Help debugging a bitcoin PHP extension (wrapper for bitcoin/secp256k1)

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA512 Hi all, I'm not sure of the best place to ask, but I am wondering if anyone could look over an extension I am working on, a wrapper for a small C library used to do of the cryptographic operations in bitcoin. I currently have all but two of the functions written and mostly working - with tonnes of positive tests - but it seems there is a segmentation fault in one of the functions. I think the problem in how I'm dealing with setting return values to the reference of an argument. It's quite a small extension and it hasn't taken a lot of effort to bring it this far, but I've stumbled for quite a bit on this. I know more experienced eyes could root out the problems quicker than mine. The repo for this is here: https://github.com/afk11/secp256k1-php I'd love more eyes to go over it as it blows the alternatives out of the water - an ECDSA implementation in pure PHP is quite slow. This is specialized to bitcoins elliptic curve, it's safer than reimplementing the wheel, and is insanely fast! Here is the function which SEGFAULTS, for those short on time (FYI I run php 5.6) PHP_FUNCTION(secp256k1_ec_pubkey_decompress) { secp256k1_start(SECP256K1_START_SIGN); // We are taking a pubkey, and it's length, and decompressing it (33 or 65 bytes -> 65 bytes) // updating both of these zvals at the end zval *pubkey, *pubkeylen; unsigned char* newpubkey; int newpubkeylen; int result; // From documentation it seems I can only mess with zvals when setting by reference? if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "zz", &pubkey, &pubkeylen) == FAILURE) { return; } // Initialize an unsigned char* with our pubkey newpubkey = Z_STRVAL_P(pubkey); newpubkeylen = Z_LVAL_P(pubkeylen); result = secp256k1_ec_pubkey_decompress(newpubkey, &newpubkeylen); if (result == 1) { newpubkey[newpubkeylen] = 0U; // Great, it worked, set pubkey and pubkeylen to the new values ZVAL_STRINGL(pubkey, newpubkey, newpubkeylen, 0); ZVAL_LONG(pubkeylen, newpubkeylen); } else { efree(newpubkey); } // Done, return the result. RETURN_LONG(result); } Not sure what it could be, the documentation I've found online often contains macros not found in PHP5.6, so it's hard to know what exactly I would be doing. For reference, the end libraries header is here: https://github.com/bitcoin/secp256k1/tree/master/include/secp256k1.h All the best, - -- Thomas Kerin - ------------------------- My PGP key can be found here <http://pgp.mit.edu/pks/lookup?op=get&search=0x3F0D2F83A2966155> -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iQJ8BAEBCgBmBQJVCwVZXxSAAAAAAC4AKGlzc3Vlci1mcHJAbm90YXRpb25zLm9w ZW5wZ3AuZmlmdGhob3JzZW1hbi5uZXQ2MzI1MzM4QjJGOTU5OEUzREMzQzc0MzAz RjBEMkY4M0EyOTY2MTU1AAoJED8NL4OilmFVmzUP/jGeLvg+/Q35czpxYY/MTBFI +cdqOCtMx5cIhI5X3kKUYZOnwEIn9fuiDM+TXmLzwit392YfHC2QZts3F/q25f/P 6IdfGgNNwWbu4JfKPe8MDIrQXVE8wbt9CQ5CvLCtPP/mK/uPuObmOu4KdhJHgYJy eYkuxysodzHrwJTrR5oE/jBUPKP3ndVI4/r3fQm6snXM7sI2p4P7KkvcgP+NqivC 7HTVn4abGU1AnPzAobAG7WuABfKduWoA1ZNmstISC8KfRYnc50CstSi4r7B32jsK uykBr0dfoVITpwrA2cAKpS/rmO2vN8O+aABigFy5Vbg4v3LJVF3ZOOLduIPvtcPO JPxHEDIphnHBvphxAm8vaQII1R6Fjyq0RdQNEmQbTocFcCJcINwV+WeQONgg1+/d PKYpD7FZF9j+pVo/MAybsLwdwUDxYkvDTmlx+a8MIElM2guCtABdxqOuewq3ZfQ8 865eNKR/CaZ3AmTwuvRjCxOzOguGG/vmJxa/xyiuGuoYvqDBVlW9YsiEDqk7kW1e XjEivFb1Bn9BxjAt4WK7aiUN6T7jLpRDfsVSWo3BEkVBaSXeAg5OCA4g/9FyJa1Y foNBKP3psdmK9FcNUSSMITvz7ovssa6FKyr7RrINqTTurZBumZnndKXFwPCYiHmi zLwodvh12Jm7ltp4UHt5 =oJjR -----END PGP SIGNATURE-----