Freeze catalog signature vectors (T-614)

core/catalog/parser.go

@@ -2,7 +2,6 @@ package catalog
 
 import (
 	"bytes"
-	"encoding/base64"
 	"encoding/hex"
 	"encoding/json"
 	"errors"
@@ -231,12 +230,9 @@ func validatePackage(architecture Architecture, publishedPackage Package) error
 }
 
 func validateSignature(value string) error {
-	signature, err := base64.StdEncoding.Strict().DecodeString(value)
+	_, err := decodeCanonicalSignature(value)
 	if err != nil {
-		return fmt.Errorf("must be strict Base64: %v", err)
-	}
-	if len(signature) != 64 {
-		return fmt.Errorf("must decode to 64 bytes")
+		return fmt.Errorf("must be canonical padded Base64 for 64 bytes: %v", err)
 	}
 	return nil
 }