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         unsigned char   ci_size;
  78         char            ci_data_mode;
  79         char            ci_filename_mode;
  80         char            ci_flags;
  81         struct crypto_ablkcipher *ci_ctfm;
  82         struct key      *ci_keyring_key;
  83         char            ci_raw[EXT4_MAX_KEY_SIZE];
  84         char            ci_master_key[EXT4_KEY_DESCRIPTOR_SIZE];
  85 };
  86
  87 #define EXT4_CTX_REQUIRES_FREE_ENCRYPT_FL             0x00000001
  88 #define EXT4_BOUNCE_PAGE_REQUIRES_FREE_ENCRYPT_FL     0x00000002
  89 #define EXT4_WRITE_PATH_FL                            0x00000004
  90
  91 struct ext4_crypto_ctx {
  92         struct crypto_tfm *tfm;         /* Crypto API context */
  93         union {
  94                 struct {
  95                         struct page *bounce_page;       /* Ciphertext page */
  96                         struct page *control_page;      /* Original page  */
  97                 } w;
  98                 struct {
  99                         struct bio *bio;
 100                         struct work_struct work;
 101                 } r;
 102                 struct list_head free_list;     /* Free list */
 103         };
 104         char flags;                      /* Flags */
 105         char mode;                       /* Encryption mode for tfm */
 106 };
 107
 108 struct ext4_completion_result {
 109         struct completion completion;
 110         int res;
 111 };
 112
 113 #define DECLARE_EXT4_COMPLETION_RESULT(ecr) \
 114         struct ext4_completion_result ecr = { \
 115                 COMPLETION_INITIALIZER((ecr).completion), 0 }
 116
 117 static inline int ext4_encryption_key_size(int mode)
 118 {
 119         switch (mode) {
 120         case EXT4_ENCRYPTION_MODE_AES_256_XTS:
 121                 return EXT4_AES_256_XTS_KEY_SIZE;
 122         case EXT4_ENCRYPTION_MODE_AES_256_GCM:
 123                 return EXT4_AES_256_GCM_KEY_SIZE;
 124         case EXT4_ENCRYPTION_MODE_AES_256_CBC:
 125                 return EXT4_AES_256_CBC_KEY_SIZE;
 126         case EXT4_ENCRYPTION_MODE_AES_256_CTS:
 127                 return EXT4_AES_256_CTS_KEY_SIZE;
 128         default:
 129                 BUG();
 130         }
 131         return 0;
 132 }
 133
 134 #define EXT4_FNAME_NUM_SCATTER_ENTRIES  4
 135 #define EXT4_CRYPTO_BLOCK_SIZE          16
 136 #define EXT4_FNAME_CRYPTO_DIGEST_SIZE   32
 137
 138 struct ext4_str {
 139         unsigned char *name;
 140         u32 len;
 141 };
 142
 143 /**
 144  * For encrypted symlinks, the ciphertext length is stored at the beginning
 145  * of the string in little-endian format.
 146  */
 147 struct ext4_encrypted_symlink_data {
 148         __le16 len;
 149         char encrypted_path[1];
 150 } __attribute__((__packed__));
 151
 152 /**
 153  * This function is used to calculate the disk space required to
 154  * store a filename of length l in encrypted symlink format.
 155  */
 156 static inline u32 encrypted_symlink_data_len(u32 l)
 157 {
 158         if (l < EXT4_CRYPTO_BLOCK_SIZE)
 159                 l = EXT4_CRYPTO_BLOCK_SIZE;
 160         return (l + sizeof(struct ext4_encrypted_symlink_data) - 1);
 161 }
 162
 163 #endif  /* _EXT4_CRYPTO_H */