crypto: allocate less.

The code in hash functions themselves could write directly into the
output buffer for a savings of about 50ns. But it's a little ugly so I
wasted a copy.

R=bradfitz
CC=golang-dev
https://golang.org/cl/5440111

src/pkg/crypto/hmac/hmac.go

@@ -49,14 +49,13 @@ func (h *hmac) tmpPad(xor byte) {
 }
 
 func (h *hmac) Sum(in []byte) []byte {
-	sum := h.inner.Sum(nil)
+	origLen := len(in)
+	in = h.inner.Sum(in)
 	h.tmpPad(0x5c)
-	for i, b := range sum {
-		h.tmp[padSize+i] = b
-	}
+	copy(h.tmp[padSize:], in[origLen:])
 	h.outer.Reset()
 	h.outer.Write(h.tmp)
-	return h.outer.Sum(in)
+	return h.outer.Sum(in[:origLen])
 }
 
 func (h *hmac) Write(p []byte) (n int, err error) {

src/pkg/crypto/md5/md5.go

@@ -79,8 +79,7 @@ func (d *digest) Write(p []byte) (nn int, err error) {
 
 func (d0 *digest) Sum(in []byte) []byte {
 	// Make a copy of d0 so that caller can keep writing and summing.
-	d := new(digest)
-	*d = *d0
+	d := *d0
 
 	// Padding.  Add a 1 bit and 0 bits until 56 bytes mod 64.
 	len := d.len
@@ -103,11 +102,13 @@ func (d0 *digest) Sum(in []byte) []byte {
 		panic("d.nx != 0")
 	}
 
-	for _, s := range d.s {
-		in = append(in, byte(s>>0))
-		in = append(in, byte(s>>8))
-		in = append(in, byte(s>>16))
-		in = append(in, byte(s>>24))
+	var digest [Size]byte
+	for i, s := range d.s {
+		digest[i*4] = byte(s)
+		digest[i*4+1] = byte(s >> 8)
+		digest[i*4+2] = byte(s >> 16)
+		digest[i*4+3] = byte(s >> 24)
 	}
-	return in
+
+	return append(in, digest[:]...)
 }

src/pkg/crypto/openpgp/s2k/s2k.go

@@ -26,6 +26,7 @@ var zero [1]byte
 // 4880, section 3.7.1.2) using the given hash, input passphrase and salt.
 func Salted(out []byte, h hash.Hash, in []byte, salt []byte) {
 	done := 0
+	var digest []byte
 
 	for i := 0; done < len(out); i++ {
 		h.Reset()
@@ -34,7 +35,8 @@ func Salted(out []byte, h hash.Hash, in []byte, salt []byte) {
 		}
 		h.Write(salt)
 		h.Write(in)
-		n := copy(out[done:], h.Sum(nil))
+		digest = h.Sum(digest[:0])
+		n := copy(out[done:], digest)
 		done += n
 	}
 }
@@ -52,6 +54,7 @@ func Iterated(out []byte, h hash.Hash, in []byte, salt []byte, count int) {
 	}
 
 	done := 0
+	var digest []byte
 	for i := 0; done < len(out); i++ {
 		h.Reset()
 		for j := 0; j < i; j++ {
@@ -68,7 +71,8 @@ func Iterated(out []byte, h hash.Hash, in []byte, salt []byte, count int) {
 				written += len(combined)
 			}
 		}
-		n := copy(out[done:], h.Sum(nil))
+		digest = h.Sum(digest[:0])
+		n := copy(out[done:], digest)
 		done += n
 	}
 }

src/pkg/crypto/ripemd160/ripemd160.go

@@ -83,8 +83,7 @@ func (d *digest) Write(p []byte) (nn int, err error) {
 
 func (d0 *digest) Sum(in []byte) []byte {
 	// Make a copy of d0 so that caller can keep writing and summing.
-	d := new(digest)
-	*d = *d0
+	d := *d0
 
 	// Padding.  Add a 1 bit and 0 bits until 56 bytes mod 64.
 	tc := d.tc
@@ -107,11 +106,13 @@ func (d0 *digest) Sum(in []byte) []byte {
 		panic("d.nx != 0")
 	}
 
-	for _, s := range d.s {
-		in = append(in, byte(s))
-		in = append(in, byte(s>>8))
-		in = append(in, byte(s>>16))
-		in = append(in, byte(s>>24))
+	var digest [Size]byte
+	for i, s := range d.s {
+		digest[i*4] = byte(s)
+		digest[i*4+1] = byte(s >> 8)
+		digest[i*4+2] = byte(s >> 16)
+		digest[i*4+3] = byte(s >> 24)
 	}
-	return in
+
+	return append(in, digest[:]...)
 }

src/pkg/crypto/rsa/rsa.go

@@ -189,12 +189,13 @@ func incCounter(c *[4]byte) {
 // specified in PKCS#1 v2.1.
 func mgf1XOR(out []byte, hash hash.Hash, seed []byte) {
 	var counter [4]byte
+	var digest []byte
 
 	done := 0
 	for done < len(out) {
 		hash.Write(seed)
 		hash.Write(counter[0:4])
-		digest := hash.Sum(nil)
+		digest = hash.Sum(digest[:0])
 		hash.Reset()
 
 		for i := 0; i < len(digest) && done < len(out); i++ {

src/pkg/crypto/sha1/sha1.go

@@ -81,8 +81,7 @@ func (d *digest) Write(p []byte) (nn int, err error) {
 
 func (d0 *digest) Sum(in []byte) []byte {
 	// Make a copy of d0 so that caller can keep writing and summing.
-	d := new(digest)
-	*d = *d0
+	d := *d0
 
 	// Padding.  Add a 1 bit and 0 bits until 56 bytes mod 64.
 	len := d.len
@@ -105,11 +104,13 @@ func (d0 *digest) Sum(in []byte) []byte {
 		panic("d.nx != 0")
 	}
 
-	for _, s := range d.h {
-		in = append(in, byte(s>>24))
-		in = append(in, byte(s>>16))
-		in = append(in, byte(s>>8))
-		in = append(in, byte(s))
+	var digest [Size]byte
+	for i, s := range d.h {
+		digest[i*4] = byte(s >> 24)
+		digest[i*4+1] = byte(s >> 16)
+		digest[i*4+2] = byte(s >> 8)
+		digest[i*4+3] = byte(s)
 	}
-	return in
+
+	return append(in, digest[:]...)
 }

src/pkg/crypto/sha256/sha256.go

@@ -125,8 +125,7 @@ func (d *digest) Write(p []byte) (nn int, err error) {
 
 func (d0 *digest) Sum(in []byte) []byte {
 	// Make a copy of d0 so that caller can keep writing and summing.
-	d := new(digest)
-	*d = *d0
+	d := *d0
 
 	// Padding.  Add a 1 bit and 0 bits until 56 bytes mod 64.
 	len := d.len
@@ -150,14 +149,19 @@ func (d0 *digest) Sum(in []byte) []byte {
 	}
 
 	h := d.h[:]
+	size := Size
 	if d.is224 {
 		h = d.h[:7]
+		size = Size224
 	}
-	for _, s := range h {
-		in = append(in, byte(s>>24))
-		in = append(in, byte(s>>16))
-		in = append(in, byte(s>>8))
-		in = append(in, byte(s))
+
+	var digest [Size]byte
+	for i, s := range h {
+		digest[i*4] = byte(s >> 24)
+		digest[i*4+1] = byte(s >> 16)
+		digest[i*4+2] = byte(s >> 8)
+		digest[i*4+3] = byte(s)
 	}
-	return in
+
+	return append(in, digest[:size]...)
 }

src/pkg/crypto/sha512/sha512.go

@@ -150,18 +150,23 @@ func (d0 *digest) Sum(in []byte) []byte {
 	}
 
 	h := d.h[:]
+	size := Size
 	if d.is384 {
 		h = d.h[:6]
+		size = Size384
 	}
-	for _, s := range h {
-		in = append(in, byte(s>>56))
-		in = append(in, byte(s>>48))
-		in = append(in, byte(s>>40))
-		in = append(in, byte(s>>32))
-		in = append(in, byte(s>>24))
-		in = append(in, byte(s>>16))
-		in = append(in, byte(s>>8))
-		in = append(in, byte(s))
+
+	var digest [Size]byte
+	for i, s := range h {
+		digest[i*8] = byte(s >> 56)
+		digest[i*8+1] = byte(s >> 48)
+		digest[i*8+2] = byte(s >> 40)
+		digest[i*8+3] = byte(s >> 32)
+		digest[i*8+4] = byte(s >> 24)
+		digest[i*8+5] = byte(s >> 16)
+		digest[i*8+6] = byte(s >> 8)
+		digest[i*8+7] = byte(s)
 	}
-	return in
+
+	return append(in, digest[:size]...)
 }

src/pkg/crypto/tls/cipher_suites.go

@@ -96,7 +96,7 @@ func macSHA1(version uint16, key []byte) macFunction {
 
 type macFunction interface {
 	Size() int
-	MAC(seq, data []byte) []byte
+	MAC(digestBuf, seq, data []byte) []byte
 }
 
 // ssl30MAC implements the SSLv3 MAC function, as defined in
@@ -114,7 +114,7 @@ var ssl30Pad1 = [48]byte{0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0x36, 0
 
 var ssl30Pad2 = [48]byte{0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c, 0x5c}
 
-func (s ssl30MAC) MAC(seq, record []byte) []byte {
+func (s ssl30MAC) MAC(digestBuf, seq, record []byte) []byte {
 	padLength := 48
 	if s.h.Size() == 20 {
 		padLength = 40
@@ -127,13 +127,13 @@ func (s ssl30MAC) MAC(seq, record []byte) []byte {
 	s.h.Write(record[:1])
 	s.h.Write(record[3:5])
 	s.h.Write(record[recordHeaderLen:])
-	digest := s.h.Sum(nil)
+	digestBuf = s.h.Sum(digestBuf[:0])
 
 	s.h.Reset()
 	s.h.Write(s.key)
 	s.h.Write(ssl30Pad2[:padLength])
-	s.h.Write(digest)
-	return s.h.Sum(nil)
+	s.h.Write(digestBuf)
+	return s.h.Sum(digestBuf[:0])
 }
 
 // tls10MAC implements the TLS 1.0 MAC function. RFC 2246, section 6.2.3.
@@ -145,11 +145,11 @@ func (s tls10MAC) Size() int {
 	return s.h.Size()
 }
 
-func (s tls10MAC) MAC(seq, record []byte) []byte {
+func (s tls10MAC) MAC(digestBuf, seq, record []byte) []byte {
 	s.h.Reset()
 	s.h.Write(seq)
 	s.h.Write(record)
-	return s.h.Sum(nil)
+	return s.h.Sum(digestBuf[:0])
 }
 
 func rsaKA() keyAgreement {

src/pkg/crypto/tls/conn.go

@@ -118,6 +118,9 @@ type halfConn struct {
 
 	nextCipher interface{} // next encryption state
 	nextMac    macFunction // next MAC algorithm
+
+	// used to save allocating a new buffer for each MAC.
+	inDigestBuf, outDigestBuf []byte
 }
 
 // prepareCipherSpec sets the encryption and MAC states
@@ -280,12 +283,13 @@ func (hc *halfConn) decrypt(b *block) (bool, alert) {
 		b.data[4] = byte(n)
 		b.resize(recordHeaderLen + n)
 		remoteMAC := payload[n:]
-		localMAC := hc.mac.MAC(hc.seq[0:], b.data)
+		localMAC := hc.mac.MAC(hc.inDigestBuf, hc.seq[0:], b.data)
 		hc.incSeq()
 
 		if subtle.ConstantTimeCompare(localMAC, remoteMAC) != 1 || paddingGood != 255 {
 			return false, alertBadRecordMAC
 		}
+		hc.inDigestBuf = localMAC
 	}
 
 	return true, 0
@@ -312,12 +316,13 @@ func padToBlockSize(payload []byte, blockSize int) (prefix, finalBlock []byte) {
 func (hc *halfConn) encrypt(b *block) (bool, alert) {
 	// mac
 	if hc.mac != nil {
-		mac := hc.mac.MAC(hc.seq[0:], b.data)
+		mac := hc.mac.MAC(hc.outDigestBuf, hc.seq[0:], b.data)
 		hc.incSeq()
 
 		n := len(b.data)
 		b.resize(n + len(mac))
 		copy(b.data[n:], mac)
+		hc.outDigestBuf = mac
 	}
 
 	payload := b.data[recordHeaderLen:]

src/pkg/crypto/tls/handshake_client.go

@@ -231,10 +231,10 @@ func (c *Conn) clientHandshake() error {
 
 	if cert != nil {
 		certVerify := new(certificateVerifyMsg)
-		var digest [36]byte
-		copy(digest[0:16], finishedHash.serverMD5.Sum(nil))
-		copy(digest[16:36], finishedHash.serverSHA1.Sum(nil))
-		signed, err := rsa.SignPKCS1v15(c.config.rand(), c.config.Certificates[0].PrivateKey, crypto.MD5SHA1, digest[0:])
+		digest := make([]byte, 0, 36)
+		digest = finishedHash.serverMD5.Sum(digest)
+		digest = finishedHash.serverSHA1.Sum(digest)
+		signed, err := rsa.SignPKCS1v15(c.config.rand(), c.config.Certificates[0].PrivateKey, crypto.MD5SHA1, digest)
 		if err != nil {
 			return c.sendAlert(alertInternalError)
 		}

src/pkg/crypto/tls/handshake_server.go

@@ -234,9 +234,9 @@ FindCipherSuite:
 			return c.sendAlert(alertUnexpectedMessage)
 		}
 
-		digest := make([]byte, 36)
-		copy(digest[0:16], finishedHash.serverMD5.Sum(nil))
-		copy(digest[16:36], finishedHash.serverSHA1.Sum(nil))
+		digest := make([]byte, 0, 36)
+		digest = finishedHash.serverMD5.Sum(digest)
+		digest = finishedHash.serverSHA1.Sum(digest)
 		err = rsa.VerifyPKCS1v15(pub, crypto.MD5SHA1, digest, certVerify.signature)
 		if err != nil {
 			c.sendAlert(alertBadCertificate)