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