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.txt
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 <asm/uaccess.h>
20 #include "internal.h"
21
22 static int request_key_auth_instantiate(struct key *,
23 struct key_preparsed_payload *);
24 static void request_key_auth_describe(const struct key *, struct seq_file *);
25 static void request_key_auth_revoke(struct key *);
26 static void request_key_auth_destroy(struct key *);
27 static long request_key_auth_read(const struct key *, char __user *, size_t);
28
29 /*
30 * The request-key authorisation key type definition.
31 */
32 struct key_type key_type_request_key_auth = {
33 .name = ".request_key_auth",
34 .def_datalen = sizeof(struct request_key_auth),
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 /*
43 * Instantiate a request-key authorisation key.
44 */
request_key_auth_instantiate(struct key * key,struct key_preparsed_payload * prep)45 static int request_key_auth_instantiate(struct key *key,
46 struct key_preparsed_payload *prep)
47 {
48 key->payload.data = (struct request_key_auth *)prep->data;
49 return 0;
50 }
51
52 /*
53 * Describe an authorisation token.
54 */
request_key_auth_describe(const struct key * key,struct seq_file * m)55 static void request_key_auth_describe(const struct key *key,
56 struct seq_file *m)
57 {
58 struct request_key_auth *rka = key->payload.data;
59
60 seq_puts(m, "key:");
61 seq_puts(m, key->description);
62 if (key_is_instantiated(key))
63 seq_printf(m, " pid:%d ci:%zu", rka->pid, rka->callout_len);
64 }
65
66 /*
67 * Read the callout_info data (retrieves the callout information).
68 * - the key's semaphore is read-locked
69 */
request_key_auth_read(const struct key * key,char __user * buffer,size_t buflen)70 static long request_key_auth_read(const struct key *key,
71 char __user *buffer, size_t buflen)
72 {
73 struct request_key_auth *rka = key->payload.data;
74 size_t datalen;
75 long ret;
76
77 datalen = rka->callout_len;
78 ret = datalen;
79
80 /* we can return the data as is */
81 if (buffer && buflen > 0) {
82 if (buflen > datalen)
83 buflen = datalen;
84
85 if (copy_to_user(buffer, rka->callout_info, buflen) != 0)
86 ret = -EFAULT;
87 }
88
89 return ret;
90 }
91
92 /*
93 * Handle revocation of an authorisation token key.
94 *
95 * Called with the key sem write-locked.
96 */
request_key_auth_revoke(struct key * key)97 static void request_key_auth_revoke(struct key *key)
98 {
99 struct request_key_auth *rka = key->payload.data;
100
101 kenter("{%d}", key->serial);
102
103 if (rka->cred) {
104 put_cred(rka->cred);
105 rka->cred = NULL;
106 }
107 }
108
109 /*
110 * Destroy an instantiation authorisation token key.
111 */
request_key_auth_destroy(struct key * key)112 static void request_key_auth_destroy(struct key *key)
113 {
114 struct request_key_auth *rka = key->payload.data;
115
116 kenter("{%d}", key->serial);
117
118 if (rka->cred) {
119 put_cred(rka->cred);
120 rka->cred = NULL;
121 }
122
123 key_put(rka->target_key);
124 key_put(rka->dest_keyring);
125 kfree(rka->callout_info);
126 kfree(rka);
127 }
128
129 /*
130 * Create an authorisation token for /sbin/request-key or whoever to gain
131 * access to the caller's security data.
132 */
request_key_auth_new(struct key * target,const void * callout_info,size_t callout_len,struct key * dest_keyring)133 struct key *request_key_auth_new(struct key *target, const void *callout_info,
134 size_t callout_len, struct key *dest_keyring)
135 {
136 struct request_key_auth *rka, *irka;
137 const struct cred *cred = current->cred;
138 struct key *authkey = NULL;
139 char desc[20];
140 int ret;
141
142 kenter("%d,", target->serial);
143
144 /* allocate a auth record */
145 rka = kmalloc(sizeof(*rka), GFP_KERNEL);
146 if (!rka) {
147 kleave(" = -ENOMEM");
148 return ERR_PTR(-ENOMEM);
149 }
150 rka->callout_info = kmalloc(callout_len, GFP_KERNEL);
151 if (!rka->callout_info) {
152 kleave(" = -ENOMEM");
153 kfree(rka);
154 return ERR_PTR(-ENOMEM);
155 }
156
157 /* see if the calling process is already servicing the key request of
158 * another process */
159 if (cred->request_key_auth) {
160 /* it is - use that instantiation context here too */
161 down_read(&cred->request_key_auth->sem);
162
163 /* if the auth key has been revoked, then the key we're
164 * servicing is already instantiated */
165 if (test_bit(KEY_FLAG_REVOKED, &cred->request_key_auth->flags))
166 goto auth_key_revoked;
167
168 irka = cred->request_key_auth->payload.data;
169 rka->cred = get_cred(irka->cred);
170 rka->pid = irka->pid;
171
172 up_read(&cred->request_key_auth->sem);
173 }
174 else {
175 /* it isn't - use this process as the context */
176 rka->cred = get_cred(cred);
177 rka->pid = current->pid;
178 }
179
180 rka->target_key = key_get(target);
181 rka->dest_keyring = key_get(dest_keyring);
182 memcpy(rka->callout_info, callout_info, callout_len);
183 rka->callout_len = callout_len;
184
185 /* allocate the auth key */
186 sprintf(desc, "%x", target->serial);
187
188 authkey = key_alloc(&key_type_request_key_auth, desc,
189 cred->fsuid, cred->fsgid, cred,
190 KEY_POS_VIEW | KEY_POS_READ | KEY_POS_SEARCH |
191 KEY_USR_VIEW, KEY_ALLOC_NOT_IN_QUOTA);
192 if (IS_ERR(authkey)) {
193 ret = PTR_ERR(authkey);
194 goto error_alloc;
195 }
196
197 /* construct the auth key */
198 ret = key_instantiate_and_link(authkey, rka, 0, NULL, NULL);
199 if (ret < 0)
200 goto error_inst;
201
202 kleave(" = {%d,%d}", authkey->serial, atomic_read(&authkey->usage));
203 return authkey;
204
205 auth_key_revoked:
206 up_read(&cred->request_key_auth->sem);
207 kfree(rka->callout_info);
208 kfree(rka);
209 kleave("= -EKEYREVOKED");
210 return ERR_PTR(-EKEYREVOKED);
211
212 error_inst:
213 key_revoke(authkey);
214 key_put(authkey);
215 error_alloc:
216 key_put(rka->target_key);
217 key_put(rka->dest_keyring);
218 kfree(rka->callout_info);
219 kfree(rka);
220 kleave("= %d", ret);
221 return ERR_PTR(ret);
222 }
223
224 /*
225 * See if an authorisation key is associated with a particular key.
226 */
key_get_instantiation_authkey_match(const struct key * key,const void * _id)227 static int key_get_instantiation_authkey_match(const struct key *key,
228 const void *_id)
229 {
230 struct request_key_auth *rka = key->payload.data;
231 key_serial_t id = (key_serial_t)(unsigned long) _id;
232
233 return rka->target_key->serial == id;
234 }
235
236 /*
237 * Search the current process's keyrings for the authorisation key for
238 * instantiation of a key.
239 */
key_get_instantiation_authkey(key_serial_t target_id)240 struct key *key_get_instantiation_authkey(key_serial_t target_id)
241 {
242 const struct cred *cred = current_cred();
243 struct key *authkey;
244 key_ref_t authkey_ref;
245
246 authkey_ref = search_process_keyrings(
247 &key_type_request_key_auth,
248 (void *) (unsigned long) target_id,
249 key_get_instantiation_authkey_match,
250 cred);
251
252 if (IS_ERR(authkey_ref)) {
253 authkey = ERR_CAST(authkey_ref);
254 if (authkey == ERR_PTR(-EAGAIN))
255 authkey = ERR_PTR(-ENOKEY);
256 goto error;
257 }
258
259 authkey = key_ref_to_ptr(authkey_ref);
260 if (test_bit(KEY_FLAG_REVOKED, &authkey->flags)) {
261 key_put(authkey);
262 authkey = ERR_PTR(-EKEYREVOKED);
263 }
264
265 error:
266 return authkey;
267 }
268