Manually update buildah to v1.13.1

Should help with #791.

Signed-off-by: Miloslav Trmač <mitr@redhat.com>

vendor/golang.org/x/crypto/openpgp/packet/encrypted_key.go

@@ -5,6 +5,7 @@
 package packet
 
 import (
+	"crypto"
 	"crypto/rsa"
 	"encoding/binary"
 	"io"
@@ -78,8 +79,9 @@ func (e *EncryptedKey) Decrypt(priv *PrivateKey, config *Config) error {
 	// padding oracle attacks.
 	switch priv.PubKeyAlgo {
 	case PubKeyAlgoRSA, PubKeyAlgoRSAEncryptOnly:
-		k := priv.PrivateKey.(*rsa.PrivateKey)
-		b, err = rsa.DecryptPKCS1v15(config.Random(), k, padToKeySize(&k.PublicKey, e.encryptedMPI1.bytes))
+		// Supports both *rsa.PrivateKey and crypto.Decrypter
+		k := priv.PrivateKey.(crypto.Decrypter)
+		b, err = k.Decrypt(config.Random(), padToKeySize(k.Public().(*rsa.PublicKey), e.encryptedMPI1.bytes), nil)
 	case PubKeyAlgoElGamal:
 		c1 := new(big.Int).SetBytes(e.encryptedMPI1.bytes)
 		c2 := new(big.Int).SetBytes(e.encryptedMPI2.bytes)

vendor/golang.org/x/crypto/openpgp/packet/private_key.go

@@ -31,7 +31,7 @@ type PrivateKey struct {
 	encryptedData []byte
 	cipher        CipherFunction
 	s2k           func(out, in []byte)
-	PrivateKey    interface{} // An *{rsa|dsa|ecdsa}.PrivateKey or a crypto.Signer.
+	PrivateKey    interface{} // An *{rsa|dsa|ecdsa}.PrivateKey or crypto.Signer/crypto.Decrypter (Decryptor RSA only).
 	sha1Checksum  bool
 	iv            []byte
 }