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secp256k1
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Set precomputation table late and unset early. 

Set the global pointer to the precomputation table only after initializing
it completely, and unset it before doing any uninitialization.

This causes fail-fast behavior in case of race conditions between
initialization and operations using it.
This commit is contained in:
Pieter Wuille 2014-09-13 17:19:26 +02:00
parent 04e34d18c3
commit c259a7cbc0
1 changed files with 10 additions and 4 deletions
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14
src/ecmult_impl.h
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@ -94,8 +94,8 @@ static void secp256k1_ecmult_start(void) {
if (secp256k1_ecmult_consts != NULL)
return;
// Allocate the precomputation table.
secp256k1_ecmult_consts_t *ret = (secp256k1_ecmult_consts_t*)malloc(sizeof(secp256k1_ecmult_consts_t));
secp256k1_ecmult_consts = ret;
// get the generator
const secp256k1_ge_t *g = &secp256k1_ge_consts->g;
@ -109,14 +109,17 @@ static void secp256k1_ecmult_start(void) {
// precompute the tables with odd multiples
secp256k1_ecmult_table_precomp_ge(ret->pre_g, &gj, WINDOW_G);
secp256k1_ecmult_table_precomp_ge(ret->pre_g_128, &g_128j, WINDOW_G);
// Set the global pointer to the precomputation table.
secp256k1_ecmult_consts = ret;
}
static void secp256k1_ecmult_gen_start(void) {
if (secp256k1_ecmult_gen_consts != NULL)
return;
// Allocate the precomputation table.
secp256k1_ecmult_gen_consts_t *ret = (secp256k1_ecmult_gen_consts_t*)malloc(sizeof(secp256k1_ecmult_gen_consts_t));
secp256k1_ecmult_gen_consts = ret;
// get the generator
const secp256k1_ge_t *g = &secp256k1_ge_consts->g;
@ -169,6 +172,9 @@ static void secp256k1_ecmult_gen_start(void) {
ret->prec[j][k][i] = raw[k];
}
}
// Set the global pointer to the precomputation table.
secp256k1_ecmult_gen_consts = ret;
}
static void secp256k1_ecmult_stop(void) {
@ -176,8 +182,8 @@ static void secp256k1_ecmult_stop(void) {
return;
secp256k1_ecmult_consts_t *c = (secp256k1_ecmult_consts_t*)secp256k1_ecmult_consts;
free(c);
secp256k1_ecmult_consts = NULL;
free(c);
}
static void secp256k1_ecmult_gen_stop(void) {
@ -185,8 +191,8 @@ static void secp256k1_ecmult_gen_stop(void) {
return;
secp256k1_ecmult_gen_consts_t *c = (secp256k1_ecmult_gen_consts_t*)secp256k1_ecmult_gen_consts;
free(c);
secp256k1_ecmult_gen_consts = NULL;
free(c);
}
/** Convert a number to WNAF notation. The number becomes represented by sum(2^i * wnaf[i], i=0..bits),