Commit | Line | Data |
---|---|---|
1a4240f4 WL |
1 | /* Key type used to cache DNS lookups made by the kernel |
2 | * | |
3 | * See Documentation/networking/dns_resolver.txt | |
4 | * | |
5 | * Copyright (c) 2007 Igor Mammedov | |
6 | * Author(s): Igor Mammedov (niallain@gmail.com) | |
7 | * Steve French (sfrench@us.ibm.com) | |
8 | * Wang Lei (wang840925@gmail.com) | |
9 | * David Howells (dhowells@redhat.com) | |
10 | * | |
11 | * This library is free software; you can redistribute it and/or modify | |
12 | * it under the terms of the GNU Lesser General Public License as published | |
13 | * by the Free Software Foundation; either version 2.1 of the License, or | |
14 | * (at your option) any later version. | |
15 | * | |
16 | * This library is distributed in the hope that it will be useful, | |
17 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
18 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See | |
19 | * the GNU Lesser General Public License for more details. | |
20 | * | |
21 | * You should have received a copy of the GNU Lesser General Public License | |
c057b190 | 22 | * along with this library; if not, see <http://www.gnu.org/licenses/>. |
1a4240f4 WL |
23 | */ |
24 | #include <linux/module.h> | |
25 | #include <linux/moduleparam.h> | |
26 | #include <linux/slab.h> | |
27 | #include <linux/string.h> | |
28 | #include <linux/kernel.h> | |
29 | #include <linux/keyctl.h> | |
af352fe9 | 30 | #include <linux/err.h> |
4a2d7892 | 31 | #include <linux/seq_file.h> |
bbb4c432 | 32 | #include <linux/dns_resolver.h> |
1a4240f4 WL |
33 | #include <keys/dns_resolver-type.h> |
34 | #include <keys/user-type.h> | |
35 | #include "internal.h" | |
36 | ||
37 | MODULE_DESCRIPTION("DNS Resolver"); | |
38 | MODULE_AUTHOR("Wang Lei"); | |
39 | MODULE_LICENSE("GPL"); | |
40 | ||
95c96174 | 41 | unsigned int dns_resolver_debug; |
d6444062 | 42 | module_param_named(debug, dns_resolver_debug, uint, 0644); |
1a4240f4 WL |
43 | MODULE_PARM_DESC(debug, "DNS Resolver debugging mask"); |
44 | ||
45 | const struct cred *dns_resolver_cache; | |
46 | ||
4a2d7892 WL |
47 | #define DNS_ERRORNO_OPTION "dnserror" |
48 | ||
2e12256b DH |
49 | static struct key_acl dns_keyring_acl = { |
50 | .usage = REFCOUNT_INIT(1), | |
51 | .nr_ace = 2, | |
52 | .aces = { | |
53 | KEY_POSSESSOR_ACE(KEY_ACE_SEARCH | KEY_ACE_WRITE), | |
54 | KEY_OWNER_ACE(KEY_ACE_VIEW | KEY_ACE_READ | KEY_ACE_CLEAR), | |
55 | } | |
56 | }; | |
57 | ||
1a4240f4 | 58 | /* |
d46d4942 | 59 | * Preparse instantiation data for a dns_resolver key. |
1a4240f4 | 60 | * |
bbb4c432 DH |
61 | * For normal hostname lookups, the data must be a NUL-terminated string, with |
62 | * the NUL char accounted in datalen. | |
1a4240f4 WL |
63 | * |
64 | * If the data contains a '#' characters, then we take the clause after each | |
65 | * one to be an option of the form 'key=value'. The actual data of interest is | |
66 | * the string leading up to the first '#'. For instance: | |
67 | * | |
68 | * "ip1,ip2,...#foo=bar" | |
bbb4c432 DH |
69 | * |
70 | * For server list requests, the data must begin with a NUL char and be | |
71 | * followed by a byte indicating the version of the data format. Version 1 | |
72 | * looks something like (note this is packed): | |
73 | * | |
74 | * u8 Non-string marker (ie. 0) | |
75 | * u8 Content (DNS_PAYLOAD_IS_*) | |
76 | * u8 Version (e.g. 1) | |
77 | * u8 Source of server list | |
78 | * u8 Lookup status of server list | |
79 | * u8 Number of servers | |
80 | * foreach-server { | |
81 | * __le16 Name length | |
82 | * __le16 Priority (as per SRV record, low first) | |
83 | * __le16 Weight (as per SRV record, higher first) | |
84 | * __le16 Port | |
85 | * u8 Source of address list | |
86 | * u8 Lookup status of address list | |
87 | * u8 Protocol (DNS_SERVER_PROTOCOL_*) | |
88 | * u8 Number of addresses | |
89 | * char[] Name (not NUL-terminated) | |
90 | * foreach-address { | |
91 | * u8 Family (DNS_ADDRESS_IS_*) | |
92 | * union { | |
93 | * u8[4] ipv4_addr | |
94 | * u8[16] ipv6_addr | |
95 | * } | |
96 | * } | |
97 | * } | |
98 | * | |
1a4240f4 WL |
99 | */ |
100 | static int | |
d46d4942 | 101 | dns_resolver_preparse(struct key_preparsed_payload *prep) |
1a4240f4 | 102 | { |
bbb4c432 | 103 | const struct dns_payload_header *bin; |
1a4240f4 | 104 | struct user_key_payload *upayload; |
4a2d7892 | 105 | unsigned long derrno; |
1a4240f4 | 106 | int ret; |
d46d4942 | 107 | int datalen = prep->datalen, result_len = 0; |
cf7f601c | 108 | const char *data = prep->data, *end, *opt; |
1a4240f4 | 109 | |
bbb4c432 DH |
110 | if (datalen <= 1 || !data) |
111 | return -EINVAL; | |
112 | ||
113 | if (data[0] == 0) { | |
114 | /* It may be a server list. */ | |
115 | if (datalen <= sizeof(*bin)) | |
116 | return -EINVAL; | |
117 | ||
118 | bin = (const struct dns_payload_header *)data; | |
119 | kenter("[%u,%u],%u", bin->content, bin->version, datalen); | |
120 | if (bin->content != DNS_PAYLOAD_IS_SERVER_LIST) { | |
121 | pr_warn_ratelimited( | |
122 | "dns_resolver: Unsupported content type (%u)\n", | |
123 | bin->content); | |
124 | return -EINVAL; | |
125 | } | |
126 | ||
127 | if (bin->version != 1) { | |
128 | pr_warn_ratelimited( | |
129 | "dns_resolver: Unsupported server list version (%u)\n", | |
130 | bin->version); | |
131 | return -EINVAL; | |
132 | } | |
133 | ||
134 | result_len = datalen; | |
135 | goto store_result; | |
136 | } | |
137 | ||
d46d4942 | 138 | kenter("'%*.*s',%u", datalen, datalen, data, datalen); |
1a4240f4 | 139 | |
bbb4c432 | 140 | if (!data || data[datalen - 1] != '\0') |
1a4240f4 WL |
141 | return -EINVAL; |
142 | datalen--; | |
143 | ||
144 | /* deal with any options embedded in the data */ | |
4a2d7892 | 145 | end = data + datalen; |
1a4240f4 WL |
146 | opt = memchr(data, '#', datalen); |
147 | if (!opt) { | |
4a2d7892 WL |
148 | /* no options: the entire data is the result */ |
149 | kdebug("no options"); | |
150 | result_len = datalen; | |
151 | } else { | |
152 | const char *next_opt; | |
153 | ||
154 | result_len = opt - data; | |
155 | opt++; | |
156 | kdebug("options: '%s'", opt); | |
157 | do { | |
c604cb76 | 158 | int opt_len, opt_nlen; |
4a2d7892 | 159 | const char *eq; |
c604cb76 | 160 | char optval[128]; |
4a2d7892 WL |
161 | |
162 | next_opt = memchr(opt, '#', end - opt) ?: end; | |
163 | opt_len = next_opt - opt; | |
c604cb76 | 164 | if (opt_len <= 0 || opt_len > sizeof(optval)) { |
9c438d7a EB |
165 | pr_warn_ratelimited("Invalid option length (%d) for dns_resolver key\n", |
166 | opt_len); | |
4a2d7892 WL |
167 | return -EINVAL; |
168 | } | |
169 | ||
c604cb76 EB |
170 | eq = memchr(opt, '=', opt_len); |
171 | if (eq) { | |
172 | opt_nlen = eq - opt; | |
173 | eq++; | |
174 | memcpy(optval, eq, next_opt - eq); | |
175 | optval[next_opt - eq] = '\0'; | |
176 | } else { | |
177 | opt_nlen = opt_len; | |
178 | optval[0] = '\0'; | |
179 | } | |
4a2d7892 | 180 | |
c604cb76 EB |
181 | kdebug("option '%*.*s' val '%s'", |
182 | opt_nlen, opt_nlen, opt, optval); | |
4a2d7892 WL |
183 | |
184 | /* see if it's an error number representing a DNS error | |
185 | * that's to be recorded as the result in this key */ | |
186 | if (opt_nlen == sizeof(DNS_ERRORNO_OPTION) - 1 && | |
187 | memcmp(opt, DNS_ERRORNO_OPTION, opt_nlen) == 0) { | |
188 | kdebug("dns error number option"); | |
4a2d7892 | 189 | |
c604cb76 | 190 | ret = kstrtoul(optval, 10, &derrno); |
4a2d7892 WL |
191 | if (ret < 0) |
192 | goto bad_option_value; | |
193 | ||
194 | if (derrno < 1 || derrno > 511) | |
195 | goto bad_option_value; | |
196 | ||
197 | kdebug("dns error no. = %lu", derrno); | |
146aa8b1 | 198 | prep->payload.data[dns_key_error] = ERR_PTR(-derrno); |
4a2d7892 WL |
199 | continue; |
200 | } | |
201 | ||
202 | bad_option_value: | |
9c438d7a EB |
203 | pr_warn_ratelimited("Option '%*.*s' to dns_resolver key: bad/missing value\n", |
204 | opt_nlen, opt_nlen, opt); | |
4a2d7892 WL |
205 | return -EINVAL; |
206 | } while (opt = next_opt + 1, opt < end); | |
1a4240f4 WL |
207 | } |
208 | ||
4a2d7892 WL |
209 | /* don't cache the result if we're caching an error saying there's no |
210 | * result */ | |
146aa8b1 DH |
211 | if (prep->payload.data[dns_key_error]) { |
212 | kleave(" = 0 [h_error %ld]", PTR_ERR(prep->payload.data[dns_key_error])); | |
4a2d7892 WL |
213 | return 0; |
214 | } | |
215 | ||
bbb4c432 | 216 | store_result: |
4a2d7892 | 217 | kdebug("store result"); |
d46d4942 | 218 | prep->quotalen = result_len; |
1a4240f4 WL |
219 | |
220 | upayload = kmalloc(sizeof(*upayload) + result_len + 1, GFP_KERNEL); | |
221 | if (!upayload) { | |
222 | kleave(" = -ENOMEM"); | |
223 | return -ENOMEM; | |
224 | } | |
225 | ||
226 | upayload->datalen = result_len; | |
227 | memcpy(upayload->data, data, result_len); | |
228 | upayload->data[result_len] = '\0'; | |
1a4240f4 | 229 | |
146aa8b1 | 230 | prep->payload.data[dns_key_data] = upayload; |
1a4240f4 WL |
231 | kleave(" = 0"); |
232 | return 0; | |
233 | } | |
234 | ||
d46d4942 DH |
235 | /* |
236 | * Clean up the preparse data | |
237 | */ | |
238 | static void dns_resolver_free_preparse(struct key_preparsed_payload *prep) | |
239 | { | |
240 | pr_devel("==>%s()\n", __func__); | |
241 | ||
146aa8b1 | 242 | kfree(prep->payload.data[dns_key_data]); |
d46d4942 DH |
243 | } |
244 | ||
1a4240f4 WL |
245 | /* |
246 | * The description is of the form "[<type>:]<domain_name>" | |
247 | * | |
248 | * The domain name may be a simple name or an absolute domain name (which | |
249 | * should end with a period). The domain name is case-independent. | |
250 | */ | |
0c903ab6 DH |
251 | static bool dns_resolver_cmp(const struct key *key, |
252 | const struct key_match_data *match_data) | |
1a4240f4 WL |
253 | { |
254 | int slen, dlen, ret = 0; | |
46291959 | 255 | const char *src = key->description, *dsp = match_data->raw_data; |
1a4240f4 WL |
256 | |
257 | kenter("%s,%s", src, dsp); | |
258 | ||
259 | if (!src || !dsp) | |
260 | goto no_match; | |
261 | ||
262 | if (strcasecmp(src, dsp) == 0) | |
263 | goto matched; | |
264 | ||
265 | slen = strlen(src); | |
266 | dlen = strlen(dsp); | |
267 | if (slen <= 0 || dlen <= 0) | |
268 | goto no_match; | |
269 | if (src[slen - 1] == '.') | |
270 | slen--; | |
271 | if (dsp[dlen - 1] == '.') | |
272 | dlen--; | |
273 | if (slen != dlen || strncasecmp(src, dsp, slen) != 0) | |
274 | goto no_match; | |
275 | ||
276 | matched: | |
277 | ret = 1; | |
278 | no_match: | |
279 | kleave(" = %d", ret); | |
280 | return ret; | |
281 | } | |
282 | ||
c06cfb08 DH |
283 | /* |
284 | * Preparse the match criterion. | |
285 | */ | |
286 | static int dns_resolver_match_preparse(struct key_match_data *match_data) | |
287 | { | |
288 | match_data->lookup_type = KEYRING_SEARCH_LOOKUP_ITERATE; | |
289 | match_data->cmp = dns_resolver_cmp; | |
290 | return 0; | |
291 | } | |
292 | ||
4a2d7892 WL |
293 | /* |
294 | * Describe a DNS key | |
295 | */ | |
296 | static void dns_resolver_describe(const struct key *key, struct seq_file *m) | |
297 | { | |
4a2d7892 | 298 | seq_puts(m, key->description); |
363b02da | 299 | if (key_is_positive(key)) { |
146aa8b1 DH |
300 | int err = PTR_ERR(key->payload.data[dns_key_error]); |
301 | ||
78b7280c DH |
302 | if (err) |
303 | seq_printf(m, ": %d", err); | |
304 | else | |
305 | seq_printf(m, ": %u", key->datalen); | |
306 | } | |
4a2d7892 WL |
307 | } |
308 | ||
1362fa07 DH |
309 | /* |
310 | * read the DNS data | |
311 | * - the key's semaphore is read-locked | |
312 | */ | |
313 | static long dns_resolver_read(const struct key *key, | |
314 | char __user *buffer, size_t buflen) | |
315 | { | |
146aa8b1 DH |
316 | int err = PTR_ERR(key->payload.data[dns_key_error]); |
317 | ||
318 | if (err) | |
319 | return err; | |
1362fa07 DH |
320 | |
321 | return user_read(key, buffer, buflen); | |
322 | } | |
323 | ||
1a4240f4 WL |
324 | struct key_type key_type_dns_resolver = { |
325 | .name = "dns_resolver", | |
9b242610 | 326 | .flags = KEY_TYPE_NET_DOMAIN, |
d46d4942 DH |
327 | .preparse = dns_resolver_preparse, |
328 | .free_preparse = dns_resolver_free_preparse, | |
329 | .instantiate = generic_key_instantiate, | |
c06cfb08 | 330 | .match_preparse = dns_resolver_match_preparse, |
1a4240f4 WL |
331 | .revoke = user_revoke, |
332 | .destroy = user_destroy, | |
4a2d7892 | 333 | .describe = dns_resolver_describe, |
1362fa07 | 334 | .read = dns_resolver_read, |
1a4240f4 WL |
335 | }; |
336 | ||
337 | static int __init init_dns_resolver(void) | |
338 | { | |
339 | struct cred *cred; | |
340 | struct key *keyring; | |
341 | int ret; | |
342 | ||
1a4240f4 WL |
343 | /* create an override credential set with a special thread keyring in |
344 | * which DNS requests are cached | |
345 | * | |
346 | * this is used to prevent malicious redirections from being installed | |
347 | * with add_key(). | |
348 | */ | |
349 | cred = prepare_kernel_cred(NULL); | |
350 | if (!cred) | |
351 | return -ENOMEM; | |
352 | ||
2a74dbb9 LT |
353 | keyring = keyring_alloc(".dns_resolver", |
354 | GLOBAL_ROOT_UID, GLOBAL_ROOT_GID, cred, | |
2e12256b | 355 | &dns_keyring_acl, |
5ac7eace | 356 | KEY_ALLOC_NOT_IN_QUOTA, NULL, NULL); |
1a4240f4 WL |
357 | if (IS_ERR(keyring)) { |
358 | ret = PTR_ERR(keyring); | |
359 | goto failed_put_cred; | |
360 | } | |
361 | ||
1a4240f4 WL |
362 | ret = register_key_type(&key_type_dns_resolver); |
363 | if (ret < 0) | |
364 | goto failed_put_key; | |
365 | ||
366 | /* instruct request_key() to use this special keyring as a cache for | |
367 | * the results it looks up */ | |
700920eb | 368 | set_bit(KEY_FLAG_ROOT_CAN_CLEAR, &keyring->flags); |
1a4240f4 WL |
369 | cred->thread_keyring = keyring; |
370 | cred->jit_keyring = KEY_REQKEY_DEFL_THREAD_KEYRING; | |
371 | dns_resolver_cache = cred; | |
372 | ||
373 | kdebug("DNS resolver keyring: %d\n", key_serial(keyring)); | |
374 | return 0; | |
375 | ||
376 | failed_put_key: | |
377 | key_put(keyring); | |
378 | failed_put_cred: | |
379 | put_cred(cred); | |
380 | return ret; | |
381 | } | |
382 | ||
383 | static void __exit exit_dns_resolver(void) | |
384 | { | |
385 | key_revoke(dns_resolver_cache->thread_keyring); | |
386 | unregister_key_type(&key_type_dns_resolver); | |
387 | put_cred(dns_resolver_cache); | |
1a4240f4 WL |
388 | } |
389 | ||
390 | module_init(init_dns_resolver) | |
391 | module_exit(exit_dns_resolver) | |
392 | MODULE_LICENSE("GPL"); |