e73ec040e2509494d3d123ad8c47419b747a33f7
[sfrench/cifs-2.6.git] / security / keys / request_key_auth.c
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 (dhowells@redhat.com)
6  *
7  * See Documentation/security/keys/request-key.rst
8  */
9
10 #include <linux/sched.h>
11 #include <linux/err.h>
12 #include <linux/seq_file.h>
13 #include <linux/slab.h>
14 #include <linux/uaccess.h>
15 #include "internal.h"
16 #include <keys/request_key_auth-type.h>
17
18 static int request_key_auth_preparse(struct key_preparsed_payload *);
19 static void request_key_auth_free_preparse(struct key_preparsed_payload *);
20 static int request_key_auth_instantiate(struct key *,
21                                         struct key_preparsed_payload *);
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         .preparse       = request_key_auth_preparse,
34         .free_preparse  = request_key_auth_free_preparse,
35         .instantiate    = request_key_auth_instantiate,
36         .describe       = request_key_auth_describe,
37         .revoke         = request_key_auth_revoke,
38         .destroy        = request_key_auth_destroy,
39         .read           = request_key_auth_read,
40 };
41
42 static int request_key_auth_preparse(struct key_preparsed_payload *prep)
43 {
44         return 0;
45 }
46
47 static void request_key_auth_free_preparse(struct key_preparsed_payload *prep)
48 {
49 }
50
51 /*
52  * Instantiate a request-key authorisation key.
53  */
54 static int request_key_auth_instantiate(struct key *key,
55                                         struct key_preparsed_payload *prep)
56 {
57         rcu_assign_keypointer(key, (struct request_key_auth *)prep->data);
58         return 0;
59 }
60
61 /*
62  * Describe an authorisation token.
63  */
64 static void request_key_auth_describe(const struct key *key,
65                                       struct seq_file *m)
66 {
67         struct request_key_auth *rka = dereference_key_rcu(key);
68
69         seq_puts(m, "key:");
70         seq_puts(m, key->description);
71         if (key_is_positive(key))
72                 seq_printf(m, " pid:%d ci:%zu", rka->pid, rka->callout_len);
73 }
74
75 /*
76  * Read the callout_info data (retrieves the callout information).
77  * - the key's semaphore is read-locked
78  */
79 static long request_key_auth_read(const struct key *key,
80                                   char __user *buffer, size_t buflen)
81 {
82         struct request_key_auth *rka = dereference_key_locked(key);
83         size_t datalen;
84         long ret;
85
86         datalen = rka->callout_len;
87         ret = datalen;
88
89         /* we can return the data as is */
90         if (buffer && buflen > 0) {
91                 if (buflen > datalen)
92                         buflen = datalen;
93
94                 if (copy_to_user(buffer, rka->callout_info, buflen) != 0)
95                         ret = -EFAULT;
96         }
97
98         return ret;
99 }
100
101 static void free_request_key_auth(struct request_key_auth *rka)
102 {
103         if (!rka)
104                 return;
105         key_put(rka->target_key);
106         key_put(rka->dest_keyring);
107         if (rka->cred)
108                 put_cred(rka->cred);
109         kfree(rka->callout_info);
110         kfree(rka);
111 }
112
113 /*
114  * Dispose of the request_key_auth record under RCU conditions
115  */
116 static void request_key_auth_rcu_disposal(struct rcu_head *rcu)
117 {
118         struct request_key_auth *rka =
119                 container_of(rcu, struct request_key_auth, rcu);
120
121         free_request_key_auth(rka);
122 }
123
124 /*
125  * Handle revocation of an authorisation token key.
126  *
127  * Called with the key sem write-locked.
128  */
129 static void request_key_auth_revoke(struct key *key)
130 {
131         struct request_key_auth *rka = dereference_key_locked(key);
132
133         kenter("{%d}", key->serial);
134         rcu_assign_keypointer(key, NULL);
135         call_rcu(&rka->rcu, request_key_auth_rcu_disposal);
136 }
137
138 /*
139  * Destroy an instantiation authorisation token key.
140  */
141 static void request_key_auth_destroy(struct key *key)
142 {
143         struct request_key_auth *rka = rcu_access_pointer(key->payload.rcu_data0);
144
145         kenter("{%d}", key->serial);
146         if (rka) {
147                 rcu_assign_keypointer(key, NULL);
148                 call_rcu(&rka->rcu, request_key_auth_rcu_disposal);
149         }
150 }
151
152 /*
153  * Create an authorisation token for /sbin/request-key or whoever to gain
154  * access to the caller's security data.
155  */
156 struct key *request_key_auth_new(struct key *target, const char *op,
157                                  const void *callout_info, size_t callout_len,
158                                  struct key *dest_keyring)
159 {
160         struct request_key_auth *rka, *irka;
161         const struct cred *cred = current_cred();
162         struct key *authkey = NULL;
163         char desc[20];
164         int ret = -ENOMEM;
165
166         kenter("%d,", target->serial);
167
168         /* allocate a auth record */
169         rka = kzalloc(sizeof(*rka), GFP_KERNEL);
170         if (!rka)
171                 goto error;
172         rka->callout_info = kmemdup(callout_info, callout_len, GFP_KERNEL);
173         if (!rka->callout_info)
174                 goto error_free_rka;
175         rka->callout_len = callout_len;
176         strlcpy(rka->op, op, sizeof(rka->op));
177
178         /* see if the calling process is already servicing the key request of
179          * another process */
180         if (cred->request_key_auth) {
181                 /* it is - use that instantiation context here too */
182                 down_read(&cred->request_key_auth->sem);
183
184                 /* if the auth key has been revoked, then the key we're
185                  * servicing is already instantiated */
186                 if (test_bit(KEY_FLAG_REVOKED,
187                              &cred->request_key_auth->flags)) {
188                         up_read(&cred->request_key_auth->sem);
189                         ret = -EKEYREVOKED;
190                         goto error_free_rka;
191                 }
192
193                 irka = cred->request_key_auth->payload.data[0];
194                 rka->cred = get_cred(irka->cred);
195                 rka->pid = irka->pid;
196
197                 up_read(&cred->request_key_auth->sem);
198         }
199         else {
200                 /* it isn't - use this process as the context */
201                 rka->cred = get_cred(cred);
202                 rka->pid = current->pid;
203         }
204
205         rka->target_key = key_get(target);
206         rka->dest_keyring = key_get(dest_keyring);
207
208         /* allocate the auth key */
209         sprintf(desc, "%x", target->serial);
210
211         authkey = key_alloc(&key_type_request_key_auth, desc,
212                             cred->fsuid, cred->fsgid, cred,
213                             KEY_POS_VIEW | KEY_POS_READ | KEY_POS_SEARCH | KEY_POS_LINK |
214                             KEY_USR_VIEW, KEY_ALLOC_NOT_IN_QUOTA, NULL);
215         if (IS_ERR(authkey)) {
216                 ret = PTR_ERR(authkey);
217                 goto error_free_rka;
218         }
219
220         /* construct the auth key */
221         ret = key_instantiate_and_link(authkey, rka, 0, NULL, NULL);
222         if (ret < 0)
223                 goto error_put_authkey;
224
225         kleave(" = {%d,%d}", authkey->serial, refcount_read(&authkey->usage));
226         return authkey;
227
228 error_put_authkey:
229         key_put(authkey);
230 error_free_rka:
231         free_request_key_auth(rka);
232 error:
233         kleave("= %d", ret);
234         return ERR_PTR(ret);
235 }
236
237 /*
238  * Search the current process's keyrings for the authorisation key for
239  * instantiation of a key.
240  */
241 struct key *key_get_instantiation_authkey(key_serial_t target_id)
242 {
243         char description[16];
244         struct keyring_search_context ctx = {
245                 .index_key.type         = &key_type_request_key_auth,
246                 .index_key.description  = description,
247                 .cred                   = current_cred(),
248                 .match_data.cmp         = key_default_cmp,
249                 .match_data.raw_data    = description,
250                 .match_data.lookup_type = KEYRING_SEARCH_LOOKUP_DIRECT,
251                 .flags                  = (KEYRING_SEARCH_DO_STATE_CHECK |
252                                            KEYRING_SEARCH_RECURSE),
253         };
254         struct key *authkey;
255         key_ref_t authkey_ref;
256
257         ctx.index_key.desc_len = sprintf(description, "%x", target_id);
258
259         rcu_read_lock();
260         authkey_ref = search_process_keyrings_rcu(&ctx);
261         rcu_read_unlock();
262
263         if (IS_ERR(authkey_ref)) {
264                 authkey = ERR_CAST(authkey_ref);
265                 if (authkey == ERR_PTR(-EAGAIN))
266                         authkey = ERR_PTR(-ENOKEY);
267                 goto error;
268         }
269
270         authkey = key_ref_to_ptr(authkey_ref);
271         if (test_bit(KEY_FLAG_REVOKED, &authkey->flags)) {
272                 key_put(authkey);
273                 authkey = ERR_PTR(-EKEYREVOKED);
274         }
275
276 error:
277         return authkey;
278 }