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
  69struct ext4_encryption_key {
  70        uint32_t mode;
  71        char raw[EXT4_MAX_KEY_SIZE];
  72        uint32_t size;
  73};
  74
  75#define EXT4_CTX_REQUIRES_FREE_ENCRYPT_FL             0x00000001
  76#define EXT4_BOUNCE_PAGE_REQUIRES_FREE_ENCRYPT_FL     0x00000002
  77
  78struct ext4_crypto_ctx {
  79        struct crypto_tfm *tfm;         /* Crypto API context */
  80        struct page *bounce_page;       /* Ciphertext page on write path */
  81        struct page *control_page;      /* Original page on write path */
  82        struct bio *bio;                /* The bio for this context */
  83        struct work_struct work;        /* Work queue for read complete path */
  84        struct list_head free_list;     /* Free list */
  85        int flags;                      /* Flags */
  86        int mode;                       /* Encryption mode for tfm */
  87};
  88
  89struct ext4_completion_result {
  90        struct completion completion;
  91        int res;
  92};
  93
  94#define DECLARE_EXT4_COMPLETION_RESULT(ecr) \
  95        struct ext4_completion_result ecr = { \
  96                COMPLETION_INITIALIZER((ecr).completion), 0 }
  97
  98static inline int ext4_encryption_key_size(int mode)
  99{
 100        switch (mode) {
 101        case EXT4_ENCRYPTION_MODE_AES_256_XTS:
 102                return EXT4_AES_256_XTS_KEY_SIZE;
 103        case EXT4_ENCRYPTION_MODE_AES_256_GCM:
 104                return EXT4_AES_256_GCM_KEY_SIZE;
 105        case EXT4_ENCRYPTION_MODE_AES_256_CBC:
 106                return EXT4_AES_256_CBC_KEY_SIZE;
 107        case EXT4_ENCRYPTION_MODE_AES_256_CTS:
 108                return EXT4_AES_256_CTS_KEY_SIZE;
 109        default:
 110                BUG();
 111        }
 112        return 0;
 113}
 114
 115#define EXT4_FNAME_NUM_SCATTER_ENTRIES  4
 116#define EXT4_CRYPTO_BLOCK_SIZE          16
 117#define EXT4_FNAME_CRYPTO_DIGEST_SIZE   32
 118
 119struct ext4_str {
 120        unsigned char *name;
 121        u32 len;
 122};
 123
 124struct ext4_fname_crypto_ctx {
 125        u32 lim;
 126        char tmp_buf[EXT4_CRYPTO_BLOCK_SIZE];
 127        struct crypto_ablkcipher *ctfm;
 128        struct crypto_hash *htfm;
 129        struct page *workpage;
 130        struct ext4_encryption_key key;
 131        unsigned flags : 8;
 132        unsigned has_valid_key : 1;
 133        unsigned ctfm_key_is_ready : 1;
 134};
 135
 136/**
 137 * For encrypted symlinks, the ciphertext length is stored at the beginning
 138 * of the string in little-endian format.
 139 */
 140struct ext4_encrypted_symlink_data {
 141        __le16 len;
 142        char encrypted_path[1];
 143} __attribute__((__packed__));
 144
 145/**
 146 * This function is used to calculate the disk space required to
 147 * store a filename of length l in encrypted symlink format.
 148 */
 149static inline u32 encrypted_symlink_data_len(u32 l)
 150{
 151        if (l < EXT4_CRYPTO_BLOCK_SIZE)
 152                l = EXT4_CRYPTO_BLOCK_SIZE;
 153        return (l + sizeof(struct ext4_encrypted_symlink_data) - 1);
 154}
 155
 156#endif  /* _EXT4_CRYPTO_H */
 157