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1// SPDX-License-Identifier: GPL-2.0-or-later
2/* Request key authorisation token key definition.
3 *
4 * Copyright (C) 2005 Red Hat, Inc. All Rights Reserved.
5 * Written by David Howells ([email protected])
6 *
7 * See Documentation/security/keys/request-key.rst
8 */
9
10#include <linux/sched.h>
11#include <linux/err.h>
12#include <linux/pid.h>
13#include <linux/proc_fs.h>
14#include <linux/seq_file.h>
15#include <linux/slab.h>
16#include <linux/uaccess.h>
17#include "internal.h"
18#include <keys/request_key_auth-type.h>
19
20static int request_key_auth_preparse(struct key_preparsed_payload *);
21static void request_key_auth_free_preparse(struct key_preparsed_payload *);
22static int request_key_auth_instantiate(struct key *,
23 struct key_preparsed_payload *);
24static void request_key_auth_describe(const struct key *, struct seq_file *);
25static void request_key_auth_revoke(struct key *);
26static void request_key_auth_destroy(struct key *);
27static long request_key_auth_read(const struct key *, char *, size_t);
28static void request_key_auth_rcu_disposal(struct rcu_head *);
29
30/*
31 * The request-key authorisation key type definition.
32 */
33struct key_type key_type_request_key_auth = {
34 .name = ".request_key_auth",
35 .def_datalen = sizeof(struct request_key_auth),
36 .preparse = request_key_auth_preparse,
37 .free_preparse = request_key_auth_free_preparse,
38 .instantiate = request_key_auth_instantiate,
39 .describe = request_key_auth_describe,
40 .revoke = request_key_auth_revoke,
41 .destroy = request_key_auth_destroy,
42 .read = request_key_auth_read,
43};
44
45static int request_key_auth_preparse(struct key_preparsed_payload *prep)
46{
47 return 0;
48}
49
50static void request_key_auth_free_preparse(struct key_preparsed_payload *prep)
51{
52}
53
54/*
55 * Instantiate a request-key authorisation key.
56 */
57static int request_key_auth_instantiate(struct key *key,
58 struct key_preparsed_payload *prep)
59{
60 rcu_assign_keypointer(key, (struct request_key_auth *)prep->data);
61 return 0;
62}
63
64/*
65 * Describe an authorisation token.
66 */
67static void request_key_auth_describe(const struct key *key,
68 struct seq_file *m)
69{
70 struct request_key_auth *rka = dereference_key_rcu(key);
71
72 if (!rka)
73 return;
74
75 seq_puts(m, "key:");
76 seq_puts(m, key->description);
77 if (key_is_positive(key))
78 seq_printf(m, " pid:%d ci:%zu",
79 pid_nr_ns(rka->pid,
80 proc_pid_ns(file_inode(m->file)->i_sb)),
81 rka->callout_len);
82}
83
84/*
85 * Read the callout_info data (retrieves the callout information).
86 * - the key's semaphore is read-locked
87 */
88static long request_key_auth_read(const struct key *key,
89 char *buffer, size_t buflen)
90{
91 struct request_key_auth *rka = dereference_key_locked(key);
92 size_t datalen;
93 long ret;
94
95 if (!rka)
96 return -EKEYREVOKED;
97
98 datalen = rka->callout_len;
99 ret = datalen;
100
101 /* we can return the data as is */
102 if (buffer && buflen > 0) {
103 if (buflen > datalen)
104 buflen = datalen;
105
106 memcpy(buffer, rka->callout_info, buflen);
107 }
108
109 return ret;
110}
111
112static void free_request_key_auth(struct request_key_auth *rka)
113{
114 if (!rka)
115 return;
116 key_put(rka->target_key);
117 key_put(rka->dest_keyring);
118 if (rka->cred)
119 put_cred(rka->cred);
120 kfree(rka->callout_info);
121 put_pid(rka->pid);
122 kfree(rka);
123}
124
125/*
126 * Take a reference to the request-key authorisation payload so callers can
127 * drop authkey->sem before doing operations that may sleep.
128 */
129struct request_key_auth *request_key_auth_get(struct key *authkey)
130{
131 struct request_key_auth *rka;
132
133 down_read(&authkey->sem);
134 rka = dereference_key_locked(authkey);
135 if (rka && !test_bit(KEY_FLAG_REVOKED, &authkey->flags))
136 refcount_inc(&rka->usage);
137 else
138 rka = NULL;
139 up_read(&authkey->sem);
140
141 return rka;
142}
143
144void request_key_auth_put(struct request_key_auth *rka)
145{
146 if (rka && refcount_dec_and_test(&rka->usage))
147 call_rcu(&rka->rcu, request_key_auth_rcu_disposal);
148}
149
150/*
151 * Dispose of the request_key_auth record under RCU conditions
152 */
153static void request_key_auth_rcu_disposal(struct rcu_head *rcu)
154{
155 struct request_key_auth *rka =
156 container_of(rcu, struct request_key_auth, rcu);
157
158 free_request_key_auth(rka);
159}
160
161/*
162 * Handle revocation of an authorisation token key.
163 *
164 * Called with the key sem write-locked.
165 */
166static void request_key_auth_revoke(struct key *key)
167{
168 struct request_key_auth *rka = dereference_key_locked(key);
169
170 kenter("{%d}", key->serial);
171 if (!rka)
172 return;
173 rcu_assign_keypointer(key, NULL);
174 request_key_auth_put(rka);
175}
176
177/*
178 * Destroy an instantiation authorisation token key.
179 */
180static void request_key_auth_destroy(struct key *key)
181{
182 struct request_key_auth *rka = rcu_access_pointer(key->payload.rcu_data0);
183
184 kenter("{%d}", key->serial);
185 if (rka) {
186 rcu_assign_keypointer(key, NULL);
187 request_key_auth_put(rka);
188 }
189}
190
191/*
192 * Create an authorisation token for /sbin/request-key or whoever to gain
193 * access to the caller's security data.
194 */
195struct key *request_key_auth_new(struct key *target, const char *op,
196 const void *callout_info, size_t callout_len,
197 struct key *dest_keyring)
198{
199 struct request_key_auth *rka, *irka;
200 const struct cred *cred = current_cred();
201 struct key *authkey = NULL;
202 char desc[20];
203 int ret = -ENOMEM;
204
205 kenter("%d,", target->serial);
206
207 /* allocate a auth record */
208 rka = kzalloc_obj(*rka);
209 if (!rka)
210 goto error;
211 refcount_set(&rka->usage, 1);
212 rka->callout_info = kmemdup(callout_info, callout_len, GFP_KERNEL);
213 if (!rka->callout_info)
214 goto error_free_rka;
215 rka->callout_len = callout_len;
216 strscpy(rka->op, op, sizeof(rka->op));
217
218 /* see if the calling process is already servicing the key request of
219 * another process */
220 if (cred->request_key_auth) {
221 /* it is - use that instantiation context here too */
222 down_read(&cred->request_key_auth->sem);
223
224 /* if the auth key has been revoked, then the key we're
225 * servicing is already instantiated */
226 if (test_bit(KEY_FLAG_REVOKED,
227 &cred->request_key_auth->flags)) {
228 up_read(&cred->request_key_auth->sem);
229 ret = -EKEYREVOKED;
230 goto error_free_rka;
231 }
232
233 irka = cred->request_key_auth->payload.data[0];
234 rka->cred = get_cred(irka->cred);
235 rka->pid = get_pid(irka->pid);
236
237 up_read(&cred->request_key_auth->sem);
238 }
239 else {
240 /* it isn't - use this process as the context */
241 rka->cred = get_cred(cred);
242 rka->pid = get_pid(task_pid(current));
243 }
244
245 rka->target_key = key_get(target);
246 rka->dest_keyring = key_get(dest_keyring);
247
248 /* allocate the auth key */
249 sprintf(desc, "%x", target->serial);
250
251 authkey = key_alloc(&key_type_request_key_auth, desc,
252 cred->fsuid, cred->fsgid, cred,
253 KEY_POS_VIEW | KEY_POS_READ | KEY_POS_SEARCH | KEY_POS_LINK |
254 KEY_USR_VIEW, KEY_ALLOC_NOT_IN_QUOTA, NULL);
255 if (IS_ERR(authkey)) {
256 ret = PTR_ERR(authkey);
257 goto error_free_rka;
258 }
259
260 /* construct the auth key */
261 ret = key_instantiate_and_link(authkey, rka, 0, NULL, NULL);
262 if (ret < 0)
263 goto error_put_authkey;
264
265 kleave(" = {%d,%d}", authkey->serial, refcount_read(&authkey->usage));
266 return authkey;
267
268error_put_authkey:
269 key_put(authkey);
270error_free_rka:
271 free_request_key_auth(rka);
272error:
273 kleave("= %d", ret);
274 return ERR_PTR(ret);
275}
276
277/*
278 * Search the current process's keyrings for the authorisation key for
279 * instantiation of a key.
280 */
281struct key *key_get_instantiation_authkey(key_serial_t target_id)
282{
283 char description[16];
284 struct keyring_search_context ctx = {
285 .index_key.type = &key_type_request_key_auth,
286 .index_key.description = description,
287 .cred = current_cred(),
288 .match_data.cmp = key_default_cmp,
289 .match_data.raw_data = description,
290 .match_data.lookup_type = KEYRING_SEARCH_LOOKUP_DIRECT,
291 .flags = (KEYRING_SEARCH_DO_STATE_CHECK |
292 KEYRING_SEARCH_RECURSE),
293 };
294 struct key *authkey;
295 key_ref_t authkey_ref;
296
297 ctx.index_key.desc_len = sprintf(description, "%x", target_id);
298
299 rcu_read_lock();
300 authkey_ref = search_process_keyrings_rcu(&ctx);
301 rcu_read_unlock();
302
303 if (IS_ERR(authkey_ref)) {
304 authkey = ERR_CAST(authkey_ref);
305 if (authkey == ERR_PTR(-EAGAIN))
306 authkey = ERR_PTR(-ENOKEY);
307 goto error;
308 }
309
310 authkey = key_ref_to_ptr(authkey_ref);
311 if (test_bit(KEY_FLAG_REVOKED, &authkey->flags)) {
312 key_put(authkey);
313 authkey = ERR_PTR(-EKEYREVOKED);
314 }
315
316error:
317 return authkey;
318}