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Introduce hash context to support pluggable SHA256 compression

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This is purely a mechanical change with no behavior change.

It introduces a secp256k1_hash_ctx struct inside secp256k1_context
and propagates it to all SHA256-related operations.

This sets up the ability to provide a hardware-optimized SHA256
compression function at runtime in a follow-up commit.
This commit is contained in:
furszy
2025-12-17 11:15:33 -05:00
parent 95e6815843
commit fdb6a91a5e
21 changed files with 313 additions and 238 deletions
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27
src/secp256k1.c
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@@ -60,6 +60,7 @@
* context_eq function. */
struct secp256k1_context_struct {
secp256k1_ecmult_gen_context ecmult_gen_ctx;
secp256k1_hash_ctx hash_ctx;
secp256k1_callback illegal_callback;
secp256k1_callback error_callback;
int declassify;
@@ -67,6 +68,7 @@ struct secp256k1_context_struct {
static const secp256k1_context secp256k1_context_static_ = {
{ 0 },
{ secp256k1_sha256_transform },
{ secp256k1_default_illegal_callback_fn, 0 },
{ secp256k1_default_error_callback_fn, 0 },
0
@@ -129,10 +131,11 @@ secp256k1_context* secp256k1_context_preallocated_create(void* prealloc, unsigne
ret = (secp256k1_context*)prealloc;
ret->illegal_callback = default_illegal_callback;
ret->error_callback = default_error_callback;
secp256k1_hash_ctx_init(&ret->hash_ctx);
/* Flags have been checked by secp256k1_context_preallocated_size. */
VERIFY_CHECK((flags & SECP256K1_FLAGS_TYPE_MASK) == SECP256K1_FLAGS_TYPE_CONTEXT);
secp256k1_ecmult_gen_context_build(&ret->ecmult_gen_ctx);
secp256k1_ecmult_gen_context_build(&ret->ecmult_gen_ctx, &ret->hash_ctx);
ret->declassify = !!(flags & SECP256K1_FLAGS_BIT_CONTEXT_DECLASSIFY);
return ret;
@@ -220,6 +223,10 @@ void secp256k1_context_set_error_callback(secp256k1_context* ctx, void (*fun)(co
ctx->error_callback.data = data;
}
static SECP256K1_INLINE const secp256k1_hash_ctx* secp256k1_get_hash_context(const secp256k1_context *ctx) {
return &ctx->hash_ctx;
}
static secp256k1_scratch_space* secp256k1_scratch_space_create(const secp256k1_context* ctx, size_t max_size) {
VERIFY_CHECK(ctx != NULL);
return secp256k1_scratch_create(&ctx->error_callback, max_size);
@@ -476,7 +483,7 @@ static SECP256K1_INLINE void buffer_append(unsigned char *buf, unsigned int *off
*offset += len;
}
static int nonce_function_rfc6979(unsigned char *nonce32, const unsigned char *msg32, const unsigned char *key32, const unsigned char *algo16, void *data, unsigned int counter) {
static int nonce_function_rfc6979_impl(const secp256k1_hash_ctx *hash_ctx, unsigned char *nonce32, const unsigned char *msg32, const unsigned char *key32, const unsigned char *algo16, void *data, unsigned int counter) {
unsigned char keydata[112];
unsigned int offset = 0;
secp256k1_rfc6979_hmac_sha256 rng;
@@ -501,9 +508,9 @@ static int nonce_function_rfc6979(unsigned char *nonce32, const unsigned char *m
if (algo16 != NULL) {
buffer_append(keydata, &offset, algo16, 16);
}
secp256k1_rfc6979_hmac_sha256_initialize(&rng, keydata, offset);
secp256k1_rfc6979_hmac_sha256_initialize(hash_ctx, &rng, keydata, offset);
for (i = 0; i <= counter; i++) {
secp256k1_rfc6979_hmac_sha256_generate(&rng, nonce32, 32);
secp256k1_rfc6979_hmac_sha256_generate(hash_ctx, &rng, nonce32, 32);
}
secp256k1_rfc6979_hmac_sha256_finalize(&rng);
@@ -512,6 +519,10 @@ static int nonce_function_rfc6979(unsigned char *nonce32, const unsigned char *m
return 1;
}
static int nonce_function_rfc6979(unsigned char *nonce32, const unsigned char *msg32, const unsigned char *key32, const unsigned char *algo16, void *data, unsigned int counter) {
return nonce_function_rfc6979_impl(secp256k1_get_hash_context(secp256k1_context_static), nonce32, msg32, key32, algo16, data, counter);
}
const secp256k1_nonce_function secp256k1_nonce_function_rfc6979 = nonce_function_rfc6979;
const secp256k1_nonce_function secp256k1_nonce_function_default = nonce_function_rfc6979;
@@ -757,7 +768,7 @@ int secp256k1_context_randomize(secp256k1_context* ctx, const unsigned char *see
ARG_CHECK(secp256k1_context_is_proper(ctx));
if (secp256k1_ecmult_gen_context_is_built(&ctx->ecmult_gen_ctx)) {
secp256k1_ecmult_gen_blind(&ctx->ecmult_gen_ctx, seed32);
secp256k1_ecmult_gen_blind(&ctx->ecmult_gen_ctx, secp256k1_get_hash_context(ctx), seed32);
}
return 1;
}
@@ -795,9 +806,9 @@ int secp256k1_tagged_sha256(const secp256k1_context* ctx, unsigned char *hash32,
ARG_CHECK(tag != NULL);
ARG_CHECK(msg != NULL);
secp256k1_sha256_initialize_tagged(&sha, tag, taglen);
secp256k1_sha256_write(&sha, msg, msglen);
secp256k1_sha256_finalize(&sha, hash32);
secp256k1_sha256_initialize_tagged(secp256k1_get_hash_context(ctx), &sha, tag, taglen);
secp256k1_sha256_write(secp256k1_get_hash_context(ctx), &sha, msg, msglen);
secp256k1_sha256_finalize(secp256k1_get_hash_context(ctx), &sha, hash32);
secp256k1_sha256_clear(&sha);
return 1;
}