Verify compressed argument in secp256k1_eckey_pubkey_serialize
#1642
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Due to similarity to the public API function `secp256k1_ec_pubkey_serialize`, public API flags like `SECP256K1_EC_COMPRESSED` are sometimes mistakingly passed to newly proposed code (this is currently the case for several modules in secp256k1-zkp, see BlockstreamResearch/secp256k1-zkp#300). which is currently not detected. To avoid this in the future, a VERIFY_CHECK is added to check that the `compressed` argument is either 0 or 1.
real-or-random
approved these changes
Dec 9, 2024
| @@ -35,6 +36,8 @@ static int secp256k1_eckey_pubkey_parse(secp256k1_ge *elem, const unsigned char | |||
| } | |||
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| static int secp256k1_eckey_pubkey_serialize(secp256k1_ge *elem, unsigned char *pub, size_t *size, int compressed) { | |||
| VERIFY_CHECK(compressed == 0 || compressed == 1); | |||
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In other places, we simply rely on C's int-as-bool convention, so I suggest adding a comment that explains why we enforce 0/1 in this case.
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Due to similarity to the public API function
secp256k1_ec_pubkey_serialize, public API flags likeSECP256K1_EC_COMPRESSEDare sometimes mistakingly passed tosecp256k1_eckey_pubkey_serializein newly proposed code (this is currently the case for several modules in secp256k1-zkp, see BlockstreamResearch/secp256k1-zkp#300), which is currently not detected. To avoid this in the future, a VERIFY_CHECK is added to check that thecompressedargument is either 0 or 1.