FileTypeDetector.java

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/*
 * Autopsy Forensic Browser
 *
 * Copyright 2014-2015 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.autopsy.modules.filetypeid;

import java.util.ArrayList;
import java.util.Map;
import java.util.SortedSet;
import org.apache.tika.Tika;
import org.apache.tika.mime.MediaType;
import org.apache.tika.mime.MimeTypes;
import org.sleuthkit.datamodel.AbstractFile;
import org.sleuthkit.datamodel.BlackboardArtifact;
import org.sleuthkit.datamodel.BlackboardAttribute;
import org.sleuthkit.datamodel.TskCoreException;
import org.sleuthkit.datamodel.TskData;

public class FileTypeDetector {

    private static final Tika tika = new Tika();
    private static final int BUFFER_SIZE = 64 * 1024;
    private final byte buffer[] = new byte[BUFFER_SIZE];
    private final Map<String, FileType> userDefinedFileTypes;

    public FileTypeDetector() throws FileTypeDetectorInitException {
        try {
            userDefinedFileTypes = UserDefinedFileTypesManager.getInstance().getFileTypes();
        } catch (UserDefinedFileTypesManager.UserDefinedFileTypesException ex) {
            throw new FileTypeDetectorInitException("Error loading user-defined file types", ex); //NON-NLS
        }
    }

    public boolean isDetectable(String mimeType) {
        return isDetectableAsUserDefinedType(mimeType) || isDetectableByTika(mimeType);
    }

    private boolean isDetectableAsUserDefinedType(String mimeType) {
        return userDefinedFileTypes.containsKey(mimeType);
    }

    private boolean isDetectableByTika(String mimeType) {
        String[] split = mimeType.split("/");
        if (split.length == 2) {
            String type = split[0];
            String subtype = split[1];
            MediaType mediaType = new MediaType(type, subtype);
            SortedSet<MediaType> m = MimeTypes.getDefaultMimeTypes().getMediaTypeRegistry().getTypes();
            return m.contains(mediaType);
        }
        return false;
    }

    public String getFileType(AbstractFile file) throws TskCoreException {
        String fileType;
        ArrayList<BlackboardAttribute> attributes = file.getGenInfoAttributes(BlackboardAttribute.ATTRIBUTE_TYPE.TSK_FILE_TYPE_SIG);
        for (BlackboardAttribute attribute : attributes) {
            fileType = attribute.getValueString();
            if (null != fileType && !fileType.isEmpty()) {
                return fileType;
            }
        }
        return detectAndPostToBlackboard(file);
    }

    public String detectAndPostToBlackboard(AbstractFile file) throws TskCoreException {
        String mimeType = detect(file);
        if (null != mimeType) {
            BlackboardArtifact getInfoArt = file.getGenInfoArtifact();
            BlackboardAttribute batt = new BlackboardAttribute(BlackboardAttribute.ATTRIBUTE_TYPE.TSK_FILE_TYPE_SIG.getTypeID(), FileTypeIdModuleFactory.getModuleName(), mimeType);
            getInfoArt.addAttribute(batt);
        }
        return mimeType;
    }

    public String detect(AbstractFile file) throws TskCoreException {
        // consistently mark non-regular files (refer TskData.TSK_FS_META_TYPE_ENUM),
        // 0 sized files, unallocated, and unused blocks (refer TskData.TSK_DB_FILES_TYPE_ENUM)
        // as octet-stream.
        if (!file.isFile() || file.getSize() <= 0
                || (file.getType() == TskData.TSK_DB_FILES_TYPE_ENUM.UNALLOC_BLOCKS)
                || (file.getType() == TskData.TSK_DB_FILES_TYPE_ENUM.UNUSED_BLOCKS)) {
            return MimeTypes.OCTET_STREAM;
        }

        String fileType = detectUserDefinedType(file);
        if (null == fileType) {
            try {
                byte buf[];
                int len = file.read(buffer, 0, BUFFER_SIZE);
                if (len < BUFFER_SIZE) {
                    buf = new byte[len];
                    System.arraycopy(buffer, 0, buf, 0, len);
                } else {
                    buf = buffer;
                }

                String mimetype = tika.detect(buf, file.getName());

                return mimetype.replace("tika-", ""); //NON-NLS

            } catch (Exception ignored) {
            }
        }
        return fileType;
    }

    private String detectUserDefinedType(AbstractFile file) throws TskCoreException {
        for (FileType fileType : userDefinedFileTypes.values()) {
            if (fileType.matches(file)) {
                if (fileType.alertOnMatch()) {
                    BlackboardArtifact artifact;
                    artifact = file.newArtifact(BlackboardArtifact.ARTIFACT_TYPE.TSK_INTERESTING_FILE_HIT);
                    BlackboardAttribute setNameAttribute = new BlackboardAttribute(BlackboardAttribute.ATTRIBUTE_TYPE.TSK_SET_NAME.getTypeID(), FileTypeIdModuleFactory.getModuleName(), fileType.getFilesSetName());
                    artifact.addAttribute(setNameAttribute);

                    BlackboardAttribute ruleNameAttribute = new BlackboardAttribute(BlackboardAttribute.ATTRIBUTE_TYPE.TSK_CATEGORY.getTypeID(), FileTypeIdModuleFactory.getModuleName(), fileType.getMimeType());
                    artifact.addAttribute(ruleNameAttribute);
                }
                return fileType.getMimeType();
            }
        }
        return null;
    }

    public static class FileTypeDetectorInitException extends Exception {

        FileTypeDetectorInitException(String message) {
            super(message);
        }

        FileTypeDetectorInitException(String message, Throwable throwable) {
            super(message, throwable);
        }
    }

}