1 /* Request key authorisation token key definition.
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/security/keys/request-key.rst
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 <linux/uaccess.h>
20 #include "internal.h"
21 #include <keys/request_key_auth-type.h>
22
23 static int request_key_auth_preparse(struct key_preparsed_payload *);
24 static void request_key_auth_free_preparse(struct key_preparsed_payload *);
25 static int request_key_auth_instantiate(struct key *,
26 struct key_preparsed_payload *);
27 static void request_key_auth_describe(const struct key *, struct seq_file *);
28 static void request_key_auth_revoke(struct key *);
29 static void request_key_auth_destroy(struct key *);
30 static long request_key_auth_read(const struct key *, char __user *, size_t);
31
32 /*
33 * The request-key authorisation key type definition.
34 */
35 struct key_type key_type_request_key_auth = {
36 .name = ".request_key_auth",
37 .def_datalen = sizeof(struct request_key_auth),
38 .preparse = request_key_auth_preparse,
39 .free_preparse = request_key_auth_free_preparse,
40 .instantiate = request_key_auth_instantiate,
41 .describe = request_key_auth_describe,
42 .revoke = request_key_auth_revoke,
43 .destroy = request_key_auth_destroy,
44 .read = request_key_auth_read,
45 };
46
request_key_auth_preparse(struct key_preparsed_payload * prep)47 static int request_key_auth_preparse(struct key_preparsed_payload *prep)
48 {
49 return 0;
50 }
51
request_key_auth_free_preparse(struct key_preparsed_payload * prep)52 static void request_key_auth_free_preparse(struct key_preparsed_payload *prep)
53 {
54 }
55
56 /*
57 * Instantiate a request-key authorisation key.
58 */
request_key_auth_instantiate(struct key * key,struct key_preparsed_payload * prep)59 static int request_key_auth_instantiate(struct key *key,
60 struct key_preparsed_payload *prep)
61 {
62 key->payload.data[0] = (struct request_key_auth *)prep->data;
63 return 0;
64 }
65
66 /*
67 * Describe an authorisation token.
68 */
request_key_auth_describe(const struct key * key,struct seq_file * m)69 static void request_key_auth_describe(const struct key *key,
70 struct seq_file *m)
71 {
72 struct request_key_auth *rka = get_request_key_auth(key);
73
74 if (!rka)
75 return;
76
77 seq_puts(m, "key:");
78 seq_puts(m, key->description);
79 if (key_is_positive(key))
80 seq_printf(m, " pid:%d ci:%zu", rka->pid, rka->callout_len);
81 }
82
83 /*
84 * Read the callout_info data (retrieves the callout information).
85 * - the key's semaphore is read-locked
86 */
request_key_auth_read(const struct key * key,char __user * buffer,size_t buflen)87 static long request_key_auth_read(const struct key *key,
88 char __user *buffer, size_t buflen)
89 {
90 struct request_key_auth *rka = get_request_key_auth(key);
91 size_t datalen;
92 long ret;
93
94 if (!rka)
95 return -EKEYREVOKED;
96
97 datalen = rka->callout_len;
98 ret = datalen;
99
100 /* we can return the data as is */
101 if (buffer && buflen > 0) {
102 if (buflen > datalen)
103 buflen = datalen;
104
105 if (copy_to_user(buffer, rka->callout_info, buflen) != 0)
106 ret = -EFAULT;
107 }
108
109 return ret;
110 }
111
112 /*
113 * Handle revocation of an authorisation token key.
114 *
115 * Called with the key sem write-locked.
116 */
request_key_auth_revoke(struct key * key)117 static void request_key_auth_revoke(struct key *key)
118 {
119 struct request_key_auth *rka = get_request_key_auth(key);
120
121 kenter("{%d}", key->serial);
122
123 if (rka->cred) {
124 put_cred(rka->cred);
125 rka->cred = NULL;
126 }
127 }
128
free_request_key_auth(struct request_key_auth * rka)129 static void free_request_key_auth(struct request_key_auth *rka)
130 {
131 if (!rka)
132 return;
133 key_put(rka->target_key);
134 key_put(rka->dest_keyring);
135 if (rka->cred)
136 put_cred(rka->cred);
137 kfree(rka->callout_info);
138 kfree(rka);
139 }
140
141 /*
142 * Destroy an instantiation authorisation token key.
143 */
request_key_auth_destroy(struct key * key)144 static void request_key_auth_destroy(struct key *key)
145 {
146 struct request_key_auth *rka = get_request_key_auth(key);
147
148 kenter("{%d}", key->serial);
149
150 free_request_key_auth(rka);
151 }
152
153 /*
154 * Create an authorisation token for /sbin/request-key or whoever to gain
155 * access to the caller's security data.
156 */
request_key_auth_new(struct key * target,const char * op,const void * callout_info,size_t callout_len,struct key * dest_keyring)157 struct key *request_key_auth_new(struct key *target, const char *op,
158 const void *callout_info, size_t callout_len,
159 struct key *dest_keyring)
160 {
161 struct request_key_auth *rka, *irka;
162 const struct cred *cred = current->cred;
163 struct key *authkey = NULL;
164 char desc[20];
165 int ret = -ENOMEM;
166
167 kenter("%d,", target->serial);
168
169 /* allocate a auth record */
170 rka = kzalloc(sizeof(*rka), GFP_KERNEL);
171 if (!rka)
172 goto error;
173 rka->callout_info = kmemdup(callout_info, callout_len, GFP_KERNEL);
174 if (!rka->callout_info)
175 goto error_free_rka;
176 rka->callout_len = callout_len;
177 strlcpy(rka->op, op, sizeof(rka->op));
178
179 /* see if the calling process is already servicing the key request of
180 * another process */
181 if (cred->request_key_auth) {
182 /* it is - use that instantiation context here too */
183 down_read(&cred->request_key_auth->sem);
184
185 /* if the auth key has been revoked, then the key we're
186 * servicing is already instantiated */
187 if (test_bit(KEY_FLAG_REVOKED,
188 &cred->request_key_auth->flags)) {
189 up_read(&cred->request_key_auth->sem);
190 ret = -EKEYREVOKED;
191 goto error_free_rka;
192 }
193
194 irka = cred->request_key_auth->payload.data[0];
195 rka->cred = get_cred(irka->cred);
196 rka->pid = irka->pid;
197
198 up_read(&cred->request_key_auth->sem);
199 }
200 else {
201 /* it isn't - use this process as the context */
202 rka->cred = get_cred(cred);
203 rka->pid = current->pid;
204 }
205
206 rka->target_key = key_get(target);
207 rka->dest_keyring = key_get(dest_keyring);
208
209 /* allocate the auth key */
210 sprintf(desc, "%x", target->serial);
211
212 authkey = key_alloc(&key_type_request_key_auth, desc,
213 cred->fsuid, cred->fsgid, cred,
214 KEY_POS_VIEW | KEY_POS_READ | KEY_POS_SEARCH |
215 KEY_USR_VIEW, KEY_ALLOC_NOT_IN_QUOTA, NULL);
216 if (IS_ERR(authkey)) {
217 ret = PTR_ERR(authkey);
218 goto error_free_rka;
219 }
220
221 /* construct the auth key */
222 ret = key_instantiate_and_link(authkey, rka, 0, NULL, NULL);
223 if (ret < 0)
224 goto error_put_authkey;
225
226 kleave(" = {%d,%d}", authkey->serial, refcount_read(&authkey->usage));
227 return authkey;
228
229 error_put_authkey:
230 key_put(authkey);
231 error_free_rka:
232 free_request_key_auth(rka);
233 error:
234 kleave("= %d", ret);
235 return ERR_PTR(ret);
236 }
237
238 /*
239 * Search the current process's keyrings for the authorisation key for
240 * instantiation of a key.
241 */
key_get_instantiation_authkey(key_serial_t target_id)242 struct key *key_get_instantiation_authkey(key_serial_t target_id)
243 {
244 char description[16];
245 struct keyring_search_context ctx = {
246 .index_key.type = &key_type_request_key_auth,
247 .index_key.description = description,
248 .cred = current_cred(),
249 .match_data.cmp = key_default_cmp,
250 .match_data.raw_data = description,
251 .match_data.lookup_type = KEYRING_SEARCH_LOOKUP_DIRECT,
252 .flags = KEYRING_SEARCH_DO_STATE_CHECK,
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 authkey_ref = search_process_keyrings(&ctx);
260
261 if (IS_ERR(authkey_ref)) {
262 authkey = ERR_CAST(authkey_ref);
263 if (authkey == ERR_PTR(-EAGAIN))
264 authkey = ERR_PTR(-ENOKEY);
265 goto error;
266 }
267
268 authkey = key_ref_to_ptr(authkey_ref);
269 if (test_bit(KEY_FLAG_REVOKED, &authkey->flags)) {
270 key_put(authkey);
271 authkey = ERR_PTR(-EKEYREVOKED);
272 }
273
274 error:
275 return authkey;
276 }
277