Merge #6865: coinjoin/server: validate DSQUEUE denomination; remove redundant time stamp screens; tests: add denom and timestamp coverage

3739540 coinjoin/server: validate DSQUEUE denomination; remove redundant timestamp screens; rely on IsTimeOutOfBounds(); tests: add denom and timestamp coverage (pasta)

Pull request description:

  ## Issue being fixed or feature implemented
  Ensure we believe that a DSQ is fully valid before we broadcast it further; add unit tests

  ## What was done?
    _Describe your changes in detail_

  ## How Has This Been Tested?
    _Please describe in detail how you tested your changes._

    _Include details of your testing environment, and the tests you ran
  to see how your change affects other areas of the code, etc._

  ## Breaking Changes
    _Please describe any breaking changes your code introduces_

  ## Checklist:
    _Go over all the following points, and put an `x` in all the boxes that apply._
  - [ ] I have performed a self-review of my own code
  - [ ] I have commented my code, particularly in hard-to-understand areas
  - [ ] I have added or updated relevant unit/integration/functional/e2e tests
  - [ ] I have made corresponding changes to the documentation
  - [x] I have assigned this pull request to a milestone _(for repository code-owners and collaborators only)_

ACKs for top commit:
  UdjinM6:
    utACK 3739540
  kwvg:
    utACK 3739540

Tree-SHA512: 6e4fe3affcfb002f92044b99acff12f2d2bf03cb1c8dda62000875987145a4162cc7d397dc834ea4ecd883961d480672d079a0ad8d9c134b00c87de93c94d15d

Author: PastaPastaPasta

src/coinjoin/server.cpp

@@ -117,6 +117,13 @@ MessageProcessingResult CCoinJoinServer::ProcessDSQUEUE(NodeId from, CDataStream
     MessageProcessingResult ret{};
     ret.m_to_erase = CInv{MSG_DSQ, dsq.GetHash()};
 
+    // Validate denomination first
+    if (!CoinJoin::IsValidDenomination(dsq.nDenom)) {
+        LogPrint(BCLog::COINJOIN, "DSQUEUE -- invalid denomination %d from peer %d\n", dsq.nDenom, from);
+        ret.m_error = MisbehavingError{10};
+        return ret;
+    }
+
     if (dsq.masternodeOutpoint.IsNull() && dsq.m_protxHash.IsNull()) {
         ret.m_error = MisbehavingError{100};
         return ret;

src/test/coinjoin_queue_tests.cpp

@@ -53,4 +53,46 @@ BOOST_AUTO_TEST_CASE(queue_hashes_and_equality)
     BOOST_CHECK(a.GetSignatureHash() == b.GetSignatureHash());
 }
 
+BOOST_AUTO_TEST_CASE(queue_denomination_validation)
+{
+    // Test that valid denominations pass
+    int validDenom = CoinJoin::AmountToDenomination(CoinJoin::GetSmallestDenomination());
+    BOOST_CHECK(CoinJoin::IsValidDenomination(validDenom));
+
+    // Test that invalid denominations fail
+    BOOST_CHECK(!CoinJoin::IsValidDenomination(0));     // Zero
+    BOOST_CHECK(!CoinJoin::IsValidDenomination(-1));    // Negative
+    BOOST_CHECK(!CoinJoin::IsValidDenomination(999));   // Invalid value
+}
+
+BOOST_AUTO_TEST_CASE(queue_timestamp_validation)
+{
+    CCoinJoinQueue q;
+    q.nDenom = CoinJoin::AmountToDenomination(CoinJoin::GetSmallestDenomination());
+    q.masternodeOutpoint = COutPoint(uint256S("cc"), 3);
+    q.m_protxHash = uint256::ONE;
+
+    int64_t current_time = GetAdjustedTime();
+
+    // Test valid timestamp (current time)
+    q.nTime = current_time;
+    BOOST_CHECK(!q.IsTimeOutOfBounds(current_time));
+
+    // Test timestamp slightly in future (within COINJOIN_QUEUE_TIMEOUT = 30)
+    q.nTime = current_time + 15; // 15 seconds in future
+    BOOST_CHECK(!q.IsTimeOutOfBounds(current_time));
+
+    // Test timestamp slightly in past (within COINJOIN_QUEUE_TIMEOUT = 30)
+    q.nTime = current_time - 15; // 15 seconds ago
+    BOOST_CHECK(!q.IsTimeOutOfBounds(current_time));
+
+    // Test timestamp too far in future (outside COINJOIN_QUEUE_TIMEOUT = 30)
+    q.nTime = current_time + 60; // 60 seconds in future
+    BOOST_CHECK(q.IsTimeOutOfBounds(current_time));
+
+    // Test timestamp too far in past (outside COINJOIN_QUEUE_TIMEOUT = 30)
+    q.nTime = current_time - 60; // 60 seconds ago
+    BOOST_CHECK(q.IsTimeOutOfBounds(current_time));
+}
+
 BOOST_AUTO_TEST_SUITE_END()