fs/ext4/ext4_crypto.h

   1 /*
   2  * linux/fs/ext4/ext4_crypto.h
   3  *
   4  * Copyright (C) 2015, Google, Inc.
   5  *
   6  * This contains encryption header content for ext4
   7  *
   8  * Written by Michael Halcrow, 2015.
   9  */
  10
  11 #ifndef _EXT4_CRYPTO_H
  12 #define _EXT4_CRYPTO_H
  13
  14 #include <linux/fs.h>
  15
  16 #define EXT4_KEY_DESCRIPTOR_SIZE 8
  17
  18 /* Policy provided via an ioctl on the topmost directory */
  19 struct ext4_encryption_policy {
  20         char version;
  21         char contents_encryption_mode;
  22         char filenames_encryption_mode;
  23         char flags;
  24         char master_key_descriptor[EXT4_KEY_DESCRIPTOR_SIZE];
  25 } __attribute__((__packed__));
  26
  27 #define EXT4_ENCRYPTION_CONTEXT_FORMAT_V1 1
  28 #define EXT4_KEY_DERIVATION_NONCE_SIZE 16
  29
  30 #define EXT4_POLICY_FLAGS_PAD_4         0x00
  31 #define EXT4_POLICY_FLAGS_PAD_8         0x01
  32 #define EXT4_POLICY_FLAGS_PAD_16        0x02
  33 #define EXT4_POLICY_FLAGS_PAD_32        0x03
  34 #define EXT4_POLICY_FLAGS_PAD_MASK      0x03
  35 #define EXT4_POLICY_FLAGS_VALID         0x03
  36
  37 /**
  38  * Encryption context for inode
  39  *
  40  * Protector format:
  41  *  1 byte: Protector format (1 = this version)
  42  *  1 byte: File contents encryption mode
  43  *  1 byte: File names encryption mode
  44  *  1 byte: Reserved
  45  *  8 bytes: Master Key descriptor
  46  *  16 bytes: Encryption Key derivation nonce
  47  */
  48 struct ext4_encryption_context {
  49         char format;
  50         char contents_encryption_mode;
  51         char filenames_encryption_mode;
  52         char flags;
  53         char master_key_descriptor[EXT4_KEY_DESCRIPTOR_SIZE];
  54         char nonce[EXT4_KEY_DERIVATION_NONCE_SIZE];
  55 } __attribute__((__packed__));
  56
  57 /* Encryption parameters */
  58 #define EXT4_XTS_TWEAK_SIZE 16
  59 #define EXT4_AES_128_ECB_KEY_SIZE 16
  60 #define EXT4_AES_256_GCM_KEY_SIZE 32
  61 #define EXT4_AES_256_CBC_KEY_SIZE 32
  62 #define EXT4_AES_256_CTS_KEY_SIZE 32
  63 #define EXT4_AES_256_XTS_KEY_SIZE 64
  64 #define EXT4_MAX_KEY_SIZE 64
  65
  66 #define EXT4_KEY_DESC_PREFIX "ext4:"
  67 #define EXT4_KEY_DESC_PREFIX_SIZE 5
  68
  69 /* This is passed in from userspace into the kernel keyring */
  70 struct ext4_encryption_key {
  71         __u32 mode;
  72         char raw[EXT4_MAX_KEY_SIZE];
  73         __u32 size;
  74 } __attribute__((__packed__));
  75
  76 struct ext4_crypt_info {
  77         char            ci_data_mode;
  78         char            ci_filename_mode;
  79         char            ci_flags;
  80         struct crypto_skcipher *ci_ctfm;
  81         struct key      *ci_keyring_key;
  82         char            ci_master_key[EXT4_KEY_DESCRIPTOR_SIZE];
  83 };
  84
  85 #define EXT4_CTX_REQUIRES_FREE_ENCRYPT_FL             0x00000001
  86 #define EXT4_WRITE_PATH_FL                            0x00000002
  87
  88 struct ext4_crypto_ctx {
  89         union {
  90                 struct {
  91                         struct page *bounce_page;       /* Ciphertext page */
  92                         struct page *control_page;      /* Original page  */
  93                 } w;
  94                 struct {
  95                         struct bio *bio;
  96                         struct work_struct work;
  97                 } r;
  98                 struct list_head free_list;     /* Free list */
  99         };
 100         char flags;                      /* Flags */
 101         char mode;                       /* Encryption mode for tfm */
 102 };
 103
 104 struct ext4_completion_result {
 105         struct completion completion;
 106         int res;
 107 };
 108
 109 #define DECLARE_EXT4_COMPLETION_RESULT(ecr) \
 110         struct ext4_completion_result ecr = { \
 111                 COMPLETION_INITIALIZER((ecr).completion), 0 }
 112
 113 static inline int ext4_encryption_key_size(int mode)
 114 {
 115         switch (mode) {
 116         case EXT4_ENCRYPTION_MODE_AES_256_XTS:
 117                 return EXT4_AES_256_XTS_KEY_SIZE;
 118         case EXT4_ENCRYPTION_MODE_AES_256_GCM:
 119                 return EXT4_AES_256_GCM_KEY_SIZE;
 120         case EXT4_ENCRYPTION_MODE_AES_256_CBC:
 121                 return EXT4_AES_256_CBC_KEY_SIZE;
 122         case EXT4_ENCRYPTION_MODE_AES_256_CTS:
 123                 return EXT4_AES_256_CTS_KEY_SIZE;
 124         default:
 125                 BUG();
 126         }
 127         return 0;
 128 }
 129
 130 #define EXT4_FNAME_NUM_SCATTER_ENTRIES  4
 131 #define EXT4_CRYPTO_BLOCK_SIZE          16
 132 #define EXT4_FNAME_CRYPTO_DIGEST_SIZE   32
 133
 134 struct ext4_str {
 135         unsigned char *name;
 136         u32 len;
 137 };
 138
 139 /**
 140  * For encrypted symlinks, the ciphertext length is stored at the beginning
 141  * of the string in little-endian format.
 142  */
 143 struct ext4_encrypted_symlink_data {
 144         __le16 len;
 145         char encrypted_path[1];
 146 } __attribute__((__packed__));
 147
 148 /**
 149  * This function is used to calculate the disk space required to
 150  * store a filename of length l in encrypted symlink format.
 151  */
 152 static inline u32 encrypted_symlink_data_len(u32 l)
 153 {
 154         if (l < EXT4_CRYPTO_BLOCK_SIZE)
 155                 l = EXT4_CRYPTO_BLOCK_SIZE;
 156         return (l + sizeof(struct ext4_encrypted_symlink_data) - 1);
 157 }
 158
 159 #endif  /* _EXT4_CRYPTO_H */