/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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.apache.catalina.core;

import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.io.UnsupportedEncodingException;
import java.util.Collection;
import java.util.Collections;
import java.util.Iterator;
import java.util.LinkedHashSet;
import java.util.Locale;
import java.util.Map;

import javax.servlet.http.Part;

import org.apache.tomcat.util.http.fileupload.FileItem;
import org.apache.tomcat.util.http.fileupload.ParameterParser;
import org.apache.tomcat.util.http.fileupload.disk.DiskFileItem;

/**
 * Adaptor to allow {@link FileItem} objects generated by the package renamed
 * commons-upload to be used by the Servlet 3.0 upload API that expects
 * {@link Part}s.
 */
public class ApplicationPart implements Part {

    private final FileItem fileItem;
    private final File location;

    public ApplicationPart(FileItem fileItem, File location) {
        this.fileItem = fileItem;
        this.location = location;
    }

    @Override
    public void delete() throws IOException {
        fileItem.delete();
    }

    @Override
    public String getContentType() {
        return fileItem.getContentType();
    }

    @Override
    public String getHeader(String name) {
        if (fileItem instanceof DiskFileItem) {
            return ((DiskFileItem) fileItem).getHeaders().getHeader(name);
        }
        return null;
    }

    @Override
    public Collection<String> getHeaderNames() {
        if (fileItem instanceof DiskFileItem) {
            LinkedHashSet<String> headerNames = new LinkedHashSet<>();
            Iterator<String> iter =
                ((DiskFileItem) fileItem).getHeaders().getHeaderNames();
            while (iter.hasNext()) {
                headerNames.add(iter.next());
            }
            return headerNames;
        }
        return Collections.emptyList();
    }

    @Override
    public Collection<String> getHeaders(String name) {
        if (fileItem instanceof DiskFileItem) {
            LinkedHashSet<String> headers = new LinkedHashSet<>();
            Iterator<String> iter =
                ((DiskFileItem) fileItem).getHeaders().getHeaders(name);
            while (iter.hasNext()) {
                headers.add(iter.next());
            }
            return headers;
        }
        return Collections.emptyList();
    }

    @Override
    public InputStream getInputStream() throws IOException {
        return fileItem.getInputStream();
    }

    @Override
    public String getName() {
        return fileItem.getFieldName();
    }

    @Override
    public long getSize() {
        return fileItem.getSize();
    }

    @Override
    public void write(String fileName) throws IOException {
        File file = new File(fileName);
        if (!file.isAbsolute()) {
            file = new File(location, fileName);
        }
        try {
            fileItem.write(file);
        } catch (Exception e) {
            throw new IOException(e);
        }
    }

    public String getString(String encoding) throws UnsupportedEncodingException {
        return fileItem.getString(encoding);
    }

    /*
     * Adapted from FileUploadBase.getFileName()
     */
    @Override
    public String getSubmittedFileName() {
        String fileName = null;
        String cd = getHeader("Content-Disposition");
        if (cd != null) {
            String cdl = cd.toLowerCase(Locale.ENGLISH);
            if (cdl.startsWith("form-data") || cdl.startsWith("attachment")) {
                ParameterParser paramParser = new ParameterParser();
                paramParser.setLowerCaseNames(true);
                // Parameter parser can handle null input
                Map<String,String> params =
                    paramParser.parse(cd, ';');
                if (params.containsKey("filename")) {
                    fileName = params.get("filename");
                    if (fileName != null) {
                        // This is a token or a quoted-string. If it is a token,
                        // there won't be any '\' characters. If it is a
                        // quoted-string it can be dequoted by removing the '\'
                        // characters.
                        fileName = fileName.trim().replaceAll("\\", "");
                    } else {
                        // Even if there is no value, the parameter is present,
                        // so we return an empty file name rather than no file
                        // name.
                        fileName = "";
                    }
                }
            }
        }
        return fileName;
    }
}

@@ -5039,16 +5039,18 @@
 eAll(%22%5C%5C
+%5C%5C
 %22, %22%22);%0A

Correct regex. The actual regex is "\\" and since '\' needs to be escaped the code needs to use "\\\\"