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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 | ||
ab3c3587 DH |
12 | #include <linux/init.h> |
13 | #include <linux/seq_file.h> | |
14 | #include <linux/file.h> | |
15 | #include <linux/shmem_fs.h> | |
16 | #include <linux/err.h> | |
17 | #include <keys/user-type.h> | |
18 | #include <keys/big_key-type.h> | |
19 | ||
146aa8b1 DH |
20 | /* |
21 | * Layout of key payload words. | |
22 | */ | |
23 | enum { | |
24 | big_key_data, | |
25 | big_key_path, | |
26 | big_key_path_2nd_part, | |
27 | big_key_len, | |
28 | }; | |
29 | ||
ab3c3587 DH |
30 | /* |
31 | * If the data is under this limit, there's no point creating a shm file to | |
32 | * hold it as the permanently resident metadata for the shmem fs will be at | |
33 | * least as large as the data. | |
34 | */ | |
35 | #define BIG_KEY_FILE_THRESHOLD (sizeof(struct inode) + sizeof(struct dentry)) | |
36 | ||
37 | /* | |
38 | * big_key defined keys take an arbitrary string as the description and an | |
39 | * arbitrary blob of data as the payload | |
40 | */ | |
41 | struct key_type key_type_big_key = { | |
42 | .name = "big_key", | |
002edaf7 DH |
43 | .preparse = big_key_preparse, |
44 | .free_preparse = big_key_free_preparse, | |
45 | .instantiate = generic_key_instantiate, | |
ab3c3587 DH |
46 | .revoke = big_key_revoke, |
47 | .destroy = big_key_destroy, | |
48 | .describe = big_key_describe, | |
49 | .read = big_key_read, | |
50 | }; | |
51 | ||
52 | /* | |
002edaf7 | 53 | * Preparse a big key |
ab3c3587 | 54 | */ |
002edaf7 | 55 | int big_key_preparse(struct key_preparsed_payload *prep) |
ab3c3587 | 56 | { |
146aa8b1 | 57 | struct path *path = (struct path *)&prep->payload.data[big_key_path]; |
ab3c3587 DH |
58 | struct file *file; |
59 | ssize_t written; | |
60 | size_t datalen = prep->datalen; | |
61 | int ret; | |
62 | ||
63 | ret = -EINVAL; | |
64 | if (datalen <= 0 || datalen > 1024 * 1024 || !prep->data) | |
65 | goto error; | |
66 | ||
67 | /* Set an arbitrary quota */ | |
002edaf7 | 68 | prep->quotalen = 16; |
ab3c3587 | 69 | |
146aa8b1 | 70 | prep->payload.data[big_key_len] = (void *)(unsigned long)datalen; |
ab3c3587 DH |
71 | |
72 | if (datalen > BIG_KEY_FILE_THRESHOLD) { | |
73 | /* Create a shmem file to store the data in. This will permit the data | |
74 | * to be swapped out if needed. | |
75 | * | |
76 | * TODO: Encrypt the stored data with a temporary key. | |
77 | */ | |
c7277090 | 78 | file = shmem_kernel_file_setup("", datalen, 0); |
d2b86970 WY |
79 | if (IS_ERR(file)) { |
80 | ret = PTR_ERR(file); | |
002edaf7 | 81 | goto error; |
d2b86970 | 82 | } |
ab3c3587 DH |
83 | |
84 | written = kernel_write(file, prep->data, prep->datalen, 0); | |
85 | if (written != datalen) { | |
97826c82 | 86 | ret = written; |
ab3c3587 DH |
87 | if (written >= 0) |
88 | ret = -ENOMEM; | |
89 | goto err_fput; | |
90 | } | |
91 | ||
92 | /* Pin the mount and dentry to the key so that we can open it again | |
93 | * later | |
94 | */ | |
95 | *path = file->f_path; | |
96 | path_get(path); | |
97 | fput(file); | |
98 | } else { | |
99 | /* Just store the data in a buffer */ | |
100 | void *data = kmalloc(datalen, GFP_KERNEL); | |
002edaf7 DH |
101 | if (!data) |
102 | return -ENOMEM; | |
ab3c3587 | 103 | |
146aa8b1 DH |
104 | prep->payload.data[big_key_data] = data; |
105 | memcpy(data, prep->data, prep->datalen); | |
ab3c3587 DH |
106 | } |
107 | return 0; | |
108 | ||
109 | err_fput: | |
110 | fput(file); | |
ab3c3587 DH |
111 | error: |
112 | return ret; | |
113 | } | |
114 | ||
002edaf7 DH |
115 | /* |
116 | * Clear preparsement. | |
117 | */ | |
118 | void big_key_free_preparse(struct key_preparsed_payload *prep) | |
119 | { | |
120 | if (prep->datalen > BIG_KEY_FILE_THRESHOLD) { | |
146aa8b1 | 121 | struct path *path = (struct path *)&prep->payload.data[big_key_path]; |
002edaf7 DH |
122 | path_put(path); |
123 | } else { | |
146aa8b1 | 124 | kfree(prep->payload.data[big_key_data]); |
002edaf7 DH |
125 | } |
126 | } | |
127 | ||
ab3c3587 DH |
128 | /* |
129 | * dispose of the links from a revoked keyring | |
130 | * - called with the key sem write-locked | |
131 | */ | |
132 | void big_key_revoke(struct key *key) | |
133 | { | |
146aa8b1 | 134 | struct path *path = (struct path *)&key->payload.data[big_key_path]; |
ab3c3587 DH |
135 | |
136 | /* clear the quota */ | |
137 | key_payload_reserve(key, 0); | |
146aa8b1 DH |
138 | if (key_is_instantiated(key) && |
139 | (size_t)key->payload.data[big_key_len] > BIG_KEY_FILE_THRESHOLD) | |
ab3c3587 DH |
140 | vfs_truncate(path, 0); |
141 | } | |
142 | ||
143 | /* | |
144 | * dispose of the data dangling from the corpse of a big_key key | |
145 | */ | |
146 | void big_key_destroy(struct key *key) | |
147 | { | |
146aa8b1 DH |
148 | size_t datalen = (size_t)key->payload.data[big_key_len]; |
149 | ||
150 | if (datalen) { | |
151 | struct path *path = (struct path *)&key->payload.data[big_key_path]; | |
ab3c3587 DH |
152 | path_put(path); |
153 | path->mnt = NULL; | |
154 | path->dentry = NULL; | |
155 | } else { | |
146aa8b1 DH |
156 | kfree(key->payload.data[big_key_data]); |
157 | key->payload.data[big_key_data] = NULL; | |
ab3c3587 DH |
158 | } |
159 | } | |
160 | ||
161 | /* | |
162 | * describe the big_key key | |
163 | */ | |
164 | void big_key_describe(const struct key *key, struct seq_file *m) | |
165 | { | |
146aa8b1 | 166 | size_t datalen = (size_t)key->payload.data[big_key_len]; |
ab3c3587 DH |
167 | |
168 | seq_puts(m, key->description); | |
169 | ||
170 | if (key_is_instantiated(key)) | |
146aa8b1 | 171 | seq_printf(m, ": %zu [%s]", |
ab3c3587 DH |
172 | datalen, |
173 | datalen > BIG_KEY_FILE_THRESHOLD ? "file" : "buff"); | |
174 | } | |
175 | ||
176 | /* | |
177 | * read the key data | |
178 | * - the key's semaphore is read-locked | |
179 | */ | |
180 | long big_key_read(const struct key *key, char __user *buffer, size_t buflen) | |
181 | { | |
146aa8b1 | 182 | size_t datalen = (size_t)key->payload.data[big_key_len]; |
ab3c3587 DH |
183 | long ret; |
184 | ||
185 | if (!buffer || buflen < datalen) | |
186 | return datalen; | |
187 | ||
188 | if (datalen > BIG_KEY_FILE_THRESHOLD) { | |
146aa8b1 | 189 | struct path *path = (struct path *)&key->payload.data[big_key_path]; |
ab3c3587 DH |
190 | struct file *file; |
191 | loff_t pos; | |
192 | ||
193 | file = dentry_open(path, O_RDONLY, current_cred()); | |
194 | if (IS_ERR(file)) | |
195 | return PTR_ERR(file); | |
196 | ||
197 | pos = 0; | |
198 | ret = vfs_read(file, buffer, datalen, &pos); | |
199 | fput(file); | |
200 | if (ret >= 0 && ret != datalen) | |
201 | ret = -EIO; | |
202 | } else { | |
203 | ret = datalen; | |
146aa8b1 DH |
204 | if (copy_to_user(buffer, key->payload.data[big_key_data], |
205 | datalen) != 0) | |
ab3c3587 DH |
206 | ret = -EFAULT; |
207 | } | |
208 | ||
209 | return ret; | |
210 | } | |
211 | ||
ab3c3587 DH |
212 | static int __init big_key_init(void) |
213 | { | |
214 | return register_key_type(&key_type_big_key); | |
215 | } | |
a1f2bdf3 | 216 | device_initcall(big_key_init); |