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KCCM partial AEAD block #2350

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tonywasher wants to merge 2 commits into from
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KCCM partial AEAD block #2350

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151905d
KCCM enable partial AEADData support
tonywasher Jul 11, 2026
997af34
KCCM ensure nonce is at least blockSize
tonywasher Jul 11, 2026
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17 changes: 10 additions & 7 deletions core/src/main/java/org/bouncycastle/crypto/modes/KCCMBlockCipher.java
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Original file line number Diff line number Diff line change
Expand Up @@ -156,6 +156,14 @@ else if (params instanceof ParametersWithIV)
throw new IllegalArgumentException("invalid parameters passed to KCCM");
}

// TODO Nonce length validation. Should it always be engineBlockSize?
if (newNonce.length < engine.getBlockSize())
{
byte[] tmp = new byte[engine.getBlockSize()];
System.arraycopy(newNonce, 0, tmp, 0, newNonce.length);
newNonce = tmp;
}

// RFC 5116 sec. 2.1 requires a distinct nonce per AEAD encryption under a given key; the
// DSTU 7624 CCM construction inherits this CCM rule (cf. NIST SP 800-38C), and reuse is
// catastrophic (CTR keystream reuse plus a forgeable CBC-MAC). That obligation is the
Expand Down Expand Up @@ -216,11 +224,6 @@ private void processAssociatedText()

boolean hasAssocText = aadLen > 0;

if (hasAssocText && aadLen % engine.getBlockSize() != 0)
{
throw new IllegalArgumentException("padding not supported");
}

// The G1 block binds the nonce, data length and MAC-size flag into the MAC and must be
// processed unconditionally. DSTU 7624 carries the associated-data-present indicator as a flag
// bit inside G1, so it is not a gate on computing G1: skipping G1 when no AAD is present leaves
Expand Down Expand Up @@ -271,9 +274,9 @@ private void processAssociatedText()

int assocOff = 0;
int authLen = aadLen;
while (authLen != 0)
while (authLen > 0)
{
for (int byteIndex = 0; byteIndex < engine.getBlockSize(); byteIndex++)
for (int byteIndex = 0; byteIndex < engine.getBlockSize() && byteIndex < authLen - assocOff; byteIndex++)
{
macBlock[byteIndex] ^= aad[byteIndex + assocOff];
}
Expand Down