frost/secp256k1-zkp
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Use secp256k1_memclear() to clear stack memory instead of memset()

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All of the invocations of secp256k1_memclear() operate on stack
memory and happen after the function is done with the memory object.
This commit replaces existing memset() invocations and also adds
secp256k1_memclear() to code locations where clearing was missing;
there is no guarantee that this commit covers all code locations
where clearing is necessary.

Co-Authored-By: isle2983 <isle2983@yahoo.com>
This commit is contained in:
Tim Ruffing
2019-06-08 13:54:14 +02:00
committed by Sebastian Falbesoner
parent e3497bbf00
commit 9bb368d146
8 changed files with 23 additions and 21 deletions
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8
src/ecmult_gen_impl.h
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@@ -277,8 +277,8 @@ static void secp256k1_ecmult_gen(const secp256k1_ecmult_gen_context *ctx, secp25
/* Cleanup. */
secp256k1_fe_clear(&neg);
secp256k1_ge_clear(&add);
memset(&adds, 0, sizeof(adds));
memset(&recoded, 0, sizeof(recoded));
secp256k1_memclear(&adds, sizeof(adds));
secp256k1_memclear(&recoded, sizeof(recoded));
}
/* Setup blinding values for secp256k1_ecmult_gen. */
@@ -310,7 +310,7 @@ static void secp256k1_ecmult_gen_blind(secp256k1_ecmult_gen_context *ctx, const
VERIFY_CHECK(seed32 != NULL);
memcpy(keydata + 32, seed32, 32);
secp256k1_rfc6979_hmac_sha256_initialize(&rng, keydata, 64);
memset(keydata, 0, sizeof(keydata));
secp256k1_memclear(keydata, sizeof(keydata));
/* Compute projective blinding factor (cannot be 0). */
secp256k1_rfc6979_hmac_sha256_generate(&rng, nonce32, 32);
@@ -325,13 +325,13 @@ static void secp256k1_ecmult_gen_blind(secp256k1_ecmult_gen_context *ctx, const
* which secp256k1_gej_add_ge cannot handle. */
secp256k1_scalar_cmov(&b, &secp256k1_scalar_one, secp256k1_scalar_is_zero(&b));
secp256k1_rfc6979_hmac_sha256_finalize(&rng);
memset(nonce32, 0, 32);
secp256k1_ecmult_gen(ctx, &gb, &b);
secp256k1_scalar_negate(&b, &b);
secp256k1_scalar_add(&ctx->scalar_offset, &b, &diff);
secp256k1_ge_set_gej(&ctx->ge_offset, &gb);
/* Clean up. */
secp256k1_memclear(nonce32, sizeof(nonce32));
secp256k1_scalar_clear(&b);
secp256k1_gej_clear(&gb);
secp256k1_fe_clear(&f);