LXR linux/fs/ext4/ext4

   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 */
  19struct 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 */
  48struct 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 */
  70struct ext4_encryption_key {
  71        __u32 mode;
  72        char raw[EXT4_MAX_KEY_SIZE];
  73        __u32 size;
  74} __attribute__((__packed__));
  75
  76struct 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
  88struct 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
 104struct 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
 113static 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
 134struct 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 */
 143struct 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 */
 152static 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 */
 160