/**
* Take a signature and decrypt it.
*/
static bigint *ICACHE_FLASH_ATTR sig_verify(BI_CTX *ctx, const uint8_t *sig, int sig_len,
bigint *modulus, bigint *pub_exp)
{
int i, size;
bigint *decrypted_bi, *dat_bi;
bigint *bir = NULL;
uint8_t *block = (uint8_t *)os_malloc(sig_len);
/* decrypt */
dat_bi = bi_import(ctx, sig, sig_len);
ctx->mod_offset = BIGINT_M_OFFSET;
/* convert to a normal block */
decrypted_bi = bi_mod_power2(ctx, dat_bi, modulus, pub_exp);
bi_export(ctx, decrypted_bi, block, sig_len);
ctx->mod_offset = BIGINT_M_OFFSET;
i = 10; /* start at the first possible non-padded byte */
while (block[i++] && i < sig_len);
size = sig_len - i;
/* get only the bit we want */
if (size > 0)
{
int len;
const uint8_t *sig_ptr = get_signature(&block[i], &len);
if (sig_ptr)
{
bir = bi_import(ctx, sig_ptr, len);
}
}
/* save a few bytes of memory */
bi_clear_cache(ctx);
os_free(block);
return bir;
}
/**
* Take a signature and decrypt it.
**/
bigint *RSA_sign_verify(BI_CTX *ctx, const uint8_t *sig, int sig_len,
bigint *modulus, bigint *pub_exp)
{
uint8_t *block;
int i, size;
bigint *decrypted_bi, *dat_bi;
bigint *bir = NULL;
block = (uint8_t *)malloc(sig_len);
/* decrypt */
dat_bi = bi_import(ctx, sig, sig_len);
ctx->mod_offset = BIGINT_M_OFFSET;
/* convert to a normal block */
decrypted_bi = bi_mod_power2(ctx, dat_bi, modulus, pub_exp);
bi_export(ctx, decrypted_bi, block, sig_len);
ctx->mod_offset = BIGINT_M_OFFSET;
i = 10; /* start at the first possible non-padded byte */
while (block[i++] && i < sig_len);
size = sig_len - i;
/* get only the bit we want */
if (size > 0)
{
int len;
const uint8_t *sig_ptr = x509_get_signature(&block[i], &len);
if (sig_ptr)
{
bir = bi_import(ctx, sig_ptr, len);
}
}
free(block);
return bir;
}