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1/* SPDX-License-Identifier: GPL-2.0 */
2/*
3 * fscrypt_private.h
4 *
5 * Copyright (C) 2015, Google, Inc.
6 *
7 * Originally written by Michael Halcrow, Ildar Muslukhov, and Uday Savagaonkar.
8 * Heavily modified since then.
9 */
10
11#ifndef _FSCRYPT_PRIVATE_H
12#define _FSCRYPT_PRIVATE_H
13
14#include <linux/fscrypt.h>
15#include <crypto/hash.h>
16
17#define CONST_STRLEN(str) (sizeof(str) - 1)
18
19#define FS_KEY_DERIVATION_NONCE_SIZE 16
20
21#define FSCRYPT_MIN_KEY_SIZE 16
22
23#define FSCRYPT_CONTEXT_V1 1
24#define FSCRYPT_CONTEXT_V2 2
25
26struct fscrypt_context_v1 {
27 u8 version; /* FSCRYPT_CONTEXT_V1 */
28 u8 contents_encryption_mode;
29 u8 filenames_encryption_mode;
30 u8 flags;
31 u8 master_key_descriptor[FSCRYPT_KEY_DESCRIPTOR_SIZE];
32 u8 nonce[FS_KEY_DERIVATION_NONCE_SIZE];
33};
34
35struct fscrypt_context_v2 {
36 u8 version; /* FSCRYPT_CONTEXT_V2 */
37 u8 contents_encryption_mode;
38 u8 filenames_encryption_mode;
39 u8 flags;
40 u8 __reserved[4];
41 u8 master_key_identifier[FSCRYPT_KEY_IDENTIFIER_SIZE];
42 u8 nonce[FS_KEY_DERIVATION_NONCE_SIZE];
43};
44
45/**
46 * fscrypt_context - the encryption context of an inode
47 *
48 * This is the on-disk equivalent of an fscrypt_policy, stored alongside each
49 * encrypted file usually in a hidden extended attribute. It contains the
50 * fields from the fscrypt_policy, in order to identify the encryption algorithm
51 * and key with which the file is encrypted. It also contains a nonce that was
52 * randomly generated by fscrypt itself; this is used as KDF input or as a tweak
53 * to cause different files to be encrypted differently.
54 */
55union fscrypt_context {
56 u8 version;
57 struct fscrypt_context_v1 v1;
58 struct fscrypt_context_v2 v2;
59};
60
61/*
62 * Return the size expected for the given fscrypt_context based on its version
63 * number, or 0 if the context version is unrecognized.
64 */
65static inline int fscrypt_context_size(const union fscrypt_context *ctx)
66{
67 switch (ctx->version) {
68 case FSCRYPT_CONTEXT_V1:
69 BUILD_BUG_ON(sizeof(ctx->v1) != 28);
70 return sizeof(ctx->v1);
71 case FSCRYPT_CONTEXT_V2:
72 BUILD_BUG_ON(sizeof(ctx->v2) != 40);
73 return sizeof(ctx->v2);
74 }
75 return 0;
76}
77
78#undef fscrypt_policy
79union fscrypt_policy {
80 u8 version;
81 struct fscrypt_policy_v1 v1;
82 struct fscrypt_policy_v2 v2;
83};
84
85/*
86 * Return the size expected for the given fscrypt_policy based on its version
87 * number, or 0 if the policy version is unrecognized.
88 */
89static inline int fscrypt_policy_size(const union fscrypt_policy *policy)
90{
91 switch (policy->version) {
92 case FSCRYPT_POLICY_V1:
93 return sizeof(policy->v1);
94 case FSCRYPT_POLICY_V2:
95 return sizeof(policy->v2);
96 }
97 return 0;
98}
99
100/* Return the contents encryption mode of a valid encryption policy */
101static inline u8
102fscrypt_policy_contents_mode(const union fscrypt_policy *policy)
103{
104 switch (policy->version) {
105 case FSCRYPT_POLICY_V1:
106 return policy->v1.contents_encryption_mode;
107 case FSCRYPT_POLICY_V2:
108 return policy->v2.contents_encryption_mode;
109 }
110 BUG();
111}
112
113/* Return the filenames encryption mode of a valid encryption policy */
114static inline u8
115fscrypt_policy_fnames_mode(const union fscrypt_policy *policy)
116{
117 switch (policy->version) {
118 case FSCRYPT_POLICY_V1:
119 return policy->v1.filenames_encryption_mode;
120 case FSCRYPT_POLICY_V2:
121 return policy->v2.filenames_encryption_mode;
122 }
123 BUG();
124}
125
126/* Return the flags (FSCRYPT_POLICY_FLAG*) of a valid encryption policy */
127static inline u8
128fscrypt_policy_flags(const union fscrypt_policy *policy)
129{
130 switch (policy->version) {
131 case FSCRYPT_POLICY_V1:
132 return policy->v1.flags;
133 case FSCRYPT_POLICY_V2:
134 return policy->v2.flags;
135 }
136 BUG();
137}
138
139static inline bool
140fscrypt_is_direct_key_policy(const union fscrypt_policy *policy)
141{
142 return fscrypt_policy_flags(policy) & FSCRYPT_POLICY_FLAG_DIRECT_KEY;
143}
144
145/**
146 * For encrypted symlinks, the ciphertext length is stored at the beginning
147 * of the string in little-endian format.
148 */
149struct fscrypt_symlink_data {
150 __le16 len;
151 char encrypted_path[1];
152} __packed;
153
154/*
155 * fscrypt_info - the "encryption key" for an inode
156 *
157 * When an encrypted file's key is made available, an instance of this struct is
158 * allocated and stored in ->i_crypt_info. Once created, it remains until the
159 * inode is evicted.
160 */
161struct fscrypt_info {
162
163 /* The actual crypto transform used for encryption and decryption */
164 struct crypto_skcipher *ci_ctfm;
165
166 /*
167 * Cipher for ESSIV IV generation. Only set for CBC contents
168 * encryption, otherwise is NULL.
169 */
170 struct crypto_cipher *ci_essiv_tfm;
171
172 /*
173 * Encryption mode used for this inode. It corresponds to either the
174 * contents or filenames encryption mode, depending on the inode type.
175 */
176 struct fscrypt_mode *ci_mode;
177
178 /* Back-pointer to the inode */
179 struct inode *ci_inode;
180
181 /*
182 * The master key with which this inode was unlocked (decrypted). This
183 * will be NULL if the master key was found in a process-subscribed
184 * keyring rather than in the filesystem-level keyring.
185 */
186 struct key *ci_master_key;
187
188 /*
189 * Link in list of inodes that were unlocked with the master key.
190 * Only used when ->ci_master_key is set.
191 */
192 struct list_head ci_master_key_link;
193
194 /*
195 * If non-NULL, then encryption is done using the master key directly
196 * and ci_ctfm will equal ci_direct_key->dk_ctfm.
197 */
198 struct fscrypt_direct_key *ci_direct_key;
199
200 /* The encryption policy used by this inode */
201 union fscrypt_policy ci_policy;
202
203 /* This inode's nonce, copied from the fscrypt_context */
204 u8 ci_nonce[FS_KEY_DERIVATION_NONCE_SIZE];
205};
206
207typedef enum {
208 FS_DECRYPT = 0,
209 FS_ENCRYPT,
210} fscrypt_direction_t;
211
212#define FS_CTX_REQUIRES_FREE_ENCRYPT_FL 0x00000001
213
214static inline bool fscrypt_valid_enc_modes(u32 contents_mode,
215 u32 filenames_mode)
216{
217 if (contents_mode == FSCRYPT_MODE_AES_128_CBC &&
218 filenames_mode == FSCRYPT_MODE_AES_128_CTS)
219 return true;
220
221 if (contents_mode == FSCRYPT_MODE_AES_256_XTS &&
222 filenames_mode == FSCRYPT_MODE_AES_256_CTS)
223 return true;
224
225 if (contents_mode == FSCRYPT_MODE_ADIANTUM &&
226 filenames_mode == FSCRYPT_MODE_ADIANTUM)
227 return true;
228
229 return false;
230}
231
232/* crypto.c */
233extern struct kmem_cache *fscrypt_info_cachep;
234extern int fscrypt_initialize(unsigned int cop_flags);
235extern int fscrypt_crypt_block(const struct inode *inode,
236 fscrypt_direction_t rw, u64 lblk_num,
237 struct page *src_page, struct page *dest_page,
238 unsigned int len, unsigned int offs,
239 gfp_t gfp_flags);
240extern struct page *fscrypt_alloc_bounce_page(gfp_t gfp_flags);
241extern const struct dentry_operations fscrypt_d_ops;
242
243extern void __printf(3, 4) __cold
244fscrypt_msg(const struct inode *inode, const char *level, const char *fmt, ...);
245
246#define fscrypt_warn(inode, fmt, ...) \
247 fscrypt_msg((inode), KERN_WARNING, fmt, ##__VA_ARGS__)
248#define fscrypt_err(inode, fmt, ...) \
249 fscrypt_msg((inode), KERN_ERR, fmt, ##__VA_ARGS__)
250
251#define FSCRYPT_MAX_IV_SIZE 32
252
253union fscrypt_iv {
254 struct {
255 /* logical block number within the file */
256 __le64 lblk_num;
257
258 /* per-file nonce; only set in DIRECT_KEY mode */
259 u8 nonce[FS_KEY_DERIVATION_NONCE_SIZE];
260 };
261 u8 raw[FSCRYPT_MAX_IV_SIZE];
262};
263
264void fscrypt_generate_iv(union fscrypt_iv *iv, u64 lblk_num,
265 const struct fscrypt_info *ci);
266
267/* fname.c */
268extern int fname_encrypt(struct inode *inode, const struct qstr *iname,
269 u8 *out, unsigned int olen);
270extern bool fscrypt_fname_encrypted_size(const struct inode *inode,
271 u32 orig_len, u32 max_len,
272 u32 *encrypted_len_ret);
273
274/* hkdf.c */
275
276struct fscrypt_hkdf {
277 struct crypto_shash *hmac_tfm;
278};
279
280extern int fscrypt_init_hkdf(struct fscrypt_hkdf *hkdf, const u8 *master_key,
281 unsigned int master_key_size);
282
283/*
284 * The list of contexts in which fscrypt uses HKDF. These values are used as
285 * the first byte of the HKDF application-specific info string to guarantee that
286 * info strings are never repeated between contexts. This ensures that all HKDF
287 * outputs are unique and cryptographically isolated, i.e. knowledge of one
288 * output doesn't reveal another.
289 */
290#define HKDF_CONTEXT_KEY_IDENTIFIER 1
291#define HKDF_CONTEXT_PER_FILE_KEY 2
292#define HKDF_CONTEXT_PER_MODE_KEY 3
293
294extern int fscrypt_hkdf_expand(struct fscrypt_hkdf *hkdf, u8 context,
295 const u8 *info, unsigned int infolen,
296 u8 *okm, unsigned int okmlen);
297
298extern void fscrypt_destroy_hkdf(struct fscrypt_hkdf *hkdf);
299
300/* keyring.c */
301
302/*
303 * fscrypt_master_key_secret - secret key material of an in-use master key
304 */
305struct fscrypt_master_key_secret {
306
307 /*
308 * For v2 policy keys: HKDF context keyed by this master key.
309 * For v1 policy keys: not set (hkdf.hmac_tfm == NULL).
310 */
311 struct fscrypt_hkdf hkdf;
312
313 /* Size of the raw key in bytes. Set even if ->raw isn't set. */
314 u32 size;
315
316 /* For v1 policy keys: the raw key. Wiped for v2 policy keys. */
317 u8 raw[FSCRYPT_MAX_KEY_SIZE];
318
319} __randomize_layout;
320
321/*
322 * fscrypt_master_key - an in-use master key
323 *
324 * This represents a master encryption key which has been added to the
325 * filesystem and can be used to "unlock" the encrypted files which were
326 * encrypted with it.
327 */
328struct fscrypt_master_key {
329
330 /*
331 * The secret key material. After FS_IOC_REMOVE_ENCRYPTION_KEY is
332 * executed, this is wiped and no new inodes can be unlocked with this
333 * key; however, there may still be inodes in ->mk_decrypted_inodes
334 * which could not be evicted. As long as some inodes still remain,
335 * FS_IOC_REMOVE_ENCRYPTION_KEY can be retried, or
336 * FS_IOC_ADD_ENCRYPTION_KEY can add the secret again.
337 *
338 * Locking: protected by key->sem (outer) and mk_secret_sem (inner).
339 * The reason for two locks is that key->sem also protects modifying
340 * mk_users, which ranks it above the semaphore for the keyring key
341 * type, which is in turn above page faults (via keyring_read). But
342 * sometimes filesystems call fscrypt_get_encryption_info() from within
343 * a transaction, which ranks it below page faults. So we need a
344 * separate lock which protects mk_secret but not also mk_users.
345 */
346 struct fscrypt_master_key_secret mk_secret;
347 struct rw_semaphore mk_secret_sem;
348
349 /*
350 * For v1 policy keys: an arbitrary key descriptor which was assigned by
351 * userspace (->descriptor).
352 *
353 * For v2 policy keys: a cryptographic hash of this key (->identifier).
354 */
355 struct fscrypt_key_specifier mk_spec;
356
357 /*
358 * Keyring which contains a key of type 'key_type_fscrypt_user' for each
359 * user who has added this key. Normally each key will be added by just
360 * one user, but it's possible that multiple users share a key, and in
361 * that case we need to keep track of those users so that one user can't
362 * remove the key before the others want it removed too.
363 *
364 * This is NULL for v1 policy keys; those can only be added by root.
365 *
366 * Locking: in addition to this keyrings own semaphore, this is
367 * protected by the master key's key->sem, so we can do atomic
368 * search+insert. It can also be searched without taking any locks, but
369 * in that case the returned key may have already been removed.
370 */
371 struct key *mk_users;
372
373 /*
374 * Length of ->mk_decrypted_inodes, plus one if mk_secret is present.
375 * Once this goes to 0, the master key is removed from ->s_master_keys.
376 * The 'struct fscrypt_master_key' will continue to live as long as the
377 * 'struct key' whose payload it is, but we won't let this reference
378 * count rise again.
379 */
380 refcount_t mk_refcount;
381
382 /*
383 * List of inodes that were unlocked using this key. This allows the
384 * inodes to be evicted efficiently if the key is removed.
385 */
386 struct list_head mk_decrypted_inodes;
387 spinlock_t mk_decrypted_inodes_lock;
388
389 /* Per-mode tfms for DIRECT_KEY policies, allocated on-demand */
390 struct crypto_skcipher *mk_mode_keys[__FSCRYPT_MODE_MAX + 1];
391
392} __randomize_layout;
393
394static inline bool
395is_master_key_secret_present(const struct fscrypt_master_key_secret *secret)
396{
397 /*
398 * The READ_ONCE() is only necessary for fscrypt_drop_inode() and
399 * fscrypt_key_describe(). These run in atomic context, so they can't
400 * take ->mk_secret_sem and thus 'secret' can change concurrently which
401 * would be a data race. But they only need to know whether the secret
402 * *was* present at the time of check, so READ_ONCE() suffices.
403 */
404 return READ_ONCE(secret->size) != 0;
405}
406
407static inline const char *master_key_spec_type(
408 const struct fscrypt_key_specifier *spec)
409{
410 switch (spec->type) {
411 case FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR:
412 return "descriptor";
413 case FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER:
414 return "identifier";
415 }
416 return "[unknown]";
417}
418
419static inline int master_key_spec_len(const struct fscrypt_key_specifier *spec)
420{
421 switch (spec->type) {
422 case FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR:
423 return FSCRYPT_KEY_DESCRIPTOR_SIZE;
424 case FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER:
425 return FSCRYPT_KEY_IDENTIFIER_SIZE;
426 }
427 return 0;
428}
429
430extern struct key *
431fscrypt_find_master_key(struct super_block *sb,
432 const struct fscrypt_key_specifier *mk_spec);
433
434extern int fscrypt_verify_key_added(struct super_block *sb,
435 const u8 identifier[FSCRYPT_KEY_IDENTIFIER_SIZE]);
436
437extern int __init fscrypt_init_keyring(void);
438
439/* keysetup.c */
440
441struct fscrypt_mode {
442 const char *friendly_name;
443 const char *cipher_str;
444 int keysize;
445 int ivsize;
446 bool logged_impl_name;
447 bool needs_essiv;
448};
449
450static inline bool
451fscrypt_mode_supports_direct_key(const struct fscrypt_mode *mode)
452{
453 return mode->ivsize >= offsetofend(union fscrypt_iv, nonce);
454}
455
456extern struct crypto_skcipher *
457fscrypt_allocate_skcipher(struct fscrypt_mode *mode, const u8 *raw_key,
458 const struct inode *inode);
459
460extern int fscrypt_set_derived_key(struct fscrypt_info *ci,
461 const u8 *derived_key);
462
463/* keysetup_v1.c */
464
465extern void fscrypt_put_direct_key(struct fscrypt_direct_key *dk);
466
467extern int fscrypt_setup_v1_file_key(struct fscrypt_info *ci,
468 const u8 *raw_master_key);
469
470extern int fscrypt_setup_v1_file_key_via_subscribed_keyrings(
471 struct fscrypt_info *ci);
472/* policy.c */
473
474extern bool fscrypt_policies_equal(const union fscrypt_policy *policy1,
475 const union fscrypt_policy *policy2);
476extern bool fscrypt_supported_policy(const union fscrypt_policy *policy_u,
477 const struct inode *inode);
478extern int fscrypt_policy_from_context(union fscrypt_policy *policy_u,
479 const union fscrypt_context *ctx_u,
480 int ctx_size);
481
482#endif /* _FSCRYPT_PRIVATE_H */
1/* SPDX-License-Identifier: GPL-2.0 */
2/*
3 * fscrypt_private.h
4 *
5 * Copyright (C) 2015, Google, Inc.
6 *
7 * Originally written by Michael Halcrow, Ildar Muslukhov, and Uday Savagaonkar.
8 * Heavily modified since then.
9 */
10
11#ifndef _FSCRYPT_PRIVATE_H
12#define _FSCRYPT_PRIVATE_H
13
14#include <linux/fscrypt.h>
15#include <linux/siphash.h>
16#include <crypto/hash.h>
17#include <linux/blk-crypto.h>
18
19#define CONST_STRLEN(str) (sizeof(str) - 1)
20
21#define FSCRYPT_FILE_NONCE_SIZE 16
22
23/*
24 * Minimum size of an fscrypt master key. Note: a longer key will be required
25 * if ciphers with a 256-bit security strength are used. This is just the
26 * absolute minimum, which applies when only 128-bit encryption is used.
27 */
28#define FSCRYPT_MIN_KEY_SIZE 16
29
30#define FSCRYPT_CONTEXT_V1 1
31#define FSCRYPT_CONTEXT_V2 2
32
33/* Keep this in sync with include/uapi/linux/fscrypt.h */
34#define FSCRYPT_MODE_MAX FSCRYPT_MODE_AES_256_HCTR2
35
36struct fscrypt_context_v1 {
37 u8 version; /* FSCRYPT_CONTEXT_V1 */
38 u8 contents_encryption_mode;
39 u8 filenames_encryption_mode;
40 u8 flags;
41 u8 master_key_descriptor[FSCRYPT_KEY_DESCRIPTOR_SIZE];
42 u8 nonce[FSCRYPT_FILE_NONCE_SIZE];
43};
44
45struct fscrypt_context_v2 {
46 u8 version; /* FSCRYPT_CONTEXT_V2 */
47 u8 contents_encryption_mode;
48 u8 filenames_encryption_mode;
49 u8 flags;
50 u8 log2_data_unit_size;
51 u8 __reserved[3];
52 u8 master_key_identifier[FSCRYPT_KEY_IDENTIFIER_SIZE];
53 u8 nonce[FSCRYPT_FILE_NONCE_SIZE];
54};
55
56/*
57 * fscrypt_context - the encryption context of an inode
58 *
59 * This is the on-disk equivalent of an fscrypt_policy, stored alongside each
60 * encrypted file usually in a hidden extended attribute. It contains the
61 * fields from the fscrypt_policy, in order to identify the encryption algorithm
62 * and key with which the file is encrypted. It also contains a nonce that was
63 * randomly generated by fscrypt itself; this is used as KDF input or as a tweak
64 * to cause different files to be encrypted differently.
65 */
66union fscrypt_context {
67 u8 version;
68 struct fscrypt_context_v1 v1;
69 struct fscrypt_context_v2 v2;
70};
71
72/*
73 * Return the size expected for the given fscrypt_context based on its version
74 * number, or 0 if the context version is unrecognized.
75 */
76static inline int fscrypt_context_size(const union fscrypt_context *ctx)
77{
78 switch (ctx->version) {
79 case FSCRYPT_CONTEXT_V1:
80 BUILD_BUG_ON(sizeof(ctx->v1) != 28);
81 return sizeof(ctx->v1);
82 case FSCRYPT_CONTEXT_V2:
83 BUILD_BUG_ON(sizeof(ctx->v2) != 40);
84 return sizeof(ctx->v2);
85 }
86 return 0;
87}
88
89/* Check whether an fscrypt_context has a recognized version number and size */
90static inline bool fscrypt_context_is_valid(const union fscrypt_context *ctx,
91 int ctx_size)
92{
93 return ctx_size >= 1 && ctx_size == fscrypt_context_size(ctx);
94}
95
96/* Retrieve the context's nonce, assuming the context was already validated */
97static inline const u8 *fscrypt_context_nonce(const union fscrypt_context *ctx)
98{
99 switch (ctx->version) {
100 case FSCRYPT_CONTEXT_V1:
101 return ctx->v1.nonce;
102 case FSCRYPT_CONTEXT_V2:
103 return ctx->v2.nonce;
104 }
105 WARN_ON_ONCE(1);
106 return NULL;
107}
108
109union fscrypt_policy {
110 u8 version;
111 struct fscrypt_policy_v1 v1;
112 struct fscrypt_policy_v2 v2;
113};
114
115/*
116 * Return the size expected for the given fscrypt_policy based on its version
117 * number, or 0 if the policy version is unrecognized.
118 */
119static inline int fscrypt_policy_size(const union fscrypt_policy *policy)
120{
121 switch (policy->version) {
122 case FSCRYPT_POLICY_V1:
123 return sizeof(policy->v1);
124 case FSCRYPT_POLICY_V2:
125 return sizeof(policy->v2);
126 }
127 return 0;
128}
129
130/* Return the contents encryption mode of a valid encryption policy */
131static inline u8
132fscrypt_policy_contents_mode(const union fscrypt_policy *policy)
133{
134 switch (policy->version) {
135 case FSCRYPT_POLICY_V1:
136 return policy->v1.contents_encryption_mode;
137 case FSCRYPT_POLICY_V2:
138 return policy->v2.contents_encryption_mode;
139 }
140 BUG();
141}
142
143/* Return the filenames encryption mode of a valid encryption policy */
144static inline u8
145fscrypt_policy_fnames_mode(const union fscrypt_policy *policy)
146{
147 switch (policy->version) {
148 case FSCRYPT_POLICY_V1:
149 return policy->v1.filenames_encryption_mode;
150 case FSCRYPT_POLICY_V2:
151 return policy->v2.filenames_encryption_mode;
152 }
153 BUG();
154}
155
156/* Return the flags (FSCRYPT_POLICY_FLAG*) of a valid encryption policy */
157static inline u8
158fscrypt_policy_flags(const union fscrypt_policy *policy)
159{
160 switch (policy->version) {
161 case FSCRYPT_POLICY_V1:
162 return policy->v1.flags;
163 case FSCRYPT_POLICY_V2:
164 return policy->v2.flags;
165 }
166 BUG();
167}
168
169static inline int
170fscrypt_policy_v2_du_bits(const struct fscrypt_policy_v2 *policy,
171 const struct inode *inode)
172{
173 return policy->log2_data_unit_size ?: inode->i_blkbits;
174}
175
176static inline int
177fscrypt_policy_du_bits(const union fscrypt_policy *policy,
178 const struct inode *inode)
179{
180 switch (policy->version) {
181 case FSCRYPT_POLICY_V1:
182 return inode->i_blkbits;
183 case FSCRYPT_POLICY_V2:
184 return fscrypt_policy_v2_du_bits(&policy->v2, inode);
185 }
186 BUG();
187}
188
189/*
190 * For encrypted symlinks, the ciphertext length is stored at the beginning
191 * of the string in little-endian format.
192 */
193struct fscrypt_symlink_data {
194 __le16 len;
195 char encrypted_path[];
196} __packed;
197
198/**
199 * struct fscrypt_prepared_key - a key prepared for actual encryption/decryption
200 * @tfm: crypto API transform object
201 * @blk_key: key for blk-crypto
202 *
203 * Normally only one of the fields will be non-NULL.
204 */
205struct fscrypt_prepared_key {
206 struct crypto_skcipher *tfm;
207#ifdef CONFIG_FS_ENCRYPTION_INLINE_CRYPT
208 struct blk_crypto_key *blk_key;
209#endif
210};
211
212/*
213 * fscrypt_inode_info - the "encryption key" for an inode
214 *
215 * When an encrypted file's key is made available, an instance of this struct is
216 * allocated and stored in ->i_crypt_info. Once created, it remains until the
217 * inode is evicted.
218 */
219struct fscrypt_inode_info {
220
221 /* The key in a form prepared for actual encryption/decryption */
222 struct fscrypt_prepared_key ci_enc_key;
223
224 /* True if ci_enc_key should be freed when this struct is freed */
225 u8 ci_owns_key : 1;
226
227#ifdef CONFIG_FS_ENCRYPTION_INLINE_CRYPT
228 /*
229 * True if this inode will use inline encryption (blk-crypto) instead of
230 * the traditional filesystem-layer encryption.
231 */
232 u8 ci_inlinecrypt : 1;
233#endif
234
235 /* True if ci_dirhash_key is initialized */
236 u8 ci_dirhash_key_initialized : 1;
237
238 /*
239 * log2 of the data unit size (granularity of contents encryption) of
240 * this file. This is computable from ci_policy and ci_inode but is
241 * cached here for efficiency. Only used for regular files.
242 */
243 u8 ci_data_unit_bits;
244
245 /* Cached value: log2 of number of data units per FS block */
246 u8 ci_data_units_per_block_bits;
247
248 /* Hashed inode number. Only set for IV_INO_LBLK_32 */
249 u32 ci_hashed_ino;
250
251 /*
252 * Encryption mode used for this inode. It corresponds to either the
253 * contents or filenames encryption mode, depending on the inode type.
254 */
255 struct fscrypt_mode *ci_mode;
256
257 /* Back-pointer to the inode */
258 struct inode *ci_inode;
259
260 /*
261 * The master key with which this inode was unlocked (decrypted). This
262 * will be NULL if the master key was found in a process-subscribed
263 * keyring rather than in the filesystem-level keyring.
264 */
265 struct fscrypt_master_key *ci_master_key;
266
267 /*
268 * Link in list of inodes that were unlocked with the master key.
269 * Only used when ->ci_master_key is set.
270 */
271 struct list_head ci_master_key_link;
272
273 /*
274 * If non-NULL, then encryption is done using the master key directly
275 * and ci_enc_key will equal ci_direct_key->dk_key.
276 */
277 struct fscrypt_direct_key *ci_direct_key;
278
279 /*
280 * This inode's hash key for filenames. This is a 128-bit SipHash-2-4
281 * key. This is only set for directories that use a keyed dirhash over
282 * the plaintext filenames -- currently just casefolded directories.
283 */
284 siphash_key_t ci_dirhash_key;
285
286 /* The encryption policy used by this inode */
287 union fscrypt_policy ci_policy;
288
289 /* This inode's nonce, copied from the fscrypt_context */
290 u8 ci_nonce[FSCRYPT_FILE_NONCE_SIZE];
291};
292
293typedef enum {
294 FS_DECRYPT = 0,
295 FS_ENCRYPT,
296} fscrypt_direction_t;
297
298/* crypto.c */
299extern struct kmem_cache *fscrypt_inode_info_cachep;
300int fscrypt_initialize(struct super_block *sb);
301int fscrypt_crypt_data_unit(const struct fscrypt_inode_info *ci,
302 fscrypt_direction_t rw, u64 index,
303 struct page *src_page, struct page *dest_page,
304 unsigned int len, unsigned int offs,
305 gfp_t gfp_flags);
306struct page *fscrypt_alloc_bounce_page(gfp_t gfp_flags);
307
308void __printf(3, 4) __cold
309fscrypt_msg(const struct inode *inode, const char *level, const char *fmt, ...);
310
311#define fscrypt_warn(inode, fmt, ...) \
312 fscrypt_msg((inode), KERN_WARNING, fmt, ##__VA_ARGS__)
313#define fscrypt_err(inode, fmt, ...) \
314 fscrypt_msg((inode), KERN_ERR, fmt, ##__VA_ARGS__)
315
316#define FSCRYPT_MAX_IV_SIZE 32
317
318union fscrypt_iv {
319 struct {
320 /* zero-based index of data unit within the file */
321 __le64 index;
322
323 /* per-file nonce; only set in DIRECT_KEY mode */
324 u8 nonce[FSCRYPT_FILE_NONCE_SIZE];
325 };
326 u8 raw[FSCRYPT_MAX_IV_SIZE];
327 __le64 dun[FSCRYPT_MAX_IV_SIZE / sizeof(__le64)];
328};
329
330void fscrypt_generate_iv(union fscrypt_iv *iv, u64 index,
331 const struct fscrypt_inode_info *ci);
332
333/*
334 * Return the number of bits used by the maximum file data unit index that is
335 * possible on the given filesystem, using the given log2 data unit size.
336 */
337static inline int
338fscrypt_max_file_dun_bits(const struct super_block *sb, int du_bits)
339{
340 return fls64(sb->s_maxbytes - 1) - du_bits;
341}
342
343/* fname.c */
344bool __fscrypt_fname_encrypted_size(const union fscrypt_policy *policy,
345 u32 orig_len, u32 max_len,
346 u32 *encrypted_len_ret);
347
348/* hkdf.c */
349struct fscrypt_hkdf {
350 struct crypto_shash *hmac_tfm;
351};
352
353int fscrypt_init_hkdf(struct fscrypt_hkdf *hkdf, const u8 *master_key,
354 unsigned int master_key_size);
355
356/*
357 * The list of contexts in which fscrypt uses HKDF. These values are used as
358 * the first byte of the HKDF application-specific info string to guarantee that
359 * info strings are never repeated between contexts. This ensures that all HKDF
360 * outputs are unique and cryptographically isolated, i.e. knowledge of one
361 * output doesn't reveal another.
362 */
363#define HKDF_CONTEXT_KEY_IDENTIFIER 1 /* info=<empty> */
364#define HKDF_CONTEXT_PER_FILE_ENC_KEY 2 /* info=file_nonce */
365#define HKDF_CONTEXT_DIRECT_KEY 3 /* info=mode_num */
366#define HKDF_CONTEXT_IV_INO_LBLK_64_KEY 4 /* info=mode_num||fs_uuid */
367#define HKDF_CONTEXT_DIRHASH_KEY 5 /* info=file_nonce */
368#define HKDF_CONTEXT_IV_INO_LBLK_32_KEY 6 /* info=mode_num||fs_uuid */
369#define HKDF_CONTEXT_INODE_HASH_KEY 7 /* info=<empty> */
370
371int fscrypt_hkdf_expand(const struct fscrypt_hkdf *hkdf, u8 context,
372 const u8 *info, unsigned int infolen,
373 u8 *okm, unsigned int okmlen);
374
375void fscrypt_destroy_hkdf(struct fscrypt_hkdf *hkdf);
376
377/* inline_crypt.c */
378#ifdef CONFIG_FS_ENCRYPTION_INLINE_CRYPT
379int fscrypt_select_encryption_impl(struct fscrypt_inode_info *ci);
380
381static inline bool
382fscrypt_using_inline_encryption(const struct fscrypt_inode_info *ci)
383{
384 return ci->ci_inlinecrypt;
385}
386
387int fscrypt_prepare_inline_crypt_key(struct fscrypt_prepared_key *prep_key,
388 const u8 *raw_key,
389 const struct fscrypt_inode_info *ci);
390
391void fscrypt_destroy_inline_crypt_key(struct super_block *sb,
392 struct fscrypt_prepared_key *prep_key);
393
394/*
395 * Check whether the crypto transform or blk-crypto key has been allocated in
396 * @prep_key, depending on which encryption implementation the file will use.
397 */
398static inline bool
399fscrypt_is_key_prepared(struct fscrypt_prepared_key *prep_key,
400 const struct fscrypt_inode_info *ci)
401{
402 /*
403 * The two smp_load_acquire()'s here pair with the smp_store_release()'s
404 * in fscrypt_prepare_inline_crypt_key() and fscrypt_prepare_key().
405 * I.e., in some cases (namely, if this prep_key is a per-mode
406 * encryption key) another task can publish blk_key or tfm concurrently,
407 * executing a RELEASE barrier. We need to use smp_load_acquire() here
408 * to safely ACQUIRE the memory the other task published.
409 */
410 if (fscrypt_using_inline_encryption(ci))
411 return smp_load_acquire(&prep_key->blk_key) != NULL;
412 return smp_load_acquire(&prep_key->tfm) != NULL;
413}
414
415#else /* CONFIG_FS_ENCRYPTION_INLINE_CRYPT */
416
417static inline int fscrypt_select_encryption_impl(struct fscrypt_inode_info *ci)
418{
419 return 0;
420}
421
422static inline bool
423fscrypt_using_inline_encryption(const struct fscrypt_inode_info *ci)
424{
425 return false;
426}
427
428static inline int
429fscrypt_prepare_inline_crypt_key(struct fscrypt_prepared_key *prep_key,
430 const u8 *raw_key,
431 const struct fscrypt_inode_info *ci)
432{
433 WARN_ON_ONCE(1);
434 return -EOPNOTSUPP;
435}
436
437static inline void
438fscrypt_destroy_inline_crypt_key(struct super_block *sb,
439 struct fscrypt_prepared_key *prep_key)
440{
441}
442
443static inline bool
444fscrypt_is_key_prepared(struct fscrypt_prepared_key *prep_key,
445 const struct fscrypt_inode_info *ci)
446{
447 return smp_load_acquire(&prep_key->tfm) != NULL;
448}
449#endif /* !CONFIG_FS_ENCRYPTION_INLINE_CRYPT */
450
451/* keyring.c */
452
453/*
454 * fscrypt_master_key_secret - secret key material of an in-use master key
455 */
456struct fscrypt_master_key_secret {
457
458 /*
459 * For v2 policy keys: HKDF context keyed by this master key.
460 * For v1 policy keys: not set (hkdf.hmac_tfm == NULL).
461 */
462 struct fscrypt_hkdf hkdf;
463
464 /*
465 * Size of the raw key in bytes. This remains set even if ->raw was
466 * zeroized due to no longer being needed. I.e. we still remember the
467 * size of the key even if we don't need to remember the key itself.
468 */
469 u32 size;
470
471 /* For v1 policy keys: the raw key. Wiped for v2 policy keys. */
472 u8 raw[FSCRYPT_MAX_KEY_SIZE];
473
474} __randomize_layout;
475
476/*
477 * fscrypt_master_key - an in-use master key
478 *
479 * This represents a master encryption key which has been added to the
480 * filesystem. There are three high-level states that a key can be in:
481 *
482 * FSCRYPT_KEY_STATUS_PRESENT
483 * Key is fully usable; it can be used to unlock inodes that are encrypted
484 * with it (this includes being able to create new inodes). ->mk_present
485 * indicates whether the key is in this state. ->mk_secret exists, the key
486 * is in the keyring, and ->mk_active_refs > 0 due to ->mk_present.
487 *
488 * FSCRYPT_KEY_STATUS_INCOMPLETELY_REMOVED
489 * Removal of this key has been initiated, but some inodes that were
490 * unlocked with it are still in-use. Like ABSENT, ->mk_secret is wiped,
491 * and the key can no longer be used to unlock inodes. Unlike ABSENT, the
492 * key is still in the keyring; ->mk_decrypted_inodes is nonempty; and
493 * ->mk_active_refs > 0, being equal to the size of ->mk_decrypted_inodes.
494 *
495 * This state transitions to ABSENT if ->mk_decrypted_inodes becomes empty,
496 * or to PRESENT if FS_IOC_ADD_ENCRYPTION_KEY is called again for this key.
497 *
498 * FSCRYPT_KEY_STATUS_ABSENT
499 * Key is fully removed. The key is no longer in the keyring,
500 * ->mk_decrypted_inodes is empty, ->mk_active_refs == 0, ->mk_secret is
501 * wiped, and the key can no longer be used to unlock inodes.
502 */
503struct fscrypt_master_key {
504
505 /*
506 * Link in ->s_master_keys->key_hashtable.
507 * Only valid if ->mk_active_refs > 0.
508 */
509 struct hlist_node mk_node;
510
511 /* Semaphore that protects ->mk_secret, ->mk_users, and ->mk_present */
512 struct rw_semaphore mk_sem;
513
514 /*
515 * Active and structural reference counts. An active ref guarantees
516 * that the struct continues to exist, continues to be in the keyring
517 * ->s_master_keys, and that any embedded subkeys (e.g.
518 * ->mk_direct_keys) that have been prepared continue to exist.
519 * A structural ref only guarantees that the struct continues to exist.
520 *
521 * There is one active ref associated with ->mk_present being true, and
522 * one active ref for each inode in ->mk_decrypted_inodes.
523 *
524 * There is one structural ref associated with the active refcount being
525 * nonzero. Finding a key in the keyring also takes a structural ref,
526 * which is then held temporarily while the key is operated on.
527 */
528 refcount_t mk_active_refs;
529 refcount_t mk_struct_refs;
530
531 struct rcu_head mk_rcu_head;
532
533 /*
534 * The secret key material. Wiped as soon as it is no longer needed;
535 * for details, see the fscrypt_master_key struct comment.
536 *
537 * Locking: protected by ->mk_sem.
538 */
539 struct fscrypt_master_key_secret mk_secret;
540
541 /*
542 * For v1 policy keys: an arbitrary key descriptor which was assigned by
543 * userspace (->descriptor).
544 *
545 * For v2 policy keys: a cryptographic hash of this key (->identifier).
546 */
547 struct fscrypt_key_specifier mk_spec;
548
549 /*
550 * Keyring which contains a key of type 'key_type_fscrypt_user' for each
551 * user who has added this key. Normally each key will be added by just
552 * one user, but it's possible that multiple users share a key, and in
553 * that case we need to keep track of those users so that one user can't
554 * remove the key before the others want it removed too.
555 *
556 * This is NULL for v1 policy keys; those can only be added by root.
557 *
558 * Locking: protected by ->mk_sem. (We don't just rely on the keyrings
559 * subsystem semaphore ->mk_users->sem, as we need support for atomic
560 * search+insert along with proper synchronization with other fields.)
561 */
562 struct key *mk_users;
563
564 /*
565 * List of inodes that were unlocked using this key. This allows the
566 * inodes to be evicted efficiently if the key is removed.
567 */
568 struct list_head mk_decrypted_inodes;
569 spinlock_t mk_decrypted_inodes_lock;
570
571 /*
572 * Per-mode encryption keys for the various types of encryption policies
573 * that use them. Allocated and derived on-demand.
574 */
575 struct fscrypt_prepared_key mk_direct_keys[FSCRYPT_MODE_MAX + 1];
576 struct fscrypt_prepared_key mk_iv_ino_lblk_64_keys[FSCRYPT_MODE_MAX + 1];
577 struct fscrypt_prepared_key mk_iv_ino_lblk_32_keys[FSCRYPT_MODE_MAX + 1];
578
579 /* Hash key for inode numbers. Initialized only when needed. */
580 siphash_key_t mk_ino_hash_key;
581 bool mk_ino_hash_key_initialized;
582
583 /*
584 * Whether this key is in the "present" state, i.e. fully usable. For
585 * details, see the fscrypt_master_key struct comment.
586 *
587 * Locking: protected by ->mk_sem, but can be read locklessly using
588 * READ_ONCE(). Writers must use WRITE_ONCE() when concurrent readers
589 * are possible.
590 */
591 bool mk_present;
592
593} __randomize_layout;
594
595static inline const char *master_key_spec_type(
596 const struct fscrypt_key_specifier *spec)
597{
598 switch (spec->type) {
599 case FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR:
600 return "descriptor";
601 case FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER:
602 return "identifier";
603 }
604 return "[unknown]";
605}
606
607static inline int master_key_spec_len(const struct fscrypt_key_specifier *spec)
608{
609 switch (spec->type) {
610 case FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR:
611 return FSCRYPT_KEY_DESCRIPTOR_SIZE;
612 case FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER:
613 return FSCRYPT_KEY_IDENTIFIER_SIZE;
614 }
615 return 0;
616}
617
618void fscrypt_put_master_key(struct fscrypt_master_key *mk);
619
620void fscrypt_put_master_key_activeref(struct super_block *sb,
621 struct fscrypt_master_key *mk);
622
623struct fscrypt_master_key *
624fscrypt_find_master_key(struct super_block *sb,
625 const struct fscrypt_key_specifier *mk_spec);
626
627int fscrypt_get_test_dummy_key_identifier(
628 u8 key_identifier[FSCRYPT_KEY_IDENTIFIER_SIZE]);
629
630int fscrypt_add_test_dummy_key(struct super_block *sb,
631 struct fscrypt_key_specifier *key_spec);
632
633int fscrypt_verify_key_added(struct super_block *sb,
634 const u8 identifier[FSCRYPT_KEY_IDENTIFIER_SIZE]);
635
636int __init fscrypt_init_keyring(void);
637
638/* keysetup.c */
639
640struct fscrypt_mode {
641 const char *friendly_name;
642 const char *cipher_str;
643 int keysize; /* key size in bytes */
644 int security_strength; /* security strength in bytes */
645 int ivsize; /* IV size in bytes */
646 int logged_cryptoapi_impl;
647 int logged_blk_crypto_native;
648 int logged_blk_crypto_fallback;
649 enum blk_crypto_mode_num blk_crypto_mode;
650};
651
652extern struct fscrypt_mode fscrypt_modes[];
653
654int fscrypt_prepare_key(struct fscrypt_prepared_key *prep_key,
655 const u8 *raw_key, const struct fscrypt_inode_info *ci);
656
657void fscrypt_destroy_prepared_key(struct super_block *sb,
658 struct fscrypt_prepared_key *prep_key);
659
660int fscrypt_set_per_file_enc_key(struct fscrypt_inode_info *ci,
661 const u8 *raw_key);
662
663int fscrypt_derive_dirhash_key(struct fscrypt_inode_info *ci,
664 const struct fscrypt_master_key *mk);
665
666void fscrypt_hash_inode_number(struct fscrypt_inode_info *ci,
667 const struct fscrypt_master_key *mk);
668
669int fscrypt_get_encryption_info(struct inode *inode, bool allow_unsupported);
670
671/**
672 * fscrypt_require_key() - require an inode's encryption key
673 * @inode: the inode we need the key for
674 *
675 * If the inode is encrypted, set up its encryption key if not already done.
676 * Then require that the key be present and return -ENOKEY otherwise.
677 *
678 * No locks are needed, and the key will live as long as the struct inode --- so
679 * it won't go away from under you.
680 *
681 * Return: 0 on success, -ENOKEY if the key is missing, or another -errno code
682 * if a problem occurred while setting up the encryption key.
683 */
684static inline int fscrypt_require_key(struct inode *inode)
685{
686 if (IS_ENCRYPTED(inode)) {
687 int err = fscrypt_get_encryption_info(inode, false);
688
689 if (err)
690 return err;
691 if (!fscrypt_has_encryption_key(inode))
692 return -ENOKEY;
693 }
694 return 0;
695}
696
697/* keysetup_v1.c */
698
699void fscrypt_put_direct_key(struct fscrypt_direct_key *dk);
700
701int fscrypt_setup_v1_file_key(struct fscrypt_inode_info *ci,
702 const u8 *raw_master_key);
703
704int fscrypt_setup_v1_file_key_via_subscribed_keyrings(
705 struct fscrypt_inode_info *ci);
706
707/* policy.c */
708
709bool fscrypt_policies_equal(const union fscrypt_policy *policy1,
710 const union fscrypt_policy *policy2);
711int fscrypt_policy_to_key_spec(const union fscrypt_policy *policy,
712 struct fscrypt_key_specifier *key_spec);
713const union fscrypt_policy *fscrypt_get_dummy_policy(struct super_block *sb);
714bool fscrypt_supported_policy(const union fscrypt_policy *policy_u,
715 const struct inode *inode);
716int fscrypt_policy_from_context(union fscrypt_policy *policy_u,
717 const union fscrypt_context *ctx_u,
718 int ctx_size);
719const union fscrypt_policy *fscrypt_policy_to_inherit(struct inode *dir);
720
721#endif /* _FSCRYPT_PRIVATE_H */