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 <linux/slab.h>
19 #include <asm/uaccess.h>
20 #include "internal.h"
21
22 static int request_key_auth_instantiate(struct key *, const void *, size_t);
23 static void request_key_auth_describe(const struct key *, struct seq_file *);
24 static void request_key_auth_revoke(struct key *);
25 static void request_key_auth_destroy(struct key *);
26 static long request_key_auth_read(const struct key *, char __user *, size_t);
27
28 /*
29 * the request-key authorisation key type definition
30 */
31 struct key_type key_type_request_key_auth = {
32 .name = ".request_key_auth",
33 .def_datalen = sizeof(struct request_key_auth),
34 .instantiate = request_key_auth_instantiate,
35 .describe = request_key_auth_describe,
36 .revoke = request_key_auth_revoke,
37 .destroy = request_key_auth_destroy,
38 .read = request_key_auth_read,
39 };
40
41 /*****************************************************************************/
42 /*
43 * instantiate a request-key authorisation key
44 */
45 static int request_key_auth_instantiate(struct key *key,
46 const void *data,
47 size_t datalen)
48 {
49 key->payload.data = (struct request_key_auth *) data;
50 return 0;
51
52 } /* end request_key_auth_instantiate() */
53
54 /*****************************************************************************/
55 /*
56 * reading a request-key authorisation key retrieves the callout information
57 */
58 static void request_key_auth_describe(const struct key *key,
59 struct seq_file *m)
60 {
61 struct request_key_auth *rka = key->payload.data;
62
63 seq_puts(m, "key:");
64 seq_puts(m, key->description);
65 seq_printf(m, " pid:%d ci:%zu", rka->pid, rka->callout_len);
66
67 } /* end request_key_auth_describe() */
68
69 /*****************************************************************************/
70 /*
71 * read the callout_info data
72 * - the key's semaphore is read-locked
73 */
74 static long request_key_auth_read(const struct key *key,
75 char __user *buffer, size_t buflen)
76 {
77 struct request_key_auth *rka = key->payload.data;
78 size_t datalen;
79 long ret;
80
81 datalen = rka->callout_len;
82 ret = datalen;
83
84 /* we can return the data as is */
85 if (buffer && buflen > 0) {
86 if (buflen > datalen)
87 buflen = datalen;
88
89 if (copy_to_user(buffer, rka->callout_info, buflen) != 0)
90 ret = -EFAULT;
91 }
92
93 return ret;
94
95 } /* end request_key_auth_read() */
96
97 /*****************************************************************************/
98 /*
99 * handle revocation of an authorisation token key
100 * - called with the key sem write-locked
101 */
102 static void request_key_auth_revoke(struct key *key)
103 {
104 struct request_key_auth *rka = key->payload.data;
105
106 kenter("{%d}", key->serial);
107
108 if (rka->cred) {
109 put_cred(rka->cred);
110 rka->cred = NULL;
111 }
112
113 } /* end request_key_auth_revoke() */
114
115 /*****************************************************************************/
116 /*
117 * destroy an instantiation authorisation token key
118 */
119 static void request_key_auth_destroy(struct key *key)
120 {
121 struct request_key_auth *rka = key->payload.data;
122
123 kenter("{%d}", key->serial);
124
125 if (rka->cred) {
126 put_cred(rka->cred);
127 rka->cred = NULL;
128 }
129
130 key_put(rka->target_key);
131 key_put(rka->dest_keyring);
132 kfree(rka->callout_info);
133 kfree(rka);
134
135 } /* end request_key_auth_destroy() */
136
137 /*****************************************************************************/
138 /*
139 * create an authorisation token for /sbin/request-key or whoever to gain
140 * access to the caller's security data
141 */
142 struct key *request_key_auth_new(struct key *target, const void *callout_info,
143 size_t callout_len, struct key *dest_keyring)
144 {
145 struct request_key_auth *rka, *irka;
146 const struct cred *cred = current->cred;
147 struct key *authkey = NULL;
148 char desc[20];
149 int ret;
150
151 kenter("%d,", target->serial);
152
153 /* allocate a auth record */
154 rka = kmalloc(sizeof(*rka), GFP_KERNEL);
155 if (!rka) {
156 kleave(" = -ENOMEM");
157 return ERR_PTR(-ENOMEM);
158 }
159 rka->callout_info = kmalloc(callout_len, GFP_KERNEL);
160 if (!rka->callout_info) {
161 kleave(" = -ENOMEM");
162 kfree(rka);
163 return ERR_PTR(-ENOMEM);
164 }
165
166 /* see if the calling process is already servicing the key request of
167 * another process */
168 if (cred->request_key_auth) {
169 /* it is - use that instantiation context here too */
170 down_read(&cred->request_key_auth->sem);
171
172 /* if the auth key has been revoked, then the key we're
173 * servicing is already instantiated */
174 if (test_bit(KEY_FLAG_REVOKED, &cred->request_key_auth->flags))
175 goto auth_key_revoked;
176
177 irka = cred->request_key_auth->payload.data;
178 rka->cred = get_cred(irka->cred);
179 rka->pid = irka->pid;
180
181 up_read(&cred->request_key_auth->sem);
182 }
183 else {
184 /* it isn't - use this process as the context */
185 rka->cred = get_cred(cred);
186 rka->pid = current->pid;
187 }
188
189 rka->target_key = key_get(target);
190 rka->dest_keyring = key_get(dest_keyring);
191 memcpy(rka->callout_info, callout_info, callout_len);
192 rka->callout_len = callout_len;
193
194 /* allocate the auth key */
195 sprintf(desc, "%x", target->serial);
196
197 authkey = key_alloc(&key_type_request_key_auth, desc,
198 cred->fsuid, cred->fsgid, cred,
199 KEY_POS_VIEW | KEY_POS_READ | KEY_POS_SEARCH |
200 KEY_USR_VIEW, KEY_ALLOC_NOT_IN_QUOTA);
201 if (IS_ERR(authkey)) {
202 ret = PTR_ERR(authkey);
203 goto error_alloc;
204 }
205
206 /* construct the auth key */
207 ret = key_instantiate_and_link(authkey, rka, 0, NULL, NULL);
208 if (ret < 0)
209 goto error_inst;
210
211 kleave(" = {%d,%d}", authkey->serial, atomic_read(&authkey->usage));
212 return authkey;
213
214 auth_key_revoked:
215 up_read(&cred->request_key_auth->sem);
216 kfree(rka->callout_info);
217 kfree(rka);
218 kleave("= -EKEYREVOKED");
219 return ERR_PTR(-EKEYREVOKED);
220
221 error_inst:
222 key_revoke(authkey);
223 key_put(authkey);
224 error_alloc:
225 key_put(rka->target_key);
226 key_put(rka->dest_keyring);
227 kfree(rka->callout_info);
228 kfree(rka);
229 kleave("= %d", ret);
230 return ERR_PTR(ret);
231
232 } /* end request_key_auth_new() */
233
234 /*****************************************************************************/
235 /*
236 * see if an authorisation key is associated with a particular key
237 */
238 static int key_get_instantiation_authkey_match(const struct key *key,
239 const void *_id)
240 {
241 struct request_key_auth *rka = key->payload.data;
242 key_serial_t id = (key_serial_t)(unsigned long) _id;
243
244 return rka->target_key->serial == id;
245
246 } /* end key_get_instantiation_authkey_match() */
247
248 /*****************************************************************************/
249 /*
250 * get the authorisation key for instantiation of a specific key if attached to
251 * the current process's keyrings
252 * - this key is inserted into a keyring and that is set as /sbin/request-key's
253 * session keyring
254 * - a target_id of zero specifies any valid token
255 */
256 struct key *key_get_instantiation_authkey(key_serial_t target_id)
257 {
258 const struct cred *cred = current_cred();
259 struct key *authkey;
260 key_ref_t authkey_ref;
261
262 authkey_ref = search_process_keyrings(
263 &key_type_request_key_auth,
264 (void *) (unsigned long) target_id,
265 key_get_instantiation_authkey_match,
266 cred);
267
268 if (IS_ERR(authkey_ref)) {
269 authkey = ERR_CAST(authkey_ref);
270 goto error;
271 }
272
273 authkey = key_ref_to_ptr(authkey_ref);
274 if (test_bit(KEY_FLAG_REVOKED, &authkey->flags)) {
275 key_put(authkey);
276 authkey = ERR_PTR(-EKEYREVOKED);
277 }
278
279 error:
280 return authkey;
281
282 } /* end key_get_instantiation_authkey() */
283
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