package org.bouncycastle.openpgp;
import java.io.EOFException;
import java.io.IOException;
import java.io.InputStream;
import java.security.DigestInputStream;
import java.security.MessageDigest;
import org.bouncycastle.bcpg.InputStreamPacket;
import org.bouncycastle.bcpg.SymmetricEncIntegrityPacket;
import org.bouncycastle.bcpg.SymmetricKeyAlgorithmTags;
import org.bouncycastle.util.Arrays;
public abstract class PGPEncryptedData
implements SymmetricKeyAlgorithmTags
{
protected class TruncatedStream extends InputStream
{
int[] lookAhead = new int[22];
int bufPtr;
InputStream in;
TruncatedStream(
InputStream in)
throws IOException
{
for (int i = 0; i != lookAhead.length; i++)
{
if ((lookAhead[i] = in.read()) < 0)
{
throw new EOFException();
}
}
bufPtr = 0;
this.in = in;
}
public int read()
throws IOException
{
int ch = in.read();
if (ch >= 0)
{
int c = lookAhead[bufPtr];
lookAhead[bufPtr] = ch;
bufPtr = (bufPtr + 1) % lookAhead.length;
return c;
}
return -1;
}
int[] getLookAhead()
{
int[] tmp = new int[lookAhead.length];
int count = 0;
for (int i = bufPtr; i != lookAhead.length; i++)
{
tmp[count++] = lookAhead[i];
}
for (int i = 0; i != bufPtr; i++)
{
tmp[count++] = lookAhead[i];
}
return tmp;
}
}
InputStreamPacket encData;
InputStream encStream;
TruncatedStream truncStream;
PGPEncryptedData(
InputStreamPacket encData)
{
this.encData = encData;
}
/**
* Return the raw input stream for the data stream.
*
* @return InputStream
*/
public InputStream getInputStream()
{
return encData.getInputStream();
}
/**
* Return true if the message is integrity protected.
* @return true if there is a modification detection code package associated with this stream
*/
public boolean isIntegrityProtected()
{
return (encData instanceof SymmetricEncIntegrityPacket);
}
/**
* Note: This can only be called after the message has been read.
*
* @return true if the message verifies, false otherwise.
* @throws PGPException if the message is not integrity protected.
*/
public boolean verify()
throws PGPException, IOException
{
if (!this.isIntegrityProtected())
{
throw new PGPException("data not integrity protected.");
}
DigestInputStream dIn = (DigestInputStream)encStream;
//
// make sure we are at the end.
//
while (encStream.read() >= 0)
{
// do nothing
}
MessageDigest hash = dIn.getMessageDigest();
//
// process the MDC packet
//
int[] lookAhead = truncStream.getLookAhead();
hash.update((byte)lookAhead[0]);
hash.update((byte)lookAhead[1]);
byte[] digest = hash.digest();
byte[] streamDigest = new byte[digest.length];
for (int i = 0; i != streamDigest.length; i++)
{
streamDigest[i] = (byte)lookAhead[i + 2];
}
return Arrays.constantTimeAreEqual(digest, streamDigest);
}
}