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// SPDX-License-Identifier: GPL-2.0+
/*
* Copyright (c) 2020, Alexandru Gagniuc <mr.nuke.me@gmail.com>
* Copyright (c) 2013, Google Inc.
*/
#include <libfdt.h>
#include <u-boot/fdt-libcrypto.h>
int fdt_add_bignum(void *blob, int noffset, const char *prop_name,
BIGNUM *num, int num_bits)
{
int nwords = num_bits / 32;
int size;
uint32_t *buf, *ptr;
BIGNUM *tmp, *big2, *big32, *big2_32;
BN_CTX *ctx;
int ret;
tmp = BN_new();
big2 = BN_new();
big32 = BN_new();
big2_32 = BN_new();
/*
* Note: This code assumes that all of the above succeed, or all fail.
* In practice memory allocations generally do not fail (unless the
* process is killed), so it does not seem worth handling each of these
* as a separate case. Technicaly this could leak memory on failure,
* but a) it won't happen in practice, and b) it doesn't matter as we
* will immediately exit with a failure code.
*/
if (!tmp || !big2 || !big32 || !big2_32) {
fprintf(stderr, "Out of memory (bignum)\n");
return -ENOMEM;
}
ctx = BN_CTX_new();
if (!ctx) {
fprintf(stderr, "Out of memory (bignum context)\n");
return -ENOMEM;
}
BN_set_word(big2, 2L);
BN_set_word(big32, 32L);
BN_exp(big2_32, big2, big32, ctx); /* B = 2^32 */
size = nwords * sizeof(uint32_t);
buf = malloc(size);
if (!buf) {
fprintf(stderr, "Out of memory (%d bytes)\n", size);
return -ENOMEM;
}
/* Write out modulus as big endian array of integers */
for (ptr = buf + nwords - 1; ptr >= buf; ptr--) {
BN_mod(tmp, num, big2_32, ctx); /* n = N mod B */
*ptr = cpu_to_fdt32(BN_get_word(tmp));
BN_rshift(num, num, 32); /* N = N/B */
}
/*
* We try signing with successively increasing size values, so this
* might fail several times
*/
ret = fdt_setprop(blob, noffset, prop_name, buf, size);
free(buf);
BN_free(tmp);
BN_free(big2);
BN_free(big32);
BN_free(big2_32);
return ret ? -FDT_ERR_NOSPACE : 0;
}
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