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Code Issues Projects Releases Wiki Activity

Rewrote EC key encoding and added fuzzing tests to track down bug #33.

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This commit is contained in:
akwizgran
2014-01-05 21:25:56 +00:00
parent 3779f6ea8b
commit bf1a72c826
5 changed files with 90 additions and 24 deletions
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4
briar-core/src/net/sf/briar/crypto/Sec1KeyParser.java
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@@ -28,7 +28,7 @@ class Sec1KeyParser implements KeyParser {
this.params = params;
this.modulus = modulus;
this.keyBits = keyBits;
bytesPerInt = (int) Math.ceil(keyBits / 8.0);
bytesPerInt = keyBits + 7 / 8;
publicKeyBytes = 1 + 2 * bytesPerInt;
privateKeyBytes = bytesPerInt;
}
@@ -47,7 +47,7 @@ class Sec1KeyParser implements KeyParser {
if(x.compareTo(modulus) >= 0) throw new GeneralSecurityException();
// The y co-ordinate must be >= 0 and < q
byte[] yBytes = new byte[bytesPerInt];
System.arraycopy(encodedKey, bytesPerInt + 1, yBytes, 0, bytesPerInt);
System.arraycopy(encodedKey, 1 + bytesPerInt, yBytes, 0, bytesPerInt);
BigInteger y = new BigInteger(1, yBytes); // Positive signum
if(y.compareTo(modulus) >= 0) throw new GeneralSecurityException();
// Verify that y^2 == x^3 + ax + b (mod p)

15
briar-core/src/net/sf/briar/crypto/Sec1PrivateKey.java
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@@ -1,7 +1,5 @@
package net.sf.briar.crypto;
import java.math.BigInteger;
import net.sf.briar.api.crypto.PrivateKey;
import org.spongycastle.crypto.params.ECPrivateKeyParameters;
@@ -9,20 +7,17 @@ import org.spongycastle.crypto.params.ECPrivateKeyParameters;
class Sec1PrivateKey implements PrivateKey {
private final ECPrivateKeyParameters key;
private final int privateKeyBytes;
private final int bytesPerInt;
Sec1PrivateKey(ECPrivateKeyParameters key, int keyBits) {
this.key = key;
privateKeyBytes = (int) Math.ceil(keyBits / 8.0);
bytesPerInt = keyBits + 7 / 8;
}
public byte[] getEncoded() {
byte[] encodedKey = new byte[privateKeyBytes];
BigInteger d = key.getD();
// Copy up to privateKeyBytes bytes into exactly privateKeyBytes bytes
byte[] dBytes = d.toByteArray();
for(int i = 0; i < dBytes.length && i < privateKeyBytes; i++)
encodedKey[privateKeyBytes - 1 - i] = dBytes[dBytes.length - 1 - i];
byte[] encodedKey = new byte[bytesPerInt];
byte[] d = key.getD().toByteArray();
Sec1Utils.convertToFixedLength(d, encodedKey, bytesPerInt, 0);
return encodedKey;
}

18
briar-core/src/net/sf/briar/crypto/Sec1PublicKey.java
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@@ -1,7 +1,5 @@
package net.sf.briar.crypto;
import java.math.BigInteger;
import net.sf.briar.api.crypto.PublicKey;
import org.spongycastle.crypto.params.ECPublicKeyParameters;
@@ -18,22 +16,18 @@ class Sec1PublicKey implements PublicKey {
Sec1PublicKey(ECPublicKeyParameters key, int keyBits) {
this.key = key;
bytesPerInt = (int) Math.ceil(keyBits / 8.0);
bytesPerInt = keyBits + 7 / 8;
publicKeyBytes = 1 + 2 * bytesPerInt;
}
public byte[] getEncoded() {
byte[] encodedKey = new byte[publicKeyBytes];
encodedKey[0] = 4;
BigInteger x = key.getQ().getX().toBigInteger();
BigInteger y = key.getQ().getY().toBigInteger();
// Copy up to bytesPerInt bytes into exactly bytesPerInt bytes
byte[] xBytes = x.toByteArray();
for(int i = 0; i < xBytes.length && i < bytesPerInt; i++)
encodedKey[bytesPerInt - i] = xBytes[xBytes.length - 1 - i];
byte[] yBytes = y.toByteArray();
for(int i = 0; i < yBytes.length && i < bytesPerInt; i++)
encodedKey[2 * bytesPerInt - i] = yBytes[yBytes.length - 1 - i];
byte[] x = key.getQ().getX().toBigInteger().toByteArray();
Sec1Utils.convertToFixedLength(x, encodedKey, bytesPerInt, 1);
byte[] y = key.getQ().getY().toBigInteger().toByteArray();
Sec1Utils.convertToFixedLength(y, encodedKey, bytesPerInt,
1 + bytesPerInt);
return encodedKey;
}

15
briar-core/src/net/sf/briar/crypto/Sec1Utils.java Normal file
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@@ -0,0 +1,15 @@
package net.sf.briar.crypto;
class Sec1Utils {
static void convertToFixedLength(byte[] src, byte[] dest, int destLen,
int destOff) {
if(src.length < destLen) {
destOff += destLen - src.length;
System.arraycopy(src, 0, dest, destOff, src.length);
} else {
int srcOff = src.length - destLen;
System.arraycopy(src, srcOff, dest, destOff, destLen);
}
}
}

62
briar-tests/src/net/sf/briar/crypto/KeyEncodingAndParsingTest.java
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@@ -1,6 +1,10 @@
package net.sf.briar.crypto;
import static org.junit.Assert.assertArrayEquals;
import java.security.GeneralSecurityException;
import java.util.Random;
import net.sf.briar.BriarTestCase;
import net.sf.briar.api.crypto.KeyPair;
import net.sf.briar.api.crypto.KeyParser;
@@ -47,6 +51,35 @@ public class KeyEncodingAndParsingTest extends BriarTestCase {
assertArrayEquals(secret, secret1);
}
@Test
public void testAgreementKeyParserByFuzzing() throws Exception {
KeyParser parser = crypto.getAgreementKeyParser();
// Generate a key pair to get the proper public key length
KeyPair p = crypto.generateAgreementKeyPair();
int pubLength = p.getPublic().getEncoded().length;
int privLength = p.getPrivate().getEncoded().length;
// Parse some random byte arrays - expect GeneralSecurityException
Random random = new Random();
byte[] pubFuzz = new byte[pubLength];
byte[] privFuzz = new byte[privLength];
for(int i = 0; i < 1000; i++) {
random.nextBytes(pubFuzz);
try {
parser.parsePublicKey(pubFuzz);
} catch(GeneralSecurityException expected) {
} catch(Exception e) {
fail();
}
random.nextBytes(privFuzz);
try {
parser.parsePrivateKey(privFuzz);
} catch(GeneralSecurityException expected) {
} catch(Exception e) {
fail();
}
}
}
@Test
public void testSignaturePublicKeyEncodingAndParsing() throws Exception {
KeyParser parser = crypto.getSignatureKeyParser();
@@ -80,4 +113,33 @@ public class KeyEncodingAndParsingTest extends BriarTestCase {
byte[] secret1 = crypto.deriveSharedSecret(bPriv, aPair.getPublic());
assertArrayEquals(secret, secret1);
}
@Test
public void testSignatureKeyParserByFuzzing() throws Exception {
KeyParser parser = crypto.getSignatureKeyParser();
// Generate a key pair to get the proper public key length
KeyPair p = crypto.generateSignatureKeyPair();
int pubLength = p.getPublic().getEncoded().length;
int privLength = p.getPrivate().getEncoded().length;
// Parse some random byte arrays - expect GeneralSecurityException
Random random = new Random();
byte[] pubFuzz = new byte[pubLength];
byte[] privFuzz = new byte[privLength];
for(int i = 0; i < 1000; i++) {
random.nextBytes(pubFuzz);
try {
parser.parsePublicKey(pubFuzz);
} catch(GeneralSecurityException expected) {
} catch(Exception e) {
fail();
}
random.nextBytes(privFuzz);
try {
parser.parsePrivateKey(privFuzz);
} catch(GeneralSecurityException expected) {
} catch(Exception e) {
fail();
}
}
}
}