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 56 /* Allowed values for type in the structure below */ 57 #define CRYPT_TYPE_PASSWORD 0 /* master_key is encrypted with a password 58 * Must be zero to be compatible with pre-L 59 * devices where type is always password.*/ 60 #define CRYPT_TYPE_DEFAULT 1 /* master_key is encrypted with default 61 * password */ 62 #define CRYPT_TYPE_PATTERN 2 /* master_key is encrypted with a pattern */ 63 #define CRYPT_TYPE_PIN 3 /* master_key is encrypted with a pin */ 64 #define CRYPT_TYPE_MAX_TYPE 3 /* type cannot be larger than this value */ 65 66 #define CRYPT_MNT_MAGIC 0xD0B5B1C4 67 #define PERSIST_DATA_MAGIC 0xE950CD44 68 69 #define SCRYPT_PROP "ro.crypto.scrypt_params" 70 #define SCRYPT_DEFAULTS { 15, 3, 1 } 71 72 /* Key Derivation Function algorithms */ 73 #define KDF_PBKDF2 1 74 #define KDF_SCRYPT 2 75 /* Algorithms 3 & 4 deprecated before shipping outside of google, so removed */ 76 #define KDF_SCRYPT_KEYMASTER 5 77 78 /* Maximum allowed keymaster blob size. */ 79 #define KEYMASTER_BLOB_SIZE 2048 80 81 /* __le32 and __le16 defined in system/extras/ext4_utils/ext4_utils.h */ 82 #define __le8 unsigned char 83 84 #if !defined(SHA256_DIGEST_LENGTH) 85 #define SHA256_DIGEST_LENGTH 32 86 #endif 87 88 struct crypt_mnt_ftr { 89 __le32 magic; /* See above */ 90 __le16 major_version; 91 __le16 minor_version; 92 __le32 ftr_size; /* in bytes, not including key following */ 93 __le32 flags; /* See above */ 94 __le32 keysize; /* in bytes */ 95 __le32 crypt_type; /* how master_key is encrypted. Must be a 96 * CRYPT_TYPE_XXX value */ 97 __le64 fs_size; /* Size of the encrypted fs, in 512 byte sectors */ 98 __le32 failed_decrypt_count; /* count of # of failed attempts to decrypt and 99 mount, set to 0 on successful mount */ 100 unsigned char crypto_type_name[MAX_CRYPTO_TYPE_NAME_LEN]; /* The type of encryption 101 needed to decrypt this 102 partition, null terminated */ 103 __le32 spare2; /* ignored */ 104 unsigned char master_key[MAX_KEY_LEN]; /* The encrypted key for decrypting the filesystem */ 105 unsigned char salt[SALT_LEN]; /* The salt used for this encryption */ 106 __le64 persist_data_offset[2]; /* Absolute offset to both copies of crypt_persist_data 107 * on device with that info, either the footer of the 108 * real_blkdevice or the metadata partition. */ 109 110 __le32 persist_data_size; /* The number of bytes allocated to each copy of the 111 * persistent data table*/ 112 113 __le8 kdf_type; /* The key derivation function used. */ 114 115 /* scrypt parameters. See www.tarsnap.com/scrypt/scrypt.pdf */ 116 __le8 N_factor; /* (1 << N) */ 117 __le8 r_factor; /* (1 << r) */ 118 __le8 p_factor; /* (1 << p) */ 119 __le64 encrypted_upto; /* If we are in state CRYPT_ENCRYPTION_IN_PROGRESS and 120 we have to stop (e.g. power low) this is the last 121 encrypted 512 byte sector.*/ 122 __le8 hash_first_block[SHA256_DIGEST_LENGTH]; /* When CRYPT_ENCRYPTION_IN_PROGRESS 123 set, hash of first block, used 124 to validate before continuing*/ 125 126 /* key_master key, used to sign the derived key which is then used to generate 127 * the intermediate key 128 * This key should be used for no other purposes! We use this key to sign unpadded 129 * data, which is acceptable but only if the key is not reused elsewhere. */ 130 __le8 keymaster_blob[KEYMASTER_BLOB_SIZE]; 131 __le32 keymaster_blob_size; 132 133 /* Store scrypt of salted intermediate key. When decryption fails, we can 134 check if this matches, and if it does, we know that the problem is with the 135 drive, and there is no point in asking the user for more passwords. 136 137 Note that if any part of this structure is corrupt, this will not match and 138 we will continue to believe the user entered the wrong password. In that 139 case the only solution is for the user to enter a password enough times to 140 force a wipe. 141 142 Note also that there is no need to worry about migration. If this data is 143 wrong, we simply won't recognise a right password, and will continue to 144 prompt. On the first password change, this value will be populated and 145 then we will be OK. 146 */ 147 unsigned char scrypted_intermediate_key[SCRYPT_LEN]; 148 }; 149 150 /* Persistant data that should be available before decryption. 151 * Things like airplane mode, locale and timezone are kept 152 * here and can be retrieved by the CryptKeeper UI to properly 153 * configure the phone before asking for the password 154 * This is only valid if the major and minor version above 155 * is set to 1.1 or higher. 156 * 157 * This is a 4K structure. There are 2 copies, and the code alternates 158 * writing one and then clearing the previous one. The reading 159 * code reads the first valid copy it finds, based on the magic number. 160 * The absolute offset to the first of the two copies is kept in rev 1.1 161 * and higher crypt_mnt_ftr structures. 162 */ 163 struct crypt_persist_entry { 164 char key[PROPERTY_KEY_MAX]; 165 char val[PROPERTY_VALUE_MAX]; 166 }; 167 168 /* Should be exactly 4K in size */ 169 struct crypt_persist_data { 170 __le32 persist_magic; 171 __le32 persist_valid_entries; 172 __le32 persist_spare[30]; 173 struct crypt_persist_entry persist_entry[0]; 174 }; 175 176 #define DATA_MNT_POINT "/data" 177 178 /* Return values for cryptfs_crypto_complete */ 179 #define CRYPTO_COMPLETE_NOT_ENCRYPTED 1 180 #define CRYPTO_COMPLETE_ENCRYPTED 0 181 #define CRYPTO_COMPLETE_BAD_METADATA -1 182 #define CRYPTO_COMPLETE_PARTIAL -2 183 #define CRYPTO_COMPLETE_INCONSISTENT -3 184 #define CRYPTO_COMPLETE_CORRUPT -4 185 186 /* Return values for cryptfs_enable_inplace*() */ 187 #define ENABLE_INPLACE_OK 0 188 #define ENABLE_INPLACE_ERR_OTHER -1 189 #define ENABLE_INPLACE_ERR_DEV -2 /* crypto_blkdev issue */ 190 191 /* Return values for cryptfs_getfield */ 192 #define CRYPTO_GETFIELD_OK 0 193 #define CRYPTO_GETFIELD_ERROR_NO_FIELD -1 194 #define CRYPTO_GETFIELD_ERROR_OTHER -2 195 #define CRYPTO_GETFIELD_ERROR_BUF_TOO_SMALL -3 196 197 /* Return values for cryptfs_setfield */ 198 #define CRYPTO_SETFIELD_OK 0 199 #define CRYPTO_SETFIELD_ERROR_OTHER -1 200 #define CRYPTO_SETFIELD_ERROR_FIELD_TOO_LONG -2 201 #define CRYPTO_SETFIELD_ERROR_VALUE_TOO_LONG -3 202 203 /* Return values for persist_del_key */ 204 #define PERSIST_DEL_KEY_OK 0 205 #define PERSIST_DEL_KEY_ERROR_OTHER -1 206 #define PERSIST_DEL_KEY_ERROR_NO_FIELD -2 207 208 #ifdef __cplusplus 209 extern "C" { 210 #endif 211 212 int wait_and_unmount(const char *mountpoint, bool kill); 213 214 typedef int (*kdf_func)(const char *passwd, const unsigned char *salt, 215 unsigned char *ikey, void *params); 216 217 int cryptfs_crypto_complete(void); 218 int cryptfs_check_passwd(char *pw); 219 int cryptfs_verify_passwd(char *newpw); 220 int cryptfs_restart(void); 221 int cryptfs_enable(char *flag, int type, char *passwd, int allow_reboot); 222 int cryptfs_changepw(int type, const char *newpw); 223 int cryptfs_enable_default(char *flag, int allow_reboot); 224 int cryptfs_setup_ext_volume(const char* label, const char* real_blkdev, 225 const unsigned char* key, int keysize, char* out_crypto_blkdev); 226 int cryptfs_revert_ext_volume(const char* label); 227 int cryptfs_enable_file(); 228 int cryptfs_getfield(const char *fieldname, char *value, int len); 229 int cryptfs_setfield(const char *fieldname, const char *value); 230 int cryptfs_mount_default_encrypted(void); 231 int cryptfs_get_password_type(void); 232 const char* cryptfs_get_password(void); 233 void cryptfs_clear_password(void); 234 235 // Functions for file encryption to use to inherit our encryption logic 236 int cryptfs_create_default_ftr(struct crypt_mnt_ftr* ftr, int key_length); 237 int cryptfs_get_master_key(struct crypt_mnt_ftr* ftr, const char* password, 238 unsigned char* master_key); 239 int cryptfs_set_password(struct crypt_mnt_ftr* ftr, const char* password, 240 const unsigned char* master_key); 241 #ifdef __cplusplus 242 } 243 #endif 244
