1 /* 2 * Copyright (C) 2010 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 /* This structure starts 16,384 bytes before the end of a hardware 18 * partition that is encrypted, or in a separate partition. It's location 19 * is specified by a property set in init.<device>.rc. 20 * The structure allocates 48 bytes for a key, but the real key size is 21 * specified in the struct. Currently, the code is hardcoded to use 128 22 * bit keys. 23 * The fields after salt are only valid in rev 1.1 and later stuctures. 24 * Obviously, the filesystem does not include the last 16 kbytes 25 * of the partition if the crypt_mnt_ftr lives at the end of the 26 * partition. 27 */ 28 29 #include <stdbool.h> 30 #include <cutils/properties.h> 31 32 /* The current cryptfs version */ 33 #define CURRENT_MAJOR_VERSION 1 34 #define CURRENT_MINOR_VERSION 3 35 36 #define CRYPT_FOOTER_OFFSET 0x4000 37 #define CRYPT_FOOTER_TO_PERSIST_OFFSET 0x1000 38 #define CRYPT_PERSIST_DATA_SIZE 0x1000 39 40 #define MAX_CRYPTO_TYPE_NAME_LEN 64 41 42 #define MAX_KEY_LEN 48 43 #define SALT_LEN 16 44 #define SCRYPT_LEN 32 45 46 /* definitions of flags in the structure below */ 47 #define CRYPT_MNT_KEY_UNENCRYPTED 0x1 /* The key for the partition is not encrypted. */ 48 #define CRYPT_ENCRYPTION_IN_PROGRESS 0x2 /* Encryption partially completed, 49 encrypted_upto valid*/ 50 #define CRYPT_INCONSISTENT_STATE 0x4 /* Set when starting encryption, clear when 51 exit cleanly, either through success or 52 correctly marked partial encryption */ 53 #define CRYPT_DATA_CORRUPT 0x8 /* Set when encryption is fine, but the 54 underlying volume is corrupt */ 55 #define CRYPT_FORCE_ENCRYPTION 0x10 /* Set when it is time to encrypt this 56 volume on boot. Everything in this 57 structure is set up correctly as 58 though device is encrypted except 59 that the master key is encrypted with the 60 default password. */ 61 #define CRYPT_FORCE_COMPLETE 0x20 /* Set when the above encryption cycle is 62 complete. On next cryptkeeper entry, match 63 the password. If it matches fix the master 64 key and remove this flag. */ 65 66 /* Allowed values for type in the structure below */ 67 #define CRYPT_TYPE_PASSWORD 0 /* master_key is encrypted with a password 68 * Must be zero to be compatible with pre-L 69 * devices where type is always password.*/ 70 #define CRYPT_TYPE_DEFAULT 1 /* master_key is encrypted with default 71 * password */ 72 #define CRYPT_TYPE_PATTERN 2 /* master_key is encrypted with a pattern */ 73 #define CRYPT_TYPE_PIN 3 /* master_key is encrypted with a pin */ 74 #define CRYPT_TYPE_MAX_TYPE 3 /* type cannot be larger than this value */ 75 76 #define CRYPT_MNT_MAGIC 0xD0B5B1C4 77 #define PERSIST_DATA_MAGIC 0xE950CD44 78 79 /* Key Derivation Function algorithms */ 80 #define KDF_PBKDF2 1 81 #define KDF_SCRYPT 2 82 /* Algorithms 3 & 4 deprecated before shipping outside of google, so removed */ 83 #define KDF_SCRYPT_KEYMASTER 5 84 85 /* Maximum allowed keymaster blob size. */ 86 #define KEYMASTER_BLOB_SIZE 2048 87 88 /* __le32 and __le16 defined in system/extras/ext4_utils/ext4_utils.h */ 89 #define __le8 unsigned char 90 91 #if !defined(SHA256_DIGEST_LENGTH) 92 #define SHA256_DIGEST_LENGTH 32 93 #endif 94 95 struct crypt_mnt_ftr { 96 __le32 magic; /* See above */ 97 __le16 major_version; 98 __le16 minor_version; 99 __le32 ftr_size; /* in bytes, not including key following */ 100 __le32 flags; /* See above */ 101 __le32 keysize; /* in bytes */ 102 __le32 crypt_type; /* how master_key is encrypted. Must be a 103 * CRYPT_TYPE_XXX value */ 104 __le64 fs_size; /* Size of the encrypted fs, in 512 byte sectors */ 105 __le32 failed_decrypt_count; /* count of # of failed attempts to decrypt and 106 mount, set to 0 on successful mount */ 107 unsigned char crypto_type_name[MAX_CRYPTO_TYPE_NAME_LEN]; /* The type of encryption 108 needed to decrypt this 109 partition, null terminated */ 110 __le32 spare2; /* ignored */ 111 unsigned char master_key[MAX_KEY_LEN]; /* The encrypted key for decrypting the filesystem */ 112 unsigned char salt[SALT_LEN]; /* The salt used for this encryption */ 113 __le64 persist_data_offset[2]; /* Absolute offset to both copies of crypt_persist_data 114 * on device with that info, either the footer of the 115 * real_blkdevice or the metadata partition. */ 116 117 __le32 persist_data_size; /* The number of bytes allocated to each copy of the 118 * persistent data table*/ 119 120 __le8 kdf_type; /* The key derivation function used. */ 121 122 /* scrypt parameters. See www.tarsnap.com/scrypt/scrypt.pdf */ 123 __le8 N_factor; /* (1 << N) */ 124 __le8 r_factor; /* (1 << r) */ 125 __le8 p_factor; /* (1 << p) */ 126 __le64 encrypted_upto; /* If we are in state CRYPT_ENCRYPTION_IN_PROGRESS and 127 we have to stop (e.g. power low) this is the last 128 encrypted 512 byte sector.*/ 129 __le8 hash_first_block[SHA256_DIGEST_LENGTH]; /* When CRYPT_ENCRYPTION_IN_PROGRESS 130 set, hash of first block, used 131 to validate before continuing*/ 132 133 /* key_master key, used to sign the derived key which is then used to generate 134 * the intermediate key 135 * This key should be used for no other purposes! We use this key to sign unpadded 136 * data, which is acceptable but only if the key is not reused elsewhere. */ 137 __le8 keymaster_blob[KEYMASTER_BLOB_SIZE]; 138 __le32 keymaster_blob_size; 139 140 /* Store scrypt of salted intermediate key. When decryption fails, we can 141 check if this matches, and if it does, we know that the problem is with the 142 drive, and there is no point in asking the user for more passwords. 143 144 Note that if any part of this structure is corrupt, this will not match and 145 we will continue to believe the user entered the wrong password. In that 146 case the only solution is for the user to enter a password enough times to 147 force a wipe. 148 149 Note also that there is no need to worry about migration. If this data is 150 wrong, we simply won't recognise a right password, and will continue to 151 prompt. On the first password change, this value will be populated and 152 then we will be OK. 153 */ 154 unsigned char scrypted_intermediate_key[SCRYPT_LEN]; 155 156 /* sha of this structure with this element set to zero 157 Used when encrypting on reboot to validate structure before doing something 158 fatal 159 */ 160 unsigned char sha256[SHA256_DIGEST_LENGTH]; 161 }; 162 163 /* Persistant data that should be available before decryption. 164 * Things like airplane mode, locale and timezone are kept 165 * here and can be retrieved by the CryptKeeper UI to properly 166 * configure the phone before asking for the password 167 * This is only valid if the major and minor version above 168 * is set to 1.1 or higher. 169 * 170 * This is a 4K structure. There are 2 copies, and the code alternates 171 * writing one and then clearing the previous one. The reading 172 * code reads the first valid copy it finds, based on the magic number. 173 * The absolute offset to the first of the two copies is kept in rev 1.1 174 * and higher crypt_mnt_ftr structures. 175 */ 176 struct crypt_persist_entry { 177 char key[PROPERTY_KEY_MAX]; 178 char val[PROPERTY_VALUE_MAX]; 179 }; 180 181 /* Should be exactly 4K in size */ 182 struct crypt_persist_data { 183 __le32 persist_magic; 184 __le32 persist_valid_entries; 185 __le32 persist_spare[30]; 186 struct crypt_persist_entry persist_entry[0]; 187 }; 188 189 #define DATA_MNT_POINT "/data" 190 191 /* Return values for cryptfs_crypto_complete */ 192 #define CRYPTO_COMPLETE_NOT_ENCRYPTED 1 193 #define CRYPTO_COMPLETE_ENCRYPTED 0 194 #define CRYPTO_COMPLETE_BAD_METADATA (-1) 195 #define CRYPTO_COMPLETE_PARTIAL (-2) 196 #define CRYPTO_COMPLETE_INCONSISTENT (-3) 197 #define CRYPTO_COMPLETE_CORRUPT (-4) 198 199 /* Return values for cryptfs_enable_inplace*() */ 200 #define ENABLE_INPLACE_OK 0 201 #define ENABLE_INPLACE_ERR_OTHER (-1) 202 #define ENABLE_INPLACE_ERR_DEV (-2) /* crypto_blkdev issue */ 203 204 /* Return values for cryptfs_getfield */ 205 #define CRYPTO_GETFIELD_OK 0 206 #define CRYPTO_GETFIELD_ERROR_NO_FIELD (-1) 207 #define CRYPTO_GETFIELD_ERROR_OTHER (-2) 208 #define CRYPTO_GETFIELD_ERROR_BUF_TOO_SMALL (-3) 209 210 /* Return values for cryptfs_setfield */ 211 #define CRYPTO_SETFIELD_OK 0 212 #define CRYPTO_SETFIELD_ERROR_OTHER (-1) 213 #define CRYPTO_SETFIELD_ERROR_FIELD_TOO_LONG (-2) 214 #define CRYPTO_SETFIELD_ERROR_VALUE_TOO_LONG (-3) 215 216 /* Return values for persist_del_key */ 217 #define PERSIST_DEL_KEY_OK 0 218 #define PERSIST_DEL_KEY_ERROR_OTHER (-1) 219 #define PERSIST_DEL_KEY_ERROR_NO_FIELD (-2) 220 221 #ifdef __cplusplus 222 extern "C" { 223 #endif 224 225 int wait_and_unmount(const char *mountpoint, bool kill); 226 227 typedef int (*kdf_func)(const char *passwd, const unsigned char *salt, 228 unsigned char *ikey, void *params); 229 230 int cryptfs_crypto_complete(void); 231 int cryptfs_check_passwd(const char *pw); 232 int cryptfs_verify_passwd(char *newpw); 233 int cryptfs_restart(void); 234 int cryptfs_enable(char *flag, int type, char *passwd, int no_ui); 235 int cryptfs_changepw(int type, const char *newpw); 236 int cryptfs_enable_default(char *flag, int no_ui); 237 int cryptfs_setup_ext_volume(const char* label, const char* real_blkdev, 238 const unsigned char* key, int keysize, char* out_crypto_blkdev); 239 int cryptfs_revert_ext_volume(const char* label); 240 int cryptfs_getfield(const char *fieldname, char *value, int len); 241 int cryptfs_setfield(const char *fieldname, const char *value); 242 int cryptfs_mount_default_encrypted(void); 243 int cryptfs_get_password_type(void); 244 const char* cryptfs_get_password(void); 245 void cryptfs_clear_password(void); 246 int cryptfs_isConvertibleToFBE(void); 247 248 // Functions for file encryption to use to inherit our encryption logic 249 int cryptfs_create_default_ftr(struct crypt_mnt_ftr* ftr, int key_length); 250 int cryptfs_get_master_key(struct crypt_mnt_ftr* ftr, const char* password, 251 unsigned char* master_key); 252 int cryptfs_set_password(struct crypt_mnt_ftr* ftr, const char* password, 253 const unsigned char* master_key); 254 void cryptfs_get_file_encryption_modes(const char **contents_mode_ret, 255 const char **filenames_mode_ret); 256 257 #ifdef __cplusplus 258 } 259 #endif 260
