diff options
Diffstat (limited to 'vendor/golang.org/x/crypto/ssh/cipher.go')
| -rw-r--r-- | vendor/golang.org/x/crypto/ssh/cipher.go | 240 |
1 files changed, 191 insertions, 49 deletions
diff --git a/vendor/golang.org/x/crypto/ssh/cipher.go b/vendor/golang.org/x/crypto/ssh/cipher.go index e67c5e0a..30a49fdf 100644 --- a/vendor/golang.org/x/crypto/ssh/cipher.go +++ b/vendor/golang.org/x/crypto/ssh/cipher.go @@ -16,6 +16,9 @@ import ( "hash" "io" "io/ioutil" + + "golang.org/x/crypto/internal/chacha20" + "golang.org/x/crypto/poly1305" ) const ( @@ -53,78 +56,78 @@ 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) +type cipherMode struct { + keySize int + ivSize int + create func(key, iv []byte, macKey []byte, algs directionAlgorithms) (packetCipher, 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 - } +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 c.skip > 0 { - streamDump = make([]byte, 512) - } + var streamDump []byte + if skip > 0 { + streamDump = make([]byte, 512) + } - for remainingToDump := c.skip; remainingToDump > 0; { - dumpThisTime := remainingToDump - if dumpThisTime > len(streamDump) { - dumpThisTime = len(streamDump) + for remainingToDump := skip; remainingToDump > 0; { + dumpThisTime := remainingToDump + if dumpThisTime > len(streamDump) { + dumpThisTime = len(streamDump) + } + stream.XORKeyStream(streamDump[:dumpThisTime], streamDump[:dumpThisTime]) + remainingToDump -= dumpThisTime } - stream.XORKeyStream(streamDump[:dumpThisTime], streamDump[:dumpThisTime]) - remainingToDump -= dumpThisTime - } - return stream, nil + 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]*streamCipherMode{ +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, 0, newAESCTR}, - "aes192-ctr": {24, aes.BlockSize, 0, newAESCTR}, - "aes256-ctr": {32, aes.BlockSize, 0, newAESCTR}, + "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, 1536, newRC4}, - "arcfour256": {32, 0, 1536, newRC4}, + "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, 0, newRC4}, + "arcfour": {16, 0, streamCipherMode(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}, + // 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, 0, nil}, + aes128cbcID: {16, aes.BlockSize, newAESCBCCipher}, - // 3des-cbc is insecure and is disabled by default. - tripledescbcID: {24, des.BlockSize, 0, nil}, + // 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 @@ -304,7 +307,7 @@ type gcmCipher struct { buf []byte } -func newGCMCipher(iv, key []byte) (packetCipher, error) { +func newGCMCipher(key, iv, unusedMacKey []byte, unusedAlgs directionAlgorithms) (packetCipher, error) { c, err := aes.NewCipher(key) if err != nil { return nil, err @@ -422,7 +425,7 @@ type cbcCipher struct { oracleCamouflage uint32 } -func newCBCCipher(c cipher.Block, iv, key, macKey []byte, algs directionAlgorithms) (packetCipher, error) { +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), @@ -436,13 +439,13 @@ func newCBCCipher(c cipher.Block, iv, key, macKey []byte, algs directionAlgorith return cbc, nil } -func newAESCBCCipher(iv, key, macKey []byte, algs directionAlgorithms) (packetCipher, error) { +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, iv, key, macKey, algs) + cbc, err := newCBCCipher(c, key, iv, macKey, algs) if err != nil { return nil, err } @@ -450,13 +453,13 @@ func newAESCBCCipher(iv, key, macKey []byte, algs directionAlgorithms) (packetCi return cbc, nil } -func newTripleDESCBCCipher(iv, key, macKey []byte, algs directionAlgorithms) (packetCipher, error) { +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, iv, key, macKey, algs) + cbc, err := newCBCCipher(c, key, iv, macKey, algs) if err != nil { return nil, err } @@ -627,3 +630,142 @@ func (c *cbcCipher) writePacket(seqNum uint32, w io.Writer, rand io.Reader, pack 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 [32]byte + contentKey [32]byte + 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), + } + + copy(c.contentKey[:], key[:32]) + copy(c.lengthKey[:], key[32:]) + return c, nil +} + +// The Poly1305 key is obtained by encrypting 32 0-bytes. +var chacha20PolyKeyInput [32]byte + +func (c *chacha20Poly1305Cipher) readPacket(seqNum uint32, r io.Reader) ([]byte, error) { + var counter [16]byte + binary.BigEndian.PutUint64(counter[8:], uint64(seqNum)) + + var polyKey [32]byte + chacha20.XORKeyStream(polyKey[:], chacha20PolyKeyInput[:], &counter, &c.contentKey) + + encryptedLength := c.buf[:4] + if _, err := io.ReadFull(r, encryptedLength); err != nil { + return nil, err + } + + var lenBytes [4]byte + chacha20.XORKeyStream(lenBytes[:], encryptedLength, &counter, &c.lengthKey) + + 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") + } + + counter[0] = 1 + + plain := c.buf[4:contentEnd] + chacha20.XORKeyStream(plain, plain, &counter, &c.contentKey) + + 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 { + var counter [16]byte + binary.BigEndian.PutUint64(counter[8:], uint64(seqNum)) + + var polyKey [32]byte + chacha20.XORKeyStream(polyKey[:], chacha20PolyKeyInput[:], &counter, &c.contentKey) + + // 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.XORKeyStream(c.buf, c.buf[:4], &counter, &c.lengthKey) + 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 + } + + counter[0] = 1 + chacha20.XORKeyStream(c.buf[4:], c.buf[4:packetEnd], &counter, &c.contentKey) + + 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 +} |