Require callers of AcceptBlockHeader() to perform anti-dos checks

In order to prevent memory DoS, we must ensure that we don't accept a new
header into memory until we've performed anti-DoS checks, such as verifying
that the header is part of a sufficiently high work chain. This commit adds a
new argument to AcceptBlockHeader() so that we can ensure that all call-sites
which might cause a new header to be accepted into memory have to grapple with
the question of whether the header is safe to accept, or needs further
validation.

This patch also fixes two places where low-difficulty-headers could have been
processed without such validation (processing an unrequested block from the
network, and processing a compact block).

Credit to Niklas Gögge for noticing this issue, and thanks to Sjors Provoost
for test code.

8 files changed, 15 insertions, 15 deletions

diff --git a/src/test/blockfilter_index_tests.cpp b/src/test/blockfilter_index_tests.cpp
index 1a182209b8..2798e998af 100644
--- a/src/test/blockfilter_index_tests.cpp
+++ b/src/test/blockfilter_index_tests.cpp
@@ -101,7 +101,7 @@ bool BuildChainTestingSetup::BuildChain(const CBlockIndex* pindex,
         CBlockHeader header = block->GetBlockHeader();
 
         BlockValidationState state;
-        if (!Assert(m_node.chainman)->ProcessNewBlockHeaders({header}, state, &pindex)) {
+        if (!Assert(m_node.chainman)->ProcessNewBlockHeaders({header}, true, state, &pindex)) {
             return false;
         }
     }
@@ -178,7 +178,7 @@ BOOST_FIXTURE_TEST_CASE(blockfilter_index_initial_sync, BuildChainTestingSetup)
     uint256 chainA_last_header = last_header;
     for (size_t i = 0; i < 2; i++) {
         const auto& block = chainA[i];
-        BOOST_REQUIRE(Assert(m_node.chainman)->ProcessNewBlock(block, true, nullptr));
+        BOOST_REQUIRE(Assert(m_node.chainman)->ProcessNewBlock(block, true, true, nullptr));
     }
     for (size_t i = 0; i < 2; i++) {
         const auto& block = chainA[i];
@@ -196,7 +196,7 @@ BOOST_FIXTURE_TEST_CASE(blockfilter_index_initial_sync, BuildChainTestingSetup)
     uint256 chainB_last_header = last_header;
     for (size_t i = 0; i < 3; i++) {
         const auto& block = chainB[i];
-        BOOST_REQUIRE(Assert(m_node.chainman)->ProcessNewBlock(block, true, nullptr));
+        BOOST_REQUIRE(Assert(m_node.chainman)->ProcessNewBlock(block, true, true, nullptr));
     }
     for (size_t i = 0; i < 3; i++) {
         const auto& block = chainB[i];
@@ -227,7 +227,7 @@ BOOST_FIXTURE_TEST_CASE(blockfilter_index_initial_sync, BuildChainTestingSetup)
     // Reorg back to chain A.
      for (size_t i = 2; i < 4; i++) {
          const auto& block = chainA[i];
-         BOOST_REQUIRE(Assert(m_node.chainman)->ProcessNewBlock(block, true, nullptr));
+         BOOST_REQUIRE(Assert(m_node.chainman)->ProcessNewBlock(block, true, true, nullptr));
      }
 
      // Check that chain A and B blocks can be retrieved.
diff --git a/src/test/coinstatsindex_tests.cpp b/src/test/coinstatsindex_tests.cpp
index c93d05a93b..132c4e53e7 100644
--- a/src/test/coinstatsindex_tests.cpp
+++ b/src/test/coinstatsindex_tests.cpp
@@ -102,7 +102,7 @@ BOOST_FIXTURE_TEST_CASE(coinstatsindex_unclean_shutdown, TestChain100Setup)
             LOCK(cs_main);
             BlockValidationState state;
             BOOST_CHECK(CheckBlock(block, state, params.GetConsensus()));
-            BOOST_CHECK(chainstate.AcceptBlock(new_block, state, &new_block_index, true, nullptr, nullptr));
+            BOOST_CHECK(chainstate.AcceptBlock(new_block, state, &new_block_index, true, nullptr, nullptr, true));
             CCoinsViewCache view(&chainstate.CoinsTip());
             BOOST_CHECK(chainstate.ConnectBlock(block, state, new_block_index, view));
         }
diff --git a/src/test/fuzz/utxo_snapshot.cpp b/src/test/fuzz/utxo_snapshot.cpp
index 0b596492be..8abb943266 100644
--- a/src/test/fuzz/utxo_snapshot.cpp
+++ b/src/test/fuzz/utxo_snapshot.cpp
@@ -58,7 +58,7 @@ FUZZ_TARGET_INIT(utxo_snapshot, initialize_chain)
     if (fuzzed_data_provider.ConsumeBool()) {
         for (const auto& block : *g_chain) {
             BlockValidationState dummy;
-            bool processed{chainman.ProcessNewBlockHeaders({*block}, dummy)};
+            bool processed{chainman.ProcessNewBlockHeaders({*block}, true, dummy)};
             Assert(processed);
             const auto* index{WITH_LOCK(::cs_main, return chainman.m_blockman.LookupBlockIndex(block->GetHash()))};
             Assert(index);
diff --git a/src/test/miner_tests.cpp b/src/test/miner_tests.cpp
index d88aed7d4a..9f5fb17b60 100644
--- a/src/test/miner_tests.cpp
+++ b/src/test/miner_tests.cpp
@@ -588,7 +588,7 @@ BOOST_AUTO_TEST_CASE(CreateNewBlock_validity)
             pblock->nNonce = bi.nonce;
         }
         std::shared_ptr<const CBlock> shared_pblock = std::make_shared<const CBlock>(*pblock);
-        BOOST_CHECK(Assert(m_node.chainman)->ProcessNewBlock(shared_pblock, true, nullptr));
+        BOOST_CHECK(Assert(m_node.chainman)->ProcessNewBlock(shared_pblock, true, true, nullptr));
         pblock->hashPrevBlock = pblock->GetHash();
     }
 
diff --git a/src/test/util/mining.cpp b/src/test/util/mining.cpp
index 88cf9647e7..faa0b2878c 100644
--- a/src/test/util/mining.cpp
+++ b/src/test/util/mining.cpp
@@ -68,7 +68,7 @@ CTxIn MineBlock(const NodeContext& node, const CScript& coinbase_scriptPubKey)
         assert(block->nNonce);
     }
 
-    bool processed{Assert(node.chainman)->ProcessNewBlock(block, true, nullptr)};
+    bool processed{Assert(node.chainman)->ProcessNewBlock(block, true, true, nullptr)};
     assert(processed);
 
     return CTxIn{block->vtx[0]->GetHash(), 0};
diff --git a/src/test/util/setup_common.cpp b/src/test/util/setup_common.cpp
index 30d26ecf79..8a0b03c9d1 100644
--- a/src/test/util/setup_common.cpp
+++ b/src/test/util/setup_common.cpp
@@ -321,7 +321,7 @@ CBlock TestChain100Setup::CreateAndProcessBlock(
 
     const CBlock block = this->CreateBlock(txns, scriptPubKey, *chainstate);
     std::shared_ptr<const CBlock> shared_pblock = std::make_shared<const CBlock>(block);
-    Assert(m_node.chainman)->ProcessNewBlock(shared_pblock, true, nullptr);
+    Assert(m_node.chainman)->ProcessNewBlock(shared_pblock, true, true, nullptr);
 
     return block;
 }
diff --git a/src/test/validation_block_tests.cpp b/src/test/validation_block_tests.cpp
index 1c5ca18759..bb1ade153a 100644
--- a/src/test/validation_block_tests.cpp
+++ b/src/test/validation_block_tests.cpp
@@ -100,7 +100,7 @@ std::shared_ptr<CBlock> MinerTestingSetup::FinalizeBlock(std::shared_ptr<CBlock>
     // submit block header, so that miner can get the block height from the
     // global state and the node has the topology of the chain
     BlockValidationState ignored;
-    BOOST_CHECK(Assert(m_node.chainman)->ProcessNewBlockHeaders({pblock->GetBlockHeader()}, ignored));
+    BOOST_CHECK(Assert(m_node.chainman)->ProcessNewBlockHeaders({pblock->GetBlockHeader()}, true, ignored));
 
     return pblock;
 }
@@ -157,7 +157,7 @@ BOOST_AUTO_TEST_CASE(processnewblock_signals_ordering)
 
     bool ignored;
     // Connect the genesis block and drain any outstanding events
-    BOOST_CHECK(Assert(m_node.chainman)->ProcessNewBlock(std::make_shared<CBlock>(Params().GenesisBlock()), true, &ignored));
+    BOOST_CHECK(Assert(m_node.chainman)->ProcessNewBlock(std::make_shared<CBlock>(Params().GenesisBlock()), true, true, &ignored));
     SyncWithValidationInterfaceQueue();
 
     // subscribe to events (this subscriber will validate event ordering)
@@ -179,13 +179,13 @@ BOOST_AUTO_TEST_CASE(processnewblock_signals_ordering)
             FastRandomContext insecure;
             for (int i = 0; i < 1000; i++) {
                 auto block = blocks[insecure.randrange(blocks.size() - 1)];
-                Assert(m_node.chainman)->ProcessNewBlock(block, true, &ignored);
+                Assert(m_node.chainman)->ProcessNewBlock(block, true, true, &ignored);
             }
 
             // to make sure that eventually we process the full chain - do it here
             for (const auto& block : blocks) {
                 if (block->vtx.size() == 1) {
-                    bool processed = Assert(m_node.chainman)->ProcessNewBlock(block, true, &ignored);
+                    bool processed = Assert(m_node.chainman)->ProcessNewBlock(block, true, true, &ignored);
                     assert(processed);
                 }
             }
@@ -224,7 +224,7 @@ BOOST_AUTO_TEST_CASE(mempool_locks_reorg)
 {
     bool ignored;
     auto ProcessBlock = [&](std::shared_ptr<const CBlock> block) -> bool {
-        return Assert(m_node.chainman)->ProcessNewBlock(block, /*force_processing=*/true, /*new_block=*/&ignored);
+        return Assert(m_node.chainman)->ProcessNewBlock(block, /*force_processing=*/true, /*min_pow_checked=*/true, /*new_block=*/&ignored);
     };
 
     // Process all mined blocks
diff --git a/src/test/validation_chainstate_tests.cpp b/src/test/validation_chainstate_tests.cpp
index ee60f9aa4d..98294b9028 100644
--- a/src/test/validation_chainstate_tests.cpp
+++ b/src/test/validation_chainstate_tests.cpp
@@ -132,7 +132,7 @@ BOOST_FIXTURE_TEST_CASE(chainstate_update_tip, TestChain100Setup)
         bool checked = CheckBlock(*pblock, state, chainparams.GetConsensus());
         BOOST_CHECK(checked);
         bool accepted = background_cs.AcceptBlock(
-            pblock, state, &pindex, true, nullptr, &newblock);
+            pblock, state, &pindex, true, nullptr, &newblock, true);
         BOOST_CHECK(accepted);
     }
     // UpdateTip is called here