| /* ==================================================================== |
| 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.poi.hssf.record.crypto; |
| |
| import java.io.InputStream; |
| import java.io.PushbackInputStream; |
| |
| import org.apache.poi.hssf.record.BOFRecord; |
| import org.apache.poi.hssf.record.BiffHeaderInput; |
| import org.apache.poi.hssf.record.FilePassRecord; |
| import org.apache.poi.hssf.record.InterfaceHdrRecord; |
| import org.apache.poi.poifs.crypt.ChunkedCipherInputStream; |
| import org.apache.poi.poifs.crypt.Decryptor; |
| import org.apache.poi.poifs.crypt.EncryptionInfo; |
| import org.apache.poi.util.IOUtils; |
| import org.apache.poi.util.LittleEndian; |
| import org.apache.poi.util.LittleEndianConsts; |
| import org.apache.poi.util.LittleEndianInput; |
| import org.apache.poi.util.RecordFormatException; |
| import org.apache.poi.util.SuppressForbidden; |
| |
| public final class Biff8DecryptingStream implements BiffHeaderInput, LittleEndianInput { |
| |
| public static final int RC4_REKEYING_INTERVAL = 1024; |
| //arbitrarily selected; may need to increase |
| private static final int MAX_RECORD_LENGTH = 100_000; |
| |
| private ChunkedCipherInputStream ccis; |
| private final byte[] buffer = new byte[LittleEndianConsts.LONG_SIZE]; |
| private boolean shouldSkipEncryptionOnCurrentRecord; |
| |
| public Biff8DecryptingStream(InputStream in, int initialOffset, EncryptionInfo info) throws RecordFormatException { |
| try { |
| byte[] initialBuf = IOUtils.safelyAllocate(initialOffset, MAX_RECORD_LENGTH); |
| InputStream stream; |
| if (initialOffset == 0) { |
| stream = in; |
| } else { |
| stream = new PushbackInputStream(in, initialOffset); |
| ((PushbackInputStream)stream).unread(initialBuf); |
| } |
| |
| Decryptor dec = info.getDecryptor(); |
| dec.setChunkSize(RC4_REKEYING_INTERVAL); |
| ccis = (ChunkedCipherInputStream)dec.getDataStream(stream, Integer.MAX_VALUE, 0); |
| |
| if (initialOffset > 0) { |
| ccis.readFully(initialBuf); |
| } |
| } catch (Exception e) { |
| throw new RecordFormatException(e); |
| } |
| } |
| |
| @Override |
| @SuppressForbidden("just delegating") |
| public int available() { |
| return ccis.available(); |
| } |
| |
| /** |
| * Reads an unsigned short value without decrypting |
| */ |
| @Override |
| public int readRecordSID() { |
| readPlain(buffer, 0, LittleEndianConsts.SHORT_SIZE); |
| int sid = LittleEndian.getUShort(buffer, 0); |
| shouldSkipEncryptionOnCurrentRecord = isNeverEncryptedRecord(sid); |
| return sid; |
| } |
| |
| /** |
| * Reads an unsigned short value without decrypting |
| */ |
| @Override |
| public int readDataSize() { |
| readPlain(buffer, 0, LittleEndianConsts.SHORT_SIZE); |
| int dataSize = LittleEndian.getUShort(buffer, 0); |
| ccis.setNextRecordSize(dataSize); |
| return dataSize; |
| } |
| |
| @Override |
| public double readDouble() { |
| long valueLongBits = readLong(); |
| double result = Double.longBitsToDouble(valueLongBits); |
| if (Double.isNaN(result)) { |
| // (Because Excel typically doesn't write NaN |
| throw new RuntimeException("Did not expect to read NaN"); |
| } |
| return result; |
| } |
| |
| @Override |
| public void readFully(byte[] buf) { |
| readFully(buf, 0, buf.length); |
| } |
| |
| @Override |
| public void readFully(byte[] buf, int off, int len) { |
| if (shouldSkipEncryptionOnCurrentRecord) { |
| readPlain(buf, off, buf.length); |
| } else { |
| ccis.readFully(buf, off, len); |
| } |
| } |
| |
| @Override |
| public int readUByte() { |
| return readByte() & 0xFF; |
| } |
| |
| @Override |
| public byte readByte() { |
| if (shouldSkipEncryptionOnCurrentRecord) { |
| readPlain(buffer, 0, LittleEndianConsts.BYTE_SIZE); |
| return buffer[0]; |
| } else { |
| return ccis.readByte(); |
| } |
| } |
| |
| @Override |
| public int readUShort() { |
| return readShort() & 0xFFFF; |
| } |
| |
| @Override |
| public short readShort() { |
| if (shouldSkipEncryptionOnCurrentRecord) { |
| readPlain(buffer, 0, LittleEndianConsts.SHORT_SIZE); |
| return LittleEndian.getShort(buffer); |
| } else { |
| return ccis.readShort(); |
| } |
| } |
| |
| @Override |
| public int readInt() { |
| if (shouldSkipEncryptionOnCurrentRecord) { |
| readPlain(buffer, 0, LittleEndianConsts.INT_SIZE); |
| return LittleEndian.getInt(buffer); |
| } else { |
| return ccis.readInt(); |
| } |
| } |
| |
| @Override |
| public long readLong() { |
| if (shouldSkipEncryptionOnCurrentRecord) { |
| readPlain(buffer, 0, LittleEndianConsts.LONG_SIZE); |
| return LittleEndian.getLong(buffer); |
| } else { |
| return ccis.readLong(); |
| } |
| } |
| |
| /** |
| * @return the absolute position in the stream |
| */ |
| public long getPosition() { |
| return ccis.getPos(); |
| } |
| |
| /** |
| * TODO: Additionally, the lbPlyPos (position_of_BOF) field of the BoundSheet8 record MUST NOT be encrypted. |
| * |
| * @return <code>true</code> if record type specified by <tt>sid</tt> is never encrypted |
| */ |
| public static boolean isNeverEncryptedRecord(int sid) { |
| switch (sid) { |
| case BOFRecord.sid: |
| // sheet BOFs for sure |
| // TODO - find out about chart BOFs |
| |
| case InterfaceHdrRecord.sid: |
| // don't know why this record doesn't seem to get encrypted |
| |
| case FilePassRecord.sid: |
| // this only really counts when writing because FILEPASS is read early |
| |
| // UsrExcl(0x0194) |
| // FileLock |
| // RRDInfo(0x0196) |
| // RRDHead(0x0138) |
| |
| return true; |
| |
| default: |
| return false; |
| } |
| } |
| |
| @Override |
| public void readPlain(byte[] b, int off, int len) { |
| ccis.readPlain(b, off, len); |
| } |
| |
| } |