1 files changed, 105 insertions, 0 deletions
diff --git a/libgo/go/crypto/block/cmac.go b/libgo/go/crypto/block/cmac.go
new file mode 100644
index 000000000..b85cde72e
--- /dev/null
+++ b/libgo/go/crypto/block/cmac.go
@@ -0,0 +1,105 @@
+// 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.
+
+// CMAC message authentication code, defined in
+// NIST Special Publication SP 800-38B.
+
+package block
+
+import (
+	"hash"
+	"os"
+)
+
+const (
+	// minimal irreducible polynomial of degree b
+	r64  = 0x1b
+	r128 = 0x87
+)
+
+type cmac struct {
+	k1, k2, ci, digest []byte
+	p                  int // position in ci
+	c                  Cipher
+}
+
+// TODO(rsc): Should this return an error instead of panic?
+
+// NewCMAC returns a new instance of a CMAC message authentication code
+// digest using the given Cipher.
+func NewCMAC(c Cipher) hash.Hash {
+	var r byte
+	n := c.BlockSize()
+	switch n {
+	case 64 / 8:
+		r = r64
+	case 128 / 8:
+		r = r128
+	default:
+		panic("crypto/block: NewCMAC: invalid cipher block size")
+	}
+
+	d := new(cmac)
+	d.c = c
+	d.k1 = make([]byte, n)
+	d.k2 = make([]byte, n)
+	d.ci = make([]byte, n)
+	d.digest = make([]byte, n)
+
+	// Subkey generation, p. 7
+	c.Encrypt(d.k1, d.k1)
+	if shift1(d.k1, d.k1) != 0 {
+		d.k1[n-1] ^= r
+	}
+	if shift1(d.k2, d.k1) != 0 {
+		d.k2[n-1] ^= r
+	}
+
+	return d
+}
+
+// Reset clears the digest state, starting a new digest.
+func (d *cmac) Reset() {
+	for i := range d.ci {
+		d.ci[i] = 0
+	}
+	d.p = 0
+}
+
+// Write adds the given data to the digest state.
+func (d *cmac) Write(p []byte) (n int, err os.Error) {
+	// Xor input into ci.
+	for _, c := range p {
+		// If ci is full, encrypt and start over.
+		if d.p >= len(d.ci) {
+			d.c.Encrypt(d.ci, d.ci)
+			d.p = 0
+		}
+		d.ci[d.p] ^= c
+		d.p++
+	}
+	return len(p), nil
+}
+
+// Sum returns the CMAC digest, one cipher block in length,
+// of the data written with Write.
+func (d *cmac) Sum() []byte {
+	// Finish last block, mix in key, encrypt.
+	// Don't edit ci, in case caller wants
+	// to keep digesting after call to Sum.
+	k := d.k1
+	if d.p < len(d.digest) {
+		k = d.k2
+	}
+	for i := 0; i < len(d.ci); i++ {
+		d.digest[i] = d.ci[i] ^ k[i]
+	}
+	if d.p < len(d.digest) {
+		d.digest[d.p] ^= 0x80
+	}
+	d.c.Encrypt(d.digest, d.digest)
+	return d.digest
+}
+
+func (d *cmac) Size() int { return len(d.digest) }