add hmac.NewSHA1 and hmac.NewMD5.

fix Reset bug in sha1.
add hmac, sha1, md5 tests.
document hmac.

R=r
DELTA=146  (111 added, 6 deleted, 29 changed)
OCL=29294
CL=29299

src/lib/crypto/hmac/hmac.go

@@ -2,22 +2,34 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// TODO(rsc): comments
-
+// The hmac package implements the Keyed-Hash Message Authentication Code (HMAC)
+// as defined in U.S. Federal Information Processing Standards Publication 198.
+// An HMAC is a cryptographic hash attesting that uses a key to sign a message.
+// The receiver verifies the hash by recomputing it using the same key.
 package hmac
 
 import (
+	"crypto/md5";
+	"crypto/sha1";
 	"hash";
 	"os";
 )
 
-// k0 = key
-// ipad = 0x36 byte repeated to key len
-// opad = 0x5c byte repeated to key len
-// hmac = 
-//	H((k0 ^ opad) || H((k0 ^ ipad) || text))
+// FIPS 198:
+// http://csrc.nist.gov/publications/fips/fips198/fips-198a.pdf
+
+// key is zero padded to 64 bytes
+// ipad = 0x36 byte repeated to 64 bytes
+// opad = 0x5c byte repeated to 64 bytes
+// hmac = H([key ^ opad] H([key ^ ipad] text))
 
 const (
+	// NOTE(rsc): This constant is actually the
+	// underlying hash function's block size.
+	// HMAC is only conventionally used with
+	// MD5 and SHA1, and both use 64-byte blocks.
+	// The hash.Hash interface doesn't provide a
+	// way to find out the block size.
 	padSize = 64;
 )
 
@@ -37,11 +49,6 @@ func (h *hmac) tmpPad(xor byte) {
 	}
 }
 
-func (h *hmac) init() {
-	h.tmpPad(0x36);
-	h.inner.Write(h.tmp[0:padSize]);
-}
-
 func (h *hmac) Sum() []byte {
 	h.tmpPad(0x5c);
 	sum := h.inner.Sum();
@@ -63,10 +70,17 @@ func (h *hmac) Size() int {
 
 func (h *hmac) Reset() {
 	h.inner.Reset();
-	h.init();
+	h.tmpPad(0x36);
+	h.inner.Write(h.tmp[0:padSize]);
 }
 
-func HMAC(h hash.Hash, key []byte) hash.Hash {
+// New returns a new HMAC hash using the given hash and key.
+func New(h hash.Hash, key []byte) hash.Hash {
+	if len(key) > padSize {
+		// If key is too big, hash it.
+		h.Write(key);
+		key = h.Sum();
+	}
 	hm := new(hmac);
 	hm.inner = h;
 	hm.size = h.Size();
@@ -75,6 +89,16 @@ func HMAC(h hash.Hash, key []byte) hash.Hash {
 		hm.key[i] = k;
 	}
 	hm.tmp = make([]byte, padSize + hm.size);
-	hm.init();
+	hm.Reset();
 	return hm;
 }
+
+// NewMD5 returns a new HMAC-MD5 hash using the given key.
+func NewMD5(key []byte) hash.Hash {
+	return New(md5.New(), key);
+}
+
+// NewSHA1 returns a new HMAC-SHA1 hash using the given key.
+func NewSHA1(key []byte) hash.Hash {
+	return New(sha1.New(), key);
+}

src/lib/crypto/hmac/hmac_test.go

@@ -7,21 +7,94 @@ package hmac
 // TODO(rsc): better test
 
 import (
+	"hash";
 	"crypto/hmac";
-	"crypto/md5";
 	"io";
 	"fmt";
 	"testing";
 )
 
-func TestHMAC_MD5(t *testing.T) {
-	// presotto's test
-	inner := md5.New();
-	h := HMAC(inner, io.StringBytes("Jefe"));
-	io.WriteString(h, "what do ya want for nothing?");
-	s := fmt.Sprintf("%x", h.Sum());
-	answer := "750c783e6ab0b503eaa86e310a5db738";
-	if s != answer {
-		t.Error("have", s, "\nwant", answer);
+type hmacTest struct {
+	hash func([]byte) hash.Hash;
+	key []byte;
+	in []byte;
+	out string;
+}
+
+// Tests from US FIPS 198
+// http://csrc.nist.gov/publications/fips/fips198/fips-198a.pdf
+var hmacTests = []hmacTest {
+	hmacTest {
+		NewSHA1,
+		[]byte {
+			0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
+			0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f,
+			0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17,
+			0x18, 0x19, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f,
+			0x20, 0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27,
+			0x28, 0x29, 0x2a, 0x2b, 0x2c, 0x2d, 0x2e, 0x2f,
+			0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37,
+			0x38, 0x39, 0x3a, 0x3b, 0x3c, 0x3d, 0x3e, 0x3f,
+		},
+		io.StringBytes("Sample #1"),
+		"4f4ca3d5d68ba7cc0a1208c9c61e9c5da0403c0a",
+	},
+	hmacTest {
+		NewSHA1,
+		[]byte {
+			0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37,
+			0x38, 0x39, 0x3a, 0x3b, 0x3c, 0x3d, 0x3e, 0x3f,
+			0x40, 0x41, 0x42, 0x43,
+		},
+		io.StringBytes("Sample #2"),
+		"0922d3405faa3d194f82a45830737d5cc6c75d24",
+	},
+	hmacTest {
+		NewSHA1,
+		[]byte {
+			0x50, 0x51, 0x52, 0x53, 0x54, 0x55, 0x56, 0x57,
+			0x58, 0x59, 0x5a, 0x5b, 0x5c, 0x5d, 0x5e, 0x5f,
+			0x60, 0x61, 0x62, 0x63, 0x64, 0x65, 0x66, 0x67,
+			0x68, 0x69, 0x6a, 0x6b, 0x6c, 0x6d, 0x6e, 0x6f,
+			0x70, 0x71, 0x72, 0x73, 0x74, 0x75, 0x76, 0x77,
+			0x78, 0x79, 0x7a, 0x7b, 0x7c, 0x7d, 0x7e, 0x7f,
+			0x80, 0x81, 0x82, 0x83, 0x84, 0x85, 0x86, 0x87,
+			0x88, 0x89, 0x8a, 0x8b, 0x8c, 0x8d, 0x8e, 0x8f,
+			0x90, 0x91, 0x92, 0x93, 0x94, 0x95, 0x96, 0x97,
+			0x98, 0x99, 0x9a, 0x9b, 0x9c, 0x9d, 0x9e, 0x9f,
+			0xa0, 0xa1, 0xa2, 0xa3, 0xa4, 0xa5, 0xa6, 0xa7,
+			0xa8, 0xa9, 0xaa, 0xab, 0xac, 0xad, 0xae, 0xaf,
+			0xb0, 0xb1, 0xb2, 0xb3,
+		},
+		io.StringBytes("Sample #3"),
+		"bcf41eab8bb2d802f3d05caf7cb092ecf8d1a3aa",
+	},
+
+	// Test from Plan 9.
+	hmacTest {
+		NewMD5,
+		io.StringBytes("Jefe"),
+		io.StringBytes("what do ya want for nothing?"),
+		"750c783e6ab0b503eaa86e310a5db738",
+	}
+}
+
+func TestHMAC(t *testing.T) {
+	for i, tt := range hmacTests {
+		h := tt.hash(tt.key);
+		for j := 0; j < 2; j++ {
+			n, err := h.Write(tt.in);
+			if n != len(tt.in) || err != nil {
+				t.Errorf("test %d.%d: Write(%d) = %d, %v", i, j, len(tt.in), n, err);
+				continue;
+			}
+			sum := fmt.Sprintf("%x", h.Sum());
+			if sum != tt.out {
+				t.Errorf("test %d.%d: have %s want %s\n", i, j, sum, tt.out);
+			}
+
+			// Second iteration: make sure reset works.
+			h.Reset();
+		}
 	}
 }

src/lib/crypto/md5/md5_test.go

@@ -54,11 +54,14 @@ func TestGolden(t *testing.T) {
 	for i := 0; i < len(golden); i++ {
 		g := golden[i];
 		c := New();
-		io.WriteString(c, g.in);
-		s := fmt.Sprintf("%x", c.Sum());
-		if s != g.out {
-			t.Errorf("md5(%s) = %s want %s", g.in, s, g.out);
-			t.FailNow();
+		for j := 0; j < 2; j++ {
+			io.WriteString(c, g.in);
+			s := fmt.Sprintf("%x", c.Sum());
+			if s != g.out {
+				t.Errorf("md5[%d](%s) = %s want %s", j, g.in, s, g.out);
+				t.FailNow();
+			}
+			c.Reset();
 		}
 	}
 }

src/lib/crypto/sha1/sha1.go

@@ -37,6 +37,8 @@ func (d *digest) Reset() {
 	d.h[2] = _Init2;
 	d.h[3] = _Init3;
 	d.h[4] = _Init4;
+	d.nx = 0;
+	d.len = 0;
 }
 
 // New returns a Hash computing the SHA1 checksum.

src/lib/crypto/sha1/sha1_test.go

@@ -56,11 +56,14 @@ func TestGolden(t *testing.T) {
 	for i := 0; i < len(golden); i++ {
 		g := golden[i];
 		c := New();
-		io.WriteString(c, g.in);
-		s := fmt.Sprintf("%x", c.Sum());
-		if s != g.out {
-			t.Errorf("sha1(%s) = %s want %s", g.in, s, g.out);
-			t.FailNow();
+		for j := 0; j < 2; j++ {
+			io.WriteString(c, g.in);
+			s := fmt.Sprintf("%x", c.Sum());
+			if s != g.out {
+				t.Errorf("sha1[%d](%s) = %s want %s", j, g.in, s, g.out);
+				t.FailNow();
+			}
+			c.Reset();
 		}
 	}
 }