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 #define FS_FNAME_NUM_SCATTER_ENTRIES    4
 115 #define FS_CRYPTO_BLOCK_SIZE            16
 116 #define FS_FNAME_CRYPTO_DIGEST_SIZE     32
 117
 118 /**
 119  * For encrypted symlinks, the ciphertext length is stored at the beginning
 120  * of the string in little-endian format.
 121  */
 122 struct fscrypt_symlink_data {
 123         __le16 len;
 124         char encrypted_path[1];
 125 } __packed;
 126
 127 /**
 128  * This function is used to calculate the disk space required to
 129  * store a filename of length l in encrypted symlink format.
 130  */
 131 static inline u32 fscrypt_symlink_data_len(u32 l)
 132 {
 133         if (l < FS_CRYPTO_BLOCK_SIZE)
 134                 l = FS_CRYPTO_BLOCK_SIZE;
 135         return (l + sizeof(struct fscrypt_symlink_data) - 1);
 136 }
 137
 138 struct fscrypt_str {
 139         unsigned char *name;
 140         u32 len;
 141 };
 142
 143 struct fscrypt_name {
 144         const struct qstr *usr_fname;
 145         struct fscrypt_str disk_name;
 146         u32 hash;
 147         u32 minor_hash;
 148         struct fscrypt_str crypto_buf;
 149 };
 150
 151 #define FSTR_INIT(n, l)         { .name = n, .len = l }
 152 #define FSTR_TO_QSTR(f)         QSTR_INIT((f)->name, (f)->len)
 153 #define fname_name(p)           ((p)->disk_name.name)
 154 #define fname_len(p)            ((p)->disk_name.len)
 155
 156 /*
 157  * crypto opertions for filesystems
 158  */
 159 struct fscrypt_operations {
 160         int (*get_context)(struct inode *, void *, size_t);
 161         int (*key_prefix)(struct inode *, u8 **);
 162         int (*prepare_context)(struct inode *);
 163         int (*set_context)(struct inode *, const void *, size_t, void *);
 164         int (*dummy_context)(struct inode *);
 165         bool (*is_encrypted)(struct inode *);
 166         bool (*empty_dir)(struct inode *);
 167         unsigned (*max_namelen)(struct inode *);
 168 };
 169
 170 static inline bool fscrypt_dummy_context_enabled(struct inode *inode)
 171 {
 172         if (inode->i_sb->s_cop->dummy_context &&
 173                                 inode->i_sb->s_cop->dummy_context(inode))
 174                 return true;
 175         return false;
 176 }
 177
 178 static inline bool fscrypt_valid_contents_enc_mode(u32 mode)
 179 {
 180         return (mode == FS_ENCRYPTION_MODE_AES_256_XTS);
 181 }
 182
 183 static inline bool fscrypt_valid_filenames_enc_mode(u32 mode)
 184 {
 185         return (mode == FS_ENCRYPTION_MODE_AES_256_CTS);
 186 }
 187
 188 static inline bool fscrypt_is_dot_dotdot(const struct qstr *str)
 189 {
 190         if (str->len == 1 && str->name[0] == '.')
 191                 return true;
 192
 193         if (str->len == 2 && str->name[0] == '.' && str->name[1] == '.')
 194                 return true;
 195
 196         return false;
 197 }
 198
 199 static inline struct page *fscrypt_control_page(struct page *page)
 200 {
 201 #if IS_ENABLED(CONFIG_FS_ENCRYPTION)
 202         return ((struct fscrypt_ctx *)page_private(page))->w.control_page;
 203 #else
 204         WARN_ON_ONCE(1);
 205         return ERR_PTR(-EINVAL);
 206 #endif
 207 }
 208
 209 static inline int fscrypt_has_encryption_key(struct inode *inode)
 210 {
 211 #if IS_ENABLED(CONFIG_FS_ENCRYPTION)
 212         return (inode->i_crypt_info != NULL);
 213 #else
 214         return 0;
 215 #endif
 216 }
 217
 218 static inline void fscrypt_set_encrypted_dentry(struct dentry *dentry)
 219 {
 220 #if IS_ENABLED(CONFIG_FS_ENCRYPTION)
 221         spin_lock(&dentry->d_lock);
 222         dentry->d_flags |= DCACHE_ENCRYPTED_WITH_KEY;
 223         spin_unlock(&dentry->d_lock);
 224 #endif
 225 }
 226
 227 #if IS_ENABLED(CONFIG_FS_ENCRYPTION)
 228 extern const struct dentry_operations fscrypt_d_ops;
 229 #endif
 230
 231 static inline void fscrypt_set_d_op(struct dentry *dentry)
 232 {
 233 #if IS_ENABLED(CONFIG_FS_ENCRYPTION)
 234         d_set_d_op(dentry, &fscrypt_d_ops);
 235 #endif
 236 }
 237
 238 #if IS_ENABLED(CONFIG_FS_ENCRYPTION)
 239 /* crypto.c */
 240 extern struct kmem_cache *fscrypt_info_cachep;
 241 int fscrypt_initialize(void);
 242
 243 extern struct fscrypt_ctx *fscrypt_get_ctx(struct inode *, gfp_t);
 244 extern void fscrypt_release_ctx(struct fscrypt_ctx *);
 245 extern struct page *fscrypt_encrypt_page(struct inode *, struct page *, gfp_t);
 246 extern int fscrypt_decrypt_page(struct page *);
 247 extern void fscrypt_decrypt_bio_pages(struct fscrypt_ctx *, struct bio *);
 248 extern void fscrypt_pullback_bio_page(struct page **, bool);
 249 extern void fscrypt_restore_control_page(struct page *);
 250 extern int fscrypt_zeroout_range(struct inode *, pgoff_t, sector_t,
 251                                                 unsigned int);
 252 /* policy.c */
 253 extern int fscrypt_process_policy(struct file *, const struct fscrypt_policy *);
 254 extern int fscrypt_get_policy(struct inode *, struct fscrypt_policy *);
 255 extern int fscrypt_has_permitted_context(struct inode *, struct inode *);
 256 extern int fscrypt_inherit_context(struct inode *, struct inode *,
 257                                         void *, bool);
 258 /* keyinfo.c */
 259 extern int get_crypt_info(struct inode *);
 260 extern int fscrypt_get_encryption_info(struct inode *);
 261 extern void fscrypt_put_encryption_info(struct inode *, struct fscrypt_info *);
 262
 263 /* fname.c */
 264 extern int fscrypt_setup_filename(struct inode *, const struct qstr *,
 265                                 int lookup, struct fscrypt_name *);
 266 extern void fscrypt_free_filename(struct fscrypt_name *);
 267 extern u32 fscrypt_fname_encrypted_size(struct inode *, u32);
 268 extern int fscrypt_fname_alloc_buffer(struct inode *, u32,
 269                                 struct fscrypt_str *);
 270 extern void fscrypt_fname_free_buffer(struct fscrypt_str *);
 271 extern int fscrypt_fname_disk_to_usr(struct inode *, u32, u32,
 272                         const struct fscrypt_str *, struct fscrypt_str *);
 273 extern int fscrypt_fname_usr_to_disk(struct inode *, const struct qstr *,
 274                         struct fscrypt_str *);
 275 #endif
 276
 277 /* crypto.c */
 278 static inline struct fscrypt_ctx *fscrypt_notsupp_get_ctx(struct inode *i,
 279                                                         gfp_t f)
 280 {
 281         return ERR_PTR(-EOPNOTSUPP);
 282 }
 283
 284 static inline void fscrypt_notsupp_release_ctx(struct fscrypt_ctx *c)
 285 {
 286         return;
 287 }
 288
 289 static inline struct page *fscrypt_notsupp_encrypt_page(struct inode *i,
 290                                                 struct page *p, gfp_t f)
 291 {
 292         return ERR_PTR(-EOPNOTSUPP);
 293 }
 294
 295 static inline int fscrypt_notsupp_decrypt_page(struct page *p)
 296 {
 297         return -EOPNOTSUPP;
 298 }
 299
 300 static inline void fscrypt_notsupp_decrypt_bio_pages(struct fscrypt_ctx *c,
 301                                                 struct bio *b)
 302 {
 303         return;
 304 }
 305
 306 static inline void fscrypt_notsupp_pullback_bio_page(struct page **p, bool b)
 307 {
 308         return;
 309 }
 310
 311 static inline void fscrypt_notsupp_restore_control_page(struct page *p)
 312 {
 313         return;
 314 }
 315
 316 static inline int fscrypt_notsupp_zeroout_range(struct inode *i, pgoff_t p,
 317                                         sector_t s, unsigned int f)
 318 {
 319         return -EOPNOTSUPP;
 320 }
 321
 322 /* policy.c */
 323 static inline int fscrypt_notsupp_process_policy(struct file *f,
 324                                 const struct fscrypt_policy *p)
 325 {
 326         return -EOPNOTSUPP;
 327 }
 328
 329 static inline int fscrypt_notsupp_get_policy(struct inode *i,
 330                                 struct fscrypt_policy *p)
 331 {
 332         return -EOPNOTSUPP;
 333 }
 334
 335 static inline int fscrypt_notsupp_has_permitted_context(struct inode *p,
 336                                 struct inode *i)
 337 {
 338         return 0;
 339 }
 340
 341 static inline int fscrypt_notsupp_inherit_context(struct inode *p,
 342                                 struct inode *i, void *v, bool b)
 343 {
 344         return -EOPNOTSUPP;
 345 }
 346
 347 /* keyinfo.c */
 348 static inline int fscrypt_notsupp_get_encryption_info(struct inode *i)
 349 {
 350         return -EOPNOTSUPP;
 351 }
 352
 353 static inline void fscrypt_notsupp_put_encryption_info(struct inode *i,
 354                                         struct fscrypt_info *f)
 355 {
 356         return;
 357 }
 358
 359  /* fname.c */
 360 static inline int fscrypt_notsupp_setup_filename(struct inode *dir,
 361                         const struct qstr *iname,
 362                         int lookup, struct fscrypt_name *fname)
 363 {
 364         if (dir->i_sb->s_cop->is_encrypted(dir))
 365                 return -EOPNOTSUPP;
 366
 367         memset(fname, 0, sizeof(struct fscrypt_name));
 368         fname->usr_fname = iname;
 369         fname->disk_name.name = (unsigned char *)iname->name;
 370         fname->disk_name.len = iname->len;
 371         return 0;
 372 }
 373
 374 static inline void fscrypt_notsupp_free_filename(struct fscrypt_name *fname)
 375 {
 376         return;
 377 }
 378
 379 static inline u32 fscrypt_notsupp_fname_encrypted_size(struct inode *i, u32 s)
 380 {
 381         /* never happens */
 382         WARN_ON(1);
 383         return 0;
 384 }
 385
 386 static inline int fscrypt_notsupp_fname_alloc_buffer(struct inode *inode,
 387                                 u32 ilen, struct fscrypt_str *crypto_str)
 388 {
 389         return -EOPNOTSUPP;
 390 }
 391
 392 static inline void fscrypt_notsupp_fname_free_buffer(struct fscrypt_str *c)
 393 {
 394         return;
 395 }
 396
 397 static inline int fscrypt_notsupp_fname_disk_to_usr(struct inode *inode,
 398                         u32 hash, u32 minor_hash,
 399                         const struct fscrypt_str *iname,
 400                         struct fscrypt_str *oname)
 401 {
 402         return -EOPNOTSUPP;
 403 }
 404
 405 static inline int fscrypt_notsupp_fname_usr_to_disk(struct inode *inode,
 406                         const struct qstr *iname,
 407                         struct fscrypt_str *oname)
 408 {
 409         return -EOPNOTSUPP;
 410 }
 411 #endif  /* _LINUX_FSCRYPTO_H */