2 files changed, 242 insertions, 0 deletions
diff --git a/src/crypto/rc4/rc4.go b/src/crypto/rc4/rc4.go
new file mode 100644
index 0000000..c2df0db
--- /dev/null
+++ b/src/crypto/rc4/rc4.go
@@ -0,0 +1,80 @@
+// Copyright 2009 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 rc4 implements RC4 encryption, as defined in Bruce Schneier's
+// Applied Cryptography.
+//
+// RC4 is cryptographically broken and should not be used for secure
+// applications.
+package rc4
+
+import (
+	"crypto/internal/subtle"
+	"strconv"
+)
+
+// A Cipher is an instance of RC4 using a particular key.
+type Cipher struct {
+	s    [256]uint32
+	i, j uint8
+}
+
+type KeySizeError int
+
+func (k KeySizeError) Error() string {
+	return "crypto/rc4: invalid key size " + strconv.Itoa(int(k))
+}
+
+// NewCipher creates and returns a new Cipher. The key argument should be the
+// RC4 key, at least 1 byte and at most 256 bytes.
+func NewCipher(key []byte) (*Cipher, error) {
+	k := len(key)
+	if k < 1 || k > 256 {
+		return nil, KeySizeError(k)
+	}
+	var c Cipher
+	for i := 0; i < 256; i++ {
+		c.s[i] = uint32(i)
+	}
+	var j uint8 = 0
+	for i := 0; i < 256; i++ {
+		j += uint8(c.s[i]) + key[i%k]
+		c.s[i], c.s[j] = c.s[j], c.s[i]
+	}
+	return &c, nil
+}
+
+// Reset zeros the key data and makes the Cipher unusable.
+//
+// Deprecated: Reset can't guarantee that the key will be entirely removed from
+// the process's memory.
+func (c *Cipher) Reset() {
+	for i := range c.s {
+		c.s[i] = 0
+	}
+	c.i, c.j = 0, 0
+}
+
+// XORKeyStream sets dst to the result of XORing src with the key stream.
+// Dst and src must overlap entirely or not at all.
+func (c *Cipher) XORKeyStream(dst, src []byte) {
+	if len(src) == 0 {
+		return
+	}
+	if subtle.InexactOverlap(dst[:len(src)], src) {
+		panic("crypto/rc4: invalid buffer overlap")
+	}
+	i, j := c.i, c.j
+	_ = dst[len(src)-1]
+	dst = dst[:len(src)] // eliminate bounds check from loop
+	for k, v := range src {
+		i += 1
+		x := c.s[i]
+		j += uint8(x)
+		y := c.s[j]
+		c.s[i], c.s[j] = y, x
+		dst[k] = v ^ uint8(c.s[uint8(x+y)])
+	}
+	c.i, c.j = i, j
+}
diff --git a/src/crypto/rc4/rc4_test.go b/src/crypto/rc4/rc4_test.go
new file mode 100644
index 0000000..e7356aa
--- /dev/null
+++ b/src/crypto/rc4/rc4_test.go
@@ -0,0 +1,162 @@
+// Copyright 2009 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 rc4
+
+import (
+	"bytes"
+	"fmt"
+	"testing"
+)
+
+type rc4Test struct {
+	key, keystream []byte
+}
+
+var golden = []rc4Test{
+	// Test vectors from the original cypherpunk posting of ARC4:
+	//   https://groups.google.com/group/sci.crypt/msg/10a300c9d21afca0?pli=1
+	{
+		[]byte{0x01, 0x23, 0x45, 0x67, 0x89, 0xab, 0xcd, 0xef},
+		[]byte{0x74, 0x94, 0xc2, 0xe7, 0x10, 0x4b, 0x08, 0x79},
+	},
+	{
+		[]byte{0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00},
+		[]byte{0xde, 0x18, 0x89, 0x41, 0xa3, 0x37, 0x5d, 0x3a},
+	},
+	{
+		[]byte{0xef, 0x01, 0x23, 0x45},
+		[]byte{0xd6, 0xa1, 0x41, 0xa7, 0xec, 0x3c, 0x38, 0xdf, 0xbd, 0x61},
+	},
+
+	// Test vectors from the Wikipedia page: https://en.wikipedia.org/wiki/RC4
+	{
+		[]byte{0x4b, 0x65, 0x79},
+		[]byte{0xeb, 0x9f, 0x77, 0x81, 0xb7, 0x34, 0xca, 0x72, 0xa7, 0x19},
+	},
+	{
+		[]byte{0x57, 0x69, 0x6b, 0x69},
+		[]byte{0x60, 0x44, 0xdb, 0x6d, 0x41, 0xb7},
+	},
+	{
+		[]byte{0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00},
+		[]byte{
+			0xde, 0x18, 0x89, 0x41, 0xa3, 0x37, 0x5d, 0x3a,
+			0x8a, 0x06, 0x1e, 0x67, 0x57, 0x6e, 0x92, 0x6d,
+			0xc7, 0x1a, 0x7f, 0xa3, 0xf0, 0xcc, 0xeb, 0x97,
+			0x45, 0x2b, 0x4d, 0x32, 0x27, 0x96, 0x5f, 0x9e,
+			0xa8, 0xcc, 0x75, 0x07, 0x6d, 0x9f, 0xb9, 0xc5,
+			0x41, 0x7a, 0xa5, 0xcb, 0x30, 0xfc, 0x22, 0x19,
+			0x8b, 0x34, 0x98, 0x2d, 0xbb, 0x62, 0x9e, 0xc0,
+			0x4b, 0x4f, 0x8b, 0x05, 0xa0, 0x71, 0x08, 0x50,
+			0x92, 0xa0, 0xc3, 0x58, 0x4a, 0x48, 0xe4, 0xa3,
+			0x0a, 0x39, 0x7b, 0x8a, 0xcd, 0x1d, 0x00, 0x9e,
+			0xc8, 0x7d, 0x68, 0x11, 0xf2, 0x2c, 0xf4, 0x9c,
+			0xa3, 0xe5, 0x93, 0x54, 0xb9, 0x45, 0x15, 0x35,
+			0xa2, 0x18, 0x7a, 0x86, 0x42, 0x6c, 0xca, 0x7d,
+			0x5e, 0x82, 0x3e, 0xba, 0x00, 0x44, 0x12, 0x67,
+			0x12, 0x57, 0xb8, 0xd8, 0x60, 0xae, 0x4c, 0xbd,
+			0x4c, 0x49, 0x06, 0xbb, 0xc5, 0x35, 0xef, 0xe1,
+			0x58, 0x7f, 0x08, 0xdb, 0x33, 0x95, 0x5c, 0xdb,
+			0xcb, 0xad, 0x9b, 0x10, 0xf5, 0x3f, 0xc4, 0xe5,
+			0x2c, 0x59, 0x15, 0x65, 0x51, 0x84, 0x87, 0xfe,
+			0x08, 0x4d, 0x0e, 0x3f, 0x03, 0xde, 0xbc, 0xc9,
+			0xda, 0x1c, 0xe9, 0x0d, 0x08, 0x5c, 0x2d, 0x8a,
+			0x19, 0xd8, 0x37, 0x30, 0x86, 0x16, 0x36, 0x92,
+			0x14, 0x2b, 0xd8, 0xfc, 0x5d, 0x7a, 0x73, 0x49,
+			0x6a, 0x8e, 0x59, 0xee, 0x7e, 0xcf, 0x6b, 0x94,
+			0x06, 0x63, 0xf4, 0xa6, 0xbe, 0xe6, 0x5b, 0xd2,
+			0xc8, 0x5c, 0x46, 0x98, 0x6c, 0x1b, 0xef, 0x34,
+			0x90, 0xd3, 0x7b, 0x38, 0xda, 0x85, 0xd3, 0x2e,
+			0x97, 0x39, 0xcb, 0x23, 0x4a, 0x2b, 0xe7, 0x40,
+		},
+	},
+}
+
+func testEncrypt(t *testing.T, desc string, c *Cipher, src, expect []byte) {
+	dst := make([]byte, len(src))
+	c.XORKeyStream(dst, src)
+	for i, v := range dst {
+		if v != expect[i] {
+			t.Fatalf("%s: mismatch at byte %d:\nhave %x\nwant %x", desc, i, dst, expect)
+		}
+	}
+}
+
+func TestGolden(t *testing.T) {
+	for gi, g := range golden {
+		data := make([]byte, len(g.keystream))
+		for i := range data {
+			data[i] = byte(i)
+		}
+
+		expect := make([]byte, len(g.keystream))
+		for i := range expect {
+			expect[i] = byte(i) ^ g.keystream[i]
+		}
+
+		for size := 1; size <= len(g.keystream); size++ {
+			c, err := NewCipher(g.key)
+			if err != nil {
+				t.Fatalf("#%d: NewCipher: %v", gi, err)
+			}
+
+			off := 0
+			for off < len(g.keystream) {
+				n := len(g.keystream) - off
+				if n > size {
+					n = size
+				}
+				desc := fmt.Sprintf("#%d@[%d:%d]", gi, off, off+n)
+				testEncrypt(t, desc, c, data[off:off+n], expect[off:off+n])
+				off += n
+			}
+		}
+	}
+}
+
+func TestBlock(t *testing.T) {
+	c1a, _ := NewCipher(golden[0].key)
+	c1b, _ := NewCipher(golden[1].key)
+	data1 := make([]byte, 1<<20)
+	for i := range data1 {
+		c1a.XORKeyStream(data1[i:i+1], data1[i:i+1])
+		c1b.XORKeyStream(data1[i:i+1], data1[i:i+1])
+	}
+
+	c2a, _ := NewCipher(golden[0].key)
+	c2b, _ := NewCipher(golden[1].key)
+	data2 := make([]byte, 1<<20)
+	c2a.XORKeyStream(data2, data2)
+	c2b.XORKeyStream(data2, data2)
+
+	if !bytes.Equal(data1, data2) {
+		t.Fatalf("bad block")
+	}
+}
+
+func benchmark(b *testing.B, size int64) {
+	buf := make([]byte, size)
+	c, err := NewCipher(golden[0].key)
+	if err != nil {
+		panic(err)
+	}
+	b.SetBytes(size)
+
+	for i := 0; i < b.N; i++ {
+		c.XORKeyStream(buf, buf)
+	}
+}
+
+func BenchmarkRC4_128(b *testing.B) {
+	benchmark(b, 128)
+}
+
+func BenchmarkRC4_1K(b *testing.B) {
+	benchmark(b, 1024)
+}
+
+func BenchmarkRC4_8K(b *testing.B) {
+	benchmark(b, 8096)
+}