LXR uboot/lib/fdt-libcrypto.c

   1// SPDX-License-Identifier: GPL-2.0+
   2/*
   3 * Copyright (c) 2020, Alexandru Gagniuc <mr.nuke.me@gmail.com>
   4 * Copyright (c) 2013, Google Inc.
   5 */
   6
   7#include <libfdt.h>
   8#include <u-boot/fdt-libcrypto.h>
   9
  10int fdt_add_bignum(void *blob, int noffset, const char *prop_name,
  11                   BIGNUM *num, int num_bits)
  12{
  13        int nwords = num_bits / 32;
  14        int size;
  15        uint32_t *buf, *ptr;
  16        BIGNUM *tmp, *big2, *big32, *big2_32;
  17        BN_CTX *ctx;
  18        int ret;
  19
  20        tmp = BN_new();
  21        big2 = BN_new();
  22        big32 = BN_new();
  23        big2_32 = BN_new();
  24
  25        /*
  26         * Note: This code assumes that all of the above succeed, or all fail.
  27         * In practice memory allocations generally do not fail (unless the
  28         * process is killed), so it does not seem worth handling each of these
  29         * as a separate case. Technicaly this could leak memory on failure,
  30         * but a) it won't happen in practice, and b) it doesn't matter as we
  31         * will immediately exit with a failure code.
  32         */
  33        if (!tmp || !big2 || !big32 || !big2_32) {
  34                fprintf(stderr, "Out of memory (bignum)\n");
  35                return -ENOMEM;
  36        }
  37        ctx = BN_CTX_new();
  38        if (!ctx) {
  39                fprintf(stderr, "Out of memory (bignum context)\n");
  40                return -ENOMEM;
  41        }
  42        BN_set_word(big2, 2L);
  43        BN_set_word(big32, 32L);
  44        BN_exp(big2_32, big2, big32, ctx); /* B = 2^32 */
  45
  46        size = nwords * sizeof(uint32_t);
  47        buf = malloc(size);
  48        if (!buf) {
  49                fprintf(stderr, "Out of memory (%d bytes)\n", size);
  50                return -ENOMEM;
  51        }
  52
  53        /* Write out modulus as big endian array of integers */
  54        for (ptr = buf + nwords - 1; ptr >= buf; ptr--) {
  55                BN_mod(tmp, num, big2_32, ctx); /* n = N mod B */
  56                *ptr = cpu_to_fdt32(BN_get_word(tmp));
  57                BN_rshift(num, num, 32); /*  N = N/B */
  58        }
  59
  60        /*
  61         * We try signing with successively increasing size values, so this
  62         * might fail several times
  63         */
  64        ret = fdt_setprop(blob, noffset, prop_name, buf, size);
  65        free(buf);
  66        BN_free(tmp);
  67        BN_free(big2);
  68        BN_free(big32);
  69        BN_free(big2_32);
  70
  71        return ret ? -FDT_ERR_NOSPACE : 0;
  72}
  73