Author: nextgens
Date: 2007-10-24 09:19:44 +0000 (Wed, 24 Oct 2007)
New Revision: 15518
Modified:
trunk/freenet/src/freenet/crypt/DiffieHellman.java
trunk/freenet/src/freenet/node/FNPPacketMangler.java
Log:
JFK:
Strengthen the verification of DH parameters.
See http://securitytracker.com/alerts/2005/Aug/1014739.html for details
Modified: trunk/freenet/src/freenet/crypt/DiffieHellman.java
===================================================================
--- trunk/freenet/src/freenet/crypt/DiffieHellman.java 2007-10-24 08:30:18 UTC
(rev 15517)
+++ trunk/freenet/src/freenet/crypt/DiffieHellman.java 2007-10-24 09:19:44 UTC
(rev 15518)
@@ -6,6 +6,7 @@
package freenet.crypt;
+import java.math.BigInteger;
import java.util.Random;
import java.util.Stack;
@@ -36,6 +37,9 @@
private static Object precalcerWaitObj = new Object();
private static Thread precalcThread;
+
+ public static final BigInteger MIN_EXPONENTIAL_VALUE = new
BigInteger("2").pow(24);
+ public static final BigInteger MAX_EXPONENTIAL_VALUE =
group.getP().subtract(MIN_EXPONENTIAL_VALUE);
static {
precalcThread = new PrecalcBufferFill();
@@ -139,10 +143,52 @@
private static NativeBigInteger[] genParams() {
NativeBigInteger params[] = new NativeBigInteger[2];
// Don't need NativeBigInteger?
- params[0] = new NativeBigInteger(256, r);
- params[1] = (NativeBigInteger) group.getG().modPow(params[0],
group.getP());
+
+ do {
+ params[0] = new NativeBigInteger(256, r);
+ params[1] = (NativeBigInteger)
group.getG().modPow(params[0], group.getP());
+ }
while(!DiffieHellman.checkDHExponentialValidity(DiffieHellman.class,
params[1]));
+
return params;
}
+
+ /**
+ * Check the validity of a DH exponential
+ *
+ * @param a BigInteger: The exponential to test
+ * @return a boolean: whether the DH exponential provided is acceptable
or not
+ *
+ * @see http://securitytracker.com/alerts/2005/Aug/1014739.html
+ */
+ public static boolean checkDHExponentialValidity(Class caller,
BigInteger exponential) {
+ int onesCount=0, zerosCount=0;
+
+ // Ensure that we have at least 16 bits of each gender
+ for(int i=0; i < exponential.bitLength(); i++)
+ if(exponential.testBit(i))
+ onesCount++;
+ else
+ zerosCount++;
+ if((onesCount<16) || (zerosCount<16)) {
+ Logger.error(caller, "The provided exponential contains
"+zerosCount+" zeros and "+onesCount+" ones wich is unacceptable!");
+ return false;
+ }
+
+ //TODO: Shall we test if p-1 = -1 here ?
+
+ // Ensure that g^x > 2^24
+ if(MIN_EXPONENTIAL_VALUE.compareTo(exponential) > -1) {
+ Logger.error(caller, "The provided exponential is
smaller than 2^24 which is unacceptable!");
+ return false;
+ }
+ // Ensure that g^x < (p - 2^24)
+ if(MAX_EXPONENTIAL_VALUE.compareTo(exponential) < 1) {
+ Logger.error(DiffieHellman.class, "The provided
exponential is bigger than (p - 2^24) which is unacceptable!");
+ return false;
+ }
+
+ return true;
+ }
public static DHGroup getGroup() {
return group;
Modified: trunk/freenet/src/freenet/node/FNPPacketMangler.java
===================================================================
--- trunk/freenet/src/freenet/node/FNPPacketMangler.java 2007-10-24
08:30:18 UTC (rev 15517)
+++ trunk/freenet/src/freenet/node/FNPPacketMangler.java 2007-10-24
09:19:44 UTC (rev 15518)
@@ -492,10 +492,10 @@
byte[] hisExponential = new
byte[DiffieHellman.modulusLengthInBytes()];
System.arraycopy(payload, offset, hisExponential, 0,
DiffieHellman.modulusLengthInBytes());
NativeBigInteger _hisExponential = new
NativeBigInteger(1,hisExponential);
- if(_hisExponential.compareTo(NativeBigInteger.ONE) > 0) {
+ if(DiffieHellman.checkDHExponentialValidity(this.getClass(),
_hisExponential)) {
sendJFKMessage2(nonceInitiator, hisExponential, pn,
replyTo);
}else
- Logger.error(this, "We can't accept the exponential
"+pn+" sent us; it's smaller than 1!!");
+ Logger.error(this, "We can't accept the exponential
"+pn+" sent us!!");
long t2=System.currentTimeMillis();
if((t2-t1)>500)
@@ -671,8 +671,8 @@
return;
}
- if(_hisExponential.compareTo(NativeBigInteger.ONE) < 1) {
- Logger.error(this, "We can't accept the exponential
"+pn+" sent us; it's smaller than 1!!");
+ if(!DiffieHellman.checkDHExponentialValidity(this.getClass(),
_hisExponential)) {
+ Logger.error(this, "We can't accept the exponential
"+pn+" sent us!!");
return;
}
