Added XTEA block cipher package to src/pkg/crypto

This is an adaption of the code from http://en.wikipedia.org/wiki/XTEA. The package also implements the block.Cipher
interface so that it can be used with the various block modes.

R=rsc
https://golang.org/cl/157152

src/pkg/Makefile

@@ -36,6 +36,7 @@ DIRS=\
 	crypto/subtle\
 	crypto/tls\
 	crypto/x509\
+	crypto/xtea\
 	debug/dwarf\
 	debug/macho\
 	debug/elf\

src/pkg/crypto/xtea/Makefile

+# 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.
+
+include ../../../Make.$(GOARCH)
+
+TARG=crypto/xtea
+GOFILES=\
+	cipher.go\
+	block.go\
+
+include ../../../Make.pkg

src/pkg/crypto/xtea/block.go

+// 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.
+
+/*
+	Implementation adapted from Needham and Wheeler's paper:
+	http://www.cix.co.uk/~klockstone/xtea.pdf
+
+	A precalculated look up table is used during encryption/decryption for values that are based purely on the key.
+*/
+
+package xtea
+
+// XTEA is based on 64 rounds.
+const numRounds = 64
+
+// blockToUint32 reads an 8 byte slice into two uint32s.
+// The block is treated as big endian.
+func blockToUint32(src []byte) (uint32, uint32) {
+	r0 := uint32(src[0])<<24 | uint32(src[1])<<16 | uint32(src[2])<<8 | uint32(src[3]);
+	r1 := uint32(src[4])<<24 | uint32(src[5])<<16 | uint32(src[6])<<8 | uint32(src[7]);
+	return r0, r1;
+}
+
+// uint32ToBlock writes two unint32s into an 8 byte data block.
+// Values are written as big endian.
+func uint32ToBlock(v0, v1 uint32, dst []byte) {
+	dst[0] = byte(v0 >> 24);
+	dst[1] = byte(v0 >> 16);
+	dst[2] = byte(v0 >> 8);
+	dst[3] = byte(v0);
+	dst[4] = byte(v1 >> 24);
+	dst[5] = byte(v1 >> 16);
+	dst[6] = byte(v1 >> 8);
+	dst[7] = byte(v1 >> 0);
+}
+
+// encryptBlock encrypts a single 8 byte block using XTEA.
+func encryptBlock(c *Cipher, src, dst []byte) {
+	v0, v1 := blockToUint32(src);
+
+	// Two rounds of XTEA applied per loop
+	for i := 0; i < numRounds; {
+		v0 += ((v1<<4 ^ v1>>5) + v1) ^ c.table[i];
+		i++;
+		v1 += ((v0<<4 ^ v0>>5) + v0) ^ c.table[i];
+		i++;
+	}
+
+	uint32ToBlock(v0, v1, dst);
+}
+
+// decryptBlock decrypt a single 8 byte block using XTEA.
+func decryptBlock(c *Cipher, src, dst []byte) {
+	v0, v1 := blockToUint32(src);
+
+	// Two rounds of XTEA applied per loop
+	for i := numRounds; i > 0; {
+		i--;
+		v1 -= ((v0<<4 ^ v0>>5) + v0) ^ c.table[i];
+		i--;
+		v0 -= ((v1<<4 ^ v1>>5) + v1) ^ c.table[i];
+	}
+
+	uint32ToBlock(v0, v1, dst);
+}

src/pkg/crypto/xtea/cipher.go

+// 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.
+
+// This package implements XTEA encryption, as defined in Needham and
+// Wheeler's 1997 technical report, "Tea extensions."
+package xtea
+
+// For details, see http://www.cix.co.uk/~klockstone/xtea.pdf
+
+import (
+	"os";
+	"strconv";
+)
+
+// The XTEA block size in bytes.
+const BlockSize = 8
+
+// A Cipher is an instance of an XTEA cipher using a particular key.
+// table contains a series of precalculated values that are used each round.
+type Cipher struct {
+	table [64]uint32;
+}
+
+type KeySizeError int
+
+func (k KeySizeError) String() string {
+	return "crypto/xtea: invalid key size " + strconv.Itoa(int(k))
+}
+
+// NewCipher creates and returns a new Cipher.
+// The key argument should be the XTEA key.
+// XTEA only supports 128 bit (16 byte) keys.
+func NewCipher(key []byte) (*Cipher, os.Error) {
+	k := len(key);
+	switch k {
+	default:
+		return nil, KeySizeError(k)
+	case 16:
+		break
+	}
+
+	c := new(Cipher);
+	initCipher(c, key);
+
+	return c, nil;
+}
+
+// BlockSize returns the XTEA block size, 8 bytes.
+// It is necessary to satisfy the Key interface in the
+// package "crypto/modes".
+func (c *Cipher) BlockSize() int	{ return BlockSize }
+
+// Encrypt encrypts the 8 byte buffer src using the key and stores the result in dst.
+// Note that for amounts of data larger than a block,
+// it is not safe to just call Encrypt on successive blocks;
+// instead, use an encryption mode like XTEACBC (see modes.go).
+func (c *Cipher) Encrypt(src, dst []byte)	{ encryptBlock(c, src, dst) }
+
+// Decrypt decrypts the 8 byte buffer src using the key k and stores the result in dst.
+func (c *Cipher) Decrypt(src, dst []byte)	{ decryptBlock(c, src, dst) }
+
+// Reset zeros the table, so that it will no longer appear in the process's memory.
+func (c *Cipher) Reset() {
+	for i := 0; i < len(c.table); i++ {
+		c.table[i] = 0
+	}
+}
+
+// initCipher initializes the cipher context by creating a look up table
+// of precalculated values that are based on the key.
+func initCipher(c *Cipher, key []byte) {
+	// Load the key into four uint32s
+	var k [4]uint32;
+	for i := 0; i < len(k); i++ {
+		j := i << 2;	// Multiply by 4
+		k[i] = uint32(key[j+0])<<24 | uint32(key[j+1])<<16 | uint32(key[j+2])<<8 | uint32(key[j+3]);
+	}
+
+	// Precalculate the table
+	const delta = 0x9E3779B9;
+	var sum uint32 = 0;
+
+	// Two rounds of XTEA applied per loop
+	for i := 0; i < numRounds; {
+		c.table[i] = sum + k[sum&3];
+		i++;
+		sum += delta;
+		c.table[i] = sum + k[(sum>>11)&3];
+		i++;
+	}
+}

src/pkg/crypto/xtea/xtea_test.go

+// 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 xtea
+
+import (
+	"testing";
+)
+
+// A sample test key for when we just want to initialise a cipher
+var testKey = []byte{0x00, 0x11, 0x22, 0x33, 0x44, 0x55, 0x66, 0x77, 0x88, 0x99, 0xAA, 0xBB, 0xCC, 0xDD, 0xEE, 0xFF}
+
+// Test that the block size for XTEA is correct
+func TestBlocksize(t *testing.T) {
+	if BlockSize != 8 {
+		t.Errorf("BlockSize constant - expected 8, got %d", BlockSize);
+		return;
+	}
+
+	c, err := NewCipher(testKey);
+	if err != nil {
+		t.Errorf("NewCipher(%d bytes) = %s", len(testKey), err);
+		return;
+	}
+
+	result := c.BlockSize();
+	if result != 8 {
+		t.Errorf("BlockSize function - expected 8, gotr %d", result);
+		return;
+	}
+}
+
+// A series of test values to confirm that the Cipher.table array was initialised correctly
+var testTable = []uint32{
+	0x00112233, 0x6B1568B8, 0xE28CE030, 0xC5089E2D, 0xC5089E2D, 0x1EFBD3A2, 0xA7845C2A, 0x78EF0917,
+	0x78EF0917, 0x172682D0, 0x5B6AC714, 0x822AC955, 0x3DE68511, 0xDC1DFECA, 0x2062430E, 0x3611343F,
+	0xF1CCEFFB, 0x900469B4, 0xD448ADF8, 0x2E3BE36D, 0xB6C46BF5, 0x994029F2, 0x994029F2, 0xF3335F67,
+	0x6AAAD6DF, 0x4D2694DC, 0x4D2694DC, 0xEB5E0E95, 0x2FA252D9, 0x4551440A, 0x121E10D6, 0xB0558A8F,
+	0xE388BDC3, 0x0A48C004, 0xC6047BC0, 0x643BF579, 0xA88039BD, 0x02736F32, 0x8AFBF7BA, 0x5C66A4A7,
+	0x5C66A4A7, 0xC76AEB2C, 0x3EE262A4, 0x215E20A1, 0x215E20A1, 0x7B515616, 0x03D9DE9E, 0x1988CFCF,
+	0xD5448B8B, 0x737C0544, 0xB7C04988, 0xDE804BC9, 0x9A3C0785, 0x3873813E, 0x7CB7C582, 0xD6AAFAF7,
+	0x4E22726F, 0x309E306C, 0x309E306C, 0x8A9165E1, 0x1319EE69, 0xF595AC66, 0xF595AC66, 0x4F88E1DB,
+}
+
+// Test that the cipher context is initialised correctly
+func TestCipherInit(t *testing.T) {
+	c, err := NewCipher(testKey);
+	if err != nil {
+		t.Errorf("NewCipher(%d bytes) = %s", len(testKey), err);
+		return;
+	}
+
+	for i := 0; i < len(c.table); i++ {
+		if c.table[i] != testTable[i] {
+			t.Errorf("NewCipher() failed to initialise Cipher.table[%d] correctly. Expected %08X, got %08X", i, testTable[i], c.table[i]);
+			break;
+		}
+	}
+}
+
+// Test that invalid key sizes return an error
+func TestInvalidKeySize(t *testing.T) {
+	// Test a long key
+	key := []byte{
+		0x00, 0x11, 0x22, 0x33, 0x44, 0x55, 0x66, 0x77, 0x88, 0x99, 0xAA, 0xBB, 0xCC, 0xDD, 0xEE, 0xFF,
+		0x00, 0x11, 0x22, 0x33, 0x44, 0x55, 0x66, 0x77, 0x88, 0x99, 0xAA, 0xBB, 0xCC, 0xDD, 0xEE, 0xFF,
+	};
+
+	_, err := NewCipher(key);
+	if err == nil {
+		t.Errorf("Invalid key size %d didn't result in an error.", len(key))
+	}
+
+	// Test a short key
+	key = []byte{0x00, 0x11, 0x22, 0x33, 0x44, 0x55, 0x66, 0x77};
+
+	_, err = NewCipher(key);
+	if err == nil {
+		t.Errorf("Invalid key size %d didn't result in an error.", len(key))
+	}
+}
+
+// Test that we can correctly decode some bytes we have encoded
+func TestEncodeDecode(t *testing.T) {
+	original := []byte{0x01, 0x23, 0x45, 0x67, 0x89, 0xAB, 0xCD, 0xEF};
+	input := original;
+	output := make([]byte, BlockSize);
+
+	c, err := NewCipher(testKey);
+	if err != nil {
+		t.Errorf("NewCipher(%d bytes) = %s", len(testKey), err);
+		return;
+	}
+
+	// Encrypt the input block
+	c.Encrypt(input, output);
+
+	// Check that the output does not match the input
+	differs := false;
+	for i := 0; i < len(input); i++ {
+		if output[i] != input[i] {
+			differs = true;
+			break;
+		}
+	}
+	if differs == false {
+		t.Error("Cipher.Encrypt: Failed to encrypt the input block.");
+		return;
+	}
+
+	// Decrypt the block we just encrypted
+	input = output;
+	output = make([]byte, BlockSize);
+	c.Decrypt(input, output);
+
+	// Check that the output from decrypt matches our initial input
+	for i := 0; i < len(input); i++ {
+		if output[i] != original[i] {
+			t.Errorf("Decrypted byte %d differed. Expected %02X, got %02X\n", i, original[i], output[i]);
+			return;
+		}
+	}
+}
+
+// Test Vectors
+type CryptTest struct {
+	key		[]byte;
+	plainText	[]byte;
+	cipherText	[]byte;
+}
+
+var CryptTests = []CryptTest{
+	// These were sourced from http://www.freemedialibrary.com/index.php/XTEA_test_vectors
+	CryptTest{
+		[]byte{0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f},
+		[]byte{0x41, 0x42, 0x43, 0x44, 0x45, 0x46, 0x47, 0x48},
+		[]byte{0x49, 0x7d, 0xf3, 0xd0, 0x72, 0x61, 0x2c, 0xb5},
+	},
+	CryptTest{
+		[]byte{0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f},
+		[]byte{0x41, 0x41, 0x41, 0x41, 0x41, 0x41, 0x41, 0x41},
+		[]byte{0xe7, 0x8f, 0x2d, 0x13, 0x74, 0x43, 0x41, 0xd8},
+	},
+	CryptTest{
+		[]byte{0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f},
+		[]byte{0x5a, 0x5b, 0x6e, 0x27, 0x89, 0x48, 0xd7, 0x7f},
+		[]byte{0x41, 0x41, 0x41, 0x41, 0x41, 0x41, 0x41, 0x41},
+	},
+	CryptTest{
+		[]byte{0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00},
+		[]byte{0x41, 0x42, 0x43, 0x44, 0x45, 0x46, 0x47, 0x48},
+		[]byte{0xa0, 0x39, 0x05, 0x89, 0xf8, 0xb8, 0xef, 0xa5},
+	},
+	CryptTest{
+		[]byte{0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00},
+		[]byte{0x41, 0x41, 0x41, 0x41, 0x41, 0x41, 0x41, 0x41},
+		[]byte{0xed, 0x23, 0x37, 0x5a, 0x82, 0x1a, 0x8c, 0x2d},
+	},
+	CryptTest{
+		[]byte{0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00},
+		[]byte{0x70, 0xe1, 0x22, 0x5d, 0x6e, 0x4e, 0x76, 0x55},
+		[]byte{0x41, 0x41, 0x41, 0x41, 0x41, 0x41, 0x41, 0x41},
+	},
+
+	// These vectors are from http://wiki.secondlife.com/wiki/XTEA_Strong_Encryption_Implementation#Bouncy_Castle_C.23_API
+	CryptTest{
+		[]byte{0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00},
+		[]byte{0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00},
+		[]byte{0xDE, 0xE9, 0xD4, 0xD8, 0xF7, 0x13, 0x1E, 0xD9},
+	},
+	CryptTest{
+		[]byte{0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00},
+		[]byte{0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08},
+		[]byte{0x06, 0x5C, 0x1B, 0x89, 0x75, 0xC6, 0xA8, 0x16},
+	},
+	CryptTest{
+		[]byte{0x01, 0x23, 0x45, 0x67, 0x12, 0x34, 0x56, 0x78, 0x23, 0x45, 0x67, 0x89, 0x34, 0x56, 0x78, 0x9A},
+		[]byte{0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00},
+		[]byte{0x1F, 0xF9, 0xA0, 0x26, 0x1A, 0xC6, 0x42, 0x64},
+	},
+	CryptTest{
+		[]byte{0x01, 0x23, 0x45, 0x67, 0x12, 0x34, 0x56, 0x78, 0x23, 0x45, 0x67, 0x89, 0x34, 0x56, 0x78, 0x9A},
+		[]byte{0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08},
+		[]byte{0x8C, 0x67, 0x15, 0x5B, 0x2E, 0xF9, 0x1E, 0xAD},
+	},
+}
+
+// Test encryption
+func TestCipherEncrypt(t *testing.T) {
+	for i, tt := range CryptTests {
+		c, err := NewCipher(tt.key);
+		if err != nil {
+			t.Errorf("NewCipher(%d bytes), vector %d = %s", len(tt.key), i, err);
+			continue;
+		}
+
+		out := make([]byte, len(tt.plainText));
+		c.Encrypt(tt.plainText, out);
+
+		for j := 0; j < len(out); j++ {
+			if out[j] != tt.cipherText[j] {
+				t.Errorf("Cipher.Encrypt %d: out[%d] = %02X, expected %02X", i, j, out[j], tt.cipherText[j]);
+				break;
+			}
+		}
+	}
+}
+
+// Test decryption
+func TestCipherDecrypt(t *testing.T) {
+	for i, tt := range CryptTests {
+		c, err := NewCipher(tt.key);
+		if err != nil {
+			t.Errorf("NewCipher(%d bytes), vector %d = %s", len(tt.key), i, err);
+			continue;
+		}
+
+		out := make([]byte, len(tt.cipherText));
+		c.Decrypt(tt.cipherText, out);
+
+		for j := 0; j < len(out); j++ {
+			if out[j] != tt.plainText[j] {
+				t.Errorf("Cipher.Decrypt %d: out[%d] = %02X, expected %02X", i, j, out[j], tt.plainText[j]);
+				break;
+			}
+		}
+	}
+}
+
+// Test resetting the cipher context
+func TestReset(t *testing.T) {
+	c, err := NewCipher(testKey);
+	if err != nil {
+		t.Errorf("NewCipher(%d bytes) = %s", len(testKey), err);
+		return;
+	}
+
+	c.Reset();
+	for i := 0; i < len(c.table); i++ {
+		if c.table[i] != 0 {
+			t.Errorf("Cipher.Reset: Failed to clear Cipher.table[%d]. expected 0, got %08X", i, c.table[i]);
+			return;
+		}
+	}
+}