blob: 577dfaf0367f66e137442b3932210d806d832da3 [file] [log] [blame]
Greg Kroah-Hartmanb2441312017-11-01 15:07:57 +01001// SPDX-License-Identifier: GPL-2.0
Jaegeuk Kim0b81d072015-05-15 16:26:10 -07002/*
3 * key management facility for FS encryption support.
4 *
5 * Copyright (C) 2015, Google, Inc.
6 *
7 * This contains encryption key functions.
8 *
9 * Written by Michael Halcrow, Ildar Muslukhov, and Uday Savagaonkar, 2015.
10 */
11
Jaegeuk Kim0b81d072015-05-15 16:26:10 -070012#include <keys/user-type.h>
Jaegeuk Kim0b81d072015-05-15 16:26:10 -070013#include <linux/scatterlist.h>
Daniel Walterb7e7cf72017-06-19 09:27:58 +020014#include <linux/ratelimit.h>
15#include <crypto/aes.h>
16#include <crypto/sha.h>
Theodore Ts'o3325bea2016-11-26 20:32:46 -050017#include "fscrypt_private.h"
Jaegeuk Kim0b81d072015-05-15 16:26:10 -070018
Daniel Walterb7e7cf72017-06-19 09:27:58 +020019static struct crypto_shash *essiv_hash_tfm;
20
Jaegeuk Kim0b81d072015-05-15 16:26:10 -070021static void derive_crypt_complete(struct crypto_async_request *req, int rc)
22{
23 struct fscrypt_completion_result *ecr = req->data;
24
25 if (rc == -EINPROGRESS)
26 return;
27
28 ecr->res = rc;
29 complete(&ecr->completion);
30}
31
32/**
33 * derive_key_aes() - Derive a key using AES-128-ECB
34 * @deriving_key: Encryption key used for derivation.
35 * @source_key: Source key to which to apply derivation.
Daniel Walterb7e7cf72017-06-19 09:27:58 +020036 * @derived_raw_key: Derived raw key.
Jaegeuk Kim0b81d072015-05-15 16:26:10 -070037 *
38 * Return: Zero on success; non-zero otherwise.
39 */
40static int derive_key_aes(u8 deriving_key[FS_AES_128_ECB_KEY_SIZE],
Daniel Walterb7e7cf72017-06-19 09:27:58 +020041 const struct fscrypt_key *source_key,
42 u8 derived_raw_key[FS_MAX_KEY_SIZE])
Jaegeuk Kim0b81d072015-05-15 16:26:10 -070043{
44 int res = 0;
Linus Torvaldsd4075742016-03-21 11:03:02 -070045 struct skcipher_request *req = NULL;
Jaegeuk Kim0b81d072015-05-15 16:26:10 -070046 DECLARE_FS_COMPLETION_RESULT(ecr);
47 struct scatterlist src_sg, dst_sg;
Linus Torvaldsd4075742016-03-21 11:03:02 -070048 struct crypto_skcipher *tfm = crypto_alloc_skcipher("ecb(aes)", 0, 0);
Jaegeuk Kim0b81d072015-05-15 16:26:10 -070049
50 if (IS_ERR(tfm)) {
51 res = PTR_ERR(tfm);
52 tfm = NULL;
53 goto out;
54 }
Linus Torvaldsd4075742016-03-21 11:03:02 -070055 crypto_skcipher_set_flags(tfm, CRYPTO_TFM_REQ_WEAK_KEY);
56 req = skcipher_request_alloc(tfm, GFP_NOFS);
Jaegeuk Kim0b81d072015-05-15 16:26:10 -070057 if (!req) {
58 res = -ENOMEM;
59 goto out;
60 }
Linus Torvaldsd4075742016-03-21 11:03:02 -070061 skcipher_request_set_callback(req,
Jaegeuk Kim0b81d072015-05-15 16:26:10 -070062 CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
63 derive_crypt_complete, &ecr);
Linus Torvaldsd4075742016-03-21 11:03:02 -070064 res = crypto_skcipher_setkey(tfm, deriving_key,
Jaegeuk Kim0b81d072015-05-15 16:26:10 -070065 FS_AES_128_ECB_KEY_SIZE);
66 if (res < 0)
67 goto out;
68
Daniel Walterb7e7cf72017-06-19 09:27:58 +020069 sg_init_one(&src_sg, source_key->raw, source_key->size);
70 sg_init_one(&dst_sg, derived_raw_key, source_key->size);
71 skcipher_request_set_crypt(req, &src_sg, &dst_sg, source_key->size,
72 NULL);
Linus Torvaldsd4075742016-03-21 11:03:02 -070073 res = crypto_skcipher_encrypt(req);
Jaegeuk Kim0b81d072015-05-15 16:26:10 -070074 if (res == -EINPROGRESS || res == -EBUSY) {
75 wait_for_completion(&ecr.completion);
76 res = ecr.res;
77 }
78out:
Linus Torvaldsd4075742016-03-21 11:03:02 -070079 skcipher_request_free(req);
80 crypto_free_skcipher(tfm);
Jaegeuk Kim0b81d072015-05-15 16:26:10 -070081 return res;
82}
83
Jaegeuk Kimb5a7aef2016-05-04 22:05:01 -070084static int validate_user_key(struct fscrypt_info *crypt_info,
85 struct fscrypt_context *ctx, u8 *raw_key,
Daniel Walterb7e7cf72017-06-19 09:27:58 +020086 const char *prefix, int min_keysize)
Jaegeuk Kimb5a7aef2016-05-04 22:05:01 -070087{
Eric Biggersa5d431e2017-01-05 13:51:18 -080088 char *description;
Jaegeuk Kimb5a7aef2016-05-04 22:05:01 -070089 struct key *keyring_key;
90 struct fscrypt_key *master_key;
91 const struct user_key_payload *ukp;
Jaegeuk Kimb5a7aef2016-05-04 22:05:01 -070092 int res;
93
Eric Biggersa5d431e2017-01-05 13:51:18 -080094 description = kasprintf(GFP_NOFS, "%s%*phN", prefix,
95 FS_KEY_DESCRIPTOR_SIZE,
96 ctx->master_key_descriptor);
97 if (!description)
Jaegeuk Kimb5a7aef2016-05-04 22:05:01 -070098 return -ENOMEM;
99
Eric Biggersa5d431e2017-01-05 13:51:18 -0800100 keyring_key = request_key(&key_type_logon, description, NULL);
101 kfree(description);
Jaegeuk Kimb5a7aef2016-05-04 22:05:01 -0700102 if (IS_ERR(keyring_key))
103 return PTR_ERR(keyring_key);
Eric Biggers1b53cf92017-02-21 15:07:11 -0800104 down_read(&keyring_key->sem);
Jaegeuk Kimb5a7aef2016-05-04 22:05:01 -0700105
106 if (keyring_key->type != &key_type_logon) {
107 printk_once(KERN_WARNING
108 "%s: key type must be logon\n", __func__);
109 res = -ENOKEY;
110 goto out;
111 }
David Howells0837e492017-03-01 15:11:23 +0000112 ukp = user_key_payload_locked(keyring_key);
Eric Biggersd60b5b72017-10-09 12:46:18 -0700113 if (!ukp) {
114 /* key was revoked before we acquired its semaphore */
115 res = -EKEYREVOKED;
116 goto out;
117 }
Jaegeuk Kimb5a7aef2016-05-04 22:05:01 -0700118 if (ukp->datalen != sizeof(struct fscrypt_key)) {
119 res = -EINVAL;
Jaegeuk Kimb5a7aef2016-05-04 22:05:01 -0700120 goto out;
121 }
122 master_key = (struct fscrypt_key *)ukp->data;
123 BUILD_BUG_ON(FS_AES_128_ECB_KEY_SIZE != FS_KEY_DERIVATION_NONCE_SIZE);
124
Daniel Walterb7e7cf72017-06-19 09:27:58 +0200125 if (master_key->size < min_keysize || master_key->size > FS_MAX_KEY_SIZE
126 || master_key->size % AES_BLOCK_SIZE != 0) {
Jaegeuk Kimb5a7aef2016-05-04 22:05:01 -0700127 printk_once(KERN_WARNING
128 "%s: key size incorrect: %d\n",
129 __func__, master_key->size);
130 res = -ENOKEY;
Jaegeuk Kimb5a7aef2016-05-04 22:05:01 -0700131 goto out;
132 }
Daniel Walterb7e7cf72017-06-19 09:27:58 +0200133 res = derive_key_aes(ctx->nonce, master_key, raw_key);
Jaegeuk Kimb5a7aef2016-05-04 22:05:01 -0700134out:
Eric Biggers1b53cf92017-02-21 15:07:11 -0800135 up_read(&keyring_key->sem);
Jaegeuk Kimb5a7aef2016-05-04 22:05:01 -0700136 key_put(keyring_key);
137 return res;
138}
139
Daniel Walterb7e7cf72017-06-19 09:27:58 +0200140static const struct {
141 const char *cipher_str;
142 int keysize;
143} available_modes[] = {
144 [FS_ENCRYPTION_MODE_AES_256_XTS] = { "xts(aes)",
145 FS_AES_256_XTS_KEY_SIZE },
146 [FS_ENCRYPTION_MODE_AES_256_CTS] = { "cts(cbc(aes))",
147 FS_AES_256_CTS_KEY_SIZE },
148 [FS_ENCRYPTION_MODE_AES_128_CBC] = { "cbc(aes)",
149 FS_AES_128_CBC_KEY_SIZE },
150 [FS_ENCRYPTION_MODE_AES_128_CTS] = { "cts(cbc(aes))",
151 FS_AES_128_CTS_KEY_SIZE },
152};
153
Eric Biggers8f398502016-09-15 13:32:11 -0400154static int determine_cipher_type(struct fscrypt_info *ci, struct inode *inode,
155 const char **cipher_str_ret, int *keysize_ret)
156{
Daniel Walterb7e7cf72017-06-19 09:27:58 +0200157 u32 mode;
158
159 if (!fscrypt_valid_enc_modes(ci->ci_data_mode, ci->ci_filename_mode)) {
160 pr_warn_ratelimited("fscrypt: inode %lu uses unsupported encryption modes (contents mode %d, filenames mode %d)\n",
161 inode->i_ino,
162 ci->ci_data_mode, ci->ci_filename_mode);
163 return -EINVAL;
164 }
165
Eric Biggers8f398502016-09-15 13:32:11 -0400166 if (S_ISREG(inode->i_mode)) {
Daniel Walterb7e7cf72017-06-19 09:27:58 +0200167 mode = ci->ci_data_mode;
168 } else if (S_ISDIR(inode->i_mode) || S_ISLNK(inode->i_mode)) {
169 mode = ci->ci_filename_mode;
170 } else {
171 WARN_ONCE(1, "fscrypt: filesystem tried to load encryption info for inode %lu, which is not encryptable (file type %d)\n",
172 inode->i_ino, (inode->i_mode & S_IFMT));
173 return -EINVAL;
Eric Biggers8f398502016-09-15 13:32:11 -0400174 }
175
Daniel Walterb7e7cf72017-06-19 09:27:58 +0200176 *cipher_str_ret = available_modes[mode].cipher_str;
177 *keysize_ret = available_modes[mode].keysize;
178 return 0;
Eric Biggers8f398502016-09-15 13:32:11 -0400179}
180
Jaegeuk Kim0b81d072015-05-15 16:26:10 -0700181static void put_crypt_info(struct fscrypt_info *ci)
182{
183 if (!ci)
184 return;
185
Linus Torvaldsd4075742016-03-21 11:03:02 -0700186 crypto_free_skcipher(ci->ci_ctfm);
Daniel Walterb7e7cf72017-06-19 09:27:58 +0200187 crypto_free_cipher(ci->ci_essiv_tfm);
Jaegeuk Kim0b81d072015-05-15 16:26:10 -0700188 kmem_cache_free(fscrypt_info_cachep, ci);
189}
190
Daniel Walterb7e7cf72017-06-19 09:27:58 +0200191static int derive_essiv_salt(const u8 *key, int keysize, u8 *salt)
192{
193 struct crypto_shash *tfm = READ_ONCE(essiv_hash_tfm);
194
195 /* init hash transform on demand */
196 if (unlikely(!tfm)) {
197 struct crypto_shash *prev_tfm;
198
199 tfm = crypto_alloc_shash("sha256", 0, 0);
200 if (IS_ERR(tfm)) {
201 pr_warn_ratelimited("fscrypt: error allocating SHA-256 transform: %ld\n",
202 PTR_ERR(tfm));
203 return PTR_ERR(tfm);
204 }
205 prev_tfm = cmpxchg(&essiv_hash_tfm, NULL, tfm);
206 if (prev_tfm) {
207 crypto_free_shash(tfm);
208 tfm = prev_tfm;
209 }
210 }
211
212 {
213 SHASH_DESC_ON_STACK(desc, tfm);
214 desc->tfm = tfm;
215 desc->flags = 0;
216
217 return crypto_shash_digest(desc, key, keysize, salt);
218 }
219}
220
221static int init_essiv_generator(struct fscrypt_info *ci, const u8 *raw_key,
222 int keysize)
223{
224 int err;
225 struct crypto_cipher *essiv_tfm;
226 u8 salt[SHA256_DIGEST_SIZE];
227
228 essiv_tfm = crypto_alloc_cipher("aes", 0, 0);
229 if (IS_ERR(essiv_tfm))
230 return PTR_ERR(essiv_tfm);
231
232 ci->ci_essiv_tfm = essiv_tfm;
233
234 err = derive_essiv_salt(raw_key, keysize, salt);
235 if (err)
236 goto out;
237
238 /*
239 * Using SHA256 to derive the salt/key will result in AES-256 being
240 * used for IV generation. File contents encryption will still use the
241 * configured keysize (AES-128) nevertheless.
242 */
243 err = crypto_cipher_setkey(essiv_tfm, salt, sizeof(salt));
244 if (err)
245 goto out;
246
247out:
248 memzero_explicit(salt, sizeof(salt));
249 return err;
250}
251
252void __exit fscrypt_essiv_cleanup(void)
253{
254 crypto_free_shash(essiv_hash_tfm);
255}
256
Eric Biggers1b53cf92017-02-21 15:07:11 -0800257int fscrypt_get_encryption_info(struct inode *inode)
Jaegeuk Kim0b81d072015-05-15 16:26:10 -0700258{
259 struct fscrypt_info *crypt_info;
Jaegeuk Kim0b81d072015-05-15 16:26:10 -0700260 struct fscrypt_context ctx;
Linus Torvaldsd4075742016-03-21 11:03:02 -0700261 struct crypto_skcipher *ctfm;
Jaegeuk Kim0b81d072015-05-15 16:26:10 -0700262 const char *cipher_str;
Eric Biggers8f398502016-09-15 13:32:11 -0400263 int keysize;
Eric Biggersa6e08912016-11-13 20:41:09 -0500264 u8 *raw_key = NULL;
Jaegeuk Kim0b81d072015-05-15 16:26:10 -0700265 int res;
266
Eric Biggers1b53cf92017-02-21 15:07:11 -0800267 if (inode->i_crypt_info)
268 return 0;
269
David Gstirf32d7ac2016-12-06 23:53:57 +0100270 res = fscrypt_initialize(inode->i_sb->s_cop->flags);
Jaegeuk Kim0b81d072015-05-15 16:26:10 -0700271 if (res)
272 return res;
273
Jaegeuk Kim0b81d072015-05-15 16:26:10 -0700274 res = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx));
275 if (res < 0) {
Theodore Ts'o5bbdcbb2017-01-02 15:12:17 -0500276 if (!fscrypt_dummy_context_enabled(inode) ||
277 inode->i_sb->s_cop->is_encrypted(inode))
Jaegeuk Kim0b81d072015-05-15 16:26:10 -0700278 return res;
Theodore Ts'o5bbdcbb2017-01-02 15:12:17 -0500279 /* Fake up a context for an unencrypted directory */
280 memset(&ctx, 0, sizeof(ctx));
Eric Biggers8f398502016-09-15 13:32:11 -0400281 ctx.format = FS_ENCRYPTION_CONTEXT_FORMAT_V1;
Jaegeuk Kim0b81d072015-05-15 16:26:10 -0700282 ctx.contents_encryption_mode = FS_ENCRYPTION_MODE_AES_256_XTS;
283 ctx.filenames_encryption_mode = FS_ENCRYPTION_MODE_AES_256_CTS;
Theodore Ts'o5bbdcbb2017-01-02 15:12:17 -0500284 memset(ctx.master_key_descriptor, 0x42, FS_KEY_DESCRIPTOR_SIZE);
Jaegeuk Kim0b81d072015-05-15 16:26:10 -0700285 } else if (res != sizeof(ctx)) {
286 return -EINVAL;
287 }
Eric Biggers8f398502016-09-15 13:32:11 -0400288
289 if (ctx.format != FS_ENCRYPTION_CONTEXT_FORMAT_V1)
290 return -EINVAL;
291
292 if (ctx.flags & ~FS_POLICY_FLAGS_VALID)
293 return -EINVAL;
Jaegeuk Kim0b81d072015-05-15 16:26:10 -0700294
295 crypt_info = kmem_cache_alloc(fscrypt_info_cachep, GFP_NOFS);
296 if (!crypt_info)
297 return -ENOMEM;
298
299 crypt_info->ci_flags = ctx.flags;
300 crypt_info->ci_data_mode = ctx.contents_encryption_mode;
301 crypt_info->ci_filename_mode = ctx.filenames_encryption_mode;
302 crypt_info->ci_ctfm = NULL;
Daniel Walterb7e7cf72017-06-19 09:27:58 +0200303 crypt_info->ci_essiv_tfm = NULL;
Jaegeuk Kim0b81d072015-05-15 16:26:10 -0700304 memcpy(crypt_info->ci_master_key, ctx.master_key_descriptor,
305 sizeof(crypt_info->ci_master_key));
Jaegeuk Kim0b81d072015-05-15 16:26:10 -0700306
Eric Biggers8f398502016-09-15 13:32:11 -0400307 res = determine_cipher_type(crypt_info, inode, &cipher_str, &keysize);
308 if (res)
Jaegeuk Kim0b81d072015-05-15 16:26:10 -0700309 goto out;
Eric Biggers8f398502016-09-15 13:32:11 -0400310
Eric Biggersa6e08912016-11-13 20:41:09 -0500311 /*
312 * This cannot be a stack buffer because it is passed to the scatterlist
313 * crypto API as part of key derivation.
314 */
315 res = -ENOMEM;
316 raw_key = kmalloc(FS_MAX_KEY_SIZE, GFP_NOFS);
317 if (!raw_key)
318 goto out;
319
Daniel Walterb7e7cf72017-06-19 09:27:58 +0200320 res = validate_user_key(crypt_info, &ctx, raw_key, FS_KEY_DESC_PREFIX,
321 keysize);
Jaegeuk Kimb5a7aef2016-05-04 22:05:01 -0700322 if (res && inode->i_sb->s_cop->key_prefix) {
Eric Biggersa5d431e2017-01-05 13:51:18 -0800323 int res2 = validate_user_key(crypt_info, &ctx, raw_key,
Daniel Walterb7e7cf72017-06-19 09:27:58 +0200324 inode->i_sb->s_cop->key_prefix,
325 keysize);
Jaegeuk Kimb5a7aef2016-05-04 22:05:01 -0700326 if (res2) {
327 if (res2 == -ENOKEY)
328 res = -ENOKEY;
329 goto out;
330 }
331 } else if (res) {
Jaegeuk Kim0b81d072015-05-15 16:26:10 -0700332 goto out;
333 }
Linus Torvaldsd4075742016-03-21 11:03:02 -0700334 ctfm = crypto_alloc_skcipher(cipher_str, 0, 0);
Jaegeuk Kim0b81d072015-05-15 16:26:10 -0700335 if (!ctfm || IS_ERR(ctfm)) {
336 res = ctfm ? PTR_ERR(ctfm) : -ENOMEM;
Daniel Walterb7e7cf72017-06-19 09:27:58 +0200337 pr_debug("%s: error %d (inode %lu) allocating crypto tfm\n",
338 __func__, res, inode->i_ino);
Jaegeuk Kim0b81d072015-05-15 16:26:10 -0700339 goto out;
340 }
341 crypt_info->ci_ctfm = ctfm;
Linus Torvaldsd4075742016-03-21 11:03:02 -0700342 crypto_skcipher_clear_flags(ctfm, ~0);
343 crypto_skcipher_set_flags(ctfm, CRYPTO_TFM_REQ_WEAK_KEY);
Daniel Walterb7e7cf72017-06-19 09:27:58 +0200344 /*
345 * if the provided key is longer than keysize, we use the first
346 * keysize bytes of the derived key only
347 */
Eric Biggers8f398502016-09-15 13:32:11 -0400348 res = crypto_skcipher_setkey(ctfm, raw_key, keysize);
Jaegeuk Kim0b81d072015-05-15 16:26:10 -0700349 if (res)
350 goto out;
351
Daniel Walterb7e7cf72017-06-19 09:27:58 +0200352 if (S_ISREG(inode->i_mode) &&
353 crypt_info->ci_data_mode == FS_ENCRYPTION_MODE_AES_128_CBC) {
354 res = init_essiv_generator(crypt_info, raw_key, keysize);
355 if (res) {
356 pr_debug("%s: error %d (inode %lu) allocating essiv tfm\n",
357 __func__, res, inode->i_ino);
358 goto out;
359 }
360 }
Eric Biggers1b53cf92017-02-21 15:07:11 -0800361 if (cmpxchg(&inode->i_crypt_info, NULL, crypt_info) == NULL)
362 crypt_info = NULL;
Jaegeuk Kim0b81d072015-05-15 16:26:10 -0700363out:
364 if (res == -ENOKEY)
365 res = 0;
366 put_crypt_info(crypt_info);
Eric Biggersa6e08912016-11-13 20:41:09 -0500367 kzfree(raw_key);
Jaegeuk Kim0b81d072015-05-15 16:26:10 -0700368 return res;
369}
Eric Biggers1b53cf92017-02-21 15:07:11 -0800370EXPORT_SYMBOL(fscrypt_get_encryption_info);
Jaegeuk Kim0b81d072015-05-15 16:26:10 -0700371
372void fscrypt_put_encryption_info(struct inode *inode, struct fscrypt_info *ci)
373{
374 struct fscrypt_info *prev;
375
376 if (ci == NULL)
Mark Rutland6aa7de02017-10-23 14:07:29 -0700377 ci = READ_ONCE(inode->i_crypt_info);
Jaegeuk Kim0b81d072015-05-15 16:26:10 -0700378 if (ci == NULL)
379 return;
380
381 prev = cmpxchg(&inode->i_crypt_info, ci, NULL);
382 if (prev != ci)
383 return;
384
385 put_crypt_info(ci);
386}
387EXPORT_SYMBOL(fscrypt_put_encryption_info);