Do not accept EC signatures when the public point is invalid

Force g*x+p*y to the point at infinity if g or p is not a valid point.

This does not seem to be a security issue since if you can control the
public point you can just use a regular key and sign whatever you like.
Still, it's odd to accept anything here, and easy to prevent it.

Found by CryptoFuzz reported offline by @guidovranken

1 files changed, 3 insertions, 1 deletions

diff --git a/src/tests/test_pubkey.cpp b/src/tests/test_pubkey.cpp
index 3e3001a86..03f57c922 100644
--- a/src/tests/test_pubkey.cpp
+++ b/src/tests/test_pubkey.cpp
@@ -237,7 +237,9 @@ PK_Signature_Verification_Test::run_one_test(const std::string& pad_hdr, const V
                   }
                }
             else
-               result.test_eq("incorrect signature invalid", verified, false);
+               {
+               result.confirm("incorrect signature is rejected", verified == false);
+               }
             }
          catch(std::exception& e)
             {