ThreadError Mac::ProcessReceiveSecurity(const Address &aSrcAddr, Neighbor *aNeighbor)
{
ThreadError error = kThreadError_None;
uint8_t securityLevel;
uint32_t frameCounter;
uint8_t nonce[kNonceSize];
uint8_t tag[Frame::kMaxMicSize];
uint8_t tagLength;
uint8_t keyid;
uint32_t keySequence;
const uint8_t *macKey;
Crypto::AesCcm aesCcm;
mReceiveFrame.SetSecurityValid(false);
if (mReceiveFrame.GetSecurityEnabled() == false)
{
ExitNow();
}
VerifyOrExit(aNeighbor != NULL, error = kThreadError_Security);
mReceiveFrame.GetSecurityLevel(securityLevel);
mReceiveFrame.GetFrameCounter(frameCounter);
GenerateNonce(aSrcAddr.mExtAddress, frameCounter, securityLevel, nonce);
tagLength = mReceiveFrame.GetFooterLength() - Frame::kFcsSize;
mReceiveFrame.GetKeyId(keyid);
keyid--;
if (keyid == (mKeyManager.GetCurrentKeySequence() & 0x7f))
{
// same key index
keySequence = mKeyManager.GetCurrentKeySequence();
macKey = mKeyManager.GetCurrentMacKey();
VerifyOrExit(aNeighbor->mPreviousKey == true || frameCounter >= aNeighbor->mValid.mLinkFrameCounter,
error = kThreadError_Security);
}
else if (aNeighbor->mPreviousKey &&
mKeyManager.IsPreviousKeyValid() &&
keyid == (mKeyManager.GetPreviousKeySequence() & 0x7f))
{
// previous key index
keySequence = mKeyManager.GetPreviousKeySequence();
macKey = mKeyManager.GetPreviousMacKey();
VerifyOrExit(frameCounter >= aNeighbor->mValid.mLinkFrameCounter, error = kThreadError_Security);
}
else if (keyid == ((mKeyManager.GetCurrentKeySequence() + 1) & 0x7f))
{
// next key index
keySequence = mKeyManager.GetCurrentKeySequence() + 1;
macKey = mKeyManager.GetTemporaryMacKey(keySequence);
}
else
{
for (Receiver *receiver = mReceiveHead; receiver; receiver = receiver->mNext)
{
receiver->HandleReceivedFrame(mReceiveFrame, kThreadError_Security);
}
ExitNow(error = kThreadError_Security);
}
aesCcm.SetKey(macKey, 16);
aesCcm.Init(mReceiveFrame.GetHeaderLength(), mReceiveFrame.GetPayloadLength(),
tagLength, nonce, sizeof(nonce));
aesCcm.Header(mReceiveFrame.GetHeader(), mReceiveFrame.GetHeaderLength());
aesCcm.Payload(mReceiveFrame.GetPayload(), mReceiveFrame.GetPayload(), mReceiveFrame.GetPayloadLength(),
false);
aesCcm.Finalize(tag, &tagLength);
VerifyOrExit(memcmp(tag, mReceiveFrame.GetFooter(), tagLength) == 0, error = kThreadError_Security);
if (keySequence > mKeyManager.GetCurrentKeySequence())
{
mKeyManager.SetCurrentKeySequence(keySequence);
}
if (keySequence == mKeyManager.GetCurrentKeySequence())
{
aNeighbor->mPreviousKey = false;
}
aNeighbor->mValid.mLinkFrameCounter = frameCounter + 1;
mReceiveFrame.SetSecurityValid(true);
exit:
return error;
}
