include/linux/fscrypto.h

   1 /*
   2  * General per-file encryption definition
   3  *
   4  * Copyright (C) 2015, Google, Inc.
   5  *
   6  * Written by Michael Halcrow, 2015.
   7  * Modified by Jaegeuk Kim, 2015.
   8  */
   9
  10 #ifndef _LINUX_FSCRYPTO_H
  11 #define _LINUX_FSCRYPTO_H
  12
  13 #include <linux/key.h>
  14 #include <linux/fs.h>
  15 #include <linux/mm.h>
  16 #include <linux/bio.h>
  17 #include <linux/dcache.h>
  18 #include <crypto/skcipher.h>
  19 #include <uapi/linux/fs.h>
  20
  21 #define FS_KEY_DERIVATION_NONCE_SIZE            16
  22 #define FS_ENCRYPTION_CONTEXT_FORMAT_V1         1
  23
  24 #define FS_POLICY_FLAGS_PAD_4           0x00
  25 #define FS_POLICY_FLAGS_PAD_8           0x01
  26 #define FS_POLICY_FLAGS_PAD_16          0x02
  27 #define FS_POLICY_FLAGS_PAD_32          0x03
  28 #define FS_POLICY_FLAGS_PAD_MASK        0x03
  29 #define FS_POLICY_FLAGS_VALID           0x03
  30
  31 /* Encryption algorithms */
  32 #define FS_ENCRYPTION_MODE_INVALID              0
  33 #define FS_ENCRYPTION_MODE_AES_256_XTS          1
  34 #define FS_ENCRYPTION_MODE_AES_256_GCM          2
  35 #define FS_ENCRYPTION_MODE_AES_256_CBC          3
  36 #define FS_ENCRYPTION_MODE_AES_256_CTS          4
  37
  38 /**
  39  * Encryption context for inode
  40  *
  41  * Protector format:
  42  *  1 byte: Protector format (1 = this version)
  43  *  1 byte: File contents encryption mode
  44  *  1 byte: File names encryption mode
  45  *  1 byte: Flags
  46  *  8 bytes: Master Key descriptor
  47  *  16 bytes: Encryption Key derivation nonce
  48  */
  49 struct fscrypt_context {
  50         u8 format;
  51         u8 contents_encryption_mode;
  52         u8 filenames_encryption_mode;
  53         u8 flags;
  54         u8 master_key_descriptor[FS_KEY_DESCRIPTOR_SIZE];
  55         u8 nonce[FS_KEY_DERIVATION_NONCE_SIZE];
  56 } __packed;
  57
  58 /* Encryption parameters */
  59 #define FS_XTS_TWEAK_SIZE               16
  60 #define FS_AES_128_ECB_KEY_SIZE         16
  61 #define FS_AES_256_GCM_KEY_SIZE         32
  62 #define FS_AES_256_CBC_KEY_SIZE         32
  63 #define FS_AES_256_CTS_KEY_SIZE         32
  64 #define FS_AES_256_XTS_KEY_SIZE         64
  65 #define FS_MAX_KEY_SIZE                 64
  66
  67 #define FS_KEY_DESC_PREFIX              "fscrypt:"
  68 #define FS_KEY_DESC_PREFIX_SIZE         8
  69
  70 /* This is passed in from userspace into the kernel keyring */
  71 struct fscrypt_key {
  72         u32 mode;
  73         u8 raw[FS_MAX_KEY_SIZE];
  74         u32 size;
  75 } __packed;
  76
  77 struct fscrypt_info {
  78         u8 ci_data_mode;
  79         u8 ci_filename_mode;
  80         u8 ci_flags;
  81         struct crypto_skcipher *ci_ctfm;
  82         struct key *ci_keyring_key;
  83         u8 ci_master_key[FS_KEY_DESCRIPTOR_SIZE];
  84 };
  85
  86 #define FS_CTX_REQUIRES_FREE_ENCRYPT_FL         0x00000001
  87 #define FS_WRITE_PATH_FL                        0x00000002
  88
  89 struct fscrypt_ctx {
  90         union {
  91                 struct {
  92                         struct page *bounce_page;       /* Ciphertext page */
  93                         struct page *control_page;      /* Original page  */
  94                 } w;
  95                 struct {
  96                         struct bio *bio;
  97                         struct work_struct work;
  98                 } r;
  99                 struct list_head free_list;     /* Free list */
 100         };
 101         u8 flags;                               /* Flags */
 102         u8 mode;                                /* Encryption mode for tfm */
 103 };
 104
 105 struct fscrypt_completion_result {
 106         struct completion completion;
 107         int res;
 108 };
 109
 110 #define DECLARE_FS_COMPLETION_RESULT(ecr) \
 111         struct fscrypt_completion_result ecr = { \
 112                 COMPLETION_INITIALIZER((ecr).completion), 0 }
 113
 114 static inline int fscrypt_key_size(int mode)
 115 {
 116         switch (mode) {
 117         case FS_ENCRYPTION_MODE_AES_256_XTS:
 118                 return FS_AES_256_XTS_KEY_SIZE;
 119         case FS_ENCRYPTION_MODE_AES_256_GCM:
 120                 return FS_AES_256_GCM_KEY_SIZE;
 121         case FS_ENCRYPTION_MODE_AES_256_CBC:
 122                 return FS_AES_256_CBC_KEY_SIZE;
 123         case FS_ENCRYPTION_MODE_AES_256_CTS:
 124                 return FS_AES_256_CTS_KEY_SIZE;
 125         default:
 126                 BUG();
 127         }
 128         return 0;
 129 }
 130
 131 #define FS_FNAME_NUM_SCATTER_ENTRIES    4
 132 #define FS_CRYPTO_BLOCK_SIZE            16
 133 #define FS_FNAME_CRYPTO_DIGEST_SIZE     32
 134
 135 /**
 136  * For encrypted symlinks, the ciphertext length is stored at the beginning
 137  * of the string in little-endian format.
 138  */
 139 struct fscrypt_symlink_data {
 140         __le16 len;
 141         char encrypted_path[1];
 142 } __packed;
 143
 144 /**
 145  * This function is used to calculate the disk space required to
 146  * store a filename of length l in encrypted symlink format.
 147  */
 148 static inline u32 fscrypt_symlink_data_len(u32 l)
 149 {
 150         if (l < FS_CRYPTO_BLOCK_SIZE)
 151                 l = FS_CRYPTO_BLOCK_SIZE;
 152         return (l + sizeof(struct fscrypt_symlink_data) - 1);
 153 }
 154
 155 struct fscrypt_str {
 156         unsigned char *name;
 157         u32 len;
 158 };
 159
 160 struct fscrypt_name {
 161         const struct qstr *usr_fname;
 162         struct fscrypt_str disk_name;
 163         u32 hash;
 164         u32 minor_hash;
 165         struct fscrypt_str crypto_buf;
 166 };
 167
 168 #define FSTR_INIT(n, l)         { .name = n, .len = l }
 169 #define FSTR_TO_QSTR(f)         QSTR_INIT((f)->name, (f)->len)
 170 #define fname_name(p)           ((p)->disk_name.name)
 171 #define fname_len(p)            ((p)->disk_name.len)
 172
 173 /*
 174  * crypto opertions for filesystems
 175  */
 176 struct fscrypt_operations {
 177         int (*get_context)(struct inode *, void *, size_t);
 178         int (*prepare_context)(struct inode *);
 179         int (*set_context)(struct inode *, const void *, size_t, void *);
 180         int (*dummy_context)(struct inode *);
 181         bool (*is_encrypted)(struct inode *);
 182         bool (*empty_dir)(struct inode *);
 183         unsigned (*max_namelen)(struct inode *);
 184 };
 185
 186 static inline bool fscrypt_dummy_context_enabled(struct inode *inode)
 187 {
 188         if (inode->i_sb->s_cop->dummy_context &&
 189                                 inode->i_sb->s_cop->dummy_context(inode))
 190                 return true;
 191         return false;
 192 }
 193
 194 static inline bool fscrypt_valid_contents_enc_mode(u32 mode)
 195 {
 196         return (mode == FS_ENCRYPTION_MODE_AES_256_XTS);
 197 }
 198
 199 static inline bool fscrypt_valid_filenames_enc_mode(u32 mode)
 200 {
 201         return (mode == FS_ENCRYPTION_MODE_AES_256_CTS);
 202 }
 203
 204 static inline u32 fscrypt_validate_encryption_key_size(u32 mode, u32 size)
 205 {
 206         if (size == fscrypt_key_size(mode))
 207                 return size;
 208         return 0;
 209 }
 210
 211 static inline bool fscrypt_is_dot_dotdot(const struct qstr *str)
 212 {
 213         if (str->len == 1 && str->name[0] == '.')
 214                 return true;
 215
 216         if (str->len == 2 && str->name[0] == '.' && str->name[1] == '.')
 217                 return true;
 218
 219         return false;
 220 }
 221
 222 static inline struct page *fscrypt_control_page(struct page *page)
 223 {
 224 #if IS_ENABLED(CONFIG_FS_ENCRYPTION)
 225         return ((struct fscrypt_ctx *)page_private(page))->w.control_page;
 226 #else
 227         WARN_ON_ONCE(1);
 228         return ERR_PTR(-EINVAL);
 229 #endif
 230 }
 231
 232 static inline int fscrypt_has_encryption_key(struct inode *inode)
 233 {
 234 #if IS_ENABLED(CONFIG_FS_ENCRYPTION)
 235         return (inode->i_crypt_info != NULL);
 236 #else
 237         return 0;
 238 #endif
 239 }
 240
 241 static inline void fscrypt_set_encrypted_dentry(struct dentry *dentry)
 242 {
 243 #if IS_ENABLED(CONFIG_FS_ENCRYPTION)
 244         spin_lock(&dentry->d_lock);
 245         dentry->d_flags |= DCACHE_ENCRYPTED_WITH_KEY;
 246         spin_unlock(&dentry->d_lock);
 247 #endif
 248 }
 249
 250 #if IS_ENABLED(CONFIG_FS_ENCRYPTION)
 251 extern const struct dentry_operations fscrypt_d_ops;
 252 #endif
 253
 254 static inline void fscrypt_set_d_op(struct dentry *dentry)
 255 {
 256 #if IS_ENABLED(CONFIG_FS_ENCRYPTION)
 257         d_set_d_op(dentry, &fscrypt_d_ops);
 258 #endif
 259 }
 260
 261 #if IS_ENABLED(CONFIG_FS_ENCRYPTION)
 262 /* crypto.c */
 263 extern struct kmem_cache *fscrypt_info_cachep;
 264 int fscrypt_initialize(void);
 265
 266 extern struct fscrypt_ctx *fscrypt_get_ctx(struct inode *, gfp_t);
 267 extern void fscrypt_release_ctx(struct fscrypt_ctx *);
 268 extern struct page *fscrypt_encrypt_page(struct inode *, struct page *, gfp_t);
 269 extern int fscrypt_decrypt_page(struct page *);
 270 extern void fscrypt_decrypt_bio_pages(struct fscrypt_ctx *, struct bio *);
 271 extern void fscrypt_pullback_bio_page(struct page **, bool);
 272 extern void fscrypt_restore_control_page(struct page *);
 273 extern int fscrypt_zeroout_range(struct inode *, pgoff_t, sector_t,
 274                                                 unsigned int);
 275 /* policy.c */
 276 extern int fscrypt_process_policy(struct inode *,
 277                                         const struct fscrypt_policy *);
 278 extern int fscrypt_get_policy(struct inode *, struct fscrypt_policy *);
 279 extern int fscrypt_has_permitted_context(struct inode *, struct inode *);
 280 extern int fscrypt_inherit_context(struct inode *, struct inode *,
 281                                         void *, bool);
 282 /* keyinfo.c */
 283 extern int get_crypt_info(struct inode *);
 284 extern int fscrypt_get_encryption_info(struct inode *);
 285 extern void fscrypt_put_encryption_info(struct inode *, struct fscrypt_info *);
 286
 287 /* fname.c */
 288 extern int fscrypt_setup_filename(struct inode *, const struct qstr *,
 289                                 int lookup, struct fscrypt_name *);
 290 extern void fscrypt_free_filename(struct fscrypt_name *);
 291 extern u32 fscrypt_fname_encrypted_size(struct inode *, u32);
 292 extern int fscrypt_fname_alloc_buffer(struct inode *, u32,
 293                                 struct fscrypt_str *);
 294 extern void fscrypt_fname_free_buffer(struct fscrypt_str *);
 295 extern int fscrypt_fname_disk_to_usr(struct inode *, u32, u32,
 296                         const struct fscrypt_str *, struct fscrypt_str *);
 297 extern int fscrypt_fname_usr_to_disk(struct inode *, const struct qstr *,
 298                         struct fscrypt_str *);
 299 #endif
 300
 301 /* crypto.c */
 302 static inline struct fscrypt_ctx *fscrypt_notsupp_get_ctx(struct inode *i,
 303                                                         gfp_t f)
 304 {
 305         return ERR_PTR(-EOPNOTSUPP);
 306 }
 307
 308 static inline void fscrypt_notsupp_release_ctx(struct fscrypt_ctx *c)
 309 {
 310         return;
 311 }
 312
 313 static inline struct page *fscrypt_notsupp_encrypt_page(struct inode *i,
 314                                                 struct page *p, gfp_t f)
 315 {
 316         return ERR_PTR(-EOPNOTSUPP);
 317 }
 318
 319 static inline int fscrypt_notsupp_decrypt_page(struct page *p)
 320 {
 321         return -EOPNOTSUPP;
 322 }
 323
 324 static inline void fscrypt_notsupp_decrypt_bio_pages(struct fscrypt_ctx *c,
 325                                                 struct bio *b)
 326 {
 327         return;
 328 }
 329
 330 static inline void fscrypt_notsupp_pullback_bio_page(struct page **p, bool b)
 331 {
 332         return;
 333 }
 334
 335 static inline void fscrypt_notsupp_restore_control_page(struct page *p)
 336 {
 337         return;
 338 }
 339
 340 static inline int fscrypt_notsupp_zeroout_range(struct inode *i, pgoff_t p,
 341                                         sector_t s, unsigned int f)
 342 {
 343         return -EOPNOTSUPP;
 344 }
 345
 346 /* policy.c */
 347 static inline int fscrypt_notsupp_process_policy(struct inode *i,
 348                                 const struct fscrypt_policy *p)
 349 {
 350         return -EOPNOTSUPP;
 351 }
 352
 353 static inline int fscrypt_notsupp_get_policy(struct inode *i,
 354                                 struct fscrypt_policy *p)
 355 {
 356         return -EOPNOTSUPP;
 357 }
 358
 359 static inline int fscrypt_notsupp_has_permitted_context(struct inode *p,
 360                                 struct inode *i)
 361 {
 362         return 0;
 363 }
 364
 365 static inline int fscrypt_notsupp_inherit_context(struct inode *p,
 366                                 struct inode *i, void *v, bool b)
 367 {
 368         return -EOPNOTSUPP;
 369 }
 370
 371 /* keyinfo.c */
 372 static inline int fscrypt_notsupp_get_encryption_info(struct inode *i)
 373 {
 374         return -EOPNOTSUPP;
 375 }
 376
 377 static inline void fscrypt_notsupp_put_encryption_info(struct inode *i,
 378                                         struct fscrypt_info *f)
 379 {
 380         return;
 381 }
 382
 383  /* fname.c */
 384 static inline int fscrypt_notsupp_setup_filename(struct inode *dir,
 385                         const struct qstr *iname,
 386                         int lookup, struct fscrypt_name *fname)
 387 {
 388         if (dir->i_sb->s_cop->is_encrypted(dir))
 389                 return -EOPNOTSUPP;
 390
 391         memset(fname, 0, sizeof(struct fscrypt_name));
 392         fname->usr_fname = iname;
 393         fname->disk_name.name = (unsigned char *)iname->name;
 394         fname->disk_name.len = iname->len;
 395         return 0;
 396 }
 397
 398 static inline void fscrypt_notsupp_free_filename(struct fscrypt_name *fname)
 399 {
 400         return;
 401 }
 402
 403 static inline u32 fscrypt_notsupp_fname_encrypted_size(struct inode *i, u32 s)
 404 {
 405         /* never happens */
 406         WARN_ON(1);
 407         return 0;
 408 }
 409
 410 static inline int fscrypt_notsupp_fname_alloc_buffer(struct inode *inode,
 411                                 u32 ilen, struct fscrypt_str *crypto_str)
 412 {
 413         return -EOPNOTSUPP;
 414 }
 415
 416 static inline void fscrypt_notsupp_fname_free_buffer(struct fscrypt_str *c)
 417 {
 418         return;
 419 }
 420
 421 static inline int fscrypt_notsupp_fname_disk_to_usr(struct inode *inode,
 422                         u32 hash, u32 minor_hash,
 423                         const struct fscrypt_str *iname,
 424                         struct fscrypt_str *oname)
 425 {
 426         return -EOPNOTSUPP;
 427 }
 428
 429 static inline int fscrypt_notsupp_fname_usr_to_disk(struct inode *inode,
 430                         const struct qstr *iname,
 431                         struct fscrypt_str *oname)
 432 {
 433         return -EOPNOTSUPP;
 434 }
 435 #endif  /* _LINUX_FSCRYPTO_H */