1 files changed, 24 insertions, 30 deletions

diff --git a/src/pkg/crypto/dsa/dsa.go b/src/pkg/crypto/dsa/dsa.go
index a5f96fe94..05766a2f1 100644
--- a/src/pkg/crypto/dsa/dsa.go
+++ b/src/pkg/crypto/dsa/dsa.go
@@ -2,13 +2,13 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// Package dsa implements the Digital Signature Algorithm, as defined in FIPS 186-3
+// Package dsa implements the Digital Signature Algorithm, as defined in FIPS 186-3.
 package dsa
 
 import (
-	"big"
+	"errors"
 	"io"
-	"os"
+	"math/big"
 )
 
 // Parameters represents the domain parameters for a key. These parameters can
@@ -29,17 +29,11 @@ type PrivateKey struct {
 	X *big.Int
 }
 
-type invalidPublicKeyError int
-
-func (invalidPublicKeyError) String() string {
-	return "crypto/dsa: invalid public key"
-}
-
-// InvalidPublicKeyError results when a public key is not usable by this code.
+// ErrInvalidPublicKey results when a public key is not usable by this code.
 // FIPS is quite strict about the format of DSA keys, but other code may be
 // less so. Thus, when using keys which may have been generated by other code,
 // this error must be handled.
-var InvalidPublicKeyError = invalidPublicKeyError(0)
+var ErrInvalidPublicKey = errors.New("crypto/dsa: invalid public key")
 
 // ParameterSizes is a enumeration of the acceptable bit lengths of the primes
 // in a set of DSA parameters. See FIPS 186-3, section 4.2.
@@ -58,7 +52,7 @@ const numMRTests = 64
 
 // GenerateParameters puts a random, valid set of DSA parameters into params.
 // This function takes many seconds, even on fast machines.
-func GenerateParameters(params *Parameters, rand io.Reader, sizes ParameterSizes) (err os.Error) {
+func GenerateParameters(params *Parameters, rand io.Reader, sizes ParameterSizes) (err error) {
 	// This function doesn't follow FIPS 186-3 exactly in that it doesn't
 	// use a verification seed to generate the primes. The verification
 	// seed doesn't appear to be exported or used by other code and
@@ -79,7 +73,7 @@ func GenerateParameters(params *Parameters, rand io.Reader, sizes ParameterSizes
 		L = 3072
 		N = 256
 	default:
-		return os.NewError("crypto/dsa: invalid ParameterSizes")
+		return errors.New("crypto/dsa: invalid ParameterSizes")
 	}
 
 	qBytes := make([]byte, N/8)
@@ -102,7 +96,7 @@ GeneratePrimes:
 		qBytes[0] |= 0x80
 		q.SetBytes(qBytes)
 
-		if !big.ProbablyPrime(q, numMRTests) {
+		if !q.ProbablyPrime(numMRTests) {
 			continue
 		}
 
@@ -123,7 +117,7 @@ GeneratePrimes:
 				continue
 			}
 
-			if !big.ProbablyPrime(p, numMRTests) {
+			if !p.ProbablyPrime(numMRTests) {
 				continue
 			}
 
@@ -156,9 +150,9 @@ GeneratePrimes:
 
 // GenerateKey generates a public&private key pair. The Parameters of the
 // PrivateKey must already be valid (see GenerateParameters).
-func GenerateKey(priv *PrivateKey, rand io.Reader) os.Error {
+func GenerateKey(priv *PrivateKey, rand io.Reader) error {
 	if priv.P == nil || priv.Q == nil || priv.G == nil {
-		return os.NewError("crypto/dsa: parameters not set up before generating key")
+		return errors.New("crypto/dsa: parameters not set up before generating key")
 	}
 
 	x := new(big.Int)
@@ -185,12 +179,16 @@ func GenerateKey(priv *PrivateKey, rand io.Reader) os.Error {
 // larger message) using the private key, priv. It returns the signature as a
 // pair of integers. The security of the private key depends on the entropy of
 // rand.
-func Sign(rand io.Reader, priv *PrivateKey, hash []byte) (r, s *big.Int, err os.Error) {
+//
+// Note that FIPS 186-3 section 4.6 specifies that the hash should be truncated
+// to the byte-length of the subgroup. This function does not perform that
+// truncation itself.
+func Sign(rand io.Reader, priv *PrivateKey, hash []byte) (r, s *big.Int, err error) {
 	// FIPS 186-3, section 4.6
 
 	n := priv.Q.BitLen()
 	if n&7 != 0 {
-		err = InvalidPublicKeyError
+		err = ErrInvalidPublicKey
 		return
 	}
 	n >>= 3
@@ -218,10 +216,7 @@ func Sign(rand io.Reader, priv *PrivateKey, hash []byte) (r, s *big.Int, err os.
 			continue
 		}
 
-		if n > len(hash) {
-			n = len(hash)
-		}
-		z := k.SetBytes(hash[:n])
+		z := k.SetBytes(hash)
 
 		s = new(big.Int).Mul(priv.X, r)
 		s.Add(s, z)
@@ -238,7 +233,11 @@ func Sign(rand io.Reader, priv *PrivateKey, hash []byte) (r, s *big.Int, err os.
 }
 
 // Verify verifies the signature in r, s of hash using the public key, pub. It
-// returns true iff the signature is valid.
+// reports whether the signature is valid.
+//
+// Note that FIPS 186-3 section 4.6 specifies that the hash should be truncated
+// to the byte-length of the subgroup. This function does not perform that
+// truncation itself.
 func Verify(pub *PublicKey, hash []byte, r, s *big.Int) bool {
 	// FIPS 186-3, section 4.7
 
@@ -255,12 +254,7 @@ func Verify(pub *PublicKey, hash []byte, r, s *big.Int) bool {
 	if n&7 != 0 {
 		return false
 	}
-	n >>= 3
-
-	if n > len(hash) {
-		n = len(hash)
-	}
-	z := new(big.Int).SetBytes(hash[:n])
+	z := new(big.Int).SetBytes(hash)
 
 	u1 := new(big.Int).Mul(z, w)
 	u1.Mod(u1, pub.Q)