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ssh: cleanup cipher creation logic 

Change-Id: I0e6ac0a381ffa53650304f0bea2ba79c3cf1d8c2
Reviewed-on: https://go-review.googlesource.com/87196
Run-TryBot: Han-Wen Nienhuys <hanwen@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
This commit is contained in:
Han-Wen Nienhuys 2018-01-10 17:35:17 +01:00
Родитель 1c1f1399d0
Коммит 39efaea5da
2 изменённых файлов: 62 добавлений и 91 удалений
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106
ssh/cipher.go
Просмотреть файл

@ -56,78 +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
}
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)
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
}
stream.XORKeyStream(streamDump[:dumpThisTime], streamDump[:dumpThisTime])
remainingToDump -= dumpThisTime
}
return stream, nil
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]*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)},
// AEAD ciphers are special cased. If we add any more non-stream
// ciphers, we should create a cleaner way to do this.
gcmCipherID: {16, 12, 0, nil},
chacha20Poly1305ID: {64, 0, 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
@ -307,7 +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
@ -425,7 +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),
@ -439,13 +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
}
@ -453,13 +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
}
@ -646,9 +646,9 @@ type chacha20Poly1305Cipher struct {
buf []byte
}
func newChaCha20Cipher(key []byte) (packetCipher, error) {
func newChaCha20Cipher(key, unusedIV, unusedMACKey []byte, unusedAlgs directionAlgorithms) (packetCipher, error) {
if len(key) != 64 {
panic("key length")
panic(len(key))
}
c := &chacha20Poly1305Cipher{

47
ssh/transport.go
Просмотреть файл

@ -233,51 +233,22 @@ var (
clientKeys = direction{[]byte{'A'}, []byte{'C'}, []byte{'E'}}
)
// generateKeys generates key material for IV, MAC and encryption.
func generateKeys(d direction, algs directionAlgorithms, kex *kexResult) (iv, key, macKey []byte) {
cipherMode := cipherModes[algs.Cipher]
macMode := macModes[algs.MAC]
iv = make([]byte, cipherMode.ivSize)
key = make([]byte, cipherMode.keySize)
macKey = make([]byte, macMode.keySize)
generateKeyMaterial(iv, d.ivTag, kex)
generateKeyMaterial(key, d.keyTag, kex)
generateKeyMaterial(macKey, d.macKeyTag, kex)
return
}
// setupKeys sets the cipher and MAC keys from kex.K, kex.H and sessionId, as
// described in RFC 4253, section 6.4. direction should either be serverKeys
// (to setup server->client keys) or clientKeys (for client->server keys).
func newPacketCipher(d direction, algs directionAlgorithms, kex *kexResult) (packetCipher, error) {
iv, key, macKey := generateKeys(d, algs, kex)
cipherMode := cipherModes[algs.Cipher]
macMode := macModes[algs.MAC]
switch algs.Cipher {
case chacha20Poly1305ID:
return newChaCha20Cipher(key)
case gcmCipherID:
return newGCMCipher(iv, key)
case aes128cbcID:
return newAESCBCCipher(iv, key, macKey, algs)
case tripledescbcID:
return newTripleDESCBCCipher(iv, key, macKey, algs)
}
iv := make([]byte, cipherMode.ivSize)
key := make([]byte, cipherMode.keySize)
macKey := make([]byte, macMode.keySize)
c := &streamPacketCipher{
mac: macModes[algs.MAC].new(macKey),
etm: macModes[algs.MAC].etm,
}
c.macResult = make([]byte, c.mac.Size())
generateKeyMaterial(iv, d.ivTag, kex)
generateKeyMaterial(key, d.keyTag, kex)
generateKeyMaterial(macKey, d.macKeyTag, kex)
var err error
c.cipher, err = cipherModes[algs.Cipher].createStream(key, iv)
if err != nil {
return nil, err
}
return c, nil
return cipherModes[algs.Cipher].create(key, iv, macKey, algs)
}
// generateKeyMaterial fills out with key material generated from tag, K, H