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 <cutils/properties.h>
30
31/* The current cryptfs version */
32#define CURRENT_MAJOR_VERSION 1
33#define CURRENT_MINOR_VERSION 2
34
35#define CRYPT_FOOTER_OFFSET 0x4000
36#define CRYPT_FOOTER_TO_PERSIST_OFFSET 0x1000
37#define CRYPT_PERSIST_DATA_SIZE 0x1000
38
39#define MAX_CRYPTO_TYPE_NAME_LEN 64
40
41#define MAX_KEY_LEN 48
42#define SALT_LEN 16
43
44/* definitions of flags in the structure below */
45#define CRYPT_MNT_KEY_UNENCRYPTED 0x1 /* The key for the partition is not encrypted. */
46#define CRYPT_ENCRYPTION_IN_PROGRESS 0x2 /* Set when starting encryption,
47                                          * clear when done before rebooting */
48
49#define CRYPT_MNT_MAGIC 0xD0B5B1C4
50#define PERSIST_DATA_MAGIC 0xE950CD44
51
52#define SCRYPT_PROP "ro.crypto.scrypt_params"
53#define SCRYPT_DEFAULTS { 15, 3, 1 }
54
55/* Key Derivation Function algorithms */
56#define KDF_PBKDF2 1
57#define KDF_SCRYPT 2
58
59#define __le32 unsigned int
60#define __le16 unsigned short int
61#define __le8  unsigned char
62
63struct crypt_mnt_ftr {
64  __le32 magic;		/* See above */
65  __le16 major_version;
66  __le16 minor_version;
67  __le32 ftr_size; 	/* in bytes, not including key following */
68  __le32 flags;		/* See above */
69  __le32 keysize;	/* in bytes */
70  __le32 spare1;	/* ignored */
71  __le64 fs_size;	/* Size of the encrypted fs, in 512 byte sectors */
72  __le32 failed_decrypt_count; /* count of # of failed attempts to decrypt and
73				  mount, set to 0 on successful mount */
74  unsigned char crypto_type_name[MAX_CRYPTO_TYPE_NAME_LEN]; /* The type of encryption
75							       needed to decrypt this
76							       partition, null terminated */
77  __le32 spare2;        /* ignored */
78  unsigned char master_key[MAX_KEY_LEN]; /* The encrypted key for decrypting the filesystem */
79  unsigned char salt[SALT_LEN];   /* The salt used for this encryption */
80  __le64 persist_data_offset[2];  /* Absolute offset to both copies of crypt_persist_data
81                                   * on device with that info, either the footer of the
82                                   * real_blkdevice or the metadata partition. */
83
84  __le32 persist_data_size;       /* The number of bytes allocated to each copy of the
85                                   * persistent data table*/
86
87  __le8  kdf_type; /* The key derivation function used. */
88
89  /* scrypt parameters. See www.tarsnap.com/scrypt/scrypt.pdf */
90  __le8  N_factor; /* (1 << N) */
91  __le8  r_factor; /* (1 << r) */
92  __le8  p_factor; /* (1 << p) */
93};
94
95/* Persistant data that should be available before decryption.
96 * Things like airplane mode, locale and timezone are kept
97 * here and can be retrieved by the CryptKeeper UI to properly
98 * configure the phone before asking for the password
99 * This is only valid if the major and minor version above
100 * is set to 1.1 or higher.
101 *
102 * This is a 4K structure.  There are 2 copies, and the code alternates
103 * writing one and then clearing the previous one.  The reading
104 * code reads the first valid copy it finds, based on the magic number.
105 * The absolute offset to the first of the two copies is kept in rev 1.1
106 * and higher crypt_mnt_ftr structures.
107 */
108struct crypt_persist_entry {
109  char key[PROPERTY_KEY_MAX];
110  char val[PROPERTY_VALUE_MAX];
111};
112
113/* Should be exactly 4K in size */
114struct crypt_persist_data {
115  __le32 persist_magic;
116  __le32 persist_valid_entries;
117  __le32 persist_spare[30];
118  struct crypt_persist_entry persist_entry[0];
119};
120
121struct volume_info {
122   unsigned int size;
123   unsigned int flags;
124   struct crypt_mnt_ftr crypt_ftr;
125   char mnt_point[256];
126   char blk_dev[256];
127   char crypto_blkdev[256];
128   char label[256];
129};
130#define VOL_NONREMOVABLE   0x1
131#define VOL_ENCRYPTABLE    0x2
132#define VOL_PRIMARY        0x4
133#define VOL_PROVIDES_ASEC  0x8
134
135#ifdef __cplusplus
136extern "C" {
137#endif
138
139  typedef void (*kdf_func)(char *passwd, unsigned char *salt, unsigned char *ikey, void *params);
140
141  int cryptfs_crypto_complete(void);
142  int cryptfs_check_passwd(char *pw);
143  int cryptfs_verify_passwd(char *newpw);
144  int cryptfs_restart(void);
145  int cryptfs_enable(char *flag, char *passwd);
146  int cryptfs_changepw(char *newpw);
147  int cryptfs_setup_volume(const char *label, int major, int minor,
148                           char *crypto_dev_path, unsigned int max_pathlen,
149                           int *new_major, int *new_minor);
150  int cryptfs_revert_volume(const char *label);
151  int cryptfs_getfield(char *fieldname, char *value, int len);
152  int cryptfs_setfield(char *fieldname, char *value);
153#ifdef __cplusplus
154}
155#endif
156
157