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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/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
20/*
21 * Layout of key payload words.
22 */
23enum {
24 big_key_data,
25 big_key_path,
26 big_key_path_2nd_part,
27 big_key_len,
28};
29
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 */
41struct key_type key_type_big_key = {
42 .name = "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,
49 .read = big_key_read,
50};
51
52/*
53 * Preparse a big key
54 */
55int big_key_preparse(struct key_preparsed_payload *prep)
56{
57 struct path *path = (struct path *)&prep->payload.data[big_key_path];
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 */
68 prep->quotalen = 16;
69
70 prep->payload.data[big_key_len] = (void *)(unsigned long)datalen;
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 */
78 file = shmem_kernel_file_setup("", datalen, 0);
79 if (IS_ERR(file)) {
80 ret = PTR_ERR(file);
81 goto error;
82 }
83
84 written = kernel_write(file, prep->data, prep->datalen, 0);
85 if (written != datalen) {
86 ret = written;
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);
101 if (!data)
102 return -ENOMEM;
103
104 prep->payload.data[big_key_data] = data;
105 memcpy(data, prep->data, prep->datalen);
106 }
107 return 0;
108
109err_fput:
110 fput(file);
111error:
112 return ret;
113}
114
115/*
116 * Clear preparsement.
117 */
118void big_key_free_preparse(struct key_preparsed_payload *prep)
119{
120 if (prep->datalen > BIG_KEY_FILE_THRESHOLD) {
121 struct path *path = (struct path *)&prep->payload.data[big_key_path];
122 path_put(path);
123 } else {
124 kfree(prep->payload.data[big_key_data]);
125 }
126}
127
128/*
129 * dispose of the links from a revoked keyring
130 * - called with the key sem write-locked
131 */
132void big_key_revoke(struct key *key)
133{
134 struct path *path = (struct path *)&key->payload.data[big_key_path];
135
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);
141}
142
143/*
144 * dispose of the data dangling from the corpse of a big_key key
145 */
146void big_key_destroy(struct key *key)
147{
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];
152 path_put(path);
153 path->mnt = NULL;
154 path->dentry = NULL;
155 } else {
156 kfree(key->payload.data[big_key_data]);
157 key->payload.data[big_key_data] = NULL;
158 }
159}
160
161/*
162 * describe the big_key key
163 */
164void big_key_describe(const struct key *key, struct seq_file *m)
165{
166 size_t datalen = (size_t)key->payload.data[big_key_len];
167
168 seq_puts(m, key->description);
169
170 if (key_is_instantiated(key))
171 seq_printf(m, ": %zu [%s]",
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 */
180long big_key_read(const struct key *key, char __user *buffer, size_t buflen)
181{
182 size_t datalen = (size_t)key->payload.data[big_key_len];
183 long ret;
184
185 if (!buffer || buflen < datalen)
186 return datalen;
187
188 if (datalen > BIG_KEY_FILE_THRESHOLD) {
189 struct path *path = (struct path *)&key->payload.data[big_key_path];
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;
204 if (copy_to_user(buffer, key->payload.data[big_key_data],
205 datalen) != 0)
206 ret = -EFAULT;
207 }
208
209 return ret;
210}
211
212static int __init big_key_init(void)
213{
214 return register_key_type(&key_type_big_key);
215}
216device_initcall(big_key_init);
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
21MODULE_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 */
34struct 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 */
48int 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_kernel_file_setup("", datalen, 0);
74 if (IS_ERR(file)) {
75 ret = PTR_ERR(file);
76 goto err_quota;
77 }
78
79 written = kernel_write(file, prep->data, prep->datalen, 0);
80 if (written != datalen) {
81 ret = written;
82 if (written >= 0)
83 ret = -ENOMEM;
84 goto err_fput;
85 }
86
87 /* Pin the mount and dentry to the key so that we can open it again
88 * later
89 */
90 *path = file->f_path;
91 path_get(path);
92 fput(file);
93 } else {
94 /* Just store the data in a buffer */
95 void *data = kmalloc(datalen, GFP_KERNEL);
96 if (!data) {
97 ret = -ENOMEM;
98 goto err_quota;
99 }
100
101 key->payload.data = memcpy(data, prep->data, prep->datalen);
102 }
103 return 0;
104
105err_fput:
106 fput(file);
107err_quota:
108 key_payload_reserve(key, 0);
109error:
110 return ret;
111}
112
113/*
114 * dispose of the links from a revoked keyring
115 * - called with the key sem write-locked
116 */
117void big_key_revoke(struct key *key)
118{
119 struct path *path = (struct path *)&key->payload.data2;
120
121 /* clear the quota */
122 key_payload_reserve(key, 0);
123 if (key_is_instantiated(key) && key->type_data.x[1] > BIG_KEY_FILE_THRESHOLD)
124 vfs_truncate(path, 0);
125}
126
127/*
128 * dispose of the data dangling from the corpse of a big_key key
129 */
130void big_key_destroy(struct key *key)
131{
132 if (key->type_data.x[1] > BIG_KEY_FILE_THRESHOLD) {
133 struct path *path = (struct path *)&key->payload.data2;
134 path_put(path);
135 path->mnt = NULL;
136 path->dentry = NULL;
137 } else {
138 kfree(key->payload.data);
139 key->payload.data = NULL;
140 }
141}
142
143/*
144 * describe the big_key key
145 */
146void big_key_describe(const struct key *key, struct seq_file *m)
147{
148 unsigned long datalen = key->type_data.x[1];
149
150 seq_puts(m, key->description);
151
152 if (key_is_instantiated(key))
153 seq_printf(m, ": %lu [%s]",
154 datalen,
155 datalen > BIG_KEY_FILE_THRESHOLD ? "file" : "buff");
156}
157
158/*
159 * read the key data
160 * - the key's semaphore is read-locked
161 */
162long big_key_read(const struct key *key, char __user *buffer, size_t buflen)
163{
164 unsigned long datalen = key->type_data.x[1];
165 long ret;
166
167 if (!buffer || buflen < datalen)
168 return datalen;
169
170 if (datalen > BIG_KEY_FILE_THRESHOLD) {
171 struct path *path = (struct path *)&key->payload.data2;
172 struct file *file;
173 loff_t pos;
174
175 file = dentry_open(path, O_RDONLY, current_cred());
176 if (IS_ERR(file))
177 return PTR_ERR(file);
178
179 pos = 0;
180 ret = vfs_read(file, buffer, datalen, &pos);
181 fput(file);
182 if (ret >= 0 && ret != datalen)
183 ret = -EIO;
184 } else {
185 ret = datalen;
186 if (copy_to_user(buffer, key->payload.data, datalen) != 0)
187 ret = -EFAULT;
188 }
189
190 return ret;
191}
192
193/*
194 * Module stuff
195 */
196static int __init big_key_init(void)
197{
198 return register_key_type(&key_type_big_key);
199}
200
201static void __exit big_key_cleanup(void)
202{
203 unregister_key_type(&key_type_big_key);
204}
205
206module_init(big_key_init);
207module_exit(big_key_cleanup);