Make empty byte arrays pass CheckSignatureEncoding()

Makes it possible to compactly provide a delibrately invalid signature
for use with CHECK(MULTI)SIG. For instance with BIP19 if m != n invalid
signatures need to be provided in the scriptSig; prior to this change
those invalid signatures would need to be large DER-encoded signatures.

Note that we may want to further expand on this change in the future by
saying that only OP_0 is a "valid" invalid signature; BIP19 even with
this change is inherently malleable as the invalid signatures can be any
validly encoded DER signature.

1 files changed, 0 insertions, 4 deletions

diff --git a/src/test/multisig_tests.cpp b/src/test/multisig_tests.cpp
index 69d8522188..9501169943 100644
--- a/src/test/multisig_tests.cpp
+++ b/src/test/multisig_tests.cpp
@@ -116,10 +116,6 @@ BOOST_AUTO_TEST_CASE(multisig_verify)
         }
     }
     s.clear();
-    s << OP_0 << OP_0;
-    BOOST_CHECK(!VerifyScript(s, a_or_b, flags, SignatureChecker(txTo[1], 0), &err));
-    BOOST_CHECK_MESSAGE(err == SCRIPT_ERR_SIG_DER, ScriptErrorString(err));
-    s.clear();
     s << OP_0 << OP_1;
     BOOST_CHECK(!VerifyScript(s, a_or_b, flags, SignatureChecker(txTo[1], 0), &err));
     BOOST_CHECK_MESSAGE(err == SCRIPT_ERR_SIG_DER, ScriptErrorString(err));