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/*
 * Copyright (c) 1997, 2018 Oracle and/or its affiliates. All rights reserved.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v. 2.0, which is available at
 * http://www.eclipse.org/legal/epl-2.0.
 *
 * This Source Code may also be made available under the following Secondary
 * Licenses when the conditions for such availability set forth in the
 * Eclipse Public License v. 2.0 are satisfied: GNU General Public License,
 * version 2 with the GNU Classpath Exception, which is available at
 * https://www.gnu.org/software/classpath/license.html.
 *
 * SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
 */

package com.sun.mail.util;

import java.io.*;

/**
 * This class implements a BASE64 Decoder. It is implemented as
 * a FilterInputStream, so one can just wrap this class around
 * any input stream and read bytes from this filter. The decoding
 * is done as the bytes are read out.
 * 
 * @author John Mani
 * @author Bill Shannon
 */

public class BASE64DecoderStream extends FilterInputStream {
    // buffer of decoded bytes for single byte reads
    private byte[] buffer = new byte[3];
    private int bufsize = 0;	// size of the cache
    private int index = 0;	// index into the cache

    // buffer for almost 8K of typical 76 chars + CRLF lines,
    // used by getByte method.  this buffer contains encoded bytes.
    private byte[] input_buffer = new byte[78*105];
    private int input_pos = 0;
    private int input_len = 0;;

    private boolean ignoreErrors = false;

    /** 
     * Create a BASE64 decoder that decodes the specified input stream.
     * The System property mail.mime.base64.ignoreerrors
     * controls whether errors in the encoded data cause an exception
     * or are ignored.  The default is false (errors cause exception).
     *
     * @param in	the input stream
     */
    public BASE64DecoderStream(InputStream in) {
	super(in);
	// default to false
	ignoreErrors = PropUtil.getBooleanSystemProperty(
	    "mail.mime.base64.ignoreerrors", false);
    }

    /** 
     * Create a BASE64 decoder that decodes the specified input stream.
     *
     * @param in	the input stream
     * @param ignoreErrors	ignore errors in encoded data?
     */
    public BASE64DecoderStream(InputStream in, boolean ignoreErrors) {
	super(in);
	this.ignoreErrors = ignoreErrors;
    }

    /**
     * Read the next decoded byte from this input stream. The byte
     * is returned as an int in the range 0 
     * to 255. If no byte is available because the end of 
     * the stream has been reached, the value -1 is returned.
     * This method blocks until input data is available, the end of the 
     * stream is detected, or an exception is thrown.
     *
     * @return     next byte of data, or -1 if the end of the
     *             stream is reached.
     * @exception  IOException  if an I/O error occurs.
     * @see        java.io.FilterInputStream#in
     */
    @Override
    public int read() throws IOException {
	if (index >= bufsize) {
	    bufsize = decode(buffer, 0, buffer.length);
	    if (bufsize <= 0) // buffer is empty
		return -1;
	    index = 0; // reset index into buffer
	}
	return buffer[index++] & 0xff; // Zero off the MSB
    }

    /**
     * Reads up to len decoded bytes of data from this input stream
     * into an array of bytes. This method blocks until some input is
     * available.
     * 

* * @param buf the buffer into which the data is read. * @param off the start offset of the data. * @param len the maximum number of bytes read. * @return the total number of bytes read into the buffer, or * -1 if there is no more data because the end of * the stream has been reached. * @exception IOException if an I/O error occurs. */ @Override public int read(byte[] buf, int off, int len) throws IOException { // empty out single byte read buffer int off0 = off; while (index < bufsize && len > 0) { buf[off++] = buffer[index++]; len--; } if (index >= bufsize) bufsize = index = 0; int bsize = (len / 3) * 3; // round down to multiple of 3 bytes if (bsize > 0) { int size = decode(buf, off, bsize); off += size; len -= size; if (size != bsize) { // hit EOF? if (off == off0) // haven't returned any data return -1; else // returned some data before hitting EOF return off - off0; } } // finish up with a partial read if necessary for (; len > 0; len--) { int c = read(); if (c == -1) // EOF break; buf[off++] = (byte)c; } if (off == off0) // haven't returned any data return -1; else // returned some data before hitting EOF return off - off0; } /** * Skips over and discards n bytes of data from this stream. */ @Override public long skip(long n) throws IOException { long skipped = 0; while (n-- > 0 && read() >= 0) skipped++; return skipped; } /** * Tests if this input stream supports marks. Currently this class * does not support marks */ @Override public boolean markSupported() { return false; // Maybe later .. } /** * Returns the number of bytes that can be read from this input * stream without blocking. However, this figure is only * a close approximation in case the original encoded stream * contains embedded CRLFs; since the CRLFs are discarded, not decoded */ @Override public int available() throws IOException { // This is only an estimate, since in.available() // might include CRLFs too .. return ((in.available() * 3)/4 + (bufsize-index)); } /** * This character array provides the character to value map * based on RFC1521. */ private final static char pem_array[] = { 'A','B','C','D','E','F','G','H', // 0 'I','J','K','L','M','N','O','P', // 1 'Q','R','S','T','U','V','W','X', // 2 'Y','Z','a','b','c','d','e','f', // 3 'g','h','i','j','k','l','m','n', // 4 'o','p','q','r','s','t','u','v', // 5 'w','x','y','z','0','1','2','3', // 6 '4','5','6','7','8','9','+','/' // 7 }; private final static byte pem_convert_array[] = new byte[256]; static { for (int i = 0; i < 255; i++) pem_convert_array[i] = -1; for (int i = 0; i < pem_array.length; i++) pem_convert_array[pem_array[i]] = (byte)i; } /** * The decoder algorithm. Most of the complexity here is dealing * with error cases. Returns the number of bytes decoded, which * may be zero. Decoding is done by filling an int with 4 6-bit * values by shifting them in from the bottom and then extracting * 3 8-bit bytes from the int by shifting them out from the bottom. * * @param outbuf the buffer into which to put the decoded bytes * @param pos position in the buffer to start filling * @param len the number of bytes to fill * @return the number of bytes filled, always a multiple * of three, and may be zero * @exception IOException if the data is incorrectly formatted */ private int decode(byte[] outbuf, int pos, int len) throws IOException { int pos0 = pos; while (len >= 3) { /* * We need 4 valid base64 characters before we start decoding. * We skip anything that's not a valid base64 character (usually * just CRLF). */ int got = 0; int val = 0; while (got < 4) { int i = getByte(); if (i == -1 || i == -2) { boolean atEOF; if (i == -1) { if (got == 0) return pos - pos0; if (!ignoreErrors) throw new DecodingException( "BASE64Decoder: Error in encoded stream: " + "needed 4 valid base64 characters " + "but only got " + got + " before EOF" + recentChars()); atEOF = true; // don't read any more } else { // i == -2 // found a padding character, we're at EOF // XXX - should do something to make EOF "sticky" if (got < 2 && !ignoreErrors) throw new DecodingException( "BASE64Decoder: Error in encoded stream: " + "needed at least 2 valid base64 characters," + " but only got " + got + " before padding character (=)" + recentChars()); // didn't get any characters before padding character? if (got == 0) return pos - pos0; atEOF = false; // need to keep reading } // pad partial result with zeroes // how many bytes will we produce on output? // (got always < 4, so size always < 3) int size = got - 1; if (size == 0) size = 1; // handle the one padding character we've seen got++; val <<= 6; while (got < 4) { if (!atEOF) { // consume the rest of the padding characters, // filling with zeroes i = getByte(); if (i == -1) { if (!ignoreErrors) throw new DecodingException( "BASE64Decoder: Error in encoded " + "stream: hit EOF while looking for " + "padding characters (=)" + recentChars()); } else if (i != -2) { if (!ignoreErrors) throw new DecodingException( "BASE64Decoder: Error in encoded " + "stream: found valid base64 " + "character after a padding character " + "(=)" + recentChars()); } } val <<= 6; got++; } // now pull out however many valid bytes we got val >>= 8; // always skip first one if (size == 2) outbuf[pos + 1] = (byte)(val & 0xff); val >>= 8; outbuf[pos] = (byte)(val & 0xff); // len -= size; // not needed, return below pos += size; return pos - pos0; } else { // got a valid byte val <<= 6; got++; val |= i; } } // read 4 valid characters, now extract 3 bytes outbuf[pos + 2] = (byte)(val & 0xff); val >>= 8; outbuf[pos + 1] = (byte)(val & 0xff); val >>= 8; outbuf[pos] = (byte)(val & 0xff); len -= 3; pos += 3; } return pos - pos0; } /** * Read the next valid byte from the input stream. * Buffer lots of data from underlying stream in input_buffer, * for efficiency. * * @return the next byte, -1 on EOF, or -2 if next byte is '=' * (padding at end of encoded data) */ private int getByte() throws IOException { int c; do { if (input_pos >= input_len) { try { input_len = in.read(input_buffer); } catch (EOFException ex) { return -1; } if (input_len <= 0) return -1; input_pos = 0; } // get the next byte in the buffer c = input_buffer[input_pos++] & 0xff; // is it a padding byte? if (c == '=') return -2; // no, convert it c = pem_convert_array[c]; // loop until we get a legitimate byte } while (c == -1); return c; } /** * Return the most recent characters, for use in an error message. */ private String recentChars() { // reach into the input buffer and extract up to 10 // recent characters, to help in debugging. String errstr = ""; int nc = input_pos > 10 ? 10 : input_pos; if (nc > 0) { errstr += ", the " + nc + " most recent characters were: \""; for (int k = input_pos - nc; k < input_pos; k++) { char c = (char)(input_buffer[k] & 0xff); switch (c) { case '\r': errstr += "\\r"; break; case '\n': errstr += "\\n"; break; case '\t': errstr += "\\t"; break; default: if (c >= ' ' && c < 0177) errstr += c; else errstr += ("\\" + (int)c); } } errstr += "\""; } return errstr; } /** * Base64 decode a byte array. No line breaks are allowed. * This method is suitable for short strings, such as those * in the IMAP AUTHENTICATE protocol, but not to decode the * entire content of a MIME part. * * NOTE: inbuf may only contain valid base64 characters. * Whitespace is not ignored. * * @param inbuf the byte array * @return the decoded byte array */ public static byte[] decode(byte[] inbuf) { int size = (inbuf.length / 4) * 3; if (size == 0) return inbuf; if (inbuf[inbuf.length - 1] == '=') { size--; if (inbuf[inbuf.length - 2] == '=') size--; } byte[] outbuf = new byte[size]; int inpos = 0, outpos = 0; size = inbuf.length; while (size > 0) { int val; int osize = 3; val = pem_convert_array[inbuf[inpos++] & 0xff]; val <<= 6; val |= pem_convert_array[inbuf[inpos++] & 0xff]; val <<= 6; if (inbuf[inpos] != '=') // End of this BASE64 encoding val |= pem_convert_array[inbuf[inpos++] & 0xff]; else osize--; val <<= 6; if (inbuf[inpos] != '=') // End of this BASE64 encoding val |= pem_convert_array[inbuf[inpos++] & 0xff]; else osize--; if (osize > 2) outbuf[outpos + 2] = (byte)(val & 0xff); val >>= 8; if (osize > 1) outbuf[outpos + 1] = (byte)(val & 0xff); val >>= 8; outbuf[outpos] = (byte)(val & 0xff); outpos += osize; size -= 4; } return outbuf; } /*** begin TEST program *** public static void main(String argv[]) throws Exception { FileInputStream infile = new FileInputStream(argv[0]); BASE64DecoderStream decoder = new BASE64DecoderStream(infile); int c; while ((c = decoder.read()) != -1) System.out.print((char)c); System.out.flush(); } *** end TEST program ***/ }





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