include/linux/fscrypt_common.h

   1 /*
   2  * fscrypt_common.h: common declarations for per-file encryption
   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_FSCRYPT_COMMON_H
  11 #define _LINUX_FSCRYPT_COMMON_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_CRYPTO_BLOCK_SIZE            16
  22
  23 struct fscrypt_info;
  24
  25 struct fscrypt_ctx {
  26         union {
  27                 struct {
  28                         struct page *bounce_page;       /* Ciphertext page */
  29                         struct page *control_page;      /* Original page  */
  30                 } w;
  31                 struct {
  32                         struct bio *bio;
  33                         struct work_struct work;
  34                 } r;
  35                 struct list_head free_list;     /* Free list */
  36         };
  37         u8 flags;                               /* Flags */
  38 };
  39
  40 /**
  41  * For encrypted symlinks, the ciphertext length is stored at the beginning
  42  * of the string in little-endian format.
  43  */
  44 struct fscrypt_symlink_data {
  45         __le16 len;
  46         char encrypted_path[1];
  47 } __packed;
  48
  49 /**
  50  * This function is used to calculate the disk space required to
  51  * store a filename of length l in encrypted symlink format.
  52  */
  53 static inline u32 fscrypt_symlink_data_len(u32 l)
  54 {
  55         if (l < FS_CRYPTO_BLOCK_SIZE)
  56                 l = FS_CRYPTO_BLOCK_SIZE;
  57         return (l + sizeof(struct fscrypt_symlink_data) - 1);
  58 }
  59
  60 struct fscrypt_str {
  61         unsigned char *name;
  62         u32 len;
  63 };
  64
  65 struct fscrypt_name {
  66         const struct qstr *usr_fname;
  67         struct fscrypt_str disk_name;
  68         u32 hash;
  69         u32 minor_hash;
  70         struct fscrypt_str crypto_buf;
  71 };
  72
  73 #define FSTR_INIT(n, l)         { .name = n, .len = l }
  74 #define FSTR_TO_QSTR(f)         QSTR_INIT((f)->name, (f)->len)
  75 #define fname_name(p)           ((p)->disk_name.name)
  76 #define fname_len(p)            ((p)->disk_name.len)
  77
  78 /*
  79  * fscrypt superblock flags
  80  */
  81 #define FS_CFLG_OWN_PAGES (1U << 1)
  82
  83 /*
  84  * crypto opertions for filesystems
  85  */
  86 struct fscrypt_operations {
  87         unsigned int flags;
  88         const char *key_prefix;
  89         int (*get_context)(struct inode *, void *, size_t);
  90         int (*set_context)(struct inode *, const void *, size_t, void *);
  91         int (*dummy_context)(struct inode *);
  92         bool (*is_encrypted)(struct inode *);
  93         bool (*empty_dir)(struct inode *);
  94         unsigned (*max_namelen)(struct inode *);
  95 };
  96
  97 static inline bool fscrypt_dummy_context_enabled(struct inode *inode)
  98 {
  99         if (inode->i_sb->s_cop->dummy_context &&
 100                                 inode->i_sb->s_cop->dummy_context(inode))
 101                 return true;
 102         return false;
 103 }
 104
 105 static inline bool fscrypt_valid_contents_enc_mode(u32 mode)
 106 {
 107         return (mode == FS_ENCRYPTION_MODE_AES_256_XTS);
 108 }
 109
 110 static inline bool fscrypt_valid_filenames_enc_mode(u32 mode)
 111 {
 112         return (mode == FS_ENCRYPTION_MODE_AES_256_CTS);
 113 }
 114
 115 static inline bool fscrypt_is_dot_dotdot(const struct qstr *str)
 116 {
 117         if (str->len == 1 && str->name[0] == '.')
 118                 return true;
 119
 120         if (str->len == 2 && str->name[0] == '.' && str->name[1] == '.')
 121                 return true;
 122
 123         return false;
 124 }
 125
 126 static inline struct page *fscrypt_control_page(struct page *page)
 127 {
 128 #if IS_ENABLED(CONFIG_FS_ENCRYPTION)
 129         return ((struct fscrypt_ctx *)page_private(page))->w.control_page;
 130 #else
 131         WARN_ON_ONCE(1);
 132         return ERR_PTR(-EINVAL);
 133 #endif
 134 }
 135
 136 static inline int fscrypt_has_encryption_key(const struct inode *inode)
 137 {
 138 #if IS_ENABLED(CONFIG_FS_ENCRYPTION)
 139         return (inode->i_crypt_info != NULL);
 140 #else
 141         return 0;
 142 #endif
 143 }
 144
 145 #endif  /* _LINUX_FSCRYPT_COMMON_H */