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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> |
1a4240f4 WL |
32 | #include <keys/dns_resolver-type.h> |
33 | #include <keys/user-type.h> | |
34 | #include "internal.h" | |
35 | ||
36 | MODULE_DESCRIPTION("DNS Resolver"); | |
37 | MODULE_AUTHOR("Wang Lei"); | |
38 | MODULE_LICENSE("GPL"); | |
39 | ||
95c96174 | 40 | unsigned int dns_resolver_debug; |
d6444062 | 41 | module_param_named(debug, dns_resolver_debug, uint, 0644); |
1a4240f4 WL |
42 | MODULE_PARM_DESC(debug, "DNS Resolver debugging mask"); |
43 | ||
44 | const struct cred *dns_resolver_cache; | |
45 | ||
4a2d7892 WL |
46 | #define DNS_ERRORNO_OPTION "dnserror" |
47 | ||
1a4240f4 | 48 | /* |
d46d4942 | 49 | * Preparse instantiation data for a dns_resolver key. |
1a4240f4 WL |
50 | * |
51 | * The data must be a NUL-terminated string, with the NUL char accounted in | |
52 | * datalen. | |
53 | * | |
54 | * If the data contains a '#' characters, then we take the clause after each | |
55 | * one to be an option of the form 'key=value'. The actual data of interest is | |
56 | * the string leading up to the first '#'. For instance: | |
57 | * | |
58 | * "ip1,ip2,...#foo=bar" | |
59 | */ | |
60 | static int | |
d46d4942 | 61 | dns_resolver_preparse(struct key_preparsed_payload *prep) |
1a4240f4 WL |
62 | { |
63 | struct user_key_payload *upayload; | |
4a2d7892 | 64 | unsigned long derrno; |
1a4240f4 | 65 | int ret; |
d46d4942 | 66 | int datalen = prep->datalen, result_len = 0; |
cf7f601c | 67 | const char *data = prep->data, *end, *opt; |
1a4240f4 | 68 | |
d46d4942 | 69 | kenter("'%*.*s',%u", datalen, datalen, data, datalen); |
1a4240f4 WL |
70 | |
71 | if (datalen <= 1 || !data || data[datalen - 1] != '\0') | |
72 | return -EINVAL; | |
73 | datalen--; | |
74 | ||
75 | /* deal with any options embedded in the data */ | |
4a2d7892 | 76 | end = data + datalen; |
1a4240f4 WL |
77 | opt = memchr(data, '#', datalen); |
78 | if (!opt) { | |
4a2d7892 WL |
79 | /* no options: the entire data is the result */ |
80 | kdebug("no options"); | |
81 | result_len = datalen; | |
82 | } else { | |
83 | const char *next_opt; | |
84 | ||
85 | result_len = opt - data; | |
86 | opt++; | |
87 | kdebug("options: '%s'", opt); | |
88 | do { | |
c604cb76 | 89 | int opt_len, opt_nlen; |
4a2d7892 | 90 | const char *eq; |
c604cb76 | 91 | char optval[128]; |
4a2d7892 WL |
92 | |
93 | next_opt = memchr(opt, '#', end - opt) ?: end; | |
94 | opt_len = next_opt - opt; | |
c604cb76 | 95 | if (opt_len <= 0 || opt_len > sizeof(optval)) { |
9c438d7a EB |
96 | pr_warn_ratelimited("Invalid option length (%d) for dns_resolver key\n", |
97 | opt_len); | |
4a2d7892 WL |
98 | return -EINVAL; |
99 | } | |
100 | ||
c604cb76 EB |
101 | eq = memchr(opt, '=', opt_len); |
102 | if (eq) { | |
103 | opt_nlen = eq - opt; | |
104 | eq++; | |
105 | memcpy(optval, eq, next_opt - eq); | |
106 | optval[next_opt - eq] = '\0'; | |
107 | } else { | |
108 | opt_nlen = opt_len; | |
109 | optval[0] = '\0'; | |
110 | } | |
4a2d7892 | 111 | |
c604cb76 EB |
112 | kdebug("option '%*.*s' val '%s'", |
113 | opt_nlen, opt_nlen, opt, optval); | |
4a2d7892 WL |
114 | |
115 | /* see if it's an error number representing a DNS error | |
116 | * that's to be recorded as the result in this key */ | |
117 | if (opt_nlen == sizeof(DNS_ERRORNO_OPTION) - 1 && | |
118 | memcmp(opt, DNS_ERRORNO_OPTION, opt_nlen) == 0) { | |
119 | kdebug("dns error number option"); | |
4a2d7892 | 120 | |
c604cb76 | 121 | ret = kstrtoul(optval, 10, &derrno); |
4a2d7892 WL |
122 | if (ret < 0) |
123 | goto bad_option_value; | |
124 | ||
125 | if (derrno < 1 || derrno > 511) | |
126 | goto bad_option_value; | |
127 | ||
128 | kdebug("dns error no. = %lu", derrno); | |
146aa8b1 | 129 | prep->payload.data[dns_key_error] = ERR_PTR(-derrno); |
4a2d7892 WL |
130 | continue; |
131 | } | |
132 | ||
133 | bad_option_value: | |
9c438d7a EB |
134 | pr_warn_ratelimited("Option '%*.*s' to dns_resolver key: bad/missing value\n", |
135 | opt_nlen, opt_nlen, opt); | |
4a2d7892 WL |
136 | return -EINVAL; |
137 | } while (opt = next_opt + 1, opt < end); | |
1a4240f4 WL |
138 | } |
139 | ||
4a2d7892 WL |
140 | /* don't cache the result if we're caching an error saying there's no |
141 | * result */ | |
146aa8b1 DH |
142 | if (prep->payload.data[dns_key_error]) { |
143 | kleave(" = 0 [h_error %ld]", PTR_ERR(prep->payload.data[dns_key_error])); | |
4a2d7892 WL |
144 | return 0; |
145 | } | |
146 | ||
147 | kdebug("store result"); | |
d46d4942 | 148 | prep->quotalen = result_len; |
1a4240f4 WL |
149 | |
150 | upayload = kmalloc(sizeof(*upayload) + result_len + 1, GFP_KERNEL); | |
151 | if (!upayload) { | |
152 | kleave(" = -ENOMEM"); | |
153 | return -ENOMEM; | |
154 | } | |
155 | ||
156 | upayload->datalen = result_len; | |
157 | memcpy(upayload->data, data, result_len); | |
158 | upayload->data[result_len] = '\0'; | |
1a4240f4 | 159 | |
146aa8b1 | 160 | prep->payload.data[dns_key_data] = upayload; |
1a4240f4 WL |
161 | kleave(" = 0"); |
162 | return 0; | |
163 | } | |
164 | ||
d46d4942 DH |
165 | /* |
166 | * Clean up the preparse data | |
167 | */ | |
168 | static void dns_resolver_free_preparse(struct key_preparsed_payload *prep) | |
169 | { | |
170 | pr_devel("==>%s()\n", __func__); | |
171 | ||
146aa8b1 | 172 | kfree(prep->payload.data[dns_key_data]); |
d46d4942 DH |
173 | } |
174 | ||
1a4240f4 WL |
175 | /* |
176 | * The description is of the form "[<type>:]<domain_name>" | |
177 | * | |
178 | * The domain name may be a simple name or an absolute domain name (which | |
179 | * should end with a period). The domain name is case-independent. | |
180 | */ | |
0c903ab6 DH |
181 | static bool dns_resolver_cmp(const struct key *key, |
182 | const struct key_match_data *match_data) | |
1a4240f4 WL |
183 | { |
184 | int slen, dlen, ret = 0; | |
46291959 | 185 | const char *src = key->description, *dsp = match_data->raw_data; |
1a4240f4 WL |
186 | |
187 | kenter("%s,%s", src, dsp); | |
188 | ||
189 | if (!src || !dsp) | |
190 | goto no_match; | |
191 | ||
192 | if (strcasecmp(src, dsp) == 0) | |
193 | goto matched; | |
194 | ||
195 | slen = strlen(src); | |
196 | dlen = strlen(dsp); | |
197 | if (slen <= 0 || dlen <= 0) | |
198 | goto no_match; | |
199 | if (src[slen - 1] == '.') | |
200 | slen--; | |
201 | if (dsp[dlen - 1] == '.') | |
202 | dlen--; | |
203 | if (slen != dlen || strncasecmp(src, dsp, slen) != 0) | |
204 | goto no_match; | |
205 | ||
206 | matched: | |
207 | ret = 1; | |
208 | no_match: | |
209 | kleave(" = %d", ret); | |
210 | return ret; | |
211 | } | |
212 | ||
c06cfb08 DH |
213 | /* |
214 | * Preparse the match criterion. | |
215 | */ | |
216 | static int dns_resolver_match_preparse(struct key_match_data *match_data) | |
217 | { | |
218 | match_data->lookup_type = KEYRING_SEARCH_LOOKUP_ITERATE; | |
219 | match_data->cmp = dns_resolver_cmp; | |
220 | return 0; | |
221 | } | |
222 | ||
4a2d7892 WL |
223 | /* |
224 | * Describe a DNS key | |
225 | */ | |
226 | static void dns_resolver_describe(const struct key *key, struct seq_file *m) | |
227 | { | |
4a2d7892 | 228 | seq_puts(m, key->description); |
363b02da | 229 | if (key_is_positive(key)) { |
146aa8b1 DH |
230 | int err = PTR_ERR(key->payload.data[dns_key_error]); |
231 | ||
78b7280c DH |
232 | if (err) |
233 | seq_printf(m, ": %d", err); | |
234 | else | |
235 | seq_printf(m, ": %u", key->datalen); | |
236 | } | |
4a2d7892 WL |
237 | } |
238 | ||
1362fa07 DH |
239 | /* |
240 | * read the DNS data | |
241 | * - the key's semaphore is read-locked | |
242 | */ | |
243 | static long dns_resolver_read(const struct key *key, | |
244 | char __user *buffer, size_t buflen) | |
245 | { | |
146aa8b1 DH |
246 | int err = PTR_ERR(key->payload.data[dns_key_error]); |
247 | ||
248 | if (err) | |
249 | return err; | |
1362fa07 DH |
250 | |
251 | return user_read(key, buffer, buflen); | |
252 | } | |
253 | ||
1a4240f4 WL |
254 | struct key_type key_type_dns_resolver = { |
255 | .name = "dns_resolver", | |
d46d4942 DH |
256 | .preparse = dns_resolver_preparse, |
257 | .free_preparse = dns_resolver_free_preparse, | |
258 | .instantiate = generic_key_instantiate, | |
c06cfb08 | 259 | .match_preparse = dns_resolver_match_preparse, |
1a4240f4 WL |
260 | .revoke = user_revoke, |
261 | .destroy = user_destroy, | |
4a2d7892 | 262 | .describe = dns_resolver_describe, |
1362fa07 | 263 | .read = dns_resolver_read, |
1a4240f4 WL |
264 | }; |
265 | ||
266 | static int __init init_dns_resolver(void) | |
267 | { | |
268 | struct cred *cred; | |
269 | struct key *keyring; | |
270 | int ret; | |
271 | ||
1a4240f4 WL |
272 | /* create an override credential set with a special thread keyring in |
273 | * which DNS requests are cached | |
274 | * | |
275 | * this is used to prevent malicious redirections from being installed | |
276 | * with add_key(). | |
277 | */ | |
278 | cred = prepare_kernel_cred(NULL); | |
279 | if (!cred) | |
280 | return -ENOMEM; | |
281 | ||
2a74dbb9 LT |
282 | keyring = keyring_alloc(".dns_resolver", |
283 | GLOBAL_ROOT_UID, GLOBAL_ROOT_GID, cred, | |
f8aa23a5 DH |
284 | (KEY_POS_ALL & ~KEY_POS_SETATTR) | |
285 | KEY_USR_VIEW | KEY_USR_READ, | |
5ac7eace | 286 | KEY_ALLOC_NOT_IN_QUOTA, NULL, NULL); |
1a4240f4 WL |
287 | if (IS_ERR(keyring)) { |
288 | ret = PTR_ERR(keyring); | |
289 | goto failed_put_cred; | |
290 | } | |
291 | ||
1a4240f4 WL |
292 | ret = register_key_type(&key_type_dns_resolver); |
293 | if (ret < 0) | |
294 | goto failed_put_key; | |
295 | ||
296 | /* instruct request_key() to use this special keyring as a cache for | |
297 | * the results it looks up */ | |
700920eb | 298 | set_bit(KEY_FLAG_ROOT_CAN_CLEAR, &keyring->flags); |
1a4240f4 WL |
299 | cred->thread_keyring = keyring; |
300 | cred->jit_keyring = KEY_REQKEY_DEFL_THREAD_KEYRING; | |
301 | dns_resolver_cache = cred; | |
302 | ||
303 | kdebug("DNS resolver keyring: %d\n", key_serial(keyring)); | |
304 | return 0; | |
305 | ||
306 | failed_put_key: | |
307 | key_put(keyring); | |
308 | failed_put_cred: | |
309 | put_cred(cred); | |
310 | return ret; | |
311 | } | |
312 | ||
313 | static void __exit exit_dns_resolver(void) | |
314 | { | |
315 | key_revoke(dns_resolver_cache->thread_keyring); | |
316 | unregister_key_type(&key_type_dns_resolver); | |
317 | put_cred(dns_resolver_cache); | |
1a4240f4 WL |
318 | } |
319 | ||
320 | module_init(init_dns_resolver) | |
321 | module_exit(exit_dns_resolver) | |
322 | MODULE_LICENSE("GPL"); | |
f8aa23a5 | 323 |