1 /* request_key_auth.c: request key authorisation controlling key def
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/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 <asm/uaccess.h>
19 #include "internal.h"
20 
21 static int request_key_auth_instantiate(struct key *, const void *, size_t);
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 	.instantiate	= request_key_auth_instantiate,
34 	.describe	= request_key_auth_describe,
35 	.revoke		= request_key_auth_revoke,
36 	.destroy	= request_key_auth_destroy,
37 	.read		= request_key_auth_read,
38 };
39 
40 /*****************************************************************************/
41 /*
42  * instantiate a request-key authorisation key
43  */
44 static int request_key_auth_instantiate(struct key *key,
45 					const void *data,
46 					size_t datalen)
47 {
48 	key->payload.data = (struct request_key_auth *) data;
49 	return 0;
50 
51 } /* end request_key_auth_instantiate() */
52 
53 /*****************************************************************************/
54 /*
55  * reading a request-key authorisation key retrieves the callout information
56  */
57 static void request_key_auth_describe(const struct key *key,
58 				      struct seq_file *m)
59 {
60 	struct request_key_auth *rka = key->payload.data;
61 
62 	seq_puts(m, "key:");
63 	seq_puts(m, key->description);
64 	seq_printf(m, " pid:%d ci:%zu", rka->pid, strlen(rka->callout_info));
65 
66 } /* end request_key_auth_describe() */
67 
68 /*****************************************************************************/
69 /*
70  * read the callout_info data
71  * - the key's semaphore is read-locked
72  */
73 static long request_key_auth_read(const struct key *key,
74 				  char __user *buffer, size_t buflen)
75 {
76 	struct request_key_auth *rka = key->payload.data;
77 	size_t datalen;
78 	long ret;
79 
80 	datalen = strlen(rka->callout_info);
81 	ret = datalen;
82 
83 	/* we can return the data as is */
84 	if (buffer && buflen > 0) {
85 		if (buflen > datalen)
86 			buflen = datalen;
87 
88 		if (copy_to_user(buffer, rka->callout_info, buflen) != 0)
89 			ret = -EFAULT;
90 	}
91 
92 	return ret;
93 
94 } /* end request_key_auth_read() */
95 
96 /*****************************************************************************/
97 /*
98  * handle revocation of an authorisation token key
99  * - called with the key sem write-locked
100  */
101 static void request_key_auth_revoke(struct key *key)
102 {
103 	struct request_key_auth *rka = key->payload.data;
104 
105 	kenter("{%d}", key->serial);
106 
107 	if (rka->context) {
108 		put_task_struct(rka->context);
109 		rka->context = NULL;
110 	}
111 
112 } /* end request_key_auth_revoke() */
113 
114 /*****************************************************************************/
115 /*
116  * destroy an instantiation authorisation token key
117  */
118 static void request_key_auth_destroy(struct key *key)
119 {
120 	struct request_key_auth *rka = key->payload.data;
121 
122 	kenter("{%d}", key->serial);
123 
124 	if (rka->context) {
125 		put_task_struct(rka->context);
126 		rka->context = NULL;
127 	}
128 
129 	key_put(rka->target_key);
130 	kfree(rka->callout_info);
131 	kfree(rka);
132 
133 } /* end request_key_auth_destroy() */
134 
135 /*****************************************************************************/
136 /*
137  * create an authorisation token for /sbin/request-key or whoever to gain
138  * access to the caller's security data
139  */
140 struct key *request_key_auth_new(struct key *target, const char *callout_info)
141 {
142 	struct request_key_auth *rka, *irka;
143 	struct key *authkey = NULL;
144 	char desc[20];
145 	int ret;
146 
147 	kenter("%d,", target->serial);
148 
149 	/* allocate a auth record */
150 	rka = kmalloc(sizeof(*rka), GFP_KERNEL);
151 	if (!rka) {
152 		kleave(" = -ENOMEM");
153 		return ERR_PTR(-ENOMEM);
154 	}
155 	rka->callout_info = kmalloc(strlen(callout_info) + 1, GFP_KERNEL);
156 	if (!rka->callout_info) {
157 		kleave(" = -ENOMEM");
158 		kfree(rka);
159 		return ERR_PTR(-ENOMEM);
160 	}
161 
162 	/* see if the calling process is already servicing the key request of
163 	 * another process */
164 	if (current->request_key_auth) {
165 		/* it is - use that instantiation context here too */
166 		down_read(&current->request_key_auth->sem);
167 
168 		/* if the auth key has been revoked, then the key we're
169 		 * servicing is already instantiated */
170 		if (test_bit(KEY_FLAG_REVOKED,
171 			     &current->request_key_auth->flags))
172 			goto auth_key_revoked;
173 
174 		irka = current->request_key_auth->payload.data;
175 		rka->context = irka->context;
176 		rka->pid = irka->pid;
177 		get_task_struct(rka->context);
178 
179 		up_read(&current->request_key_auth->sem);
180 	}
181 	else {
182 		/* it isn't - use this process as the context */
183 		rka->context = current;
184 		rka->pid = current->pid;
185 		get_task_struct(rka->context);
186 	}
187 
188 	rka->target_key = key_get(target);
189 	strcpy(rka->callout_info, callout_info);
190 
191 	/* allocate the auth key */
192 	sprintf(desc, "%x", target->serial);
193 
194 	authkey = key_alloc(&key_type_request_key_auth, desc,
195 			    current->fsuid, current->fsgid, current,
196 			    KEY_POS_VIEW | KEY_POS_READ | KEY_POS_SEARCH |
197 			    KEY_USR_VIEW, KEY_ALLOC_NOT_IN_QUOTA);
198 	if (IS_ERR(authkey)) {
199 		ret = PTR_ERR(authkey);
200 		goto error_alloc;
201 	}
202 
203 	/* construct and attach to the keyring */
204 	ret = key_instantiate_and_link(authkey, rka, 0, NULL, NULL);
205 	if (ret < 0)
206 		goto error_inst;
207 
208 	kleave(" = {%d}", authkey->serial);
209 	return authkey;
210 
211 auth_key_revoked:
212 	up_read(&current->request_key_auth->sem);
213 	kfree(rka->callout_info);
214 	kfree(rka);
215 	kleave("= -EKEYREVOKED");
216 	return ERR_PTR(-EKEYREVOKED);
217 
218 error_inst:
219 	key_revoke(authkey);
220 	key_put(authkey);
221 error_alloc:
222 	key_put(rka->target_key);
223 	kfree(rka->callout_info);
224 	kfree(rka);
225 	kleave("= %d", ret);
226 	return ERR_PTR(ret);
227 
228 } /* end request_key_auth_new() */
229 
230 /*****************************************************************************/
231 /*
232  * see if an authorisation key is associated with a particular key
233  */
234 static int key_get_instantiation_authkey_match(const struct key *key,
235 					       const void *_id)
236 {
237 	struct request_key_auth *rka = key->payload.data;
238 	key_serial_t id = (key_serial_t)(unsigned long) _id;
239 
240 	return rka->target_key->serial == id;
241 
242 } /* end key_get_instantiation_authkey_match() */
243 
244 /*****************************************************************************/
245 /*
246  * get the authorisation key for instantiation of a specific key if attached to
247  * the current process's keyrings
248  * - this key is inserted into a keyring and that is set as /sbin/request-key's
249  *   session keyring
250  * - a target_id of zero specifies any valid token
251  */
252 struct key *key_get_instantiation_authkey(key_serial_t target_id)
253 {
254 	struct key *authkey;
255 	key_ref_t authkey_ref;
256 
257 	authkey_ref = search_process_keyrings(
258 		&key_type_request_key_auth,
259 		(void *) (unsigned long) target_id,
260 		key_get_instantiation_authkey_match,
261 		current);
262 
263 	if (IS_ERR(authkey_ref)) {
264 		authkey = ERR_CAST(authkey_ref);
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 } /* end key_get_instantiation_authkey() */
278