Interm. BLD BREAK Pad short ECDSA signature

big.Int.Bytes() trims MSB zeroes, put them back in depending on
EC Field length

Change-Id: I87829c0babeafc49650f408355fa8212b49b62ff
Signed-off-by: Volodymyr Paprotski <vpaprots@ca.ibm.com>

bccsp/pkcs11/ecdsa.go

@@ -111,5 +111,5 @@ func (csp *impl) verifyECDSA(k ecdsaPublicKey, signature, digest []byte, opts bc
 		return false, fmt.Errorf("Invalid S. Must be smaller than half the order [%s][%s].", s, halfOrder)
 	}
 
-	return verifyECDSA(k.ski, digest, r, s)
+	return verifyECDSA(k.ski, digest, r, s, k.pub.Curve.Params().BitSize/8)
 }

bccsp/pkcs11/pkcs11.go

@@ -328,7 +328,7 @@ func signECDSA(ski []byte, msg []byte) (R, S *big.Int, err error) {
 	return R, S, nil
 }
 
-func verifyECDSA(ski []byte, msg []byte, R, S *big.Int) (valid bool, err error) {
+func verifyECDSA(ski []byte, msg []byte, R, S *big.Int, byteSize int) (valid bool, err error) {
 	p11lib := ctx
 	session := getSession()
 	defer returnSession(session)
@@ -340,7 +340,14 @@ func verifyECDSA(ski []byte, msg []byte, R, S *big.Int) (valid bool, err error)
 		return false, fmt.Errorf("Public key not found [%s]\n", err)
 	}
 
-	sig := append(R.Bytes(), S.Bytes()...)
+	r := R.Bytes()
+	s := S.Bytes()
+
+	// Pad front of R and S with Zeroes if needed
+	sig := make([]byte, 2*byteSize)
+	copy(sig[byteSize-len(r):byteSize], r)
+	copy(sig[2*byteSize-len(s):], s)
+
 	err = p11lib.VerifyInit(session, []*pkcs11.Mechanism{pkcs11.NewMechanism(pkcs11.CKM_ECDSA, nil)},
 		*publicKey)
 	if err != nil {

bccsp/pkcs11/pkcs11_test.go

@@ -63,7 +63,7 @@ func TestPKCS11ECKeySignVerify(t *testing.T) {
 		t.Fatal("Failed signing message [%s]", err)
 	}
 
-	pass, err := verifyECDSA(key, hash1, R, S)
+	pass, err := verifyECDSA(key, hash1, R, S, currentTestConfig.securityLevel/8)
 	if err != nil {
 		t.Fatal("Error verifying message 1 [%s]", err)
 	}
@@ -76,7 +76,7 @@ func TestPKCS11ECKeySignVerify(t *testing.T) {
 		t.Fatal("Signature should match with software verification!")
 	}
 
-	pass, err = verifyECDSA(key, hash2, R, S)
+	pass, err = verifyECDSA(key, hash2, R, S, currentTestConfig.securityLevel/8)
 	if err != nil {
 		t.Fatal("Error verifying message 2 [%s]", err)
 	}
@@ -129,7 +129,7 @@ func TestPKCS11ECKeyImportSignVerify(t *testing.T) {
 		t.Fatal("Failed signing message [%s]", err)
 	}
 
-	pass, err := verifyECDSA(ski, hash1, R, S)
+	pass, err := verifyECDSA(ski, hash1, R, S, currentTestConfig.securityLevel/8)
 	if err != nil {
 		t.Fatalf("Error verifying message 1 [%s]\n%s\n\n%s", err, hex.Dump(R.Bytes()), hex.Dump(S.Bytes()))
 	}
@@ -142,7 +142,7 @@ func TestPKCS11ECKeyImportSignVerify(t *testing.T) {
 		t.Fatal("Signature should match with software verification!")
 	}
 
-	pass, err = verifyECDSA(ski, hash2, R, S)
+	pass, err = verifyECDSA(ski, hash2, R, S, currentTestConfig.securityLevel/8)
 	if err != nil {
 		t.Fatal("Error verifying message 2 [%s]", err)
 	}
@@ -198,15 +198,15 @@ func TestPKCS11ECKeyExport(t *testing.T) {
 		t.Fatalf("Failed signing message [%s]", err)
 	}
 
-	pass, err := verifyECDSA(key2, hash1, R, S)
+	pass, err := verifyECDSA(key2, hash1, R, S, currentTestConfig.securityLevel/8)
 	if err != nil {
 		t.Fatalf("Error verifying message 1 [%s]", err)
 	}
 	if pass == false {
 		t.Fatal("Signature should match! [1]")
 	}
 
-	pass, err = verifyECDSA(key, hash1, R, S)
+	pass, err = verifyECDSA(key, hash1, R, S, currentTestConfig.securityLevel/8)
 	if err != nil {
 		t.Fatalf("Error verifying message 2 [%s]", err)
 	}
@@ -219,7 +219,7 @@ func TestPKCS11ECKeyExport(t *testing.T) {
 		t.Fatal("Signature should match with software verification!")
 	}
 
-	pass, err = verifyECDSA(key, hash2, R, S)
+	pass, err = verifyECDSA(key, hash2, R, S, currentTestConfig.securityLevel/8)
 	if err != nil {
 		t.Fatal("Error verifying message 3 [%s]", err)
 	}