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 35 UserState::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 41 UserState::~UserState() { 42 free(mUserDir); 43 free(mMasterKeyFile); 44 } 45 46 bool 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 61 void UserState::setState(State state) { 62 mState = state; 63 if (mState == STATE_NO_ERROR || mState == STATE_UNINITIALIZED) { 64 mRetry = MAX_RETRY; 65 } 66 } 67 68 void UserState::zeroizeMasterKeysInMemory() { 69 memset(mMasterKey, 0, sizeof(mMasterKey)); 70 memset(mSalt, 0, sizeof(mSalt)); 71 } 72 73 bool UserState::deleteMasterKey() { 74 setState(STATE_UNINITIALIZED); 75 zeroizeMasterKeysInMemory(); 76 return unlink(mMasterKeyFile) == 0 || errno == ENOENT; 77 } 78 79 ResponseCode 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 91 ResponseCode 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 } 102 103 ResponseCode 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 } 132 133 ResponseCode 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 } 139 140 ResponseCode 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 } 199 200 bool 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 } 223 224 void 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 } 239 240 bool UserState::generateSalt(Entropy* entropy) { 241 return entropy->generate_random_data(mSalt, sizeof(mSalt)); 242 } 243 244 bool 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 } 253 254 void UserState::setupMasterKeys() { 255 setState(STATE_NO_ERROR); 256 } 257
