1 /* request_key_auth.c: request key authorisation controlling key def
2 *
3 * Copyright (C) 2005 Red Hat, Inc. All Rights Reserved.
4 * Written by David Howells (dhowells@redhat.com)
5 *
6 * This program is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU General Public License
8 * as published by the Free Software Foundation; either version
9 * 2 of the License, or (at your option) any later version.
10 *
11 * See Documentation/keys-request-key.txt
12 */
13
14 #include <linux/module.h>
15 #include <linux/sched.h>
16 #include <linux/err.h>
17 #include <linux/seq_file.h>
18 #include <asm/uaccess.h>
19 #include "internal.h"
20
21 static int request_key_auth_instantiate(struct key *, const void *, size_t);
22 static void request_key_auth_describe(const struct key *, struct seq_file *);
23 static void request_key_auth_revoke(struct key *);
24 static void request_key_auth_destroy(struct key *);
25 static long request_key_auth_read(const struct key *, char __user *, size_t);
26
27 /*
28 * the request-key authorisation key type definition
29 */
30 struct key_type key_type_request_key_auth = {
31 .name = ".request_key_auth",
32 .def_datalen = sizeof(struct request_key_auth),
33 .instantiate = request_key_auth_instantiate,
34 .describe = request_key_auth_describe,
35 .revoke = request_key_auth_revoke,
36 .destroy = request_key_auth_destroy,
37 .read = request_key_auth_read,
38 };
39
40 /*****************************************************************************/
41 /*
42 * instantiate a request-key authorisation key
43 */
44 static int request_key_auth_instantiate(struct key *key,
45 const void *data,
46 size_t datalen)
47 {
48 key->payload.data = (struct request_key_auth *) data;
49 return 0;
50
51 } /* end request_key_auth_instantiate() */
52
53 /*****************************************************************************/
54 /*
55 * reading a request-key authorisation key retrieves the callout information
56 */
57 static void request_key_auth_describe(const struct key *key,
58 struct seq_file *m)
59 {
60 struct request_key_auth *rka = key->payload.data;
61
62 seq_puts(m, "key:");
63 seq_puts(m, key->description);
64 seq_printf(m, " pid:%d ci:%zu", rka->pid, strlen(rka->callout_info));
65
66 } /* end request_key_auth_describe() */
67
68 /*****************************************************************************/
69 /*
70 * read the callout_info data
71 * - the key's semaphore is read-locked
72 */
73 static long request_key_auth_read(const struct key *key,
74 char __user *buffer, size_t buflen)
75 {
76 struct request_key_auth *rka = key->payload.data;
77 size_t datalen;
78 long ret;
79
80 datalen = strlen(rka->callout_info);
81 ret = datalen;
82
83 /* we can return the data as is */
84 if (buffer && buflen > 0) {
85 if (buflen > datalen)
86 buflen = datalen;
87
88 if (copy_to_user(buffer, rka->callout_info, buflen) != 0)
89 ret = -EFAULT;
90 }
91
92 return ret;
93
94 } /* end request_key_auth_read() */
95
96 /*****************************************************************************/
97 /*
98 * handle revocation of an authorisation token key
99 * - called with the key sem write-locked
100 */
101 static void request_key_auth_revoke(struct key *key)
102 {
103 struct request_key_auth *rka = key->payload.data;
104
105 kenter("{%d}", key->serial);
106
107 if (rka->context) {
108 put_task_struct(rka->context);
109 rka->context = NULL;
110 }
111
112 } /* end request_key_auth_revoke() */
113
114 /*****************************************************************************/
115 /*
116 * destroy an instantiation authorisation token key
117 */
118 static void request_key_auth_destroy(struct key *key)
119 {
120 struct request_key_auth *rka = key->payload.data;
121
122 kenter("{%d}", key->serial);
123
124 if (rka->context) {
125 put_task_struct(rka->context);
126 rka->context = NULL;
127 }
128
129 key_put(rka->target_key);
130 kfree(rka->callout_info);
131 kfree(rka);
132
133 } /* end request_key_auth_destroy() */
134
135 /*****************************************************************************/
136 /*
137 * create an authorisation token for /sbin/request-key or whoever to gain
138 * access to the caller's security data
139 */
140 struct key *request_key_auth_new(struct key *target, const char *callout_info)
141 {
142 struct request_key_auth *rka, *irka;
143 struct key *authkey = NULL;
144 char desc[20];
145 int ret;
146
147 kenter("%d,", target->serial);
148
149 /* allocate a auth record */
150 rka = kmalloc(sizeof(*rka), GFP_KERNEL);
151 if (!rka) {
152 kleave(" = -ENOMEM");
153 return ERR_PTR(-ENOMEM);
154 }
155 rka->callout_info = kmalloc(strlen(callout_info) + 1, GFP_KERNEL);
156 if (!rka->callout_info) {
157 kleave(" = -ENOMEM");
158 kfree(rka);
159 return ERR_PTR(-ENOMEM);
160 }
161
162 /* see if the calling process is already servicing the key request of
163 * another process */
164 if (current->request_key_auth) {
165 /* it is - use that instantiation context here too */
166 down_read(¤t->request_key_auth->sem);
167
168 /* if the auth key has been revoked, then the key we're
169 * servicing is already instantiated */
170 if (test_bit(KEY_FLAG_REVOKED,
171 ¤t->request_key_auth->flags))
172 goto auth_key_revoked;
173
174 irka = current->request_key_auth->payload.data;
175 rka->context = irka->context;
176 rka->pid = irka->pid;
177 get_task_struct(rka->context);
178
179 up_read(¤t->request_key_auth->sem);
180 }
181 else {
182 /* it isn't - use this process as the context */
183 rka->context = current;
184 rka->pid = current->pid;
185 get_task_struct(rka->context);
186 }
187
188 rka->target_key = key_get(target);
189 strcpy(rka->callout_info, callout_info);
190
191 /* allocate the auth key */
192 sprintf(desc, "%x", target->serial);
193
194 authkey = key_alloc(&key_type_request_key_auth, desc,
195 current->fsuid, current->fsgid, current,
196 KEY_POS_VIEW | KEY_POS_READ | KEY_POS_SEARCH |
197 KEY_USR_VIEW, KEY_ALLOC_NOT_IN_QUOTA);
198 if (IS_ERR(authkey)) {
199 ret = PTR_ERR(authkey);
200 goto error_alloc;
201 }
202
203 /* construct and attach to the keyring */
204 ret = key_instantiate_and_link(authkey, rka, 0, NULL, NULL);
205 if (ret < 0)
206 goto error_inst;
207
208 kleave(" = {%d}", authkey->serial);
209 return authkey;
210
211 auth_key_revoked:
212 up_read(¤t->request_key_auth->sem);
213 kfree(rka->callout_info);
214 kfree(rka);
215 kleave("= -EKEYREVOKED");
216 return ERR_PTR(-EKEYREVOKED);
217
218 error_inst:
219 key_revoke(authkey);
220 key_put(authkey);
221 error_alloc:
222 key_put(rka->target_key);
223 kfree(rka->callout_info);
224 kfree(rka);
225 kleave("= %d", ret);
226 return ERR_PTR(ret);
227
228 } /* end request_key_auth_new() */
229
230 /*****************************************************************************/
231 /*
232 * see if an authorisation key is associated with a particular key
233 */
234 static int key_get_instantiation_authkey_match(const struct key *key,
235 const void *_id)
236 {
237 struct request_key_auth *rka = key->payload.data;
238 key_serial_t id = (key_serial_t)(unsigned long) _id;
239
240 return rka->target_key->serial == id;
241
242 } /* end key_get_instantiation_authkey_match() */
243
244 /*****************************************************************************/
245 /*
246 * get the authorisation key for instantiation of a specific key if attached to
247 * the current process's keyrings
248 * - this key is inserted into a keyring and that is set as /sbin/request-key's
249 * session keyring
250 * - a target_id of zero specifies any valid token
251 */
252 struct key *key_get_instantiation_authkey(key_serial_t target_id)
253 {
254 struct key *authkey;
255 key_ref_t authkey_ref;
256
257 authkey_ref = search_process_keyrings(
258 &key_type_request_key_auth,
259 (void *) (unsigned long) target_id,
260 key_get_instantiation_authkey_match,
261 current);
262
263 if (IS_ERR(authkey_ref)) {
264 authkey = ERR_CAST(authkey_ref);
265 goto error;
266 }
267
268 authkey = key_ref_to_ptr(authkey_ref);
269 if (test_bit(KEY_FLAG_REVOKED, &authkey->flags)) {
270 key_put(authkey);
271 authkey = ERR_PTR(-EKEYREVOKED);
272 }
273
274 error:
275 return authkey;
276
277 } /* end key_get_instantiation_authkey() */
278
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