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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 | ||
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 | */ | |
34 | struct key_type key_type_big_key = { | |
35 | .name = "big_key", | |
002edaf7 DH |
36 | .preparse = big_key_preparse, |
37 | .free_preparse = big_key_free_preparse, | |
38 | .instantiate = generic_key_instantiate, | |
ab3c3587 DH |
39 | .revoke = big_key_revoke, |
40 | .destroy = big_key_destroy, | |
41 | .describe = big_key_describe, | |
42 | .read = big_key_read, | |
43 | }; | |
44 | ||
45 | /* | |
002edaf7 | 46 | * Preparse a big key |
ab3c3587 | 47 | */ |
002edaf7 | 48 | int big_key_preparse(struct key_preparsed_payload *prep) |
ab3c3587 | 49 | { |
002edaf7 | 50 | struct path *path = (struct path *)&prep->payload; |
ab3c3587 DH |
51 | 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 */ | |
002edaf7 | 61 | prep->quotalen = 16; |
ab3c3587 | 62 | |
002edaf7 | 63 | prep->type_data[1] = (void *)(unsigned long)datalen; |
ab3c3587 DH |
64 | |
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 | */ | |
c7277090 | 71 | file = shmem_kernel_file_setup("", datalen, 0); |
d2b86970 WY |
72 | if (IS_ERR(file)) { |
73 | ret = PTR_ERR(file); | |
002edaf7 | 74 | goto error; |
d2b86970 | 75 | } |
ab3c3587 DH |
76 | |
77 | written = kernel_write(file, prep->data, prep->datalen, 0); | |
78 | if (written != datalen) { | |
97826c82 | 79 | ret = written; |
ab3c3587 DH |
80 | 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); | |
002edaf7 DH |
94 | if (!data) |
95 | return -ENOMEM; | |
ab3c3587 | 96 | |
002edaf7 | 97 | prep->payload[0] = memcpy(data, prep->data, prep->datalen); |
ab3c3587 DH |
98 | } |
99 | return 0; | |
100 | ||
101 | err_fput: | |
102 | fput(file); | |
ab3c3587 DH |
103 | error: |
104 | return ret; | |
105 | } | |
106 | ||
002edaf7 DH |
107 | /* |
108 | * Clear preparsement. | |
109 | */ | |
110 | void 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 | ||
ab3c3587 DH |
120 | /* |
121 | * dispose of the links from a revoked keyring | |
122 | * - called with the key sem write-locked | |
123 | */ | |
124 | void 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 | */ | |
137 | void 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 | */ | |
153 | void 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 | */ | |
169 | long 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 | */ | |
203 | static int __init big_key_init(void) | |
204 | { | |
205 | return register_key_type(&key_type_big_key); | |
206 | } | |
207 | ||
208 | static void __exit big_key_cleanup(void) | |
209 | { | |
210 | unregister_key_type(&key_type_big_key); | |
211 | } | |
212 | ||
213 | module_init(big_key_init); | |
214 | module_exit(big_key_cleanup); |