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1a4240f4 WL |
1 | /* Key type used to cache DNS lookups made by the kernel |
2 | * | |
9dfe1361 | 3 | * See Documentation/networking/dns_resolver.rst |
1a4240f4 WL |
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 | ||
1a4240f4 | 49 | /* |
d46d4942 | 50 | * Preparse instantiation data for a dns_resolver key. |
1a4240f4 | 51 | * |
bbb4c432 DH |
52 | * For normal hostname lookups, the data must be a NUL-terminated string, with |
53 | * the NUL char accounted in datalen. | |
1a4240f4 WL |
54 | * |
55 | * If the data contains a '#' characters, then we take the clause after each | |
56 | * one to be an option of the form 'key=value'. The actual data of interest is | |
57 | * the string leading up to the first '#'. For instance: | |
58 | * | |
59 | * "ip1,ip2,...#foo=bar" | |
bbb4c432 DH |
60 | * |
61 | * For server list requests, the data must begin with a NUL char and be | |
62 | * followed by a byte indicating the version of the data format. Version 1 | |
63 | * looks something like (note this is packed): | |
64 | * | |
65 | * u8 Non-string marker (ie. 0) | |
66 | * u8 Content (DNS_PAYLOAD_IS_*) | |
67 | * u8 Version (e.g. 1) | |
68 | * u8 Source of server list | |
69 | * u8 Lookup status of server list | |
70 | * u8 Number of servers | |
71 | * foreach-server { | |
72 | * __le16 Name length | |
73 | * __le16 Priority (as per SRV record, low first) | |
74 | * __le16 Weight (as per SRV record, higher first) | |
75 | * __le16 Port | |
76 | * u8 Source of address list | |
77 | * u8 Lookup status of address list | |
78 | * u8 Protocol (DNS_SERVER_PROTOCOL_*) | |
79 | * u8 Number of addresses | |
80 | * char[] Name (not NUL-terminated) | |
81 | * foreach-address { | |
82 | * u8 Family (DNS_ADDRESS_IS_*) | |
83 | * union { | |
84 | * u8[4] ipv4_addr | |
85 | * u8[16] ipv6_addr | |
86 | * } | |
87 | * } | |
88 | * } | |
89 | * | |
1a4240f4 WL |
90 | */ |
91 | static int | |
d46d4942 | 92 | dns_resolver_preparse(struct key_preparsed_payload *prep) |
1a4240f4 | 93 | { |
bbb4c432 | 94 | const struct dns_payload_header *bin; |
1a4240f4 | 95 | struct user_key_payload *upayload; |
4a2d7892 | 96 | unsigned long derrno; |
1a4240f4 | 97 | int ret; |
d46d4942 | 98 | int datalen = prep->datalen, result_len = 0; |
cf7f601c | 99 | const char *data = prep->data, *end, *opt; |
1a4240f4 | 100 | |
bbb4c432 DH |
101 | if (datalen <= 1 || !data) |
102 | return -EINVAL; | |
103 | ||
104 | if (data[0] == 0) { | |
105 | /* It may be a server list. */ | |
106 | if (datalen <= sizeof(*bin)) | |
107 | return -EINVAL; | |
108 | ||
109 | bin = (const struct dns_payload_header *)data; | |
110 | kenter("[%u,%u],%u", bin->content, bin->version, datalen); | |
111 | if (bin->content != DNS_PAYLOAD_IS_SERVER_LIST) { | |
112 | pr_warn_ratelimited( | |
113 | "dns_resolver: Unsupported content type (%u)\n", | |
114 | bin->content); | |
115 | return -EINVAL; | |
116 | } | |
117 | ||
118 | if (bin->version != 1) { | |
119 | pr_warn_ratelimited( | |
120 | "dns_resolver: Unsupported server list version (%u)\n", | |
121 | bin->version); | |
122 | return -EINVAL; | |
123 | } | |
124 | ||
125 | result_len = datalen; | |
126 | goto store_result; | |
127 | } | |
128 | ||
d46d4942 | 129 | kenter("'%*.*s',%u", datalen, datalen, data, datalen); |
1a4240f4 | 130 | |
bbb4c432 | 131 | if (!data || data[datalen - 1] != '\0') |
1a4240f4 WL |
132 | return -EINVAL; |
133 | datalen--; | |
134 | ||
135 | /* deal with any options embedded in the data */ | |
4a2d7892 | 136 | end = data + datalen; |
1a4240f4 WL |
137 | opt = memchr(data, '#', datalen); |
138 | if (!opt) { | |
4a2d7892 WL |
139 | /* no options: the entire data is the result */ |
140 | kdebug("no options"); | |
141 | result_len = datalen; | |
142 | } else { | |
143 | const char *next_opt; | |
144 | ||
145 | result_len = opt - data; | |
146 | opt++; | |
147 | kdebug("options: '%s'", opt); | |
148 | do { | |
c604cb76 | 149 | int opt_len, opt_nlen; |
4a2d7892 | 150 | const char *eq; |
c604cb76 | 151 | char optval[128]; |
4a2d7892 WL |
152 | |
153 | next_opt = memchr(opt, '#', end - opt) ?: end; | |
154 | opt_len = next_opt - opt; | |
c604cb76 | 155 | if (opt_len <= 0 || opt_len > sizeof(optval)) { |
9c438d7a EB |
156 | pr_warn_ratelimited("Invalid option length (%d) for dns_resolver key\n", |
157 | opt_len); | |
4a2d7892 WL |
158 | return -EINVAL; |
159 | } | |
160 | ||
c604cb76 EB |
161 | eq = memchr(opt, '=', opt_len); |
162 | if (eq) { | |
163 | opt_nlen = eq - opt; | |
164 | eq++; | |
165 | memcpy(optval, eq, next_opt - eq); | |
166 | optval[next_opt - eq] = '\0'; | |
167 | } else { | |
168 | opt_nlen = opt_len; | |
169 | optval[0] = '\0'; | |
170 | } | |
4a2d7892 | 171 | |
c604cb76 EB |
172 | kdebug("option '%*.*s' val '%s'", |
173 | opt_nlen, opt_nlen, opt, optval); | |
4a2d7892 WL |
174 | |
175 | /* see if it's an error number representing a DNS error | |
176 | * that's to be recorded as the result in this key */ | |
177 | if (opt_nlen == sizeof(DNS_ERRORNO_OPTION) - 1 && | |
178 | memcmp(opt, DNS_ERRORNO_OPTION, opt_nlen) == 0) { | |
179 | kdebug("dns error number option"); | |
4a2d7892 | 180 | |
c604cb76 | 181 | ret = kstrtoul(optval, 10, &derrno); |
4a2d7892 WL |
182 | if (ret < 0) |
183 | goto bad_option_value; | |
184 | ||
185 | if (derrno < 1 || derrno > 511) | |
186 | goto bad_option_value; | |
187 | ||
188 | kdebug("dns error no. = %lu", derrno); | |
146aa8b1 | 189 | prep->payload.data[dns_key_error] = ERR_PTR(-derrno); |
4a2d7892 WL |
190 | continue; |
191 | } | |
192 | ||
193 | bad_option_value: | |
9c438d7a EB |
194 | pr_warn_ratelimited("Option '%*.*s' to dns_resolver key: bad/missing value\n", |
195 | opt_nlen, opt_nlen, opt); | |
4a2d7892 WL |
196 | return -EINVAL; |
197 | } while (opt = next_opt + 1, opt < end); | |
1a4240f4 WL |
198 | } |
199 | ||
4a2d7892 WL |
200 | /* don't cache the result if we're caching an error saying there's no |
201 | * result */ | |
146aa8b1 DH |
202 | if (prep->payload.data[dns_key_error]) { |
203 | kleave(" = 0 [h_error %ld]", PTR_ERR(prep->payload.data[dns_key_error])); | |
4a2d7892 WL |
204 | return 0; |
205 | } | |
206 | ||
bbb4c432 | 207 | store_result: |
4a2d7892 | 208 | kdebug("store result"); |
d46d4942 | 209 | prep->quotalen = result_len; |
1a4240f4 WL |
210 | |
211 | upayload = kmalloc(sizeof(*upayload) + result_len + 1, GFP_KERNEL); | |
212 | if (!upayload) { | |
213 | kleave(" = -ENOMEM"); | |
214 | return -ENOMEM; | |
215 | } | |
216 | ||
217 | upayload->datalen = result_len; | |
218 | memcpy(upayload->data, data, result_len); | |
219 | upayload->data[result_len] = '\0'; | |
1a4240f4 | 220 | |
146aa8b1 | 221 | prep->payload.data[dns_key_data] = upayload; |
1a4240f4 WL |
222 | kleave(" = 0"); |
223 | return 0; | |
224 | } | |
225 | ||
d46d4942 DH |
226 | /* |
227 | * Clean up the preparse data | |
228 | */ | |
229 | static void dns_resolver_free_preparse(struct key_preparsed_payload *prep) | |
230 | { | |
231 | pr_devel("==>%s()\n", __func__); | |
232 | ||
146aa8b1 | 233 | kfree(prep->payload.data[dns_key_data]); |
d46d4942 DH |
234 | } |
235 | ||
1a4240f4 WL |
236 | /* |
237 | * The description is of the form "[<type>:]<domain_name>" | |
238 | * | |
239 | * The domain name may be a simple name or an absolute domain name (which | |
240 | * should end with a period). The domain name is case-independent. | |
241 | */ | |
0c903ab6 DH |
242 | static bool dns_resolver_cmp(const struct key *key, |
243 | const struct key_match_data *match_data) | |
1a4240f4 WL |
244 | { |
245 | int slen, dlen, ret = 0; | |
46291959 | 246 | const char *src = key->description, *dsp = match_data->raw_data; |
1a4240f4 WL |
247 | |
248 | kenter("%s,%s", src, dsp); | |
249 | ||
250 | if (!src || !dsp) | |
251 | goto no_match; | |
252 | ||
253 | if (strcasecmp(src, dsp) == 0) | |
254 | goto matched; | |
255 | ||
256 | slen = strlen(src); | |
257 | dlen = strlen(dsp); | |
258 | if (slen <= 0 || dlen <= 0) | |
259 | goto no_match; | |
260 | if (src[slen - 1] == '.') | |
261 | slen--; | |
262 | if (dsp[dlen - 1] == '.') | |
263 | dlen--; | |
264 | if (slen != dlen || strncasecmp(src, dsp, slen) != 0) | |
265 | goto no_match; | |
266 | ||
267 | matched: | |
268 | ret = 1; | |
269 | no_match: | |
270 | kleave(" = %d", ret); | |
271 | return ret; | |
272 | } | |
273 | ||
c06cfb08 DH |
274 | /* |
275 | * Preparse the match criterion. | |
276 | */ | |
277 | static int dns_resolver_match_preparse(struct key_match_data *match_data) | |
278 | { | |
279 | match_data->lookup_type = KEYRING_SEARCH_LOOKUP_ITERATE; | |
280 | match_data->cmp = dns_resolver_cmp; | |
281 | return 0; | |
282 | } | |
283 | ||
4a2d7892 WL |
284 | /* |
285 | * Describe a DNS key | |
286 | */ | |
287 | static void dns_resolver_describe(const struct key *key, struct seq_file *m) | |
288 | { | |
4a2d7892 | 289 | seq_puts(m, key->description); |
363b02da | 290 | if (key_is_positive(key)) { |
146aa8b1 DH |
291 | int err = PTR_ERR(key->payload.data[dns_key_error]); |
292 | ||
78b7280c DH |
293 | if (err) |
294 | seq_printf(m, ": %d", err); | |
295 | else | |
296 | seq_printf(m, ": %u", key->datalen); | |
297 | } | |
4a2d7892 WL |
298 | } |
299 | ||
1362fa07 DH |
300 | /* |
301 | * read the DNS data | |
302 | * - the key's semaphore is read-locked | |
303 | */ | |
304 | static long dns_resolver_read(const struct key *key, | |
d3ec10aa | 305 | char *buffer, size_t buflen) |
1362fa07 | 306 | { |
146aa8b1 DH |
307 | int err = PTR_ERR(key->payload.data[dns_key_error]); |
308 | ||
309 | if (err) | |
310 | return err; | |
1362fa07 DH |
311 | |
312 | return user_read(key, buffer, buflen); | |
313 | } | |
314 | ||
1a4240f4 WL |
315 | struct key_type key_type_dns_resolver = { |
316 | .name = "dns_resolver", | |
9b242610 | 317 | .flags = KEY_TYPE_NET_DOMAIN, |
d46d4942 DH |
318 | .preparse = dns_resolver_preparse, |
319 | .free_preparse = dns_resolver_free_preparse, | |
320 | .instantiate = generic_key_instantiate, | |
c06cfb08 | 321 | .match_preparse = dns_resolver_match_preparse, |
1a4240f4 WL |
322 | .revoke = user_revoke, |
323 | .destroy = user_destroy, | |
4a2d7892 | 324 | .describe = dns_resolver_describe, |
1362fa07 | 325 | .read = dns_resolver_read, |
1a4240f4 WL |
326 | }; |
327 | ||
328 | static int __init init_dns_resolver(void) | |
329 | { | |
330 | struct cred *cred; | |
331 | struct key *keyring; | |
332 | int ret; | |
333 | ||
1a4240f4 WL |
334 | /* create an override credential set with a special thread keyring in |
335 | * which DNS requests are cached | |
336 | * | |
337 | * this is used to prevent malicious redirections from being installed | |
338 | * with add_key(). | |
339 | */ | |
5a17f040 | 340 | cred = prepare_kernel_cred(&init_task); |
1a4240f4 WL |
341 | if (!cred) |
342 | return -ENOMEM; | |
343 | ||
2a74dbb9 LT |
344 | keyring = keyring_alloc(".dns_resolver", |
345 | GLOBAL_ROOT_UID, GLOBAL_ROOT_GID, cred, | |
028db3e2 LT |
346 | (KEY_POS_ALL & ~KEY_POS_SETATTR) | |
347 | KEY_USR_VIEW | KEY_USR_READ, | |
5ac7eace | 348 | KEY_ALLOC_NOT_IN_QUOTA, NULL, NULL); |
1a4240f4 WL |
349 | if (IS_ERR(keyring)) { |
350 | ret = PTR_ERR(keyring); | |
351 | goto failed_put_cred; | |
352 | } | |
353 | ||
1a4240f4 WL |
354 | ret = register_key_type(&key_type_dns_resolver); |
355 | if (ret < 0) | |
356 | goto failed_put_key; | |
357 | ||
358 | /* instruct request_key() to use this special keyring as a cache for | |
359 | * the results it looks up */ | |
700920eb | 360 | set_bit(KEY_FLAG_ROOT_CAN_CLEAR, &keyring->flags); |
1a4240f4 WL |
361 | cred->thread_keyring = keyring; |
362 | cred->jit_keyring = KEY_REQKEY_DEFL_THREAD_KEYRING; | |
363 | dns_resolver_cache = cred; | |
364 | ||
365 | kdebug("DNS resolver keyring: %d\n", key_serial(keyring)); | |
366 | return 0; | |
367 | ||
368 | failed_put_key: | |
369 | key_put(keyring); | |
370 | failed_put_cred: | |
371 | put_cred(cred); | |
372 | return ret; | |
373 | } | |
374 | ||
375 | static void __exit exit_dns_resolver(void) | |
376 | { | |
377 | key_revoke(dns_resolver_cache->thread_keyring); | |
378 | unregister_key_type(&key_type_dns_resolver); | |
379 | put_cred(dns_resolver_cache); | |
1a4240f4 WL |
380 | } |
381 | ||
382 | module_init(init_dns_resolver) | |
383 | module_exit(exit_dns_resolver) | |
384 | MODULE_LICENSE("GPL"); |