1 files changed, 88 insertions, 0 deletions
diff --git a/libgo/go/exp/ssh/cipher.go b/libgo/go/exp/ssh/cipher.go
new file mode 100644
index 00000000000..de4926d7b81
--- /dev/null
+++ b/libgo/go/exp/ssh/cipher.go
@@ -0,0 +1,88 @@
+// 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/rc4"
+)
+
+// streamDump is used to dump the initial keystream for stream ciphers. It is a
+// a write-only buffer, and not intended for reading so do not require a mutex.
+var streamDump [512]byte
+
+// 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
+	skip     int
+	createFn func(key, iv []byte) (cipher.Stream, error)
+}
+
+func (c *cipherMode) createCipher(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.createFn(key[:c.keySize], iv[:c.ivSize])
+	if err != nil {
+		return nil, err
+	}
+
+	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
+}
+
+// Specifies a default set of ciphers and a preference order. This is based on
+// OpenSSH's default client preference order, minus algorithms that are not
+// implemented.
+var DefaultCipherOrder = []string{
+	"aes128-ctr", "aes192-ctr", "aes256-ctr",
+	"arcfour256", "arcfour128",
+}
+
+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": &cipherMode{16, aes.BlockSize, 0, newAESCTR},
+	"aes192-ctr": &cipherMode{24, aes.BlockSize, 0, newAESCTR},
+	"aes256-ctr": &cipherMode{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": &cipherMode{16, 0, 1536, newRC4},
+	"arcfour256": &cipherMode{32, 0, 1536, newRC4},
+}