| /*********************************************************************** | |
| * Copyright (c) 2015 Pieter Wuille * | |
| * Distributed under the MIT software license, see the accompanying * | |
| * file COPYING or https://www.opensource.org/licenses/mit-license.php.* | |
| ***********************************************************************/ | |
| | |
| #include <string.h> | |
| | |
| #include "lax_der_parsing.h" | |
| | |
| int ecdsa_signature_parse_der_lax(const secp256k1_context* ctx, secp256k1_ecdsa_signature* sig, const unsigned char *input, size_t inputlen) { | |
| size_t rpos, rlen, spos, slen; | |
| size_t pos = 0; | |
| size_t lenbyte; | |
| unsigned char tmpsig[64] = {0}; | |
| int overflow = 0; | |
| | |
| /* Hack to initialize sig with a correctly-parsed but invalid signature. */ | |
| secp256k1_ecdsa_signature_parse_compact(ctx, sig, tmpsig); | |
| | |
| /* Sequence tag byte */ | |
| if (pos == inputlen || input[pos] != 0x30) { | |
| return 0; | |
| } | |
| pos++; | |
| | |
| /* Sequence length bytes */ | |
| if (pos == inputlen) { | |
| return 0; | |
| } | |
| lenbyte = input[pos++]; | |
| if (lenbyte & 0x80) { | |
| lenbyte -= 0x80; | |
| if (lenbyte > inputlen - pos) { | |
| return 0; | |
| } | |
| pos += lenbyte; | |
| } | |
| | |
| /* Integer tag byte for R */ | |
| if (pos == inputlen || input[pos] != 0x02) { | |
| return 0; | |
| } | |
| pos++; | |
| | |
| /* Integer length for R */ | |
| if (pos == inputlen) { | |
| return 0; | |
| } | |
| lenbyte = input[pos++]; | |
| if (lenbyte & 0x80) { | |
| lenbyte -= 0x80; | |
| if (lenbyte > inputlen - pos) { | |
| return 0; | |
| } | |
| while (lenbyte > 0 && input[pos] == 0) { | |
| pos++; | |
| lenbyte--; | |
| } | |
| if (lenbyte >= sizeof(size_t)) { | |
| return 0; | |
| } | |
| rlen = 0; | |
| while (lenbyte > 0) { | |
| rlen = (rlen << 8) + input[pos]; | |
| pos++; | |
| lenbyte--; | |
| } | |
| } else { | |
| rlen = lenbyte; | |
| } | |
| if (rlen > inputlen - pos) { | |
| return 0; | |
| } | |
| rpos = pos; | |
| pos += rlen; | |
| | |
| /* Integer tag byte for S */ | |
| if (pos == inputlen || input[pos] != 0x02) { | |
| return 0; | |
| } | |
| pos++; | |
| | |
| /* Integer length for S */ | |
| if (pos == inputlen) { | |
| return 0; | |
| } | |
| lenbyte = input[pos++]; | |
| if (lenbyte & 0x80) { | |
| lenbyte -= 0x80; | |
| if (lenbyte > inputlen - pos) { | |
| return 0; | |
| } | |
| while (lenbyte > 0 && input[pos] == 0) { | |
| pos++; | |
| lenbyte--; | |
| } | |
| if (lenbyte >= sizeof(size_t)) { | |
| return 0; | |
| } | |
| slen = 0; | |
| while (lenbyte > 0) { | |
| slen = (slen << 8) + input[pos]; | |
| pos++; | |
| lenbyte--; | |
| } | |
| } else { | |
| slen = lenbyte; | |
| } | |
| if (slen > inputlen - pos) { | |
| return 0; | |
| } | |
| spos = pos; | |
| | |
| /* Ignore leading zeroes in R */ | |
| while (rlen > 0 && input[rpos] == 0) { | |
| rlen--; | |
| rpos++; | |
| } | |
| /* Copy R value */ | |
| if (rlen > 32) { | |
| overflow = 1; | |
| } else if (rlen) { | |
| memcpy(tmpsig + 32 - rlen, input + rpos, rlen); | |
| } | |
| | |
| /* Ignore leading zeroes in S */ | |
| while (slen > 0 && input[spos] == 0) { | |
| slen--; | |
| spos++; | |
| } | |
| /* Copy S value */ | |
| if (slen > 32) { | |
| overflow = 1; | |
| } else if (slen) { | |
| memcpy(tmpsig + 64 - slen, input + spos, slen); | |
| } | |
| | |
| if (!overflow) { | |
| overflow = !secp256k1_ecdsa_signature_parse_compact(ctx, sig, tmpsig); | |
| } | |
| if (overflow) { | |
| memset(tmpsig, 0, 64); | |
| secp256k1_ecdsa_signature_parse_compact(ctx, sig, tmpsig); | |
| } | |
| return 1; | |
| } | |