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_ablkcipher *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 ext4_encryption_key_size(int mode)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 32 133 134 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 */ encrypted_symlink_data_len(u32 l)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