xref: /openbmc/u-boot/lib/rsa/rsa-sign.c (revision 04735e9c5578dd4f3584be5454b9779e8e5c2af9)
1  /*
2   * Copyright (c) 2013, Google Inc.
3   *
4   * This program is free software; you can redistribute it and/or
5   * modify it under the terms of the GNU General Public License as
6   * published by the Free Software Foundation; either version 2 of
7   * the License, or (at your option) any later version.
8   *
9   * This program is distributed in the hope that it will be useful,
10   * but WITHOUT ANY WARRANTY; without even the implied warranty of
11   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
12   * GNU General Public License for more details.
13   *
14   * You should have received a copy of the GNU General Public License
15   * along with this program; if not, write to the Free Software
16   * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
17   * MA 02111-1307 USA
18   */
19  
20  #include "mkimage.h"
21  #include <stdio.h>
22  #include <string.h>
23  #include <image.h>
24  #include <time.h>
25  #include <openssl/rsa.h>
26  #include <openssl/pem.h>
27  #include <openssl/err.h>
28  #include <openssl/ssl.h>
29  #include <openssl/evp.h>
30  
31  #if OPENSSL_VERSION_NUMBER >= 0x10000000L
32  #define HAVE_ERR_REMOVE_THREAD_STATE
33  #endif
34  
35  static int rsa_err(const char *msg)
36  {
37  	unsigned long sslErr = ERR_get_error();
38  
39  	fprintf(stderr, "%s", msg);
40  	fprintf(stderr, ": %s\n",
41  		ERR_error_string(sslErr, 0));
42  
43  	return -1;
44  }
45  
46  /**
47   * rsa_get_pub_key() - read a public key from a .crt file
48   *
49   * @keydir:	Directory containins the key
50   * @name	Name of key file (will have a .crt extension)
51   * @rsap	Returns RSA object, or NULL on failure
52   * @return 0 if ok, -ve on error (in which case *rsap will be set to NULL)
53   */
54  static int rsa_get_pub_key(const char *keydir, const char *name, RSA **rsap)
55  {
56  	char path[1024];
57  	EVP_PKEY *key;
58  	X509 *cert;
59  	RSA *rsa;
60  	FILE *f;
61  	int ret;
62  
63  	*rsap = NULL;
64  	snprintf(path, sizeof(path), "%s/%s.crt", keydir, name);
65  	f = fopen(path, "r");
66  	if (!f) {
67  		fprintf(stderr, "Couldn't open RSA certificate: '%s': %s\n",
68  			path, strerror(errno));
69  		return -EACCES;
70  	}
71  
72  	/* Read the certificate */
73  	cert = NULL;
74  	if (!PEM_read_X509(f, &cert, NULL, NULL)) {
75  		rsa_err("Couldn't read certificate");
76  		ret = -EINVAL;
77  		goto err_cert;
78  	}
79  
80  	/* Get the public key from the certificate. */
81  	key = X509_get_pubkey(cert);
82  	if (!key) {
83  		rsa_err("Couldn't read public key\n");
84  		ret = -EINVAL;
85  		goto err_pubkey;
86  	}
87  
88  	/* Convert to a RSA_style key. */
89  	rsa = EVP_PKEY_get1_RSA(key);
90  	if (!rsa) {
91  		rsa_err("Couldn't convert to a RSA style key");
92  		goto err_rsa;
93  	}
94  	fclose(f);
95  	EVP_PKEY_free(key);
96  	X509_free(cert);
97  	*rsap = rsa;
98  
99  	return 0;
100  
101  err_rsa:
102  	EVP_PKEY_free(key);
103  err_pubkey:
104  	X509_free(cert);
105  err_cert:
106  	fclose(f);
107  	return ret;
108  }
109  
110  /**
111   * rsa_get_priv_key() - read a private key from a .key file
112   *
113   * @keydir:	Directory containins the key
114   * @name	Name of key file (will have a .key extension)
115   * @rsap	Returns RSA object, or NULL on failure
116   * @return 0 if ok, -ve on error (in which case *rsap will be set to NULL)
117   */
118  static int rsa_get_priv_key(const char *keydir, const char *name, RSA **rsap)
119  {
120  	char path[1024];
121  	RSA *rsa;
122  	FILE *f;
123  
124  	*rsap = NULL;
125  	snprintf(path, sizeof(path), "%s/%s.key", keydir, name);
126  	f = fopen(path, "r");
127  	if (!f) {
128  		fprintf(stderr, "Couldn't open RSA private key: '%s': %s\n",
129  			path, strerror(errno));
130  		return -ENOENT;
131  	}
132  
133  	rsa = PEM_read_RSAPrivateKey(f, 0, NULL, path);
134  	if (!rsa) {
135  		rsa_err("Failure reading private key");
136  		fclose(f);
137  		return -EPROTO;
138  	}
139  	fclose(f);
140  	*rsap = rsa;
141  
142  	return 0;
143  }
144  
145  static int rsa_init(void)
146  {
147  	int ret;
148  
149  	ret = SSL_library_init();
150  	if (!ret) {
151  		fprintf(stderr, "Failure to init SSL library\n");
152  		return -1;
153  	}
154  	SSL_load_error_strings();
155  
156  	OpenSSL_add_all_algorithms();
157  	OpenSSL_add_all_digests();
158  	OpenSSL_add_all_ciphers();
159  
160  	return 0;
161  }
162  
163  static void rsa_remove(void)
164  {
165  	CRYPTO_cleanup_all_ex_data();
166  	ERR_free_strings();
167  #ifdef HAVE_ERR_REMOVE_THREAD_STATE
168  	ERR_remove_thread_state(NULL);
169  #else
170  	ERR_remove_state(0);
171  #endif
172  	EVP_cleanup();
173  }
174  
175  static int rsa_sign_with_key(RSA *rsa, const struct image_region region[],
176  		int region_count, uint8_t **sigp, uint *sig_size)
177  {
178  	EVP_PKEY *key;
179  	EVP_MD_CTX *context;
180  	int size, ret = 0;
181  	uint8_t *sig;
182  	int i;
183  
184  	key = EVP_PKEY_new();
185  	if (!key)
186  		return rsa_err("EVP_PKEY object creation failed");
187  
188  	if (!EVP_PKEY_set1_RSA(key, rsa)) {
189  		ret = rsa_err("EVP key setup failed");
190  		goto err_set;
191  	}
192  
193  	size = EVP_PKEY_size(key);
194  	sig = malloc(size);
195  	if (!sig) {
196  		fprintf(stderr, "Out of memory for signature (%d bytes)\n",
197  			size);
198  		ret = -ENOMEM;
199  		goto err_alloc;
200  	}
201  
202  	context = EVP_MD_CTX_create();
203  	if (!context) {
204  		ret = rsa_err("EVP context creation failed");
205  		goto err_create;
206  	}
207  	EVP_MD_CTX_init(context);
208  	if (!EVP_SignInit(context, EVP_sha1())) {
209  		ret = rsa_err("Signer setup failed");
210  		goto err_sign;
211  	}
212  
213  	for (i = 0; i < region_count; i++) {
214  		if (!EVP_SignUpdate(context, region[i].data, region[i].size)) {
215  			ret = rsa_err("Signing data failed");
216  			goto err_sign;
217  		}
218  	}
219  
220  	if (!EVP_SignFinal(context, sig, sig_size, key)) {
221  		ret = rsa_err("Could not obtain signature");
222  		goto err_sign;
223  	}
224  	EVP_MD_CTX_cleanup(context);
225  	EVP_MD_CTX_destroy(context);
226  	EVP_PKEY_free(key);
227  
228  	debug("Got signature: %d bytes, expected %d\n", *sig_size, size);
229  	*sigp = sig;
230  	*sig_size = size;
231  
232  	return 0;
233  
234  err_sign:
235  	EVP_MD_CTX_destroy(context);
236  err_create:
237  	free(sig);
238  err_alloc:
239  err_set:
240  	EVP_PKEY_free(key);
241  	return ret;
242  }
243  
244  int rsa_sign(struct image_sign_info *info,
245  	     const struct image_region region[], int region_count,
246  	     uint8_t **sigp, uint *sig_len)
247  {
248  	RSA *rsa;
249  	int ret;
250  
251  	ret = rsa_init();
252  	if (ret)
253  		return ret;
254  
255  	ret = rsa_get_priv_key(info->keydir, info->keyname, &rsa);
256  	if (ret)
257  		goto err_priv;
258  	ret = rsa_sign_with_key(rsa, region, region_count, sigp, sig_len);
259  	if (ret)
260  		goto err_sign;
261  
262  	RSA_free(rsa);
263  	rsa_remove();
264  
265  	return ret;
266  
267  err_sign:
268  	RSA_free(rsa);
269  err_priv:
270  	rsa_remove();
271  	return ret;
272  }
273  
274  /*
275   * rsa_get_params(): - Get the important parameters of an RSA public key
276   */
277  int rsa_get_params(RSA *key, uint32_t *n0_invp, BIGNUM **modulusp,
278  		   BIGNUM **r_squaredp)
279  {
280  	BIGNUM *big1, *big2, *big32, *big2_32;
281  	BIGNUM *n, *r, *r_squared, *tmp;
282  	BN_CTX *bn_ctx = BN_CTX_new();
283  	int ret = 0;
284  
285  	/* Initialize BIGNUMs */
286  	big1 = BN_new();
287  	big2 = BN_new();
288  	big32 = BN_new();
289  	r = BN_new();
290  	r_squared = BN_new();
291  	tmp = BN_new();
292  	big2_32 = BN_new();
293  	n = BN_new();
294  	if (!big1 || !big2 || !big32 || !r || !r_squared || !tmp || !big2_32 ||
295  	    !n) {
296  		fprintf(stderr, "Out of memory (bignum)\n");
297  		return -ENOMEM;
298  	}
299  
300  	if (!BN_copy(n, key->n) || !BN_set_word(big1, 1L) ||
301  	    !BN_set_word(big2, 2L) || !BN_set_word(big32, 32L))
302  		ret = -1;
303  
304  	/* big2_32 = 2^32 */
305  	if (!BN_exp(big2_32, big2, big32, bn_ctx))
306  		ret = -1;
307  
308  	/* Calculate n0_inv = -1 / n[0] mod 2^32 */
309  	if (!BN_mod_inverse(tmp, n, big2_32, bn_ctx) ||
310  	    !BN_sub(tmp, big2_32, tmp))
311  		ret = -1;
312  	*n0_invp = BN_get_word(tmp);
313  
314  	/* Calculate R = 2^(# of key bits) */
315  	if (!BN_set_word(tmp, BN_num_bits(n)) ||
316  	    !BN_exp(r, big2, tmp, bn_ctx))
317  		ret = -1;
318  
319  	/* Calculate r_squared = R^2 mod n */
320  	if (!BN_copy(r_squared, r) ||
321  	    !BN_mul(tmp, r_squared, r, bn_ctx) ||
322  	    !BN_mod(r_squared, tmp, n, bn_ctx))
323  		ret = -1;
324  
325  	*modulusp = n;
326  	*r_squaredp = r_squared;
327  
328  	BN_free(big1);
329  	BN_free(big2);
330  	BN_free(big32);
331  	BN_free(r);
332  	BN_free(tmp);
333  	BN_free(big2_32);
334  	if (ret) {
335  		fprintf(stderr, "Bignum operations failed\n");
336  		return -ENOMEM;
337  	}
338  
339  	return ret;
340  }
341  
342  static int fdt_add_bignum(void *blob, int noffset, const char *prop_name,
343  			  BIGNUM *num, int num_bits)
344  {
345  	int nwords = num_bits / 32;
346  	int size;
347  	uint32_t *buf, *ptr;
348  	BIGNUM *tmp, *big2, *big32, *big2_32;
349  	BN_CTX *ctx;
350  	int ret;
351  
352  	tmp = BN_new();
353  	big2 = BN_new();
354  	big32 = BN_new();
355  	big2_32 = BN_new();
356  	if (!tmp || !big2 || !big32 || !big2_32) {
357  		fprintf(stderr, "Out of memory (bignum)\n");
358  		return -ENOMEM;
359  	}
360  	ctx = BN_CTX_new();
361  	if (!tmp) {
362  		fprintf(stderr, "Out of memory (bignum context)\n");
363  		return -ENOMEM;
364  	}
365  	BN_set_word(big2, 2L);
366  	BN_set_word(big32, 32L);
367  	BN_exp(big2_32, big2, big32, ctx); /* B = 2^32 */
368  
369  	size = nwords * sizeof(uint32_t);
370  	buf = malloc(size);
371  	if (!buf) {
372  		fprintf(stderr, "Out of memory (%d bytes)\n", size);
373  		return -ENOMEM;
374  	}
375  
376  	/* Write out modulus as big endian array of integers */
377  	for (ptr = buf + nwords - 1; ptr >= buf; ptr--) {
378  		BN_mod(tmp, num, big2_32, ctx); /* n = N mod B */
379  		*ptr = cpu_to_fdt32(BN_get_word(tmp));
380  		BN_rshift(num, num, 32); /*  N = N/B */
381  	}
382  
383  	ret = fdt_setprop(blob, noffset, prop_name, buf, size);
384  	if (ret) {
385  		fprintf(stderr, "Failed to write public key to FIT\n");
386  		return -ENOSPC;
387  	}
388  	free(buf);
389  	BN_free(tmp);
390  	BN_free(big2);
391  	BN_free(big32);
392  	BN_free(big2_32);
393  
394  	return ret;
395  }
396  
397  int rsa_add_verify_data(struct image_sign_info *info, void *keydest)
398  {
399  	BIGNUM *modulus, *r_squared;
400  	uint32_t n0_inv;
401  	int parent, node;
402  	char name[100];
403  	int ret;
404  	int bits;
405  	RSA *rsa;
406  
407  	debug("%s: Getting verification data\n", __func__);
408  	ret = rsa_get_pub_key(info->keydir, info->keyname, &rsa);
409  	if (ret)
410  		return ret;
411  	ret = rsa_get_params(rsa, &n0_inv, &modulus, &r_squared);
412  	if (ret)
413  		return ret;
414  	bits = BN_num_bits(modulus);
415  	parent = fdt_subnode_offset(keydest, 0, FIT_SIG_NODENAME);
416  	if (parent == -FDT_ERR_NOTFOUND) {
417  		parent = fdt_add_subnode(keydest, 0, FIT_SIG_NODENAME);
418  		if (parent < 0) {
419  			fprintf(stderr, "Couldn't create signature node: %s\n",
420  				fdt_strerror(parent));
421  			return -EINVAL;
422  		}
423  	}
424  
425  	/* Either create or overwrite the named key node */
426  	snprintf(name, sizeof(name), "key-%s", info->keyname);
427  	node = fdt_subnode_offset(keydest, parent, name);
428  	if (node == -FDT_ERR_NOTFOUND) {
429  		node = fdt_add_subnode(keydest, parent, name);
430  		if (node < 0) {
431  			fprintf(stderr, "Could not create key subnode: %s\n",
432  				fdt_strerror(node));
433  			return -EINVAL;
434  		}
435  	} else if (node < 0) {
436  		fprintf(stderr, "Cannot select keys parent: %s\n",
437  			fdt_strerror(node));
438  		return -ENOSPC;
439  	}
440  
441  	ret = fdt_setprop_string(keydest, node, "key-name-hint",
442  				 info->keyname);
443  	ret |= fdt_setprop_u32(keydest, node, "rsa,num-bits", bits);
444  	ret |= fdt_setprop_u32(keydest, node, "rsa,n0-inverse", n0_inv);
445  	ret |= fdt_add_bignum(keydest, node, "rsa,modulus", modulus, bits);
446  	ret |= fdt_add_bignum(keydest, node, "rsa,r-squared", r_squared, bits);
447  	ret |= fdt_setprop_string(keydest, node, FIT_ALGO_PROP,
448  				  info->algo->name);
449  	if (info->require_keys) {
450  		fdt_setprop_string(keydest, node, "required",
451  				   info->require_keys);
452  	}
453  	BN_free(modulus);
454  	BN_free(r_squared);
455  	if (ret)
456  		return -EIO;
457  
458  	return 0;
459  }
460