1 files changed, 100 insertions, 0 deletions
diff --git a/libgo/go/crypto/hmac/hmac.go b/libgo/go/crypto/hmac/hmac.go
new file mode 100644
index 000000000..298fb2c06
--- /dev/null
+++ b/libgo/go/crypto/hmac/hmac.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.
+
+// 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 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"
+	"crypto/sha256"
+	"hash"
+	"os"
+)
+
+// 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
+)
+
+type hmac struct {
+	size         int
+	key, tmp     []byte
+	outer, inner hash.Hash
+}
+
+func (h *hmac) tmpPad(xor byte) {
+	for i, k := range h.key {
+		h.tmp[i] = xor ^ k
+	}
+	for i := len(h.key); i < padSize; i++ {
+		h.tmp[i] = xor
+	}
+}
+
+func (h *hmac) Sum() []byte {
+	sum := h.inner.Sum()
+	h.tmpPad(0x5c)
+	for i, b := range sum {
+		h.tmp[padSize+i] = b
+	}
+	h.outer.Reset()
+	h.outer.Write(h.tmp)
+	return h.outer.Sum()
+}
+
+func (h *hmac) Write(p []byte) (n int, err os.Error) {
+	return h.inner.Write(p)
+}
+
+func (h *hmac) Size() int { return h.size }
+
+func (h *hmac) Reset() {
+	h.inner.Reset()
+	h.tmpPad(0x36)
+	h.inner.Write(h.tmp[0:padSize])
+}
+
+// New returns a new HMAC hash using the given hash generator and key.
+func New(h func() hash.Hash, key []byte) hash.Hash {
+	hm := new(hmac)
+	hm.outer = h()
+	hm.inner = h()
+	hm.size = hm.inner.Size()
+	hm.tmp = make([]byte, padSize+hm.size)
+	if len(key) > padSize {
+		// If key is too big, hash it.
+		hm.outer.Write(key)
+		key = hm.outer.Sum()
+	}
+	hm.key = make([]byte, len(key))
+	copy(hm.key, key)
+	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) }
+
+// NewSHA256 returns a new HMAC-SHA256 hash using the given key.
+func NewSHA256(key []byte) hash.Hash { return New(sha256.New, key) }