1 /* Large capacity key type
3 * Copyright (C) 2013 Red Hat, Inc. All Rights Reserved.
4 * Written by David Howells (dhowells@redhat.com)
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.
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>
21 * Layout of key payload words.
26 big_key_path_2nd_part,
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.
35 #define BIG_KEY_FILE_THRESHOLD (sizeof(struct inode) + sizeof(struct dentry))
38 * big_key defined keys take an arbitrary string as the description and an
39 * arbitrary blob of data as the payload
41 struct key_type key_type_big_key = {
43 .preparse = big_key_preparse,
44 .free_preparse = big_key_free_preparse,
45 .instantiate = generic_key_instantiate,
46 .revoke = big_key_revoke,
47 .destroy = big_key_destroy,
48 .describe = big_key_describe,
55 int big_key_preparse(struct key_preparsed_payload *prep)
57 struct path *path = (struct path *)&prep->payload.data[big_key_path];
60 size_t datalen = prep->datalen;
64 if (datalen <= 0 || datalen > 1024 * 1024 || !prep->data)
67 /* Set an arbitrary quota */
70 prep->payload.data[big_key_len] = (void *)(unsigned long)datalen;
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.
76 * TODO: Encrypt the stored data with a temporary key.
78 file = shmem_kernel_file_setup("", datalen, 0);
84 written = kernel_write(file, prep->data, prep->datalen, 0);
85 if (written != datalen) {
92 /* Pin the mount and dentry to the key so that we can open it again
99 /* Just store the data in a buffer */
100 void *data = kmalloc(datalen, GFP_KERNEL);
104 prep->payload.data[big_key_data] = data;
105 memcpy(data, prep->data, prep->datalen);
116 * Clear preparsement.
118 void big_key_free_preparse(struct key_preparsed_payload *prep)
120 if (prep->datalen > BIG_KEY_FILE_THRESHOLD) {
121 struct path *path = (struct path *)&prep->payload.data[big_key_path];
124 kfree(prep->payload.data[big_key_data]);
129 * dispose of the links from a revoked keyring
130 * - called with the key sem write-locked
132 void big_key_revoke(struct key *key)
134 struct path *path = (struct path *)&key->payload.data[big_key_path];
136 /* clear the quota */
137 key_payload_reserve(key, 0);
138 if (key_is_instantiated(key) &&
139 (size_t)key->payload.data[big_key_len] > BIG_KEY_FILE_THRESHOLD)
140 vfs_truncate(path, 0);
144 * dispose of the data dangling from the corpse of a big_key key
146 void big_key_destroy(struct key *key)
148 size_t datalen = (size_t)key->payload.data[big_key_len];
151 struct path *path = (struct path *)&key->payload.data[big_key_path];
156 kfree(key->payload.data[big_key_data]);
157 key->payload.data[big_key_data] = NULL;
162 * describe the big_key key
164 void big_key_describe(const struct key *key, struct seq_file *m)
166 size_t datalen = (size_t)key->payload.data[big_key_len];
168 seq_puts(m, key->description);
170 if (key_is_instantiated(key))
171 seq_printf(m, ": %zu [%s]",
173 datalen > BIG_KEY_FILE_THRESHOLD ? "file" : "buff");
178 * - the key's semaphore is read-locked
180 long big_key_read(const struct key *key, char __user *buffer, size_t buflen)
182 size_t datalen = (size_t)key->payload.data[big_key_len];
185 if (!buffer || buflen < datalen)
188 if (datalen > BIG_KEY_FILE_THRESHOLD) {
189 struct path *path = (struct path *)&key->payload.data[big_key_path];
193 file = dentry_open(path, O_RDONLY, current_cred());
195 return PTR_ERR(file);
198 ret = vfs_read(file, buffer, datalen, &pos);
200 if (ret >= 0 && ret != datalen)
204 if (copy_to_user(buffer, key->payload.data[big_key_data],
212 static int __init big_key_init(void)
214 return register_key_type(&key_type_big_key);
216 device_initcall(big_key_init);