1/*
2 * Copyright (C) 2016 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#define LOG_TAG "keystore"
18
19#include "user_state.h"
20
21#include <dirent.h>
22#include <fcntl.h>
23#include <stdio.h>
24#include <stdlib.h>
25#include <sys/stat.h>
26
27#include <openssl/evp.h>
28
29#include <cutils/log.h>
30
31#include "blob.h"
32#include "keystore_utils.h"
33
34
35UserState::UserState(uid_t userId) :
36        mUserId(userId), mState(STATE_UNINITIALIZED), mRetry(MAX_RETRY) {
37    asprintf(&mUserDir, "user_%u", mUserId);
38    asprintf(&mMasterKeyFile, "%s/.masterkey", mUserDir);
39}
40
41UserState::~UserState() {
42    free(mUserDir);
43    free(mMasterKeyFile);
44}
45
46bool UserState::initialize() {
47    if ((mkdir(mUserDir, S_IRUSR | S_IWUSR | S_IXUSR) < 0) && (errno != EEXIST)) {
48        ALOGE("Could not create directory '%s'", mUserDir);
49        return false;
50    }
51
52    if (access(mMasterKeyFile, R_OK) == 0) {
53        setState(STATE_LOCKED);
54    } else {
55        setState(STATE_UNINITIALIZED);
56    }
57
58    return true;
59}
60
61void UserState::setState(State state) {
62    mState = state;
63    if (mState == STATE_NO_ERROR || mState == STATE_UNINITIALIZED) {
64        mRetry = MAX_RETRY;
65    }
66}
67
68void UserState::zeroizeMasterKeysInMemory() {
69    memset(mMasterKey, 0, sizeof(mMasterKey));
70    memset(mSalt, 0, sizeof(mSalt));
71}
72
73bool UserState::deleteMasterKey() {
74    setState(STATE_UNINITIALIZED);
75    zeroizeMasterKeysInMemory();
76    return unlink(mMasterKeyFile) == 0 || errno == ENOENT;
77}
78
79ResponseCode UserState::initialize(const android::String8& pw, Entropy* entropy) {
80    if (!generateMasterKey(entropy)) {
81        return ResponseCode::SYSTEM_ERROR;
82    }
83    ResponseCode response = writeMasterKey(pw, entropy);
84    if (response != ResponseCode::NO_ERROR) {
85        return response;
86    }
87    setupMasterKeys();
88    return ResponseCode::NO_ERROR;
89}
90
91ResponseCode UserState::copyMasterKey(UserState* src) {
92    if (mState != STATE_UNINITIALIZED) {
93        return ResponseCode::SYSTEM_ERROR;
94    }
95    if (src->getState() != STATE_NO_ERROR) {
96        return ResponseCode::SYSTEM_ERROR;
97    }
98    memcpy(mMasterKey, src->mMasterKey, MASTER_KEY_SIZE_BYTES);
99    setupMasterKeys();
100    return copyMasterKeyFile(src);
101}
102
103ResponseCode UserState::copyMasterKeyFile(UserState* src) {
104    /* Copy the master key file to the new user.  Unfortunately we don't have the src user's
105     * password so we cannot generate a new file with a new salt.
106     */
107    int in = TEMP_FAILURE_RETRY(open(src->getMasterKeyFileName(), O_RDONLY));
108    if (in < 0) {
109        return ResponseCode::SYSTEM_ERROR;
110    }
111    blobv3 rawBlob;
112    size_t length = readFully(in, (uint8_t*)&rawBlob, sizeof(rawBlob));
113    if (close(in) != 0) {
114        return ResponseCode::SYSTEM_ERROR;
115    }
116    int out =
117        TEMP_FAILURE_RETRY(open(mMasterKeyFile, O_WRONLY | O_TRUNC | O_CREAT, S_IRUSR | S_IWUSR));
118    if (out < 0) {
119        return ResponseCode::SYSTEM_ERROR;
120    }
121    size_t outLength = writeFully(out, (uint8_t*)&rawBlob, length);
122    if (close(out) != 0) {
123        return ResponseCode::SYSTEM_ERROR;
124    }
125    if (outLength != length) {
126        ALOGW("blob not fully written %zu != %zu", outLength, length);
127        unlink(mMasterKeyFile);
128        return ResponseCode::SYSTEM_ERROR;
129    }
130    return ResponseCode::NO_ERROR;
131}
132
133ResponseCode UserState::writeMasterKey(const android::String8& pw, Entropy* entropy) {
134    uint8_t passwordKey[MASTER_KEY_SIZE_BYTES];
135    generateKeyFromPassword(passwordKey, MASTER_KEY_SIZE_BYTES, pw, mSalt);
136    Blob masterKeyBlob(mMasterKey, sizeof(mMasterKey), mSalt, sizeof(mSalt), TYPE_MASTER_KEY);
137    return masterKeyBlob.writeBlob(mMasterKeyFile, passwordKey, STATE_NO_ERROR, entropy);
138}
139
140ResponseCode UserState::readMasterKey(const android::String8& pw, Entropy* entropy) {
141    int in = TEMP_FAILURE_RETRY(open(mMasterKeyFile, O_RDONLY));
142    if (in < 0) {
143        return ResponseCode::SYSTEM_ERROR;
144    }
145
146    // We read the raw blob to just to get the salt to generate the AES key, then we create the Blob
147    // to use with decryptBlob
148    blobv3 rawBlob;
149    size_t length = readFully(in, (uint8_t*)&rawBlob, sizeof(rawBlob));
150    if (close(in) != 0) {
151        return ResponseCode::SYSTEM_ERROR;
152    }
153    // find salt at EOF if present, otherwise we have an old file
154    uint8_t* salt;
155    if (length > SALT_SIZE && rawBlob.info == SALT_SIZE) {
156        salt = (uint8_t*)&rawBlob + length - SALT_SIZE;
157    } else {
158        salt = NULL;
159    }
160    uint8_t passwordKey[MASTER_KEY_SIZE_BYTES];
161    generateKeyFromPassword(passwordKey, MASTER_KEY_SIZE_BYTES, pw, salt);
162    Blob masterKeyBlob(rawBlob);
163    ResponseCode response = masterKeyBlob.readBlob(mMasterKeyFile, passwordKey, STATE_NO_ERROR);
164    if (response == ResponseCode::SYSTEM_ERROR) {
165        return response;
166    }
167    if (response == ResponseCode::NO_ERROR && masterKeyBlob.getLength() == MASTER_KEY_SIZE_BYTES) {
168        // If salt was missing, generate one and write a new master key file with the salt.
169        if (salt == NULL) {
170            if (!generateSalt(entropy)) {
171                return ResponseCode::SYSTEM_ERROR;
172            }
173            response = writeMasterKey(pw, entropy);
174        }
175        if (response == ResponseCode::NO_ERROR) {
176            memcpy(mMasterKey, masterKeyBlob.getValue(), MASTER_KEY_SIZE_BYTES);
177            setupMasterKeys();
178        }
179        return response;
180    }
181    if (mRetry <= 0) {
182        reset();
183        return ResponseCode::UNINITIALIZED;
184    }
185    --mRetry;
186    switch (mRetry) {
187    case 0:
188        return ResponseCode::WRONG_PASSWORD_0;
189    case 1:
190        return ResponseCode::WRONG_PASSWORD_1;
191    case 2:
192        return ResponseCode::WRONG_PASSWORD_2;
193    case 3:
194        return ResponseCode::WRONG_PASSWORD_3;
195    default:
196        return ResponseCode::WRONG_PASSWORD_3;
197    }
198}
199
200bool UserState::reset() {
201    DIR* dir = opendir(getUserDirName());
202    if (!dir) {
203        // If the directory doesn't exist then nothing to do.
204        if (errno == ENOENT) {
205            return true;
206        }
207        ALOGW("couldn't open user directory: %s", strerror(errno));
208        return false;
209    }
210
211    struct dirent* file;
212    while ((file = readdir(dir)) != NULL) {
213        // skip . and ..
214        if (!strcmp(".", file->d_name) || !strcmp("..", file->d_name)) {
215            continue;
216        }
217
218        unlinkat(dirfd(dir), file->d_name, 0);
219    }
220    closedir(dir);
221    return true;
222}
223
224void UserState::generateKeyFromPassword(uint8_t* key, ssize_t keySize, const android::String8& pw,
225                                        uint8_t* salt) {
226    size_t saltSize;
227    if (salt != NULL) {
228        saltSize = SALT_SIZE;
229    } else {
230        // Pre-gingerbread used this hardwired salt, readMasterKey will rewrite these when found
231        salt = (uint8_t*)"keystore";
232        // sizeof = 9, not strlen = 8
233        saltSize = sizeof("keystore");
234    }
235
236    PKCS5_PBKDF2_HMAC_SHA1(reinterpret_cast<const char*>(pw.string()), pw.length(), salt, saltSize,
237                           8192, keySize, key);
238}
239
240bool UserState::generateSalt(Entropy* entropy) {
241    return entropy->generate_random_data(mSalt, sizeof(mSalt));
242}
243
244bool UserState::generateMasterKey(Entropy* entropy) {
245    if (!entropy->generate_random_data(mMasterKey, sizeof(mMasterKey))) {
246        return false;
247    }
248    if (!generateSalt(entropy)) {
249        return false;
250    }
251    return true;
252}
253
254void UserState::setupMasterKeys() {
255    setState(STATE_NO_ERROR);
256}
257