lib/rsa/rsa-sign.c

   1 /*
   2  * Copyright (c) 2013, Google Inc.
   3  *
   4  * SPDX-License-Identifier:     GPL-2.0+
   5  */
   6
   7 #include "mkimage.h"
   8 #include <stdio.h>
   9 #include <string.h>
  10 #include <image.h>
  11 #include <time.h>
  12 #include <openssl/rsa.h>
  13 #include <openssl/pem.h>
  14 #include <openssl/err.h>
  15 #include <openssl/ssl.h>
  16 #include <openssl/evp.h>
  17
  18 #if OPENSSL_VERSION_NUMBER >= 0x10000000L
  19 #define HAVE_ERR_REMOVE_THREAD_STATE
  20 #endif
  21
  22 static int rsa_err(const char *msg)
  23 {
  24         unsigned long sslErr = ERR_get_error();
  25
  26         fprintf(stderr, "%s", msg);
  27         fprintf(stderr, ": %s\n",
  28                 ERR_error_string(sslErr, 0));
  29
  30         return -1;
  31 }
  32
  33 /**
  34  * rsa_get_pub_key() - read a public key from a .crt file
  35  *
  36  * @keydir:     Directory containins the key
  37  * @name        Name of key file (will have a .crt extension)
  38  * @rsap        Returns RSA object, or NULL on failure
  39  * @return 0 if ok, -ve on error (in which case *rsap will be set to NULL)
  40  */
  41 static int rsa_get_pub_key(const char *keydir, const char *name, RSA **rsap)
  42 {
  43         char path[1024];
  44         EVP_PKEY *key;
  45         X509 *cert;
  46         RSA *rsa;
  47         FILE *f;
  48         int ret;
  49
  50         *rsap = NULL;
  51         snprintf(path, sizeof(path), "%s/%s.crt", keydir, name);
  52         f = fopen(path, "r");
  53         if (!f) {
  54                 fprintf(stderr, "Couldn't open RSA certificate: '%s': %s\n",
  55                         path, strerror(errno));
  56                 return -EACCES;
  57         }
  58
  59         /* Read the certificate */
  60         cert = NULL;
  61         if (!PEM_read_X509(f, &cert, NULL, NULL)) {
  62                 rsa_err("Couldn't read certificate");
  63                 ret = -EINVAL;
  64                 goto err_cert;
  65         }
  66
  67         /* Get the public key from the certificate. */
  68         key = X509_get_pubkey(cert);
  69         if (!key) {
  70                 rsa_err("Couldn't read public key\n");
  71                 ret = -EINVAL;
  72                 goto err_pubkey;
  73         }
  74
  75         /* Convert to a RSA_style key. */
  76         rsa = EVP_PKEY_get1_RSA(key);
  77         if (!rsa) {
  78                 rsa_err("Couldn't convert to a RSA style key");
  79                 ret = -EINVAL;
  80                 goto err_rsa;
  81         }
  82         fclose(f);
  83         EVP_PKEY_free(key);
  84         X509_free(cert);
  85         *rsap = rsa;
  86
  87         return 0;
  88
  89 err_rsa:
  90         EVP_PKEY_free(key);
  91 err_pubkey:
  92         X509_free(cert);
  93 err_cert:
  94         fclose(f);
  95         return ret;
  96 }
  97
  98 /**
  99  * rsa_get_priv_key() - read a private key from a .key file
 100  *
 101  * @keydir:     Directory containins the key
 102  * @name        Name of key file (will have a .key extension)
 103  * @rsap        Returns RSA object, or NULL on failure
 104  * @return 0 if ok, -ve on error (in which case *rsap will be set to NULL)
 105  */
 106 static int rsa_get_priv_key(const char *keydir, const char *name, RSA **rsap)
 107 {
 108         char path[1024];
 109         RSA *rsa;
 110         FILE *f;
 111
 112         *rsap = NULL;
 113         snprintf(path, sizeof(path), "%s/%s.key", keydir, name);
 114         f = fopen(path, "r");
 115         if (!f) {
 116                 fprintf(stderr, "Couldn't open RSA private key: '%s': %s\n",
 117                         path, strerror(errno));
 118                 return -ENOENT;
 119         }
 120
 121         rsa = PEM_read_RSAPrivateKey(f, 0, NULL, path);
 122         if (!rsa) {
 123                 rsa_err("Failure reading private key");
 124                 fclose(f);
 125                 return -EPROTO;
 126         }
 127         fclose(f);
 128         *rsap = rsa;
 129
 130         return 0;
 131 }
 132
 133 static int rsa_init(void)
 134 {
 135         int ret;
 136
 137         ret = SSL_library_init();
 138         if (!ret) {
 139                 fprintf(stderr, "Failure to init SSL library\n");
 140                 return -1;
 141         }
 142         SSL_load_error_strings();
 143
 144         OpenSSL_add_all_algorithms();
 145         OpenSSL_add_all_digests();
 146         OpenSSL_add_all_ciphers();
 147
 148         return 0;
 149 }
 150
 151 static void rsa_remove(void)
 152 {
 153         CRYPTO_cleanup_all_ex_data();
 154         ERR_free_strings();
 155 #ifdef HAVE_ERR_REMOVE_THREAD_STATE
 156         ERR_remove_thread_state(NULL);
 157 #else
 158         ERR_remove_state(0);
 159 #endif
 160         EVP_cleanup();
 161 }
 162
 163 static int rsa_sign_with_key(RSA *rsa, struct checksum_algo *checksum_algo,
 164                 const struct image_region region[], int region_count,
 165                 uint8_t **sigp, uint *sig_size)
 166 {
 167         EVP_PKEY *key;
 168         EVP_MD_CTX *context;
 169         int size, ret = 0;
 170         uint8_t *sig;
 171         int i;
 172
 173         key = EVP_PKEY_new();
 174         if (!key)
 175                 return rsa_err("EVP_PKEY object creation failed");
 176
 177         if (!EVP_PKEY_set1_RSA(key, rsa)) {
 178                 ret = rsa_err("EVP key setup failed");
 179                 goto err_set;
 180         }
 181
 182         size = EVP_PKEY_size(key);
 183         sig = malloc(size);
 184         if (!sig) {
 185                 fprintf(stderr, "Out of memory for signature (%d bytes)\n",
 186                         size);
 187                 ret = -ENOMEM;
 188                 goto err_alloc;
 189         }
 190
 191         context = EVP_MD_CTX_create();
 192         if (!context) {
 193                 ret = rsa_err("EVP context creation failed");
 194                 goto err_create;
 195         }
 196         EVP_MD_CTX_init(context);
 197         if (!EVP_SignInit(context, checksum_algo->calculate_sign())) {
 198                 ret = rsa_err("Signer setup failed");
 199                 goto err_sign;
 200         }
 201
 202         for (i = 0; i < region_count; i++) {
 203                 if (!EVP_SignUpdate(context, region[i].data, region[i].size)) {
 204                         ret = rsa_err("Signing data failed");
 205                         goto err_sign;
 206                 }
 207         }
 208
 209         if (!EVP_SignFinal(context, sig, sig_size, key)) {
 210                 ret = rsa_err("Could not obtain signature");
 211                 goto err_sign;
 212         }
 213         EVP_MD_CTX_cleanup(context);
 214         EVP_MD_CTX_destroy(context);
 215         EVP_PKEY_free(key);
 216
 217         debug("Got signature: %d bytes, expected %d\n", *sig_size, size);
 218         *sigp = sig;
 219         *sig_size = size;
 220
 221         return 0;
 222
 223 err_sign:
 224         EVP_MD_CTX_destroy(context);
 225 err_create:
 226         free(sig);
 227 err_alloc:
 228 err_set:
 229         EVP_PKEY_free(key);
 230         return ret;
 231 }
 232
 233 int rsa_sign(struct image_sign_info *info,
 234              const struct image_region region[], int region_count,
 235              uint8_t **sigp, uint *sig_len)
 236 {
 237         RSA *rsa;
 238         int ret;
 239
 240         ret = rsa_init();
 241         if (ret)
 242                 return ret;
 243
 244         ret = rsa_get_priv_key(info->keydir, info->keyname, &rsa);
 245         if (ret)
 246                 goto err_priv;
 247         ret = rsa_sign_with_key(rsa, info->algo->checksum, region,
 248                                 region_count, sigp, sig_len);
 249         if (ret)
 250                 goto err_sign;
 251
 252         RSA_free(rsa);
 253         rsa_remove();
 254
 255         return ret;
 256
 257 err_sign:
 258         RSA_free(rsa);
 259 err_priv:
 260         rsa_remove();
 261         return ret;
 262 }
 263
 264 /*
 265  * rsa_get_exponent(): - Get the public exponent from an RSA key
 266  */
 267 static int rsa_get_exponent(RSA *key, uint64_t *e)
 268 {
 269         int ret;
 270         BIGNUM *bn_te;
 271         uint64_t te;
 272
 273         ret = -EINVAL;
 274         bn_te = NULL;
 275
 276         if (!e)
 277                 goto cleanup;
 278
 279         if (BN_num_bits(key->e) > 64)
 280                 goto cleanup;
 281
 282         *e = BN_get_word(key->e);
 283
 284         if (BN_num_bits(key->e) < 33) {
 285                 ret = 0;
 286                 goto cleanup;
 287         }
 288
 289         bn_te = BN_dup(key->e);
 290         if (!bn_te)
 291                 goto cleanup;
 292
 293         if (!BN_rshift(bn_te, bn_te, 32))
 294                 goto cleanup;
 295
 296         if (!BN_mask_bits(bn_te, 32))
 297                 goto cleanup;
 298
 299         te = BN_get_word(bn_te);
 300         te <<= 32;
 301         *e |= te;
 302         ret = 0;
 303
 304 cleanup:
 305         if (bn_te)
 306                 BN_free(bn_te);
 307
 308         return ret;
 309 }
 310
 311 /*
 312  * rsa_get_params(): - Get the important parameters of an RSA public key
 313  */
 314 int rsa_get_params(RSA *key, uint64_t *exponent, uint32_t *n0_invp,
 315                    BIGNUM **modulusp, BIGNUM **r_squaredp)
 316 {
 317         BIGNUM *big1, *big2, *big32, *big2_32;
 318         BIGNUM *n, *r, *r_squared, *tmp;
 319         BN_CTX *bn_ctx = BN_CTX_new();
 320         int ret = 0;
 321
 322         /* Initialize BIGNUMs */
 323         big1 = BN_new();
 324         big2 = BN_new();
 325         big32 = BN_new();
 326         r = BN_new();
 327         r_squared = BN_new();
 328         tmp = BN_new();
 329         big2_32 = BN_new();
 330         n = BN_new();
 331         if (!big1 || !big2 || !big32 || !r || !r_squared || !tmp || !big2_32 ||
 332             !n) {
 333                 fprintf(stderr, "Out of memory (bignum)\n");
 334                 return -ENOMEM;
 335         }
 336
 337         if (0 != rsa_get_exponent(key, exponent))
 338                 ret = -1;
 339
 340         if (!BN_copy(n, key->n) || !BN_set_word(big1, 1L) ||
 341             !BN_set_word(big2, 2L) || !BN_set_word(big32, 32L))
 342                 ret = -1;
 343
 344         /* big2_32 = 2^32 */
 345         if (!BN_exp(big2_32, big2, big32, bn_ctx))
 346                 ret = -1;
 347
 348         /* Calculate n0_inv = -1 / n[0] mod 2^32 */
 349         if (!BN_mod_inverse(tmp, n, big2_32, bn_ctx) ||
 350             !BN_sub(tmp, big2_32, tmp))
 351                 ret = -1;
 352         *n0_invp = BN_get_word(tmp);
 353
 354         /* Calculate R = 2^(# of key bits) */
 355         if (!BN_set_word(tmp, BN_num_bits(n)) ||
 356             !BN_exp(r, big2, tmp, bn_ctx))
 357                 ret = -1;
 358
 359         /* Calculate r_squared = R^2 mod n */
 360         if (!BN_copy(r_squared, r) ||
 361             !BN_mul(tmp, r_squared, r, bn_ctx) ||
 362             !BN_mod(r_squared, tmp, n, bn_ctx))
 363                 ret = -1;
 364
 365         *modulusp = n;
 366         *r_squaredp = r_squared;
 367
 368         BN_free(big1);
 369         BN_free(big2);
 370         BN_free(big32);
 371         BN_free(r);
 372         BN_free(tmp);
 373         BN_free(big2_32);
 374         if (ret) {
 375                 fprintf(stderr, "Bignum operations failed\n");
 376                 return -ENOMEM;
 377         }
 378
 379         return ret;
 380 }
 381
 382 static int fdt_add_bignum(void *blob, int noffset, const char *prop_name,
 383                           BIGNUM *num, int num_bits)
 384 {
 385         int nwords = num_bits / 32;
 386         int size;
 387         uint32_t *buf, *ptr;
 388         BIGNUM *tmp, *big2, *big32, *big2_32;
 389         BN_CTX *ctx;
 390         int ret;
 391
 392         tmp = BN_new();
 393         big2 = BN_new();
 394         big32 = BN_new();
 395         big2_32 = BN_new();
 396         if (!tmp || !big2 || !big32 || !big2_32) {
 397                 fprintf(stderr, "Out of memory (bignum)\n");
 398                 return -ENOMEM;
 399         }
 400         ctx = BN_CTX_new();
 401         if (!tmp) {
 402                 fprintf(stderr, "Out of memory (bignum context)\n");
 403                 return -ENOMEM;
 404         }
 405         BN_set_word(big2, 2L);
 406         BN_set_word(big32, 32L);
 407         BN_exp(big2_32, big2, big32, ctx); /* B = 2^32 */
 408
 409         size = nwords * sizeof(uint32_t);
 410         buf = malloc(size);
 411         if (!buf) {
 412                 fprintf(stderr, "Out of memory (%d bytes)\n", size);
 413                 return -ENOMEM;
 414         }
 415
 416         /* Write out modulus as big endian array of integers */
 417         for (ptr = buf + nwords - 1; ptr >= buf; ptr--) {
 418                 BN_mod(tmp, num, big2_32, ctx); /* n = N mod B */
 419                 *ptr = cpu_to_fdt32(BN_get_word(tmp));
 420                 BN_rshift(num, num, 32); /*  N = N/B */
 421         }
 422
 423         ret = fdt_setprop(blob, noffset, prop_name, buf, size);
 424         if (ret) {
 425                 fprintf(stderr, "Failed to write public key to FIT\n");
 426                 return -ENOSPC;
 427         }
 428         free(buf);
 429         BN_free(tmp);
 430         BN_free(big2);
 431         BN_free(big32);
 432         BN_free(big2_32);
 433
 434         return ret;
 435 }
 436
 437 int rsa_add_verify_data(struct image_sign_info *info, void *keydest)
 438 {
 439         BIGNUM *modulus, *r_squared;
 440         uint64_t exponent;
 441         uint32_t n0_inv;
 442         int parent, node;
 443         char name[100];
 444         int ret;
 445         int bits;
 446         RSA *rsa;
 447
 448         debug("%s: Getting verification data\n", __func__);
 449         ret = rsa_get_pub_key(info->keydir, info->keyname, &rsa);
 450         if (ret)
 451                 return ret;
 452         ret = rsa_get_params(rsa, &exponent, &n0_inv, &modulus, &r_squared);
 453         if (ret)
 454                 return ret;
 455         bits = BN_num_bits(modulus);
 456         parent = fdt_subnode_offset(keydest, 0, FIT_SIG_NODENAME);
 457         if (parent == -FDT_ERR_NOTFOUND) {
 458                 parent = fdt_add_subnode(keydest, 0, FIT_SIG_NODENAME);
 459                 if (parent < 0) {
 460                         ret = parent;
 461                         if (ret != -FDT_ERR_NOSPACE) {
 462                                 fprintf(stderr, "Couldn't create signature node: %s\n",
 463                                         fdt_strerror(parent));
 464                         }
 465                 }
 466         }
 467         if (ret)
 468                 goto done;
 469
 470         /* Either create or overwrite the named key node */
 471         snprintf(name, sizeof(name), "key-%s", info->keyname);
 472         node = fdt_subnode_offset(keydest, parent, name);
 473         if (node == -FDT_ERR_NOTFOUND) {
 474                 node = fdt_add_subnode(keydest, parent, name);
 475                 if (node < 0) {
 476                         ret = node;
 477                         if (ret != -FDT_ERR_NOSPACE) {
 478                                 fprintf(stderr, "Could not create key subnode: %s\n",
 479                                         fdt_strerror(node));
 480                         }
 481                 }
 482         } else if (node < 0) {
 483                 fprintf(stderr, "Cannot select keys parent: %s\n",
 484                         fdt_strerror(node));
 485                 ret = node;
 486         }
 487
 488         if (!ret) {
 489                 ret = fdt_setprop_string(keydest, node, "key-name-hint",
 490                                  info->keyname);
 491         }
 492         if (!ret)
 493                 ret = fdt_setprop_u32(keydest, node, "rsa,num-bits", bits);
 494         if (!ret)
 495                 ret = fdt_setprop_u32(keydest, node, "rsa,n0-inverse", n0_inv);
 496         if (!ret) {
 497                 ret = fdt_setprop_u64(keydest, node, "rsa,exponent", exponent);
 498         }
 499         if (!ret) {
 500                 ret = fdt_add_bignum(keydest, node, "rsa,modulus", modulus,
 501                                      bits);
 502         }
 503         if (!ret) {
 504                 ret = fdt_add_bignum(keydest, node, "rsa,r-squared", r_squared,
 505                                      bits);
 506         }
 507         if (!ret) {
 508                 ret = fdt_setprop_string(keydest, node, FIT_ALGO_PROP,
 509                                          info->algo->name);
 510         }
 511         if (info->require_keys) {
 512                 ret = fdt_setprop_string(keydest, node, "required",
 513                                          info->require_keys);
 514         }
 515 done:
 516         BN_free(modulus);
 517         BN_free(r_squared);
 518         if (ret)
 519                 return ret == -FDT_ERR_NOSPACE ? -ENOSPC : -EIO;
 520
 521         return 0;
 522 }