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Prevent CMAC from accepting IV #14

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timw wants to merge 1 commit into from
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Prevent CMAC from accepting IV #14

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7 changes: 6 additions & 1 deletion 7 core/src/main/java/org/bouncycastle/crypto/macs/CMac.java
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Original file line number Diff line number Diff line change
Expand Up @@ -5,6 +5,7 @@
import org.bouncycastle.crypto.Mac;
import org.bouncycastle.crypto.modes.CBCBlockCipher;
import org.bouncycastle.crypto.paddings.ISO7816d4Padding;
import org.bouncycastle.crypto.params.KeyParameter;

/**
* CMAC - as specified at www.nuee.nagoya-u.ac.jp/labs/tiwata/omac/omac.html
Expand Down Expand Up @@ -121,7 +122,7 @@ private static byte[] doubleLu(byte[] in)

public void init(CipherParameters params)
{
if (params != null)
if (params instanceof KeyParameter)
{
cipher.init(true, params);

Expand All @@ -130,6 +131,10 @@ public void init(CipherParameters params)
cipher.processBlock(ZEROES, 0, L, 0);
Lu = doubleLu(L);
Lu2 = doubleLu(Lu);
} else if (params != null)
{
// CMAC mode does not permit IV to underlying CBC mode
throw new IllegalArgumentException("CMac mode only permits key to be set.");
}

reset();
Expand Down
17 changes: 17 additions & 0 deletions 17 core/src/test/java/org/bouncycastle/crypto/test/CMacTest.java
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Original file line number Diff line number Diff line change
Expand Up @@ -2,9 +2,11 @@

import org.bouncycastle.crypto.BlockCipher;
import org.bouncycastle.crypto.Mac;
import org.bouncycastle.crypto.engines.AESEngine;
import org.bouncycastle.crypto.engines.AESFastEngine;
import org.bouncycastle.crypto.macs.CMac;
import org.bouncycastle.crypto.params.KeyParameter;
import org.bouncycastle.crypto.params.ParametersWithIV;
import org.bouncycastle.util.encoders.Hex;
import org.bouncycastle.util.test.SimpleTest;

Expand Down Expand Up @@ -248,6 +250,21 @@ public void performTest()
fail("Failed - expected " + new String(Hex.encode(output_k256_m64))
+ " got " + new String(Hex.encode(out)));
}

testExceptions();
}

private void testExceptions()
{
try
{
CMac mac = new CMac(new AESEngine());
mac.init(new ParametersWithIV(new KeyParameter(new byte[16]), new byte[16]));
fail("CMac does not accept IV");
} catch(IllegalArgumentException e)
{
// Expected
}
}

public String getName()
Expand Down
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