xref: /rk3399_rockchip-uboot/lib/rsa/rsa-sign.c (revision 2a3fb7bb049d69d96f3bc7dae8caa756fdc8a613)
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/bn.h>
13 #include <openssl/rsa.h>
14 #include <openssl/pem.h>
15 #include <openssl/err.h>
16 #include <openssl/ssl.h>
17 #include <openssl/evp.h>
18 #include <openssl/engine.h>
19 
20 #if OPENSSL_VERSION_NUMBER >= 0x10000000L
21 #define HAVE_ERR_REMOVE_THREAD_STATE
22 #endif
23 
24 #if OPENSSL_VERSION_NUMBER < 0x10100000L
25 static void RSA_get0_key(const RSA *r,
26                  const BIGNUM **n, const BIGNUM **e, const BIGNUM **d)
27 {
28    if (n != NULL)
29        *n = r->n;
30    if (e != NULL)
31        *e = r->e;
32    if (d != NULL)
33        *d = r->d;
34 }
35 #endif
36 
37 static int rsa_err(const char *msg)
38 {
39 	unsigned long sslErr = ERR_get_error();
40 
41 	fprintf(stderr, "%s", msg);
42 	fprintf(stderr, ": %s\n",
43 		ERR_error_string(sslErr, 0));
44 
45 	return -1;
46 }
47 
48 /**
49  * rsa_pem_get_pub_key() - read a public key from a .crt file
50  *
51  * @keydir:	Directory containins the key
52  * @name	Name of key file (will have a .crt extension)
53  * @rsap	Returns RSA object, or NULL on failure
54  * @return 0 if ok, -ve on error (in which case *rsap will be set to NULL)
55  */
56 static int rsa_pem_get_pub_key(const char *keydir, const char *name, RSA **rsap)
57 {
58 	char path[1024];
59 	EVP_PKEY *key;
60 	X509 *cert;
61 	RSA *rsa;
62 	FILE *f;
63 	int ret;
64 
65 	*rsap = NULL;
66 	snprintf(path, sizeof(path), "%s/%s.crt", keydir, name);
67 	f = fopen(path, "r");
68 	if (!f) {
69 		fprintf(stderr, "Couldn't open RSA certificate: '%s': %s\n",
70 			path, strerror(errno));
71 		return -EACCES;
72 	}
73 
74 	/* Read the certificate */
75 	cert = NULL;
76 	if (!PEM_read_X509(f, &cert, NULL, NULL)) {
77 		rsa_err("Couldn't read certificate");
78 		ret = -EINVAL;
79 		goto err_cert;
80 	}
81 
82 	/* Get the public key from the certificate. */
83 	key = X509_get_pubkey(cert);
84 	if (!key) {
85 		rsa_err("Couldn't read public key\n");
86 		ret = -EINVAL;
87 		goto err_pubkey;
88 	}
89 
90 	/* Convert to a RSA_style key. */
91 	rsa = EVP_PKEY_get1_RSA(key);
92 	if (!rsa) {
93 		rsa_err("Couldn't convert to a RSA style key");
94 		ret = -EINVAL;
95 		goto err_rsa;
96 	}
97 	fclose(f);
98 	EVP_PKEY_free(key);
99 	X509_free(cert);
100 	*rsap = rsa;
101 
102 	return 0;
103 
104 err_rsa:
105 	EVP_PKEY_free(key);
106 err_pubkey:
107 	X509_free(cert);
108 err_cert:
109 	fclose(f);
110 	return ret;
111 }
112 
113 /**
114  * rsa_engine_get_pub_key() - read a public key from given engine
115  *
116  * @keydir:	Key prefix
117  * @name	Name of key
118  * @engine	Engine to use
119  * @rsap	Returns RSA object, or NULL on failure
120  * @return 0 if ok, -ve on error (in which case *rsap will be set to NULL)
121  */
122 static int rsa_engine_get_pub_key(const char *keydir, const char *name,
123 				  ENGINE *engine, RSA **rsap)
124 {
125 	const char *engine_id;
126 	char key_id[1024];
127 	EVP_PKEY *key;
128 	RSA *rsa;
129 	int ret;
130 
131 	*rsap = NULL;
132 
133 	engine_id = ENGINE_get_id(engine);
134 
135 	if (engine_id && !strcmp(engine_id, "pkcs11")) {
136 		if (keydir)
137 			snprintf(key_id, sizeof(key_id),
138 				 "pkcs11:%s;object=%s;type=public",
139 				 keydir, name);
140 		else
141 			snprintf(key_id, sizeof(key_id),
142 				 "pkcs11:object=%s;type=public",
143 				 name);
144 	} else {
145 		fprintf(stderr, "Engine not supported\n");
146 		return -ENOTSUP;
147 	}
148 
149 	key = ENGINE_load_public_key(engine, key_id, NULL, NULL);
150 	if (!key)
151 		return rsa_err("Failure loading public key from engine");
152 
153 	/* Convert to a RSA_style key. */
154 	rsa = EVP_PKEY_get1_RSA(key);
155 	if (!rsa) {
156 		rsa_err("Couldn't convert to a RSA style key");
157 		ret = -EINVAL;
158 		goto err_rsa;
159 	}
160 
161 	EVP_PKEY_free(key);
162 	*rsap = rsa;
163 
164 	return 0;
165 
166 err_rsa:
167 	EVP_PKEY_free(key);
168 	return ret;
169 }
170 
171 /**
172  * rsa_get_pub_key() - read a public key
173  *
174  * @keydir:	Directory containing the key (PEM file) or key prefix (engine)
175  * @name	Name of key file (will have a .crt extension)
176  * @engine	Engine to use
177  * @rsap	Returns RSA object, or NULL on failure
178  * @return 0 if ok, -ve on error (in which case *rsap will be set to NULL)
179  */
180 static int rsa_get_pub_key(const char *keydir, const char *name,
181 			   ENGINE *engine, RSA **rsap)
182 {
183 	if (engine)
184 		return rsa_engine_get_pub_key(keydir, name, engine, rsap);
185 	return rsa_pem_get_pub_key(keydir, name, rsap);
186 }
187 
188 /**
189  * rsa_pem_get_priv_key() - read a private key from a .key file
190  *
191  * @keydir:	Directory containing the key
192  * @name	Name of key file (will have a .key extension)
193  * @rsap	Returns RSA object, or NULL on failure
194  * @return 0 if ok, -ve on error (in which case *rsap will be set to NULL)
195  */
196 static int rsa_pem_get_priv_key(const char *keydir, const char *name,
197 				RSA **rsap)
198 {
199 	char path[1024];
200 	RSA *rsa;
201 	FILE *f;
202 
203 	*rsap = NULL;
204 	snprintf(path, sizeof(path), "%s/%s.key", keydir, name);
205 	f = fopen(path, "r");
206 	if (!f) {
207 		fprintf(stderr, "Couldn't open RSA private key: '%s': %s\n",
208 			path, strerror(errno));
209 		return -ENOENT;
210 	}
211 
212 	rsa = PEM_read_RSAPrivateKey(f, 0, NULL, path);
213 	if (!rsa) {
214 		rsa_err("Failure reading private key");
215 		fclose(f);
216 		return -EPROTO;
217 	}
218 	fclose(f);
219 	*rsap = rsa;
220 
221 	return 0;
222 }
223 
224 /**
225  * rsa_engine_get_priv_key() - read a private key from given engine
226  *
227  * @keydir:	Key prefix
228  * @name	Name of key
229  * @engine	Engine to use
230  * @rsap	Returns RSA object, or NULL on failure
231  * @return 0 if ok, -ve on error (in which case *rsap will be set to NULL)
232  */
233 static int rsa_engine_get_priv_key(const char *keydir, const char *name,
234 				   ENGINE *engine, RSA **rsap)
235 {
236 	const char *engine_id;
237 	char key_id[1024];
238 	EVP_PKEY *key;
239 	RSA *rsa;
240 	int ret;
241 
242 	*rsap = NULL;
243 
244 	engine_id = ENGINE_get_id(engine);
245 
246 	if (engine_id && !strcmp(engine_id, "pkcs11")) {
247 		if (keydir)
248 			snprintf(key_id, sizeof(key_id),
249 				 "pkcs11:%s;object=%s;type=private",
250 				 keydir, name);
251 		else
252 			snprintf(key_id, sizeof(key_id),
253 				 "pkcs11:object=%s;type=private",
254 				 name);
255 	} else {
256 		fprintf(stderr, "Engine not supported\n");
257 		return -ENOTSUP;
258 	}
259 
260 	key = ENGINE_load_private_key(engine, key_id, NULL, NULL);
261 	if (!key)
262 		return rsa_err("Failure loading private key from engine");
263 
264 	/* Convert to a RSA_style key. */
265 	rsa = EVP_PKEY_get1_RSA(key);
266 	if (!rsa) {
267 		rsa_err("Couldn't convert to a RSA style key");
268 		ret = -EINVAL;
269 		goto err_rsa;
270 	}
271 
272 	EVP_PKEY_free(key);
273 	*rsap = rsa;
274 
275 	return 0;
276 
277 err_rsa:
278 	EVP_PKEY_free(key);
279 	return ret;
280 }
281 
282 /**
283  * rsa_get_priv_key() - read a private key
284  *
285  * @keydir:	Directory containing the key (PEM file) or key prefix (engine)
286  * @name	Name of key
287  * @engine	Engine to use for signing
288  * @rsap	Returns RSA object, or NULL on failure
289  * @return 0 if ok, -ve on error (in which case *rsap will be set to NULL)
290  */
291 static int rsa_get_priv_key(const char *keydir, const char *name,
292 			    ENGINE *engine, RSA **rsap)
293 {
294 	if (engine)
295 		return rsa_engine_get_priv_key(keydir, name, engine, rsap);
296 	return rsa_pem_get_priv_key(keydir, name, rsap);
297 }
298 
299 static int rsa_init(void)
300 {
301 	int ret;
302 
303 #if OPENSSL_VERSION_NUMBER < 0x10100000L
304 	ret = SSL_library_init();
305 #else
306 	ret = OPENSSL_init_ssl(0, NULL);
307 #endif
308 	if (!ret) {
309 		fprintf(stderr, "Failure to init SSL library\n");
310 		return -1;
311 	}
312 #if OPENSSL_VERSION_NUMBER < 0x10100000L
313 	SSL_load_error_strings();
314 
315 	OpenSSL_add_all_algorithms();
316 	OpenSSL_add_all_digests();
317 	OpenSSL_add_all_ciphers();
318 #endif
319 
320 	return 0;
321 }
322 
323 static int rsa_engine_init(const char *engine_id, ENGINE **pe)
324 {
325 	ENGINE *e;
326 	int ret;
327 
328 	ENGINE_load_builtin_engines();
329 
330 	e = ENGINE_by_id(engine_id);
331 	if (!e) {
332 		fprintf(stderr, "Engine isn't available\n");
333 		ret = -1;
334 		goto err_engine_by_id;
335 	}
336 
337 	if (!ENGINE_init(e)) {
338 		fprintf(stderr, "Couldn't initialize engine\n");
339 		ret = -1;
340 		goto err_engine_init;
341 	}
342 
343 	if (!ENGINE_set_default_RSA(e)) {
344 		fprintf(stderr, "Couldn't set engine as default for RSA\n");
345 		ret = -1;
346 		goto err_set_rsa;
347 	}
348 
349 	*pe = e;
350 
351 	return 0;
352 
353 err_set_rsa:
354 	ENGINE_finish(e);
355 err_engine_init:
356 	ENGINE_free(e);
357 err_engine_by_id:
358 #if OPENSSL_VERSION_NUMBER < 0x10100000L
359 	ENGINE_cleanup();
360 #endif
361 	return ret;
362 }
363 
364 static void rsa_remove(void)
365 {
366 #if OPENSSL_VERSION_NUMBER < 0x10100000L
367 	CRYPTO_cleanup_all_ex_data();
368 	ERR_free_strings();
369 #ifdef HAVE_ERR_REMOVE_THREAD_STATE
370 	ERR_remove_thread_state(NULL);
371 #else
372 	ERR_remove_state(0);
373 #endif
374 	EVP_cleanup();
375 #endif
376 }
377 
378 static void rsa_engine_remove(ENGINE *e)
379 {
380 	if (e) {
381 		ENGINE_finish(e);
382 		ENGINE_free(e);
383 	}
384 }
385 
386 /*
387  * With this data2sign.bin, we can provide it to who real holds the RAS-private
388  * key to sign current fit image. Then we replace the signature in fit image
389  * with a valid one.
390  */
391 static int gen_data2sign(const struct image_region region[], int region_count)
392 {
393 	char *file = "data2sign.bin";
394 	FILE *fd;
395 	int i;
396 
397 	fd = fopen(file, "wb");
398 	if (!fd) {
399 		fprintf(stderr, "Failed to create %s: %s\n",
400 			file, strerror(errno));
401 		return -ENOENT;
402 	}
403 
404 	for (i = 0; i < region_count; i++)
405 		fwrite(region[i].data, region[i].size, 1, fd);
406 
407 	fclose(fd);
408 
409 	return 0;
410 }
411 
412 static int rsa_sign_with_key(RSA *rsa, struct padding_algo *padding_algo,
413 			     struct checksum_algo *checksum_algo,
414 		const struct image_region region[], int region_count,
415 		uint8_t **sigp, uint *sig_size)
416 {
417 	EVP_PKEY *key;
418 	EVP_PKEY_CTX *ckey;
419 	EVP_MD_CTX *context;
420 	int ret = 0;
421 	size_t size;
422 	uint8_t *sig;
423 	int i;
424 
425 	key = EVP_PKEY_new();
426 	if (!key)
427 		return rsa_err("EVP_PKEY object creation failed");
428 
429 	if (!EVP_PKEY_set1_RSA(key, rsa)) {
430 		ret = rsa_err("EVP key setup failed");
431 		goto err_set;
432 	}
433 
434 	size = EVP_PKEY_size(key);
435 	sig = malloc(size);
436 	if (!sig) {
437 		fprintf(stderr, "Out of memory for signature (%zu bytes)\n",
438 			size);
439 		ret = -ENOMEM;
440 		goto err_alloc;
441 	}
442 
443 	context = EVP_MD_CTX_create();
444 	if (!context) {
445 		ret = rsa_err("EVP context creation failed");
446 		goto err_create;
447 	}
448 	EVP_MD_CTX_init(context);
449 
450 	ckey = EVP_PKEY_CTX_new(key, NULL);
451 	if (!ckey) {
452 		ret = rsa_err("EVP key context creation failed");
453 		goto err_create;
454 	}
455 
456 	if (EVP_DigestSignInit(context, &ckey,
457 			       checksum_algo->calculate_sign(),
458 			       NULL, key) <= 0) {
459 		ret = rsa_err("Signer setup failed");
460 		goto err_sign;
461 	}
462 
463 #ifdef CONFIG_FIT_ENABLE_RSASSA_PSS_SUPPORT
464 	if (padding_algo && !strcmp(padding_algo->name, "pss")) {
465 		if (EVP_PKEY_CTX_set_rsa_padding(ckey,
466 						 RSA_PKCS1_PSS_PADDING) <= 0) {
467 			ret = rsa_err("Signer padding setup failed");
468 			goto err_sign;
469 		}
470 	}
471 #endif /* CONFIG_FIT_ENABLE_RSASSA_PSS_SUPPORT */
472 
473 	for (i = 0; i < region_count; i++) {
474 		if (!EVP_DigestSignUpdate(context, region[i].data,
475 					  region[i].size)) {
476 			ret = rsa_err("Signing data failed");
477 			goto err_sign;
478 		}
479 	}
480 
481 	if (!EVP_DigestSignFinal(context, sig, &size)) {
482 		ret = rsa_err("Could not obtain signature");
483 		goto err_sign;
484 	}
485 
486 	#if OPENSSL_VERSION_NUMBER < 0x10100000L || \
487 		(defined(LIBRESSL_VERSION_NUMBER) && LIBRESSL_VERSION_NUMBER < 0x02070000fL)
488 		EVP_MD_CTX_cleanup(context);
489 	#else
490 		EVP_MD_CTX_reset(context);
491 	#endif
492 	EVP_MD_CTX_destroy(context);
493 	EVP_PKEY_free(key);
494 
495 	debug("Got signature: %d bytes, expected %zu\n", *sig_size, size);
496 	*sigp = sig;
497 	*sig_size = size;
498 
499 	gen_data2sign(region, region_count);
500 
501 	return 0;
502 
503 err_sign:
504 	EVP_MD_CTX_destroy(context);
505 err_create:
506 	free(sig);
507 err_alloc:
508 err_set:
509 	EVP_PKEY_free(key);
510 	return ret;
511 }
512 
513 int rsa_sign(struct image_sign_info *info,
514 	     const struct image_region region[], int region_count,
515 	     uint8_t **sigp, uint *sig_len)
516 {
517 	RSA *rsa;
518 	ENGINE *e = NULL;
519 	int ret;
520 
521 	ret = rsa_init();
522 	if (ret)
523 		return ret;
524 
525 	if (info->engine_id) {
526 		ret = rsa_engine_init(info->engine_id, &e);
527 		if (ret)
528 			goto err_engine;
529 	}
530 
531 	ret = rsa_get_priv_key(info->keydir, info->keyname, e, &rsa);
532 	if (ret)
533 		goto err_priv;
534 	ret = rsa_sign_with_key(rsa, info->padding, info->checksum, region,
535 				region_count, sigp, sig_len);
536 	if (ret)
537 		goto err_sign;
538 
539 	RSA_free(rsa);
540 	if (info->engine_id)
541 		rsa_engine_remove(e);
542 	rsa_remove();
543 
544 	return ret;
545 
546 err_sign:
547 	RSA_free(rsa);
548 err_priv:
549 	if (info->engine_id)
550 		rsa_engine_remove(e);
551 err_engine:
552 	rsa_remove();
553 	return ret;
554 }
555 
556 /*
557  * rsa_get_exponent(): - Get the public exponent from an RSA key
558  */
559 static int rsa_get_exponent(RSA *key, uint64_t *e)
560 {
561 	int ret;
562 	BIGNUM *bn_te;
563 	const BIGNUM *key_e;
564 	uint64_t te;
565 
566 	ret = -EINVAL;
567 	bn_te = NULL;
568 
569 	if (!e)
570 		goto cleanup;
571 
572 	RSA_get0_key(key, NULL, &key_e, NULL);
573 	if (BN_num_bits(key_e) > 64)
574 		goto cleanup;
575 
576 	*e = BN_get_word(key_e);
577 
578 	if (BN_num_bits(key_e) < 33) {
579 		ret = 0;
580 		goto cleanup;
581 	}
582 
583 	bn_te = BN_dup(key_e);
584 	if (!bn_te)
585 		goto cleanup;
586 
587 	if (!BN_rshift(bn_te, bn_te, 32))
588 		goto cleanup;
589 
590 	if (!BN_mask_bits(bn_te, 32))
591 		goto cleanup;
592 
593 	te = BN_get_word(bn_te);
594 	te <<= 32;
595 	*e |= te;
596 	ret = 0;
597 
598 cleanup:
599 	if (bn_te)
600 		BN_free(bn_te);
601 
602 	return ret;
603 }
604 
605 /*
606  * rsa_get_params(): - Get the important parameters of an RSA public key
607  */
608 int rsa_get_params(RSA *key, uint64_t *exponent, uint32_t *n0_invp,
609 		   BIGNUM **modulusp, BIGNUM **exponent_BN, BIGNUM **r_squaredp,
610 		   BIGNUM **c_factorp, BIGNUM **np_factorp)
611 {
612 	BIGNUM *big1, *big2, *big32, *big2_32, *big4100, *big2180;
613 	BIGNUM *n, *e, *r, *r_squared, *tmp, *c_factor, *np_factor;
614 	const BIGNUM *key_n, *key_e;
615 	BN_CTX *bn_ctx = BN_CTX_new();
616 	int ret = 0;
617 
618 	/* Initialize BIGNUMs */
619 	big1 = BN_new();
620 	big2 = BN_new();
621 	big32 = BN_new();
622 	big4100 = BN_new();
623 	big2180 = BN_new();
624 
625 	r = BN_new();
626 	r_squared = BN_new();
627 	c_factor = BN_new();
628 	np_factor = BN_new();
629 	tmp = BN_new();
630 	big2_32 = BN_new();
631 	n = BN_new();
632 	e = BN_new();
633 	if (!big1 || !big2 || !big32 || !big4100 || !big2180 || !r ||
634 	    !r_squared || !tmp || !big2_32 || !n || !e ||
635 	    !c_factor || !np_factor) {
636 		fprintf(stderr, "Out of memory (bignum)\n");
637 		return -ENOMEM;
638 	}
639 
640 	if (0 != rsa_get_exponent(key, exponent))
641 		ret = -1;
642 
643 	RSA_get0_key(key, &key_n, &key_e, NULL);
644 	if (!BN_copy(n, key_n) || !BN_copy(e, key_e) ||
645 	    !BN_set_word(big1, 1L) ||
646 	    !BN_set_word(big2, 2L) || !BN_set_word(big32, 32L) ||
647 	    !BN_set_word(big4100, 4100L) || !BN_set_word(big2180, 2180L))
648 		ret = -1;
649 
650 	/* big2_32 = 2^32 */
651 	if (!BN_exp(big2_32, big2, big32, bn_ctx))
652 		ret = -1;
653 
654 	/* Calculate n0_inv = -1 / n[0] mod 2^32 */
655 	if (!BN_mod_inverse(tmp, n, big2_32, bn_ctx) ||
656 	    !BN_sub(tmp, big2_32, tmp))
657 		ret = -1;
658 	*n0_invp = BN_get_word(tmp);
659 
660 	/* Calculate R = 2^(# of key bits) */
661 	if (!BN_set_word(tmp, BN_num_bits(n)) ||
662 	    !BN_exp(r, big2, tmp, bn_ctx))
663 		ret = -1;
664 
665 	/* Calculate r_squared = R^2 mod n */
666 	if (!BN_copy(r_squared, r) ||
667 	    !BN_mul(tmp, r_squared, r, bn_ctx) ||
668 	    !BN_mod(r_squared, tmp, n, bn_ctx))
669 		ret = -1;
670 
671 	/* Calculate c_factor = 2^4100 mod n */
672 	if (!BN_exp(tmp, big2, big4100, bn_ctx) ||
673 	    !BN_mod(c_factor, tmp, n, bn_ctx))
674 		ret = -1;
675 
676 	/* Calculate np_factor = 2^2180 div n */
677 	if (!BN_exp(tmp, big2, big2180, bn_ctx) ||
678 	    !BN_div(np_factor, NULL, tmp, n, bn_ctx))
679 		ret = -1;
680 
681 	*modulusp = n;
682 	*exponent_BN = e;
683 	*r_squaredp = r_squared;
684 	*c_factorp = c_factor;
685 	*np_factorp = np_factor;
686 
687 	BN_free(big1);
688 	BN_free(big2);
689 	BN_free(big32);
690 	BN_free(big4100);
691 	BN_free(big2180);
692 	BN_free(r);
693 	BN_free(tmp);
694 	BN_free(big2_32);
695 	if (ret) {
696 		fprintf(stderr, "Bignum operations failed\n");
697 		return -ENOMEM;
698 	}
699 
700 	return ret;
701 }
702 
703 static int fdt_add_bignum(void *blob, int noffset, const char *prop_name,
704 			  BIGNUM *num, int num_bits)
705 {
706 	int nwords = num_bits / 32;
707 	int size;
708 	uint32_t *buf, *ptr;
709 	BIGNUM *tmp, *big2, *big32, *big2_32;
710 	BN_CTX *ctx;
711 	int ret;
712 
713 	tmp = BN_new();
714 	big2 = BN_new();
715 	big32 = BN_new();
716 	big2_32 = BN_new();
717 	if (!tmp || !big2 || !big32 || !big2_32) {
718 		fprintf(stderr, "Out of memory (bignum)\n");
719 		return -ENOMEM;
720 	}
721 	ctx = BN_CTX_new();
722 	if (!tmp) {
723 		fprintf(stderr, "Out of memory (bignum context)\n");
724 		return -ENOMEM;
725 	}
726 	BN_set_word(big2, 2L);
727 	BN_set_word(big32, 32L);
728 	BN_exp(big2_32, big2, big32, ctx); /* B = 2^32 */
729 
730 	size = nwords * sizeof(uint32_t);
731 	buf = malloc(size);
732 	if (!buf) {
733 		fprintf(stderr, "Out of memory (%d bytes)\n", size);
734 		return -ENOMEM;
735 	}
736 
737 	/* Write out modulus as big endian array of integers */
738 	for (ptr = buf + nwords - 1; ptr >= buf; ptr--) {
739 		BN_mod(tmp, num, big2_32, ctx); /* n = N mod B */
740 		*ptr = cpu_to_fdt32(BN_get_word(tmp));
741 		BN_rshift(num, num, 32); /*  N = N/B */
742 	}
743 
744 	/*
745 	 * We try signing with successively increasing size values, so this
746 	 * might fail several times
747 	 */
748 	ret = fdt_setprop(blob, noffset, prop_name, buf, size);
749 	if (ret)
750 		return -FDT_ERR_NOSPACE;
751 	free(buf);
752 	BN_free(tmp);
753 	BN_free(big2);
754 	BN_free(big32);
755 	BN_free(big2_32);
756 
757 	return ret;
758 }
759 
760 int rsa_add_verify_data(struct image_sign_info *info, void *keydest)
761 {
762 	BIGNUM *modulus, *exponent_BN, *r_squared, *c_factor, *np_factor;
763 	uint64_t exponent;
764 	uint32_t n0_inv;
765 	int parent, node;
766 	char name[100];
767 	int ret;
768 	int bits;
769 	RSA *rsa;
770 	ENGINE *e = NULL;
771 
772 	debug("%s: Getting verification data\n", __func__);
773 	if (info->engine_id) {
774 		ret = rsa_engine_init(info->engine_id, &e);
775 		if (ret)
776 			return ret;
777 	}
778 	ret = rsa_get_pub_key(info->keydir, info->keyname, e, &rsa);
779 	if (ret)
780 		goto err_get_pub_key;
781 	ret = rsa_get_params(rsa, &exponent, &n0_inv, &modulus,
782 			     &exponent_BN, &r_squared, &c_factor, &np_factor);
783 	if (ret)
784 		goto err_get_params;
785 	bits = BN_num_bits(modulus);
786 	parent = fdt_subnode_offset(keydest, 0, FIT_SIG_NODENAME);
787 	if (parent == -FDT_ERR_NOTFOUND) {
788 		parent = fdt_add_subnode(keydest, 0, FIT_SIG_NODENAME);
789 		if (parent < 0) {
790 			ret = parent;
791 			if (ret != -FDT_ERR_NOSPACE) {
792 				fprintf(stderr, "Couldn't create signature node: %s\n",
793 					fdt_strerror(parent));
794 			}
795 		}
796 	}
797 	if (ret)
798 		goto done;
799 
800 	/* Either create or overwrite the named key node */
801 	snprintf(name, sizeof(name), "key-%s", info->keyname);
802 	node = fdt_subnode_offset(keydest, parent, name);
803 	if (node == -FDT_ERR_NOTFOUND) {
804 		node = fdt_add_subnode(keydest, parent, name);
805 		if (node < 0) {
806 			ret = node;
807 			if (ret != -FDT_ERR_NOSPACE) {
808 				fprintf(stderr, "Could not create key subnode: %s\n",
809 					fdt_strerror(node));
810 			}
811 		}
812 	} else if (node < 0) {
813 		fprintf(stderr, "Cannot select keys parent: %s\n",
814 			fdt_strerror(node));
815 		ret = node;
816 	}
817 
818 	if (!ret) {
819 		ret = fdt_setprop_string(keydest, node, "key-name-hint",
820 				 info->keyname);
821 	}
822 	if (!ret)
823 		ret = fdt_setprop_u32(keydest, node, "rsa,num-bits", bits);
824 	if (!ret)
825 		ret = fdt_setprop_u32(keydest, node, "rsa,n0-inverse", n0_inv);
826 	if (!ret) {
827 		ret = fdt_setprop_u64(keydest, node, "rsa,exponent", exponent);
828 	}
829 	if (!ret) {
830 		ret = fdt_add_bignum(keydest, node, "rsa,exponent-BN",
831 				     exponent_BN, bits);
832 	}
833 	if (!ret) {
834 		ret = fdt_add_bignum(keydest, node, "rsa,modulus", modulus,
835 				     bits);
836 	}
837 	if (!ret) {
838 		ret = fdt_add_bignum(keydest, node, "rsa,r-squared", r_squared,
839 				     bits);
840 	}
841 	if (!ret) {
842 		ret = fdt_add_bignum(keydest, node, "rsa,c", c_factor,
843 				     bits);
844 	}
845 	if (!ret) {
846 		ret = fdt_add_bignum(keydest, node, "rsa,np", np_factor,
847 				     bits);
848 	}
849 	if (!ret) {
850 		ret = fdt_setprop_string(keydest, node, FIT_ALGO_PROP,
851 					 info->name);
852 	}
853 	if (!ret && info->require_keys) {
854 		ret = fdt_setprop_string(keydest, node, "required",
855 					 info->require_keys);
856 	}
857 done:
858 	BN_free(modulus);
859 	BN_free(r_squared);
860 	if (ret)
861 		ret = ret == -FDT_ERR_NOSPACE ? -ENOSPC : -EIO;
862 err_get_params:
863 	RSA_free(rsa);
864 err_get_pub_key:
865 	if (info->engine_id)
866 		rsa_engine_remove(e);
867 
868 	return ret;
869 }
870