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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", | |
36 | .def_lookup_type = KEYRING_SEARCH_LOOKUP_DIRECT, | |
37 | .instantiate = big_key_instantiate, | |
38 | .match = user_match, | |
39 | .revoke = big_key_revoke, | |
40 | .destroy = big_key_destroy, | |
41 | .describe = big_key_describe, | |
42 | .read = big_key_read, | |
43 | }; | |
44 | ||
45 | /* | |
46 | * Instantiate a big key | |
47 | */ | |
48 | int big_key_instantiate(struct key *key, struct key_preparsed_payload *prep) | |
49 | { | |
50 | struct path *path = (struct path *)&key->payload.data2; | |
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 */ | |
61 | ret = key_payload_reserve(key, 16); | |
62 | if (ret < 0) | |
63 | goto error; | |
64 | ||
65 | key->type_data.x[1] = datalen; | |
66 | ||
67 | if (datalen > BIG_KEY_FILE_THRESHOLD) { | |
68 | /* Create a shmem file to store the data in. This will permit the data | |
69 | * to be swapped out if needed. | |
70 | * | |
71 | * TODO: Encrypt the stored data with a temporary key. | |
72 | */ | |
73 | file = shmem_file_setup("", datalen, 0); | |
74 | if (IS_ERR(file)) | |
75 | goto err_quota; | |
76 | ||
77 | written = kernel_write(file, prep->data, prep->datalen, 0); | |
78 | if (written != datalen) { | |
79 | if (written >= 0) | |
80 | ret = -ENOMEM; | |
81 | goto err_fput; | |
82 | } | |
83 | ||
84 | /* Pin the mount and dentry to the key so that we can open it again | |
85 | * later | |
86 | */ | |
87 | *path = file->f_path; | |
88 | path_get(path); | |
89 | fput(file); | |
90 | } else { | |
91 | /* Just store the data in a buffer */ | |
92 | void *data = kmalloc(datalen, GFP_KERNEL); | |
93 | if (!data) { | |
94 | ret = -ENOMEM; | |
95 | goto err_quota; | |
96 | } | |
97 | ||
98 | key->payload.data = memcpy(data, prep->data, prep->datalen); | |
99 | } | |
100 | return 0; | |
101 | ||
102 | err_fput: | |
103 | fput(file); | |
104 | err_quota: | |
105 | key_payload_reserve(key, 0); | |
106 | error: | |
107 | return ret; | |
108 | } | |
109 | ||
110 | /* | |
111 | * dispose of the links from a revoked keyring | |
112 | * - called with the key sem write-locked | |
113 | */ | |
114 | void big_key_revoke(struct key *key) | |
115 | { | |
116 | struct path *path = (struct path *)&key->payload.data2; | |
117 | ||
118 | /* clear the quota */ | |
119 | key_payload_reserve(key, 0); | |
120 | if (key_is_instantiated(key) && key->type_data.x[1] > BIG_KEY_FILE_THRESHOLD) | |
121 | vfs_truncate(path, 0); | |
122 | } | |
123 | ||
124 | /* | |
125 | * dispose of the data dangling from the corpse of a big_key key | |
126 | */ | |
127 | void big_key_destroy(struct key *key) | |
128 | { | |
129 | if (key->type_data.x[1] > BIG_KEY_FILE_THRESHOLD) { | |
130 | struct path *path = (struct path *)&key->payload.data2; | |
131 | path_put(path); | |
132 | path->mnt = NULL; | |
133 | path->dentry = NULL; | |
134 | } else { | |
135 | kfree(key->payload.data); | |
136 | key->payload.data = NULL; | |
137 | } | |
138 | } | |
139 | ||
140 | /* | |
141 | * describe the big_key key | |
142 | */ | |
143 | void big_key_describe(const struct key *key, struct seq_file *m) | |
144 | { | |
145 | unsigned long datalen = key->type_data.x[1]; | |
146 | ||
147 | seq_puts(m, key->description); | |
148 | ||
149 | if (key_is_instantiated(key)) | |
150 | seq_printf(m, ": %lu [%s]", | |
151 | datalen, | |
152 | datalen > BIG_KEY_FILE_THRESHOLD ? "file" : "buff"); | |
153 | } | |
154 | ||
155 | /* | |
156 | * read the key data | |
157 | * - the key's semaphore is read-locked | |
158 | */ | |
159 | long big_key_read(const struct key *key, char __user *buffer, size_t buflen) | |
160 | { | |
161 | unsigned long datalen = key->type_data.x[1]; | |
162 | long ret; | |
163 | ||
164 | if (!buffer || buflen < datalen) | |
165 | return datalen; | |
166 | ||
167 | if (datalen > BIG_KEY_FILE_THRESHOLD) { | |
168 | struct path *path = (struct path *)&key->payload.data2; | |
169 | struct file *file; | |
170 | loff_t pos; | |
171 | ||
172 | file = dentry_open(path, O_RDONLY, current_cred()); | |
173 | if (IS_ERR(file)) | |
174 | return PTR_ERR(file); | |
175 | ||
176 | pos = 0; | |
177 | ret = vfs_read(file, buffer, datalen, &pos); | |
178 | fput(file); | |
179 | if (ret >= 0 && ret != datalen) | |
180 | ret = -EIO; | |
181 | } else { | |
182 | ret = datalen; | |
183 | if (copy_to_user(buffer, key->payload.data, datalen) != 0) | |
184 | ret = -EFAULT; | |
185 | } | |
186 | ||
187 | return ret; | |
188 | } | |
189 | ||
190 | /* | |
191 | * Module stuff | |
192 | */ | |
193 | static int __init big_key_init(void) | |
194 | { | |
195 | return register_key_type(&key_type_big_key); | |
196 | } | |
197 | ||
198 | static void __exit big_key_cleanup(void) | |
199 | { | |
200 | unregister_key_type(&key_type_big_key); | |
201 | } | |
202 | ||
203 | module_init(big_key_init); | |
204 | module_exit(big_key_cleanup); |