LibraryLock.java

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/*
 * Sleuth Kit Data Model
 *
 * Copyright 2024 Basis Technology Corp.
 * Contact: carrier <at> sleuthkit <dot> org
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.sleuthkit.datamodel;
 
import java.io.File;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.nio.channels.FileChannel;
import java.nio.channels.FileLock;
import java.util.Arrays;
import java.util.logging.Level;

public class LibraryLock implements AutoCloseable {
 
        private static final String LIB_FILE_LOCK_TEXT = "lib_lock";
 
        private static final String TMP_DIR_KEY = "java.io.tmpdir";
        private static final String USER_NAME_KEY = "user.name";
 
        private static final byte[] UTF8_BOM = {(byte) 0XEF, (byte) 0xBB, (byte) 0XBF};
 
        private static LibraryLock libLock = null;

        public static LibraryLock acquireLibLock() {
                if (libLock == null) {
                        libLock = getLibLock();
                }
                return libLock;
        }

        public static void removeLibLock() throws Exception {
                if (libLock != null) {
                        libLock.close();
                }
        }

        private static LibraryLock getLibLock() {
                File libTskJniFile = LibraryUtils.getTempFile(
                                System.getProperty(TMP_DIR_KEY, ""),
                                LibraryUtils.Lib.TSK_JNI.getLibName(),
                                System.getProperty(USER_NAME_KEY, ""),
                                LibraryUtils.getExtByPlatform());
 
                // if the lock file exists
                if (libTskJniFile.isFile() && !libTskJniFile.canWrite()) {
                        // get the random access file as read only
                        try (RandomAccessFile lockFileRaf = new RandomAccessFile(libTskJniFile, "r")) {
                                LockState lockState = isNewLock(lockFileRaf)
                                                ? LockState.HELD_BY_NEW
                                                : LockState.HELD_BY_OLD;
 
                                return new LibraryLock(lockState, libTskJniFile, lockFileRaf, null, null);
                        } catch (IOException ex) {
                                // if there is an error getting read only access, then it is the old application dll
                                java.util.logging.Logger.getLogger(LibraryLock.class.getCanonicalName()).log(Level.WARNING, "An error occurred while acquiring the TSK lib lock", ex);
                                return new LibraryLock(LockState.HELD_BY_OLD, libTskJniFile, null, null, null);
                        }
                } else {
                        // make directories leading up to that
                        libTskJniFile.getParentFile().mkdirs();
 
                        // get file access to the file
                        RandomAccessFile lockFileRaf = null;
                        FileChannel lockFileChannel = null;
                        FileLock lockFileLock = null;
                        try {
                                lockFileRaf = new RandomAccessFile(libTskJniFile, "rw");
                                lockFileChannel = lockFileRaf.getChannel();
                                lockFileLock = lockFileChannel == null
                                                ? null
                                                : lockFileChannel.tryLock(1024L, 1L, false);
 
                                if (lockFileLock != null) {
                                        lockFileRaf.setLength(0);
                                        lockFileRaf.write(UTF8_BOM);
                                        lockFileRaf.writeChars(LIB_FILE_LOCK_TEXT);
 
                                        return new LibraryLock(LockState.ACQUIRED, libTskJniFile, lockFileRaf, lockFileChannel, lockFileLock);
                                } else {
                                        LockState lockState = isNewLock(lockFileRaf)
                                                        ? LockState.HELD_BY_NEW
                                                        : LockState.HELD_BY_OLD;
 
                                        return new LibraryLock(lockState, libTskJniFile, lockFileRaf, lockFileChannel, null);
                                }
                        } catch (IOException ex) {
                                // if there is an error getting read only access, then it is the old application dll
                                java.util.logging.Logger.getLogger(LibraryLock.class.getCanonicalName()).log(Level.WARNING, "An error occurred while acquiring the TSK lib lock", ex);
                                return new LibraryLock(LockState.HELD_BY_OLD, libTskJniFile, lockFileRaf, lockFileChannel, lockFileLock);
                        }
                }
        }

        private static boolean isNewLock(RandomAccessFile libRaf) throws IOException {
                libRaf.seek(0);
                byte[] startFileArr = new byte[UTF8_BOM.length];
                int read = libRaf.read(startFileArr);
                return read == startFileArr.length && Arrays.equals(UTF8_BOM, startFileArr);
 
        }
 
        private File libTskJniFile;
        private RandomAccessFile lockFileRaf;
        private FileChannel lockFileChannel;
        private FileLock lockFileLock;
        private LockState lockState;

        private LibraryLock(
                        LockState lockState,
                        File lockFile,
                        RandomAccessFile lockFileRaf,
                        FileChannel lockFileChannel,
                        FileLock lockFileLock) {
 
                this.libTskJniFile = lockFile;
                this.lockFileRaf = lockFileRaf;
                this.lockFileChannel = lockFileChannel;
                this.lockFileLock = lockFileLock;
                this.lockState = lockState;
        }

        public LockState getLockState() {
                return lockState;
        }

        public File getLibTskJniFile() {
                return libTskJniFile;
        }
 
        @Override
        public void close() throws Exception {
                // close lock file resources in reverse acquisition order
                if (this.lockFileLock != null) {
                        this.lockFileLock.close();
                        this.lockFileLock = null;
                }
 
                if (this.lockFileChannel != null) {
                        this.lockFileChannel.close();
                        this.lockFileChannel = null;
                }
 
                if (this.lockFileRaf != null) {
                        this.lockFileRaf.close();
                        this.lockFileRaf = null;
                }
 
                if (this.libTskJniFile != null) {
                        this.libTskJniFile.delete();
                        this.libTskJniFile = null;
                }
        }

        public enum LockState {
                HELD_BY_OLD,
                HELD_BY_NEW,
                ACQUIRED
        }
}