Make empty byte arrays pass CheckSignatureEncoding() #5627

1. 
   petertodd commented at 11:01 AM on January 9, 2015: contributor

   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.

   CC: @sipa

2. 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.

   2fa9a8ec86
3. petertodd force-pushed on Jan 9, 2015
4. in src/test/multisig_tests.cpp:None in 2fa9a8ec86

    115 | @@ -116,10 +116,6 @@ BOOST_AUTO_TEST_CASE(multisig_verify)
    116 |          }
    117 |      }
    118 |      s.clear();
    119 | -    s << OP_0 << OP_0;
    120 | -    BOOST_CHECK(!VerifyScript(s, a_or_b, flags, SignatureChecker(txTo[1], 0), &err));
    121 | -    BOOST_CHECK_MESSAGE(err == SCRIPT_ERR_SIG_DER, ScriptErrorString(err));
    122 | -    s.clear();
   

   ---

   ---

   

   petertodd commented at 11:07 AM on January 9, 2015:

   I'm not 100% clear on why this code was duplicated; the next lines are identical but with "OP_0 << OP_1" rather than "OP_0 << OP_0". I believe this was just exercising different ways of failing the DER encoding, so I removed the way that is now valid.

5. 
   petertodd commented at 11:08 AM on January 9, 2015: contributor

   See also the corresponding pull-req to BIP62: https://github.com/bitcoin/bips/pull/132

6. laanwj added the label Validation on Jan 9, 2015
7. 
   sipa commented at 11:48 PM on January 9, 2015: member

   ACK

8. 
   gmaxwell commented at 3:20 PM on January 20, 2015: contributor

   ACK

9. laanwj merged this on Jan 26, 2015
10. laanwj closed this on Jan 26, 2015

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11. laanwj referenced this in commit b01a435c34 on Jan 26, 2015
12. laanwj referenced this in commit b24ff47c64 on Jan 26, 2015
13. laanwj added this to the milestone 0.10.0 on Jan 26, 2015
14. 
    laanwj commented at 11:11 AM on January 26, 2015: member

    backported into 0.10 as b24ff47

15. reddink referenced this in commit 6cb18eb4c7 on May 27, 2020
16. MarcoFalke locked this on Sep 8, 2021

Milestone
0.10.0