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
request_key_auth_preparse(struct key_preparsed_payload * prep)42 static int request_key_auth_preparse(struct key_preparsed_payload *prep)
43 {
44 return 0;
45 }
46
request_key_auth_free_preparse(struct key_preparsed_payload * prep)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 */
request_key_auth_instantiate(struct key * key,struct key_preparsed_payload * prep)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 */
request_key_auth_describe(const struct key * key,struct seq_file * m)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 if (!rka)
70 return;
71
72 seq_puts(m, "key:");
73 seq_puts(m, key->description);
74 if (key_is_positive(key))
75 seq_printf(m, " pid:%d ci:%zu", rka->pid, rka->callout_len);
76 }
77
78 /*
79 * Read the callout_info data (retrieves the callout information).
80 * - the key's semaphore is read-locked
81 */
request_key_auth_read(const struct key * key,char __user * buffer,size_t buflen)82 static long request_key_auth_read(const struct key *key,
83 char __user *buffer, size_t buflen)
84 {
85 struct request_key_auth *rka = dereference_key_locked(key);
86 size_t datalen;
87 long ret;
88
89 if (!rka)
90 return -EKEYREVOKED;
91
92 datalen = rka->callout_len;
93 ret = datalen;
94
95 /* we can return the data as is */
96 if (buffer && buflen > 0) {
97 if (buflen > datalen)
98 buflen = datalen;
99
100 if (copy_to_user(buffer, rka->callout_info, buflen) != 0)
101 ret = -EFAULT;
102 }
103
104 return ret;
105 }
106
free_request_key_auth(struct request_key_auth * rka)107 static void free_request_key_auth(struct request_key_auth *rka)
108 {
109 if (!rka)
110 return;
111 key_put(rka->target_key);
112 key_put(rka->dest_keyring);
113 if (rka->cred)
114 put_cred(rka->cred);
115 kfree(rka->callout_info);
116 kfree(rka);
117 }
118
119 /*
120 * Dispose of the request_key_auth record under RCU conditions
121 */
request_key_auth_rcu_disposal(struct rcu_head * rcu)122 static void request_key_auth_rcu_disposal(struct rcu_head *rcu)
123 {
124 struct request_key_auth *rka =
125 container_of(rcu, struct request_key_auth, rcu);
126
127 free_request_key_auth(rka);
128 }
129
130 /*
131 * Handle revocation of an authorisation token key.
132 *
133 * Called with the key sem write-locked.
134 */
request_key_auth_revoke(struct key * key)135 static void request_key_auth_revoke(struct key *key)
136 {
137 struct request_key_auth *rka = dereference_key_locked(key);
138
139 kenter("{%d}", key->serial);
140 rcu_assign_keypointer(key, NULL);
141 call_rcu(&rka->rcu, request_key_auth_rcu_disposal);
142 }
143
144 /*
145 * Destroy an instantiation authorisation token key.
146 */
request_key_auth_destroy(struct key * key)147 static void request_key_auth_destroy(struct key *key)
148 {
149 struct request_key_auth *rka = rcu_access_pointer(key->payload.rcu_data0);
150
151 kenter("{%d}", key->serial);
152 if (rka) {
153 rcu_assign_keypointer(key, NULL);
154 call_rcu(&rka->rcu, request_key_auth_rcu_disposal);
155 }
156 }
157
158 /*
159 * Create an authorisation token for /sbin/request-key or whoever to gain
160 * access to the caller's security data.
161 */
request_key_auth_new(struct key * target,const char * op,const void * callout_info,size_t callout_len,struct key * dest_keyring)162 struct key *request_key_auth_new(struct key *target, const char *op,
163 const void *callout_info, size_t callout_len,
164 struct key *dest_keyring)
165 {
166 struct request_key_auth *rka, *irka;
167 const struct cred *cred = current_cred();
168 struct key *authkey = NULL;
169 char desc[20];
170 int ret = -ENOMEM;
171
172 kenter("%d,", target->serial);
173
174 /* allocate a auth record */
175 rka = kzalloc(sizeof(*rka), GFP_KERNEL);
176 if (!rka)
177 goto error;
178 rka->callout_info = kmemdup(callout_info, callout_len, GFP_KERNEL);
179 if (!rka->callout_info)
180 goto error_free_rka;
181 rka->callout_len = callout_len;
182 strlcpy(rka->op, op, sizeof(rka->op));
183
184 /* see if the calling process is already servicing the key request of
185 * another process */
186 if (cred->request_key_auth) {
187 /* it is - use that instantiation context here too */
188 down_read(&cred->request_key_auth->sem);
189
190 /* if the auth key has been revoked, then the key we're
191 * servicing is already instantiated */
192 if (test_bit(KEY_FLAG_REVOKED,
193 &cred->request_key_auth->flags)) {
194 up_read(&cred->request_key_auth->sem);
195 ret = -EKEYREVOKED;
196 goto error_free_rka;
197 }
198
199 irka = cred->request_key_auth->payload.data[0];
200 rka->cred = get_cred(irka->cred);
201 rka->pid = irka->pid;
202
203 up_read(&cred->request_key_auth->sem);
204 }
205 else {
206 /* it isn't - use this process as the context */
207 rka->cred = get_cred(cred);
208 rka->pid = current->pid;
209 }
210
211 rka->target_key = key_get(target);
212 rka->dest_keyring = key_get(dest_keyring);
213
214 /* allocate the auth key */
215 sprintf(desc, "%x", target->serial);
216
217 authkey = key_alloc(&key_type_request_key_auth, desc,
218 cred->fsuid, cred->fsgid, cred,
219 KEY_POS_VIEW | KEY_POS_READ | KEY_POS_SEARCH | KEY_POS_LINK |
220 KEY_USR_VIEW, KEY_ALLOC_NOT_IN_QUOTA, NULL);
221 if (IS_ERR(authkey)) {
222 ret = PTR_ERR(authkey);
223 goto error_free_rka;
224 }
225
226 /* construct the auth key */
227 ret = key_instantiate_and_link(authkey, rka, 0, NULL, NULL);
228 if (ret < 0)
229 goto error_put_authkey;
230
231 kleave(" = {%d,%d}", authkey->serial, refcount_read(&authkey->usage));
232 return authkey;
233
234 error_put_authkey:
235 key_put(authkey);
236 error_free_rka:
237 free_request_key_auth(rka);
238 error:
239 kleave("= %d", ret);
240 return ERR_PTR(ret);
241 }
242
243 /*
244 * Search the current process's keyrings for the authorisation key for
245 * instantiation of a key.
246 */
key_get_instantiation_authkey(key_serial_t target_id)247 struct key *key_get_instantiation_authkey(key_serial_t target_id)
248 {
249 char description[16];
250 struct keyring_search_context ctx = {
251 .index_key.type = &key_type_request_key_auth,
252 .index_key.description = description,
253 .cred = current_cred(),
254 .match_data.cmp = key_default_cmp,
255 .match_data.raw_data = description,
256 .match_data.lookup_type = KEYRING_SEARCH_LOOKUP_DIRECT,
257 .flags = (KEYRING_SEARCH_DO_STATE_CHECK |
258 KEYRING_SEARCH_RECURSE),
259 };
260 struct key *authkey;
261 key_ref_t authkey_ref;
262
263 ctx.index_key.desc_len = sprintf(description, "%x", target_id);
264
265 rcu_read_lock();
266 authkey_ref = search_process_keyrings_rcu(&ctx);
267 rcu_read_unlock();
268
269 if (IS_ERR(authkey_ref)) {
270 authkey = ERR_CAST(authkey_ref);
271 if (authkey == ERR_PTR(-EAGAIN))
272 authkey = ERR_PTR(-ENOKEY);
273 goto error;
274 }
275
276 authkey = key_ref_to_ptr(authkey_ref);
277 if (test_bit(KEY_FLAG_REVOKED, &authkey->flags)) {
278 key_put(authkey);
279 authkey = ERR_PTR(-EKEYREVOKED);
280 }
281
282 error:
283 return authkey;
284 }
285