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Greg Kroah-Hartmanb2441312017-11-01 15:07:57 +01001/* SPDX-License-Identifier: GPL-2.0 */
Theodore Ts'o3325bea2016-11-26 20:32:46 -05002/*
3 * fscrypt_private.h
4 *
5 * Copyright (C) 2015, Google, Inc.
6 *
Eric Biggers3ec4f2a62019-08-04 19:35:45 -07007 * Originally written by Michael Halcrow, Ildar Muslukhov, and Uday Savagaonkar.
8 * Heavily modified since then.
Theodore Ts'o3325bea2016-11-26 20:32:46 -05009 */
10
11#ifndef _FSCRYPT_PRIVATE_H
12#define _FSCRYPT_PRIVATE_H
13
Dave Chinner734f0d22017-10-09 12:15:34 -070014#include <linux/fscrypt.h>
Daniel Rosenbergaa408f82020-01-20 14:31:57 -080015#include <linux/siphash.h>
Daniel Walterb7e7cf72017-06-19 09:27:58 +020016#include <crypto/hash.h>
Theodore Ts'o3325bea2016-11-26 20:32:46 -050017
Eric Biggers22d94f42019-08-04 19:35:46 -070018#define CONST_STRLEN(str) (sizeof(str) - 1)
19
Eric Biggers11b88182018-04-30 15:51:46 -070020#define FS_KEY_DERIVATION_NONCE_SIZE 16
Theodore Ts'occ4e0df2016-11-26 22:05:18 -050021
Eric Biggers22d94f42019-08-04 19:35:46 -070022#define FSCRYPT_MIN_KEY_SIZE 16
23
Eric Biggers5dae4602019-08-04 19:35:47 -070024#define FSCRYPT_CONTEXT_V1 1
25#define FSCRYPT_CONTEXT_V2 2
26
27struct fscrypt_context_v1 {
28 u8 version; /* FSCRYPT_CONTEXT_V1 */
Theodore Ts'occ4e0df2016-11-26 22:05:18 -050029 u8 contents_encryption_mode;
30 u8 filenames_encryption_mode;
31 u8 flags;
Eric Biggers3b6df592019-08-04 19:35:44 -070032 u8 master_key_descriptor[FSCRYPT_KEY_DESCRIPTOR_SIZE];
Theodore Ts'occ4e0df2016-11-26 22:05:18 -050033 u8 nonce[FS_KEY_DERIVATION_NONCE_SIZE];
Eric Biggers5dae4602019-08-04 19:35:47 -070034};
Theodore Ts'occ4e0df2016-11-26 22:05:18 -050035
Eric Biggers5dae4602019-08-04 19:35:47 -070036struct fscrypt_context_v2 {
37 u8 version; /* FSCRYPT_CONTEXT_V2 */
38 u8 contents_encryption_mode;
39 u8 filenames_encryption_mode;
40 u8 flags;
41 u8 __reserved[4];
42 u8 master_key_identifier[FSCRYPT_KEY_IDENTIFIER_SIZE];
43 u8 nonce[FS_KEY_DERIVATION_NONCE_SIZE];
44};
45
46/**
47 * fscrypt_context - the encryption context of an inode
48 *
49 * This is the on-disk equivalent of an fscrypt_policy, stored alongside each
50 * encrypted file usually in a hidden extended attribute. It contains the
51 * fields from the fscrypt_policy, in order to identify the encryption algorithm
52 * and key with which the file is encrypted. It also contains a nonce that was
53 * randomly generated by fscrypt itself; this is used as KDF input or as a tweak
54 * to cause different files to be encrypted differently.
55 */
56union fscrypt_context {
57 u8 version;
58 struct fscrypt_context_v1 v1;
59 struct fscrypt_context_v2 v2;
60};
61
62/*
63 * Return the size expected for the given fscrypt_context based on its version
64 * number, or 0 if the context version is unrecognized.
65 */
66static inline int fscrypt_context_size(const union fscrypt_context *ctx)
67{
68 switch (ctx->version) {
69 case FSCRYPT_CONTEXT_V1:
70 BUILD_BUG_ON(sizeof(ctx->v1) != 28);
71 return sizeof(ctx->v1);
72 case FSCRYPT_CONTEXT_V2:
73 BUILD_BUG_ON(sizeof(ctx->v2) != 40);
74 return sizeof(ctx->v2);
75 }
76 return 0;
77}
78
79#undef fscrypt_policy
80union fscrypt_policy {
81 u8 version;
82 struct fscrypt_policy_v1 v1;
83 struct fscrypt_policy_v2 v2;
84};
85
86/*
87 * Return the size expected for the given fscrypt_policy based on its version
88 * number, or 0 if the policy version is unrecognized.
89 */
90static inline int fscrypt_policy_size(const union fscrypt_policy *policy)
91{
92 switch (policy->version) {
93 case FSCRYPT_POLICY_V1:
94 return sizeof(policy->v1);
95 case FSCRYPT_POLICY_V2:
96 return sizeof(policy->v2);
97 }
98 return 0;
99}
100
101/* Return the contents encryption mode of a valid encryption policy */
102static inline u8
103fscrypt_policy_contents_mode(const union fscrypt_policy *policy)
104{
105 switch (policy->version) {
106 case FSCRYPT_POLICY_V1:
107 return policy->v1.contents_encryption_mode;
108 case FSCRYPT_POLICY_V2:
109 return policy->v2.contents_encryption_mode;
110 }
111 BUG();
112}
113
114/* Return the filenames encryption mode of a valid encryption policy */
115static inline u8
116fscrypt_policy_fnames_mode(const union fscrypt_policy *policy)
117{
118 switch (policy->version) {
119 case FSCRYPT_POLICY_V1:
120 return policy->v1.filenames_encryption_mode;
121 case FSCRYPT_POLICY_V2:
122 return policy->v2.filenames_encryption_mode;
123 }
124 BUG();
125}
126
127/* Return the flags (FSCRYPT_POLICY_FLAG*) of a valid encryption policy */
128static inline u8
129fscrypt_policy_flags(const union fscrypt_policy *policy)
130{
131 switch (policy->version) {
132 case FSCRYPT_POLICY_V1:
133 return policy->v1.flags;
134 case FSCRYPT_POLICY_V2:
135 return policy->v2.flags;
136 }
137 BUG();
138}
139
Eric Biggers0eaab5b2018-01-11 23:30:08 -0500140/**
141 * For encrypted symlinks, the ciphertext length is stored at the beginning
142 * of the string in little-endian format.
143 */
144struct fscrypt_symlink_data {
145 __le16 len;
146 char encrypted_path[1];
147} __packed;
148
Theodore Ts'occ4e0df2016-11-26 22:05:18 -0500149/*
Eric Biggers8094c3c2019-01-06 08:36:21 -0500150 * fscrypt_info - the "encryption key" for an inode
151 *
152 * When an encrypted file's key is made available, an instance of this struct is
153 * allocated and stored in ->i_crypt_info. Once created, it remains until the
154 * inode is evicted.
Theodore Ts'occ4e0df2016-11-26 22:05:18 -0500155 */
156struct fscrypt_info {
Eric Biggers8094c3c2019-01-06 08:36:21 -0500157
158 /* The actual crypto transform used for encryption and decryption */
159 struct crypto_skcipher *ci_ctfm;
160
Eric Biggersb103fb72019-10-24 14:54:36 -0700161 /* True if the key should be freed when this fscrypt_info is freed */
162 bool ci_owns_key;
163
Eric Biggers8094c3c2019-01-06 08:36:21 -0500164 /*
Eric Biggers5dae4602019-08-04 19:35:47 -0700165 * Encryption mode used for this inode. It corresponds to either the
166 * contents or filenames encryption mode, depending on the inode type.
Eric Biggers8094c3c2019-01-06 08:36:21 -0500167 */
168 struct fscrypt_mode *ci_mode;
169
Eric Biggers59dc6a82019-08-04 19:35:44 -0700170 /* Back-pointer to the inode */
171 struct inode *ci_inode;
172
Eric Biggers8094c3c2019-01-06 08:36:21 -0500173 /*
Eric Biggersb1c0ec32019-08-04 19:35:46 -0700174 * The master key with which this inode was unlocked (decrypted). This
175 * will be NULL if the master key was found in a process-subscribed
176 * keyring rather than in the filesystem-level keyring.
177 */
178 struct key *ci_master_key;
179
180 /*
181 * Link in list of inodes that were unlocked with the master key.
182 * Only used when ->ci_master_key is set.
183 */
184 struct list_head ci_master_key_link;
185
186 /*
Eric Biggersa828daa2019-08-04 19:35:45 -0700187 * If non-NULL, then encryption is done using the master key directly
188 * and ci_ctfm will equal ci_direct_key->dk_ctfm.
Eric Biggers8094c3c2019-01-06 08:36:21 -0500189 */
Eric Biggersa828daa2019-08-04 19:35:45 -0700190 struct fscrypt_direct_key *ci_direct_key;
Eric Biggers8094c3c2019-01-06 08:36:21 -0500191
Daniel Rosenbergaa408f82020-01-20 14:31:57 -0800192 /*
193 * This inode's hash key for filenames. This is a 128-bit SipHash-2-4
194 * key. This is only set for directories that use a keyed dirhash over
195 * the plaintext filenames -- currently just casefolded directories.
196 */
197 siphash_key_t ci_dirhash_key;
198 bool ci_dirhash_key_initialized;
199
Eric Biggers5dae4602019-08-04 19:35:47 -0700200 /* The encryption policy used by this inode */
201 union fscrypt_policy ci_policy;
202
203 /* This inode's nonce, copied from the fscrypt_context */
Eric Biggers8094c3c2019-01-06 08:36:21 -0500204 u8 ci_nonce[FS_KEY_DERIVATION_NONCE_SIZE];
Theodore Ts'occ4e0df2016-11-26 22:05:18 -0500205};
206
Richard Weinberger58ae7462016-12-19 12:25:32 +0100207typedef enum {
208 FS_DECRYPT = 0,
209 FS_ENCRYPT,
210} fscrypt_direction_t;
211
Theodore Ts'ob98701df2016-11-26 20:43:09 -0500212/* crypto.c */
Eric Biggerse4de7822018-01-05 10:44:54 -0800213extern struct kmem_cache *fscrypt_info_cachep;
Richard Weinberger58ae7462016-12-19 12:25:32 +0100214extern int fscrypt_initialize(unsigned int cop_flags);
Eric Biggersf47fcbb2019-05-20 09:29:41 -0700215extern int fscrypt_crypt_block(const struct inode *inode,
216 fscrypt_direction_t rw, u64 lblk_num,
217 struct page *src_page, struct page *dest_page,
218 unsigned int len, unsigned int offs,
219 gfp_t gfp_flags);
Eric Biggersd2d07272019-05-20 09:29:39 -0700220extern struct page *fscrypt_alloc_bounce_page(gfp_t gfp_flags);
Theodore Ts'ob98701df2016-11-26 20:43:09 -0500221
Eric Biggers544d08f2018-04-30 15:51:47 -0700222extern void __printf(3, 4) __cold
Eric Biggers886da8b2019-07-24 11:07:58 -0700223fscrypt_msg(const struct inode *inode, const char *level, const char *fmt, ...);
Eric Biggers544d08f2018-04-30 15:51:47 -0700224
Eric Biggers886da8b2019-07-24 11:07:58 -0700225#define fscrypt_warn(inode, fmt, ...) \
226 fscrypt_msg((inode), KERN_WARNING, fmt, ##__VA_ARGS__)
227#define fscrypt_err(inode, fmt, ...) \
228 fscrypt_msg((inode), KERN_ERR, fmt, ##__VA_ARGS__)
Eric Biggers544d08f2018-04-30 15:51:47 -0700229
Eric Biggers8094c3c2019-01-06 08:36:21 -0500230#define FSCRYPT_MAX_IV_SIZE 32
231
232union fscrypt_iv {
233 struct {
234 /* logical block number within the file */
235 __le64 lblk_num;
236
237 /* per-file nonce; only set in DIRECT_KEY mode */
238 u8 nonce[FS_KEY_DERIVATION_NONCE_SIZE];
239 };
240 u8 raw[FSCRYPT_MAX_IV_SIZE];
241};
242
243void fscrypt_generate_iv(union fscrypt_iv *iv, u64 lblk_num,
244 const struct fscrypt_info *ci);
245
Eric Biggers76e81d62018-01-05 10:45:01 -0800246/* fname.c */
Eric Biggers1b3b8272020-01-19 23:17:36 -0800247extern int fscrypt_fname_encrypt(const struct inode *inode,
248 const struct qstr *iname,
249 u8 *out, unsigned int olen);
Eric Biggersb9db0b42018-01-11 23:30:08 -0500250extern bool fscrypt_fname_encrypted_size(const struct inode *inode,
251 u32 orig_len, u32 max_len,
252 u32 *encrypted_len_ret);
Eric Biggers2ebdef62019-12-09 12:43:59 -0800253extern const struct dentry_operations fscrypt_d_ops;
Eric Biggers76e81d62018-01-05 10:45:01 -0800254
Eric Biggersc1144c92019-08-04 19:35:47 -0700255/* hkdf.c */
256
257struct fscrypt_hkdf {
258 struct crypto_shash *hmac_tfm;
259};
260
261extern int fscrypt_init_hkdf(struct fscrypt_hkdf *hkdf, const u8 *master_key,
262 unsigned int master_key_size);
263
Eric Biggers5dae4602019-08-04 19:35:47 -0700264/*
265 * The list of contexts in which fscrypt uses HKDF. These values are used as
266 * the first byte of the HKDF application-specific info string to guarantee that
267 * info strings are never repeated between contexts. This ensures that all HKDF
268 * outputs are unique and cryptographically isolated, i.e. knowledge of one
269 * output doesn't reveal another.
270 */
271#define HKDF_CONTEXT_KEY_IDENTIFIER 1
272#define HKDF_CONTEXT_PER_FILE_KEY 2
Eric Biggersb103fb72019-10-24 14:54:36 -0700273#define HKDF_CONTEXT_DIRECT_KEY 3
274#define HKDF_CONTEXT_IV_INO_LBLK_64_KEY 4
Daniel Rosenbergaa408f82020-01-20 14:31:57 -0800275#define HKDF_CONTEXT_DIRHASH_KEY 5
Eric Biggers5dae4602019-08-04 19:35:47 -0700276
Eric Biggers2a5831b2019-12-09 12:40:54 -0800277extern int fscrypt_hkdf_expand(const struct fscrypt_hkdf *hkdf, u8 context,
Eric Biggersc1144c92019-08-04 19:35:47 -0700278 const u8 *info, unsigned int infolen,
279 u8 *okm, unsigned int okmlen);
280
281extern void fscrypt_destroy_hkdf(struct fscrypt_hkdf *hkdf);
282
Eric Biggers22d94f42019-08-04 19:35:46 -0700283/* keyring.c */
284
285/*
286 * fscrypt_master_key_secret - secret key material of an in-use master key
287 */
288struct fscrypt_master_key_secret {
289
Eric Biggers5dae4602019-08-04 19:35:47 -0700290 /*
291 * For v2 policy keys: HKDF context keyed by this master key.
292 * For v1 policy keys: not set (hkdf.hmac_tfm == NULL).
293 */
294 struct fscrypt_hkdf hkdf;
295
296 /* Size of the raw key in bytes. Set even if ->raw isn't set. */
Eric Biggers22d94f42019-08-04 19:35:46 -0700297 u32 size;
298
Eric Biggers5dae4602019-08-04 19:35:47 -0700299 /* For v1 policy keys: the raw key. Wiped for v2 policy keys. */
Eric Biggers22d94f42019-08-04 19:35:46 -0700300 u8 raw[FSCRYPT_MAX_KEY_SIZE];
301
302} __randomize_layout;
303
304/*
305 * fscrypt_master_key - an in-use master key
306 *
307 * This represents a master encryption key which has been added to the
308 * filesystem and can be used to "unlock" the encrypted files which were
309 * encrypted with it.
310 */
311struct fscrypt_master_key {
312
Eric Biggersb1c0ec32019-08-04 19:35:46 -0700313 /*
314 * The secret key material. After FS_IOC_REMOVE_ENCRYPTION_KEY is
315 * executed, this is wiped and no new inodes can be unlocked with this
316 * key; however, there may still be inodes in ->mk_decrypted_inodes
317 * which could not be evicted. As long as some inodes still remain,
318 * FS_IOC_REMOVE_ENCRYPTION_KEY can be retried, or
319 * FS_IOC_ADD_ENCRYPTION_KEY can add the secret again.
320 *
Eric Biggers23c688b2019-08-04 19:35:47 -0700321 * Locking: protected by key->sem (outer) and mk_secret_sem (inner).
322 * The reason for two locks is that key->sem also protects modifying
323 * mk_users, which ranks it above the semaphore for the keyring key
324 * type, which is in turn above page faults (via keyring_read). But
325 * sometimes filesystems call fscrypt_get_encryption_info() from within
326 * a transaction, which ranks it below page faults. So we need a
327 * separate lock which protects mk_secret but not also mk_users.
Eric Biggersb1c0ec32019-08-04 19:35:46 -0700328 */
Eric Biggers22d94f42019-08-04 19:35:46 -0700329 struct fscrypt_master_key_secret mk_secret;
Eric Biggers23c688b2019-08-04 19:35:47 -0700330 struct rw_semaphore mk_secret_sem;
Eric Biggers22d94f42019-08-04 19:35:46 -0700331
Eric Biggers5dae4602019-08-04 19:35:47 -0700332 /*
333 * For v1 policy keys: an arbitrary key descriptor which was assigned by
334 * userspace (->descriptor).
335 *
336 * For v2 policy keys: a cryptographic hash of this key (->identifier).
337 */
Eric Biggers22d94f42019-08-04 19:35:46 -0700338 struct fscrypt_key_specifier mk_spec;
339
Eric Biggersb1c0ec32019-08-04 19:35:46 -0700340 /*
Eric Biggers23c688b2019-08-04 19:35:47 -0700341 * Keyring which contains a key of type 'key_type_fscrypt_user' for each
342 * user who has added this key. Normally each key will be added by just
343 * one user, but it's possible that multiple users share a key, and in
344 * that case we need to keep track of those users so that one user can't
345 * remove the key before the others want it removed too.
346 *
347 * This is NULL for v1 policy keys; those can only be added by root.
348 *
349 * Locking: in addition to this keyrings own semaphore, this is
350 * protected by the master key's key->sem, so we can do atomic
351 * search+insert. It can also be searched without taking any locks, but
352 * in that case the returned key may have already been removed.
353 */
354 struct key *mk_users;
355
356 /*
Eric Biggersb1c0ec32019-08-04 19:35:46 -0700357 * Length of ->mk_decrypted_inodes, plus one if mk_secret is present.
358 * Once this goes to 0, the master key is removed from ->s_master_keys.
359 * The 'struct fscrypt_master_key' will continue to live as long as the
360 * 'struct key' whose payload it is, but we won't let this reference
361 * count rise again.
362 */
363 refcount_t mk_refcount;
364
365 /*
366 * List of inodes that were unlocked using this key. This allows the
367 * inodes to be evicted efficiently if the key is removed.
368 */
369 struct list_head mk_decrypted_inodes;
370 spinlock_t mk_decrypted_inodes_lock;
371
Eric Biggersb103fb72019-10-24 14:54:36 -0700372 /* Crypto API transforms for DIRECT_KEY policies, allocated on-demand */
373 struct crypto_skcipher *mk_direct_tfms[__FSCRYPT_MODE_MAX + 1];
374
375 /*
376 * Crypto API transforms for filesystem-layer implementation of
377 * IV_INO_LBLK_64 policies, allocated on-demand.
378 */
379 struct crypto_skcipher *mk_iv_ino_lblk_64_tfms[__FSCRYPT_MODE_MAX + 1];
Eric Biggers5dae4602019-08-04 19:35:47 -0700380
Eric Biggers22d94f42019-08-04 19:35:46 -0700381} __randomize_layout;
382
Eric Biggersb1c0ec32019-08-04 19:35:46 -0700383static inline bool
384is_master_key_secret_present(const struct fscrypt_master_key_secret *secret)
385{
386 /*
387 * The READ_ONCE() is only necessary for fscrypt_drop_inode() and
388 * fscrypt_key_describe(). These run in atomic context, so they can't
Eric Biggers23c688b2019-08-04 19:35:47 -0700389 * take ->mk_secret_sem and thus 'secret' can change concurrently which
390 * would be a data race. But they only need to know whether the secret
391 * *was* present at the time of check, so READ_ONCE() suffices.
Eric Biggersb1c0ec32019-08-04 19:35:46 -0700392 */
393 return READ_ONCE(secret->size) != 0;
394}
395
Eric Biggers22d94f42019-08-04 19:35:46 -0700396static inline const char *master_key_spec_type(
397 const struct fscrypt_key_specifier *spec)
398{
399 switch (spec->type) {
400 case FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR:
401 return "descriptor";
Eric Biggers5dae4602019-08-04 19:35:47 -0700402 case FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER:
403 return "identifier";
Eric Biggers22d94f42019-08-04 19:35:46 -0700404 }
405 return "[unknown]";
406}
407
408static inline int master_key_spec_len(const struct fscrypt_key_specifier *spec)
409{
410 switch (spec->type) {
411 case FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR:
412 return FSCRYPT_KEY_DESCRIPTOR_SIZE;
Eric Biggers5dae4602019-08-04 19:35:47 -0700413 case FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER:
414 return FSCRYPT_KEY_IDENTIFIER_SIZE;
Eric Biggers22d94f42019-08-04 19:35:46 -0700415 }
416 return 0;
417}
418
419extern struct key *
420fscrypt_find_master_key(struct super_block *sb,
421 const struct fscrypt_key_specifier *mk_spec);
422
Eric Biggers5ab71892019-08-04 19:35:48 -0700423extern int fscrypt_verify_key_added(struct super_block *sb,
424 const u8 identifier[FSCRYPT_KEY_IDENTIFIER_SIZE]);
425
Eric Biggers22d94f42019-08-04 19:35:46 -0700426extern int __init fscrypt_init_keyring(void);
427
Eric Biggersfeed8252019-08-04 19:35:45 -0700428/* keysetup.c */
Eric Biggers8094c3c2019-01-06 08:36:21 -0500429
430struct fscrypt_mode {
431 const char *friendly_name;
432 const char *cipher_str;
433 int keysize;
434 int ivsize;
Eric Biggersff73c2c2019-10-21 13:49:03 -0700435 int logged_impl_name;
Eric Biggers8094c3c2019-01-06 08:36:21 -0500436};
437
Eric Biggers85af90e2019-12-09 13:18:27 -0800438extern struct fscrypt_mode fscrypt_modes[];
Eric Biggers3ec4f2a62019-08-04 19:35:45 -0700439
Eric Biggers0109ce762019-08-04 19:35:45 -0700440extern struct crypto_skcipher *
441fscrypt_allocate_skcipher(struct fscrypt_mode *mode, const u8 *raw_key,
442 const struct inode *inode);
443
444extern int fscrypt_set_derived_key(struct fscrypt_info *ci,
445 const u8 *derived_key);
446
Daniel Rosenbergaa408f82020-01-20 14:31:57 -0800447extern int fscrypt_derive_dirhash_key(struct fscrypt_info *ci,
448 const struct fscrypt_master_key *mk);
449
Eric Biggers0109ce762019-08-04 19:35:45 -0700450/* keysetup_v1.c */
451
452extern void fscrypt_put_direct_key(struct fscrypt_direct_key *dk);
453
454extern int fscrypt_setup_v1_file_key(struct fscrypt_info *ci,
455 const u8 *raw_master_key);
456
457extern int fscrypt_setup_v1_file_key_via_subscribed_keyrings(
458 struct fscrypt_info *ci);
Eric Biggers5dae4602019-08-04 19:35:47 -0700459/* policy.c */
460
461extern bool fscrypt_policies_equal(const union fscrypt_policy *policy1,
462 const union fscrypt_policy *policy2);
463extern bool fscrypt_supported_policy(const union fscrypt_policy *policy_u,
464 const struct inode *inode);
465extern int fscrypt_policy_from_context(union fscrypt_policy *policy_u,
466 const union fscrypt_context *ctx_u,
467 int ctx_size);
Eric Biggers0109ce762019-08-04 19:35:45 -0700468
Theodore Ts'o3325bea2016-11-26 20:32:46 -0500469#endif /* _FSCRYPT_PRIVATE_H */