1 /*
2 * PKCS #1 (RSA Encryption)
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 "crypto/crypto.h"
13 #include "rsa.h"
14 #include "asn1.h"
15 #include "pkcs1.h"
16
17
pkcs1_generate_encryption_block(u8 block_type,size_t modlen,const u8 * in,size_t inlen,u8 * out,size_t * outlen)18 static int pkcs1_generate_encryption_block(u8 block_type, size_t modlen,
19 const u8 *in, size_t inlen,
20 u8 *out, size_t *outlen)
21 {
22 size_t ps_len;
23 u8 *pos;
24
25 /*
26 * PKCS #1 v1.5, 8.1:
27 *
28 * EB = 00 || BT || PS || 00 || D
29 * BT = 00 or 01 for private-key operation; 02 for public-key operation
30 * PS = k-3-||D||; at least eight octets
31 * (BT=0: PS=0x00, BT=1: PS=0xff, BT=2: PS=pseudorandom non-zero)
32 * k = length of modulus in octets (modlen)
33 */
34
35 if (modlen < 12 || modlen > *outlen || inlen > modlen - 11) {
36 wpa_printf(MSG_DEBUG, "PKCS #1: %s - Invalid buffer "
37 "lengths (modlen=%lu outlen=%lu inlen=%lu)",
38 __func__, (unsigned long) modlen,
39 (unsigned long) *outlen,
40 (unsigned long) inlen);
41 return -1;
42 }
43
44 pos = out;
45 *pos++ = 0x00;
46 *pos++ = block_type; /* BT */
47 ps_len = modlen - inlen - 3;
48 switch (block_type) {
49 case 0:
50 os_memset(pos, 0x00, ps_len);
51 pos += ps_len;
52 break;
53 case 1:
54 os_memset(pos, 0xff, ps_len);
55 pos += ps_len;
56 break;
57 case 2:
58 if (os_get_random(pos, ps_len) < 0) {
59 wpa_printf(MSG_DEBUG, "PKCS #1: %s - Failed to get "
60 "random data for PS", __func__);
61 return -1;
62 }
63 while (ps_len--) {
64 if (*pos == 0x00)
65 *pos = 0x01;
66 pos++;
67 }
68 break;
69 default:
70 wpa_printf(MSG_DEBUG, "PKCS #1: %s - Unsupported block type "
71 "%d", __func__, block_type);
72 return -1;
73 }
74 *pos++ = 0x00;
75 os_memcpy(pos, in, inlen); /* D */
76
77 return 0;
78 }
79
80
pkcs1_encrypt(int block_type,struct crypto_rsa_key * key,int use_private,const u8 * in,size_t inlen,u8 * out,size_t * outlen)81 int pkcs1_encrypt(int block_type, struct crypto_rsa_key *key,
82 int use_private, const u8 *in, size_t inlen,
83 u8 *out, size_t *outlen)
84 {
85 size_t modlen;
86
87 modlen = crypto_rsa_get_modulus_len(key);
88
89 if (pkcs1_generate_encryption_block(block_type, modlen, in, inlen,
90 out, outlen) < 0)
91 return -1;
92
93 return crypto_rsa_exptmod(out, modlen, out, outlen, key, use_private);
94 }
95
96
pkcs1_v15_private_key_decrypt(struct crypto_rsa_key * key,const u8 * in,size_t inlen,u8 * out,size_t * outlen)97 int pkcs1_v15_private_key_decrypt(struct crypto_rsa_key *key,
98 const u8 *in, size_t inlen,
99 u8 *out, size_t *outlen)
100 {
101 int res;
102 u8 *pos, *end;
103
104 res = crypto_rsa_exptmod(in, inlen, out, outlen, key, 1);
105 if (res)
106 return res;
107
108 if (*outlen < 2 || out[0] != 0 || out[1] != 2)
109 return -1;
110
111 /* Skip PS (pseudorandom non-zero octets) */
112 pos = out + 2;
113 end = out + *outlen;
114 while (*pos && pos < end)
115 pos++;
116 if (pos == end)
117 return -1;
118 if (pos - out - 2 < 8) {
119 /* PKCS #1 v1.5, 8.1: At least eight octets long PS */
120 wpa_printf(MSG_INFO, "LibTomCrypt: Too short padding");
121 return -1;
122 }
123 pos++;
124
125 *outlen -= pos - out;
126
127 /* Strip PKCS #1 header */
128 os_memmove(out, pos, *outlen);
129
130 return 0;
131 }
132
133
pkcs1_decrypt_public_key(struct crypto_rsa_key * key,const u8 * crypt,size_t crypt_len,u8 * plain,size_t * plain_len)134 int pkcs1_decrypt_public_key(struct crypto_rsa_key *key,
135 const u8 *crypt, size_t crypt_len,
136 u8 *plain, size_t *plain_len)
137 {
138 size_t len;
139 u8 *pos;
140
141 len = *plain_len;
142 if (crypto_rsa_exptmod(crypt, crypt_len, plain, &len, key, 0) < 0)
143 return -1;
144
145 /*
146 * PKCS #1 v1.5, 8.1:
147 *
148 * EB = 00 || BT || PS || 00 || D
149 * BT = 00 or 01
150 * PS = k-3-||D|| times (00 if BT=00) or (FF if BT=01)
151 * k = length of modulus in octets
152 *
153 * Based on 10.1.3, "The block type shall be 01" for a signature.
154 */
155
156 if (len < 3 + 8 + 16 /* min hash len */ ||
157 plain[0] != 0x00 || plain[1] != 0x01) {
158 wpa_printf(MSG_INFO, "LibTomCrypt: Invalid signature EB "
159 "structure");
160 return -1;
161 }
162
163 pos = plain + 3;
164 /* BT = 01 */
165 if (plain[2] != 0xff) {
166 wpa_printf(MSG_INFO, "LibTomCrypt: Invalid signature "
167 "PS (BT=01)");
168 return -1;
169 }
170 while (pos < plain + len && *pos == 0xff)
171 pos++;
172
173 if (pos - plain - 2 < 8) {
174 /* PKCS #1 v1.5, 8.1: At least eight octets long PS */
175 wpa_printf(MSG_INFO, "LibTomCrypt: Too short signature "
176 "padding");
177 return -1;
178 }
179
180 if (pos + 16 /* min hash len */ >= plain + len || *pos != 0x00) {
181 wpa_printf(MSG_INFO, "LibTomCrypt: Invalid signature EB "
182 "structure (2)");
183 return -1;
184 }
185 pos++;
186 len -= pos - plain;
187
188 /* Strip PKCS #1 header */
189 os_memmove(plain, pos, len);
190 *plain_len = len;
191
192 return 0;
193 }
194
195
pkcs1_v15_sig_ver(struct crypto_public_key * pk,const u8 * s,size_t s_len,const struct asn1_oid * hash_alg,const u8 * hash,size_t hash_len)196 int pkcs1_v15_sig_ver(struct crypto_public_key *pk,
197 const u8 *s, size_t s_len,
198 const struct asn1_oid *hash_alg,
199 const u8 *hash, size_t hash_len)
200 {
201 int res;
202 u8 *decrypted;
203 size_t decrypted_len;
204 const u8 *pos, *end, *next, *da_end;
205 struct asn1_hdr hdr;
206 struct asn1_oid oid;
207
208 decrypted = os_malloc(s_len);
209 if (decrypted == NULL)
210 return -1;
211 decrypted_len = s_len;
212 res = crypto_public_key_decrypt_pkcs1(pk, s, s_len, decrypted,
213 &decrypted_len);
214 if (res < 0) {
215 wpa_printf(MSG_INFO, "PKCS #1: RSA decrypt failed");
216 os_free(decrypted);
217 return -1;
218 }
219 wpa_hexdump(MSG_DEBUG, "Decrypted(S)", decrypted, decrypted_len);
220
221 /*
222 * PKCS #1 v1.5, 10.1.2:
223 *
224 * DigestInfo ::= SEQUENCE {
225 * digestAlgorithm DigestAlgorithmIdentifier,
226 * digest Digest
227 * }
228 *
229 * DigestAlgorithmIdentifier ::= AlgorithmIdentifier
230 *
231 * Digest ::= OCTET STRING
232 *
233 */
234 if (asn1_get_next(decrypted, decrypted_len, &hdr) < 0 ||
235 hdr.class != ASN1_CLASS_UNIVERSAL ||
236 hdr.tag != ASN1_TAG_SEQUENCE) {
237 wpa_printf(MSG_DEBUG,
238 "PKCS #1: Expected SEQUENCE (DigestInfo) - found class %d tag 0x%x",
239 hdr.class, hdr.tag);
240 os_free(decrypted);
241 return -1;
242 }
243 wpa_hexdump(MSG_MSGDUMP, "PKCS #1: DigestInfo",
244 hdr.payload, hdr.length);
245
246 pos = hdr.payload;
247 end = pos + hdr.length;
248
249 /*
250 * X.509:
251 * AlgorithmIdentifier ::= SEQUENCE {
252 * algorithm OBJECT IDENTIFIER,
253 * parameters ANY DEFINED BY algorithm OPTIONAL
254 * }
255 */
256
257 if (asn1_get_next(pos, end - pos, &hdr) < 0 ||
258 hdr.class != ASN1_CLASS_UNIVERSAL ||
259 hdr.tag != ASN1_TAG_SEQUENCE) {
260 wpa_printf(MSG_DEBUG,
261 "PKCS #1: Expected SEQUENCE (AlgorithmIdentifier) - found class %d tag 0x%x",
262 hdr.class, hdr.tag);
263 os_free(decrypted);
264 return -1;
265 }
266 wpa_hexdump(MSG_MSGDUMP, "PKCS #1: DigestAlgorithmIdentifier",
267 hdr.payload, hdr.length);
268 da_end = hdr.payload + hdr.length;
269
270 if (asn1_get_oid(hdr.payload, hdr.length, &oid, &next)) {
271 wpa_printf(MSG_DEBUG,
272 "PKCS #1: Failed to parse digestAlgorithm");
273 os_free(decrypted);
274 return -1;
275 }
276 wpa_hexdump(MSG_MSGDUMP, "PKCS #1: Digest algorithm parameters",
277 next, da_end - next);
278
279 /*
280 * RFC 5754: The correct encoding for the SHA2 algorithms would be to
281 * omit the parameters, but there are implementation that encode these
282 * as a NULL element. Allow these two cases and reject anything else.
283 */
284 if (da_end > next &&
285 (asn1_get_next(next, da_end - next, &hdr) < 0 ||
286 !asn1_is_null(&hdr) ||
287 hdr.payload + hdr.length != da_end)) {
288 wpa_printf(MSG_DEBUG,
289 "PKCS #1: Unexpected digest algorithm parameters");
290 os_free(decrypted);
291 return -1;
292 }
293
294 if (!asn1_oid_equal(&oid, hash_alg)) {
295 char txt[100], txt2[100];
296 asn1_oid_to_str(&oid, txt, sizeof(txt));
297 asn1_oid_to_str(hash_alg, txt2, sizeof(txt2));
298 wpa_printf(MSG_DEBUG,
299 "PKCS #1: Hash alg OID mismatch: was %s, expected %s",
300 txt, txt2);
301 os_free(decrypted);
302 return -1;
303 }
304
305 /* Digest ::= OCTET STRING */
306 pos = da_end;
307 end = decrypted + decrypted_len;
308
309 if (asn1_get_next(pos, end - pos, &hdr) < 0 ||
310 hdr.class != ASN1_CLASS_UNIVERSAL ||
311 hdr.tag != ASN1_TAG_OCTETSTRING) {
312 wpa_printf(MSG_DEBUG,
313 "PKCS #1: Expected OCTETSTRING (Digest) - found class %d tag 0x%x",
314 hdr.class, hdr.tag);
315 os_free(decrypted);
316 return -1;
317 }
318 wpa_hexdump(MSG_MSGDUMP, "PKCS #1: Decrypted Digest",
319 hdr.payload, hdr.length);
320
321 if (hdr.length != hash_len ||
322 os_memcmp_const(hdr.payload, hash, hdr.length) != 0) {
323 wpa_printf(MSG_INFO, "PKCS #1: Digest value does not match calculated hash");
324 os_free(decrypted);
325 return -1;
326 }
327
328 os_free(decrypted);
329
330 if (hdr.payload + hdr.length != end) {
331 wpa_printf(MSG_INFO,
332 "PKCS #1: Extra data after signature - reject");
333
334 wpa_hexdump(MSG_DEBUG, "PKCS #1: Extra data",
335 hdr.payload + hdr.length,
336 end - hdr.payload - hdr.length);
337 return -1;
338 }
339
340 return 0;
341 }
342