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//
// ========================================================================
// Copyright (c) 1995 Mort Bay Consulting Pty Ltd and others.
//
// This program and the accompanying materials are made available under the
// terms of the Eclipse Public License v. 2.0 which is available at
// https://www.eclipse.org/legal/epl-2.0, or the Apache License, Version 2.0
// which is available at https://www.apache.org/licenses/LICENSE-2.0.
//
// SPDX-License-Identifier: EPL-2.0 OR Apache-2.0
// ========================================================================
//
package org.eclipse.jetty.ee8.nested;

import java.nio.ByteBuffer;
import java.nio.charset.StandardCharsets;
import java.util.EnumSet;
import org.eclipse.jetty.http.BadMessageException;
import org.eclipse.jetty.http.HttpParser.RequestHandler;
import org.eclipse.jetty.http.HttpTokens;
import org.eclipse.jetty.util.BufferUtil;
import org.eclipse.jetty.util.SearchPattern;
import org.eclipse.jetty.util.Utf8StringBuilder;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * A parser for MultiPart content type.
 *
 * @see https://tools.ietf.org/html/rfc2046#section-5.1
 * @see https://tools.ietf.org/html/rfc2045
 */
public class MultiPartParser {

    public static final Logger LOG = LoggerFactory.getLogger(MultiPartParser.class);

    // States
    public enum FieldState {

        FIELD, IN_NAME, AFTER_NAME, VALUE, IN_VALUE
    }

    // States
    public enum State {

        PREAMBLE,
        DELIMITER,
        DELIMITER_PADDING,
        DELIMITER_CLOSE,
        BODY_PART,
        FIRST_OCTETS,
        OCTETS,
        EPILOGUE,
        END
    }

    private static final EnumSet __delimiterStates = EnumSet.of(State.DELIMITER, State.DELIMITER_CLOSE, State.DELIMITER_PADDING);

    private static final int MAX_HEADER_LINE_LENGTH = 998;

    private final boolean debugEnabled = LOG.isDebugEnabled();

    private final Handler _handler;

    private final SearchPattern _delimiterSearch;

    private String _fieldName;

    private String _fieldValue;

    private State _state = State.PREAMBLE;

    private FieldState _fieldState = FieldState.FIELD;

    // No CRLF if no preamble
    private int _partialBoundary = 2;

    private boolean _cr;

    private ByteBuffer _patternBuffer;

    private final Utf8StringBuilder _string = new Utf8StringBuilder();

    private int _length;

    private int _totalHeaderLineLength = -1;

    public MultiPartParser(Handler handler, String boundary) {
        _handler = handler;
        String delimiter = "\r\n--" + boundary;
        _patternBuffer = ByteBuffer.wrap(delimiter.getBytes(StandardCharsets.US_ASCII));
        _delimiterSearch = SearchPattern.compile(_patternBuffer.array());
    }

    public void reset() {
        _state = State.PREAMBLE;
        _fieldState = FieldState.FIELD;
        // No CRLF if no preamble
        _partialBoundary = 2;
    }

    public Handler getHandler() {
        return _handler;
    }

    public State getState() {
        return _state;
    }

    public boolean isState(State state) {
        return _state == state;
    }

    private static boolean hasNextByte(ByteBuffer buffer) {
        return BufferUtil.hasContent(buffer);
    }

    private HttpTokens.Token next(ByteBuffer buffer) {
        byte ch = buffer.get();
        HttpTokens.Token t = HttpTokens.TOKENS[0xff & ch];
        switch(t.getType()) {
            case CNTL:
                throw new IllegalCharacterException(_state, t, buffer);
            case LF:
                _cr = false;
                break;
            case CR:
                if (_cr)
                    throw new BadMessageException("Bad EOL");
                _cr = true;
                return null;
            case ALPHA:
            case DIGIT:
            case TCHAR:
            case VCHAR:
            case HTAB:
            case SPACE:
            case OTEXT:
            case COLON:
                if (_cr)
                    throw new BadMessageException("Bad EOL");
                break;
            default:
                break;
        }
        return t;
    }

    private void setString(String s) {
        _string.reset();
        _string.append(s);
        _length = s.length();
    }

    /**
     * Mime Field strings are treated as UTF-8 as per https://tools.ietf.org/html/rfc7578#section-5.1
     */
    private String takeString() {
        String s = _string.takeCompleteString(null);
        // trim trailing whitespace.
        if (s.length() > _length)
            s = s.substring(0, _length);
        _length = -1;
        return s;
    }

    /**
     * Parse until next Event.
     *
     * @param buffer the buffer to parse
     * @param last whether this buffer contains last bit of content
     * @return True if an {@link RequestHandler} method was called and it returned true;
     */
    public boolean parse(ByteBuffer buffer, boolean last) {
        boolean handle = false;
        while (!handle && BufferUtil.hasContent(buffer)) {
            switch(_state) {
                case PREAMBLE:
                    parsePreamble(buffer);
                    continue;
                case DELIMITER:
                case DELIMITER_PADDING:
                case DELIMITER_CLOSE:
                    parseDelimiter(buffer);
                    continue;
                case BODY_PART:
                    handle = parseMimePartHeaders(buffer);
                    break;
                case FIRST_OCTETS:
                case OCTETS:
                    handle = parseOctetContent(buffer);
                    break;
                case EPILOGUE:
                    BufferUtil.clear(buffer);
                    break;
                case END:
                    handle = true;
                    break;
                default:
                    throw new IllegalStateException();
            }
        }
        if (last && BufferUtil.isEmpty(buffer)) {
            if (_state == State.EPILOGUE) {
                _state = State.END;
                if (LOG.isDebugEnabled())
                    LOG.debug("messageComplete {}", this);
                return _handler.messageComplete();
            } else {
                if (LOG.isDebugEnabled())
                    LOG.debug("earlyEOF {}", this);
                _handler.earlyEOF();
                return true;
            }
        }
        return handle;
    }

    private void parsePreamble(ByteBuffer buffer) {
        if (LOG.isDebugEnabled())
            LOG.debug("parsePreamble({})", BufferUtil.toDetailString(buffer));
        if (_partialBoundary > 0) {
            int partial = _delimiterSearch.startsWith(buffer.array(), buffer.arrayOffset() + buffer.position(), buffer.remaining(), _partialBoundary);
            if (partial > 0) {
                if (partial == _delimiterSearch.getLength()) {
                    buffer.position(buffer.position() + partial - _partialBoundary);
                    _partialBoundary = 0;
                    setState(State.DELIMITER);
                    return;
                }
                _partialBoundary = partial;
                BufferUtil.clear(buffer);
                return;
            }
            _partialBoundary = 0;
        }
        int delimiter = _delimiterSearch.match(buffer.array(), buffer.arrayOffset() + buffer.position(), buffer.remaining());
        if (delimiter >= 0) {
            buffer.position(delimiter - buffer.arrayOffset() + _delimiterSearch.getLength());
            setState(State.DELIMITER);
            return;
        }
        _partialBoundary = _delimiterSearch.endsWith(buffer.array(), buffer.arrayOffset() + buffer.position(), buffer.remaining());
        BufferUtil.clear(buffer);
    }

    private void parseDelimiter(ByteBuffer buffer) {
        if (LOG.isDebugEnabled())
            LOG.debug("parseDelimiter({})", BufferUtil.toDetailString(buffer));
        while (__delimiterStates.contains(_state) && hasNextByte(buffer)) {
            HttpTokens.Token t = next(buffer);
            if (t == null)
                return;
            if (t.getType() == HttpTokens.Type.LF) {
                setState(State.BODY_PART);
                if (LOG.isDebugEnabled())
                    LOG.debug("startPart {}", this);
                _handler.startPart();
                return;
            }
            switch(_state) {
                case DELIMITER:
                    if (t.getChar() == '-')
                        setState(State.DELIMITER_CLOSE);
                    else
                        setState(State.DELIMITER_PADDING);
                    continue;
                case DELIMITER_CLOSE:
                    if (t.getChar() == '-') {
                        setState(State.EPILOGUE);
                        return;
                    }
                    setState(State.DELIMITER_PADDING);
                    continue;
                case DELIMITER_PADDING:
                default:
            }
        }
    }

    /*
     * Parse the message headers and return true if the handler has signaled for a return
     */
    protected boolean parseMimePartHeaders(ByteBuffer buffer) {
        if (LOG.isDebugEnabled())
            LOG.debug("parseMimePartHeaders({})", BufferUtil.toDetailString(buffer));
        // Process headers
        while (_state == State.BODY_PART && hasNextByte(buffer)) {
            // process each character
            HttpTokens.Token t = next(buffer);
            if (t == null)
                break;
            if (t.getType() != HttpTokens.Type.LF)
                _totalHeaderLineLength++;
            if (_totalHeaderLineLength > MAX_HEADER_LINE_LENGTH)
                throw new IllegalStateException("Header Line Exceeded Max Length");
            switch(_fieldState) {
                case FIELD:
                    switch(t.getType()) {
                        case SPACE:
                        case HTAB:
                            {
                                // Folded field value!
                                if (_fieldName == null)
                                    throw new IllegalStateException("First field folded");
                                if (_fieldValue == null) {
                                    _string.reset();
                                    _length = 0;
                                } else {
                                    setString(_fieldValue);
                                    _string.append(' ');
                                    _length++;
                                    _fieldValue = null;
                                }
                                setState(FieldState.VALUE);
                                break;
                            }
                        case LF:
                            handleField();
                            setState(State.FIRST_OCTETS);
                            // CRLF is option for empty parts
                            _partialBoundary = 2;
                            if (LOG.isDebugEnabled())
                                LOG.debug("headerComplete {}", this);
                            if (_handler.headerComplete())
                                return true;
                            break;
                        case ALPHA:
                        case DIGIT:
                        case TCHAR:
                            // process previous header
                            handleField();
                            // New header
                            setState(FieldState.IN_NAME);
                            _string.reset();
                            _string.append(t.getChar());
                            _length = 1;
                            break;
                        default:
                            throw new IllegalCharacterException(_state, t, buffer);
                    }
                    break;
                case IN_NAME:
                    switch(t.getType()) {
                        case COLON:
                            _fieldName = takeString();
                            _length = -1;
                            setState(FieldState.VALUE);
                            break;
                        case SPACE:
                            // Ignore trailing whitespaces
                            setState(FieldState.AFTER_NAME);
                            break;
                        case LF:
                            {
                                if (LOG.isDebugEnabled())
                                    LOG.debug("Line Feed in Name {}", this);
                                handleField();
                                setState(FieldState.FIELD);
                                break;
                            }
                        case ALPHA:
                        case DIGIT:
                        case TCHAR:
                            _string.append(t.getChar());
                            _length = _string.length();
                            break;
                        default:
                            throw new IllegalCharacterException(_state, t, buffer);
                    }
                    break;
                case AFTER_NAME:
                    switch(t.getType()) {
                        case COLON:
                            _fieldName = takeString();
                            _length = -1;
                            setState(FieldState.VALUE);
                            break;
                        case LF:
                            _fieldName = takeString();
                            _string.reset();
                            _fieldValue = "";
                            _length = -1;
                            break;
                        case SPACE:
                            break;
                        default:
                            throw new IllegalCharacterException(_state, t, buffer);
                    }
                    break;
                case VALUE:
                    switch(t.getType()) {
                        case LF:
                            _string.reset();
                            _fieldValue = "";
                            _length = -1;
                            setState(FieldState.FIELD);
                            break;
                        case SPACE:
                        case HTAB:
                            break;
                        case ALPHA:
                        case DIGIT:
                        case TCHAR:
                        case VCHAR:
                        case COLON:
                        case OTEXT:
                            _string.append(t.getByte());
                            _length = _string.length();
                            setState(FieldState.IN_VALUE);
                            break;
                        default:
                            throw new IllegalCharacterException(_state, t, buffer);
                    }
                    break;
                case IN_VALUE:
                    switch(t.getType()) {
                        case SPACE:
                        case HTAB:
                            _string.append(' ');
                            break;
                        case LF:
                            if (_length > 0) {
                                _fieldValue = takeString();
                                _length = -1;
                                _totalHeaderLineLength = -1;
                            }
                            setState(FieldState.FIELD);
                            break;
                        case ALPHA:
                        case DIGIT:
                        case TCHAR:
                        case VCHAR:
                        case COLON:
                        case OTEXT:
                            _string.append(t.getByte());
                            _length = _string.length();
                            break;
                        default:
                            throw new IllegalCharacterException(_state, t, buffer);
                    }
                    break;
                default:
                    throw new IllegalStateException(_state.toString());
            }
        }
        return false;
    }

    private void handleField() {
        if (LOG.isDebugEnabled())
            LOG.debug("parsedField:  _fieldName={} _fieldValue={} {}", _fieldName, _fieldValue, this);
        if (_fieldName != null && _fieldValue != null)
            _handler.parsedField(_fieldName, _fieldValue);
        _fieldName = _fieldValue = null;
    }

    protected boolean parseOctetContent(ByteBuffer buffer) {
        if (LOG.isDebugEnabled())
            LOG.debug("parseOctetContent({})", BufferUtil.toDetailString(buffer));
        // Starts With
        if (_partialBoundary > 0) {
            int partial = _delimiterSearch.startsWith(buffer.array(), buffer.arrayOffset() + buffer.position(), buffer.remaining(), _partialBoundary);
            if (partial > 0) {
                if (partial == _delimiterSearch.getLength()) {
                    buffer.position(buffer.position() + _delimiterSearch.getLength() - _partialBoundary);
                    setState(State.DELIMITER);
                    _partialBoundary = 0;
                    if (LOG.isDebugEnabled())
                        LOG.debug("Content={}, Last={} {}", BufferUtil.toDetailString(BufferUtil.EMPTY_BUFFER), true, this);
                    return _handler.content(BufferUtil.EMPTY_BUFFER, true);
                }
                _partialBoundary = partial;
                BufferUtil.clear(buffer);
                return false;
            } else {
                // output up to _partialBoundary of the search pattern
                ByteBuffer content = _patternBuffer.slice();
                if (_state == State.FIRST_OCTETS) {
                    setState(State.OCTETS);
                    content.position(2);
                }
                content.limit(_partialBoundary);
                _partialBoundary = 0;
                if (LOG.isDebugEnabled())
                    LOG.debug("Content={}, Last={} {}", BufferUtil.toDetailString(content), false, this);
                if (_handler.content(content, false))
                    return true;
            }
        }
        // Contains
        int delimiter = _delimiterSearch.match(buffer.array(), buffer.arrayOffset() + buffer.position(), buffer.remaining());
        if (delimiter >= 0) {
            ByteBuffer content = buffer.slice();
            content.limit(delimiter - buffer.arrayOffset() - buffer.position());
            buffer.position(delimiter - buffer.arrayOffset() + _delimiterSearch.getLength());
            setState(State.DELIMITER);
            if (LOG.isDebugEnabled())
                LOG.debug("Content={}, Last={} {}", BufferUtil.toDetailString(content), true, this);
            return _handler.content(content, true);
        }
        // Ends With
        _partialBoundary = _delimiterSearch.endsWith(buffer.array(), buffer.arrayOffset() + buffer.position(), buffer.remaining());
        if (_partialBoundary > 0) {
            ByteBuffer content = buffer.slice();
            content.limit(content.limit() - _partialBoundary);
            if (LOG.isDebugEnabled())
                LOG.debug("Content={}, Last={} {}", BufferUtil.toDetailString(content), false, this);
            BufferUtil.clear(buffer);
            return _handler.content(content, false);
        }
        // There is normal content with no delimiter
        ByteBuffer content = buffer.slice();
        if (LOG.isDebugEnabled())
            LOG.debug("Content={}, Last={} {}", BufferUtil.toDetailString(content), false, this);
        BufferUtil.clear(buffer);
        return _handler.content(content, false);
    }

    private void setState(State state) {
        if (debugEnabled)
            LOG.debug("{} --> {}", _state, state);
        _state = state;
    }

    private void setState(FieldState state) {
        if (debugEnabled)
            LOG.debug("{}:{} --> {}", _state, _fieldState, state);
        _fieldState = state;
    }

    @Override
    public String toString() {
        return String.format("%s{s=%s}", getClass().getSimpleName(), _state);
    }

    /*
     * Event Handler interface These methods return true if the caller should process the events so far received (eg return from parseNext and call
     * HttpChannel.handle). If multiple callbacks are called in sequence (eg headerComplete then messageComplete) from the same point in the parsing then it is
     * sufficient for the caller to process the events only once.
     */
    public interface Handler {

        default void startPart() {
        }

        @SuppressWarnings("unused")
        default void parsedField(String name, String value) {
        }

        default boolean headerComplete() {
            return false;
        }

        @SuppressWarnings("unused")
        default boolean content(ByteBuffer item, boolean last) {
            return false;
        }

        default boolean messageComplete() {
            return false;
        }

        default void earlyEOF() {
        }
    }

    @SuppressWarnings("serial")
    private static class IllegalCharacterException extends BadMessageException {

        private IllegalCharacterException(State state, HttpTokens.Token token, ByteBuffer buffer) {
            super(400, String.format("Illegal character %s", token));
            if (LOG.isDebugEnabled())
                LOG.debug(String.format("Illegal character %s in state=%s for buffer %s", token, state, BufferUtil.toDetailString(buffer)));
        }
    }
}




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