simplify func

rsa.go

@@ -33,31 +33,26 @@ func SupportsSignatureRSAPKCS1v15(ch crypto.Hash) (supported bool) {
 	defer func() {
 		cachePKCS1Supported.Store(ch, supported)
 	}()
-	md := cryptoHashToMD(ch)
-	if ch != 0 && md == nil {
-		return false
+	var md C.GO_EVP_MD_PTR
+	if ch != 0 {
+		md = cryptoHashToMD(ch)
+		if md == nil {
+			return false
+		}
 	}
 	initTestRSAKey()
 	if testRSAPkey == nil {
-		// The test key is not available, so we cannot determine if PKCS1 signatures are supported.
-		// Use SupportsHash instead as a fallback.
-		return SupportsHash(ch)
+		return false
 	}
 	ctx := C.go_openssl_EVP_PKEY_CTX_new(testRSAPkey, nil)
 	if ctx == nil {
 		return false
 	}
 	defer C.go_openssl_EVP_PKEY_CTX_free(ctx)
-	if C.go_openssl_EVP_PKEY_sign_init(ctx) != 1 {
-		return false
-	}
-	if C.go_openssl_EVP_PKEY_CTX_ctrl(ctx, -1, -1, C.GO_EVP_PKEY_CTRL_MD, 0, unsafe.Pointer(md)) != 1 {
-		return false
-	}
-	if setRSAPAdding(ctx, C.GO_RSA_PKCS1_PADDING) != nil {
-		return false
-	}
-	return true
+
+	return C.go_openssl_EVP_PKEY_sign_init(ctx) == 1 &&
+		C.go_openssl_EVP_PKEY_CTX_ctrl(ctx, -1, -1, C.GO_EVP_PKEY_CTRL_MD, 0, unsafe.Pointer(md)) == 1 &&
+		setRSAPAdding(ctx, C.GO_RSA_PKCS1_PADDING) == nil
 }
 
 func GenerateKeyRSA(bits int) (N, E, D, P, Q, Dp, Dq, Qinv BigInt, err error) {