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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 | |
22 | * along with this library; if not, write to the Free Software | |
23 | * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA | |
24 | */ | |
25 | #include <linux/module.h> | |
26 | #include <linux/moduleparam.h> | |
27 | #include <linux/slab.h> | |
28 | #include <linux/string.h> | |
29 | #include <linux/kernel.h> | |
30 | #include <linux/keyctl.h> | |
af352fe9 | 31 | #include <linux/err.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 | ||
40 | unsigned dns_resolver_debug; | |
41 | module_param_named(debug, dns_resolver_debug, uint, S_IWUSR | S_IRUGO); | |
42 | MODULE_PARM_DESC(debug, "DNS Resolver debugging mask"); | |
43 | ||
44 | const struct cred *dns_resolver_cache; | |
45 | ||
46 | /* | |
47 | * Instantiate a user defined key for dns_resolver. | |
48 | * | |
49 | * The data must be a NUL-terminated string, with the NUL char accounted in | |
50 | * datalen. | |
51 | * | |
52 | * If the data contains a '#' characters, then we take the clause after each | |
53 | * one to be an option of the form 'key=value'. The actual data of interest is | |
54 | * the string leading up to the first '#'. For instance: | |
55 | * | |
56 | * "ip1,ip2,...#foo=bar" | |
57 | */ | |
58 | static int | |
59 | dns_resolver_instantiate(struct key *key, const void *_data, size_t datalen) | |
60 | { | |
61 | struct user_key_payload *upayload; | |
62 | int ret; | |
63 | size_t result_len = 0; | |
64 | const char *data = _data, *opt; | |
65 | ||
66 | kenter("%%%d,%s,'%s',%zu", | |
67 | key->serial, key->description, data, datalen); | |
68 | ||
69 | if (datalen <= 1 || !data || data[datalen - 1] != '\0') | |
70 | return -EINVAL; | |
71 | datalen--; | |
72 | ||
73 | /* deal with any options embedded in the data */ | |
74 | opt = memchr(data, '#', datalen); | |
75 | if (!opt) { | |
76 | kdebug("no options currently supported"); | |
77 | return -EINVAL; | |
78 | } | |
79 | ||
80 | result_len = datalen; | |
81 | ret = key_payload_reserve(key, result_len); | |
82 | if (ret < 0) | |
83 | return -EINVAL; | |
84 | ||
85 | upayload = kmalloc(sizeof(*upayload) + result_len + 1, GFP_KERNEL); | |
86 | if (!upayload) { | |
87 | kleave(" = -ENOMEM"); | |
88 | return -ENOMEM; | |
89 | } | |
90 | ||
91 | upayload->datalen = result_len; | |
92 | memcpy(upayload->data, data, result_len); | |
93 | upayload->data[result_len] = '\0'; | |
94 | rcu_assign_pointer(key->payload.data, upayload); | |
95 | ||
96 | kleave(" = 0"); | |
97 | return 0; | |
98 | } | |
99 | ||
100 | /* | |
101 | * The description is of the form "[<type>:]<domain_name>" | |
102 | * | |
103 | * The domain name may be a simple name or an absolute domain name (which | |
104 | * should end with a period). The domain name is case-independent. | |
105 | */ | |
106 | static int | |
107 | dns_resolver_match(const struct key *key, const void *description) | |
108 | { | |
109 | int slen, dlen, ret = 0; | |
110 | const char *src = key->description, *dsp = description; | |
111 | ||
112 | kenter("%s,%s", src, dsp); | |
113 | ||
114 | if (!src || !dsp) | |
115 | goto no_match; | |
116 | ||
117 | if (strcasecmp(src, dsp) == 0) | |
118 | goto matched; | |
119 | ||
120 | slen = strlen(src); | |
121 | dlen = strlen(dsp); | |
122 | if (slen <= 0 || dlen <= 0) | |
123 | goto no_match; | |
124 | if (src[slen - 1] == '.') | |
125 | slen--; | |
126 | if (dsp[dlen - 1] == '.') | |
127 | dlen--; | |
128 | if (slen != dlen || strncasecmp(src, dsp, slen) != 0) | |
129 | goto no_match; | |
130 | ||
131 | matched: | |
132 | ret = 1; | |
133 | no_match: | |
134 | kleave(" = %d", ret); | |
135 | return ret; | |
136 | } | |
137 | ||
138 | struct key_type key_type_dns_resolver = { | |
139 | .name = "dns_resolver", | |
140 | .instantiate = dns_resolver_instantiate, | |
141 | .match = dns_resolver_match, | |
142 | .revoke = user_revoke, | |
143 | .destroy = user_destroy, | |
144 | .describe = user_describe, | |
145 | .read = user_read, | |
146 | }; | |
147 | ||
148 | static int __init init_dns_resolver(void) | |
149 | { | |
150 | struct cred *cred; | |
151 | struct key *keyring; | |
152 | int ret; | |
153 | ||
154 | printk(KERN_NOTICE "Registering the %s key type\n", | |
155 | key_type_dns_resolver.name); | |
156 | ||
157 | /* create an override credential set with a special thread keyring in | |
158 | * which DNS requests are cached | |
159 | * | |
160 | * this is used to prevent malicious redirections from being installed | |
161 | * with add_key(). | |
162 | */ | |
163 | cred = prepare_kernel_cred(NULL); | |
164 | if (!cred) | |
165 | return -ENOMEM; | |
166 | ||
167 | keyring = key_alloc(&key_type_keyring, ".dns_resolver", 0, 0, cred, | |
168 | (KEY_POS_ALL & ~KEY_POS_SETATTR) | | |
169 | KEY_USR_VIEW | KEY_USR_READ, | |
170 | KEY_ALLOC_NOT_IN_QUOTA); | |
171 | if (IS_ERR(keyring)) { | |
172 | ret = PTR_ERR(keyring); | |
173 | goto failed_put_cred; | |
174 | } | |
175 | ||
176 | ret = key_instantiate_and_link(keyring, NULL, 0, NULL, NULL); | |
177 | if (ret < 0) | |
178 | goto failed_put_key; | |
179 | ||
180 | ret = register_key_type(&key_type_dns_resolver); | |
181 | if (ret < 0) | |
182 | goto failed_put_key; | |
183 | ||
184 | /* instruct request_key() to use this special keyring as a cache for | |
185 | * the results it looks up */ | |
186 | cred->thread_keyring = keyring; | |
187 | cred->jit_keyring = KEY_REQKEY_DEFL_THREAD_KEYRING; | |
188 | dns_resolver_cache = cred; | |
189 | ||
190 | kdebug("DNS resolver keyring: %d\n", key_serial(keyring)); | |
191 | return 0; | |
192 | ||
193 | failed_put_key: | |
194 | key_put(keyring); | |
195 | failed_put_cred: | |
196 | put_cred(cred); | |
197 | return ret; | |
198 | } | |
199 | ||
200 | static void __exit exit_dns_resolver(void) | |
201 | { | |
202 | key_revoke(dns_resolver_cache->thread_keyring); | |
203 | unregister_key_type(&key_type_dns_resolver); | |
204 | put_cred(dns_resolver_cache); | |
205 | printk(KERN_NOTICE "Unregistered %s key type\n", | |
206 | key_type_dns_resolver.name); | |
207 | } | |
208 | ||
209 | module_init(init_dns_resolver) | |
210 | module_exit(exit_dns_resolver) | |
211 | MODULE_LICENSE("GPL"); |