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 wpa_hexdump_key(MSG_DEBUG, "Signature EB", plain, len);
161 return -1;
162 }
163
164 pos = plain + 3;
165 /* BT = 01 */
166 if (plain[2] != 0xff) {
167 wpa_printf(MSG_INFO, "LibTomCrypt: Invalid signature "
168 "PS (BT=01)");
169 wpa_hexdump_key(MSG_DEBUG, "Signature EB", plain, len);
170 return -1;
171 }
172 while (pos < plain + len && *pos == 0xff)
173 pos++;
174
175 if (pos - plain - 2 < 8) {
176 /* PKCS #1 v1.5, 8.1: At least eight octets long PS */
177 wpa_printf(MSG_INFO, "LibTomCrypt: Too short signature "
178 "padding");
179 wpa_hexdump_key(MSG_DEBUG, "Signature EB", plain, len);
180 return -1;
181 }
182
183 if (pos + 16 /* min hash len */ >= plain + len || *pos != 0x00) {
184 wpa_printf(MSG_INFO, "LibTomCrypt: Invalid signature EB "
185 "structure (2)");
186 wpa_hexdump_key(MSG_DEBUG, "Signature EB", plain, len);
187 return -1;
188 }
189 pos++;
190 len -= pos - plain;
191
192 /* Strip PKCS #1 header */
193 os_memmove(plain, pos, len);
194 *plain_len = len;
195
196 return 0;
197 }
198
199
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)200 int pkcs1_v15_sig_ver(struct crypto_public_key *pk,
201 const u8 *s, size_t s_len,
202 const struct asn1_oid *hash_alg,
203 const u8 *hash, size_t hash_len)
204 {
205 int res;
206 u8 *decrypted;
207 size_t decrypted_len;
208 const u8 *pos, *end, *next, *da_end;
209 struct asn1_hdr hdr;
210 struct asn1_oid oid;
211
212 decrypted = os_malloc(s_len);
213 if (decrypted == NULL)
214 return -1;
215 decrypted_len = s_len;
216 res = crypto_public_key_decrypt_pkcs1(pk, s, s_len, decrypted,
217 &decrypted_len);
218 if (res < 0) {
219 wpa_printf(MSG_INFO, "PKCS #1: RSA decrypt failed");
220 os_free(decrypted);
221 return -1;
222 }
223 wpa_hexdump(MSG_DEBUG, "Decrypted(S)", decrypted, decrypted_len);
224
225 /*
226 * PKCS #1 v1.5, 10.1.2:
227 *
228 * DigestInfo ::= SEQUENCE {
229 * digestAlgorithm DigestAlgorithmIdentifier,
230 * digest Digest
231 * }
232 *
233 * DigestAlgorithmIdentifier ::= AlgorithmIdentifier
234 *
235 * Digest ::= OCTET STRING
236 *
237 */
238 if (asn1_get_next(decrypted, decrypted_len, &hdr) < 0 ||
239 !asn1_is_sequence(&hdr)) {
240 asn1_unexpected(&hdr,
241 "PKCS #1: Expected SEQUENCE (DigestInfo)");
242 os_free(decrypted);
243 return -1;
244 }
245 wpa_hexdump(MSG_MSGDUMP, "PKCS #1: DigestInfo",
246 hdr.payload, hdr.length);
247
248 pos = hdr.payload;
249 end = pos + hdr.length;
250
251 /*
252 * X.509:
253 * AlgorithmIdentifier ::= SEQUENCE {
254 * algorithm OBJECT IDENTIFIER,
255 * parameters ANY DEFINED BY algorithm OPTIONAL
256 * }
257 */
258
259 if (asn1_get_next(pos, end - pos, &hdr) < 0 ||
260 !asn1_is_sequence(&hdr)) {
261 asn1_unexpected(&hdr,
262 "PKCS #1: Expected SEQUENCE (AlgorithmIdentifier)");
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
308 if (asn1_get_next(pos, end - pos, &hdr) < 0 ||
309 !asn1_is_octetstring(&hdr)) {
310 asn1_unexpected(&hdr,
311 "PKCS #1: Expected OCTETSTRING (Digest)");
312 os_free(decrypted);
313 return -1;
314 }
315 wpa_hexdump(MSG_MSGDUMP, "PKCS #1: Decrypted Digest",
316 hdr.payload, hdr.length);
317
318 if (hdr.length != hash_len ||
319 os_memcmp_const(hdr.payload, hash, hdr.length) != 0) {
320 wpa_printf(MSG_INFO, "PKCS #1: Digest value does not match calculated hash");
321 os_free(decrypted);
322 return -1;
323 }
324
325 os_free(decrypted);
326
327 if (hdr.payload + hdr.length != decrypted + decrypted_len) {
328 wpa_printf(MSG_INFO,
329 "PKCS #1: Extra data after signature - reject");
330
331 wpa_hexdump(MSG_DEBUG, "PKCS #1: Extra data",
332 hdr.payload + hdr.length,
333 decrypted + decrypted_len - hdr.payload -
334 hdr.length);
335 return -1;
336 }
337
338 return 0;
339 }
340
