(payload) - macSize - paddingLen
   431  		n = subtle.ConstantTimeSelect(int(uint32(n)>>31), 0, n) // if n < 0 { n = 0 }
   432  		record[3] = byte(n >> 8)
   433  		record[4] = byte(n)
   434  		remoteMAC := payload[n : n+macSize]
   435  		localMAC := tls10MAC(hc.mac, hc.scratchBuf[:0], hc.seq[:], record[:recordHeaderLen], payload[:n], payload[n+macSize:])
   436  
   437  		// This is equivalent to checking the MACs and paddingGood
   438  		// separately, but in constant-time to prevent distinguishing
   439  		// padding failures from MAC failures. Depending on what value
   440  		// of paddingLen was returned on bad padding, distinguishing
   441  		// bad MAC from bad padding can lead to an attack.
   442  		//
   443  		// See also the logic at the end of extractPadding.
   444  		macAndPaddingGood := subtle.ConstantTimeCompare(localMAC, remoteMAC) & int(paddingGood)
   445  		if macAndPaddingGood != 1 {
   446  			return nil, 0, alertBadRecordMAC
   447  		}
   448  
   449  		plaintext = payload[:n]
   450  	}
   451  
   452  	hc.incSeq()
   453  	return plaintext, typ, nil
   454  }
   455  
   456  // sliceForAppend extends the input slice by n bytes. head is the full extended
   457  // slice, while tail is the appended part. If the original slice has sufficient
   458  // capacity no allocation is performed.
   459  func sliceForAppend(in []byte, n int) (head, tail []byte) {
   460  	if total := len(in) + n; cap(in) >= total {
   461  		head = in[:total]
   462  	} else {
   463  		head = make([]byte, total)
   464  		copy(head, in)
   465  	}
   466  	tail = head[len(in):]
   467  	return
   468  }
   469  
   470  // encrypt encrypts payload, adding the appropriate nonce and/or MAC, and
   471  // appends it to record, which must already contain the record header.
   472  func (hc *halfConn) encrypt(record, payload []byte, rand io.Reader) ([]byte, error) {
   473  	if hc.cipher == nil {
   474  		return append(record, payload...), nil
   475  	}
   476  
   477  	var explicitNonce []byte
   478  	if explicitNonceLen := hc.explicitNonceLen(); explicitNonceLen > 0 {
   479  		record, explicitNonce = sliceForAppend(record, explicitNonceLen)
   480  		if _, isCBC := hc.cipher.(cbcMode); !isCBC && explicitNonceLen < 16 {
   481  			// The AES-GCM construction in TLS has an explicit nonce so that the
   482  			// nonce can be random. However, the nonce is only 8 bytes which is
   483  			// too small for a secure, random nonce. Therefore we use the
   484  			// sequence number as the nonce. The 3DES-CBC construction also has
   485  			// an 8 bytes nonce but its nonces must be unpredictable (see RFC
   486  			// 5246, Appendix F.3), forcing us to use randomness. That's not
   487  			// 3DES' biggest problem anyway because the birthday bound on block
   488  			// collision is reached first due to its similarly small block size
   489  			// (see the Sweet32 attack).
   490  			copy(explicitNonce, hc.seq[:])
   491  		} else {
   492  			if _, err := io.ReadFull(rand, explicitNonce); err != nil {
   493  				return nil, err
   494  			}
   495  		}
   496  	}
   497  
   498  	var dst []byte
   499  	switch c := hc.cipher.(type) {
   500  	case cipher.Stream:
   501  		mac := tls10MAC(hc.mac, hc.scratchBuf[:0], hc.seq[:], record[:recordHeaderLen], payload, nil)
   502  		record, dst = sliceForAppend(record, len(payload)+len(mac))
   503  		c.XORKeyStream(dst[:len(payload)], payload)
   504  		c.XORKeyStream(dst[len(payload):], mac)
   505  	case aead:
   506  		nonce := explicitNonce
   507  		if len(nonce) == 0 {
   508  			nonce = hc.seq[:]
   509  		}
   510  
   511  		if hc.version == VersionTLS13 {
   512  			record = append(record, payload...)
   513  
   514  			// Encrypt the actual ContentType and replace the plaintext one.
   515  			record = append(record, record[0])
   516  			record[0] = byte(recordTypeApplicationData)
   517  
   518  			n := len(payload) + 1 + c.Overhead()
   519  			record[3] = byte(n >> 8)
   520  			record[4] = byte(n)
   521  
   522  			record = c.Seal(record[:recordHeaderLen],
   523  				nonce, record[recordHeaderLen:], record[:recordHeaderLen])
   524  		} else {
   525  			additionalData := append(hc.scratchBuf[:0], hc.seq[:]...)
   526  			additionalData = append(additionalData, record[:recordHeaderLen]...)
   527  			record = c.Seal(record, nonce, payload, additionalData)
   528  		}
   529  	case cbcMode:
   530  		mac := tls10MAC(hc.mac, hc.scratchBuf[:0], hc.seq[:], record[:recordHeaderLen], payload, nil)
   531  		blockSize := c.BlockSize()
   532  		plaintextLen := len(payload) + len(mac)
   533  		paddingLen := blockSize - plaintextLen%blockSize
   534  		record, dst = sliceForAppend(record, plaintextLen+paddingLen)
   535  		copy(dst, payload)
   536  		copy(dst[len(payload):], mac)
   537  		for i := plaintextLen; i < len(dst); i++ {
   538  			dst[i] = byte(paddingLen - 1)
   539  		}
   540  		if len(explicitNonce) > 0 {
   541  			c.SetIV(explicitNonce)
   542  		}
   543  		c.CryptBlocks(dst, dst)
   544  	default:
   545  		panic("unknown cipher type")
   546  	}
   547  
   548  	// Update length to include nonce, MAC and any block padding needed.
   549  	n := len(record) - recordHeaderLen
   550  	record[3] = byte(n >> 8)
   551  	record[4] = byte(n)
   552  	hc.incSeq()
   553  
   554  	return record, nil
   555  }
   556  
   557  // RecordHeaderError is returned when a TLS record header is invalid.
   558  type RecordHeaderError struct {
   559  	// Msg contains a human readable string that describes the error.
   560  	Msg string
   561  	// RecordHeader contains the five bytes of TLS record header that
   562  	// triggered the error.
   563  	RecordHeader [5]byte
   564  	// Conn provides the underlying net.Conn in the case that a client
   565  	// sent an initial handshake that didn't look like TLS.
   566  	// It is nil if there's already been a handshake or a TLS alert has
   567  	// been written to the connection.
   568  	Conn net.Conn
   569  }
   570  
   571  func (e RecordHeaderError) Error() string { return "tls: " + e.Msg }
   572  
   573  func (c *Conn) newRecordHeaderError(conn net.Conn, msg string) (err RecordHeaderError) {
   574  	err.Msg = msg
   575  	err.Conn = conn
   576  	copy(err.RecordHeader[:], c.rawInput.Bytes())
   577  	return err
   578  }
   579  
   580  func (c *Conn) readRecord() error {
   581  	return c.readRecordOrCCS(false)
   582  }
   583  
   584  func (c *Conn) readChangeCipherSpec() error {
   585  	return c.readRecordOrCCS(true)
   586  }
   587  
   588  // readRecordOrCCS reads one or more TLS records from the connection and
   589  // updates the record layer state. Some invariants:
   590  //   * c.in must be locked
   591  //   * c.input must be empty
   592  // During the handshake one and only one of the following will happen:
   593  //   - c.hand grows
   594  //   - c.in.changeCipherSpec is called
   595  //   - an error is returned
   596  // After the handshake one and only one of the following will happen:
   597  //   - c.hand grows
   598  //   - c.input is set
   599  //   - an error is returned
   600  func (c *Conn) readRecordOrCCS(expectChangeCipherSpec bool) error {
   601  	if c.in.err != nil {
   602  		return c.in.err
   603  	}
   604  	handshakeComplete := c.handshakeComplete()
   605  
   606  	// This function modifies c.rawInput, which owns the c.input memory.
   607  	if c.input.Len() != 0 {
   608  		return c.in.setErrorLocked(errors.New("tls: internal error: attempted to read record with pending application data"))
   609  	}
   610  	c.input.Reset(nil)
   611  
   612  	// Read header, payload.
   613  	if err := c.readFromUntil(c.conn, recordHeaderLen); err != nil {
   614  		// RFC 8446, Section 6.1 suggests that EOF without an alertCloseNotify
   615  		// is an error, but popular web sites seem to do this, so we accept it
   616  		// if and only if at the record boundary.
   617  		if err == io.ErrUnexpectedEOF && c.rawInput.Len() == 0 {
   618  			err = io.EOF
   619  		}
   620  		if e, ok := err.(net.Error); !ok || !e.Temporary() {
   621  			c.in.setErrorLocked(err)
   622  		}
   623  		return err
   624  	}
   625  	hdr := c.rawInput.Bytes()[:recordHeaderLen]
   626  	typ := recordType(hdr[0])
   627  
   628  	// No valid TLS record has a type of 0x80, however SSLv2 handshakes
   629  	// start with a uint16 length where the MSB is set and the first record
   630  	// is always < 256 bytes long. Therefore typ == 0x80 strongly suggests
   631  	// an SSLv2 client.
   632  	if !handshakeComplete && typ == 0x80 {
   633  		c.sendAlert(alertProtocolVersion)
   634  		return c.in.setErrorLocked(c.newRecordHeaderError(nil, "unsupported SSLv2 handshake received"))
   635  	}
   636  
   637  	vers := uint16(hdr[1])<<8 | uint16(hdr[2])
   638  	n := int(hdr[3])<<8 | int(hdr[4])
   639  	if c.haveVers && c.vers != VersionTLS13 && vers != c.vers {
   640  		c.sendAlert(alertProtocolVersion)
   641  		msg := fmt.Sprintf("received record with version %x when expecting version %x", vers, c.vers)
   642  		return c.in.setErrorLocked(c.newRecordHeaderError(nil, msg))
   643  	}
   644  	if !c.haveVers {
   645  		// First message, be extra suspicious: this might not be a TLS
   646  		// client. Bail out before reading a full 'body', if possible.
   647  		// The current max version is 3.3 so if the version is >= 16.0,
   648  		// it's probably not real.
   649  		if (typ != recordTypeAlert && typ != recordTypeHandshake) || vers >= 0x1000 {
   650  			return c.in.setErrorLocked(c.newRecordHeaderError(c.conn, "first record does not look like a TLS handshake"))
   651  		}
   652  	}
   653  	if c.vers == VersionTLS13 && n > maxCiphertextTLS13 || n > maxCiphertext {
   654  		c.sendAlert(alertRecordOverflow)
   655  		msg := fmt.Sprintf("oversized record received with length %d", n)
   656  		return c.in.setErrorLocked(c.newRecordHeaderError(nil, msg))
   657  	}
   658  	if err := c.readFromUntil(c.conn, recordHeaderLen+n); err != nil {
   659  		if e, ok := err.(net.Error); !ok || !e.Temporary() {
   660  			c.in.setErrorLocked(err)
   661  		}
   662  		return err
   663  	}
   664  
   665  	// Process message.
   666  	record := c.rawInput.Next(recordHeaderLen + n)
   667  	data, typ, err := c.in.decrypt(record)
   668  	if err != nil {
   669  		return c.in.setErrorLocked(c.sendAlert(err.(alert)))
   670  	}
   671  	if len(data) > maxPlaintext {
   672  		return c.in.setErrorLocked(c.sendAlert(alertRecordOverflow))
   673  	}
   674  
   675  	// Application Data messages are always protected.
   676  	if c.in.cipher == nil && typ == recordTypeApplicationData {
   677  		return c.in.setErrorLocked(c.sendAlert(alertUnexpectedMessage))
   678  	}
   679  
   680  	if typ != recordTypeAlert && typ != recordTypeChangeCipherSpec && len(data) > 0 {
   681  		// This is a state-advancing message: reset the retry count.
   682  		c.retryCount = 0
   683  	}
   684  
   685  	// Handshake messages MUST NOT be interleaved with other record types in TLS 1.3.
   686  	if c.vers == VersionTLS13 && typ != recordTypeHandshake && c.hand.Len() > 0 {
   687  		return c.in.setErrorLocked(c.sendAlert(alertUnexpectedMessage))
   688  	}
   689  
   690  	switch typ {
   691  	default:
   692  		return c.in.setErrorLocked(c.sendAlert(alertUnexpectedMessage))
   693  
   694  	case recordTypeAlert:
   695  		if len(data) != 2 {
   696  			return c.in.setErrorLocked(c.sendAlert(alertUnexpectedMessage))
   697  		}
   698  		if alert(data[1]) == alertCloseNotify {
   699  			return c.in.setErrorLocked(io.EOF)
   700  		}
   701  		if c.vers == VersionTLS13 {
   702  			return c.in.setErrorLocked(&net.OpError{Op: "remote error", Err: alert(data[1])})
   703  		}
   704  		switch data[0] {
   705  		case alertLevelWarning:
   706  			// Drop the record on the floor and retry.
   707  			return c.retryReadRecord(expectChangeCipherSpec)
   708  		case alertLevelError:
   709  			return c.in.setErrorLocked(&net.OpError{Op: "remote error", Err: alert(data[1])})
   710  		default:
   711  			return c.in.setErrorLocked(c.sendAlert(alertUnexpectedMessage))
   712  		}
   713  
   714  	case recordTypeChangeCipherSpec:
   715  		if len(data) != 1 || data[0] != 1 {
   716  			return c.in.setErrorLocked(c.sendAlert(alertDecodeError))
   717  		}
   718  		// Handshake messages are not allowed to fragment across the CCS.
   719  		if c.hand.Len() > 0 {
   720  			return c.in.setErrorLocked(c.sendAlert(alertUnexpectedMessage))
   721  		}
   722  		// In TLS 1.3, change_cipher_spec records are ignored until the
   723  		// Finished. See RFC 8446, Appendix D.4. Note that according to Section
   724  		// 5, a server can send a ChangeCipherSpec before its ServerHello, when
   725  		// c.vers is still unset. That's not useful though and suspicious if the
   726  		// server then selects a lower protocol version, so don't allow that.
   727  		if c.vers == VersionTLS13 {
   728  			return c.retryReadRecord(expectChangeCipherSpec)
   729  		}
   730  		if !expectChangeCipherSpec {
   731  			return c.in.setErrorLocked(c.sendAlert(alertUnexpectedMessage))
   732  		}
   733  		if err := c.in.changeCipherSpec(); err != nil {
   734  			return c.in.setErrorLocked(c.sendAlert(err.(alert)))
   735  		}
   736  
   737  	case recordTypeApplicationData:
   738  		if !handshakeComplete || expectChangeCipherSpec {
   739  			return c.in.setErrorLocked(c.sendAlert(alertUnexpectedMessage))
   740  		}
   741  		// Some OpenSSL servers send empty records in order to randomize the
   742  		// CBC IV. Ignore a limited number of empty records.
   743  		if len(data) == 0 {
   744  			return c.retryReadRecord(expectChangeCipherSpec)
   745  		}
   746  		// Note that data is owned by c.rawInput, following the Next call above,
   747  		// to avoid copying the plaintext. This is safe because c.rawInput is
   748  		// not read from or written to until c.input is drained.
   749  		c.input.Reset(data)
   750  
   751  	case recordTypeHandshake:
   752  		if len(data) == 0 || expectChangeCipherSpec {
   753  			return c.in.setErrorLocked(c.sendAlert(alertUnexpectedMessage))
   754  		}
   755  		c.hand.Write(data)
   756  	}
   757  
   758  	return nil
   759  }
   760  
   761  // retryReadRecord recurses into readRecordOrCCS to drop a non-advancing record, like
   762  // a warning alert, empty application_data, or a change_cipher_spec in TLS 1.3.
   763  func (c *Conn) retryReadRecord(expectChangeCipherSpec bool) error {
   764  	c.retryCount++
   765  	if c.retryCount > maxUselessRecords {
   766  		c.sendAlert(alertUnexpectedMessage)
   767  		return c.in.setErrorLocked(errors.New("tls: too many ignored records"))
   768  	}
   769  	return c.readRecordOrCCS(expectChangeCipherSpec)
   770  }
   771  
   772  // atLeastReader reads from R, stopping with EOF once at least N bytes have been
   773  // read. It is different from an io.LimitedReader in that it doesn't cut short
   774  // the last Read call, and in that it considers an early EOF an error.
   775  type atLeastReader struct {
   776  	R io.Reader
   777  	N int64
   778  }
   779  
   780  func (r *atLeastReader) Read(p []byte) (int, error) {
   781  	if r.N <= 0 {
   782  		return 0, io.EOF
   783  	}
   784  	n, err := r.R.Read(p)
   785  	r.N -= int64(n) // won't underflow unless len(p) >= n > 9223372036854775809
   786  	if r.N > 0 && err == io.EOF {
   787  		return n, io.ErrUnexpectedEOF
   788  	}
   789  	if r.N <= 0 && err == nil {
   790  		return n, io.EOF
   791  	}
   792  	return n, err
   793  }
   794  
   795  // readFromUntil reads from r into c.rawInput until c.rawInput contains
   796  // at least n bytes or else returns an error.
   797  func (c *Conn) readFromUntil(r io.Reader, n int) error {
   798  	if c.rawInput.Len() >= n {
   799  		return nil
   800  	}
   801  	needs := n - c.rawInput.Len()
   802  	// There might be extra input waiting on the wire. Make a best effort
   803  	// attempt to fetch it so that it can be used in (*Conn).Read to
   804  	// "predict" closeNotify alerts.
   805  	c.rawInput.Grow(needs + bytes.MinRead)
   806  	_, err := c.rawInput.ReadFrom(&atLeastReader{r, int64(needs)})
   807  	return err
   808  }
   809  
   810  // sendAlert sends a TLS alert message.
   811  func (c *Conn) sendAlertLocked(err alert) error {
   812  	switch err {
   813  	case alertNoRenegotiation, alertCloseNotify:
   814  		c.tmp[0] = alertLevelWarning
   815  	default:
   816  		c.tmp[0] = alertLevelError
   817  	}
   818  	c.tmp[1] = byte(err)
   819  
   820  	_, writeErr := c.writeRecordLocked(recordTypeAlert, c.tmp[0:2])
   821  	if err == alertCloseNotify {
   822  		// closeNotify is a special case in that it isn't an error.
   823  		return writeErr
   824  	}
   825  
   826  	return c.out.setErrorLocked(&net.OpError{Op: "local error", Err: err})
   827  }
   828  
   829  // sendAlert sends a TLS alert message.
   830  func (c *Conn) sendAlert(err alert) error {
   831  	c.out.Lock()
   832  	defer c.out.Unlock()
   833  	return c.sendAlertLocked(err)
   834  }
   835  
   836  const (
   837  	// tcpMSSEstimate is a conservative estimate of the TCP maximum segment
   838  	// size (MSS). A constant is used, rather than querying the kernel for
   839  	// the actual MSS, to avoid complexity. The value here is the IPv6
   840  	// minimum MTU (1280 bytes) minus the overhead of an IPv6 header (40
   841  	// bytes) and a TCP header with timestamps (32 bytes).
   842  	tcpMSSEstimate = 1208
   843  
   844  	// recordSizeBoostThreshold is the number of bytes of application data
   845  	// sent after which the TLS record size will be increased to the
   846  	// maximum.
   847  	recordSizeBoostThreshold = 128 * 1024
   848  )
   849  
   850  // maxPayloadSizeForWrite returns the maximum TLS payload size to use for the
   851  // next application data record. There is the following trade-off:
   852  //
   853  //   - For latency-sensitive applications, such as web browsing, each TLS
   854  //     record should fit in one TCP segment.
   855  //   - For throughput-sensitive applications, such as large file transfers,
   856  //     larger TLS records better amortize framing and encryption overheads.
   857  //
   858  // A simple heuristic that works well in practice is to use small records for
   859  // the first 1MB of data, then use larger records for subsequent data, and
   860  // reset back to smaller records after the connection becomes idle. See "High
   861  // Performance Web Networking", Chapter 4, or:
   862  // https://www.igvita.com/2013/10/24/optimizing-tls-record-size-and-buffering-latency/
   863  //
   864  // In the interests of simplicity and determinism, this code does not attempt
   865  // to reset the record size once the connection is idle, however.
   866  func (c *Conn) maxPayloadSizeForWrite(typ recordType) int {
   867  	if c.config.DynamicRecordSizingDisabled || typ != recordTypeApplicationData {
   868  		return maxPlaintext
   869  	}
   870  
   871  	if c.bytesSent >= recordSizeBoostThreshold {
   872  		return maxPlaintext
   873  	}
   874  
   875  	// Subtract TLS overheads to get the maximum payload size.
   876  	payloadBytes := tcpMSSEstimate - recordHeaderLen - c.out.explicitNonceLen()
   877  	if c.out.cipher != nil {
   878  		switch ciph := c.out.cipher.(type) {
   879  		case cipher.Stream:
   880  			payloadBytes -= c.out.mac.Size()
   881  		case cipher.AEAD:
   882  			payloadBytes -= ciph.Overhead()
   883  		case cbcMode:
   884  			blockSize := ciph.BlockSize()
   885  			// The payload must fit in a multiple of blockSize, with
   886  			// room for at least one padding byte.
   887  			payloadBytes = (payloadBytes & ^(blockSize - 1)) - 1
   888  			// The MAC is appended before padding so affects the
   889  			// payload size directly.
   890  			payloadBytes -= c.out.mac.Size()
   891  		default:
   892  			panic("unknown cipher type")
   893  		}
   894  	}
   895  	if c.vers == VersionTLS13 {
   896  		payloadBytes-- // encrypted ContentType
   897  	}
   898  
   899  	// Allow packet growth in arithmetic progression up to max.
   900  	pkt := c.packetsSent
   901  	c.packetsSent++
   902  	if pkt > 1000 {
   903  		return maxPlaintext // avoid overflow in multiply below
   904  	}
   905  
   906  	n := payloadBytes * int(pkt+1)
   907  	if n > maxPlaintext {
   908  		n = maxPlaintext
   909  	}
   910  	return n
   911  }
   912  
   913  func (c *Conn) write(data []byte) (int, error) {
   914  	if c.buffering {
   915  		c.sendBuf = append(c.sendBuf, data...)
   916  		return len(data), nil
   917  	}
   918  
   919  	n, err := c.conn.Write(data)
   920  	c.bytesSent += int64(n)
   921  	return n, err
   922  }
   923  
   924  func (c *Conn) flush() (int, error) {
   925  	if len(c.sendBuf) == 0 {
   926  		return 0, nil
   927  	}
   928  
   929  	n, err := c.conn.Write(c.sendBuf)
   930  	c.bytesSent += int64(n)
   931  	c.sendBuf = nil
   932  	c.buffering = false
   933  	return n, err
   934  }
   935  
   936  // outBufPool pools the record-sized scratch buffers used by writeRecordLocked.
   937  var outBufPool = sync.Pool{
   938  	New: func() any {
   939  		return new([]byte)
   940  	},
   941  }
   942  
   943  // writeRecordLocked writes a TLS record with the given type and payload to the
   944  // connection and updates the record layer state.
   945  func (c *Conn) writeRecordLocked(typ recordType, data []byte) (int, error) {
   946  	outBufPtr := outBufPool.Get().(*[]byte)
   947  	outBuf := *outBufPtr
   948  	defer func() {
   949  		// You might be tempted to simplify this by just passing &outBuf to Put,
   950  		// but that would make the local copy of the outBuf slice header escape
   951  		// to the heap, causing an allocation. Instead, we keep around the
   952  		// pointer to the slice header returned by Get, which is already on the
   953  		// heap, and overwrite and return that.
   954  		*outBufPtr = outBuf
   955  		outBufPool.Put(outBufPtr)
   956  	}()
   957  
   958  	var n int
   959  	for len(data) > 0 {
   960  		m := len(data)
   961  		if maxPayload := c.maxPayloadSizeForWrite(typ); m > maxPayload {
   962  			m = maxPayload
   963  		}
   964  
   965  		_, outBuf = sliceForAppend(outBuf[:0], recordHeaderLen)
   966  		outBuf[0] = byte(typ)
   967  		vers := c.vers
   968  		if vers == 0 {
   969  			// Some TLS servers fail if the record version is
   970  			// greater than TLS 1.0 for the initial ClientHello.
   971  			vers = VersionTLS10
   972  		} else if vers == VersionTLS13 {
   973  			// TLS 1.3 froze the record layer version to 1.2.
   974  			// See RFC 8446, Section 5.1.
   975  			vers = VersionTLS12
   976  		}
   977  		outBuf[1] = byte(vers >> 8)
   978  		outBuf[2] = byte(vers)
   979  		outBuf[3] = byte(m >> 8)
   980  		outBuf[4] = byte(m)
   981  
   982  		var err error
   983  		outBuf, err = c.out.encrypt(outBuf, data[:m], c.config.rand())
   984  		if err != nil {
   985  			return n, err
   986  		}
   987  		if _, err := c.write(outBuf); err != nil {
   988  			return n, err
   989  		}
   990  		n += m
   991  		data = data[m:]
   992  	}
   993  
   994  	if typ == recordTypeChangeCipherSpec && c.vers != VersionTLS13 {
   995  		if err := c.out.changeCipherSpec(); err != nil {
   996  			return n, c.sendAlertLocked(err.(alert))
   997  		}
   998  	}
   999  
  1000  	return n, nil
  1001  }
  1002  
  1003  // writeRecord writes a TLS record with the given type and payload to the
  1004  // connection and updates the record layer state.
  1005  func (c *Conn) writeRecord(typ recordType, data []byte) (int, error) {
  1006  	c.out.Lock()
  1007  	defer c.out.Unlock()
  1008  
  1009  	return c.writeRecordLocked(typ, data)
  1010  }
  1011  
  1012  // readHandshake reads the next handshake message from
  1013  // the record layer.
  1014  func (c *Conn) readHandshake() (any, error) {
  1015  	for c.hand.Len() < 4 {
  1016  		if err := c.readRecord(); err != nil {
  1017  			return nil, err
  1018  		}
  1019  	}
  1020  
  1021  	data := c.hand.Bytes()
  1022  	n := int(data[1])<<16 | int(data[2])<<8 | int(data[3])
  1023  	if n > maxHandshake {
  1024  		c.sendAlertLocked(alertInternalError)
  1025  		return nil, c.in.setErrorLocked(fmt.Errorf("tls: handshake message of length %d bytes exceeds maximum of %d bytes", n, maxHandshake))
  1026  	}
  1027  	for c.hand.Len() < 4+n {
  1028  		if err := c.readRecord(); err != nil {
  1029  			return nil, err
  1030  		}
  1031  	}
  1032  	data = c.hand.Next(4 + n)
  1033  	var m handshakeMessage
  1034  	switch data[0] {
  1035  	case typeHelloRequest:
  1036  		m = new(helloRequestMsg)
  1037  	case typeClientHello:
  1038  		m = new(clientHelloMsg)
  1039  	case typeServerHello:
  1040  		m = new(serverHelloMsg)
  1041  	case typeNewSessionTicket:
  1042  		if c.vers == VersionTLS13 {
  1043  			m = new(newSessionTicketMsgTLS13)
  1044  		} else {
  1045  			m = new(newSessionTicketMsg)
  1046  		}
  1047  	case typeCertificate:
  1048  		if c.vers == VersionTLS13 {
  1049  			m = new(certificateMsgTLS13)
  1050  		} else {
  1051  			m = new(certificateMsg)
  1052  		}
  1053  	case typeCertificateRequest:
  1054  		if c.vers == VersionTLS13 {
  1055  			m = new(certificateRequestMsgTLS13)
  1056  		} else {
  1057  			m = &certificateRequestMsg{
  1058  				hasSignatureAlgorithm: c.vers >= VersionTLS12,
  1059  			}
  1060  		}
  1061  	case typeCertificateStatus:
  1062  		m = new(certificateStatusMsg)
  1063  	case typeServerKeyExchange:
  1064  		m = new(serverKeyExchangeMsg)
  1065  	case typeServerHelloDone:
  1066  		m = new(serverHelloDoneMsg)
  1067  	case typeClientKeyExchange:
  1068  		m = new(clientKeyExchangeMsg)
  1069  	case typeCertificateVerify:
  1070  		m = &certificateVerifyMsg{
  1071  			hasSignatureAlgorithm: c.vers >= VersionTLS12,
  1072  		}
  1073  	case typeFinished:
  1074  		m = new(finishedMsg)
  1075  	case typeEncryptedExtensions:
  1076  		m = new(encryptedExtensionsMsg)
  1077  	case typeEndOfEarlyData:
  1078  		m = new(endOfEarlyDataMsg)
  1079  	case typeKeyUpdate:
  1080  		m = new(keyUpdateMsg)
  1081  	default:
  1082  		return nil, c.in.setErrorLocked(c.sendAlert(alertUnexpectedMessage))
  1083  	}
  1084  
  1085  	// The handshake message unmarshalers
  1086  	// expect to be able to keep references to data,
  1087  	// so pass in a fresh copy that won't be overwritten.
  1088  	data = append([]byte(nil), data...)
  1089  
  1090  	if !m.unmarshal(data) {
  1091  		return nil, c.in.setErrorLocked(c.sendAlert(alertUnexpectedMessage))
  1092  	}
  1093  	return m, nil
  1094  }
  1095  
  1096  var (
  1097  	errShutdown = errors.New("tls: protocol is shutdown")
  1098  )
  1099  
  1100  // Write writes data to the connection.
  1101  //
  1102  // As Write calls Handshake, in order to prevent indefinite blocking a deadline
  1103  // must be set for both Read and Write before Write is called when the handshake
  1104  // has not yet completed. See SetDeadline, SetReadDeadline, and
  1105  // SetWriteDeadline.
  1106  func (c *Conn) Write(b []byte) (int, error) {
  1107  	// interlock with Close below
  1108  	for {
  1109  		x := atomic.LoadInt32(&c.activeCall)
  1110  		if x&1 != 0 {
  1111  			return 0, net.ErrClosed
  1112  		}
  1113  		if atomic.CompareAndSwapInt32(&c.activeCall, x, x+2) {
  1114  			break
  1115  		}
  1116  	}
  1117  	defer atomic.AddInt32(&c.activeCall, -2)
  1118  
  1119  	if err := c.Handshake(); err != nil {
  1120  		return 0, err
  1121  	}
  1122  
  1123  	c.out.Lock()
  1124  	defer c.out.Unlock()
  1125  
  1126  	if err := c.out.err; err != nil {
  1127  		return 0, err
  1128  	}
  1129  
  1130  	if !c.handshakeComplete() {
  1131  		return 0, alertInternalError
  1132  	}
  1133  
  1134  	if c.closeNotifySent {
  1135  		return 0, errShutdown
  1136  	}
  1137  
  1138  	// TLS 1.0 is susceptible to a chosen-plaintext
  1139  	// attack when using block mode ciphers due to predictable IVs.
  1140  	// This can be prevented by splitting each Application Data
  1141  	// record into two records, effectively randomizing the IV.
  1142  	//
  1143  	// https://www.openssl.org/~bodo/tls-cbc.txt
  1144  	// https://bugzilla.mozilla.org/show_bug.cgi?id=665814
  1145  	// https://www.imperialviolet.org/2012/01/15/beastfollowup.html
  1146  
  1147  	var m int
  1148  	if len(b) > 1 && c.vers == VersionTLS10 {
  1149  		if _, ok := c.out.cipher.(cipher.BlockMode); ok {
  1150  			n, err := c.writeRecordLocked(recordTypeApplicationData, b[:1])
  1151  			if err != nil {
  1152  				return n, c.out.setErrorLocked(err)
  1153  			}
  1154  			m, b = 1, b[1:]
  1155  		}
  1156  	}
  1157  
  1158  	n, err := c.writeRecordLocked(recordTypeApplicationData, b)
  1159  	return n + m, c.out.setErrorLocked(err)
  1160  }
  1161  
  1162  // handleRenegotiation processes a HelloRequest handshake message.
  1163  func (c *Conn) handleRenegotiation() error {
  1164  	if c.vers == VersionTLS13 {
  1165  		return errors.New("tls: internal error: unexpected renegotiation")
  1166  	}
  1167  
  1168  	msg, err := c.readHandshake()
  1169  	if err != nil {
  1170  		return err
  1171  	}
  1172  
  1173  	helloReq, ok := msg.(*helloRequestMsg)
  1174  	if !ok {
  1175  		c.sendAlert(alertUnexpectedMessage)
  1176  		return unexpectedMessageError(helloReq, msg)
  1177  	}
  1178  
  1179  	if !c.isClient {
  1180  		return c.sendAlert(alertNoRenegotiation)
  1181  	}
  1182  
  1183  	switch c.config.Renegotiation {
  1184  	case RenegotiateNever:
  1185  		return c.sendAlert(alertNoRenegotiation)
  1186  	case RenegotiateOnceAsClient:
  1187  		if c.handshakes > 1 {
  1188  			return c.sendAlert(alertNoRenegotiation)
  1189  		}
  1190  	case RenegotiateFreelyAsClient:
  1191  		// Ok.
  1192  	default:
  1193  		c.sendAlert(alertInternalError)
  1194  		return errors.New("tls: unknown Renegotiation value")
  1195  	}
  1196  
  1197  	c.handshakeMutex.Lock()
  1198  	defer c.handshakeMutex.Unlock()
  1199  
  1200  	atomic.StoreUint32(&c.handshakeStatus, 0)
  1201  	if c.handshakeErr = c.clientHandshake(context.Background()); c.handshakeErr == nil {
  1202  		c.handshakes++
  1203  	}
  1204  	return c.handshakeErr
  1205  }
  1206  
  1207  // handlePostHandshakeMessage processes a handshake message arrived after the
  1208  // handshake is complete. Up to TLS 1.2, it indicates the start of a renegotiation.
  1209  func (c *Conn) handlePostHandshakeMessage() error {
  1210  	if c.vers != VersionTLS13 {
  1211  		return c.handleRenegotiation()
  1212  	}
  1213  
  1214  	msg, err := c.readHandshake()
  1215  	if err != nil {
  1216  		return err
  1217  	}
  1218  
  1219  	c.retryCount++
  1220  	if c.retryCount > maxUselessRecords {
  1221  		c.sendAlert(alertUnexpectedMessage)
  1222  		return c.in.setErrorLocked(errors.New("tls: too many non-advancing records"))
  1223  	}
  1224  
  1225  	switch msg := msg.(type) {
  1226  	case *newSessionTicketMsgTLS13:
  1227  		return c.handleNewSessionTicket(msg)
  1228  	case *keyUpdateMsg:
  1229  		return c.handleKeyUpdate(msg)
  1230  	default:
  1231  		c.sendAlert(alertUnexpectedMessage)
  1232  		return fmt.Errorf("tls: received unexpected handshake message of type %T", msg)
  1233  	}
  1234  }
  1235  
  1236  func (c *Conn) handleKeyUpdate(keyUpdate *keyUpdateMsg) error {
  1237  	cipherSuite := cipherSuiteTLS13ByID(c.cipherSuite)
  1238  	if cipherSuite == nil {
  1239  		return c.in.setErrorLocked(c.sendAlert(alertInternalError))
  1240  	}
  1241  
  1242  	newSecret := cipherSuite.nextTrafficSecret(c.in.trafficSecret)
  1243  	c.in.setTrafficSecret(cipherSuite, newSecret)
  1244  
  1245  	if keyUpdate.updateRequested {
  1246  		c.out.Lock()
  1247  		defer c.out.Unlock()
  1248  
  1249  		msg := &keyUpdateMsg{}
  1250  		_, err := c.writeRecordLocked(recordTypeHandshake, msg.marshal())
  1251  		if err != nil {
  1252  			// Surface the error at the next write.
  1253  			c.out.setErrorLocked(err)
  1254  			return nil
  1255  		}
  1256  
  1257  		newSecret := cipherSuite.nextTrafficSecret(c.out.trafficSecret)
  1258  		c.out.setTrafficSecret(cipherSuite, newSecret)
  1259  	}
  1260  
  1261  	return nil
  1262  }
  1263  
  1264  // Read reads data from the connection.
  1265  //
  1266  // As Read calls Handshake, in order to prevent indefinite blocking a deadline
  1267  // must be set for both Read and Write before Read is called when the handshake
  1268  // has not yet completed. See SetDeadline, SetReadDeadline, and
  1269  // SetWriteDeadline.
  1270  func (c *Conn) Read(b []byte) (int, error) {
  1271  	if err := c.Handshake(); err != nil {
  1272  		return 0, err
  1273  	}
  1274  	if len(b) == 0 {
  1275  		// Put this after Handshake, in case people were calling
  1276  		// Read(nil) for the side effect of the Handshake.
  1277  		return 0, nil
  1278  	}
  1279  
  1280  	c.in.Lock()
  1281  	defer c.in.Unlock()
  1282  
  1283  	for c.input.Len() == 0 {
  1284  		if err := c.readRecord(); err != nil {
  1285  			return 0, err
  1286  		}
  1287  		for c.hand.Len() > 0 {
  1288  			if err := c.handlePostHandshakeMessage(); err != nil {
  1289  				return 0, err
  1290  			}
  1291  		}
  1292  	}
  1293  
  1294  	n, _ := c.input.Read(b)
  1295  
  1296  	// If a close-notify alert is waiting, read it so that we can return (n,
  1297  	// EOF) instead of (n, nil), to signal to the HTTP response reading
  1298  	// goroutine that the connection is now closed. This eliminates a race
  1299  	// where the HTTP response reading goroutine would otherwise not observe
  1300  	// the EOF until its next read, by which time a client goroutine might
  1301  	// have already tried to reuse the HTTP connection for a new request.
  1302  	// See https://golang.org/cl/76400046 and https://golang.org/issue/3514
  1303  	if n != 0 && c.input.Len() == 0 && c.rawInput.Len() > 0 &&
  1304  		recordType(c.rawInput.Bytes()[0]) == recordTypeAlert {
  1305  		if err := c.readRecord(); err != nil {
  1306  			return n, err // will be io.EOF on closeNotify
  1307  		}
  1308  	}
  1309  
  1310  	return n, nil
  1311  }
  1312  
  1313  // Close closes the connection.
  1314  func (c *Conn) Close() error {
  1315  	// Interlock with Conn.Write above.
  1316  	var x int32
  1317  	for {
  1318  		x = atomic.LoadInt32(&c.activeCall)
  1319  		if x&1 != 0 {
  1320  			return net.ErrClosed
  1321  		}
  1322  		if atomic.CompareAndSwapInt32(&c.activeCall, x, x|1) {
  1323  			break
  1324  		}
  1325  	}
  1326  	if x != 0 {
  1327  		// io.Writer and io.Closer should not be used concurrently.
  1328  		// If Close is called while a Write is currently in-flight,
  1329  		// interpret that as a sign that this Close is really just
  1330  		// being used to break the Write and/or clean up resources and
  1331  		// avoid sending the alertCloseNotify, which may block
  1332  		// waiting on handshakeMutex or the c.out mutex.
  1333  		return c.conn.Close()
  1334  	}
  1335  
  1336  	var alertErr error
  1337  	if c.handshakeComplete() {
  1338  		if err := c.closeNotify(); err != nil {
  1339  			alertErr = fmt.Errorf("tls: failed to send closeNotify alert (but connection was closed anyway): %w", err)
  1340  		}
  1341  	}
  1342  
  1343  	if err := c.conn.Close(); err != nil {
  1344  		return err
  1345  	}
  1346  	return alertErr
  1347  }
  1348  
  1349  var errEarlyCloseWrite = errors.New("tls: CloseWrite called before handshake complete")
  1350  
  1351  // CloseWrite shuts down the writing side of the connection. It should only be
  1352  // called once the handshake has completed and does not call CloseWrite on the
  1353  // underlying connection. Most callers should just use Close.
  1354  func (c *Conn) CloseWrite() error {
  1355  	if !c.handshakeComplete() {
  1356  		return errEarlyCloseWrite
  1357  	}
  1358  
  1359  	return c.closeNotify()
  1360  }
  1361  
  1362  func (c *Conn) closeNotify() error {
  1363  	c.out.Lock()
  1364  	defer c.out.Unlock()
  1365  
  1366  	if !c.closeNotifySent {
  1367  		// Set a Write Deadline to prevent possibly blocking forever.
  1368  		c.SetWriteDeadline(time.Now().Add(time.Second * 5))
  1369  		c.closeNotifyErr = c.sendAlertLocked(alertCloseNotify)
  1370  		c.closeNotifySent = true
  1371  		// Any subsequent writes will fail.
  1372  		c.SetWriteDeadline(time.Now())
  1373  	}
  1374  	return c.closeNotifyErr
  1375  }
  1376  
  1377  // Handshake runs the client or server handshake
  1378  // protocol if it has not yet been run.
  1379  //
  1380  // Most uses of this package need not call Handshake explicitly: the
  1381  // first Read or Write will call it automatically.
  1382  //
  1383  // For control over canceling or setting a timeout on a handshake, use
  1384  // HandshakeContext or the Dialer's DialContext method instead.
  1385  func (c *Conn) Handshake() error {
  1386  	return c.HandshakeContext(context.Background())
  1387  }
  1388  
  1389  // HandshakeContext runs the client or server handshake
  1390  // protocol if it has not yet been run.
  1391  //
  1392  // The provided Context must be non-nil. If the context is canceled before
  1393  // the handshake is complete, the handshake is interrupted and an error is returned.
  1394  // Once the handshake has completed, cancellation of the context will not affect the
  1395  // connection.
  1396  //
  1397  // Most uses of this package need not call HandshakeContext explicitly: the
  1398  // first Read or Write will call it automatically.
  1399  func (c *Conn) HandshakeContext(ctx context.Context) error {
  1400  	// Delegate to unexported method for named return
  1401  	// without confusing documented signature.
  1402  	return c.handshakeContext(ctx)
  1403  }
  1404  
  1405  func (c *Conn) handshakeContext(ctx context.Context) (ret error) {
  1406  	handshakeCtx, cancel := context.WithCancel(ctx)
  1407  	// Note: defer this before starting the "interrupter" goroutine
  1408  	// so that we can tell the difference between the input being canceled and
  1409  	// this cancellation. In the former case, we need to close the connection.
  1410  	defer cancel()
  1411  
  1412  	// Start the "interrupter" goroutine, if this context might be canceled.
  1413  	// (The background context cannot).
  1414  	//
  1415  	// The interrupter goroutine waits for the input context to be done and
  1416  	// closes the connection if this happens before the function returns.
  1417  	if ctx.Done() != nil {
  1418  		done := make(chan struct{})
  1419  		interruptRes := make(chan error, 1)
  1420  		defer func() {
  1421  			close(done)
  1422  			if ctxErr := <-interruptRes; ctxErr != nil {
  1423  				// Return context error to user.
  1424  				ret = ctxErr
  1425  			}
  1426  		}()
  1427  		go func() {
  1428  			select {
  1429  			case <-handshakeCtx.Done():
  1430  				// Close the connection, discarding the error
  1431  				_ = c.conn.Close()
  1432  				interruptRes <- handshakeCtx.Err()
  1433  			case <-done:
  1434  				interruptRes <- nil
  1435  			}
  1436  		}()
  1437  	}
  1438  
  1439  	c.handshakeMutex.Lock()
  1440  	defer c.handshakeMutex.Unlock()
  1441  
  1442  	if err := c.handshakeErr; err != nil {
  1443  		return err
  1444  	}
  1445  	if c.handshakeComplete() {
  1446  		return nil
  1447  	}
  1448  
  1449  	c.in.Lock()
  1450  	defer c.in.Unlock()
  1451  
  1452  	c.handshakeErr = c.handshakeFn(handshakeCtx)
  1453  	if c.handshakeErr == nil {
  1454  		c.handshakes++
  1455  	} else {
  1456  		// If an error occurred during the handshake try to flush the
  1457  		// alert that might be left in the buffer.
  1458  		c.flush()
  1459  	}
  1460  
  1461  	if c.handshakeErr == nil && !c.handshakeComplete() {
  1462  		c.handshakeErr = errors.New("tls: internal error: handshake should have had a result")
  1463  	}
  1464  
  1465  	return c.handshakeErr
  1466  }
  1467  
  1468  // ConnectionState returns basic TLS details about the connection.
  1469  func (c *Conn) ConnectionState() ConnectionState {
  1470  	c.handshakeMutex.Lock()
  1471  	defer c.handshakeMutex.Unlock()
  1472  	return c.connectionStateLocked()
  1473  }
  1474  
  1475  func (c *Conn) connectionStateLocked() ConnectionState {
  1476  	var state ConnectionState
  1477  	state.HandshakeComplete = c.handshakeComplete()
  1478  	state.Version = c.vers
  1479  	state.NegotiatedProtocol = c.clientProtocol
  1480  	state.DidResume = c.didResume
  1481  	state.NegotiatedProtocolIsMutual = true
  1482  	state.ServerName = c.serverName
  1483  	state.CipherSuite = c.cipherSuite
  1484  	state.PeerCertificates = c.peerCertificates
  1485  	state.VerifiedChains = c.verifiedChains
  1486  	state.SignedCertificateTimestamps = c.scts
  1487  	state.OCSPResponse = c.ocspResponse
  1488  	if !c.didResume && c.vers != VersionTLS13 {
  1489  		if c.clientFinishedIsFirst {
  1490  			state.TLSUnique = c.clientFinished[:]
  1491  		} else {
  1492  			state.TLSUnique = c.serverFinished[:]
  1493  		}
  1494  	}
  1495  	if c.config.Renegotiation != RenegotiateNever {
  1496  		state.ekm = noExportedKeyingMaterial
  1497  	} else {
  1498  		state.ekm = c.ekm
  1499  	}
  1500  	return state
  1501  }
  1502  
  1503  // OCSPResponse returns the stapled OCSP response from the TLS server, if
  1504  // any. (Only valid for client connections.)
  1505  func (c *Conn) OCSPResponse() []byte {
  1506  	c.handshakeMutex.Lock()
  1507  	defer c.handshakeMutex.Unlock()
  1508  
  1509  	return c.ocspResponse
  1510  }
  1511  
  1512  // VerifyHostname checks that the peer certificate chain is valid for
  1513  // connecting to host. If so, it returns nil; if not, it returns an error
  1514  // describing the problem.
  1515  func (c *Conn) VerifyHostname(host string) error {
  1516  	c.handshakeMutex.Lock()
  1517  	defer c.handshakeMutex.Unlock()
  1518  	if !c.isClient {
  1519  		return errors.New("tls: VerifyHostname called on TLS server connection")
  1520  	}
  1521  	if !c.handshakeComplete() {
  1522  		return errors.New("tls: handshake has not yet been performed")
  1523  	}
  1524  	if len(c.verifiedChains) == 0 {
  1525  		return errors.New("tls: handshake did not verify certificate chain")
  1526  	}
  1527  	return c.peerCertificates[0].VerifyHostname(host)
  1528  }
  1529  
  1530  func (c *Conn) handshakeComplete() bool {
  1531  	return atomic.LoadUint32(&c.handshakeStatus) == 1
  1532  }
  1533  

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