c281bb6837
5fa81e239atest: add valid tx test with minimum-sized ECDSA signature (8 bytes DER-encoded) (Sebastian Falbesoner) Pull request description: Currently in our tests, all ECDSA signatures passing verification have sizes of 69 bytes and above (that's the DER-encoded size, i.e. counted without the sighash flag byte) [1]. This PR adds test coverage for the minimum-sized valid case of 8 bytes, by taking an interesting testnet transaction that I stumbled upon: https://mempool.space/testnet/tx/c6c232a36395fa338da458b86ff1327395a9afc28c5d2daa4273e410089fd433 Note that this is a very obscure construction that only works because the public key used isn't contained in the locking script, but calculated and provided later at spending time (see https://bitcointalk.org/index.php?topic=1729534.msg17309060#msg17309060 for an explainer), to match the message (sighash) and picked signature. So this doesn't represent a use-case that really makes sense in practice, but it can still appear in a block (not in mempool though, due to `SCRIPT_VERIFY_CONST_SCRIPTCODE`), and having test-coverage seems useful. Can be tested with same patch below (tests crash with the condition `>= 9`, but pass with `>= 8`). [1] this can be verified by applying the following patch and running the tests: ```diff diff --git a/src/pubkey.cpp b/src/pubkey.cpp index a4ca9a170a..bee0caa603 100644 --- a/src/pubkey.cpp +++ b/src/pubkey.cpp @@ -288,7 +288,9 @@ bool CPubKey::Verify(const uint256 &hash, const std::vector<unsigned char>& vchS /* libsecp256k1's ECDSA verification requires lower-S signatures, which have * not historically been enforced in Bitcoin, so normalize them first. */ secp256k1_ecdsa_signature_normalize(secp256k1_context_static, &sig, &sig); - return secp256k1_ecdsa_verify(secp256k1_context_static, &sig, hash.begin(), &pubkey); + bool ret = secp256k1_ecdsa_verify(secp256k1_context_static, &sig, hash.begin(), &pubkey); + if (ret) assert(vchSig.size() >= 69); + return ret; } ``` ACKs for top commit: ajtowns: ACK5fa81e239algtm fjahr: tACK5fa81e239areal-or-random: utACK5fa81e239ainteresting case Tree-SHA512: d1f0612fdb71c9238ca0420f574f6f246e60dbd11970b23f21d082c759a89ff98a13b12a1f6266f14f20539ec437b7ab79322082278da32984ddfee2d8893356
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