69 lines
2.2 KiB
Java
69 lines
2.2 KiB
Java
/**
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* Copyright (C) 2014-2016 Open Whisper Systems
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*
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* Licensed according to the LICENSE file in this repository.
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*/
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package org.whispersystems.signalservice.internal.push;
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import org.whispersystems.libsignal.logging.Log;
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public class PushTransportDetails {
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private static final String TAG = PushTransportDetails.class.getSimpleName();
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private final int messageVersion;
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public PushTransportDetails(int messageVersion) {
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this.messageVersion = messageVersion;
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}
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public byte[] getStrippedPaddingMessageBody(byte[] messageWithPadding) {
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if (messageVersion < 2) throw new AssertionError("Unknown version: " + messageVersion);
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else if (messageVersion == 2) return messageWithPadding;
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int paddingStart = 0;
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for (int i=messageWithPadding.length-1;i>=0;i--) {
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if (messageWithPadding[i] == (byte)0x80) {
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paddingStart = i;
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break;
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} else if (messageWithPadding[i] != (byte)0x00) {
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Log.w(TAG, "Padding byte is malformed, returning unstripped padding.");
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return messageWithPadding;
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}
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}
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byte[] strippedMessage = new byte[paddingStart];
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System.arraycopy(messageWithPadding, 0, strippedMessage, 0, strippedMessage.length);
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return strippedMessage;
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}
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public byte[] getPaddedMessageBody(byte[] messageBody) {
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if (messageVersion < 2) throw new AssertionError("Unknown version: " + messageVersion);
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else if (messageVersion == 2) return messageBody;
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// NOTE: This is dumb. We have our own padding scheme, but so does the cipher.
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// The +1 -1 here is to make sure the Cipher has room to add one padding byte,
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// otherwise it'll add a full 16 extra bytes.
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byte[] paddedMessage = new byte[getPaddedMessageLength(messageBody.length + 1) - 1];
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System.arraycopy(messageBody, 0, paddedMessage, 0, messageBody.length);
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paddedMessage[messageBody.length] = (byte)0x80;
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return paddedMessage;
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}
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private int getPaddedMessageLength(int messageLength) {
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int messageLengthWithTerminator = messageLength + 1;
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int messagePartCount = messageLengthWithTerminator / 160;
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if (messageLengthWithTerminator % 160 != 0) {
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messagePartCount++;
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}
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return messagePartCount * 160;
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}
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}
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