crypto/x509: store names in signatureAlgorithmDetails.

There is already a table of signature algorithm details so the code
should use it for the name too. This avoids mismatches.

Change-Id: I0d4befbae721ec43db9f87cd93173ec12749e4c8
Reviewed-on: https://go-review.googlesource.com/57210
Run-TryBot: Adam Langley <agl@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>

src/crypto/x509/x509.go

@@ -194,27 +194,11 @@ func (algo SignatureAlgorithm) isRSAPSS() bool {
 	}
 }
 
-var signatureAlgoName = [...]string{
-	MD2WithRSA:       "MD2-RSA",
-	MD5WithRSA:       "MD5-RSA",
-	SHA1WithRSA:      "SHA1-RSA",
-	SHA256WithRSA:    "SHA256-RSA",
-	SHA384WithRSA:    "SHA384-RSA",
-	SHA512WithRSA:    "SHA512-RSA",
-	SHA256WithRSAPSS: "SHA256-RSAPSS",
-	SHA384WithRSAPSS: "SHA384-RSAPSS",
-	SHA512WithRSAPSS: "SHA512-RSAPSS",
-	DSAWithSHA1:      "DSA-SHA1",
-	DSAWithSHA256:    "DSA-SHA256",
-	ECDSAWithSHA1:    "ECDSA-SHA1",
-	ECDSAWithSHA256:  "ECDSA-SHA256",
-	ECDSAWithSHA384:  "ECDSA-SHA384",
-	ECDSAWithSHA512:  "ECDSA-SHA512",
-}
-
 func (algo SignatureAlgorithm) String() string {
-	if 0 < algo && int(algo) < len(signatureAlgoName) {
-		return signatureAlgoName[algo]
+	for _, details := range signatureAlgorithmDetails {
+		if details.algo == algo {
+			return details.name
+		}
 	}
 	return strconv.Itoa(int(algo))
 }
@@ -320,26 +304,27 @@ var (
 
 var signatureAlgorithmDetails = []struct {
 	algo       SignatureAlgorithm
+	name       string
 	oid        asn1.ObjectIdentifier
 	pubKeyAlgo PublicKeyAlgorithm
 	hash       crypto.Hash
 }{
-	{MD2WithRSA, oidSignatureMD2WithRSA, RSA, crypto.Hash(0) /* no value for MD2 */},
-	{MD5WithRSA, oidSignatureMD5WithRSA, RSA, crypto.MD5},
-	{SHA1WithRSA, oidSignatureSHA1WithRSA, RSA, crypto.SHA1},
-	{SHA1WithRSA, oidISOSignatureSHA1WithRSA, RSA, crypto.SHA1},
-	{SHA256WithRSA, oidSignatureSHA256WithRSA, RSA, crypto.SHA256},
-	{SHA384WithRSA, oidSignatureSHA384WithRSA, RSA, crypto.SHA384},
-	{SHA512WithRSA, oidSignatureSHA512WithRSA, RSA, crypto.SHA512},
-	{SHA256WithRSAPSS, oidSignatureRSAPSS, RSA, crypto.SHA256},
-	{SHA384WithRSAPSS, oidSignatureRSAPSS, RSA, crypto.SHA384},
-	{SHA512WithRSAPSS, oidSignatureRSAPSS, RSA, crypto.SHA512},
-	{DSAWithSHA1, oidSignatureDSAWithSHA1, DSA, crypto.SHA1},
-	{DSAWithSHA256, oidSignatureDSAWithSHA256, DSA, crypto.SHA256},
-	{ECDSAWithSHA1, oidSignatureECDSAWithSHA1, ECDSA, crypto.SHA1},
-	{ECDSAWithSHA256, oidSignatureECDSAWithSHA256, ECDSA, crypto.SHA256},
-	{ECDSAWithSHA384, oidSignatureECDSAWithSHA384, ECDSA, crypto.SHA384},
-	{ECDSAWithSHA512, oidSignatureECDSAWithSHA512, ECDSA, crypto.SHA512},
+	{MD2WithRSA, "MD2-RSA", oidSignatureMD2WithRSA, RSA, crypto.Hash(0) /* no value for MD2 */},
+	{MD5WithRSA, "MD5-RSA", oidSignatureMD5WithRSA, RSA, crypto.MD5},
+	{SHA1WithRSA, "SHA1-RSA", oidSignatureSHA1WithRSA, RSA, crypto.SHA1},
+	{SHA1WithRSA, "SHA1-RSA", oidISOSignatureSHA1WithRSA, RSA, crypto.SHA1},
+	{SHA256WithRSA, "SHA256-RSA", oidSignatureSHA256WithRSA, RSA, crypto.SHA256},
+	{SHA384WithRSA, "SHA384-RSA", oidSignatureSHA384WithRSA, RSA, crypto.SHA384},
+	{SHA512WithRSA, "SHA512-RSA", oidSignatureSHA512WithRSA, RSA, crypto.SHA512},
+	{SHA256WithRSAPSS, "SHA256-RSAPSS", oidSignatureRSAPSS, RSA, crypto.SHA256},
+	{SHA384WithRSAPSS, "SHA384-RSAPSS", oidSignatureRSAPSS, RSA, crypto.SHA384},
+	{SHA512WithRSAPSS, "SHA512-RSAPSS", oidSignatureRSAPSS, RSA, crypto.SHA512},
+	{DSAWithSHA1, "DSA-SHA1", oidSignatureDSAWithSHA1, DSA, crypto.SHA1},
+	{DSAWithSHA256, "DSA-SHA256", oidSignatureDSAWithSHA256, DSA, crypto.SHA256},
+	{ECDSAWithSHA1, "ECDSA-SHA1", oidSignatureECDSAWithSHA1, ECDSA, crypto.SHA1},
+	{ECDSAWithSHA256, "ECDSA-SHA256", oidSignatureECDSAWithSHA256, ECDSA, crypto.SHA256},
+	{ECDSAWithSHA384, "ECDSA-SHA384", oidSignatureECDSAWithSHA384, ECDSA, crypto.SHA384},
+	{ECDSAWithSHA512, "ECDSA-SHA512", oidSignatureECDSAWithSHA512, ECDSA, crypto.SHA512},
 }
 
 // pssParameters reflects the parameters in an AlgorithmIdentifier that