blob: b6adb94f6d52573aecf2e38a16724e06895dded6 [file] [log] [blame]
David Howellsab3c3582013-09-24 10:35:18 +01001/* Large capacity key type
2 *
3 * Copyright (C) 2013 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 Licence
8 * as published by the Free Software Foundation; either version
9 * 2 of the Licence, or (at your option) any later version.
10 */
11
12#include <linux/module.h>
13#include <linux/init.h>
14#include <linux/seq_file.h>
15#include <linux/file.h>
16#include <linux/shmem_fs.h>
17#include <linux/err.h>
18#include <keys/user-type.h>
19#include <keys/big_key-type.h>
20
21MODULE_LICENSE("GPL");
22
23/*
24 * If the data is under this limit, there's no point creating a shm file to
25 * hold it as the permanently resident metadata for the shmem fs will be at
26 * least as large as the data.
27 */
28#define BIG_KEY_FILE_THRESHOLD (sizeof(struct inode) + sizeof(struct dentry))
29
30/*
31 * big_key defined keys take an arbitrary string as the description and an
32 * arbitrary blob of data as the payload
33 */
34struct key_type key_type_big_key = {
35 .name = "big_key",
David Howells002edaf2014-07-18 18:56:36 +010036 .preparse = big_key_preparse,
37 .free_preparse = big_key_free_preparse,
38 .instantiate = generic_key_instantiate,
David Howellsab3c3582013-09-24 10:35:18 +010039 .revoke = big_key_revoke,
40 .destroy = big_key_destroy,
41 .describe = big_key_describe,
42 .read = big_key_read,
43};
44
45/*
David Howells002edaf2014-07-18 18:56:36 +010046 * Preparse a big key
David Howellsab3c3582013-09-24 10:35:18 +010047 */
David Howells002edaf2014-07-18 18:56:36 +010048int big_key_preparse(struct key_preparsed_payload *prep)
David Howellsab3c3582013-09-24 10:35:18 +010049{
David Howells002edaf2014-07-18 18:56:36 +010050 struct path *path = (struct path *)&prep->payload;
David Howellsab3c3582013-09-24 10:35:18 +010051 struct file *file;
52 ssize_t written;
53 size_t datalen = prep->datalen;
54 int ret;
55
56 ret = -EINVAL;
57 if (datalen <= 0 || datalen > 1024 * 1024 || !prep->data)
58 goto error;
59
60 /* Set an arbitrary quota */
David Howells002edaf2014-07-18 18:56:36 +010061 prep->quotalen = 16;
David Howellsab3c3582013-09-24 10:35:18 +010062
David Howells002edaf2014-07-18 18:56:36 +010063 prep->type_data[1] = (void *)(unsigned long)datalen;
David Howellsab3c3582013-09-24 10:35:18 +010064
65 if (datalen > BIG_KEY_FILE_THRESHOLD) {
66 /* Create a shmem file to store the data in. This will permit the data
67 * to be swapped out if needed.
68 *
69 * TODO: Encrypt the stored data with a temporary key.
70 */
Eric Parisc7277092013-12-02 11:24:19 +000071 file = shmem_kernel_file_setup("", datalen, 0);
Wei Yongjund2b86972013-10-30 11:23:02 +080072 if (IS_ERR(file)) {
73 ret = PTR_ERR(file);
David Howells002edaf2014-07-18 18:56:36 +010074 goto error;
Wei Yongjund2b86972013-10-30 11:23:02 +080075 }
David Howellsab3c3582013-09-24 10:35:18 +010076
77 written = kernel_write(file, prep->data, prep->datalen, 0);
78 if (written != datalen) {
David Howells97826c82013-11-13 16:51:06 +000079 ret = written;
David Howellsab3c3582013-09-24 10:35:18 +010080 if (written >= 0)
81 ret = -ENOMEM;
82 goto err_fput;
83 }
84
85 /* Pin the mount and dentry to the key so that we can open it again
86 * later
87 */
88 *path = file->f_path;
89 path_get(path);
90 fput(file);
91 } else {
92 /* Just store the data in a buffer */
93 void *data = kmalloc(datalen, GFP_KERNEL);
David Howells002edaf2014-07-18 18:56:36 +010094 if (!data)
95 return -ENOMEM;
David Howellsab3c3582013-09-24 10:35:18 +010096
David Howells002edaf2014-07-18 18:56:36 +010097 prep->payload[0] = memcpy(data, prep->data, prep->datalen);
David Howellsab3c3582013-09-24 10:35:18 +010098 }
99 return 0;
100
101err_fput:
102 fput(file);
David Howellsab3c3582013-09-24 10:35:18 +0100103error:
104 return ret;
105}
106
107/*
David Howells002edaf2014-07-18 18:56:36 +0100108 * Clear preparsement.
109 */
110void big_key_free_preparse(struct key_preparsed_payload *prep)
111{
112 if (prep->datalen > BIG_KEY_FILE_THRESHOLD) {
113 struct path *path = (struct path *)&prep->payload;
114 path_put(path);
115 } else {
116 kfree(prep->payload[0]);
117 }
118}
119
120/*
David Howellsab3c3582013-09-24 10:35:18 +0100121 * dispose of the links from a revoked keyring
122 * - called with the key sem write-locked
123 */
124void big_key_revoke(struct key *key)
125{
126 struct path *path = (struct path *)&key->payload.data2;
127
128 /* clear the quota */
129 key_payload_reserve(key, 0);
130 if (key_is_instantiated(key) && key->type_data.x[1] > BIG_KEY_FILE_THRESHOLD)
131 vfs_truncate(path, 0);
132}
133
134/*
135 * dispose of the data dangling from the corpse of a big_key key
136 */
137void big_key_destroy(struct key *key)
138{
139 if (key->type_data.x[1] > BIG_KEY_FILE_THRESHOLD) {
140 struct path *path = (struct path *)&key->payload.data2;
141 path_put(path);
142 path->mnt = NULL;
143 path->dentry = NULL;
144 } else {
145 kfree(key->payload.data);
146 key->payload.data = NULL;
147 }
148}
149
150/*
151 * describe the big_key key
152 */
153void big_key_describe(const struct key *key, struct seq_file *m)
154{
155 unsigned long datalen = key->type_data.x[1];
156
157 seq_puts(m, key->description);
158
159 if (key_is_instantiated(key))
160 seq_printf(m, ": %lu [%s]",
161 datalen,
162 datalen > BIG_KEY_FILE_THRESHOLD ? "file" : "buff");
163}
164
165/*
166 * read the key data
167 * - the key's semaphore is read-locked
168 */
169long big_key_read(const struct key *key, char __user *buffer, size_t buflen)
170{
171 unsigned long datalen = key->type_data.x[1];
172 long ret;
173
174 if (!buffer || buflen < datalen)
175 return datalen;
176
177 if (datalen > BIG_KEY_FILE_THRESHOLD) {
178 struct path *path = (struct path *)&key->payload.data2;
179 struct file *file;
180 loff_t pos;
181
182 file = dentry_open(path, O_RDONLY, current_cred());
183 if (IS_ERR(file))
184 return PTR_ERR(file);
185
186 pos = 0;
187 ret = vfs_read(file, buffer, datalen, &pos);
188 fput(file);
189 if (ret >= 0 && ret != datalen)
190 ret = -EIO;
191 } else {
192 ret = datalen;
193 if (copy_to_user(buffer, key->payload.data, datalen) != 0)
194 ret = -EFAULT;
195 }
196
197 return ret;
198}
199
200/*
201 * Module stuff
202 */
203static int __init big_key_init(void)
204{
205 return register_key_type(&key_type_big_key);
206}
207
208static void __exit big_key_cleanup(void)
209{
210 unregister_key_type(&key_type_big_key);
211}
212
213module_init(big_key_init);
214module_exit(big_key_cleanup);