aboutsummaryrefslogtreecommitdiffstats
path: root/security/keys/user_defined.c
blob: e446acba73d325a1d222a0a130c7f23f6a4232a9 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
/* user_defined.c: user defined key type
 *
 * Copyright (C) 2004 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version
 * 2 of the License, or (at your option) any later version.
 */

#include <linux/module.h>
#include <linux/init.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/seq_file.h>
#include <linux/err.h>
#include <asm/uaccess.h>
#include "internal.h"

static int user_instantiate(struct key *key, const void *data, size_t datalen);
static int user_duplicate(struct key *key, const struct key *source);
static int user_update(struct key *key, const void *data, size_t datalen);
static int user_match(const struct key *key, const void *criterion);
static void user_destroy(struct key *key);
static void user_describe(const struct key *user, struct seq_file *m);
static long user_read(const struct key *key,
		      char __user *buffer, size_t buflen);

/*
 * user defined keys take an arbitrary string as the description and an
 * arbitrary blob of data as the payload
 */
struct key_type key_type_user = {
	.name		= "user",
	.instantiate	= user_instantiate,
	.duplicate	= user_duplicate,
	.update		= user_update,
	.match		= user_match,
	.destroy	= user_destroy,
	.describe	= user_describe,
	.read		= user_read,
};

struct user_key_payload {
	struct rcu_head	rcu;		/* RCU destructor */
	unsigned short	datalen;	/* length of this data */
	char		data[0];	/* actual data */
};

EXPORT_SYMBOL_GPL(key_type_user);

/*****************************************************************************/
/*
 * instantiate a user defined key
 */
static int user_instantiate(struct key *key, const void *data, size_t datalen)
{
	struct user_key_payload *upayload;
	int ret;

	ret = -EINVAL;
	if (datalen <= 0 || datalen > 32767 || !data)
		goto error;

	ret = key_payload_reserve(key, datalen);
	if (ret < 0)
		goto error;

	ret = -ENOMEM;
	upayload = kmalloc(sizeof(*upayload) + datalen, GFP_KERNEL);
	if (!upayload)
		goto error;

	/* attach the data */
	upayload->datalen = datalen;
	memcpy(upayload->data, data, datalen);
	rcu_assign_pointer(key->payload.data, upayload);
	ret = 0;

 error:
	return ret;

} /* end user_instantiate() */

/*****************************************************************************/
/*
 * duplicate a user defined key
 * - both keys' semaphores are locked against further modification
 * - the new key cannot yet be accessed
 */
static int user_duplicate(struct key *key, const struct key *source)
{
	struct user_key_payload *upayload, *spayload;
	int ret;

	/* just copy the payload */
	ret = -ENOMEM;
	upayload = kmalloc(sizeof(*upayload) + source->datalen, GFP_KERNEL);
	if (upayload) {
		spayload = rcu_dereference(source->payload.data);
		BUG_ON(source->datalen != spayload->datalen);

		upayload->datalen = key->datalen = spayload->datalen;
		memcpy(upayload->data, spayload->data, key->datalen);

		key->payload.data = upayload;
		ret = 0;
	}

	return ret;

} /* end user_duplicate() */

/*****************************************************************************/
/*
 * dispose of the old data from an updated user defined key
 */
static void user_update_rcu_disposal(struct rcu_head *rcu)
{
	struct user_key_payload *upayload;

	upayload = container_of(rcu, struct user_key_payload, rcu);

	kfree(upayload);

} /* end user_update_rcu_disposal() */

/*****************************************************************************/
/*
 * update a user defined key
 * - the key's semaphore is write-locked
 */
static int user_update(struct key *key, const void *data, size_t datalen)
{
	struct user_key_payload *upayload, *zap;
	int ret;

	ret = -EINVAL;
	if (datalen <= 0 || datalen > 32767 || !data)
		goto error;

	/* construct a replacement payload */
	ret = -ENOMEM;
	upayload = kmalloc(sizeof(*upayload) + datalen, GFP_KERNEL);
	if (!upayload)
		goto error;

	upayload->datalen = datalen;
	memcpy(upayload->data, data, datalen);

	/* check the quota and attach the new data */
	zap = upayload;

	ret = key_payload_reserve(key, datalen);

	if (ret == 0) {
		/* attach the new data, displacing the old */
		zap = key->payload.data;
		rcu_assign_pointer(key->payload.data, upayload);
		key->expiry = 0;
	}

	call_rcu(&zap->rcu, user_update_rcu_disposal);

 error:
	return ret;

} /* end user_update() */

/*****************************************************************************/
/*
 * match users on their name
 */
static int user_match(const struct key *key, const void *description)
{
	return strcmp(key->description, description) == 0;

} /* end user_match() */

/*****************************************************************************/
/*
 * dispose of the data dangling from the corpse of a user
 */
static void user_destroy(struct key *key)
{
	struct user_key_payload *upayload = key->payload.data;

	kfree(upayload);

} /* end user_destroy() */

/*****************************************************************************/
/*
 * describe the user key
 */
static void user_describe(const struct key *key, struct seq_file *m)
{
	seq_puts(m, key->description);

	seq_printf(m, ": %u", key->datalen);

} /* end user_describe() */

/*****************************************************************************/
/*
 * read the key data
 * - the key's semaphore is read-locked
 */
static long user_read(const struct key *key,
		      char __user *buffer, size_t buflen)
{
	struct user_key_payload *upayload;
	long ret;

	upayload = rcu_dereference(key->payload.data);
	ret = upayload->datalen;

	/* we can return the data as is */
	if (buffer && buflen > 0) {
		if (buflen > upayload->datalen)
			buflen = upayload->datalen;

		if (copy_to_user(buffer, upayload->data, buflen) != 0)
			ret = -EFAULT;
	}

	return ret;

} /* end user_read() */