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Wang Lei1a4240f2010-08-04 15:16:33 +01001/* 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
Jeff Kirsherc057b192013-12-06 09:13:44 -080022 * along with this library; if not, see <http://www.gnu.org/licenses/>.
Wang Lei1a4240f2010-08-04 15:16:33 +010023 */
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>
Stephen Rothwellaf352fe2010-08-06 03:13:47 +010030#include <linux/err.h>
Wang Lei4a2d7892010-08-11 09:37:58 +010031#include <linux/seq_file.h>
Wang Lei1a4240f2010-08-04 15:16:33 +010032#include <keys/dns_resolver-type.h>
33#include <keys/user-type.h>
34#include "internal.h"
35
36MODULE_DESCRIPTION("DNS Resolver");
37MODULE_AUTHOR("Wang Lei");
38MODULE_LICENSE("GPL");
39
Eric Dumazet95c96172012-04-15 05:58:06 +000040unsigned int dns_resolver_debug;
Wang Lei1a4240f2010-08-04 15:16:33 +010041module_param_named(debug, dns_resolver_debug, uint, S_IWUSR | S_IRUGO);
42MODULE_PARM_DESC(debug, "DNS Resolver debugging mask");
43
44const struct cred *dns_resolver_cache;
45
Wang Lei4a2d7892010-08-11 09:37:58 +010046#define DNS_ERRORNO_OPTION "dnserror"
47
Wang Lei1a4240f2010-08-04 15:16:33 +010048/*
David Howellsd46d4942014-07-18 18:56:36 +010049 * Preparse instantiation data for a dns_resolver key.
Wang Lei1a4240f2010-08-04 15:16:33 +010050 *
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 */
60static int
David Howellsd46d4942014-07-18 18:56:36 +010061dns_resolver_preparse(struct key_preparsed_payload *prep)
Wang Lei1a4240f2010-08-04 15:16:33 +010062{
63 struct user_key_payload *upayload;
Wang Lei4a2d7892010-08-11 09:37:58 +010064 unsigned long derrno;
Wang Lei1a4240f2010-08-04 15:16:33 +010065 int ret;
David Howellsd46d4942014-07-18 18:56:36 +010066 int datalen = prep->datalen, result_len = 0;
David Howellscf7f6012012-09-13 13:06:29 +010067 const char *data = prep->data, *end, *opt;
Wang Lei1a4240f2010-08-04 15:16:33 +010068
David Howellsd46d4942014-07-18 18:56:36 +010069 kenter("'%*.*s',%u", datalen, datalen, data, datalen);
Wang Lei1a4240f2010-08-04 15:16:33 +010070
71 if (datalen <= 1 || !data || data[datalen - 1] != '\0')
72 return -EINVAL;
73 datalen--;
74
75 /* deal with any options embedded in the data */
Wang Lei4a2d7892010-08-11 09:37:58 +010076 end = data + datalen;
Wang Lei1a4240f2010-08-04 15:16:33 +010077 opt = memchr(data, '#', datalen);
78 if (!opt) {
Wang Lei4a2d7892010-08-11 09:37:58 +010079 /* 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 {
89 const char *eq;
90 int opt_len, opt_nlen, opt_vlen, tmp;
91
92 next_opt = memchr(opt, '#', end - opt) ?: end;
93 opt_len = next_opt - opt;
94 if (!opt_len) {
95 printk(KERN_WARNING
David Howellsd46d4942014-07-18 18:56:36 +010096 "Empty option to dns_resolver key\n");
Wang Lei4a2d7892010-08-11 09:37:58 +010097 return -EINVAL;
98 }
99
100 eq = memchr(opt, '=', opt_len) ?: end;
101 opt_nlen = eq - opt;
102 eq++;
103 opt_vlen = next_opt - eq; /* will be -1 if no value */
104
105 tmp = opt_vlen >= 0 ? opt_vlen : 0;
106 kdebug("option '%*.*s' val '%*.*s'",
107 opt_nlen, opt_nlen, opt, tmp, tmp, eq);
108
109 /* see if it's an error number representing a DNS error
110 * that's to be recorded as the result in this key */
111 if (opt_nlen == sizeof(DNS_ERRORNO_OPTION) - 1 &&
112 memcmp(opt, DNS_ERRORNO_OPTION, opt_nlen) == 0) {
113 kdebug("dns error number option");
114 if (opt_vlen <= 0)
115 goto bad_option_value;
116
“Cosmin92338dc2013-07-12 09:33:33 +0300117 ret = kstrtoul(eq, 10, &derrno);
Wang Lei4a2d7892010-08-11 09:37:58 +0100118 if (ret < 0)
119 goto bad_option_value;
120
121 if (derrno < 1 || derrno > 511)
122 goto bad_option_value;
123
124 kdebug("dns error no. = %lu", derrno);
David Howellsd46d4942014-07-18 18:56:36 +0100125 prep->type_data[0] = ERR_PTR(-derrno);
Wang Lei4a2d7892010-08-11 09:37:58 +0100126 continue;
127 }
128
129 bad_option_value:
130 printk(KERN_WARNING
David Howellsd46d4942014-07-18 18:56:36 +0100131 "Option '%*.*s' to dns_resolver key:"
Wang Lei4a2d7892010-08-11 09:37:58 +0100132 " bad/missing value\n",
David Howellsd46d4942014-07-18 18:56:36 +0100133 opt_nlen, opt_nlen, opt);
Wang Lei4a2d7892010-08-11 09:37:58 +0100134 return -EINVAL;
135 } while (opt = next_opt + 1, opt < end);
Wang Lei1a4240f2010-08-04 15:16:33 +0100136 }
137
Wang Lei4a2d7892010-08-11 09:37:58 +0100138 /* don't cache the result if we're caching an error saying there's no
139 * result */
David Howellsd46d4942014-07-18 18:56:36 +0100140 if (prep->type_data[0]) {
141 kleave(" = 0 [h_error %ld]", PTR_ERR(prep->type_data[0]));
Wang Lei4a2d7892010-08-11 09:37:58 +0100142 return 0;
143 }
144
145 kdebug("store result");
David Howellsd46d4942014-07-18 18:56:36 +0100146 prep->quotalen = result_len;
Wang Lei1a4240f2010-08-04 15:16:33 +0100147
148 upayload = kmalloc(sizeof(*upayload) + result_len + 1, GFP_KERNEL);
149 if (!upayload) {
150 kleave(" = -ENOMEM");
151 return -ENOMEM;
152 }
153
154 upayload->datalen = result_len;
155 memcpy(upayload->data, data, result_len);
156 upayload->data[result_len] = '\0';
Wang Lei1a4240f2010-08-04 15:16:33 +0100157
David Howellsd46d4942014-07-18 18:56:36 +0100158 prep->payload[0] = upayload;
Wang Lei1a4240f2010-08-04 15:16:33 +0100159 kleave(" = 0");
160 return 0;
161}
162
163/*
David Howellsd46d4942014-07-18 18:56:36 +0100164 * Clean up the preparse data
165 */
166static void dns_resolver_free_preparse(struct key_preparsed_payload *prep)
167{
168 pr_devel("==>%s()\n", __func__);
169
170 kfree(prep->payload[0]);
171}
172
173/*
Wang Lei1a4240f2010-08-04 15:16:33 +0100174 * The description is of the form "[<type>:]<domain_name>"
175 *
176 * The domain name may be a simple name or an absolute domain name (which
177 * should end with a period). The domain name is case-independent.
178 */
David Howells0c903ab2014-09-16 17:36:08 +0100179static bool dns_resolver_cmp(const struct key *key,
180 const struct key_match_data *match_data)
Wang Lei1a4240f2010-08-04 15:16:33 +0100181{
182 int slen, dlen, ret = 0;
David Howells46291952014-09-16 17:36:02 +0100183 const char *src = key->description, *dsp = match_data->raw_data;
Wang Lei1a4240f2010-08-04 15:16:33 +0100184
185 kenter("%s,%s", src, dsp);
186
187 if (!src || !dsp)
188 goto no_match;
189
190 if (strcasecmp(src, dsp) == 0)
191 goto matched;
192
193 slen = strlen(src);
194 dlen = strlen(dsp);
195 if (slen <= 0 || dlen <= 0)
196 goto no_match;
197 if (src[slen - 1] == '.')
198 slen--;
199 if (dsp[dlen - 1] == '.')
200 dlen--;
201 if (slen != dlen || strncasecmp(src, dsp, slen) != 0)
202 goto no_match;
203
204matched:
205 ret = 1;
206no_match:
207 kleave(" = %d", ret);
208 return ret;
209}
210
Wang Lei4a2d7892010-08-11 09:37:58 +0100211/*
David Howellsc06cfb02014-09-16 17:36:06 +0100212 * Preparse the match criterion.
213 */
214static int dns_resolver_match_preparse(struct key_match_data *match_data)
215{
216 match_data->lookup_type = KEYRING_SEARCH_LOOKUP_ITERATE;
217 match_data->cmp = dns_resolver_cmp;
218 return 0;
219}
220
221/*
Wang Lei4a2d7892010-08-11 09:37:58 +0100222 * Describe a DNS key
223 */
224static void dns_resolver_describe(const struct key *key, struct seq_file *m)
225{
226 int err = key->type_data.x[0];
227
228 seq_puts(m, key->description);
David Howells78b72802011-03-11 17:57:23 +0000229 if (key_is_instantiated(key)) {
230 if (err)
231 seq_printf(m, ": %d", err);
232 else
233 seq_printf(m, ": %u", key->datalen);
234 }
Wang Lei4a2d7892010-08-11 09:37:58 +0100235}
236
David Howells1362fa02011-03-03 11:28:58 +0000237/*
238 * read the DNS data
239 * - the key's semaphore is read-locked
240 */
241static long dns_resolver_read(const struct key *key,
242 char __user *buffer, size_t buflen)
243{
244 if (key->type_data.x[0])
245 return key->type_data.x[0];
246
247 return user_read(key, buffer, buflen);
248}
249
Wang Lei1a4240f2010-08-04 15:16:33 +0100250struct key_type key_type_dns_resolver = {
251 .name = "dns_resolver",
David Howellsd46d4942014-07-18 18:56:36 +0100252 .preparse = dns_resolver_preparse,
253 .free_preparse = dns_resolver_free_preparse,
254 .instantiate = generic_key_instantiate,
David Howellsc06cfb02014-09-16 17:36:06 +0100255 .match_preparse = dns_resolver_match_preparse,
Wang Lei1a4240f2010-08-04 15:16:33 +0100256 .revoke = user_revoke,
257 .destroy = user_destroy,
Wang Lei4a2d7892010-08-11 09:37:58 +0100258 .describe = dns_resolver_describe,
David Howells1362fa02011-03-03 11:28:58 +0000259 .read = dns_resolver_read,
Wang Lei1a4240f2010-08-04 15:16:33 +0100260};
261
262static int __init init_dns_resolver(void)
263{
264 struct cred *cred;
265 struct key *keyring;
266 int ret;
267
Wang Lei1a4240f2010-08-04 15:16:33 +0100268 /* create an override credential set with a special thread keyring in
269 * which DNS requests are cached
270 *
271 * this is used to prevent malicious redirections from being installed
272 * with add_key().
273 */
274 cred = prepare_kernel_cred(NULL);
275 if (!cred)
276 return -ENOMEM;
277
Linus Torvalds2a74dbb2012-12-16 15:40:50 -0800278 keyring = keyring_alloc(".dns_resolver",
279 GLOBAL_ROOT_UID, GLOBAL_ROOT_GID, cred,
David Howellsf8aa23a2012-10-02 19:24:56 +0100280 (KEY_POS_ALL & ~KEY_POS_SETATTR) |
281 KEY_USR_VIEW | KEY_USR_READ,
282 KEY_ALLOC_NOT_IN_QUOTA, NULL);
Wang Lei1a4240f2010-08-04 15:16:33 +0100283 if (IS_ERR(keyring)) {
284 ret = PTR_ERR(keyring);
285 goto failed_put_cred;
286 }
287
Wang Lei1a4240f2010-08-04 15:16:33 +0100288 ret = register_key_type(&key_type_dns_resolver);
289 if (ret < 0)
290 goto failed_put_key;
291
292 /* instruct request_key() to use this special keyring as a cache for
293 * the results it looks up */
David Howells700920e2012-01-18 15:31:45 +0000294 set_bit(KEY_FLAG_ROOT_CAN_CLEAR, &keyring->flags);
Wang Lei1a4240f2010-08-04 15:16:33 +0100295 cred->thread_keyring = keyring;
296 cred->jit_keyring = KEY_REQKEY_DEFL_THREAD_KEYRING;
297 dns_resolver_cache = cred;
298
299 kdebug("DNS resolver keyring: %d\n", key_serial(keyring));
300 return 0;
301
302failed_put_key:
303 key_put(keyring);
304failed_put_cred:
305 put_cred(cred);
306 return ret;
307}
308
309static void __exit exit_dns_resolver(void)
310{
311 key_revoke(dns_resolver_cache->thread_keyring);
312 unregister_key_type(&key_type_dns_resolver);
313 put_cred(dns_resolver_cache);
Wang Lei1a4240f2010-08-04 15:16:33 +0100314}
315
316module_init(init_dns_resolver)
317module_exit(exit_dns_resolver)
318MODULE_LICENSE("GPL");
David Howellsf8aa23a2012-10-02 19:24:56 +0100319