refactor to remove duplication

helper/tlsutil/config.go

@@ -148,38 +148,38 @@ func (c *Config) AppendCA(pool *x509.CertPool) error {
 	}
 
 	block, rest := pem.Decode(data)
-	if block == nil {
-		return fmt.Errorf("Failed to decode CA file from pem format")
+	if err := validateCertificate(block); err != nil {
+		return err
 	}
 
-	// Parse the certificate to ensure that it is properly formatted
-	if _, err := x509.ParseCertificates(block.Bytes); err != nil {
-		return fmt.Errorf("Failed to parse CA file: %v", err)
+	for len(rest) > 0 {
+		block, rest = pem.Decode(rest)
+		if err := validateCertificate(block); err != nil {
+			return err
+		}
+
+		if len(rest) == 0 {
+			break
+		}
 	}
 
 	if !pool.AppendCertsFromPEM(data) {
 		return fmt.Errorf("Failed to add any CA certificates")
 	}
 
-	for len(rest) > 0 {
-		block, rest = pem.Decode(rest)
-
-		if block == nil {
-			return fmt.Errorf("Failed to decode CA file from pem format")
-		}
-
-		// Parse the certificate to ensure that it is properly formatted
-		if _, err := x509.ParseCertificates(block.Bytes); err != nil {
-			return fmt.Errorf("Failed to parse CA file: %v", err)
-		}
+	return nil
+}
 
-		if !pool.AppendCertsFromPEM(data) {
-			return fmt.Errorf("Failed to add any CA certificates")
-		}
+// validateCertificate checks to ensure a certificate is valid. If it is not,
+// return a descriptive error of why the certificate is invalid.
+func validateCertificate(block *pem.Block) error {
+	if block == nil {
+		return fmt.Errorf("Failed to decode CA file from pem format")
+	}
 
-		if len(rest) == 0 {
-			break
-		}
+	// Parse the certificate to ensure that it is properly formatted
+	if _, err := x509.ParseCertificates(block.Bytes); err != nil {
+		return fmt.Errorf("Failed to parse CA file: %v", err)
 	}
 
 	return nil