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ab3c3587 DH |
1 | /* 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 | ||
21 | MODULE_LICENSE("GPL"); | |
22 | ||
146aa8b1 DH |
23 | /* |
24 | * Layout of key payload words. | |
25 | */ | |
26 | enum { | |
27 | big_key_data, | |
28 | big_key_path, | |
29 | big_key_path_2nd_part, | |
30 | big_key_len, | |
31 | }; | |
32 | ||
ab3c3587 DH |
33 | /* |
34 | * If the data is under this limit, there's no point creating a shm file to | |
35 | * hold it as the permanently resident metadata for the shmem fs will be at | |
36 | * least as large as the data. | |
37 | */ | |
38 | #define BIG_KEY_FILE_THRESHOLD (sizeof(struct inode) + sizeof(struct dentry)) | |
39 | ||
40 | /* | |
41 | * big_key defined keys take an arbitrary string as the description and an | |
42 | * arbitrary blob of data as the payload | |
43 | */ | |
44 | struct key_type key_type_big_key = { | |
45 | .name = "big_key", | |
002edaf7 DH |
46 | .preparse = big_key_preparse, |
47 | .free_preparse = big_key_free_preparse, | |
48 | .instantiate = generic_key_instantiate, | |
ab3c3587 DH |
49 | .revoke = big_key_revoke, |
50 | .destroy = big_key_destroy, | |
51 | .describe = big_key_describe, | |
52 | .read = big_key_read, | |
53 | }; | |
54 | ||
55 | /* | |
002edaf7 | 56 | * Preparse a big key |
ab3c3587 | 57 | */ |
002edaf7 | 58 | int big_key_preparse(struct key_preparsed_payload *prep) |
ab3c3587 | 59 | { |
146aa8b1 | 60 | struct path *path = (struct path *)&prep->payload.data[big_key_path]; |
ab3c3587 DH |
61 | struct file *file; |
62 | ssize_t written; | |
63 | size_t datalen = prep->datalen; | |
64 | int ret; | |
65 | ||
66 | ret = -EINVAL; | |
67 | if (datalen <= 0 || datalen > 1024 * 1024 || !prep->data) | |
68 | goto error; | |
69 | ||
70 | /* Set an arbitrary quota */ | |
002edaf7 | 71 | prep->quotalen = 16; |
ab3c3587 | 72 | |
146aa8b1 | 73 | prep->payload.data[big_key_len] = (void *)(unsigned long)datalen; |
ab3c3587 DH |
74 | |
75 | if (datalen > BIG_KEY_FILE_THRESHOLD) { | |
76 | /* Create a shmem file to store the data in. This will permit the data | |
77 | * to be swapped out if needed. | |
78 | * | |
79 | * TODO: Encrypt the stored data with a temporary key. | |
80 | */ | |
c7277090 | 81 | file = shmem_kernel_file_setup("", datalen, 0); |
d2b86970 WY |
82 | if (IS_ERR(file)) { |
83 | ret = PTR_ERR(file); | |
002edaf7 | 84 | goto error; |
d2b86970 | 85 | } |
ab3c3587 DH |
86 | |
87 | written = kernel_write(file, prep->data, prep->datalen, 0); | |
88 | if (written != datalen) { | |
97826c82 | 89 | ret = written; |
ab3c3587 DH |
90 | if (written >= 0) |
91 | ret = -ENOMEM; | |
92 | goto err_fput; | |
93 | } | |
94 | ||
95 | /* Pin the mount and dentry to the key so that we can open it again | |
96 | * later | |
97 | */ | |
98 | *path = file->f_path; | |
99 | path_get(path); | |
100 | fput(file); | |
101 | } else { | |
102 | /* Just store the data in a buffer */ | |
103 | void *data = kmalloc(datalen, GFP_KERNEL); | |
002edaf7 DH |
104 | if (!data) |
105 | return -ENOMEM; | |
ab3c3587 | 106 | |
146aa8b1 DH |
107 | prep->payload.data[big_key_data] = data; |
108 | memcpy(data, prep->data, prep->datalen); | |
ab3c3587 DH |
109 | } |
110 | return 0; | |
111 | ||
112 | err_fput: | |
113 | fput(file); | |
ab3c3587 DH |
114 | error: |
115 | return ret; | |
116 | } | |
117 | ||
002edaf7 DH |
118 | /* |
119 | * Clear preparsement. | |
120 | */ | |
121 | void big_key_free_preparse(struct key_preparsed_payload *prep) | |
122 | { | |
123 | if (prep->datalen > BIG_KEY_FILE_THRESHOLD) { | |
146aa8b1 | 124 | struct path *path = (struct path *)&prep->payload.data[big_key_path]; |
002edaf7 DH |
125 | path_put(path); |
126 | } else { | |
146aa8b1 | 127 | kfree(prep->payload.data[big_key_data]); |
002edaf7 DH |
128 | } |
129 | } | |
130 | ||
ab3c3587 DH |
131 | /* |
132 | * dispose of the links from a revoked keyring | |
133 | * - called with the key sem write-locked | |
134 | */ | |
135 | void big_key_revoke(struct key *key) | |
136 | { | |
146aa8b1 | 137 | struct path *path = (struct path *)&key->payload.data[big_key_path]; |
ab3c3587 DH |
138 | |
139 | /* clear the quota */ | |
140 | key_payload_reserve(key, 0); | |
146aa8b1 DH |
141 | if (key_is_instantiated(key) && |
142 | (size_t)key->payload.data[big_key_len] > BIG_KEY_FILE_THRESHOLD) | |
ab3c3587 DH |
143 | vfs_truncate(path, 0); |
144 | } | |
145 | ||
146 | /* | |
147 | * dispose of the data dangling from the corpse of a big_key key | |
148 | */ | |
149 | void big_key_destroy(struct key *key) | |
150 | { | |
146aa8b1 DH |
151 | size_t datalen = (size_t)key->payload.data[big_key_len]; |
152 | ||
153 | if (datalen) { | |
154 | struct path *path = (struct path *)&key->payload.data[big_key_path]; | |
ab3c3587 DH |
155 | path_put(path); |
156 | path->mnt = NULL; | |
157 | path->dentry = NULL; | |
158 | } else { | |
146aa8b1 DH |
159 | kfree(key->payload.data[big_key_data]); |
160 | key->payload.data[big_key_data] = NULL; | |
ab3c3587 DH |
161 | } |
162 | } | |
163 | ||
164 | /* | |
165 | * describe the big_key key | |
166 | */ | |
167 | void big_key_describe(const struct key *key, struct seq_file *m) | |
168 | { | |
146aa8b1 | 169 | size_t datalen = (size_t)key->payload.data[big_key_len]; |
ab3c3587 DH |
170 | |
171 | seq_puts(m, key->description); | |
172 | ||
173 | if (key_is_instantiated(key)) | |
146aa8b1 | 174 | seq_printf(m, ": %zu [%s]", |
ab3c3587 DH |
175 | datalen, |
176 | datalen > BIG_KEY_FILE_THRESHOLD ? "file" : "buff"); | |
177 | } | |
178 | ||
179 | /* | |
180 | * read the key data | |
181 | * - the key's semaphore is read-locked | |
182 | */ | |
183 | long big_key_read(const struct key *key, char __user *buffer, size_t buflen) | |
184 | { | |
146aa8b1 | 185 | size_t datalen = (size_t)key->payload.data[big_key_len]; |
ab3c3587 DH |
186 | long ret; |
187 | ||
188 | if (!buffer || buflen < datalen) | |
189 | return datalen; | |
190 | ||
191 | if (datalen > BIG_KEY_FILE_THRESHOLD) { | |
146aa8b1 | 192 | struct path *path = (struct path *)&key->payload.data[big_key_path]; |
ab3c3587 DH |
193 | struct file *file; |
194 | loff_t pos; | |
195 | ||
196 | file = dentry_open(path, O_RDONLY, current_cred()); | |
197 | if (IS_ERR(file)) | |
198 | return PTR_ERR(file); | |
199 | ||
200 | pos = 0; | |
201 | ret = vfs_read(file, buffer, datalen, &pos); | |
202 | fput(file); | |
203 | if (ret >= 0 && ret != datalen) | |
204 | ret = -EIO; | |
205 | } else { | |
206 | ret = datalen; | |
146aa8b1 DH |
207 | if (copy_to_user(buffer, key->payload.data[big_key_data], |
208 | datalen) != 0) | |
ab3c3587 DH |
209 | ret = -EFAULT; |
210 | } | |
211 | ||
212 | return ret; | |
213 | } | |
214 | ||
215 | /* | |
216 | * Module stuff | |
217 | */ | |
218 | static int __init big_key_init(void) | |
219 | { | |
220 | return register_key_type(&key_type_big_key); | |
221 | } | |
222 | ||
223 | static void __exit big_key_cleanup(void) | |
224 | { | |
225 | unregister_key_type(&key_type_big_key); | |
226 | } | |
227 | ||
228 | module_init(big_key_init); | |
229 | module_exit(big_key_cleanup); |