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  * fscrypt superblock flags
 158  */
 159 #define FS_CFLG_INPLACE_ENCRYPTION (1U << 1)
 160
 161 /*
 162  * crypto opertions for filesystems
 163  */
 164 struct fscrypt_operations {
 165         unsigned int flags;
 166         int (*get_context)(struct inode *, void *, size_t);
 167         int (*key_prefix)(struct inode *, u8 **);
 168         int (*prepare_context)(struct inode *);
 169         int (*set_context)(struct inode *, const void *, size_t, void *);
 170         int (*dummy_context)(struct inode *);
 171         bool (*is_encrypted)(struct inode *);
 172         bool (*empty_dir)(struct inode *);
 173         unsigned (*max_namelen)(struct inode *);
 174 };
 175
 176 static inline bool fscrypt_dummy_context_enabled(struct inode *inode)
 177 {
 178         if (inode->i_sb->s_cop->dummy_context &&
 179                                 inode->i_sb->s_cop->dummy_context(inode))
 180                 return true;
 181         return false;
 182 }
 183
 184 static inline bool fscrypt_valid_contents_enc_mode(u32 mode)
 185 {
 186         return (mode == FS_ENCRYPTION_MODE_AES_256_XTS);
 187 }
 188
 189 static inline bool fscrypt_valid_filenames_enc_mode(u32 mode)
 190 {
 191         return (mode == FS_ENCRYPTION_MODE_AES_256_CTS);
 192 }
 193
 194 static inline bool fscrypt_is_dot_dotdot(const struct qstr *str)
 195 {
 196         if (str->len == 1 && str->name[0] == '.')
 197                 return true;
 198
 199         if (str->len == 2 && str->name[0] == '.' && str->name[1] == '.')
 200                 return true;
 201
 202         return false;
 203 }
 204
 205 static inline struct page *fscrypt_control_page(struct page *page)
 206 {
 207 #if IS_ENABLED(CONFIG_FS_ENCRYPTION)
 208         return ((struct fscrypt_ctx *)page_private(page))->w.control_page;
 209 #else
 210         WARN_ON_ONCE(1);
 211         return ERR_PTR(-EINVAL);
 212 #endif
 213 }
 214
 215 static inline int fscrypt_has_encryption_key(const struct inode *inode)
 216 {
 217 #if IS_ENABLED(CONFIG_FS_ENCRYPTION)
 218         return (inode->i_crypt_info != NULL);
 219 #else
 220         return 0;
 221 #endif
 222 }
 223
 224 static inline void fscrypt_set_encrypted_dentry(struct dentry *dentry)
 225 {
 226 #if IS_ENABLED(CONFIG_FS_ENCRYPTION)
 227         spin_lock(&dentry->d_lock);
 228         dentry->d_flags |= DCACHE_ENCRYPTED_WITH_KEY;
 229         spin_unlock(&dentry->d_lock);
 230 #endif
 231 }
 232
 233 #if IS_ENABLED(CONFIG_FS_ENCRYPTION)
 234 extern const struct dentry_operations fscrypt_d_ops;
 235 #endif
 236
 237 static inline void fscrypt_set_d_op(struct dentry *dentry)
 238 {
 239 #if IS_ENABLED(CONFIG_FS_ENCRYPTION)
 240         d_set_d_op(dentry, &fscrypt_d_ops);
 241 #endif
 242 }
 243
 244 #if IS_ENABLED(CONFIG_FS_ENCRYPTION)
 245 /* crypto.c */
 246 extern struct kmem_cache *fscrypt_info_cachep;
 247
 248 extern struct fscrypt_ctx *fscrypt_get_ctx(const struct inode *, gfp_t);
 249 extern void fscrypt_release_ctx(struct fscrypt_ctx *);
 250 extern struct page *fscrypt_encrypt_page(const struct inode *, struct page *,
 251                                                 unsigned int, unsigned int,
 252                                                 pgoff_t, gfp_t);
 253 extern int fscrypt_decrypt_page(const struct inode *, struct page *, unsigned int,
 254                                 unsigned int, pgoff_t);
 255 extern void fscrypt_decrypt_bio_pages(struct fscrypt_ctx *, struct bio *);
 256 extern void fscrypt_pullback_bio_page(struct page **, bool);
 257 extern void fscrypt_restore_control_page(struct page *);
 258 extern int fscrypt_zeroout_range(const struct inode *, pgoff_t, sector_t,
 259                                                 unsigned int);
 260 /* policy.c */
 261 extern int fscrypt_ioctl_set_policy(struct file *, const void __user *);
 262 extern int fscrypt_ioctl_get_policy(struct file *, void __user *);
 263 extern int fscrypt_has_permitted_context(struct inode *, struct inode *);
 264 extern int fscrypt_inherit_context(struct inode *, struct inode *,
 265                                         void *, bool);
 266 /* keyinfo.c */
 267 extern int fscrypt_get_encryption_info(struct inode *);
 268 extern void fscrypt_put_encryption_info(struct inode *, struct fscrypt_info *);
 269
 270 /* fname.c */
 271 extern int fscrypt_setup_filename(struct inode *, const struct qstr *,
 272                                 int lookup, struct fscrypt_name *);
 273 extern void fscrypt_free_filename(struct fscrypt_name *);
 274 extern u32 fscrypt_fname_encrypted_size(const struct inode *, u32);
 275 extern int fscrypt_fname_alloc_buffer(const struct inode *, u32,
 276                                 struct fscrypt_str *);
 277 extern void fscrypt_fname_free_buffer(struct fscrypt_str *);
 278 extern int fscrypt_fname_disk_to_usr(struct inode *, u32, u32,
 279                         const struct fscrypt_str *, struct fscrypt_str *);
 280 extern int fscrypt_fname_usr_to_disk(struct inode *, const struct qstr *,
 281                         struct fscrypt_str *);
 282 #endif
 283
 284 /* crypto.c */
 285 static inline struct fscrypt_ctx *fscrypt_notsupp_get_ctx(const struct inode *i,
 286                                                         gfp_t f)
 287 {
 288         return ERR_PTR(-EOPNOTSUPP);
 289 }
 290
 291 static inline void fscrypt_notsupp_release_ctx(struct fscrypt_ctx *c)
 292 {
 293         return;
 294 }
 295
 296 static inline struct page *fscrypt_notsupp_encrypt_page(const struct inode *i,
 297                                                 struct page *p,
 298                                                 unsigned int len,
 299                                                 unsigned int offs,
 300                                                 pgoff_t index, gfp_t f)
 301 {
 302         return ERR_PTR(-EOPNOTSUPP);
 303 }
 304
 305 static inline int fscrypt_notsupp_decrypt_page(const struct inode *i, struct page *p,
 306                                                 unsigned int len, unsigned int offs,
 307                                                 pgoff_t index)
 308 {
 309         return -EOPNOTSUPP;
 310 }
 311
 312 static inline void fscrypt_notsupp_decrypt_bio_pages(struct fscrypt_ctx *c,
 313                                                 struct bio *b)
 314 {
 315         return;
 316 }
 317
 318 static inline void fscrypt_notsupp_pullback_bio_page(struct page **p, bool b)
 319 {
 320         return;
 321 }
 322
 323 static inline void fscrypt_notsupp_restore_control_page(struct page *p)
 324 {
 325         return;
 326 }
 327
 328 static inline int fscrypt_notsupp_zeroout_range(const struct inode *i, pgoff_t p,
 329                                         sector_t s, unsigned int f)
 330 {
 331         return -EOPNOTSUPP;
 332 }
 333
 334 /* policy.c */
 335 static inline int fscrypt_notsupp_ioctl_set_policy(struct file *f,
 336                                 const void __user *arg)
 337 {
 338         return -EOPNOTSUPP;
 339 }
 340
 341 static inline int fscrypt_notsupp_ioctl_get_policy(struct file *f,
 342                                 void __user *arg)
 343 {
 344         return -EOPNOTSUPP;
 345 }
 346
 347 static inline int fscrypt_notsupp_has_permitted_context(struct inode *p,
 348                                 struct inode *i)
 349 {
 350         return 0;
 351 }
 352
 353 static inline int fscrypt_notsupp_inherit_context(struct inode *p,
 354                                 struct inode *i, void *v, bool b)
 355 {
 356         return -EOPNOTSUPP;
 357 }
 358
 359 /* keyinfo.c */
 360 static inline int fscrypt_notsupp_get_encryption_info(struct inode *i)
 361 {
 362         return -EOPNOTSUPP;
 363 }
 364
 365 static inline void fscrypt_notsupp_put_encryption_info(struct inode *i,
 366                                         struct fscrypt_info *f)
 367 {
 368         return;
 369 }
 370
 371  /* fname.c */
 372 static inline int fscrypt_notsupp_setup_filename(struct inode *dir,
 373                         const struct qstr *iname,
 374                         int lookup, struct fscrypt_name *fname)
 375 {
 376         if (dir->i_sb->s_cop->is_encrypted(dir))
 377                 return -EOPNOTSUPP;
 378
 379         memset(fname, 0, sizeof(struct fscrypt_name));
 380         fname->usr_fname = iname;
 381         fname->disk_name.name = (unsigned char *)iname->name;
 382         fname->disk_name.len = iname->len;
 383         return 0;
 384 }
 385
 386 static inline void fscrypt_notsupp_free_filename(struct fscrypt_name *fname)
 387 {
 388         return;
 389 }
 390
 391 static inline u32 fscrypt_notsupp_fname_encrypted_size(struct inode *i, u32 s)
 392 {
 393         /* never happens */
 394         WARN_ON(1);
 395         return 0;
 396 }
 397
 398 static inline int fscrypt_notsupp_fname_alloc_buffer(struct inode *inode,
 399                                 u32 ilen, struct fscrypt_str *crypto_str)
 400 {
 401         return -EOPNOTSUPP;
 402 }
 403
 404 static inline void fscrypt_notsupp_fname_free_buffer(struct fscrypt_str *c)
 405 {
 406         return;
 407 }
 408
 409 static inline int fscrypt_notsupp_fname_disk_to_usr(struct inode *inode,
 410                         u32 hash, u32 minor_hash,
 411                         const struct fscrypt_str *iname,
 412                         struct fscrypt_str *oname)
 413 {
 414         return -EOPNOTSUPP;
 415 }
 416
 417 static inline int fscrypt_notsupp_fname_usr_to_disk(struct inode *inode,
 418                         const struct qstr *iname,
 419                         struct fscrypt_str *oname)
 420 {
 421         return -EOPNOTSUPP;
 422 }
 423 #endif  /* _LINUX_FSCRYPTO_H */