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Remove some logging that could result in an information leak.

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This commit is contained in:
Moxie Marlinspike 2012-08-05 19:03:14 -07:00
parent e45bc61624
commit dda75006e4
1 changed files with 27 additions and 34 deletions
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61
src/org/thoughtcrime/securesms/protocol/WirePrefix.java
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@ -1,6 +1,6 @@
/**
/**
* Copyright (C) 2011 Whisper Systems
*
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
@ -10,49 +10,47 @@
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
package org.thoughtcrime.securesms.protocol;
import org.thoughtcrime.securesms.util.Base64;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
import org.thoughtcrime.securesms.util.Base64;
import android.util.Log;
/**
* Calculates prefixes that identify a message as
* being part of an encrypted session. The idea was to
* make calculating and identifying these prefixes somewhat
* expensive, so that filtering them en-mass would come at a cost.
*
*
* @author Moxie Marlinspike
*/
public abstract class WirePrefix {
private static final int HASH_ITERATIONS = 1000;
private static final int PREFIX_BYTES = 3;
public static final int PREFIX_SIZE = 4;
public abstract String calculatePrefix(String message);
public static boolean isKeyExchange(String message) {
return verifyPrefix("?TSK", message);
}
public static boolean isEncryptedMessage(String message) {
return verifyPrefix("?TSM", message);
}
public static String calculateKeyExchangePrefix(String message) {
return calculatePrefix(("?TSK" + message).getBytes(), PREFIX_BYTES);
}
public static String calculateEncryptedMesagePrefix(String message) {
return calculatePrefix(("?TSM" + message).getBytes(), PREFIX_BYTES);
}
@ -60,27 +58,22 @@ public abstract class WirePrefix {
private static boolean verifyPrefix(String prefixType, String message) {
if (message.length() <= PREFIX_SIZE)
return false;
String prefix = message.substring(0, PREFIX_SIZE);
message = message.substring(PREFIX_SIZE);
Log.w("Prefix", "Calculating on message: " + message + "**");
message = message.substring(PREFIX_SIZE);
String calculatedPrefix = calculatePrefix((prefixType + message).getBytes(), PREFIX_BYTES);
assert(calculatedPrefix.length() == PREFIX_SIZE);
Log.w("Prefix", "Received prefix: " + prefix);
Log.w("Prefix", "Calculated prefix: " + calculatedPrefix);
return prefix.equals(calculatedPrefix);
return prefix.equals(calculatedPrefix);
}
private static String calculatePrefix(byte[] message, int byteCount) {
try {
MessageDigest md = MessageDigest.getInstance("SHA1");
byte[] runningDigest = message;
for (int i=0;i<HASH_ITERATIONS;i++) {
runningDigest = md.digest(runningDigest);
}
@ -88,30 +81,30 @@ public abstract class WirePrefix {
return Base64.encodeBytes(runningDigest, 0, byteCount);
} catch (NoSuchAlgorithmException e) {
throw new AssertionError(e);
}
}
}
public static String calculateEncryptedMmsSubject() {
try {
byte[] postfix = new byte[6];
SecureRandom.getInstance("SHA1PRNG").nextBytes(postfix);
String postfixString = Base64.encodeBytes(postfix);
String prefix = calculatePrefix(postfixString.getBytes(), 6);
return prefix + postfixString;
} catch (NoSuchAlgorithmException e) {
throw new AssertionError(e);
}
}
public static boolean isEncryptedMmsSubject(String subject) {
if (subject.length() < 9)
return false;
String prefix = subject.substring(0, 8);
String postfix = subject.substring(8);
String calculatedPrefix = calculatePrefix(postfix.getBytes(), 6);
return calculatedPrefix.equals(prefix);
}