From 8a8966b4ab5bc03e05f23d7c65fcbb567156c535 Mon Sep 17 00:00:00 2001
From: vyzo <vyzo@hackzen.org>
Date: Sun, 14 Oct 2018 11:59:28 +0300
Subject: [PATCH] fix public key extraction for abnormal ExtractPublicKey
 semantics

---
 sign.go | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/sign.go b/sign.go
index bd01c33..ee847ea 100644
--- a/sign.go
+++ b/sign.go
@@ -53,6 +53,9 @@ func messagePubKey(m *pb.Message) (crypto.PubKey, error) {
 		if err != nil {
 			return nil, fmt.Errorf("cannot extract signing key: %s", err.Error())
 		}
+		if pubk == nil {
+			return nil, fmt.Errorf("cannot extract signing key")
+		}
 	} else {
 		pubk, err = crypto.UnmarshalPublicKey(m.Key)
 		if err != nil {