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surjectionproof: fix malleability in surjection proof parsing

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This commit is contained in:
Andrew Poelstra
2019-06-03 21:50:40 +00:00
committed by Tim Ruffing
parent 41bc9ce129
commit 68d937fe11
2 changed files with 13 additions and 4 deletions
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9
src/modules/surjection/main_impl.h
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@@ -55,6 +55,15 @@ int secp256k1_surjectionproof_parse(const secp256k1_context* ctx, secp256k1_surj
return 0;
}
/* Check that the bitvector of used inputs is of the claimed
* length; i.e. the final byte has no "padding bits" set */
if (n_inputs % 8 != 0) {
const unsigned char padding_mask = (~0U) << (n_inputs % 8);
if ((input[2 + (n_inputs + 7) / 8 - 1] & padding_mask) != 0) {
return 0;
}
}
signature_len = 32 * (1 + secp256k1_count_bits_set(&input[2], (n_inputs + 7) / 8));
if (inputlen != 2 + (n_inputs + 7) / 8 + signature_len) {
return 0;