1 /*
2 * RSA
3 * Copyright (c) 2006-2014, Jouni Malinen <j@w1.fi>
4 *
5 * This software may be distributed under the terms of the BSD license.
6 * See README for more details.
7 */
8
9 #include "includes.h"
10
11 #include "common.h"
12 #include "asn1.h"
13 #include "bignum.h"
14 #include "rsa.h"
15
16
17 struct crypto_rsa_key {
18 int private_key; /* whether private key is set */
19 struct bignum *n; /* modulus (p * q) */
20 struct bignum *e; /* public exponent */
21 /* The following parameters are available only if private_key is set */
22 struct bignum *d; /* private exponent */
23 struct bignum *p; /* prime p (factor of n) */
24 struct bignum *q; /* prime q (factor of n) */
25 struct bignum *dmp1; /* d mod (p - 1); CRT exponent */
26 struct bignum *dmq1; /* d mod (q - 1); CRT exponent */
27 struct bignum *iqmp; /* 1 / q mod p; CRT coefficient */
28 };
29
30
crypto_rsa_parse_integer(const u8 * pos,const u8 * end,struct bignum * num)31 static const u8 * crypto_rsa_parse_integer(const u8 *pos, const u8 *end,
32 struct bignum *num)
33 {
34 struct asn1_hdr hdr;
35
36 if (pos == NULL)
37 return NULL;
38
39 if (asn1_get_next(pos, end - pos, &hdr) < 0 ||
40 hdr.class != ASN1_CLASS_UNIVERSAL || hdr.tag != ASN1_TAG_INTEGER) {
41 wpa_printf(MSG_DEBUG, "RSA: Expected INTEGER - found class %d "
42 "tag 0x%x", hdr.class, hdr.tag);
43 return NULL;
44 }
45
46 if (bignum_set_unsigned_bin(num, hdr.payload, hdr.length) < 0) {
47 wpa_printf(MSG_DEBUG, "RSA: Failed to parse INTEGER");
48 return NULL;
49 }
50
51 return hdr.payload + hdr.length;
52 }
53
54
55 /**
56 * crypto_rsa_import_public_key - Import an RSA public key
57 * @buf: Key buffer (DER encoded RSA public key)
58 * @len: Key buffer length in bytes
59 * Returns: Pointer to the public key or %NULL on failure
60 */
61 struct crypto_rsa_key *
crypto_rsa_import_public_key(const u8 * buf,size_t len)62 crypto_rsa_import_public_key(const u8 *buf, size_t len)
63 {
64 struct crypto_rsa_key *key;
65 struct asn1_hdr hdr;
66 const u8 *pos, *end;
67
68 key = os_zalloc(sizeof(*key));
69 if (key == NULL)
70 return NULL;
71
72 key->n = bignum_init();
73 key->e = bignum_init();
74 if (key->n == NULL || key->e == NULL) {
75 crypto_rsa_free(key);
76 return NULL;
77 }
78
79 /*
80 * PKCS #1, 7.1:
81 * RSAPublicKey ::= SEQUENCE {
82 * modulus INTEGER, -- n
83 * publicExponent INTEGER -- e
84 * }
85 */
86
87 if (asn1_get_next(buf, len, &hdr) < 0 ||
88 hdr.class != ASN1_CLASS_UNIVERSAL ||
89 hdr.tag != ASN1_TAG_SEQUENCE) {
90 wpa_printf(MSG_DEBUG, "RSA: Expected SEQUENCE "
91 "(public key) - found class %d tag 0x%x",
92 hdr.class, hdr.tag);
93 goto error;
94 }
95 pos = hdr.payload;
96 end = pos + hdr.length;
97
98 pos = crypto_rsa_parse_integer(pos, end, key->n);
99 pos = crypto_rsa_parse_integer(pos, end, key->e);
100
101 if (pos == NULL)
102 goto error;
103
104 if (pos != end) {
105 wpa_hexdump(MSG_DEBUG,
106 "RSA: Extra data in public key SEQUENCE",
107 pos, end - pos);
108 goto error;
109 }
110
111 return key;
112
113 error:
114 crypto_rsa_free(key);
115 return NULL;
116 }
117
118
119 struct crypto_rsa_key *
crypto_rsa_import_public_key_parts(const u8 * n,size_t n_len,const u8 * e,size_t e_len)120 crypto_rsa_import_public_key_parts(const u8 *n, size_t n_len,
121 const u8 *e, size_t e_len)
122 {
123 struct crypto_rsa_key *key;
124
125 key = os_zalloc(sizeof(*key));
126 if (key == NULL)
127 return NULL;
128
129 key->n = bignum_init();
130 key->e = bignum_init();
131 if (key->n == NULL || key->e == NULL ||
132 bignum_set_unsigned_bin(key->n, n, n_len) < 0 ||
133 bignum_set_unsigned_bin(key->e, e, e_len) < 0) {
134 crypto_rsa_free(key);
135 return NULL;
136 }
137
138 return key;
139 }
140
141
142 /**
143 * crypto_rsa_import_private_key - Import an RSA private key
144 * @buf: Key buffer (DER encoded RSA private key)
145 * @len: Key buffer length in bytes
146 * Returns: Pointer to the private key or %NULL on failure
147 */
148 struct crypto_rsa_key *
crypto_rsa_import_private_key(const u8 * buf,size_t len)149 crypto_rsa_import_private_key(const u8 *buf, size_t len)
150 {
151 struct crypto_rsa_key *key;
152 struct bignum *zero;
153 struct asn1_hdr hdr;
154 const u8 *pos, *end;
155
156 key = os_zalloc(sizeof(*key));
157 if (key == NULL)
158 return NULL;
159
160 key->private_key = 1;
161
162 key->n = bignum_init();
163 key->e = bignum_init();
164 key->d = bignum_init();
165 key->p = bignum_init();
166 key->q = bignum_init();
167 key->dmp1 = bignum_init();
168 key->dmq1 = bignum_init();
169 key->iqmp = bignum_init();
170
171 if (key->n == NULL || key->e == NULL || key->d == NULL ||
172 key->p == NULL || key->q == NULL || key->dmp1 == NULL ||
173 key->dmq1 == NULL || key->iqmp == NULL) {
174 crypto_rsa_free(key);
175 return NULL;
176 }
177
178 /*
179 * PKCS #1, 7.2:
180 * RSAPrivateKey ::= SEQUENCE {
181 * version Version,
182 * modulus INTEGER, -- n
183 * publicExponent INTEGER, -- e
184 * privateExponent INTEGER, -- d
185 * prime1 INTEGER, -- p
186 * prime2 INTEGER, -- q
187 * exponent1 INTEGER, -- d mod (p-1)
188 * exponent2 INTEGER, -- d mod (q-1)
189 * coefficient INTEGER -- (inverse of q) mod p
190 * }
191 *
192 * Version ::= INTEGER -- shall be 0 for this version of the standard
193 */
194 if (asn1_get_next(buf, len, &hdr) < 0 ||
195 hdr.class != ASN1_CLASS_UNIVERSAL ||
196 hdr.tag != ASN1_TAG_SEQUENCE) {
197 wpa_printf(MSG_DEBUG, "RSA: Expected SEQUENCE "
198 "(public key) - found class %d tag 0x%x",
199 hdr.class, hdr.tag);
200 goto error;
201 }
202 pos = hdr.payload;
203 end = pos + hdr.length;
204
205 zero = bignum_init();
206 if (zero == NULL)
207 goto error;
208 pos = crypto_rsa_parse_integer(pos, end, zero);
209 if (pos == NULL || bignum_cmp_d(zero, 0) != 0) {
210 wpa_printf(MSG_DEBUG, "RSA: Expected zero INTEGER in the "
211 "beginning of private key; not found");
212 bignum_deinit(zero);
213 goto error;
214 }
215 bignum_deinit(zero);
216
217 pos = crypto_rsa_parse_integer(pos, end, key->n);
218 pos = crypto_rsa_parse_integer(pos, end, key->e);
219 pos = crypto_rsa_parse_integer(pos, end, key->d);
220 pos = crypto_rsa_parse_integer(pos, end, key->p);
221 pos = crypto_rsa_parse_integer(pos, end, key->q);
222 pos = crypto_rsa_parse_integer(pos, end, key->dmp1);
223 pos = crypto_rsa_parse_integer(pos, end, key->dmq1);
224 pos = crypto_rsa_parse_integer(pos, end, key->iqmp);
225
226 if (pos == NULL)
227 goto error;
228
229 if (pos != end) {
230 wpa_hexdump(MSG_DEBUG,
231 "RSA: Extra data in public key SEQUENCE",
232 pos, end - pos);
233 goto error;
234 }
235
236 return key;
237
238 error:
239 crypto_rsa_free(key);
240 return NULL;
241 }
242
243
244 /**
245 * crypto_rsa_get_modulus_len - Get the modulus length of the RSA key
246 * @key: RSA key
247 * Returns: Modulus length of the key
248 */
crypto_rsa_get_modulus_len(struct crypto_rsa_key * key)249 size_t crypto_rsa_get_modulus_len(struct crypto_rsa_key *key)
250 {
251 return bignum_get_unsigned_bin_len(key->n);
252 }
253
254
255 /**
256 * crypto_rsa_exptmod - RSA modular exponentiation
257 * @in: Input data
258 * @inlen: Input data length
259 * @out: Buffer for output data
260 * @outlen: Maximum size of the output buffer and used size on success
261 * @key: RSA key
262 * @use_private: 1 = Use RSA private key, 0 = Use RSA public key
263 * Returns: 0 on success, -1 on failure
264 */
crypto_rsa_exptmod(const u8 * in,size_t inlen,u8 * out,size_t * outlen,struct crypto_rsa_key * key,int use_private)265 int crypto_rsa_exptmod(const u8 *in, size_t inlen, u8 *out, size_t *outlen,
266 struct crypto_rsa_key *key, int use_private)
267 {
268 struct bignum *tmp, *a = NULL, *b = NULL;
269 int ret = -1;
270 size_t modlen;
271
272 if (use_private && !key->private_key)
273 return -1;
274
275 tmp = bignum_init();
276 if (tmp == NULL)
277 return -1;
278
279 if (bignum_set_unsigned_bin(tmp, in, inlen) < 0)
280 goto error;
281 if (bignum_cmp(key->n, tmp) < 0) {
282 /* Too large input value for the RSA key modulus */
283 goto error;
284 }
285
286 if (use_private) {
287 /*
288 * Decrypt (or sign) using Chinese remainder theorem to speed
289 * up calculation. This is equivalent to tmp = tmp^d mod n
290 * (which would require more CPU to calculate directly).
291 *
292 * dmp1 = (1/e) mod (p-1)
293 * dmq1 = (1/e) mod (q-1)
294 * iqmp = (1/q) mod p, where p > q
295 * m1 = c^dmp1 mod p
296 * m2 = c^dmq1 mod q
297 * h = q^-1 (m1 - m2) mod p
298 * m = m2 + hq
299 */
300 a = bignum_init();
301 b = bignum_init();
302 if (a == NULL || b == NULL)
303 goto error;
304
305 /* a = tmp^dmp1 mod p */
306 if (bignum_exptmod(tmp, key->dmp1, key->p, a) < 0)
307 goto error;
308
309 /* b = tmp^dmq1 mod q */
310 if (bignum_exptmod(tmp, key->dmq1, key->q, b) < 0)
311 goto error;
312
313 /* tmp = (a - b) * (1/q mod p) (mod p) */
314 if (bignum_sub(a, b, tmp) < 0 ||
315 bignum_mulmod(tmp, key->iqmp, key->p, tmp) < 0)
316 goto error;
317
318 /* tmp = b + q * tmp */
319 if (bignum_mul(tmp, key->q, tmp) < 0 ||
320 bignum_add(tmp, b, tmp) < 0)
321 goto error;
322 } else {
323 /* Encrypt (or verify signature) */
324 /* tmp = tmp^e mod N */
325 if (bignum_exptmod(tmp, key->e, key->n, tmp) < 0)
326 goto error;
327 }
328
329 modlen = crypto_rsa_get_modulus_len(key);
330 if (modlen > *outlen) {
331 *outlen = modlen;
332 goto error;
333 }
334
335 if (bignum_get_unsigned_bin_len(tmp) > modlen)
336 goto error; /* should never happen */
337
338 *outlen = modlen;
339 os_memset(out, 0, modlen);
340 if (bignum_get_unsigned_bin(
341 tmp, out +
342 (modlen - bignum_get_unsigned_bin_len(tmp)), NULL) < 0)
343 goto error;
344
345 ret = 0;
346
347 error:
348 bignum_deinit(tmp);
349 bignum_deinit(a);
350 bignum_deinit(b);
351 return ret;
352 }
353
354
355 /**
356 * crypto_rsa_free - Free RSA key
357 * @key: RSA key to be freed
358 *
359 * This function frees an RSA key imported with either
360 * crypto_rsa_import_public_key() or crypto_rsa_import_private_key().
361 */
crypto_rsa_free(struct crypto_rsa_key * key)362 void crypto_rsa_free(struct crypto_rsa_key *key)
363 {
364 if (key) {
365 bignum_deinit(key->n);
366 bignum_deinit(key->e);
367 bignum_deinit(key->d);
368 bignum_deinit(key->p);
369 bignum_deinit(key->q);
370 bignum_deinit(key->dmp1);
371 bignum_deinit(key->dmq1);
372 bignum_deinit(key->iqmp);
373 os_free(key);
374 }
375 }
376
