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 master_key_descriptor[EXT4_KEY_DESCRIPTOR_SIZE];
  24 } __attribute__((__packed__));
  25
  26 #define EXT4_ENCRYPTION_CONTEXT_FORMAT_V1 1
  27 #define EXT4_KEY_DERIVATION_NONCE_SIZE 16
  28
  29 /**
  30  * Encryption context for inode
  31  *
  32  * Protector format:
  33  *  1 byte: Protector format (1 = this version)
  34  *  1 byte: File contents encryption mode
  35  *  1 byte: File names encryption mode
  36  *  1 byte: Reserved
  37  *  8 bytes: Master Key descriptor
  38  *  16 bytes: Encryption Key derivation nonce
  39  */
  40 struct ext4_encryption_context {
  41         char format;
  42         char contents_encryption_mode;
  43         char filenames_encryption_mode;
  44         char reserved;
  45         char master_key_descriptor[EXT4_KEY_DESCRIPTOR_SIZE];
  46         char nonce[EXT4_KEY_DERIVATION_NONCE_SIZE];
  47 } __attribute__((__packed__));
  48
  49 /* Encryption parameters */
  50 #define EXT4_XTS_TWEAK_SIZE 16
  51 #define EXT4_AES_128_ECB_KEY_SIZE 16
  52 #define EXT4_AES_256_GCM_KEY_SIZE 32
  53 #define EXT4_AES_256_CBC_KEY_SIZE 32
  54 #define EXT4_AES_256_CTS_KEY_SIZE 32
  55 #define EXT4_AES_256_XTS_KEY_SIZE 64
  56 #define EXT4_MAX_KEY_SIZE 64
  57
  58 #define EXT4_KEY_DESC_PREFIX "ext4:"
  59 #define EXT4_KEY_DESC_PREFIX_SIZE 5
  60
  61 struct ext4_encryption_key {
  62         uint32_t mode;
  63         char raw[EXT4_MAX_KEY_SIZE];
  64         uint32_t size;
  65 };
  66
  67 #define EXT4_CTX_REQUIRES_FREE_ENCRYPT_FL             0x00000001
  68 #define EXT4_BOUNCE_PAGE_REQUIRES_FREE_ENCRYPT_FL     0x00000002
  69
  70 struct ext4_crypto_ctx {
  71         struct crypto_tfm *tfm;         /* Crypto API context */
  72         struct page *bounce_page;       /* Ciphertext page on write path */
  73         struct page *control_page;      /* Original page on write path */
  74         struct bio *bio;                /* The bio for this context */
  75         struct work_struct work;        /* Work queue for read complete path */
  76         struct list_head free_list;     /* Free list */
  77         int flags;                      /* Flags */
  78         int mode;                       /* Encryption mode for tfm */
  79 };
  80
  81 struct ext4_completion_result {
  82         struct completion completion;
  83         int res;
  84 };
  85
  86 #define DECLARE_EXT4_COMPLETION_RESULT(ecr) \
  87         struct ext4_completion_result ecr = { \
  88                 COMPLETION_INITIALIZER((ecr).completion), 0 }
  89
  90 static inline int ext4_encryption_key_size(int mode)
  91 {
  92         switch (mode) {
  93         case EXT4_ENCRYPTION_MODE_AES_256_XTS:
  94                 return EXT4_AES_256_XTS_KEY_SIZE;
  95         case EXT4_ENCRYPTION_MODE_AES_256_GCM:
  96                 return EXT4_AES_256_GCM_KEY_SIZE;
  97         case EXT4_ENCRYPTION_MODE_AES_256_CBC:
  98                 return EXT4_AES_256_CBC_KEY_SIZE;
  99         case EXT4_ENCRYPTION_MODE_AES_256_CTS:
 100                 return EXT4_AES_256_CTS_KEY_SIZE;
 101         default:
 102                 BUG();
 103         }
 104         return 0;
 105 }
 106
 107 #define EXT4_FNAME_NUM_SCATTER_ENTRIES  4
 108 #define EXT4_CRYPTO_BLOCK_SIZE          16
 109 #define EXT4_FNAME_CRYPTO_DIGEST_SIZE   32
 110
 111 struct ext4_str {
 112         unsigned char *name;
 113         u32 len;
 114 };
 115
 116 struct ext4_fname_crypto_ctx {
 117         u32 lim;
 118         char tmp_buf[EXT4_CRYPTO_BLOCK_SIZE];
 119         struct crypto_ablkcipher *ctfm;
 120         struct crypto_hash *htfm;
 121         struct page *workpage;
 122         struct ext4_encryption_key key;
 123         unsigned has_valid_key : 1;
 124         unsigned ctfm_key_is_ready : 1;
 125 };
 126
 127 /**
 128  * For encrypted symlinks, the ciphertext length is stored at the beginning
 129  * of the string in little-endian format.
 130  */
 131 struct ext4_encrypted_symlink_data {
 132         __le16 len;
 133         char encrypted_path[1];
 134 } __attribute__((__packed__));
 135
 136 /**
 137  * This function is used to calculate the disk space required to
 138  * store a filename of length l in encrypted symlink format.
 139  */
 140 static inline u32 encrypted_symlink_data_len(u32 l)
 141 {
 142         if (l < EXT4_CRYPTO_BLOCK_SIZE)
 143                 l = EXT4_CRYPTO_BLOCK_SIZE;
 144         return (l + sizeof(struct ext4_encrypted_symlink_data) - 1);
 145 }
 146
 147 #endif  /* _EXT4_CRYPTO_H */