[mrp] Fix #17471 - send standalone ack before crypto ops in CASE and PASE.

src/lib/core/CHIPConfig.h

@@ -707,6 +707,17 @@
 #define CHIP_CONFIG_MAX_GROUP_CONTROL_PEERS 2
 #endif // CHIP_CONFIG_MAX_GROUP_CONTROL_PEER
 
+/**
+ *  @def CHIP_CONFIG_SLOW_CRYPTO
+ *
+ *  @brief
+ *   When enabled, CASE and PASE setup will proactively send standalone acknowledgements
+ *   prior to engaging in crypto operations.
+ */
+#ifndef CHIP_CONFIG_SLOW_CRYPTO
+#define CHIP_CONFIG_SLOW_CRYPTO 1
+#endif // CHIP_CONFIG_SLOW_CRYPTO
+
 /**
  * @def CHIP_NON_PRODUCTION_MARKER
  *

src/protocols/secure_channel/CASESession.cpp

@@ -1642,6 +1642,15 @@ CHIP_ERROR CASESession::OnMessageReceived(ExchangeContext * ec, const PayloadHea
     Protocols::SecureChannel::MsgType msgType = static_cast<Protocols::SecureChannel::MsgType>(payloadHeader.GetMessageType());
     SuccessOrExit(err);
 
+#if CHIP_CONFIG_SLOW_CRYPTO
+    if (msgType == Protocols::SecureChannel::MsgType::CASE_Sigma1 || msgType == Protocols::SecureChannel::MsgType::CASE_Sigma2 ||
+        msgType == Protocols::SecureChannel::MsgType::CASE_Sigma2Resume ||
+        msgType == Protocols::SecureChannel::MsgType::CASE_Sigma3)
+    {
+        ReturnErrorOnFailure(mExchangeCtxt->SendStandaloneAckMessage());
+    }
+#endif // CHIP_CONFIG_SLOW_CRYPTO
+
     // By default, CHIP_ERROR_INVALID_MESSAGE_TYPE is returned if in the current state
     // a message handler is not defined for the received message type.
     err = CHIP_ERROR_INVALID_MESSAGE_TYPE;

src/protocols/secure_channel/PASESession.cpp

@@ -800,10 +800,19 @@ CHIP_ERROR PASESession::OnUnsolicitedMessageReceived(const PayloadHeader & paylo
 CHIP_ERROR PASESession::OnMessageReceived(ExchangeContext * exchange, const PayloadHeader & payloadHeader,
                                           System::PacketBufferHandle && msg)
 {
-    CHIP_ERROR err = ValidateReceivedMessage(exchange, payloadHeader, msg);
+    CHIP_ERROR err  = ValidateReceivedMessage(exchange, payloadHeader, msg);
+    MsgType msgType = static_cast<MsgType>(payloadHeader.GetMessageType());
     SuccessOrExit(err);
 
-    switch (static_cast<MsgType>(payloadHeader.GetMessageType()))
+#if CHIP_CONFIG_SLOW_CRYPTO
+    if (msgType == MsgType::PBKDFParamRequest || msgType == MsgType::PBKDFParamResponse || msgType == MsgType::PASE_Pake1 ||
+        msgType == MsgType::PASE_Pake2 || msgType == MsgType::PASE_Pake3)
+    {
+        SuccessOrExit(mExchangeCtxt->SendStandaloneAckMessage());
+    }
+#endif // CHIP_CONFIG_SLOW_CRYPTO
+
+    switch (msgType)
     {
     case MsgType::PBKDFParamRequest:
         err = HandlePBKDFParamRequest(std::move(msg));

src/protocols/secure_channel/tests/TestCASESession.cpp

@@ -53,6 +53,14 @@ using namespace chip::Protocols;
 using TestContext = Test::LoopbackMessagingContext;
 
 namespace {
+#if CHIP_CONFIG_SLOW_CRYPTO
+constexpr uint32_t sTestCaseMessageCount           = 8;
+constexpr uint32_t sTestCaseResumptionMessageCount = 6;
+#else  // CHIP_CONFIG_SLOW_CRYPTO
+constexpr uint32_t sTestCaseMessageCount           = 5;
+constexpr uint32_t sTestCaseResumptionMessageCount = 4;
+#endif // CHIP_CONFIG_SLOW_CRYPTO
+
 FabricTable gCommissionerFabrics;
 FabricIndex gCommissionerFabricIndex;
 GroupDataProviderImpl gCommissionerGroupDataProvider;
@@ -283,7 +291,7 @@ void CASE_SecurePairingHandshakeTestCommon(nlTestSuite * inSuite, void * inConte
                                                         MakeOptional(nonSleepyCommissionerRmpConfig)) == CHIP_NO_ERROR);
     ctx.DrainAndServiceIO();
 
-    NL_TEST_ASSERT(inSuite, loopback.mSentMessageCount == 5);
+    NL_TEST_ASSERT(inSuite, loopback.mSentMessageCount == sTestCaseMessageCount);
     NL_TEST_ASSERT(inSuite, delegateAccessory.mNumPairingComplete == 1);
     NL_TEST_ASSERT(inSuite, delegateCommissioner.mNumPairingComplete == 1);
     NL_TEST_ASSERT(inSuite, pairingAccessory.GetRemoteMRPConfig().mIdleRetransTimeout == System::Clock::Milliseconds32(5000));
@@ -335,7 +343,7 @@ void CASE_SecurePairingHandshakeServerTest(nlTestSuite * inSuite, void * inConte
                                                          nullptr, &delegateCommissioner) == CHIP_NO_ERROR);
     ctx.DrainAndServiceIO();
 
-    NL_TEST_ASSERT(inSuite, loopback.mSentMessageCount == 5);
+    NL_TEST_ASSERT(inSuite, loopback.mSentMessageCount == sTestCaseMessageCount);
     NL_TEST_ASSERT(inSuite, delegateCommissioner.mNumPairingComplete == 1);
 
     // Validate that secure session is created
@@ -712,30 +720,32 @@ static void CASE_SessionResumptionStorage(nlTestSuite * inSuite, void * inContex
         // Both peers have a matching session resumption record.
         // This should succeed.
         {
-            .initiatorStorage         = SessionResumptionTestStorage(CHIP_NO_ERROR, responder, &resumptionIdA, &sharedSecretA),
-            .responderStorage         = SessionResumptionTestStorage(CHIP_NO_ERROR, initiator, &resumptionIdA, &sharedSecretA),
-            .expectedSentMessageCount = 4, // we expect this number of sent messages with successful session resumption
+            .initiatorStorage = SessionResumptionTestStorage(CHIP_NO_ERROR, responder, &resumptionIdA, &sharedSecretA),
+            .responderStorage = SessionResumptionTestStorage(CHIP_NO_ERROR, initiator, &resumptionIdA, &sharedSecretA),
+            .expectedSentMessageCount =
+                sTestCaseResumptionMessageCount, // we expect this number of sent messages with successful session resumption
         },
         // Peers have mismatched session resumption records.
         // This should succeed with fall back to CASE.
         {
             .initiatorStorage         = SessionResumptionTestStorage(CHIP_NO_ERROR, responder, &resumptionIdA, &sharedSecretA),
             .responderStorage         = SessionResumptionTestStorage(CHIP_ERROR_KEY_NOT_FOUND),
-            .expectedSentMessageCount = 5, // we expect this number of sent message when we fall back to CASE
+            .expectedSentMessageCount = sTestCaseMessageCount, // we expect this number of sent message when we fall back to CASE
         },
         // Peers both have record of the same resumption ID, but a different shared secret.
         // This should succeed with fall back to CASE.
         {
             .initiatorStorage         = SessionResumptionTestStorage(CHIP_NO_ERROR, responder, &resumptionIdA, &sharedSecretA),
             .responderStorage         = SessionResumptionTestStorage(CHIP_NO_ERROR, initiator, &resumptionIdA, &sharedSecretB),
-            .expectedSentMessageCount = 5, // we expect this number of sent message when we fall back to CASE
+            .expectedSentMessageCount = sTestCaseMessageCount, // we expect this number of sent message when we fall back to CASE
         },
         // Neither peer has a session resumption record.
         // This should succeed - no attempt at session resumption will be made.
         {
-            .initiatorStorage         = SessionResumptionTestStorage(CHIP_ERROR_KEY_NOT_FOUND),
-            .responderStorage         = SessionResumptionTestStorage(CHIP_ERROR_KEY_NOT_FOUND),
-            .expectedSentMessageCount = 5, // we expect this number of sent messages if we do not attempt session resumption
+            .initiatorStorage = SessionResumptionTestStorage(CHIP_ERROR_KEY_NOT_FOUND),
+            .responderStorage = SessionResumptionTestStorage(CHIP_ERROR_KEY_NOT_FOUND),
+            .expectedSentMessageCount =
+                sTestCaseMessageCount, // we expect this number of sent messages if we do not attempt session resumption
         },
     };
 

src/protocols/secure_channel/tests/TestPASESession.cpp

@@ -48,6 +48,12 @@ using namespace chip::Protocols;
 
 namespace {
 
+#if CHIP_CONFIG_SLOW_CRYPTO
+constexpr uint32_t sTestPaseMessageCount = 8;
+#else  // CHIP_CONFIG_SLOW_CRYPTO
+constexpr uint32_t sTestPaseMessageCount = 5;
+#endif // CHIP_CONFIG_SLOW_CRYPTO
+
 // Test Set #01 of Spake2p Parameters (PIN Code, Iteration Count, Salt, and matching Verifier):
 constexpr uint32_t sTestSpake2p01_PinCode        = 20202021;
 constexpr uint32_t sTestSpake2p01_IterationCount = 1000;
@@ -250,7 +256,7 @@ void SecurePairingHandshakeTestCommon(nlTestSuite * inSuite, void * inContext, S
     // via piggybacked acks. So we cannot check for a specific value of mSentMessageCount.
     // Let's make sure atleast number is >= than the minimum messages required to complete the
     // handshake.
-    NL_TEST_ASSERT(inSuite, loopback.mSentMessageCount >= 5);
+    NL_TEST_ASSERT(inSuite, loopback.mSentMessageCount >= sTestPaseMessageCount);
     NL_TEST_ASSERT(inSuite, delegateAccessory.mNumPairingComplete == 1);
     NL_TEST_ASSERT(inSuite, delegateCommissioner.mNumPairingComplete == 1);