xref: /openbmc/u-boot/lib/rsa/rsa-sign.c (revision db74cbfc)
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 #include <openssl/engine.h>
18 
19 #if OPENSSL_VERSION_NUMBER >= 0x10000000L
20 #define HAVE_ERR_REMOVE_THREAD_STATE
21 #endif
22 
23 static int rsa_err(const char *msg)
24 {
25 	unsigned long sslErr = ERR_get_error();
26 
27 	fprintf(stderr, "%s", msg);
28 	fprintf(stderr, ": %s\n",
29 		ERR_error_string(sslErr, 0));
30 
31 	return -1;
32 }
33 
34 /**
35  * rsa_pem_get_pub_key() - read a public key from a .crt file
36  *
37  * @keydir:	Directory containins the key
38  * @name	Name of key file (will have a .crt extension)
39  * @rsap	Returns RSA object, or NULL on failure
40  * @return 0 if ok, -ve on error (in which case *rsap will be set to NULL)
41  */
42 static int rsa_pem_get_pub_key(const char *keydir, const char *name, RSA **rsap)
43 {
44 	char path[1024];
45 	EVP_PKEY *key;
46 	X509 *cert;
47 	RSA *rsa;
48 	FILE *f;
49 	int ret;
50 
51 	*rsap = NULL;
52 	snprintf(path, sizeof(path), "%s/%s.crt", keydir, name);
53 	f = fopen(path, "r");
54 	if (!f) {
55 		fprintf(stderr, "Couldn't open RSA certificate: '%s': %s\n",
56 			path, strerror(errno));
57 		return -EACCES;
58 	}
59 
60 	/* Read the certificate */
61 	cert = NULL;
62 	if (!PEM_read_X509(f, &cert, NULL, NULL)) {
63 		rsa_err("Couldn't read certificate");
64 		ret = -EINVAL;
65 		goto err_cert;
66 	}
67 
68 	/* Get the public key from the certificate. */
69 	key = X509_get_pubkey(cert);
70 	if (!key) {
71 		rsa_err("Couldn't read public key\n");
72 		ret = -EINVAL;
73 		goto err_pubkey;
74 	}
75 
76 	/* Convert to a RSA_style key. */
77 	rsa = EVP_PKEY_get1_RSA(key);
78 	if (!rsa) {
79 		rsa_err("Couldn't convert to a RSA style key");
80 		ret = -EINVAL;
81 		goto err_rsa;
82 	}
83 	fclose(f);
84 	EVP_PKEY_free(key);
85 	X509_free(cert);
86 	*rsap = rsa;
87 
88 	return 0;
89 
90 err_rsa:
91 	EVP_PKEY_free(key);
92 err_pubkey:
93 	X509_free(cert);
94 err_cert:
95 	fclose(f);
96 	return ret;
97 }
98 
99 /**
100  * rsa_engine_get_pub_key() - read a public key from given engine
101  *
102  * @keydir:	Key prefix
103  * @name	Name of key
104  * @engine	Engine to use
105  * @rsap	Returns RSA object, or NULL on failure
106  * @return 0 if ok, -ve on error (in which case *rsap will be set to NULL)
107  */
108 static int rsa_engine_get_pub_key(const char *keydir, const char *name,
109 				  ENGINE *engine, RSA **rsap)
110 {
111 	const char *engine_id;
112 	char key_id[1024];
113 	EVP_PKEY *key;
114 	RSA *rsa;
115 	int ret;
116 
117 	*rsap = NULL;
118 
119 	engine_id = ENGINE_get_id(engine);
120 
121 	if (engine_id && !strcmp(engine_id, "pkcs11")) {
122 		if (keydir)
123 			snprintf(key_id, sizeof(key_id),
124 				 "pkcs11:%s;object=%s;type=public",
125 				 keydir, name);
126 		else
127 			snprintf(key_id, sizeof(key_id),
128 				 "pkcs11:object=%s;type=public",
129 				 name);
130 	} else {
131 		fprintf(stderr, "Engine not supported\n");
132 		return -ENOTSUP;
133 	}
134 
135 	key = ENGINE_load_public_key(engine, key_id, NULL, NULL);
136 	if (!key)
137 		return rsa_err("Failure loading public key from engine");
138 
139 	/* Convert to a RSA_style key. */
140 	rsa = EVP_PKEY_get1_RSA(key);
141 	if (!rsa) {
142 		rsa_err("Couldn't convert to a RSA style key");
143 		ret = -EINVAL;
144 		goto err_rsa;
145 	}
146 
147 	EVP_PKEY_free(key);
148 	*rsap = rsa;
149 
150 	return 0;
151 
152 err_rsa:
153 	EVP_PKEY_free(key);
154 	return ret;
155 }
156 
157 /**
158  * rsa_get_pub_key() - read a public key
159  *
160  * @keydir:	Directory containing the key (PEM file) or key prefix (engine)
161  * @name	Name of key file (will have a .crt extension)
162  * @engine	Engine to use
163  * @rsap	Returns RSA object, or NULL on failure
164  * @return 0 if ok, -ve on error (in which case *rsap will be set to NULL)
165  */
166 static int rsa_get_pub_key(const char *keydir, const char *name,
167 			   ENGINE *engine, RSA **rsap)
168 {
169 	if (engine)
170 		return rsa_engine_get_pub_key(keydir, name, engine, rsap);
171 	return rsa_pem_get_pub_key(keydir, name, rsap);
172 }
173 
174 /**
175  * rsa_pem_get_priv_key() - read a private key from a .key file
176  *
177  * @keydir:	Directory containing the key
178  * @name	Name of key file (will have a .key extension)
179  * @rsap	Returns RSA object, or NULL on failure
180  * @return 0 if ok, -ve on error (in which case *rsap will be set to NULL)
181  */
182 static int rsa_pem_get_priv_key(const char *keydir, const char *name,
183 				RSA **rsap)
184 {
185 	char path[1024];
186 	RSA *rsa;
187 	FILE *f;
188 
189 	*rsap = NULL;
190 	snprintf(path, sizeof(path), "%s/%s.key", keydir, name);
191 	f = fopen(path, "r");
192 	if (!f) {
193 		fprintf(stderr, "Couldn't open RSA private key: '%s': %s\n",
194 			path, strerror(errno));
195 		return -ENOENT;
196 	}
197 
198 	rsa = PEM_read_RSAPrivateKey(f, 0, NULL, path);
199 	if (!rsa) {
200 		rsa_err("Failure reading private key");
201 		fclose(f);
202 		return -EPROTO;
203 	}
204 	fclose(f);
205 	*rsap = rsa;
206 
207 	return 0;
208 }
209 
210 /**
211  * rsa_engine_get_priv_key() - read a private key from given engine
212  *
213  * @keydir:	Key prefix
214  * @name	Name of key
215  * @engine	Engine to use
216  * @rsap	Returns RSA object, or NULL on failure
217  * @return 0 if ok, -ve on error (in which case *rsap will be set to NULL)
218  */
219 static int rsa_engine_get_priv_key(const char *keydir, const char *name,
220 				   ENGINE *engine, RSA **rsap)
221 {
222 	const char *engine_id;
223 	char key_id[1024];
224 	EVP_PKEY *key;
225 	RSA *rsa;
226 	int ret;
227 
228 	*rsap = NULL;
229 
230 	engine_id = ENGINE_get_id(engine);
231 
232 	if (engine_id && !strcmp(engine_id, "pkcs11")) {
233 		if (keydir)
234 			snprintf(key_id, sizeof(key_id),
235 				 "pkcs11:%s;object=%s;type=private",
236 				 keydir, name);
237 		else
238 			snprintf(key_id, sizeof(key_id),
239 				 "pkcs11:object=%s;type=private",
240 				 name);
241 	} else {
242 		fprintf(stderr, "Engine not supported\n");
243 		return -ENOTSUP;
244 	}
245 
246 	key = ENGINE_load_private_key(engine, key_id, NULL, NULL);
247 	if (!key)
248 		return rsa_err("Failure loading private key from engine");
249 
250 	/* Convert to a RSA_style key. */
251 	rsa = EVP_PKEY_get1_RSA(key);
252 	if (!rsa) {
253 		rsa_err("Couldn't convert to a RSA style key");
254 		ret = -EINVAL;
255 		goto err_rsa;
256 	}
257 
258 	EVP_PKEY_free(key);
259 	*rsap = rsa;
260 
261 	return 0;
262 
263 err_rsa:
264 	EVP_PKEY_free(key);
265 	return ret;
266 }
267 
268 /**
269  * rsa_get_priv_key() - read a private key
270  *
271  * @keydir:	Directory containing the key (PEM file) or key prefix (engine)
272  * @name	Name of key
273  * @engine	Engine to use for signing
274  * @rsap	Returns RSA object, or NULL on failure
275  * @return 0 if ok, -ve on error (in which case *rsap will be set to NULL)
276  */
277 static int rsa_get_priv_key(const char *keydir, const char *name,
278 			    ENGINE *engine, RSA **rsap)
279 {
280 	if (engine)
281 		return rsa_engine_get_priv_key(keydir, name, engine, rsap);
282 	return rsa_pem_get_priv_key(keydir, name, rsap);
283 }
284 
285 static int rsa_init(void)
286 {
287 	int ret;
288 
289 	ret = SSL_library_init();
290 	if (!ret) {
291 		fprintf(stderr, "Failure to init SSL library\n");
292 		return -1;
293 	}
294 	SSL_load_error_strings();
295 
296 	OpenSSL_add_all_algorithms();
297 	OpenSSL_add_all_digests();
298 	OpenSSL_add_all_ciphers();
299 
300 	return 0;
301 }
302 
303 static int rsa_engine_init(const char *engine_id, ENGINE **pe)
304 {
305 	ENGINE *e;
306 	int ret;
307 
308 	ENGINE_load_builtin_engines();
309 
310 	e = ENGINE_by_id(engine_id);
311 	if (!e) {
312 		fprintf(stderr, "Engine isn't available\n");
313 		ret = -1;
314 		goto err_engine_by_id;
315 	}
316 
317 	if (!ENGINE_init(e)) {
318 		fprintf(stderr, "Couldn't initialize engine\n");
319 		ret = -1;
320 		goto err_engine_init;
321 	}
322 
323 	if (!ENGINE_set_default_RSA(e)) {
324 		fprintf(stderr, "Couldn't set engine as default for RSA\n");
325 		ret = -1;
326 		goto err_set_rsa;
327 	}
328 
329 	*pe = e;
330 
331 	return 0;
332 
333 err_set_rsa:
334 	ENGINE_finish(e);
335 err_engine_init:
336 	ENGINE_free(e);
337 err_engine_by_id:
338 	ENGINE_cleanup();
339 	return ret;
340 }
341 
342 static void rsa_remove(void)
343 {
344 	CRYPTO_cleanup_all_ex_data();
345 	ERR_free_strings();
346 #ifdef HAVE_ERR_REMOVE_THREAD_STATE
347 	ERR_remove_thread_state(NULL);
348 #else
349 	ERR_remove_state(0);
350 #endif
351 	EVP_cleanup();
352 }
353 
354 static void rsa_engine_remove(ENGINE *e)
355 {
356 	if (e) {
357 		ENGINE_finish(e);
358 		ENGINE_free(e);
359 	}
360 }
361 
362 static int rsa_sign_with_key(RSA *rsa, struct checksum_algo *checksum_algo,
363 		const struct image_region region[], int region_count,
364 		uint8_t **sigp, uint *sig_size)
365 {
366 	EVP_PKEY *key;
367 	EVP_MD_CTX *context;
368 	int size, ret = 0;
369 	uint8_t *sig;
370 	int i;
371 
372 	key = EVP_PKEY_new();
373 	if (!key)
374 		return rsa_err("EVP_PKEY object creation failed");
375 
376 	if (!EVP_PKEY_set1_RSA(key, rsa)) {
377 		ret = rsa_err("EVP key setup failed");
378 		goto err_set;
379 	}
380 
381 	size = EVP_PKEY_size(key);
382 	sig = malloc(size);
383 	if (!sig) {
384 		fprintf(stderr, "Out of memory for signature (%d bytes)\n",
385 			size);
386 		ret = -ENOMEM;
387 		goto err_alloc;
388 	}
389 
390 	context = EVP_MD_CTX_create();
391 	if (!context) {
392 		ret = rsa_err("EVP context creation failed");
393 		goto err_create;
394 	}
395 	EVP_MD_CTX_init(context);
396 	if (!EVP_SignInit(context, checksum_algo->calculate_sign())) {
397 		ret = rsa_err("Signer setup failed");
398 		goto err_sign;
399 	}
400 
401 	for (i = 0; i < region_count; i++) {
402 		if (!EVP_SignUpdate(context, region[i].data, region[i].size)) {
403 			ret = rsa_err("Signing data failed");
404 			goto err_sign;
405 		}
406 	}
407 
408 	if (!EVP_SignFinal(context, sig, sig_size, key)) {
409 		ret = rsa_err("Could not obtain signature");
410 		goto err_sign;
411 	}
412 	EVP_MD_CTX_cleanup(context);
413 	EVP_MD_CTX_destroy(context);
414 	EVP_PKEY_free(key);
415 
416 	debug("Got signature: %d bytes, expected %d\n", *sig_size, size);
417 	*sigp = sig;
418 	*sig_size = size;
419 
420 	return 0;
421 
422 err_sign:
423 	EVP_MD_CTX_destroy(context);
424 err_create:
425 	free(sig);
426 err_alloc:
427 err_set:
428 	EVP_PKEY_free(key);
429 	return ret;
430 }
431 
432 int rsa_sign(struct image_sign_info *info,
433 	     const struct image_region region[], int region_count,
434 	     uint8_t **sigp, uint *sig_len)
435 {
436 	RSA *rsa;
437 	ENGINE *e = NULL;
438 	int ret;
439 
440 	ret = rsa_init();
441 	if (ret)
442 		return ret;
443 
444 	if (info->engine_id) {
445 		ret = rsa_engine_init(info->engine_id, &e);
446 		if (ret)
447 			goto err_engine;
448 	}
449 
450 	ret = rsa_get_priv_key(info->keydir, info->keyname, e, &rsa);
451 	if (ret)
452 		goto err_priv;
453 	ret = rsa_sign_with_key(rsa, info->checksum, region,
454 				region_count, sigp, sig_len);
455 	if (ret)
456 		goto err_sign;
457 
458 	RSA_free(rsa);
459 	if (info->engine_id)
460 		rsa_engine_remove(e);
461 	rsa_remove();
462 
463 	return ret;
464 
465 err_sign:
466 	RSA_free(rsa);
467 err_priv:
468 	if (info->engine_id)
469 		rsa_engine_remove(e);
470 err_engine:
471 	rsa_remove();
472 	return ret;
473 }
474 
475 /*
476  * rsa_get_exponent(): - Get the public exponent from an RSA key
477  */
478 static int rsa_get_exponent(RSA *key, uint64_t *e)
479 {
480 	int ret;
481 	BIGNUM *bn_te;
482 	uint64_t te;
483 
484 	ret = -EINVAL;
485 	bn_te = NULL;
486 
487 	if (!e)
488 		goto cleanup;
489 
490 	if (BN_num_bits(key->e) > 64)
491 		goto cleanup;
492 
493 	*e = BN_get_word(key->e);
494 
495 	if (BN_num_bits(key->e) < 33) {
496 		ret = 0;
497 		goto cleanup;
498 	}
499 
500 	bn_te = BN_dup(key->e);
501 	if (!bn_te)
502 		goto cleanup;
503 
504 	if (!BN_rshift(bn_te, bn_te, 32))
505 		goto cleanup;
506 
507 	if (!BN_mask_bits(bn_te, 32))
508 		goto cleanup;
509 
510 	te = BN_get_word(bn_te);
511 	te <<= 32;
512 	*e |= te;
513 	ret = 0;
514 
515 cleanup:
516 	if (bn_te)
517 		BN_free(bn_te);
518 
519 	return ret;
520 }
521 
522 /*
523  * rsa_get_params(): - Get the important parameters of an RSA public key
524  */
525 int rsa_get_params(RSA *key, uint64_t *exponent, uint32_t *n0_invp,
526 		   BIGNUM **modulusp, BIGNUM **r_squaredp)
527 {
528 	BIGNUM *big1, *big2, *big32, *big2_32;
529 	BIGNUM *n, *r, *r_squared, *tmp;
530 	BN_CTX *bn_ctx = BN_CTX_new();
531 	int ret = 0;
532 
533 	/* Initialize BIGNUMs */
534 	big1 = BN_new();
535 	big2 = BN_new();
536 	big32 = BN_new();
537 	r = BN_new();
538 	r_squared = BN_new();
539 	tmp = BN_new();
540 	big2_32 = BN_new();
541 	n = BN_new();
542 	if (!big1 || !big2 || !big32 || !r || !r_squared || !tmp || !big2_32 ||
543 	    !n) {
544 		fprintf(stderr, "Out of memory (bignum)\n");
545 		return -ENOMEM;
546 	}
547 
548 	if (0 != rsa_get_exponent(key, exponent))
549 		ret = -1;
550 
551 	if (!BN_copy(n, key->n) || !BN_set_word(big1, 1L) ||
552 	    !BN_set_word(big2, 2L) || !BN_set_word(big32, 32L))
553 		ret = -1;
554 
555 	/* big2_32 = 2^32 */
556 	if (!BN_exp(big2_32, big2, big32, bn_ctx))
557 		ret = -1;
558 
559 	/* Calculate n0_inv = -1 / n[0] mod 2^32 */
560 	if (!BN_mod_inverse(tmp, n, big2_32, bn_ctx) ||
561 	    !BN_sub(tmp, big2_32, tmp))
562 		ret = -1;
563 	*n0_invp = BN_get_word(tmp);
564 
565 	/* Calculate R = 2^(# of key bits) */
566 	if (!BN_set_word(tmp, BN_num_bits(n)) ||
567 	    !BN_exp(r, big2, tmp, bn_ctx))
568 		ret = -1;
569 
570 	/* Calculate r_squared = R^2 mod n */
571 	if (!BN_copy(r_squared, r) ||
572 	    !BN_mul(tmp, r_squared, r, bn_ctx) ||
573 	    !BN_mod(r_squared, tmp, n, bn_ctx))
574 		ret = -1;
575 
576 	*modulusp = n;
577 	*r_squaredp = r_squared;
578 
579 	BN_free(big1);
580 	BN_free(big2);
581 	BN_free(big32);
582 	BN_free(r);
583 	BN_free(tmp);
584 	BN_free(big2_32);
585 	if (ret) {
586 		fprintf(stderr, "Bignum operations failed\n");
587 		return -ENOMEM;
588 	}
589 
590 	return ret;
591 }
592 
593 static int fdt_add_bignum(void *blob, int noffset, const char *prop_name,
594 			  BIGNUM *num, int num_bits)
595 {
596 	int nwords = num_bits / 32;
597 	int size;
598 	uint32_t *buf, *ptr;
599 	BIGNUM *tmp, *big2, *big32, *big2_32;
600 	BN_CTX *ctx;
601 	int ret;
602 
603 	tmp = BN_new();
604 	big2 = BN_new();
605 	big32 = BN_new();
606 	big2_32 = BN_new();
607 	if (!tmp || !big2 || !big32 || !big2_32) {
608 		fprintf(stderr, "Out of memory (bignum)\n");
609 		return -ENOMEM;
610 	}
611 	ctx = BN_CTX_new();
612 	if (!tmp) {
613 		fprintf(stderr, "Out of memory (bignum context)\n");
614 		return -ENOMEM;
615 	}
616 	BN_set_word(big2, 2L);
617 	BN_set_word(big32, 32L);
618 	BN_exp(big2_32, big2, big32, ctx); /* B = 2^32 */
619 
620 	size = nwords * sizeof(uint32_t);
621 	buf = malloc(size);
622 	if (!buf) {
623 		fprintf(stderr, "Out of memory (%d bytes)\n", size);
624 		return -ENOMEM;
625 	}
626 
627 	/* Write out modulus as big endian array of integers */
628 	for (ptr = buf + nwords - 1; ptr >= buf; ptr--) {
629 		BN_mod(tmp, num, big2_32, ctx); /* n = N mod B */
630 		*ptr = cpu_to_fdt32(BN_get_word(tmp));
631 		BN_rshift(num, num, 32); /*  N = N/B */
632 	}
633 
634 	/*
635 	 * We try signing with successively increasing size values, so this
636 	 * might fail several times
637 	 */
638 	ret = fdt_setprop(blob, noffset, prop_name, buf, size);
639 	if (ret)
640 		return -FDT_ERR_NOSPACE;
641 	free(buf);
642 	BN_free(tmp);
643 	BN_free(big2);
644 	BN_free(big32);
645 	BN_free(big2_32);
646 
647 	return ret;
648 }
649 
650 int rsa_add_verify_data(struct image_sign_info *info, void *keydest)
651 {
652 	BIGNUM *modulus, *r_squared;
653 	uint64_t exponent;
654 	uint32_t n0_inv;
655 	int parent, node;
656 	char name[100];
657 	int ret;
658 	int bits;
659 	RSA *rsa;
660 	ENGINE *e = NULL;
661 
662 	debug("%s: Getting verification data\n", __func__);
663 	if (info->engine_id) {
664 		ret = rsa_engine_init(info->engine_id, &e);
665 		if (ret)
666 			return ret;
667 	}
668 	ret = rsa_get_pub_key(info->keydir, info->keyname, e, &rsa);
669 	if (ret)
670 		goto err_get_pub_key;
671 	ret = rsa_get_params(rsa, &exponent, &n0_inv, &modulus, &r_squared);
672 	if (ret)
673 		goto err_get_params;
674 	bits = BN_num_bits(modulus);
675 	parent = fdt_subnode_offset(keydest, 0, FIT_SIG_NODENAME);
676 	if (parent == -FDT_ERR_NOTFOUND) {
677 		parent = fdt_add_subnode(keydest, 0, FIT_SIG_NODENAME);
678 		if (parent < 0) {
679 			ret = parent;
680 			if (ret != -FDT_ERR_NOSPACE) {
681 				fprintf(stderr, "Couldn't create signature node: %s\n",
682 					fdt_strerror(parent));
683 			}
684 		}
685 	}
686 	if (ret)
687 		goto done;
688 
689 	/* Either create or overwrite the named key node */
690 	snprintf(name, sizeof(name), "key-%s", info->keyname);
691 	node = fdt_subnode_offset(keydest, parent, name);
692 	if (node == -FDT_ERR_NOTFOUND) {
693 		node = fdt_add_subnode(keydest, parent, name);
694 		if (node < 0) {
695 			ret = node;
696 			if (ret != -FDT_ERR_NOSPACE) {
697 				fprintf(stderr, "Could not create key subnode: %s\n",
698 					fdt_strerror(node));
699 			}
700 		}
701 	} else if (node < 0) {
702 		fprintf(stderr, "Cannot select keys parent: %s\n",
703 			fdt_strerror(node));
704 		ret = node;
705 	}
706 
707 	if (!ret) {
708 		ret = fdt_setprop_string(keydest, node, "key-name-hint",
709 				 info->keyname);
710 	}
711 	if (!ret)
712 		ret = fdt_setprop_u32(keydest, node, "rsa,num-bits", bits);
713 	if (!ret)
714 		ret = fdt_setprop_u32(keydest, node, "rsa,n0-inverse", n0_inv);
715 	if (!ret) {
716 		ret = fdt_setprop_u64(keydest, node, "rsa,exponent", exponent);
717 	}
718 	if (!ret) {
719 		ret = fdt_add_bignum(keydest, node, "rsa,modulus", modulus,
720 				     bits);
721 	}
722 	if (!ret) {
723 		ret = fdt_add_bignum(keydest, node, "rsa,r-squared", r_squared,
724 				     bits);
725 	}
726 	if (!ret) {
727 		ret = fdt_setprop_string(keydest, node, FIT_ALGO_PROP,
728 					 info->name);
729 	}
730 	if (!ret && info->require_keys) {
731 		ret = fdt_setprop_string(keydest, node, "required",
732 					 info->require_keys);
733 	}
734 done:
735 	BN_free(modulus);
736 	BN_free(r_squared);
737 	if (ret)
738 		ret = ret == -FDT_ERR_NOSPACE ? -ENOSPC : -EIO;
739 err_get_params:
740 	RSA_free(rsa);
741 err_get_pub_key:
742 	if (info->engine_id)
743 		rsa_engine_remove(e);
744 
745 	return ret;
746 }
747