From 649bf79117e30895108b7782d62daafd07bc5e6e Mon Sep 17 00:00:00 2001 From: Niall Sheridan Date: Sun, 22 May 2016 01:23:33 +0100 Subject: Use govendor --- vendor/golang.org/x/crypto/ssh/cipher.go | 579 +++++++++++++++++++++++++++++++ 1 file changed, 579 insertions(+) create mode 100644 vendor/golang.org/x/crypto/ssh/cipher.go (limited to 'vendor/golang.org/x/crypto/ssh/cipher.go') diff --git a/vendor/golang.org/x/crypto/ssh/cipher.go b/vendor/golang.org/x/crypto/ssh/cipher.go new file mode 100644 index 0000000..34d3917 --- /dev/null +++ b/vendor/golang.org/x/crypto/ssh/cipher.go @@ -0,0 +1,579 @@ +// 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" +) + +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 streamCipherMode struct { + keySize int + ivSize int + skip int + createFunc func(key, iv []byte) (cipher.Stream, error) +} + +func (c *streamCipherMode) createStream(key, iv []byte) (cipher.Stream, error) { + if len(key) < c.keySize { + panic("ssh: key length too small for cipher") + } + if len(iv) < c.ivSize { + panic("ssh: iv too small for cipher") + } + + stream, err := c.createFunc(key[:c.keySize], iv[:c.ivSize]) + if err != nil { + return nil, err + } + + var streamDump []byte + if c.skip > 0 { + streamDump = make([]byte, 512) + } + + for remainingToDump := c.skip; remainingToDump > 0; { + dumpThisTime := remainingToDump + if dumpThisTime > len(streamDump) { + dumpThisTime = len(streamDump) + } + stream.XORKeyStream(streamDump[:dumpThisTime], streamDump[:dumpThisTime]) + remainingToDump -= dumpThisTime + } + + return 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]*streamCipherMode{ + // Ciphers from RFC4344, which introduced many CTR-based ciphers. Algorithms + // are defined in the order specified in the RFC. + "aes128-ctr": {16, aes.BlockSize, 0, newAESCTR}, + "aes192-ctr": {24, aes.BlockSize, 0, newAESCTR}, + "aes256-ctr": {32, aes.BlockSize, 0, newAESCTR}, + + // Ciphers from RFC4345, which introduces security-improved arcfour ciphers. + // They are defined in the order specified in the RFC. + "arcfour128": {16, 0, 1536, newRC4}, + "arcfour256": {32, 0, 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, 0, newRC4}, + + // AES-GCM is not a stream cipher, so it is constructed with a + // special case. If we add any more non-stream ciphers, we + // should invest a cleaner way to do this. + gcmCipherID: {16, 12, 0, nil}, + + // 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, 0, nil}, + + // 3des-cbc is insecure and is disabled by default. + tripledescbcID: {24, des.BlockSize, 0, nil}, +} + +// 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 + + // 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 + } + + 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[:]) + 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] + s.cipher.XORKeyStream(data, data) + + if s.mac != nil { + 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") + } + + paddingLength := packetSizeMultiple - (prefixLen+len(packet))%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[:]) + s.mac.Write(s.prefix[:]) + s.mac.Write(packet) + s.mac.Write(padding) + } + + s.cipher.XORKeyStream(s.prefix[:], s.prefix[:]) + s.cipher.XORKeyStream(packet, packet) + s.cipher.XORKeyStream(padding, 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(iv, key, macKey []byte) (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 >= 20 { + 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, iv, key, 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(iv, key, macKey []byte, algs directionAlgorithms) (packetCipher, error) { + c, err := aes.NewCipher(key) + if err != nil { + return nil, err + } + + cbc, err := newCBCCipher(c, iv, key, macKey, algs) + if err != nil { + return nil, err + } + + return cbc, nil +} + +func newTripleDESCBCCipher(iv, key, macKey []byte, algs directionAlgorithms) (packetCipher, error) { + c, err := des.NewTripleDESCipher(key) + if err != nil { + return nil, err + } + + cbc, err := newCBCCipher(c, iv, key, 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] + } + + if n, err := io.ReadFull(r, c.packetData[firstBlockLength:]); err != nil { + return nil, err + } else { + 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 +} -- cgit v1.2.3