Crypto modes: CBC, CFB, ECB.

Not ready to link into build yet.

Delta says 1272 lines but only 474
if you subtract the test files,
which are mostly data.

R=r
DELTA=1252  (1249 added, 0 deleted, 3 changed)
OCL=29013
CL=29037

9 files changed, 1260 insertions, 3 deletions

diff --git a/src/lib/crypto/block/cbc.go b/src/lib/crypto/block/cbc.go
new file mode 100644
index 000000000..85a746b72
--- /dev/null
+++ b/src/lib/crypto/block/cbc.go
@@ -0,0 +1,75 @@
+// 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.
+
+// Cipher block chaining (CBC) mode.
+
+// CBC provides confidentiality by xoring (chaining) each plaintext block
+// with the previous ciphertext block before applying the block cipher.
+
+// See NIST SP 800-38A, pp 10-11
+
+package block
+
+import (
+	"crypto/block";
+	"io";
+)
+
+type cbcCipher struct {
+	c Cipher;
+	blockSize int;
+	iv []byte;
+	tmp []byte;
+}
+
+func newCBC(c Cipher, iv []byte) *cbcCipher {
+	n := c.BlockSize();
+	x := new(cbcCipher);
+	x.c = c;
+	x.blockSize = n;
+	x.iv = copy(iv);
+	x.tmp = make([]byte, n);
+	return x;
+}
+
+func (x *cbcCipher) BlockSize() int {
+	return x.blockSize;
+}
+
+func (x *cbcCipher) Encrypt(src, dst []byte) {
+	for i := 0; i < x.blockSize; i++ {
+		x.iv[i] ^= src[i];
+	}
+	x.c.Encrypt(x.iv, x.iv);
+	for i := 0; i < x.blockSize; i++ {
+		dst[i] = x.iv[i];
+	}
+}
+
+func (x *cbcCipher) Decrypt(src, dst []byte) {
+	x.c.Decrypt(src, x.tmp);
+	for i := 0; i < x.blockSize; i++ {
+		x.tmp[i] ^= x.iv[i];
+		x.iv[i] = src[i];
+		dst[i] = x.tmp[i];
+	}
+}
+
+// NewCBCDecrypter returns a reader that reads data from r and decrypts it using c
+// in cipher block chaining (CBC) mode with the initialization vector iv.
+// The returned Reader does not buffer or read ahead except
+// as required by the cipher's block size.
+func NewCBCDecrypter(c Cipher, iv []byte, r io.Reader) io.Reader {
+	return NewECBDecrypter(newCBC(c, iv), r);
+}
+
+// NewCBCEncrypter returns a writer that encrypts data using c
+// in cipher block chaining (CBC) mode with the initialization vector iv
+// and writes the encrypted data to w.
+// The returned Writer does no buffering except as required
+// by the cipher's block size, so there is no need for a Flush method.
+func NewCBCEncrypter(c Cipher, iv []byte, w io.Writer) io.Writer {
+	return NewECBEncrypter(newCBC(c, iv), w);
+}
+
diff --git a/src/lib/crypto/block/cbc_aes_test.go b/src/lib/crypto/block/cbc_aes_test.go
new file mode 100644
index 000000000..4681c1c07
--- /dev/null
+++ b/src/lib/crypto/block/cbc_aes_test.go
@@ -0,0 +1,107 @@
+// 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.
+
+// CBC AES test vectors.
+
+// See U.S. National Institute of Standards and Technology (NIST)
+// Special Publication 800-38A, ``Recommendation for Block Cipher
+// Modes of Operation,'' 2001 Edition, pp. 24-29.
+
+package block
+
+// gobuild: $GC ecb_aes_test.go
+
+import (
+	"crypto/aes";
+	"crypto/block";
+	"io";
+	"os";
+	"testing";
+
+	"./ecb_aes_test";
+)
+
+type cbcTest struct {
+	name string;
+	key []byte;
+	iv []byte;
+	in []byte;
+	out []byte;
+}
+
+var cbcAESTests = []cbcTest {
+	// NIST SP 800-38A pp 27-29
+	cbcTest {
+		"CBC-AES128",
+		commonKey128,
+		commonIV,
+		commonInput,
+		[]byte {
+			0x76, 0x49, 0xab, 0xac, 0x81, 0x19, 0xb2, 0x46, 0xce, 0xe9, 0x8e, 0x9b, 0x12, 0xe9, 0x19, 0x7d,
+			0x50, 0x86, 0xcb, 0x9b, 0x50, 0x72, 0x19, 0xee, 0x95, 0xdb, 0x11, 0x3a, 0x91, 0x76, 0x78, 0xb2,
+			0x73, 0xbe, 0xd6, 0xb8, 0xe3, 0xc1, 0x74, 0x3b, 0x71, 0x16, 0xe6, 0x9e, 0x22, 0x22, 0x95, 0x16,
+			0x3f, 0xf1, 0xca, 0xa1, 0x68, 0x1f, 0xac, 0x09, 0x12, 0x0e, 0xca, 0x30, 0x75, 0x86, 0xe1, 0xa7,
+		},
+	},
+	cbcTest {
+		"CBC-AES192",
+		commonKey192,
+		commonIV,
+		commonInput,
+		[]byte {
+			0x4f, 0x02, 0x1d, 0xb2, 0x43, 0xbc, 0x63, 0x3d, 0x71, 0x78, 0x18, 0x3a, 0x9f, 0xa0, 0x71, 0xe8,
+			0xb4, 0xd9, 0xad, 0xa9, 0xad, 0x7d, 0xed, 0xf4, 0xe5, 0xe7, 0x38, 0x76, 0x3f, 0x69, 0x14, 0x5a,
+			0x57, 0x1b, 0x24, 0x20, 0x12, 0xfb, 0x7a, 0xe0, 0x7f, 0xa9, 0xba, 0xac, 0x3d, 0xf1, 0x02, 0xe0,
+			0x08, 0xb0, 0xe2, 0x79, 0x88, 0x59, 0x88, 0x81, 0xd9, 0x20, 0xa9, 0xe6, 0x4f, 0x56, 0x15, 0xcd,
+		},
+	},
+	cbcTest {
+		"CBC-AES256",
+		commonKey256,
+		commonIV,
+		commonInput,
+		[]byte {
+			0xf5, 0x8c, 0x4c, 0x04, 0xd6, 0xe5, 0xf1, 0xba, 0x77, 0x9e, 0xab, 0xfb, 0x5f, 0x7b, 0xfb, 0xd6,
+			0x9c, 0xfc, 0x4e, 0x96, 0x7e, 0xdb, 0x80, 0x8d, 0x67, 0x9f, 0x77, 0x7b, 0xc6, 0x70, 0x2c, 0x7d,
+			0x39, 0xf2, 0x33, 0x69, 0xa9, 0xd9, 0xba, 0xcf, 0xa5, 0x30, 0xe2, 0x63, 0x04, 0x23, 0x14, 0x61,
+			0xb2, 0xeb, 0x05, 0xe2, 0xc3, 0x9b, 0xe9, 0xfc, 0xda, 0x6c, 0x19, 0x07, 0x8c, 0x6a, 0x9d, 0x1b,
+		},
+	},
+}
+
+func TestCBC_AES(t *testing.T) {
+	for i, tt := range cbcAESTests {
+		test := tt.name;
+
+		c, err := aes.NewCipher(tt.key);
+		if err != nil {
+			t.Errorf("%s: NewCipher(%d bytes) = %s", test, len(tt.key), err);
+			continue;
+		}
+
+		var crypt io.ByteBuffer;
+		w := NewCBCEncrypter(c, tt.iv, &crypt);
+		var r io.Reader = io.NewByteReader(tt.in);
+		n, err := io.Copy(r, w);
+		if n != int64(len(tt.in)) || err != nil {
+			t.Errorf("%s: CBCEncrypter io.Copy = %d, %v want %d, nil", test, n, err, len(tt.in));
+		} else if d := crypt.Data(); !same(tt.out, d) {
+			t.Errorf("%s: CBCEncrypter\nhave %x\nwant %x", test, d, tt.out);
+		}
+
+		var plain io.ByteBuffer;
+		r = NewCBCDecrypter(c, tt.iv, io.NewByteReader(tt.out));
+		w = &plain;
+		n, err = io.Copy(r, w);
+		if n != int64(len(tt.out)) || err != nil {
+			t.Errorf("%s: CBCDecrypter io.Copy = %d, %v want %d, nil", test, n, err, len(tt.out));
+		} else if d := plain.Data(); !same(tt.in, d) {
+			t.Errorf("%s: CBCDecrypter\nhave %x\nwant %x", test, d, tt.in);
+		}
+
+		if t.Failed() {
+			break;
+		}
+	}
+}
diff --git a/src/lib/crypto/block/cfb.go b/src/lib/crypto/block/cfb.go
new file mode 100644
index 000000000..827a55ee1
--- /dev/null
+++ b/src/lib/crypto/block/cfb.go
@@ -0,0 +1,100 @@
+// 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.
+
+// Cipher feedback (CFB) mode.
+
+// CFB provides confidentiality by feeding a fraction of
+// the previous ciphertext in as the plaintext for the next
+// block operation.
+
+// See NIST SP 800-38A, pp 11-13
+
+package block
+
+import (
+	"crypto/block";
+	"io";
+)
+
+type cfbCipher struct {
+	c Cipher;
+	blockSize int;	// our block size (s/8)
+	cipherSize int;	// underlying cipher block size
+	iv []byte;
+	tmp []byte;
+}
+
+func newCFB(c Cipher, s int, iv []byte) *cfbCipher {
+	if s == 0 || s % 8 != 0 {
+		panicln("invalid CFB mode", s);
+	}
+	b := c.BlockSize();
+	x := new(cfbCipher);
+	x.c = c;
+	x.blockSize = s/8;
+	x.cipherSize = b;
+	x.iv = copy(iv);
+	x.tmp = make([]byte, b);
+	return x;
+}
+
+func (x *cfbCipher) BlockSize() int {
+	return x.blockSize;
+}
+
+func (x *cfbCipher) Encrypt(src, dst []byte) {
+	// Encrypt old IV and xor prefix with src to make dst.
+	x.c.Encrypt(x.iv, x.tmp);
+	for i := 0; i < x.blockSize; i++ {
+		dst[i] = src[i] ^ x.tmp[i];
+	}
+
+	// Slide unused IV pieces down and insert dst at end.
+	for i := 0; i < x.cipherSize - x.blockSize; i++ {
+		x.iv[i] = x.iv[i + x.blockSize];
+	}
+	off := x.cipherSize - x.blockSize;
+	for i := off; i < x.cipherSize; i++ {
+		x.iv[i] = dst[i - off];
+	}
+}
+
+func (x *cfbCipher) Decrypt(src, dst []byte) {
+	// Encrypt [sic] old IV and xor prefix with src to make dst.
+	x.c.Encrypt(x.iv, x.tmp);
+	for i := 0; i < x.blockSize; i++ {
+		dst[i] = src[i] ^ x.tmp[i];
+	}
+
+	// Slide unused IV pieces down and insert src at top.
+	for i := 0; i < x.cipherSize - x.blockSize; i++ {
+		x.iv[i] = x.iv[i + x.blockSize];
+	}
+	off := x.cipherSize - x.blockSize;
+	for i := off; i < x.cipherSize; i++ {
+		// Reconstruct src = dst ^ x.tmp
+		// in case we overwrote src (src == dst).
+		x.iv[i] = dst[i - off] ^ x.tmp[i - off];
+	}
+}
+
+// NewCFBDecrypter returns a reader that reads data from r and decrypts it using c
+// in s-bit cipher feedback (CFB) mode with the initialization vector iv.
+// The returned Reader does not buffer or read ahead except
+// as required by the cipher's block size.
+// Modes for s not a multiple of 8 are unimplemented.
+func NewCFBDecrypter(c Cipher, s int, iv []byte, r io.Reader) io.Reader {
+	return NewECBDecrypter(newCFB(c, s, iv), r);
+}
+
+// NewCFBEncrypter returns a writer that encrypts data using c
+// in s-bit cipher feedback (CFB) mode with the initialization vector iv
+// and writes the encrypted data to w.
+// The returned Writer does no buffering except as required
+// by the cipher's block size, so there is no need for a Flush method.
+// Modes for s not a multiple of 8 are unimplemented.
+func NewCFBEncrypter(c Cipher, s int, iv []byte, w io.Writer) io.Writer {
+	return NewECBEncrypter(newCFB(c, s, iv), w);
+}
+
diff --git a/src/lib/crypto/block/cfb_aes_test.go b/src/lib/crypto/block/cfb_aes_test.go
new file mode 100644
index 000000000..6c793dba8
--- /dev/null
+++ b/src/lib/crypto/block/cfb_aes_test.go
@@ -0,0 +1,316 @@
+// 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.
+
+// CFB AES test vectors.
+
+// See U.S. National Institute of Standards and Technology (NIST)
+// Special Publication 800-38A, ``Recommendation for Block Cipher
+// Modes of Operation,'' 2001 Edition, pp. 29-52.
+
+package block
+
+// gobuild: $GC ecb_aes_test.go
+
+import (
+	"crypto/aes";
+	"crypto/block";
+	"io";
+	"os";
+	"testing";
+
+	"./ecb_aes_test";
+)
+
+type cfbTest struct {
+	name string;
+	s int;
+	key []byte;
+	iv []byte;
+	in []byte;
+	out []byte;
+}
+
+var cfbAESTests = []cfbTest {
+	cfbTest {
+		"CFB1-AES128",
+		1,
+		commonKey128,
+		commonIV,
+		[]byte{
+			0<<7 | 1<<6 | 1<<5 | 0<<4 | 1<<3 | 0<<2 | 1<<1,
+			1<<7 | 1<<6 | 0<<5 | 0<<4 | 0<<3 | 0<<2 | 0<<1,
+		},
+		[]byte{
+			0<<7 | 1<<6 | 1<<5 | 0<<4 | 1<<3 | 0<<2 | 0<<1,
+			1<<7 | 0<<6 | 1<<5 | 1<<4 | 0<<3 | 0<<2 | 1<<1,
+		},
+	},
+	cfbTest {
+		"CFB1-AES192",
+		1,
+		commonKey192,
+		commonIV,
+		[]byte{
+			0<<7 | 1<<6 | 1<<5 | 0<<4 | 1<<3 | 0<<2 | 1<<1,
+			1<<7 | 1<<6 | 0<<5 | 0<<4 | 0<<3 | 0<<2 | 0<<1,
+		},
+		[]byte{
+			1<<7 | 0<<6 | 0<<5 | 1<<4 | 0<<3 | 0<<2 | 1<<1,
+			0<<7 | 1<<6 | 0<<5 | 1<<4 | 1<<3 | 0<<2 | 0<<1,
+		},
+	},
+	cfbTest {
+		"CFB1-AES256",
+		1,
+		commonKey256,
+		commonIV,
+		[]byte{
+			0<<7 | 1<<6 | 1<<5 | 0<<4 | 1<<3 | 0<<2 | 1<<1,
+			1<<7 | 1<<6 | 0<<5 | 0<<4 | 0<<3 | 0<<2 | 0<<1,
+		},
+		[]byte{
+			1<<7 | 0<<6 | 0<<5 | 1<<4 | 0<<3 | 0<<2 | 0<<1,
+			0<<7 | 0<<6 | 1<<5 | 0<<4 | 1<<3 | 0<<2 | 0<<1,
+		},
+	},
+
+	cfbTest {
+		"CFB8-AES128",
+		8,
+		commonKey128,
+		commonIV,
+		[]byte{
+			0x6b,
+			0xc1,
+			0xbe,
+			0xe2,
+			0x2e,
+			0x40,
+			0x9f,
+			0x96,
+			0xe9,
+			0x3d,
+			0x7e,
+			0x11,
+			0x73,
+			0x93,
+			0x17,
+			0x2a,
+			0xae,
+			0x2d,
+		},
+		[]byte{
+			0x3b,
+			0x79,
+			0x42,
+			0x4c,
+			0x9c,
+			0x0d,
+			0xd4,
+			0x36,
+			0xba,
+			0xce,
+			0x9e,
+			0x0e,
+			0xd4,
+			0x58,
+			0x6a,
+			0x4f,
+			0x32,
+			0xb9,
+		},
+	},
+
+	cfbTest {
+		"CFB8-AES192",
+		8,
+		commonKey192,
+		commonIV,
+		[]byte{
+			0x6b,
+			0xc1,
+			0xbe,
+			0xe2,
+			0x2e,
+			0x40,
+			0x9f,
+			0x96,
+			0xe9,
+			0x3d,
+			0x7e,
+			0x11,
+			0x73,
+			0x93,
+			0x17,
+			0x2a,
+			0xae,
+			0x2d,
+		},
+		[]byte{
+			0xcd,
+			0xa2,
+			0x52,
+			0x1e,
+			0xf0,
+			0xa9,
+			0x05,
+			0xca,
+			0x44,
+			0xcd,
+			0x05,
+			0x7c,
+			0xbf,
+			0x0d,
+			0x47,
+			0xa0,
+			0x67,
+			0x8a,
+		},
+	},
+
+	cfbTest {
+		"CFB8-AES256",
+		8,
+		commonKey256,
+		commonIV,
+		[]byte{
+			0x6b,
+			0xc1,
+			0xbe,
+			0xe2,
+			0x2e,
+			0x40,
+			0x9f,
+			0x96,
+			0xe9,
+			0x3d,
+			0x7e,
+			0x11,
+			0x73,
+			0x93,
+			0x17,
+			0x2a,
+			0xae,
+			0x2d,
+		},
+		[]byte{
+			0xdc,
+			0x1f,
+			0x1a,
+			0x85,
+			0x20,
+			0xa6,
+			0x4d,
+			0xb5,
+			0x5f,
+			0xcc,
+			0x8a,
+			0xc5,
+			0x54,
+			0x84,
+			0x4e,
+			0x88,
+			0x97,
+			0x00,
+		},
+	},
+
+	cfbTest {
+		"CFB128-AES128",
+		128,
+		commonKey128,
+		commonIV,
+		[]byte{
+			0x6b, 0xc1, 0xbe, 0xe2, 0x2e, 0x40, 0x9f, 0x96, 0xe9, 0x3d, 0x7e, 0x11, 0x73, 0x93, 0x17, 0x2a,
+			0xae, 0x2d, 0x8a, 0x57, 0x1e, 0x03, 0xac, 0x9c, 0x9e, 0xb7, 0x6f, 0xac, 0x45, 0xaf, 0x8e, 0x51,
+			0x30, 0xc8, 0x1c, 0x46, 0xa3, 0x5c, 0xe4, 0x11, 0xe5, 0xfb, 0xc1, 0x19, 0x1a, 0x0a, 0x52, 0xef,
+			0xf6, 0x9f, 0x24, 0x45, 0xdf, 0x4f, 0x9b, 0x17, 0xad, 0x2b, 0x41, 0x7b, 0xe6, 0x6c, 0x37, 0x10,
+		},
+		[]byte{
+			0x3b, 0x3f, 0xd9, 0x2e, 0xb7, 0x2d, 0xad, 0x20, 0x33, 0x34, 0x49, 0xf8, 0xe8, 0x3c, 0xfb, 0x4a,
+			0xc8, 0xa6, 0x45, 0x37, 0xa0, 0xb3, 0xa9, 0x3f, 0xcd, 0xe3, 0xcd, 0xad, 0x9f, 0x1c, 0xe5, 0x8b,
+			0x26, 0x75, 0x1f, 0x67, 0xa3, 0xcb, 0xb1, 0x40, 0xb1, 0x80, 0x8c, 0xf1, 0x87, 0xa4, 0xf4, 0xdf,
+			0xc0, 0x4b, 0x05, 0x35, 0x7c, 0x5d, 0x1c, 0x0e, 0xea, 0xc4, 0xc6, 0x6f, 0x9f, 0xf7, 0xf2, 0xe6,
+		},
+	},
+
+	cfbTest {
+		"CFB128-AES192",
+		128,
+		commonKey192,
+		commonIV,
+		[]byte{
+			0x6b, 0xc1, 0xbe, 0xe2, 0x2e, 0x40, 0x9f, 0x96, 0xe9, 0x3d, 0x7e, 0x11, 0x73, 0x93, 0x17, 0x2a,
+			0xae, 0x2d, 0x8a, 0x57, 0x1e, 0x03, 0xac, 0x9c, 0x9e, 0xb7, 0x6f, 0xac, 0x45, 0xaf, 0x8e, 0x51,
+			0x30, 0xc8, 0x1c, 0x46, 0xa3, 0x5c, 0xe4, 0x11, 0xe5, 0xfb, 0xc1, 0x19, 0x1a, 0x0a, 0x52, 0xef,
+			0xf6, 0x9f, 0x24, 0x45, 0xdf, 0x4f, 0x9b, 0x17, 0xad, 0x2b, 0x41, 0x7b, 0xe6, 0x6c, 0x37, 0x10,
+		},
+		[]byte{
+			0xcd, 0xc8, 0x0d, 0x6f, 0xdd, 0xf1, 0x8c, 0xab, 0x34, 0xc2, 0x59, 0x09, 0xc9, 0x9a, 0x41, 0x74,
+			0x67, 0xce, 0x7f, 0x7f, 0x81, 0x17, 0x36, 0x21, 0x96, 0x1a, 0x2b, 0x70, 0x17, 0x1d, 0x3d, 0x7a,
+			0x2e, 0x1e, 0x8a, 0x1d, 0xd5, 0x9b, 0x88, 0xb1, 0xc8, 0xe6, 0x0f, 0xed, 0x1e, 0xfa, 0xc4, 0xc9,
+			0xc0, 0x5f, 0x9f, 0x9c, 0xa9, 0x83, 0x4f, 0xa0, 0x42, 0xae, 0x8f, 0xba, 0x58, 0x4b, 0x09, 0xff,
+		},
+	},
+
+	cfbTest {
+		"CFB128-AES256",
+		128,
+		commonKey256,
+		commonIV,
+		[]byte{
+			0x6b, 0xc1, 0xbe, 0xe2, 0x2e, 0x40, 0x9f, 0x96, 0xe9, 0x3d, 0x7e, 0x11, 0x73, 0x93, 0x17, 0x2a,
+			0xae, 0x2d, 0x8a, 0x57, 0x1e, 0x03, 0xac, 0x9c, 0x9e, 0xb7, 0x6f, 0xac, 0x45, 0xaf, 0x8e, 0x51,
+			0x30, 0xc8, 0x1c, 0x46, 0xa3, 0x5c, 0xe4, 0x11, 0xe5, 0xfb, 0xc1, 0x19, 0x1a, 0x0a, 0x52, 0xef,
+			0xf6, 0x9f, 0x24, 0x45, 0xdf, 0x4f, 0x9b, 0x17, 0xad, 0x2b, 0x41, 0x7b, 0xe6, 0x6c, 0x37, 0x10,
+		},
+		[]byte{
+			0xdc, 0x7e, 0x84, 0xbf, 0xda, 0x79, 0x16, 0x4b, 0x7e, 0xcd, 0x84, 0x86, 0x98, 0x5d, 0x38, 0x60,
+			0x39, 0xff, 0xed, 0x14, 0x3b, 0x28, 0xb1, 0xc8, 0x32, 0x11, 0x3c, 0x63, 0x31, 0xe5, 0x40, 0x7b,
+			0xdf, 0x10, 0x13, 0x24, 0x15, 0xe5, 0x4b, 0x92, 0xa1, 0x3e, 0xd0, 0xa8, 0x26, 0x7a, 0xe2, 0xf9,
+			0x75, 0xa3, 0x85, 0x74, 0x1a, 0xb9, 0xce, 0xf8, 0x20, 0x31, 0x62, 0x3d, 0x55, 0xb1, 0xe4, 0x71,
+		},
+	},
+}
+
+func TestCFB_AES(t *testing.T) {
+	for i, tt := range cfbAESTests {
+		test := tt.name;
+
+		if tt.s == 1 {
+			// 1-bit CFB not implemented
+			continue;
+		}
+
+		c, err := aes.NewCipher(tt.key);
+		if err != nil {
+			t.Errorf("%s: NewCipher(%d bytes) = %s", test, len(tt.key), err);
+			continue;
+		}
+
+		var crypt io.ByteBuffer;
+		w := NewCFBEncrypter(c, tt.s, tt.iv, &crypt);
+		var r io.Reader = io.NewByteReader(tt.in);
+		n, err := io.Copy(r, w);
+		if n != int64(len(tt.in)) || err != nil {
+			t.Errorf("%s: CFBEncrypter io.Copy = %d, %v want %d, nil", test, n, err, len(tt.in));
+		} else if d := crypt.Data(); !same(tt.out, d) {
+			t.Errorf("%s: CFBEncrypter\nhave %x\nwant %x", test, d, tt.out);
+		}
+
+		var plain io.ByteBuffer;
+		r = NewCFBDecrypter(c, tt.s, tt.iv, io.NewByteReader(tt.out));
+		w = &plain;
+		n, err = io.Copy(r, w);
+		if n != int64(len(tt.out)) || err != nil {
+			t.Errorf("%s: CFBDecrypter io.Copy = %d, %v want %d, nil", test, n, err, len(tt.out));
+		} else if d := plain.Data(); !same(tt.in, d) {
+			t.Errorf("%s: CFBDecrypter\nhave %x\nwant %x", test, d, tt.in);
+		}
+
+		if t.Failed() {
+			break;
+		}
+	}
+}
diff --git a/src/lib/crypto/block/cipher.go b/src/lib/crypto/block/cipher.go
new file mode 100644
index 000000000..8bff1b878
--- /dev/null
+++ b/src/lib/crypto/block/cipher.go
@@ -0,0 +1,58 @@
+// 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.
+
+// The block package implements standard block cipher modes
+// that can be wrapped around low-level block cipher implementations.
+// See http://csrc.nist.gov/groups/ST/toolkit/BCM/current_modes.html
+// and NIST Special Publication 800-38A.
+package block
+
+// A Cipher represents an implementation of block cipher
+// using a given key.  It provides the capability to encrypt
+// or decrypt individual blocks.  The mode implementations
+// extend that capability to streams of blocks.
+type Cipher interface {
+	// BlockSize returns the cipher's block size.
+	BlockSize() int;
+
+	// Encrypt encrypts the first block in src into dst.
+	// Src and dst may point at the same memory.
+	Encrypt(src, dst []byte);
+
+	// Decrypt decrypts the first block in src into dst.
+	// Src and dst may point at the same memory.
+	Decrypt(src, dst []byte);
+}
+
+// Utility routines
+
+func shift1(src, dst []byte) byte {
+	var b byte;
+	for i := len(src)-1; i >= 0; i-- {
+		bb := src[i]>>7;
+		dst[i] = src[i]<<1 | b;
+		b = bb;
+	}
+	return b;
+}
+
+func same(p, q []byte) bool {
+	if len(p) != len(q) {
+		return false;
+	}
+	for i := 0; i < len(p); i++ {
+		if p[i] != q[i] {
+			return false;
+		}
+	}
+	return true;
+}
+
+func copy(p []byte) []byte {
+	q := make([]byte, len(p));
+	for i, b := range p {
+		q[i] = b;
+	}
+	return q;
+}
diff --git a/src/lib/crypto/block/ecb.go b/src/lib/crypto/block/ecb.go
new file mode 100644
index 000000000..141d38cc8
--- /dev/null
+++ b/src/lib/crypto/block/ecb.go
@@ -0,0 +1,271 @@
+// 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.
+
+// Electronic codebook (ECB) mode.
+// ECB is a fancy name for ``encrypt and decrypt each block separately.''
+// It's a pretty bad thing to do for any large amount of data (more than one block),
+// because the individual blocks can still be identified, duplicated, and reordered.
+// The ECB implementation exists mainly to provide buffering for
+// the other modes, which wrap it by providing modified Ciphers.
+
+// See NIST SP 800-38A, pp 9-10
+
+package block
+
+import (
+	"crypto/block";
+	"io";
+	"os";
+)
+
+type ecbDecrypter struct {
+	c Cipher;
+	r io.Reader;
+	blockSize int;		// block size
+
+	// Buffered data.
+	// The buffer buf is used as storage for both
+	// plain or crypt; at least one of those is nil at any given time.
+	buf []byte;
+	plain []byte;	// plain text waiting to be read
+	crypt []byte;	// ciphertext waiting to be decrypted
+}
+
+// Read into x.crypt until it has a full block or EOF or an error happens.
+func (x *ecbDecrypter) fillCrypt() os.Error {
+	var err os.Error;
+	for len(x.crypt) < x.blockSize {
+		off := len(x.crypt);
+		var m int;
+		m, err = x.r.Read(x.crypt[off:x.blockSize]);
+		x.crypt = x.crypt[0:off+m];
+		if m == 0 {
+			break;
+		}
+
+		// If an error happened but we got enough
+		// data to do some decryption, we can decrypt
+		// first and report the error (with some data) later.
+		// But if we don't have enough to decrypt,
+		// have to stop now.
+		if err != nil && len(x.crypt) < x.blockSize {
+			break;
+		}
+	}
+	return err;
+}
+
+// Read from plain text buffer into p.
+func (x *ecbDecrypter) readPlain(p []byte) int {
+	n := len(x.plain);
+	if n > len(p) {
+		n = len(p);
+	}
+	for i := 0; i < n; i++ {
+		p[i] = x.plain[i];
+	}
+	if n < len(x.plain) {
+		x.plain = x.plain[n:len(x.plain)];
+	} else {
+		x.plain = nil;
+	}
+	return n;
+}
+
+func (x *ecbDecrypter) Read(p []byte) (n int, err os.Error) {
+	if len(p) == 0 {
+		return;
+	}
+
+	// If there's no plaintext waiting and p is not big enough
+	// to hold a whole cipher block, we'll have to work in the
+	// cipher text buffer.  Set it to non-nil so that the
+	// code below will fill it.
+	if x.plain == nil && len(p) < x.blockSize && x.crypt == nil {
+		x.crypt = x.buf[0:0];
+	}
+
+	// If there is a leftover cipher text buffer,
+	// try to accumulate a full block.
+	if x.crypt != nil {
+		err = x.fillCrypt();
+		if err != nil || len(x.crypt) == 0 {
+			return;
+		}
+		x.c.Decrypt(x.crypt, x.crypt);
+		x.plain = x.crypt;
+		x.crypt = nil;
+	}
+
+	// If there is a leftover plain text buffer, read from it.
+	if x.plain != nil {
+		n = x.readPlain(p);
+		return;
+	}
+
+	// Read and decrypt directly in caller's buffer.
+	n, err = io.ReadAtLeast(x.r, p, x.blockSize);
+	if err == io.ErrEOF && n == 0 {
+		// EOF is okay on block boundary
+		err = nil;
+		return;
+	}
+	var i int;
+	for i = 0; i+x.blockSize <= n; i += x.blockSize {
+		a := p[i:i+x.blockSize];
+		x.c.Decrypt(a, a);
+	}
+
+	// There might be an encrypted fringe remaining.
+	// Save it for next time.
+	if i < n {
+		p = p[i:n];
+		for j, v := range p {
+			x.buf[j] = p[j];
+		}
+		x.crypt = x.buf[0:len(p)];
+		n = i;
+	}
+
+	return;
+}
+
+// NewECBDecrypter returns a reader that reads data from r and decrypts it using c.
+// It decrypts by calling c.Decrypt on each block in sequence;
+// this mode is known as electronic codebook mode, or ECB.
+// The returned Reader does not buffer or read ahead except
+// as required by the cipher's block size.
+func NewECBDecrypter(c Cipher, r io.Reader) io.Reader {
+	x := new(ecbDecrypter);
+	x.c = c;
+	x.r = r;
+	x.blockSize = c.BlockSize();
+	x.buf = make([]byte, x.blockSize);
+	return x;
+}
+
+type ecbEncrypter struct {
+	c Cipher;
+	w io.Writer;
+	blockSize int;
+
+	// Buffered data.
+	// The buffer buf is used as storage for both
+	// plain or crypt.  If both are non-nil, plain
+	// follows crypt in buf.
+	buf []byte;
+	plain []byte;	// plain text waiting to be encrypted
+	crypt []byte;	// encrypted text waiting to be written
+}
+
+// Flush the x.crypt buffer to x.w.
+func (x *ecbEncrypter) flushCrypt() os.Error {
+	if len(x.crypt) == 0 {
+		return nil;
+	}
+	n, err := x.w.Write(x.crypt);
+	if n < len(x.crypt) {
+		x.crypt = x.crypt[n:len(x.crypt)];
+		if err == nil {
+			err = io.ErrShortWrite;
+		}
+	}
+	if err != nil {
+		return err;
+	}
+	x.crypt = nil;
+	return nil;
+}
+
+// Slide x.plain down to the beginning of x.buf.
+// Plain is known to have less than one block of data,
+// so this is cheap enough.
+func (x *ecbEncrypter) slidePlain() {
+	if len(x.plain) == 0 {
+		x.plain = x.buf[0:0];
+	} else if cap(x.plain) < cap(x.buf) {
+		// plain and buf share same data,
+		// but buf is before plain, so forward loop is correct
+		for i := 0; i < len(x.plain); i++ {
+			x.buf[i] = x.plain[i];
+		}
+		x.plain = x.buf[0:len(x.plain)];
+	}
+}
+
+// Fill x.plain from the data in p.
+// Return the number of bytes copied.
+func (x *ecbEncrypter) fillPlain(p []byte) int {
+	off := len(x.plain);
+	n := len(p);
+	if max := cap(x.plain) - off; n > max {
+		n = max;
+	}
+	x.plain = x.plain[0:off+n];
+	for i := 0; i < n; i++ {
+		x.plain[off + i] = p[i];
+	}
+	return n;
+}
+
+// Encrypt x.plain; record encrypted range as x.crypt.
+func (x *ecbEncrypter) encrypt() {
+	var i int;
+	n := len(x.plain);
+	for i = 0; i+x.blockSize <= n; i += x.blockSize {
+		a := x.plain[i:i+x.blockSize];
+		x.c.Encrypt(a, a);
+	}
+	x.crypt = x.plain[0:i];
+	x.plain = x.plain[i:n];
+}
+
+func (x *ecbEncrypter) Write(p []byte) (n int, err os.Error) {
+	for {
+		// If there is data waiting to be written, write it.
+		// This can happen on the first iteration
+		// if a write failed in an earlier call.
+		if err = x.flushCrypt(); err != nil {
+			return;
+		}
+
+		// Now that encrypted data is gone (flush ran),
+		// perhaps we need to slide the plaintext down.
+		x.slidePlain();
+
+		// Fill plaintext buffer from p.
+		m := x.fillPlain(p);
+		if m == 0 {
+			break;
+		}
+		n += m;
+		p = p[m:len(p)];
+
+		// Encrypt, adjusting crypt and plain.
+		x.encrypt();
+
+		// Write x.crypt.
+		if err = x.flushCrypt(); err != nil {
+			break;
+		}
+	}
+	return;
+}
+
+// NewECBEncrypter returns a writer that encrypts data using c and writes it to w.
+// It encrypts by calling c.Encrypt on each block in sequence;
+// this mode is known as electronic codebook mode, or ECB.
+// The returned Writer does no buffering except as required
+// by the cipher's block size, so there is no need for a Flush method.
+func NewECBEncrypter(c Cipher, w io.Writer) io.Writer {
+	x := new(ecbEncrypter);
+	x.c = c;
+	x.w = w;
+	x.blockSize = c.BlockSize();
+
+	// Create a buffer that is an integral number of blocks.
+	x.buf = make([]byte, 8192/x.blockSize * x.blockSize);
+	return x;
+}
+
diff --git a/src/lib/crypto/block/ecb_aes_test.go b/src/lib/crypto/block/ecb_aes_test.go
new file mode 100644
index 000000000..de8a624b9
--- /dev/null
+++ b/src/lib/crypto/block/ecb_aes_test.go
@@ -0,0 +1,136 @@
+// 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.
+
+// ECB AES test vectors.
+
+// See U.S. National Institute of Standards and Technology (NIST)
+// Special Publication 800-38A, ``Recommendation for Block Cipher
+// Modes of Operation,'' 2001 Edition, pp. 24-27.
+
+package block
+
+import (
+	"crypto/aes";
+	"crypto/block";
+	"io";
+	"os";
+	"testing";
+)
+
+type ecbTest struct {
+	name string;
+	key []byte;
+	in []byte;
+	out []byte;
+}
+
+var commonInput = []byte {
+	0x6b, 0xc1, 0xbe, 0xe2, 0x2e, 0x40, 0x9f, 0x96, 0xe9, 0x3d, 0x7e, 0x11, 0x73, 0x93, 0x17, 0x2a,
+	0xae, 0x2d, 0x8a, 0x57, 0x1e, 0x03, 0xac, 0x9c, 0x9e, 0xb7, 0x6f, 0xac, 0x45, 0xaf, 0x8e, 0x51,
+	0x30, 0xc8, 0x1c, 0x46, 0xa3, 0x5c, 0xe4, 0x11, 0xe5, 0xfb, 0xc1, 0x19, 0x1a, 0x0a, 0x52, 0xef,
+	0xf6, 0x9f, 0x24, 0x45, 0xdf, 0x4f, 0x9b, 0x17, 0xad, 0x2b, 0x41, 0x7b, 0xe6, 0x6c, 0x37, 0x10,
+}
+
+var commonKey128 = []byte {
+	0x2b, 0x7e, 0x15, 0x16, 0x28, 0xae, 0xd2, 0xa6, 0xab, 0xf7, 0x15, 0x88, 0x09, 0xcf, 0x4f, 0x3c,
+}
+
+var commonKey192 = []byte {
+	0x8e, 0x73, 0xb0, 0xf7, 0xda, 0x0e, 0x64, 0x52, 0xc8, 0x10, 0xf3, 0x2b, 0x80, 0x90, 0x79, 0xe5,
+	0x62, 0xf8, 0xea, 0xd2, 0x52, 0x2c, 0x6b, 0x7b,
+}
+
+var commonKey256 = []byte {
+	0x60, 0x3d, 0xeb, 0x10, 0x15, 0xca, 0x71, 0xbe, 0x2b, 0x73, 0xae, 0xf0, 0x85, 0x7d, 0x77, 0x81,
+	0x1f, 0x35, 0x2c, 0x07, 0x3b, 0x61, 0x08, 0xd7, 0x2d, 0x98, 0x10, 0xa3, 0x09, 0x14, 0xdf, 0xf4,
+}
+
+var commonIV = []byte {
+	0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f,
+}
+
+var ecbAESTests = []ecbTest {
+	// FIPS 197, Appendix B, C
+	ecbTest {
+		"FIPS-197 Appendix B",
+		commonKey128,
+		[]byte {
+			0x32, 0x43, 0xf6, 0xa8, 0x88, 0x5a, 0x30, 0x8d, 0x31, 0x31, 0x98, 0xa2, 0xe0, 0x37, 0x07, 0x34,
+		},
+		[]byte {
+			0x39, 0x25, 0x84, 0x1d, 0x02, 0xdc, 0x09, 0xfb, 0xdc, 0x11, 0x85, 0x97, 0x19, 0x6a, 0x0b, 0x32,
+		}
+	},
+
+	// NIST SP 800-38A pp 24-27
+	ecbTest {
+		"ECB-AES128",
+		commonKey128,
+		commonInput,
+		[]byte {
+			0x3a, 0xd7, 0x7b, 0xb4, 0x0d, 0x7a, 0x36, 0x60, 0xa8, 0x9e, 0xca, 0xf3, 0x24, 0x66, 0xef, 0x97,
+			0xf5, 0xd3, 0xd5, 0x85, 0x03, 0xb9, 0x69, 0x9d, 0xe7, 0x85, 0x89, 0x5a, 0x96, 0xfd, 0xba, 0xaf,
+			0x43, 0xb1, 0xcd, 0x7f, 0x59, 0x8e, 0xce, 0x23, 0x88, 0x1b, 0x00, 0xe3, 0xed, 0x03, 0x06, 0x88,
+			0x7b, 0x0c, 0x78, 0x5e, 0x27, 0xe8, 0xad, 0x3f, 0x82, 0x23, 0x20, 0x71, 0x04, 0x72, 0x5d, 0xd4,
+		}
+	},
+	ecbTest {
+		"ECB-AES192",
+		commonKey192,
+		commonInput,
+		[]byte {
+			0xbd, 0x33, 0x4f, 0x1d, 0x6e, 0x45, 0xf2, 0x5f, 0xf7, 0x12, 0xa2, 0x14, 0x57, 0x1f, 0xa5, 0xcc,
+			0x97, 0x41, 0x04, 0x84, 0x6d, 0x0a, 0xd3, 0xad, 0x77, 0x34, 0xec, 0xb3, 0xec, 0xee, 0x4e, 0xef,
+			0xef, 0x7a, 0xfd, 0x22, 0x70, 0xe2, 0xe6, 0x0a, 0xdc, 0xe0, 0xba, 0x2f, 0xac, 0xe6, 0x44, 0x4e,
+			0x9a, 0x4b, 0x41, 0xba, 0x73, 0x8d, 0x6c, 0x72, 0xfb, 0x16, 0x69, 0x16, 0x03, 0xc1, 0x8e, 0x0e,
+		}
+	},
+	ecbTest {
+		"ECB-AES256",
+		commonKey256,
+		commonInput,
+		[]byte {
+			0xf3, 0xee, 0xd1, 0xbd, 0xb5, 0xd2, 0xa0, 0x3c, 0x06, 0x4b, 0x5a, 0x7e, 0x3d, 0xb1, 0x81, 0xf8,
+			0x59, 0x1c, 0xcb, 0x10, 0xd4, 0x10, 0xed, 0x26, 0xdc, 0x5b, 0xa7, 0x4a, 0x31, 0x36, 0x28, 0x70,
+			0xb6, 0xed, 0x21, 0xb9, 0x9c, 0xa6, 0xf4, 0xf9, 0xf1, 0x53, 0xe7, 0xb1, 0xbe, 0xaf, 0xed, 0x1d,
+			0x23, 0x30, 0x4b, 0x7a, 0x39, 0xf9, 0xf3, 0xff, 0x06, 0x7d, 0x8d, 0x8f, 0x9e, 0x24, 0xec, 0xc7,
+		}
+	}
+}
+
+func TestECB_AES(t *testing.T) {
+	for i, tt := range ecbAESTests {
+		test := tt.name;
+
+		c, err := aes.NewCipher(tt.key);
+		if err != nil {
+			t.Errorf("%s: NewCipher(%d bytes) = %s", test, len(tt.key), err);
+			continue;
+		}
+
+		var crypt io.ByteBuffer;
+		w := NewECBEncrypter(c, &crypt);
+		var r io.Reader = io.NewByteReader(tt.in);
+		n, err := io.Copy(r, w);
+		if n != int64(len(tt.in)) || err != nil {
+			t.Errorf("%s: ECBReader io.Copy = %d, %v want %d, nil", test, n, err, len(tt.in));
+		} else if d := crypt.Data(); !same(tt.out, d) {
+			t.Errorf("%s: ECBReader\nhave %x\nwant %x", test, d, tt.out);
+		}
+
+		var plain io.ByteBuffer;
+		r = NewECBDecrypter(c, io.NewByteReader(tt.out));
+		w = &plain;
+		n, err = io.Copy(r, w);
+		if n != int64(len(tt.out)) || err != nil {
+			t.Errorf("%s: ECBWriter io.Copy = %d, %v want %d, nil", test, n, err, len(tt.out));
+		} else if d := plain.Data(); !same(tt.in, d) {
+			t.Errorf("%s: ECBWriter\nhave %x\nwant %x", test, d, tt.in);
+		}
+
+		if t.Failed() {
+			break;
+		}
+	}
+}
diff --git a/src/lib/crypto/block/ecb_test.go b/src/lib/crypto/block/ecb_test.go
new file mode 100644
index 000000000..968893a9b
--- /dev/null
+++ b/src/lib/crypto/block/ecb_test.go
@@ -0,0 +1,183 @@
+// 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 block
+
+import (
+	"crypto/block";
+	"fmt";
+	"io";
+	"testing";
+	"testing/iotest";
+)
+
+// Simple Cipher for testing: adds an incrementing amount
+// to each byte in each
+type IncCipher struct {
+	blockSize int;
+	delta byte;
+	encrypting bool;
+}
+
+func (c *IncCipher) BlockSize() int {
+	return c.blockSize;
+}
+
+func (c *IncCipher) Encrypt(src, dst []byte) {
+	if !c.encrypting {
+		panicln("encrypt: not encrypting");
+	}
+	if len(src) != c.blockSize || len(dst) != c.blockSize {
+		panicln("encrypt: wrong block size", c.blockSize, len(src), len(dst));
+	}
+	c.delta++;
+	for i, b := range src {
+		dst[i] = b + c.delta;
+	}
+}
+
+func (c *IncCipher) Decrypt(src, dst []byte) {
+	if c.encrypting {
+		panicln("decrypt: not decrypting");
+	}
+	if len(src) != c.blockSize || len(dst) != c.blockSize {
+		panicln("decrypt: wrong block size", c.blockSize, len(src), len(dst));
+	}
+	c.delta--;
+	for i, b := range src {
+		dst[i] = b + c.delta;
+	}
+}
+
+func TestECBEncrypter(t *testing.T) {
+	var plain, crypt [256]byte;
+	for i := 0; i < len(plain); i++ {
+		plain[i] = byte(i);
+	}
+	b := new(io.ByteBuffer);
+	for block := 1; block <= 64; block *= 2 {
+		// compute encrypted version
+		delta := byte(0);
+		for i := 0; i < len(crypt); i++ {
+			if i % block == 0 {
+				delta++;
+			}
+			crypt[i] = plain[i] + delta;
+		}
+
+		for frag := 0; frag < 2; frag++ {
+			c := &IncCipher{block, 0, true};
+			b.Reset();
+			r := io.NewByteReader(&plain);
+			w := NewECBEncrypter(c, b);
+
+			// copy plain into w in increasingly large chunks: 1, 1, 2, 4, 8, ...
+			// if frag != 0, move the 1 to the end to cause fragmentation.
+			if frag == 0 {
+				nn, err := io.Copyn(r, w, 1);
+				if err != nil {
+					t.Errorf("block=%d frag=0: first Copyn: %s", block, err);
+					continue;
+				}
+			}
+			for n := 1; n <= len(plain)/2; n *= 2 {
+				nn, err := io.Copyn(r, w, int64(n));
+				if err != nil {
+					t.Errorf("block=%d frag=%d: Copyn %d: %s", block, frag, n, err);
+				}
+			}
+			if frag != 0 {
+				nn, err := io.Copyn(r, w, 1);
+				if err != nil {
+					t.Errorf("block=%d frag=1: last Copyn: %s", block, err);
+					continue;
+				}
+			}
+
+			// check output
+			data := b.Data();
+			if len(data) != len(crypt) {
+				t.Errorf("block=%d frag=%d: want %d bytes, got %d", block, frag, len(crypt), len(data));
+				continue;
+			}
+
+			if string(data) != string(&crypt) {
+				t.Errorf("block=%d frag=%d: want %x got %x", block, frag, data, crypt);
+			}
+		}
+	}
+}
+
+func testECBDecrypter(t *testing.T, maxio int) {
+	var readers = []func(io.Reader) io.Reader {
+		func (r io.Reader) io.Reader { return r },
+		iotest.OneByteReader,
+		iotest.HalfReader,
+	};
+	var plain, crypt [256]byte;
+	for i := 0; i < len(plain); i++ {
+		plain[i] = byte(255 - i);
+	}
+	b := new(io.ByteBuffer);
+	for block := 1; block <= 64 && block <= maxio; block *= 2 {
+		// compute encrypted version
+		delta := byte(0);
+		for i := 0; i < len(crypt); i++ {
+			if i % block == 0 {
+				delta++;
+			}
+			crypt[i] = plain[i] + delta;
+		}
+
+		for mode := 0; mode < len(readers); mode++ {
+			for frag := 0; frag < 2; frag++ {
+				test := fmt.Sprintf("block=%d mode=%d frag=%d maxio=%d", block, mode, frag, maxio);
+				c := &IncCipher{block, 0, false};
+				b.Reset();
+				r := NewECBDecrypter(c, readers[mode](io.NewByteReader(crypt[0:maxio])));
+
+				// read from crypt in increasingly large chunks: 1, 1, 2, 4, 8, ...
+				// if frag == 1, move the 1 to the end to cause fragmentation.
+				if frag == 0 {
+					nn, err := io.Copyn(r, b, 1);
+					if err != nil {
+						t.Errorf("%s: first Copyn: %s", test, err);
+						continue;
+					}
+				}
+				for n := 1; n <= maxio/2; n *= 2 {
+					nn, err := io.Copyn(r, b, int64(n));
+					if err != nil {
+						t.Errorf("%s: Copyn %d: %s", test, n, err);
+					}
+				}
+				if frag != 0 {
+					nn, err := io.Copyn(r, b, 1);
+					if err != nil {
+						t.Errorf("%s: last Copyn: %s", test, err);
+						continue;
+					}
+				}
+
+				// check output
+				data := b.Data();
+				if len(data) != maxio {
+					t.Errorf("%s: want %d bytes, got %d", test, maxio, len(data));
+					continue;
+				}
+
+				if string(data) != string(plain[0:maxio]) {
+					t.Errorf("%s: input=%x want %x got %x", test, crypt[0:maxio], plain[0:maxio], data);
+				}
+			}
+		}
+	}
+}
+
+func TestECBDecrypter(t *testing.T) {
+	// Do shorter I/O sizes first; they're easier to debug.
+	for n := 1; n <= 256 && !t.Failed(); n *= 2 {
+		testECBDecrypter(t, n);
+	}
+}
diff --git a/src/lib/io/io.go b/src/lib/io/io.go
index 91b6ffd8b..c120d8d44 100644
--- a/src/lib/io/io.go
+++ b/src/lib/io/io.go
@@ -27,6 +27,9 @@ var ErrShortWrite os.Error = &Error{"short write"}
 
 
 // Reader is the interface that wraps the basic Read method.
+// An implementation of Read is allowed to use all of p for
+// scratch space during the call, even if it eventually returns
+// n < len(p).
 type Reader interface {
 	Read(p []byte) (n int, err os.Error);
 }
@@ -80,10 +83,11 @@ func WriteString(w Writer, s string) (n int, err os.Error) {
 	return w.Write(StringBytes(s))
 }
 
-// FullRead reads r until the buffer buf is full, or until EOF or error.
-func FullRead(r Reader, buf []byte) (n int, err os.Error) {
+// ReadAtLeast reads r into buf until at least min bytes have been read,
+// or until EOF or error.
+func ReadAtLeast(r Reader, buf []byte, min int) (n int, err os.Error) {
 	n = 0;
-	for n < len(buf) {
+	for n < min {
 		nn, e := r.Read(buf[n:len(buf)]);
 		if nn > 0 {
 			n += nn
@@ -98,6 +102,13 @@ func FullRead(r Reader, buf []byte) (n int, err os.Error) {
 	return n, nil
 }
 
+// FullRead reads r until the buffer buf is full, or until EOF or error.
+func FullRead(r Reader, buf []byte) (n int, err os.Error) {
+	// TODO(rsc): 6g bug prevents obvious return
+	n, err = ReadAtLeast(r, buf, len(buf));
+	return;
+}
+
 // Convert something that implements Read into something
 // whose Reads are always FullReads
 type fullRead struct {