1feed8258SEric Biggers // SPDX-License-Identifier: GPL-2.0
2feed8258SEric Biggers /*
3feed8258SEric Biggers * Key setup facility for FS encryption support.
4feed8258SEric Biggers *
5feed8258SEric Biggers * Copyright (C) 2015, Google, Inc.
6feed8258SEric Biggers *
7feed8258SEric Biggers * Originally written by Michael Halcrow, Ildar Muslukhov, and Uday Savagaonkar.
8feed8258SEric Biggers * Heavily modified since then.
9feed8258SEric Biggers */
10feed8258SEric Biggers
11feed8258SEric Biggers #include <crypto/skcipher.h>
12a992b20cSEric Biggers #include <linux/random.h>
13feed8258SEric Biggers
14feed8258SEric Biggers #include "fscrypt_private.h"
15feed8258SEric Biggers
1685af90e5SEric Biggers struct fscrypt_mode fscrypt_modes[] = {
17feed8258SEric Biggers [FSCRYPT_MODE_AES_256_XTS] = {
18feed8258SEric Biggers .friendly_name = "AES-256-XTS",
19feed8258SEric Biggers .cipher_str = "xts(aes)",
20feed8258SEric Biggers .keysize = 64,
217f595d6aSEric Biggers .security_strength = 32,
22feed8258SEric Biggers .ivsize = 16,
235fee3609SSatya Tangirala .blk_crypto_mode = BLK_ENCRYPTION_MODE_AES_256_XTS,
24feed8258SEric Biggers },
25feed8258SEric Biggers [FSCRYPT_MODE_AES_256_CTS] = {
26feed8258SEric Biggers .friendly_name = "AES-256-CTS-CBC",
27feed8258SEric Biggers .cipher_str = "cts(cbc(aes))",
28feed8258SEric Biggers .keysize = 32,
297f595d6aSEric Biggers .security_strength = 32,
30feed8258SEric Biggers .ivsize = 16,
31feed8258SEric Biggers },
32feed8258SEric Biggers [FSCRYPT_MODE_AES_128_CBC] = {
334006d799SEric Biggers .friendly_name = "AES-128-CBC-ESSIV",
344006d799SEric Biggers .cipher_str = "essiv(cbc(aes),sha256)",
35feed8258SEric Biggers .keysize = 16,
367f595d6aSEric Biggers .security_strength = 16,
37feed8258SEric Biggers .ivsize = 16,
385fee3609SSatya Tangirala .blk_crypto_mode = BLK_ENCRYPTION_MODE_AES_128_CBC_ESSIV,
39feed8258SEric Biggers },
40feed8258SEric Biggers [FSCRYPT_MODE_AES_128_CTS] = {
41feed8258SEric Biggers .friendly_name = "AES-128-CTS-CBC",
42feed8258SEric Biggers .cipher_str = "cts(cbc(aes))",
43feed8258SEric Biggers .keysize = 16,
447f595d6aSEric Biggers .security_strength = 16,
45feed8258SEric Biggers .ivsize = 16,
46feed8258SEric Biggers },
47e0cefadaSTianjia Zhang [FSCRYPT_MODE_SM4_XTS] = {
48e0cefadaSTianjia Zhang .friendly_name = "SM4-XTS",
49e0cefadaSTianjia Zhang .cipher_str = "xts(sm4)",
50e0cefadaSTianjia Zhang .keysize = 32,
51e0cefadaSTianjia Zhang .security_strength = 16,
52e0cefadaSTianjia Zhang .ivsize = 16,
53e0cefadaSTianjia Zhang .blk_crypto_mode = BLK_ENCRYPTION_MODE_SM4_XTS,
54e0cefadaSTianjia Zhang },
55e0cefadaSTianjia Zhang [FSCRYPT_MODE_SM4_CTS] = {
56e0cefadaSTianjia Zhang .friendly_name = "SM4-CTS-CBC",
57e0cefadaSTianjia Zhang .cipher_str = "cts(cbc(sm4))",
58e0cefadaSTianjia Zhang .keysize = 16,
59e0cefadaSTianjia Zhang .security_strength = 16,
60e0cefadaSTianjia Zhang .ivsize = 16,
61e0cefadaSTianjia Zhang },
62feed8258SEric Biggers [FSCRYPT_MODE_ADIANTUM] = {
63feed8258SEric Biggers .friendly_name = "Adiantum",
64feed8258SEric Biggers .cipher_str = "adiantum(xchacha12,aes)",
65feed8258SEric Biggers .keysize = 32,
667f595d6aSEric Biggers .security_strength = 32,
67feed8258SEric Biggers .ivsize = 32,
685fee3609SSatya Tangirala .blk_crypto_mode = BLK_ENCRYPTION_MODE_ADIANTUM,
69feed8258SEric Biggers },
706b2a51ffSNathan Huckleberry [FSCRYPT_MODE_AES_256_HCTR2] = {
716b2a51ffSNathan Huckleberry .friendly_name = "AES-256-HCTR2",
726b2a51ffSNathan Huckleberry .cipher_str = "hctr2(aes)",
736b2a51ffSNathan Huckleberry .keysize = 32,
746b2a51ffSNathan Huckleberry .security_strength = 32,
756b2a51ffSNathan Huckleberry .ivsize = 32,
766b2a51ffSNathan Huckleberry },
77feed8258SEric Biggers };
78feed8258SEric Biggers
79e3b1078bSEric Biggers static DEFINE_MUTEX(fscrypt_mode_key_setup_mutex);
80e3b1078bSEric Biggers
81feed8258SEric Biggers static struct fscrypt_mode *
select_encryption_mode(const union fscrypt_policy * policy,const struct inode * inode)825dae460cSEric Biggers select_encryption_mode(const union fscrypt_policy *policy,
835dae460cSEric Biggers const struct inode *inode)
84feed8258SEric Biggers {
853ceb6543SEric Biggers BUILD_BUG_ON(ARRAY_SIZE(fscrypt_modes) != FSCRYPT_MODE_MAX + 1);
863ceb6543SEric Biggers
87feed8258SEric Biggers if (S_ISREG(inode->i_mode))
8885af90e5SEric Biggers return &fscrypt_modes[fscrypt_policy_contents_mode(policy)];
89feed8258SEric Biggers
90feed8258SEric Biggers if (S_ISDIR(inode->i_mode) || S_ISLNK(inode->i_mode))
9185af90e5SEric Biggers return &fscrypt_modes[fscrypt_policy_fnames_mode(policy)];
92feed8258SEric Biggers
93feed8258SEric Biggers WARN_ONCE(1, "fscrypt: filesystem tried to load encryption info for inode %lu, which is not encryptable (file type %d)\n",
94feed8258SEric Biggers inode->i_ino, (inode->i_mode & S_IFMT));
95feed8258SEric Biggers return ERR_PTR(-EINVAL);
96feed8258SEric Biggers }
97feed8258SEric Biggers
98feed8258SEric Biggers /* Create a symmetric cipher object for the given encryption mode and key */
995fee3609SSatya Tangirala static struct crypto_skcipher *
fscrypt_allocate_skcipher(struct fscrypt_mode * mode,const u8 * raw_key,const struct inode * inode)1005fee3609SSatya Tangirala fscrypt_allocate_skcipher(struct fscrypt_mode *mode, const u8 *raw_key,
101feed8258SEric Biggers const struct inode *inode)
102feed8258SEric Biggers {
103feed8258SEric Biggers struct crypto_skcipher *tfm;
104feed8258SEric Biggers int err;
105feed8258SEric Biggers
106feed8258SEric Biggers tfm = crypto_alloc_skcipher(mode->cipher_str, 0, 0);
107feed8258SEric Biggers if (IS_ERR(tfm)) {
108feed8258SEric Biggers if (PTR_ERR(tfm) == -ENOENT) {
109feed8258SEric Biggers fscrypt_warn(inode,
110feed8258SEric Biggers "Missing crypto API support for %s (API name: \"%s\")",
111feed8258SEric Biggers mode->friendly_name, mode->cipher_str);
112feed8258SEric Biggers return ERR_PTR(-ENOPKG);
113feed8258SEric Biggers }
114feed8258SEric Biggers fscrypt_err(inode, "Error allocating '%s' transform: %ld",
115feed8258SEric Biggers mode->cipher_str, PTR_ERR(tfm));
116feed8258SEric Biggers return tfm;
117feed8258SEric Biggers }
118a7a5bc5fSEric Biggers if (!xchg(&mode->logged_cryptoapi_impl, 1)) {
119feed8258SEric Biggers /*
120feed8258SEric Biggers * fscrypt performance can vary greatly depending on which
121feed8258SEric Biggers * crypto algorithm implementation is used. Help people debug
122feed8258SEric Biggers * performance problems by logging the ->cra_driver_name the
123ff73c2c0SEric Biggers * first time a mode is used.
124feed8258SEric Biggers */
125feed8258SEric Biggers pr_info("fscrypt: %s using implementation \"%s\"\n",
1266e1adb88SEric Biggers mode->friendly_name, crypto_skcipher_driver_name(tfm));
127feed8258SEric Biggers }
12841b2ad80SEric Biggers if (WARN_ON_ONCE(crypto_skcipher_ivsize(tfm) != mode->ivsize)) {
129c64cfb98SEric Biggers err = -EINVAL;
130c64cfb98SEric Biggers goto err_free_tfm;
131c64cfb98SEric Biggers }
132feed8258SEric Biggers crypto_skcipher_set_flags(tfm, CRYPTO_TFM_REQ_FORBID_WEAK_KEYS);
133feed8258SEric Biggers err = crypto_skcipher_setkey(tfm, raw_key, mode->keysize);
134feed8258SEric Biggers if (err)
135feed8258SEric Biggers goto err_free_tfm;
136feed8258SEric Biggers
137feed8258SEric Biggers return tfm;
138feed8258SEric Biggers
139feed8258SEric Biggers err_free_tfm:
140feed8258SEric Biggers crypto_free_skcipher(tfm);
141feed8258SEric Biggers return ERR_PTR(err);
142feed8258SEric Biggers }
143feed8258SEric Biggers
1445fee3609SSatya Tangirala /*
1455fee3609SSatya Tangirala * Prepare the crypto transform object or blk-crypto key in @prep_key, given the
146b7e072f9SEric Biggers * raw key, encryption mode (@ci->ci_mode), flag indicating which encryption
147b7e072f9SEric Biggers * implementation (fs-layer or blk-crypto) will be used (@ci->ci_inlinecrypt),
148b7e072f9SEric Biggers * and IV generation method (@ci->ci_policy.flags).
1495fee3609SSatya Tangirala */
fscrypt_prepare_key(struct fscrypt_prepared_key * prep_key,const u8 * raw_key,const struct fscrypt_info * ci)1505fee3609SSatya Tangirala int fscrypt_prepare_key(struct fscrypt_prepared_key *prep_key,
1515fee3609SSatya Tangirala const u8 *raw_key, const struct fscrypt_info *ci)
152feed8258SEric Biggers {
1534006d799SEric Biggers struct crypto_skcipher *tfm;
154feed8258SEric Biggers
1555fee3609SSatya Tangirala if (fscrypt_using_inline_encryption(ci))
1565fee3609SSatya Tangirala return fscrypt_prepare_inline_crypt_key(prep_key, raw_key, ci);
1575fee3609SSatya Tangirala
158f592efe7SEric Biggers tfm = fscrypt_allocate_skcipher(ci->ci_mode, raw_key, ci->ci_inode);
1594006d799SEric Biggers if (IS_ERR(tfm))
1604006d799SEric Biggers return PTR_ERR(tfm);
1615fee3609SSatya Tangirala /*
16297c6327fSEric Biggers * Pairs with the smp_load_acquire() in fscrypt_is_key_prepared().
16397c6327fSEric Biggers * I.e., here we publish ->tfm with a RELEASE barrier so that
16497c6327fSEric Biggers * concurrent tasks can ACQUIRE it. Note that this concurrency is only
16597c6327fSEric Biggers * possible for per-mode keys, not for per-file keys.
1665fee3609SSatya Tangirala */
1675fee3609SSatya Tangirala smp_store_release(&prep_key->tfm, tfm);
168feed8258SEric Biggers return 0;
169feed8258SEric Biggers }
170feed8258SEric Biggers
1715fee3609SSatya Tangirala /* Destroy a crypto transform object and/or blk-crypto key. */
fscrypt_destroy_prepared_key(struct super_block * sb,struct fscrypt_prepared_key * prep_key)17222e9947aSEric Biggers void fscrypt_destroy_prepared_key(struct super_block *sb,
17322e9947aSEric Biggers struct fscrypt_prepared_key *prep_key)
1745fee3609SSatya Tangirala {
1755fee3609SSatya Tangirala crypto_free_skcipher(prep_key->tfm);
17622e9947aSEric Biggers fscrypt_destroy_inline_crypt_key(sb, prep_key);
177d7e7b9afSEric Biggers memzero_explicit(prep_key, sizeof(*prep_key));
1785fee3609SSatya Tangirala }
1795fee3609SSatya Tangirala
1805fee3609SSatya Tangirala /* Given a per-file encryption key, set up the file's crypto transform object */
fscrypt_set_per_file_enc_key(struct fscrypt_info * ci,const u8 * raw_key)1815fee3609SSatya Tangirala int fscrypt_set_per_file_enc_key(struct fscrypt_info *ci, const u8 *raw_key)
1825fee3609SSatya Tangirala {
1835fee3609SSatya Tangirala ci->ci_owns_key = true;
1845fee3609SSatya Tangirala return fscrypt_prepare_key(&ci->ci_enc_key, raw_key, ci);
1855fee3609SSatya Tangirala }
1865fee3609SSatya Tangirala
setup_per_mode_enc_key(struct fscrypt_info * ci,struct fscrypt_master_key * mk,struct fscrypt_prepared_key * keys,u8 hkdf_context,bool include_fs_uuid)187f592efe7SEric Biggers static int setup_per_mode_enc_key(struct fscrypt_info *ci,
188b103fb76SEric Biggers struct fscrypt_master_key *mk,
1895fee3609SSatya Tangirala struct fscrypt_prepared_key *keys,
190b103fb76SEric Biggers u8 hkdf_context, bool include_fs_uuid)
1915dae460cSEric Biggers {
192b103fb76SEric Biggers const struct inode *inode = ci->ci_inode;
193b103fb76SEric Biggers const struct super_block *sb = inode->i_sb;
1945dae460cSEric Biggers struct fscrypt_mode *mode = ci->ci_mode;
19585af90e5SEric Biggers const u8 mode_num = mode - fscrypt_modes;
1965fee3609SSatya Tangirala struct fscrypt_prepared_key *prep_key;
1975dae460cSEric Biggers u8 mode_key[FSCRYPT_MAX_KEY_SIZE];
198b103fb76SEric Biggers u8 hkdf_info[sizeof(mode_num) + sizeof(sb->s_uuid)];
199b103fb76SEric Biggers unsigned int hkdf_infolen = 0;
2005dae460cSEric Biggers int err;
2015dae460cSEric Biggers
20241b2ad80SEric Biggers if (WARN_ON_ONCE(mode_num > FSCRYPT_MODE_MAX))
2035dae460cSEric Biggers return -EINVAL;
2045dae460cSEric Biggers
2055fee3609SSatya Tangirala prep_key = &keys[mode_num];
2065fee3609SSatya Tangirala if (fscrypt_is_key_prepared(prep_key, ci)) {
2075fee3609SSatya Tangirala ci->ci_enc_key = *prep_key;
208e3b1078bSEric Biggers return 0;
209e3b1078bSEric Biggers }
210e3b1078bSEric Biggers
211e3b1078bSEric Biggers mutex_lock(&fscrypt_mode_key_setup_mutex);
212e3b1078bSEric Biggers
2135fee3609SSatya Tangirala if (fscrypt_is_key_prepared(prep_key, ci))
214e3b1078bSEric Biggers goto done_unlock;
2155dae460cSEric Biggers
2165dae460cSEric Biggers BUILD_BUG_ON(sizeof(mode_num) != 1);
217b103fb76SEric Biggers BUILD_BUG_ON(sizeof(sb->s_uuid) != 16);
218b103fb76SEric Biggers BUILD_BUG_ON(sizeof(hkdf_info) != 17);
219b103fb76SEric Biggers hkdf_info[hkdf_infolen++] = mode_num;
220b103fb76SEric Biggers if (include_fs_uuid) {
221b103fb76SEric Biggers memcpy(&hkdf_info[hkdf_infolen], &sb->s_uuid,
222b103fb76SEric Biggers sizeof(sb->s_uuid));
223b103fb76SEric Biggers hkdf_infolen += sizeof(sb->s_uuid);
224b103fb76SEric Biggers }
2255dae460cSEric Biggers err = fscrypt_hkdf_expand(&mk->mk_secret.hkdf,
226b103fb76SEric Biggers hkdf_context, hkdf_info, hkdf_infolen,
2275dae460cSEric Biggers mode_key, mode->keysize);
2285dae460cSEric Biggers if (err)
229e3b1078bSEric Biggers goto out_unlock;
2305fee3609SSatya Tangirala err = fscrypt_prepare_key(prep_key, mode_key, ci);
2315dae460cSEric Biggers memzero_explicit(mode_key, mode->keysize);
2325fee3609SSatya Tangirala if (err)
233e3b1078bSEric Biggers goto out_unlock;
234e3b1078bSEric Biggers done_unlock:
2355fee3609SSatya Tangirala ci->ci_enc_key = *prep_key;
236e3b1078bSEric Biggers err = 0;
237e3b1078bSEric Biggers out_unlock:
238e3b1078bSEric Biggers mutex_unlock(&fscrypt_mode_key_setup_mutex);
239e3b1078bSEric Biggers return err;
2405dae460cSEric Biggers }
2415dae460cSEric Biggers
2422fc2b430SEric Biggers /*
2432fc2b430SEric Biggers * Derive a SipHash key from the given fscrypt master key and the given
2442fc2b430SEric Biggers * application-specific information string.
2452fc2b430SEric Biggers *
2462fc2b430SEric Biggers * Note that the KDF produces a byte array, but the SipHash APIs expect the key
2472fc2b430SEric Biggers * as a pair of 64-bit words. Therefore, on big endian CPUs we have to do an
2482fc2b430SEric Biggers * endianness swap in order to get the same results as on little endian CPUs.
2492fc2b430SEric Biggers */
fscrypt_derive_siphash_key(const struct fscrypt_master_key * mk,u8 context,const u8 * info,unsigned int infolen,siphash_key_t * key)2502fc2b430SEric Biggers static int fscrypt_derive_siphash_key(const struct fscrypt_master_key *mk,
2512fc2b430SEric Biggers u8 context, const u8 *info,
2522fc2b430SEric Biggers unsigned int infolen, siphash_key_t *key)
2532fc2b430SEric Biggers {
2542fc2b430SEric Biggers int err;
2552fc2b430SEric Biggers
2562fc2b430SEric Biggers err = fscrypt_hkdf_expand(&mk->mk_secret.hkdf, context, info, infolen,
2572fc2b430SEric Biggers (u8 *)key, sizeof(*key));
2582fc2b430SEric Biggers if (err)
2592fc2b430SEric Biggers return err;
2602fc2b430SEric Biggers
2612fc2b430SEric Biggers BUILD_BUG_ON(sizeof(*key) != 16);
2622fc2b430SEric Biggers BUILD_BUG_ON(ARRAY_SIZE(key->key) != 2);
2632fc2b430SEric Biggers le64_to_cpus(&key->key[0]);
2642fc2b430SEric Biggers le64_to_cpus(&key->key[1]);
2652fc2b430SEric Biggers return 0;
2662fc2b430SEric Biggers }
2672fc2b430SEric Biggers
fscrypt_derive_dirhash_key(struct fscrypt_info * ci,const struct fscrypt_master_key * mk)268aa408f83SDaniel Rosenberg int fscrypt_derive_dirhash_key(struct fscrypt_info *ci,
269aa408f83SDaniel Rosenberg const struct fscrypt_master_key *mk)
270aa408f83SDaniel Rosenberg {
271aa408f83SDaniel Rosenberg int err;
272aa408f83SDaniel Rosenberg
2732fc2b430SEric Biggers err = fscrypt_derive_siphash_key(mk, HKDF_CONTEXT_DIRHASH_KEY,
2741d6217a4SEric Biggers ci->ci_nonce, FSCRYPT_FILE_NONCE_SIZE,
2752fc2b430SEric Biggers &ci->ci_dirhash_key);
276aa408f83SDaniel Rosenberg if (err)
277aa408f83SDaniel Rosenberg return err;
278aa408f83SDaniel Rosenberg ci->ci_dirhash_key_initialized = true;
279aa408f83SDaniel Rosenberg return 0;
280aa408f83SDaniel Rosenberg }
281aa408f83SDaniel Rosenberg
fscrypt_hash_inode_number(struct fscrypt_info * ci,const struct fscrypt_master_key * mk)282a992b20cSEric Biggers void fscrypt_hash_inode_number(struct fscrypt_info *ci,
283a992b20cSEric Biggers const struct fscrypt_master_key *mk)
284a992b20cSEric Biggers {
28541b2ad80SEric Biggers WARN_ON_ONCE(ci->ci_inode->i_ino == 0);
28641b2ad80SEric Biggers WARN_ON_ONCE(!mk->mk_ino_hash_key_initialized);
287a992b20cSEric Biggers
288a992b20cSEric Biggers ci->ci_hashed_ino = (u32)siphash_1u64(ci->ci_inode->i_ino,
289a992b20cSEric Biggers &mk->mk_ino_hash_key);
290a992b20cSEric Biggers }
291a992b20cSEric Biggers
fscrypt_setup_iv_ino_lblk_32_key(struct fscrypt_info * ci,struct fscrypt_master_key * mk)292e3b1078bSEric Biggers static int fscrypt_setup_iv_ino_lblk_32_key(struct fscrypt_info *ci,
293e3b1078bSEric Biggers struct fscrypt_master_key *mk)
294e3b1078bSEric Biggers {
295e3b1078bSEric Biggers int err;
296e3b1078bSEric Biggers
297e3b1078bSEric Biggers err = setup_per_mode_enc_key(ci, mk, mk->mk_iv_ino_lblk_32_keys,
298e3b1078bSEric Biggers HKDF_CONTEXT_IV_INO_LBLK_32_KEY, true);
299e3b1078bSEric Biggers if (err)
300e3b1078bSEric Biggers return err;
301e3b1078bSEric Biggers
302e3b1078bSEric Biggers /* pairs with smp_store_release() below */
303e3b1078bSEric Biggers if (!smp_load_acquire(&mk->mk_ino_hash_key_initialized)) {
304e3b1078bSEric Biggers
305e3b1078bSEric Biggers mutex_lock(&fscrypt_mode_key_setup_mutex);
306e3b1078bSEric Biggers
307e3b1078bSEric Biggers if (mk->mk_ino_hash_key_initialized)
308e3b1078bSEric Biggers goto unlock;
309e3b1078bSEric Biggers
3102fc2b430SEric Biggers err = fscrypt_derive_siphash_key(mk,
3112fc2b430SEric Biggers HKDF_CONTEXT_INODE_HASH_KEY,
3122fc2b430SEric Biggers NULL, 0, &mk->mk_ino_hash_key);
313e3b1078bSEric Biggers if (err)
314e3b1078bSEric Biggers goto unlock;
315e3b1078bSEric Biggers /* pairs with smp_load_acquire() above */
316e3b1078bSEric Biggers smp_store_release(&mk->mk_ino_hash_key_initialized, true);
317e3b1078bSEric Biggers unlock:
318e3b1078bSEric Biggers mutex_unlock(&fscrypt_mode_key_setup_mutex);
319e3b1078bSEric Biggers if (err)
320e3b1078bSEric Biggers return err;
321e3b1078bSEric Biggers }
322e3b1078bSEric Biggers
323a992b20cSEric Biggers /*
324a992b20cSEric Biggers * New inodes may not have an inode number assigned yet.
325a992b20cSEric Biggers * Hashing their inode number is delayed until later.
326a992b20cSEric Biggers */
32792cfcd03SEric Biggers if (ci->ci_inode->i_ino)
328a992b20cSEric Biggers fscrypt_hash_inode_number(ci, mk);
329e3b1078bSEric Biggers return 0;
330e3b1078bSEric Biggers }
331e3b1078bSEric Biggers
fscrypt_setup_v2_file_key(struct fscrypt_info * ci,struct fscrypt_master_key * mk,bool need_dirhash_key)3325dae460cSEric Biggers static int fscrypt_setup_v2_file_key(struct fscrypt_info *ci,
333a992b20cSEric Biggers struct fscrypt_master_key *mk,
334a992b20cSEric Biggers bool need_dirhash_key)
3355dae460cSEric Biggers {
3365dae460cSEric Biggers int err;
3375dae460cSEric Biggers
3385dae460cSEric Biggers if (ci->ci_policy.v2.flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY) {
3395dae460cSEric Biggers /*
340f592efe7SEric Biggers * DIRECT_KEY: instead of deriving per-file encryption keys, the
341f592efe7SEric Biggers * per-file nonce will be included in all the IVs. But unlike
342f592efe7SEric Biggers * v1 policies, for v2 policies in this case we don't encrypt
343f592efe7SEric Biggers * with the master key directly but rather derive a per-mode
344f592efe7SEric Biggers * encryption key. This ensures that the master key is
345f592efe7SEric Biggers * consistently used only for HKDF, avoiding key reuse issues.
3465dae460cSEric Biggers */
347e3b1078bSEric Biggers err = setup_per_mode_enc_key(ci, mk, mk->mk_direct_keys,
348b103fb76SEric Biggers HKDF_CONTEXT_DIRECT_KEY, false);
349b103fb76SEric Biggers } else if (ci->ci_policy.v2.flags &
350b103fb76SEric Biggers FSCRYPT_POLICY_FLAG_IV_INO_LBLK_64) {
351b103fb76SEric Biggers /*
352b103fb76SEric Biggers * IV_INO_LBLK_64: encryption keys are derived from (master_key,
353b103fb76SEric Biggers * mode_num, filesystem_uuid), and inode number is included in
354b103fb76SEric Biggers * the IVs. This format is optimized for use with inline
355e3b1078bSEric Biggers * encryption hardware compliant with the UFS standard.
356b103fb76SEric Biggers */
357e3b1078bSEric Biggers err = setup_per_mode_enc_key(ci, mk, mk->mk_iv_ino_lblk_64_keys,
358f592efe7SEric Biggers HKDF_CONTEXT_IV_INO_LBLK_64_KEY,
359f592efe7SEric Biggers true);
360e3b1078bSEric Biggers } else if (ci->ci_policy.v2.flags &
361e3b1078bSEric Biggers FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32) {
362e3b1078bSEric Biggers err = fscrypt_setup_iv_ino_lblk_32_key(ci, mk);
363aa408f83SDaniel Rosenberg } else {
364aa408f83SDaniel Rosenberg u8 derived_key[FSCRYPT_MAX_KEY_SIZE];
3655dae460cSEric Biggers
3665dae460cSEric Biggers err = fscrypt_hkdf_expand(&mk->mk_secret.hkdf,
367f592efe7SEric Biggers HKDF_CONTEXT_PER_FILE_ENC_KEY,
3681d6217a4SEric Biggers ci->ci_nonce, FSCRYPT_FILE_NONCE_SIZE,
3695dae460cSEric Biggers derived_key, ci->ci_mode->keysize);
3705dae460cSEric Biggers if (err)
3715dae460cSEric Biggers return err;
3725dae460cSEric Biggers
373f592efe7SEric Biggers err = fscrypt_set_per_file_enc_key(ci, derived_key);
3745dae460cSEric Biggers memzero_explicit(derived_key, ci->ci_mode->keysize);
375aa408f83SDaniel Rosenberg }
376aa408f83SDaniel Rosenberg if (err)
3775dae460cSEric Biggers return err;
378aa408f83SDaniel Rosenberg
379aa408f83SDaniel Rosenberg /* Derive a secret dirhash key for directories that need it. */
380a992b20cSEric Biggers if (need_dirhash_key) {
381aa408f83SDaniel Rosenberg err = fscrypt_derive_dirhash_key(ci, mk);
382aa408f83SDaniel Rosenberg if (err)
383aa408f83SDaniel Rosenberg return err;
384aa408f83SDaniel Rosenberg }
385aa408f83SDaniel Rosenberg
386aa408f83SDaniel Rosenberg return 0;
3875dae460cSEric Biggers }
3885dae460cSEric Biggers
389feed8258SEric Biggers /*
3907f595d6aSEric Biggers * Check whether the size of the given master key (@mk) is appropriate for the
3917f595d6aSEric Biggers * encryption settings which a particular file will use (@ci).
3927f595d6aSEric Biggers *
3937f595d6aSEric Biggers * If the file uses a v1 encryption policy, then the master key must be at least
3947f595d6aSEric Biggers * as long as the derived key, as this is a requirement of the v1 KDF.
3957f595d6aSEric Biggers *
3967f595d6aSEric Biggers * Otherwise, the KDF can accept any size key, so we enforce a slightly looser
3977f595d6aSEric Biggers * requirement: we require that the size of the master key be at least the
3987f595d6aSEric Biggers * maximum security strength of any algorithm whose key will be derived from it
3997f595d6aSEric Biggers * (but in practice we only need to consider @ci->ci_mode, since any other
4007f595d6aSEric Biggers * possible subkeys such as DIRHASH and INODE_HASH will never increase the
4017f595d6aSEric Biggers * required key size over @ci->ci_mode). This allows AES-256-XTS keys to be
4027f595d6aSEric Biggers * derived from a 256-bit master key, which is cryptographically sufficient,
4037f595d6aSEric Biggers * rather than requiring a 512-bit master key which is unnecessarily long. (We
4047f595d6aSEric Biggers * still allow 512-bit master keys if the user chooses to use them, though.)
4057f595d6aSEric Biggers */
fscrypt_valid_master_key_size(const struct fscrypt_master_key * mk,const struct fscrypt_info * ci)4067f595d6aSEric Biggers static bool fscrypt_valid_master_key_size(const struct fscrypt_master_key *mk,
4077f595d6aSEric Biggers const struct fscrypt_info *ci)
4087f595d6aSEric Biggers {
4097f595d6aSEric Biggers unsigned int min_keysize;
4107f595d6aSEric Biggers
4117f595d6aSEric Biggers if (ci->ci_policy.version == FSCRYPT_POLICY_V1)
4127f595d6aSEric Biggers min_keysize = ci->ci_mode->keysize;
4137f595d6aSEric Biggers else
4147f595d6aSEric Biggers min_keysize = ci->ci_mode->security_strength;
4157f595d6aSEric Biggers
4167f595d6aSEric Biggers if (mk->mk_secret.size < min_keysize) {
4177f595d6aSEric Biggers fscrypt_warn(NULL,
4187f595d6aSEric Biggers "key with %s %*phN is too short (got %u bytes, need %u+ bytes)",
4197f595d6aSEric Biggers master_key_spec_type(&mk->mk_spec),
4207f595d6aSEric Biggers master_key_spec_len(&mk->mk_spec),
4217f595d6aSEric Biggers (u8 *)&mk->mk_spec.u,
4227f595d6aSEric Biggers mk->mk_secret.size, min_keysize);
4237f595d6aSEric Biggers return false;
4247f595d6aSEric Biggers }
4257f595d6aSEric Biggers return true;
4267f595d6aSEric Biggers }
4277f595d6aSEric Biggers
4287f595d6aSEric Biggers /*
429feed8258SEric Biggers * Find the master key, then set up the inode's actual encryption key.
430b1c0ec35SEric Biggers *
431d7e7b9afSEric Biggers * If the master key is found in the filesystem-level keyring, then it is
432d7e7b9afSEric Biggers * returned in *mk_ret with its semaphore read-locked. This is needed to ensure
433d7e7b9afSEric Biggers * that only one task links the fscrypt_info into ->mk_decrypted_inodes (as
434d7e7b9afSEric Biggers * multiple tasks may race to create an fscrypt_info for the same inode), and to
435d7e7b9afSEric Biggers * synchronize the master key being removed with a new inode starting to use it.
436feed8258SEric Biggers */
setup_file_encryption_key(struct fscrypt_info * ci,bool need_dirhash_key,struct fscrypt_master_key ** mk_ret)437b1c0ec35SEric Biggers static int setup_file_encryption_key(struct fscrypt_info *ci,
438a992b20cSEric Biggers bool need_dirhash_key,
439d7e7b9afSEric Biggers struct fscrypt_master_key **mk_ret)
440feed8258SEric Biggers {
44160e463f0SEric Biggers struct super_block *sb = ci->ci_inode->i_sb;
44222d94f49SEric Biggers struct fscrypt_key_specifier mk_spec;
443d7e7b9afSEric Biggers struct fscrypt_master_key *mk;
44422d94f49SEric Biggers int err;
44522d94f49SEric Biggers
4465fee3609SSatya Tangirala err = fscrypt_select_encryption_impl(ci);
4475fee3609SSatya Tangirala if (err)
4485fee3609SSatya Tangirala return err;
4495fee3609SSatya Tangirala
450bfb9700bSEric Biggers err = fscrypt_policy_to_key_spec(&ci->ci_policy, &mk_spec);
451bfb9700bSEric Biggers if (err)
452bfb9700bSEric Biggers return err;
45322d94f49SEric Biggers
45460e463f0SEric Biggers mk = fscrypt_find_master_key(sb, &mk_spec);
45560e463f0SEric Biggers if (unlikely(!mk)) {
45660e463f0SEric Biggers const union fscrypt_policy *dummy_policy =
45760e463f0SEric Biggers fscrypt_get_dummy_policy(sb);
45860e463f0SEric Biggers
45960e463f0SEric Biggers /*
46060e463f0SEric Biggers * Add the test_dummy_encryption key on-demand. In principle,
46160e463f0SEric Biggers * it should be added at mount time. Do it here instead so that
46260e463f0SEric Biggers * the individual filesystems don't need to worry about adding
46360e463f0SEric Biggers * this key at mount time and cleaning up on mount failure.
46460e463f0SEric Biggers */
46560e463f0SEric Biggers if (dummy_policy &&
46660e463f0SEric Biggers fscrypt_policies_equal(dummy_policy, &ci->ci_policy)) {
467097d7c1fSEric Biggers err = fscrypt_add_test_dummy_key(sb, &mk_spec);
46860e463f0SEric Biggers if (err)
46960e463f0SEric Biggers return err;
47060e463f0SEric Biggers mk = fscrypt_find_master_key(sb, &mk_spec);
47160e463f0SEric Biggers }
47260e463f0SEric Biggers }
47360e463f0SEric Biggers if (unlikely(!mk)) {
474d7e7b9afSEric Biggers if (ci->ci_policy.version != FSCRYPT_POLICY_V1)
475d7e7b9afSEric Biggers return -ENOKEY;
47622d94f49SEric Biggers
4775dae460cSEric Biggers /*
4785dae460cSEric Biggers * As a legacy fallback for v1 policies, search for the key in
4795dae460cSEric Biggers * the current task's subscribed keyrings too. Don't move this
4805dae460cSEric Biggers * to before the search of ->s_master_keys, since users
4815dae460cSEric Biggers * shouldn't be able to override filesystem-level keys.
4825dae460cSEric Biggers */
483feed8258SEric Biggers return fscrypt_setup_v1_file_key_via_subscribed_keyrings(ci);
484feed8258SEric Biggers }
485d7e7b9afSEric Biggers down_read(&mk->mk_sem);
486b1c0ec35SEric Biggers
487b1c0ec35SEric Biggers /* Has the secret been removed (via FS_IOC_REMOVE_ENCRYPTION_KEY)? */
488b1c0ec35SEric Biggers if (!is_master_key_secret_present(&mk->mk_secret)) {
489b1c0ec35SEric Biggers err = -ENOKEY;
490b1c0ec35SEric Biggers goto out_release_key;
491b1c0ec35SEric Biggers }
49222d94f49SEric Biggers
4937f595d6aSEric Biggers if (!fscrypt_valid_master_key_size(mk, ci)) {
49422d94f49SEric Biggers err = -ENOKEY;
49522d94f49SEric Biggers goto out_release_key;
49622d94f49SEric Biggers }
49722d94f49SEric Biggers
4985dae460cSEric Biggers switch (ci->ci_policy.version) {
4995dae460cSEric Biggers case FSCRYPT_POLICY_V1:
50022d94f49SEric Biggers err = fscrypt_setup_v1_file_key(ci, mk->mk_secret.raw);
5015dae460cSEric Biggers break;
5025dae460cSEric Biggers case FSCRYPT_POLICY_V2:
503a992b20cSEric Biggers err = fscrypt_setup_v2_file_key(ci, mk, need_dirhash_key);
5045dae460cSEric Biggers break;
5055dae460cSEric Biggers default:
50641b2ad80SEric Biggers WARN_ON_ONCE(1);
5075dae460cSEric Biggers err = -EINVAL;
5085dae460cSEric Biggers break;
5095dae460cSEric Biggers }
510b1c0ec35SEric Biggers if (err)
511b1c0ec35SEric Biggers goto out_release_key;
512b1c0ec35SEric Biggers
513d7e7b9afSEric Biggers *mk_ret = mk;
514b1c0ec35SEric Biggers return 0;
51522d94f49SEric Biggers
51622d94f49SEric Biggers out_release_key:
517d7e7b9afSEric Biggers up_read(&mk->mk_sem);
518d7e7b9afSEric Biggers fscrypt_put_master_key(mk);
51922d94f49SEric Biggers return err;
52022d94f49SEric Biggers }
52122d94f49SEric Biggers
put_crypt_info(struct fscrypt_info * ci)522feed8258SEric Biggers static void put_crypt_info(struct fscrypt_info *ci)
523feed8258SEric Biggers {
524d7e7b9afSEric Biggers struct fscrypt_master_key *mk;
525b1c0ec35SEric Biggers
526feed8258SEric Biggers if (!ci)
527feed8258SEric Biggers return;
528feed8258SEric Biggers
5294006d799SEric Biggers if (ci->ci_direct_key)
530feed8258SEric Biggers fscrypt_put_direct_key(ci->ci_direct_key);
531b103fb76SEric Biggers else if (ci->ci_owns_key)
53222e9947aSEric Biggers fscrypt_destroy_prepared_key(ci->ci_inode->i_sb,
53322e9947aSEric Biggers &ci->ci_enc_key);
534b1c0ec35SEric Biggers
535d7e7b9afSEric Biggers mk = ci->ci_master_key;
536d7e7b9afSEric Biggers if (mk) {
537b1c0ec35SEric Biggers /*
538b1c0ec35SEric Biggers * Remove this inode from the list of inodes that were unlocked
539d7e7b9afSEric Biggers * with the master key. In addition, if we're removing the last
540d7e7b9afSEric Biggers * inode from a master key struct that already had its secret
541d7e7b9afSEric Biggers * removed, then complete the full removal of the struct.
542b1c0ec35SEric Biggers */
543b1c0ec35SEric Biggers spin_lock(&mk->mk_decrypted_inodes_lock);
544b1c0ec35SEric Biggers list_del(&ci->ci_master_key_link);
545b1c0ec35SEric Biggers spin_unlock(&mk->mk_decrypted_inodes_lock);
54602aef422SEric Biggers fscrypt_put_master_key_activeref(ci->ci_inode->i_sb, mk);
547b1c0ec35SEric Biggers }
5486f99756dSEric Biggers memzero_explicit(ci, sizeof(*ci));
549feed8258SEric Biggers kmem_cache_free(fscrypt_info_cachep, ci);
550feed8258SEric Biggers }
551feed8258SEric Biggers
552a992b20cSEric Biggers static int
fscrypt_setup_encryption_info(struct inode * inode,const union fscrypt_policy * policy,const u8 nonce[FSCRYPT_FILE_NONCE_SIZE],bool need_dirhash_key)553a992b20cSEric Biggers fscrypt_setup_encryption_info(struct inode *inode,
554a992b20cSEric Biggers const union fscrypt_policy *policy,
555a992b20cSEric Biggers const u8 nonce[FSCRYPT_FILE_NONCE_SIZE],
556a992b20cSEric Biggers bool need_dirhash_key)
557feed8258SEric Biggers {
558feed8258SEric Biggers struct fscrypt_info *crypt_info;
559feed8258SEric Biggers struct fscrypt_mode *mode;
560d7e7b9afSEric Biggers struct fscrypt_master_key *mk = NULL;
561feed8258SEric Biggers int res;
562feed8258SEric Biggers
563*83e57e47SEric Biggers res = fscrypt_initialize(inode->i_sb);
564feed8258SEric Biggers if (res)
565feed8258SEric Biggers return res;
566feed8258SEric Biggers
5679dad5febSEric Biggers crypt_info = kmem_cache_zalloc(fscrypt_info_cachep, GFP_KERNEL);
568feed8258SEric Biggers if (!crypt_info)
569feed8258SEric Biggers return -ENOMEM;
570feed8258SEric Biggers
571feed8258SEric Biggers crypt_info->ci_inode = inode;
572a992b20cSEric Biggers crypt_info->ci_policy = *policy;
573a992b20cSEric Biggers memcpy(crypt_info->ci_nonce, nonce, FSCRYPT_FILE_NONCE_SIZE);
5745dae460cSEric Biggers
5755dae460cSEric Biggers mode = select_encryption_mode(&crypt_info->ci_policy, inode);
576feed8258SEric Biggers if (IS_ERR(mode)) {
577feed8258SEric Biggers res = PTR_ERR(mode);
578feed8258SEric Biggers goto out;
579feed8258SEric Biggers }
58041b2ad80SEric Biggers WARN_ON_ONCE(mode->ivsize > FSCRYPT_MAX_IV_SIZE);
581feed8258SEric Biggers crypt_info->ci_mode = mode;
582feed8258SEric Biggers
583d7e7b9afSEric Biggers res = setup_file_encryption_key(crypt_info, need_dirhash_key, &mk);
584feed8258SEric Biggers if (res)
585feed8258SEric Biggers goto out;
586feed8258SEric Biggers
587ab673b98SEric Biggers /*
588a992b20cSEric Biggers * For existing inodes, multiple tasks may race to set ->i_crypt_info.
589a992b20cSEric Biggers * So use cmpxchg_release(). This pairs with the smp_load_acquire() in
590ab673b98SEric Biggers * fscrypt_get_info(). I.e., here we publish ->i_crypt_info with a
591ab673b98SEric Biggers * RELEASE barrier so that other tasks can ACQUIRE it.
592ab673b98SEric Biggers */
593b1c0ec35SEric Biggers if (cmpxchg_release(&inode->i_crypt_info, NULL, crypt_info) == NULL) {
594ab673b98SEric Biggers /*
595ab673b98SEric Biggers * We won the race and set ->i_crypt_info to our crypt_info.
596ab673b98SEric Biggers * Now link it into the master key's inode list.
597ab673b98SEric Biggers */
598d7e7b9afSEric Biggers if (mk) {
599d7e7b9afSEric Biggers crypt_info->ci_master_key = mk;
600d7e7b9afSEric Biggers refcount_inc(&mk->mk_active_refs);
601b1c0ec35SEric Biggers spin_lock(&mk->mk_decrypted_inodes_lock);
602b1c0ec35SEric Biggers list_add(&crypt_info->ci_master_key_link,
603b1c0ec35SEric Biggers &mk->mk_decrypted_inodes);
604b1c0ec35SEric Biggers spin_unlock(&mk->mk_decrypted_inodes_lock);
605b1c0ec35SEric Biggers }
606feed8258SEric Biggers crypt_info = NULL;
607b1c0ec35SEric Biggers }
608b1c0ec35SEric Biggers res = 0;
609feed8258SEric Biggers out:
610d7e7b9afSEric Biggers if (mk) {
611d7e7b9afSEric Biggers up_read(&mk->mk_sem);
612d7e7b9afSEric Biggers fscrypt_put_master_key(mk);
613b1c0ec35SEric Biggers }
614feed8258SEric Biggers put_crypt_info(crypt_info);
615feed8258SEric Biggers return res;
616feed8258SEric Biggers }
617a992b20cSEric Biggers
618a992b20cSEric Biggers /**
619a992b20cSEric Biggers * fscrypt_get_encryption_info() - set up an inode's encryption key
620ac4acb1fSEric Biggers * @inode: the inode to set up the key for. Must be encrypted.
621a14d0b67SEric Biggers * @allow_unsupported: if %true, treat an unsupported encryption policy (or
622a14d0b67SEric Biggers * unrecognized encryption context) the same way as the key
623a14d0b67SEric Biggers * being unavailable, instead of returning an error. Use
624a14d0b67SEric Biggers * %false unless the operation being performed is needed in
625a14d0b67SEric Biggers * order for files (or directories) to be deleted.
626a992b20cSEric Biggers *
627a992b20cSEric Biggers * Set up ->i_crypt_info, if it hasn't already been done.
628a992b20cSEric Biggers *
629a992b20cSEric Biggers * Note: unless ->i_crypt_info is already set, this isn't %GFP_NOFS-safe. So
630a992b20cSEric Biggers * generally this shouldn't be called from within a filesystem transaction.
631a992b20cSEric Biggers *
632a992b20cSEric Biggers * Return: 0 if ->i_crypt_info was set or was already set, *or* if the
633a992b20cSEric Biggers * encryption key is unavailable. (Use fscrypt_has_encryption_key() to
634a992b20cSEric Biggers * distinguish these cases.) Also can return another -errno code.
635a992b20cSEric Biggers */
fscrypt_get_encryption_info(struct inode * inode,bool allow_unsupported)636a14d0b67SEric Biggers int fscrypt_get_encryption_info(struct inode *inode, bool allow_unsupported)
637a992b20cSEric Biggers {
638a992b20cSEric Biggers int res;
639a992b20cSEric Biggers union fscrypt_context ctx;
640a992b20cSEric Biggers union fscrypt_policy policy;
641a992b20cSEric Biggers
642a992b20cSEric Biggers if (fscrypt_has_encryption_key(inode))
643a992b20cSEric Biggers return 0;
644a992b20cSEric Biggers
645a992b20cSEric Biggers res = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx));
646a992b20cSEric Biggers if (res < 0) {
647a14d0b67SEric Biggers if (res == -ERANGE && allow_unsupported)
648a14d0b67SEric Biggers return 0;
649ac4acb1fSEric Biggers fscrypt_warn(inode, "Error %d getting encryption context", res);
650a992b20cSEric Biggers return res;
651a992b20cSEric Biggers }
652a992b20cSEric Biggers
653a992b20cSEric Biggers res = fscrypt_policy_from_context(&policy, &ctx, res);
654a992b20cSEric Biggers if (res) {
655a14d0b67SEric Biggers if (allow_unsupported)
656a14d0b67SEric Biggers return 0;
657a992b20cSEric Biggers fscrypt_warn(inode,
658a992b20cSEric Biggers "Unrecognized or corrupt encryption context");
659a992b20cSEric Biggers return res;
660a992b20cSEric Biggers }
661a992b20cSEric Biggers
662a14d0b67SEric Biggers if (!fscrypt_supported_policy(&policy, inode)) {
663a14d0b67SEric Biggers if (allow_unsupported)
664a14d0b67SEric Biggers return 0;
665a992b20cSEric Biggers return -EINVAL;
666a14d0b67SEric Biggers }
667a992b20cSEric Biggers
668a992b20cSEric Biggers res = fscrypt_setup_encryption_info(inode, &policy,
669a992b20cSEric Biggers fscrypt_context_nonce(&ctx),
670a992b20cSEric Biggers IS_CASEFOLDED(inode) &&
671a992b20cSEric Biggers S_ISDIR(inode->i_mode));
672a14d0b67SEric Biggers
673a14d0b67SEric Biggers if (res == -ENOPKG && allow_unsupported) /* Algorithm unavailable? */
674a14d0b67SEric Biggers res = 0;
675a992b20cSEric Biggers if (res == -ENOKEY)
676a992b20cSEric Biggers res = 0;
677a992b20cSEric Biggers return res;
678a992b20cSEric Biggers }
679feed8258SEric Biggers
680feed8258SEric Biggers /**
681a992b20cSEric Biggers * fscrypt_prepare_new_inode() - prepare to create a new inode in a directory
682a992b20cSEric Biggers * @dir: a possibly-encrypted directory
683a992b20cSEric Biggers * @inode: the new inode. ->i_mode must be set already.
684a992b20cSEric Biggers * ->i_ino doesn't need to be set yet.
685a992b20cSEric Biggers * @encrypt_ret: (output) set to %true if the new inode will be encrypted
686a992b20cSEric Biggers *
687a992b20cSEric Biggers * If the directory is encrypted, set up its ->i_crypt_info in preparation for
688a992b20cSEric Biggers * encrypting the name of the new file. Also, if the new inode will be
689a992b20cSEric Biggers * encrypted, set up its ->i_crypt_info and set *encrypt_ret=true.
690a992b20cSEric Biggers *
691a992b20cSEric Biggers * This isn't %GFP_NOFS-safe, and therefore it should be called before starting
692a992b20cSEric Biggers * any filesystem transaction to create the inode. For this reason, ->i_ino
693a992b20cSEric Biggers * isn't required to be set yet, as the filesystem may not have set it yet.
694a992b20cSEric Biggers *
695a992b20cSEric Biggers * This doesn't persist the new inode's encryption context. That still needs to
696a992b20cSEric Biggers * be done later by calling fscrypt_set_context().
697a992b20cSEric Biggers *
698a992b20cSEric Biggers * Return: 0 on success, -ENOKEY if the encryption key is missing, or another
699a992b20cSEric Biggers * -errno code
700a992b20cSEric Biggers */
fscrypt_prepare_new_inode(struct inode * dir,struct inode * inode,bool * encrypt_ret)701a992b20cSEric Biggers int fscrypt_prepare_new_inode(struct inode *dir, struct inode *inode,
702a992b20cSEric Biggers bool *encrypt_ret)
703a992b20cSEric Biggers {
704ac4acb1fSEric Biggers const union fscrypt_policy *policy;
705a992b20cSEric Biggers u8 nonce[FSCRYPT_FILE_NONCE_SIZE];
706a992b20cSEric Biggers
707ac4acb1fSEric Biggers policy = fscrypt_policy_to_inherit(dir);
708ac4acb1fSEric Biggers if (policy == NULL)
709a992b20cSEric Biggers return 0;
710ac4acb1fSEric Biggers if (IS_ERR(policy))
711ac4acb1fSEric Biggers return PTR_ERR(policy);
712a992b20cSEric Biggers
713a992b20cSEric Biggers if (WARN_ON_ONCE(inode->i_mode == 0))
714a992b20cSEric Biggers return -EINVAL;
715a992b20cSEric Biggers
716a992b20cSEric Biggers /*
717a992b20cSEric Biggers * Only regular files, directories, and symlinks are encrypted.
718a992b20cSEric Biggers * Special files like device nodes and named pipes aren't.
719a992b20cSEric Biggers */
720a992b20cSEric Biggers if (!S_ISREG(inode->i_mode) &&
721a992b20cSEric Biggers !S_ISDIR(inode->i_mode) &&
722a992b20cSEric Biggers !S_ISLNK(inode->i_mode))
723a992b20cSEric Biggers return 0;
724a992b20cSEric Biggers
725a992b20cSEric Biggers *encrypt_ret = true;
726a992b20cSEric Biggers
727a992b20cSEric Biggers get_random_bytes(nonce, FSCRYPT_FILE_NONCE_SIZE);
728ac4acb1fSEric Biggers return fscrypt_setup_encryption_info(inode, policy, nonce,
729a992b20cSEric Biggers IS_CASEFOLDED(dir) &&
730a992b20cSEric Biggers S_ISDIR(inode->i_mode));
731a992b20cSEric Biggers }
732a992b20cSEric Biggers EXPORT_SYMBOL_GPL(fscrypt_prepare_new_inode);
733a992b20cSEric Biggers
734a992b20cSEric Biggers /**
735d2fe9754SEric Biggers * fscrypt_put_encryption_info() - free most of an inode's fscrypt data
736d2fe9754SEric Biggers * @inode: an inode being evicted
737feed8258SEric Biggers *
738feed8258SEric Biggers * Free the inode's fscrypt_info. Filesystems must call this when the inode is
739feed8258SEric Biggers * being evicted. An RCU grace period need not have elapsed yet.
740feed8258SEric Biggers */
fscrypt_put_encryption_info(struct inode * inode)741feed8258SEric Biggers void fscrypt_put_encryption_info(struct inode *inode)
742feed8258SEric Biggers {
743feed8258SEric Biggers put_crypt_info(inode->i_crypt_info);
744feed8258SEric Biggers inode->i_crypt_info = NULL;
745feed8258SEric Biggers }
746feed8258SEric Biggers EXPORT_SYMBOL(fscrypt_put_encryption_info);
747feed8258SEric Biggers
748feed8258SEric Biggers /**
749d2fe9754SEric Biggers * fscrypt_free_inode() - free an inode's fscrypt data requiring RCU delay
750d2fe9754SEric Biggers * @inode: an inode being freed
751feed8258SEric Biggers *
752feed8258SEric Biggers * Free the inode's cached decrypted symlink target, if any. Filesystems must
753feed8258SEric Biggers * call this after an RCU grace period, just before they free the inode.
754feed8258SEric Biggers */
fscrypt_free_inode(struct inode * inode)755feed8258SEric Biggers void fscrypt_free_inode(struct inode *inode)
756feed8258SEric Biggers {
757feed8258SEric Biggers if (IS_ENCRYPTED(inode) && S_ISLNK(inode->i_mode)) {
758feed8258SEric Biggers kfree(inode->i_link);
759feed8258SEric Biggers inode->i_link = NULL;
760feed8258SEric Biggers }
761feed8258SEric Biggers }
762feed8258SEric Biggers EXPORT_SYMBOL(fscrypt_free_inode);
763b1c0ec35SEric Biggers
764b1c0ec35SEric Biggers /**
765d2fe9754SEric Biggers * fscrypt_drop_inode() - check whether the inode's master key has been removed
766d2fe9754SEric Biggers * @inode: an inode being considered for eviction
767b1c0ec35SEric Biggers *
768b1c0ec35SEric Biggers * Filesystems supporting fscrypt must call this from their ->drop_inode()
769b1c0ec35SEric Biggers * method so that encrypted inodes are evicted as soon as they're no longer in
770b1c0ec35SEric Biggers * use and their master key has been removed.
771b1c0ec35SEric Biggers *
772b1c0ec35SEric Biggers * Return: 1 if fscrypt wants the inode to be evicted now, otherwise 0
773b1c0ec35SEric Biggers */
fscrypt_drop_inode(struct inode * inode)774b1c0ec35SEric Biggers int fscrypt_drop_inode(struct inode *inode)
775b1c0ec35SEric Biggers {
776ab673b98SEric Biggers const struct fscrypt_info *ci = fscrypt_get_info(inode);
777b1c0ec35SEric Biggers
778b1c0ec35SEric Biggers /*
779b1c0ec35SEric Biggers * If ci is NULL, then the inode doesn't have an encryption key set up
780b1c0ec35SEric Biggers * so it's irrelevant. If ci_master_key is NULL, then the master key
781b1c0ec35SEric Biggers * was provided via the legacy mechanism of the process-subscribed
782b1c0ec35SEric Biggers * keyrings, so we don't know whether it's been removed or not.
783b1c0ec35SEric Biggers */
784b1c0ec35SEric Biggers if (!ci || !ci->ci_master_key)
785b1c0ec35SEric Biggers return 0;
786b1c0ec35SEric Biggers
787b1c0ec35SEric Biggers /*
7882b4eae95SEric Biggers * With proper, non-racy use of FS_IOC_REMOVE_ENCRYPTION_KEY, all inodes
7892b4eae95SEric Biggers * protected by the key were cleaned by sync_filesystem(). But if
7902b4eae95SEric Biggers * userspace is still using the files, inodes can be dirtied between
7912b4eae95SEric Biggers * then and now. We mustn't lose any writes, so skip dirty inodes here.
7922b4eae95SEric Biggers */
7932b4eae95SEric Biggers if (inode->i_state & I_DIRTY_ALL)
7942b4eae95SEric Biggers return 0;
7952b4eae95SEric Biggers
7962b4eae95SEric Biggers /*
7974a4b8721SEric Biggers * Note: since we aren't holding the key semaphore, the result here can
798b1c0ec35SEric Biggers * immediately become outdated. But there's no correctness problem with
799b1c0ec35SEric Biggers * unnecessarily evicting. Nor is there a correctness problem with not
800b1c0ec35SEric Biggers * evicting while iput() is racing with the key being removed, since
801b1c0ec35SEric Biggers * then the thread removing the key will either evict the inode itself
802b1c0ec35SEric Biggers * or will correctly detect that it wasn't evicted due to the race.
803b1c0ec35SEric Biggers */
804d7e7b9afSEric Biggers return !is_master_key_secret_present(&ci->ci_master_key->mk_secret);
805b1c0ec35SEric Biggers }
806b1c0ec35SEric Biggers EXPORT_SYMBOL_GPL(fscrypt_drop_inode);
807