diff options
Diffstat (limited to 'vendor/golang.org/x/crypto/ssh/cipher.go')
| -rw-r--r-- | vendor/golang.org/x/crypto/ssh/cipher.go | 770 |
1 files changed, 0 insertions, 770 deletions
diff --git a/vendor/golang.org/x/crypto/ssh/cipher.go b/vendor/golang.org/x/crypto/ssh/cipher.go deleted file mode 100644 index 67b0126..0000000 --- a/vendor/golang.org/x/crypto/ssh/cipher.go +++ /dev/null @@ -1,770 +0,0 @@ -// Copyright 2011 The Go Authors. All rights reserved. -// Use of this source code is governed by a BSD-style -// license that can be found in the LICENSE file. - -package ssh - -import ( - "crypto/aes" - "crypto/cipher" - "crypto/des" - "crypto/rc4" - "crypto/subtle" - "encoding/binary" - "errors" - "fmt" - "hash" - "io" - "io/ioutil" - "math/bits" - - "golang.org/x/crypto/internal/chacha20" - "golang.org/x/crypto/poly1305" -) - -const ( - packetSizeMultiple = 16 // TODO(huin) this should be determined by the cipher. - - // RFC 4253 section 6.1 defines a minimum packet size of 32768 that implementations - // MUST be able to process (plus a few more kilobytes for padding and mac). The RFC - // indicates implementations SHOULD be able to handle larger packet sizes, but then - // waffles on about reasonable limits. - // - // OpenSSH caps their maxPacket at 256kB so we choose to do - // the same. maxPacket is also used to ensure that uint32 - // length fields do not overflow, so it should remain well - // below 4G. - maxPacket = 256 * 1024 -) - -// noneCipher implements cipher.Stream and provides no encryption. It is used -// by the transport before the first key-exchange. -type noneCipher struct{} - -func (c noneCipher) XORKeyStream(dst, src []byte) { - copy(dst, src) -} - -func newAESCTR(key, iv []byte) (cipher.Stream, error) { - c, err := aes.NewCipher(key) - if err != nil { - return nil, err - } - return cipher.NewCTR(c, iv), nil -} - -func newRC4(key, iv []byte) (cipher.Stream, error) { - return rc4.NewCipher(key) -} - -type cipherMode struct { - keySize int - ivSize int - create func(key, iv []byte, macKey []byte, algs directionAlgorithms) (packetCipher, error) -} - -func streamCipherMode(skip int, createFunc func(key, iv []byte) (cipher.Stream, error)) func(key, iv []byte, macKey []byte, algs directionAlgorithms) (packetCipher, error) { - return func(key, iv, macKey []byte, algs directionAlgorithms) (packetCipher, error) { - stream, err := createFunc(key, iv) - if err != nil { - return nil, err - } - - var streamDump []byte - if skip > 0 { - streamDump = make([]byte, 512) - } - - for remainingToDump := skip; remainingToDump > 0; { - dumpThisTime := remainingToDump - if dumpThisTime > len(streamDump) { - dumpThisTime = len(streamDump) - } - stream.XORKeyStream(streamDump[:dumpThisTime], streamDump[:dumpThisTime]) - remainingToDump -= dumpThisTime - } - - mac := macModes[algs.MAC].new(macKey) - return &streamPacketCipher{ - mac: mac, - etm: macModes[algs.MAC].etm, - macResult: make([]byte, mac.Size()), - cipher: stream, - }, nil - } -} - -// cipherModes documents properties of supported ciphers. Ciphers not included -// are not supported and will not be negotiated, even if explicitly requested in -// ClientConfig.Crypto.Ciphers. -var cipherModes = map[string]*cipherMode{ - // Ciphers from RFC4344, which introduced many CTR-based ciphers. Algorithms - // are defined in the order specified in the RFC. - "aes128-ctr": {16, aes.BlockSize, streamCipherMode(0, newAESCTR)}, - "aes192-ctr": {24, aes.BlockSize, streamCipherMode(0, newAESCTR)}, - "aes256-ctr": {32, aes.BlockSize, streamCipherMode(0, newAESCTR)}, - - // Ciphers from RFC4345, which introduces security-improved arcfour ciphers. - // They are defined in the order specified in the RFC. - "arcfour128": {16, 0, streamCipherMode(1536, newRC4)}, - "arcfour256": {32, 0, streamCipherMode(1536, newRC4)}, - - // Cipher defined in RFC 4253, which describes SSH Transport Layer Protocol. - // Note that this cipher is not safe, as stated in RFC 4253: "Arcfour (and - // RC4) has problems with weak keys, and should be used with caution." - // RFC4345 introduces improved versions of Arcfour. - "arcfour": {16, 0, streamCipherMode(0, newRC4)}, - - // AEAD ciphers - gcmCipherID: {16, 12, newGCMCipher}, - chacha20Poly1305ID: {64, 0, newChaCha20Cipher}, - - // CBC mode is insecure and so is not included in the default config. - // (See http://www.isg.rhul.ac.uk/~kp/SandPfinal.pdf). If absolutely - // needed, it's possible to specify a custom Config to enable it. - // You should expect that an active attacker can recover plaintext if - // you do. - aes128cbcID: {16, aes.BlockSize, newAESCBCCipher}, - - // 3des-cbc is insecure and is not included in the default - // config. - tripledescbcID: {24, des.BlockSize, newTripleDESCBCCipher}, -} - -// prefixLen is the length of the packet prefix that contains the packet length -// and number of padding bytes. -const prefixLen = 5 - -// streamPacketCipher is a packetCipher using a stream cipher. -type streamPacketCipher struct { - mac hash.Hash - cipher cipher.Stream - etm bool - - // The following members are to avoid per-packet allocations. - prefix [prefixLen]byte - seqNumBytes [4]byte - padding [2 * packetSizeMultiple]byte - packetData []byte - macResult []byte -} - -// readPacket reads and decrypt a single packet from the reader argument. -func (s *streamPacketCipher) readPacket(seqNum uint32, r io.Reader) ([]byte, error) { - if _, err := io.ReadFull(r, s.prefix[:]); err != nil { - return nil, err - } - - var encryptedPaddingLength [1]byte - if s.mac != nil && s.etm { - copy(encryptedPaddingLength[:], s.prefix[4:5]) - s.cipher.XORKeyStream(s.prefix[4:5], s.prefix[4:5]) - } else { - s.cipher.XORKeyStream(s.prefix[:], s.prefix[:]) - } - - length := binary.BigEndian.Uint32(s.prefix[0:4]) - paddingLength := uint32(s.prefix[4]) - - var macSize uint32 - if s.mac != nil { - s.mac.Reset() - binary.BigEndian.PutUint32(s.seqNumBytes[:], seqNum) - s.mac.Write(s.seqNumBytes[:]) - if s.etm { - s.mac.Write(s.prefix[:4]) - s.mac.Write(encryptedPaddingLength[:]) - } else { - s.mac.Write(s.prefix[:]) - } - macSize = uint32(s.mac.Size()) - } - - if length <= paddingLength+1 { - return nil, errors.New("ssh: invalid packet length, packet too small") - } - - if length > maxPacket { - return nil, errors.New("ssh: invalid packet length, packet too large") - } - - // the maxPacket check above ensures that length-1+macSize - // does not overflow. - if uint32(cap(s.packetData)) < length-1+macSize { - s.packetData = make([]byte, length-1+macSize) - } else { - s.packetData = s.packetData[:length-1+macSize] - } - - if _, err := io.ReadFull(r, s.packetData); err != nil { - return nil, err - } - mac := s.packetData[length-1:] - data := s.packetData[:length-1] - - if s.mac != nil && s.etm { - s.mac.Write(data) - } - - s.cipher.XORKeyStream(data, data) - - if s.mac != nil { - if !s.etm { - s.mac.Write(data) - } - s.macResult = s.mac.Sum(s.macResult[:0]) - if subtle.ConstantTimeCompare(s.macResult, mac) != 1 { - return nil, errors.New("ssh: MAC failure") - } - } - - return s.packetData[:length-paddingLength-1], nil -} - -// writePacket encrypts and sends a packet of data to the writer argument -func (s *streamPacketCipher) writePacket(seqNum uint32, w io.Writer, rand io.Reader, packet []byte) error { - if len(packet) > maxPacket { - return errors.New("ssh: packet too large") - } - - aadlen := 0 - if s.mac != nil && s.etm { - // packet length is not encrypted for EtM modes - aadlen = 4 - } - - paddingLength := packetSizeMultiple - (prefixLen+len(packet)-aadlen)%packetSizeMultiple - if paddingLength < 4 { - paddingLength += packetSizeMultiple - } - - length := len(packet) + 1 + paddingLength - binary.BigEndian.PutUint32(s.prefix[:], uint32(length)) - s.prefix[4] = byte(paddingLength) - padding := s.padding[:paddingLength] - if _, err := io.ReadFull(rand, padding); err != nil { - return err - } - - if s.mac != nil { - s.mac.Reset() - binary.BigEndian.PutUint32(s.seqNumBytes[:], seqNum) - s.mac.Write(s.seqNumBytes[:]) - - if s.etm { - // For EtM algorithms, the packet length must stay unencrypted, - // but the following data (padding length) must be encrypted - s.cipher.XORKeyStream(s.prefix[4:5], s.prefix[4:5]) - } - - s.mac.Write(s.prefix[:]) - - if !s.etm { - // For non-EtM algorithms, the algorithm is applied on unencrypted data - s.mac.Write(packet) - s.mac.Write(padding) - } - } - - if !(s.mac != nil && s.etm) { - // For EtM algorithms, the padding length has already been encrypted - // and the packet length must remain unencrypted - s.cipher.XORKeyStream(s.prefix[:], s.prefix[:]) - } - - s.cipher.XORKeyStream(packet, packet) - s.cipher.XORKeyStream(padding, padding) - - if s.mac != nil && s.etm { - // For EtM algorithms, packet and padding must be encrypted - s.mac.Write(packet) - s.mac.Write(padding) - } - - if _, err := w.Write(s.prefix[:]); err != nil { - return err - } - if _, err := w.Write(packet); err != nil { - return err - } - if _, err := w.Write(padding); err != nil { - return err - } - - if s.mac != nil { - s.macResult = s.mac.Sum(s.macResult[:0]) - if _, err := w.Write(s.macResult); err != nil { - return err - } - } - - return nil -} - -type gcmCipher struct { - aead cipher.AEAD - prefix [4]byte - iv []byte - buf []byte -} - -func newGCMCipher(key, iv, unusedMacKey []byte, unusedAlgs directionAlgorithms) (packetCipher, error) { - c, err := aes.NewCipher(key) - if err != nil { - return nil, err - } - - aead, err := cipher.NewGCM(c) - if err != nil { - return nil, err - } - - return &gcmCipher{ - aead: aead, - iv: iv, - }, nil -} - -const gcmTagSize = 16 - -func (c *gcmCipher) writePacket(seqNum uint32, w io.Writer, rand io.Reader, packet []byte) error { - // Pad out to multiple of 16 bytes. This is different from the - // stream cipher because that encrypts the length too. - padding := byte(packetSizeMultiple - (1+len(packet))%packetSizeMultiple) - if padding < 4 { - padding += packetSizeMultiple - } - - length := uint32(len(packet) + int(padding) + 1) - binary.BigEndian.PutUint32(c.prefix[:], length) - if _, err := w.Write(c.prefix[:]); err != nil { - return err - } - - if cap(c.buf) < int(length) { - c.buf = make([]byte, length) - } else { - c.buf = c.buf[:length] - } - - c.buf[0] = padding - copy(c.buf[1:], packet) - if _, err := io.ReadFull(rand, c.buf[1+len(packet):]); err != nil { - return err - } - c.buf = c.aead.Seal(c.buf[:0], c.iv, c.buf, c.prefix[:]) - if _, err := w.Write(c.buf); err != nil { - return err - } - c.incIV() - - return nil -} - -func (c *gcmCipher) incIV() { - for i := 4 + 7; i >= 4; i-- { - c.iv[i]++ - if c.iv[i] != 0 { - break - } - } -} - -func (c *gcmCipher) readPacket(seqNum uint32, r io.Reader) ([]byte, error) { - if _, err := io.ReadFull(r, c.prefix[:]); err != nil { - return nil, err - } - length := binary.BigEndian.Uint32(c.prefix[:]) - if length > maxPacket { - return nil, errors.New("ssh: max packet length exceeded") - } - - if cap(c.buf) < int(length+gcmTagSize) { - c.buf = make([]byte, length+gcmTagSize) - } else { - c.buf = c.buf[:length+gcmTagSize] - } - - if _, err := io.ReadFull(r, c.buf); err != nil { - return nil, err - } - - plain, err := c.aead.Open(c.buf[:0], c.iv, c.buf, c.prefix[:]) - if err != nil { - return nil, err - } - c.incIV() - - padding := plain[0] - if padding < 4 { - // padding is a byte, so it automatically satisfies - // the maximum size, which is 255. - return nil, fmt.Errorf("ssh: illegal padding %d", padding) - } - - if int(padding+1) >= len(plain) { - return nil, fmt.Errorf("ssh: padding %d too large", padding) - } - plain = plain[1 : length-uint32(padding)] - return plain, nil -} - -// cbcCipher implements aes128-cbc cipher defined in RFC 4253 section 6.1 -type cbcCipher struct { - mac hash.Hash - macSize uint32 - decrypter cipher.BlockMode - encrypter cipher.BlockMode - - // The following members are to avoid per-packet allocations. - seqNumBytes [4]byte - packetData []byte - macResult []byte - - // Amount of data we should still read to hide which - // verification error triggered. - oracleCamouflage uint32 -} - -func newCBCCipher(c cipher.Block, key, iv, macKey []byte, algs directionAlgorithms) (packetCipher, error) { - cbc := &cbcCipher{ - mac: macModes[algs.MAC].new(macKey), - decrypter: cipher.NewCBCDecrypter(c, iv), - encrypter: cipher.NewCBCEncrypter(c, iv), - packetData: make([]byte, 1024), - } - if cbc.mac != nil { - cbc.macSize = uint32(cbc.mac.Size()) - } - - return cbc, nil -} - -func newAESCBCCipher(key, iv, macKey []byte, algs directionAlgorithms) (packetCipher, error) { - c, err := aes.NewCipher(key) - if err != nil { - return nil, err - } - - cbc, err := newCBCCipher(c, key, iv, macKey, algs) - if err != nil { - return nil, err - } - - return cbc, nil -} - -func newTripleDESCBCCipher(key, iv, macKey []byte, algs directionAlgorithms) (packetCipher, error) { - c, err := des.NewTripleDESCipher(key) - if err != nil { - return nil, err - } - - cbc, err := newCBCCipher(c, key, iv, macKey, algs) - if err != nil { - return nil, err - } - - return cbc, nil -} - -func maxUInt32(a, b int) uint32 { - if a > b { - return uint32(a) - } - return uint32(b) -} - -const ( - cbcMinPacketSizeMultiple = 8 - cbcMinPacketSize = 16 - cbcMinPaddingSize = 4 -) - -// cbcError represents a verification error that may leak information. -type cbcError string - -func (e cbcError) Error() string { return string(e) } - -func (c *cbcCipher) readPacket(seqNum uint32, r io.Reader) ([]byte, error) { - p, err := c.readPacketLeaky(seqNum, r) - if err != nil { - if _, ok := err.(cbcError); ok { - // Verification error: read a fixed amount of - // data, to make distinguishing between - // failing MAC and failing length check more - // difficult. - io.CopyN(ioutil.Discard, r, int64(c.oracleCamouflage)) - } - } - return p, err -} - -func (c *cbcCipher) readPacketLeaky(seqNum uint32, r io.Reader) ([]byte, error) { - blockSize := c.decrypter.BlockSize() - - // Read the header, which will include some of the subsequent data in the - // case of block ciphers - this is copied back to the payload later. - // How many bytes of payload/padding will be read with this first read. - firstBlockLength := uint32((prefixLen + blockSize - 1) / blockSize * blockSize) - firstBlock := c.packetData[:firstBlockLength] - if _, err := io.ReadFull(r, firstBlock); err != nil { - return nil, err - } - - c.oracleCamouflage = maxPacket + 4 + c.macSize - firstBlockLength - - c.decrypter.CryptBlocks(firstBlock, firstBlock) - length := binary.BigEndian.Uint32(firstBlock[:4]) - if length > maxPacket { - return nil, cbcError("ssh: packet too large") - } - if length+4 < maxUInt32(cbcMinPacketSize, blockSize) { - // The minimum size of a packet is 16 (or the cipher block size, whichever - // is larger) bytes. - return nil, cbcError("ssh: packet too small") - } - // The length of the packet (including the length field but not the MAC) must - // be a multiple of the block size or 8, whichever is larger. - if (length+4)%maxUInt32(cbcMinPacketSizeMultiple, blockSize) != 0 { - return nil, cbcError("ssh: invalid packet length multiple") - } - - paddingLength := uint32(firstBlock[4]) - if paddingLength < cbcMinPaddingSize || length <= paddingLength+1 { - return nil, cbcError("ssh: invalid packet length") - } - - // Positions within the c.packetData buffer: - macStart := 4 + length - paddingStart := macStart - paddingLength - - // Entire packet size, starting before length, ending at end of mac. - entirePacketSize := macStart + c.macSize - - // Ensure c.packetData is large enough for the entire packet data. - if uint32(cap(c.packetData)) < entirePacketSize { - // Still need to upsize and copy, but this should be rare at runtime, only - // on upsizing the packetData buffer. - c.packetData = make([]byte, entirePacketSize) - copy(c.packetData, firstBlock) - } else { - c.packetData = c.packetData[:entirePacketSize] - } - - n, err := io.ReadFull(r, c.packetData[firstBlockLength:]) - if err != nil { - return nil, err - } - c.oracleCamouflage -= uint32(n) - - remainingCrypted := c.packetData[firstBlockLength:macStart] - c.decrypter.CryptBlocks(remainingCrypted, remainingCrypted) - - mac := c.packetData[macStart:] - if c.mac != nil { - c.mac.Reset() - binary.BigEndian.PutUint32(c.seqNumBytes[:], seqNum) - c.mac.Write(c.seqNumBytes[:]) - c.mac.Write(c.packetData[:macStart]) - c.macResult = c.mac.Sum(c.macResult[:0]) - if subtle.ConstantTimeCompare(c.macResult, mac) != 1 { - return nil, cbcError("ssh: MAC failure") - } - } - - return c.packetData[prefixLen:paddingStart], nil -} - -func (c *cbcCipher) writePacket(seqNum uint32, w io.Writer, rand io.Reader, packet []byte) error { - effectiveBlockSize := maxUInt32(cbcMinPacketSizeMultiple, c.encrypter.BlockSize()) - - // Length of encrypted portion of the packet (header, payload, padding). - // Enforce minimum padding and packet size. - encLength := maxUInt32(prefixLen+len(packet)+cbcMinPaddingSize, cbcMinPaddingSize) - // Enforce block size. - encLength = (encLength + effectiveBlockSize - 1) / effectiveBlockSize * effectiveBlockSize - - length := encLength - 4 - paddingLength := int(length) - (1 + len(packet)) - - // Overall buffer contains: header, payload, padding, mac. - // Space for the MAC is reserved in the capacity but not the slice length. - bufferSize := encLength + c.macSize - if uint32(cap(c.packetData)) < bufferSize { - c.packetData = make([]byte, encLength, bufferSize) - } else { - c.packetData = c.packetData[:encLength] - } - - p := c.packetData - - // Packet header. - binary.BigEndian.PutUint32(p, length) - p = p[4:] - p[0] = byte(paddingLength) - - // Payload. - p = p[1:] - copy(p, packet) - - // Padding. - p = p[len(packet):] - if _, err := io.ReadFull(rand, p); err != nil { - return err - } - - if c.mac != nil { - c.mac.Reset() - binary.BigEndian.PutUint32(c.seqNumBytes[:], seqNum) - c.mac.Write(c.seqNumBytes[:]) - c.mac.Write(c.packetData) - // The MAC is now appended into the capacity reserved for it earlier. - c.packetData = c.mac.Sum(c.packetData) - } - - c.encrypter.CryptBlocks(c.packetData[:encLength], c.packetData[:encLength]) - - if _, err := w.Write(c.packetData); err != nil { - return err - } - - return nil -} - -const chacha20Poly1305ID = "chacha20-poly1305@openssh.com" - -// chacha20Poly1305Cipher implements the chacha20-poly1305@openssh.com -// AEAD, which is described here: -// -// https://tools.ietf.org/html/draft-josefsson-ssh-chacha20-poly1305-openssh-00 -// -// the methods here also implement padding, which RFC4253 Section 6 -// also requires of stream ciphers. -type chacha20Poly1305Cipher struct { - lengthKey [8]uint32 - contentKey [8]uint32 - buf []byte -} - -func newChaCha20Cipher(key, unusedIV, unusedMACKey []byte, unusedAlgs directionAlgorithms) (packetCipher, error) { - if len(key) != 64 { - panic(len(key)) - } - - c := &chacha20Poly1305Cipher{ - buf: make([]byte, 256), - } - - for i := range c.contentKey { - c.contentKey[i] = binary.LittleEndian.Uint32(key[i*4 : (i+1)*4]) - } - for i := range c.lengthKey { - c.lengthKey[i] = binary.LittleEndian.Uint32(key[(i+8)*4 : (i+9)*4]) - } - return c, nil -} - -func (c *chacha20Poly1305Cipher) readPacket(seqNum uint32, r io.Reader) ([]byte, error) { - nonce := [3]uint32{0, 0, bits.ReverseBytes32(seqNum)} - s := chacha20.New(c.contentKey, nonce) - var polyKey [32]byte - s.XORKeyStream(polyKey[:], polyKey[:]) - s.Advance() // skip next 32 bytes - - encryptedLength := c.buf[:4] - if _, err := io.ReadFull(r, encryptedLength); err != nil { - return nil, err - } - - var lenBytes [4]byte - chacha20.New(c.lengthKey, nonce).XORKeyStream(lenBytes[:], encryptedLength) - - length := binary.BigEndian.Uint32(lenBytes[:]) - if length > maxPacket { - return nil, errors.New("ssh: invalid packet length, packet too large") - } - - contentEnd := 4 + length - packetEnd := contentEnd + poly1305.TagSize - if uint32(cap(c.buf)) < packetEnd { - c.buf = make([]byte, packetEnd) - copy(c.buf[:], encryptedLength) - } else { - c.buf = c.buf[:packetEnd] - } - - if _, err := io.ReadFull(r, c.buf[4:packetEnd]); err != nil { - return nil, err - } - - var mac [poly1305.TagSize]byte - copy(mac[:], c.buf[contentEnd:packetEnd]) - if !poly1305.Verify(&mac, c.buf[:contentEnd], &polyKey) { - return nil, errors.New("ssh: MAC failure") - } - - plain := c.buf[4:contentEnd] - s.XORKeyStream(plain, plain) - - padding := plain[0] - if padding < 4 { - // padding is a byte, so it automatically satisfies - // the maximum size, which is 255. - return nil, fmt.Errorf("ssh: illegal padding %d", padding) - } - - if int(padding)+1 >= len(plain) { - return nil, fmt.Errorf("ssh: padding %d too large", padding) - } - - plain = plain[1 : len(plain)-int(padding)] - - return plain, nil -} - -func (c *chacha20Poly1305Cipher) writePacket(seqNum uint32, w io.Writer, rand io.Reader, payload []byte) error { - nonce := [3]uint32{0, 0, bits.ReverseBytes32(seqNum)} - s := chacha20.New(c.contentKey, nonce) - var polyKey [32]byte - s.XORKeyStream(polyKey[:], polyKey[:]) - s.Advance() // skip next 32 bytes - - // There is no blocksize, so fall back to multiple of 8 byte - // padding, as described in RFC 4253, Sec 6. - const packetSizeMultiple = 8 - - padding := packetSizeMultiple - (1+len(payload))%packetSizeMultiple - if padding < 4 { - padding += packetSizeMultiple - } - - // size (4 bytes), padding (1), payload, padding, tag. - totalLength := 4 + 1 + len(payload) + padding + poly1305.TagSize - if cap(c.buf) < totalLength { - c.buf = make([]byte, totalLength) - } else { - c.buf = c.buf[:totalLength] - } - - binary.BigEndian.PutUint32(c.buf, uint32(1+len(payload)+padding)) - chacha20.New(c.lengthKey, nonce).XORKeyStream(c.buf, c.buf[:4]) - c.buf[4] = byte(padding) - copy(c.buf[5:], payload) - packetEnd := 5 + len(payload) + padding - if _, err := io.ReadFull(rand, c.buf[5+len(payload):packetEnd]); err != nil { - return err - } - - s.XORKeyStream(c.buf[4:], c.buf[4:packetEnd]) - - var mac [poly1305.TagSize]byte - poly1305.Sum(&mac, c.buf[:packetEnd], &polyKey) - - copy(c.buf[packetEnd:], mac[:]) - - if _, err := w.Write(c.buf); err != nil { - return err - } - return nil -} |