StringsTextExtractor.java

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/*
 * Autopsy Forensic Browser
 *
 * Copyright 2011-2019 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.textextractors;
 
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.nio.charset.Charset;
import java.util.ArrayList;
import java.util.List;
import java.util.Objects;
import org.openide.util.Lookup;
import org.sleuthkit.autopsy.coreutils.StringExtract;
import org.sleuthkit.autopsy.coreutils.StringExtract.StringExtractUnicodeTable.SCRIPT;
import org.sleuthkit.autopsy.textextractors.configs.StringsConfig;
import org.sleuthkit.datamodel.Content;
import org.sleuthkit.datamodel.TskCoreException;
import org.sleuthkit.datamodel.TskException;

final class StringsTextExtractor implements TextExtractor {
 
    private boolean extractUTF8;
    private boolean extractUTF16;
    private final Content content;
    private final static String DEFAULT_INDEXED_TEXT_CHARSET = "UTF-8";
 
    private final List<SCRIPT> extractScripts = new ArrayList<>();

    public StringsTextExtractor(Content content) {
        //LATIN_2 is the default script
        extractScripts.add(SCRIPT.LATIN_2);
        extractUTF8 = true;
        this.content = content;
    }

    public final void setScripts(List<SCRIPT> extractScripts) {
        if (extractScripts == null) {
            return;
        }
 
        this.extractScripts.clear();
        this.extractScripts.addAll(extractScripts);
    }

    @Override
    public InputStreamReader getReader() {
        InputStream stringStream = getInputStream(content);
        return new InputStreamReader(stringStream, Charset.forName(DEFAULT_INDEXED_TEXT_CHARSET));
    }
 
    InputStream getInputStream(Content content) {
        //check which extract stream to use
        if (extractScripts.size() == 1 && extractScripts.get(0).equals(SCRIPT.LATIN_1)) {
            return new EnglishOnlyStream(content);//optimal for english, english only
        } else {
            return new InternationalStream(content, extractScripts, extractUTF8, extractUTF16);
        }
    }

    @Override
    public void setExtractionSettings(Lookup context) {
        if (context != null) {
            StringsConfig configInstance = context.lookup(StringsConfig.class);
            if (configInstance == null) {
                return;
            }
            if (Objects.nonNull(configInstance.getExtractUTF8())) {
                extractUTF8 = configInstance.getExtractUTF8();
            }
            if (Objects.nonNull(configInstance.getExtractUTF16())) {
                extractUTF16 = configInstance.getExtractUTF16();
            }
            if (Objects.nonNull(configInstance.getLanguageScripts())) {
                setScripts(configInstance.getLanguageScripts());
            }
        }
    }

    @Override
    public boolean isSupported() {
        return extractUTF8 || extractUTF16;
    }

    private static class EnglishOnlyStream extends InputStream {
 
        private static final String NLS = Character.toString((char) 10); //new line
        private static final int READ_BUF_SIZE = 65536;
        private static final int MIN_PRINTABLE_CHARS = 4; //num. of chars needed to qualify as a char string
 
        //args
        private final Content content;
 
        //internal working data
        private long contentOffset = 0; //offset in fscontent read into curReadBuf
        private final byte[] curReadBuf = new byte[READ_BUF_SIZE];
        private int bytesInReadBuf = 0;
        private int readBufOffset = 0; //offset in read buf processed
        private StringBuilder curString = new StringBuilder();
        private int curStringLen = 0;
        private StringBuilder tempString = new StringBuilder();
        private int tempStringLen = 0;
        private boolean isEOF = false;
        private boolean stringAtTempBoundary = false; //if temp has part of string that didn't make it in previous read()
        private boolean stringAtBufBoundary = false; //if read buffer has string being processed, continue as string from prev read() in next read()
        private boolean inString = false; //if current temp has min chars required
        private final byte[] oneCharBuf = new byte[1];

        private EnglishOnlyStream(Content content) {
            this.content = content;
        }
 
        @Override
        public int read(byte[] b, int off, int len) throws IOException {
            if (b == null) {
                throw new NullPointerException();
            } else if (off < 0 || len < 0 || len > b.length - off) {
                throw new IndexOutOfBoundsException();
            } else if (len == 0) {
                return 0;
            }
            long fileSize = content.getSize();
            if (fileSize == 0) {
                return -1;
            }
            if (isEOF) {
                return -1;
            }
            if (stringAtTempBoundary) {
                //append entire temp string residual from previous read()
                //because qualified string was broken down into 2 parts
                appendResetTemp();
                stringAtTempBoundary = false;
                //there could be more to this string in fscontent/buffer
            }
            boolean singleConsecZero = false; //preserve the current sequence of chars if 1 consecutive zero char
            int newCurLen = curStringLen + tempStringLen;
            while (newCurLen < len) {
                //need to extract more strings
                if (readBufOffset > bytesInReadBuf - 1) {
                    //no more bytes to process into strings, read them
                    try {
                        bytesInReadBuf = 0;
                        bytesInReadBuf = content.read(curReadBuf, contentOffset, READ_BUF_SIZE);
                    } catch (TskException ex) {
                        if (curStringLen > 0 || tempStringLen >= MIN_PRINTABLE_CHARS) {
                            appendResetTemp();
                            //have some extracted string, return that, and fail next time
                            isEOF = true;
                            int copied = copyToReturn(b, off, len);
                            return copied;
                        } else {
                            return -1; //EOF
                        }
                    }
                    if (bytesInReadBuf < 1) {
                        if (curStringLen > 0 || tempStringLen >= MIN_PRINTABLE_CHARS) {
                            appendResetTemp();
                            //have some extracted string, return that, and fail next time
                            isEOF = true;
                            int copied = copyToReturn(b, off, len);
                            return copied;
                        } else {
                            return -1; //EOF
                        }
                    }
                    //increment content offset for next read
                    contentOffset += bytesInReadBuf;
                    //reset read buf position
                    readBufOffset = 0;
                }
                //get char from cur read buf
                char c = (char) curReadBuf[readBufOffset++];
                singleConsecZero = c == 0 && singleConsecZero == false; //preserve the current sequence if max consec. 1 zero char
                if (StringExtract.isPrintableAscii(c)) {
                    tempString.append(c);
                    ++tempStringLen;
                    if (tempStringLen >= MIN_PRINTABLE_CHARS) {
                        inString = true;
                    }
                    //boundary case when temp has still chars - handled after the loop
                } else if (!singleConsecZero) {
                    //break the string, clear temp
                    if (tempStringLen >= MIN_PRINTABLE_CHARS || stringAtBufBoundary) {
                        //append entire temp string with new line
                        tempString.append(NLS);
                        ++tempStringLen;
                        curString.append(tempString);
                        curStringLen += tempStringLen;
                        stringAtBufBoundary = false;
                    }
                    //reset temp
                    tempString = new StringBuilder();
                    tempStringLen = 0;
                }
                newCurLen = curStringLen + tempStringLen;
            }
            //check if still in string state, so that next chars in read buf bypass min chars check
            //and qualify as string even if less < min chars required
            if (inString) {
                inString = false; //reset
                stringAtBufBoundary = true; //will bypass the check
            }
            //check if temp still has chars to qualify as a string
            //we might need to break up temp into 2 parts for next read() call
            //consume as many as possible to fill entire user buffer
            if (tempStringLen >= MIN_PRINTABLE_CHARS) {
                if (newCurLen > len) {
                    int appendChars = len - curStringLen;
                    //save part for next user read(), need to break up temp string
                    //do not append new line
                    String toAppend = tempString.substring(0, appendChars);
                    String newTemp = tempString.substring(appendChars);
                    curString.append(toAppend);
                    curStringLen += appendChars;
                    tempString = new StringBuilder(newTemp);
                    tempStringLen = newTemp.length();
                    stringAtTempBoundary = true;
                } else {
                    //append entire temp
                    curString.append(tempString);
                    curStringLen += tempStringLen;
                    //reset temp
                    tempString = new StringBuilder();
                    tempStringLen = 0;
                }
            } else {
                //if temp has a few chars, not qualified as string for now,
                //will be processed during next read() call
            }
            //copy current strings to user
            final int copied = copyToReturn(b, off, len);
            //there may be still chars in read buffer or  tempString, for next read()
            return copied;
        }
 
        //append temp buffer to cur string buffer and reset temp, if enough chars
        //does not append new line
        private void appendResetTemp() {
            if (tempStringLen >= MIN_PRINTABLE_CHARS) {
                curString.append(tempString);
                curStringLen += tempStringLen;
                tempString = new StringBuilder();
                tempStringLen = 0;
            }
        }
 
        //copy currently extracted string to user buffer
        //and reset for next read() call
        private int copyToReturn(byte[] b, int off, long len) {
            final String curStringS = curString.toString();
            //logger.log(Level.INFO, curStringS);
            byte[] stringBytes = curStringS.getBytes(Charset.forName(DEFAULT_INDEXED_TEXT_CHARSET));
            System.arraycopy(stringBytes, 0, b, off, Math.min(curStringLen, (int) len));
            //logger.log(Level.INFO, curStringS);
            //copied all string, reset
            curString = new StringBuilder();
            int ret = curStringLen;
            curStringLen = 0;
            return ret;
        }
 
        @Override
        public int read() throws IOException {
            final int read = read(oneCharBuf, 0, 1);
            if (read == 1) {
                return oneCharBuf[0];
            } else {
                return -1;
            }
        }
 
        @Override
        public int available() throws IOException {
            //we don't know how many bytes in curReadBuf may end up as strings
            return 0;
        }
 
        @Override
        public long skip(long n) throws IOException {
            //use default implementation that reads into skip buffer
            //but it could be more efficient
            return super.skip(n);
        }
    }

    private static class InternationalStream extends InputStream {
 
        private static final int FILE_BUF_SIZE = 1024 * 1024;
        private final Content content;
        private final byte[] oneCharBuf = new byte[1];
        private final StringExtract stringExtractor;
        private final boolean nothingToDo;
        private final byte[] fileReadBuff = new byte[FILE_BUF_SIZE];
        private long fileReadOffset = 0L;
        private byte[] convertBuff; //stores extracted string encoded as bytes, before returned to user
        private int convertBuffOffset = 0; //offset to start returning data to user on next read()
        private int bytesInConvertBuff = 0; //amount of data currently in the buffer
        private boolean fileEOF = false; //if file has more bytes to read
        private StringExtract.StringExtractResult lastExtractResult;

        private InternationalStream(Content content, List<SCRIPT> scripts, boolean extractUTF8, boolean extractUTF16) {
            this.content = content;
            this.stringExtractor = new StringExtract();
            this.stringExtractor.setEnabledScripts(scripts);
            this.nothingToDo = extractUTF8 == false && extractUTF16 == false;
            this.stringExtractor.setEnableUTF8(extractUTF8);
            this.stringExtractor.setEnableUTF16(extractUTF16);
        }
 
        @Override
        public int read() throws IOException {
            if (nothingToDo) {
                return -1;
            }
            final int read = read(oneCharBuf, 0, 1);
            if (read == 1) {
                return oneCharBuf[0];
            } else {
                return -1;
            }
        }
 
        @Override
        public int read(byte[] b, int off, int len) throws IOException {
            if (b == null) {
                throw new NullPointerException();
            } else if (off < 0 || len < 0 || len > b.length - off) {
                throw new IndexOutOfBoundsException();
            } else if (len == 0) {
                return 0;
            }
            if (nothingToDo) {
                return -1;
            }
            long fileSize = content.getSize();
            if (fileSize == 0) {
                return -1;
            }
            //read and convert until user buffer full
            //we have data if file can be read or when byteBuff has converted strings to return
            int bytesToUser = 0; //returned to user so far
            int offsetUser = off;
            while (bytesToUser < len && offsetUser < len) {
                //check if we have enough converted strings
                int convertBuffRemain = bytesInConvertBuff - convertBuffOffset;
                if ((convertBuff == null || convertBuffRemain == 0) && !fileEOF && fileReadOffset < fileSize) {
                    try {
                        //convert more strings, store in buffer
                        long toRead = 0;
 
                        //fill up entire fileReadBuff fresh
                        toRead = Math.min(FILE_BUF_SIZE, fileSize - fileReadOffset);
                        //}
                        int read = content.read(fileReadBuff, fileReadOffset, toRead);
                        if (read == -1 || read == 0) {
                            fileEOF = true;
                        } else {
                            fileReadOffset += read;
                            if (fileReadOffset >= fileSize) {
                                fileEOF = true;
                            }
                            //put converted string in convertBuff
                            convert(read);
                            convertBuffRemain = bytesInConvertBuff - convertBuffOffset;
                        }
                    } catch (TskCoreException ex) {
                        fileEOF = true;
                    }
                }
                //nothing more to read, and no more bytes in convertBuff
                if (convertBuff == null || convertBuffRemain == 0) {
                    if (fileEOF) {
                        return bytesToUser > 0 ? bytesToUser : -1;
                    } else {
                        //no strings extracted, try another read
                        continue;
                    }
                }
                //return part or all of convert buff to user
                final int toCopy = Math.min(convertBuffRemain, len - offsetUser);
                System.arraycopy(convertBuff, convertBuffOffset, b, offsetUser, toCopy);
 
                convertBuffOffset += toCopy;
                offsetUser += toCopy;
                bytesToUser += toCopy;
            }
            //if more string data in convertBuff, will be consumed on next read()
            return bytesToUser;
        }

        private void convert(int numBytes) {
            lastExtractResult = stringExtractor.extract(fileReadBuff, numBytes, 0);
            convertBuff = lastExtractResult.getText().getBytes(Charset.forName(DEFAULT_INDEXED_TEXT_CHARSET));
            //reset tracking vars
            if (lastExtractResult.getNumBytes() == 0) {
                bytesInConvertBuff = 0;
            } else {
                bytesInConvertBuff = convertBuff.length;
            }
            convertBuffOffset = 0;
        }
    }
}