// 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;
)
}
}
-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();
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();
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);
+}
// 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();
+ }
}
}