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