1 files changed, 56 insertions, 10 deletions

diff --git a/src/validation.cpp b/src/validation.cpp
index 0834dbe5a4..a2a339a5a1 100644
--- a/src/validation.cpp
+++ b/src/validation.cpp
@@ -2944,7 +2944,7 @@ static bool NotifyHeaderTip(CChainState& chainstate) LOCKS_EXCLUDED(cs_main) {
     }
     // Send block tip changed notifications without cs_main
     if (fNotify) {
-        uiInterface.NotifyHeaderTip(GetSynchronizationState(fInitialBlockDownload), pindexHeader);
+        uiInterface.NotifyHeaderTip(GetSynchronizationState(fInitialBlockDownload), pindexHeader->nHeight, pindexHeader->nTime, false);
     }
     return fNotify;
 }
@@ -3432,6 +3432,22 @@ std::vector<unsigned char> ChainstateManager::GenerateCoinbaseCommitment(CBlock&
     return commitment;
 }
 
+bool HasValidProofOfWork(const std::vector<CBlockHeader>& headers, const Consensus::Params& consensusParams)
+{
+    return std::all_of(headers.cbegin(), headers.cend(),
+            [&](const auto& header) { return CheckProofOfWork(header.GetHash(), header.nBits, consensusParams);});
+}
+
+arith_uint256 CalculateHeadersWork(const std::vector<CBlockHeader>& headers)
+{
+    arith_uint256 total_work{0};
+    for (const CBlockHeader& header : headers) {
+        CBlockIndex dummy(header);
+        total_work += GetBlockProof(dummy);
+    }
+    return total_work;
+}
+
 /** Context-dependent validity checks.
  *  By "context", we mean only the previous block headers, but not the UTXO
  *  set; UTXO-related validity checks are done in ConnectBlock().
@@ -3572,9 +3588,10 @@ static bool ContextualCheckBlock(const CBlock& block, BlockValidationState& stat
     return true;
 }
 
-bool ChainstateManager::AcceptBlockHeader(const CBlockHeader& block, BlockValidationState& state, CBlockIndex** ppindex)
+bool ChainstateManager::AcceptBlockHeader(const CBlockHeader& block, BlockValidationState& state, CBlockIndex** ppindex, bool min_pow_checked)
 {
     AssertLockHeld(cs_main);
+
     // Check for duplicate
     uint256 hash = block.GetHash();
     BlockMap::iterator miSelf{m_blockman.m_block_index.find(hash)};
@@ -3652,6 +3669,10 @@ bool ChainstateManager::AcceptBlockHeader(const CBlockHeader& block, BlockValida
             }
         }
     }
+    if (!min_pow_checked) {
+        LogPrint(BCLog::VALIDATION, "%s: not adding new block header %s, missing anti-dos proof-of-work validation\n", __func__, hash.ToString());
+        return state.Invalid(BlockValidationResult::BLOCK_HEADER_LOW_WORK, "too-little-chainwork");
+    }
     CBlockIndex* pindex{m_blockman.AddToBlockIndex(block, m_best_header)};
 
     if (ppindex)
@@ -3661,14 +3682,14 @@ bool ChainstateManager::AcceptBlockHeader(const CBlockHeader& block, BlockValida
 }
 
 // Exposed wrapper for AcceptBlockHeader
-bool ChainstateManager::ProcessNewBlockHeaders(const std::vector<CBlockHeader>& headers, BlockValidationState& state, const CBlockIndex** ppindex)
+bool ChainstateManager::ProcessNewBlockHeaders(const std::vector<CBlockHeader>& headers, bool min_pow_checked, BlockValidationState& state, const CBlockIndex** ppindex)
 {
     AssertLockNotHeld(cs_main);
     {
         LOCK(cs_main);
         for (const CBlockHeader& header : headers) {
             CBlockIndex *pindex = nullptr; // Use a temp pindex instead of ppindex to avoid a const_cast
-            bool accepted{AcceptBlockHeader(header, state, &pindex)};
+            bool accepted{AcceptBlockHeader(header, state, &pindex, min_pow_checked)};
             ActiveChainstate().CheckBlockIndex();
 
             if (!accepted) {
@@ -3690,8 +3711,33 @@ bool ChainstateManager::ProcessNewBlockHeaders(const std::vector<CBlockHeader>&
     return true;
 }
 
+void ChainstateManager::ReportHeadersPresync(const arith_uint256& work, int64_t height, int64_t timestamp)
+{
+    AssertLockNotHeld(cs_main);
+    const auto& chainstate = ActiveChainstate();
+    {
+        LOCK(cs_main);
+        // Don't report headers presync progress if we already have a post-minchainwork header chain.
+        // This means we lose reporting for potentially legimate, but unlikely, deep reorgs, but
+        // prevent attackers that spam low-work headers from filling our logs.
+        if (m_best_header->nChainWork >= UintToArith256(GetConsensus().nMinimumChainWork)) return;
+        // Rate limit headers presync updates to 4 per second, as these are not subject to DoS
+        // protection.
+        auto now = std::chrono::steady_clock::now();
+        if (now < m_last_presync_update + std::chrono::milliseconds{250}) return;
+        m_last_presync_update = now;
+    }
+    bool initial_download = chainstate.IsInitialBlockDownload();
+    uiInterface.NotifyHeaderTip(GetSynchronizationState(initial_download), height, timestamp, /*presync=*/true);
+    if (initial_download) {
+        const int64_t blocks_left{(GetTime() - timestamp) / GetConsensus().nPowTargetSpacing};
+        const double progress{100.0 * height / (height + blocks_left)};
+        LogPrintf("Pre-synchronizing blockheaders, height: %d (~%.2f%%)\n", height, progress);
+    }
+}
+
 /** Store block on disk. If dbp is non-nullptr, the file is known to already reside on disk */
-bool CChainState::AcceptBlock(const std::shared_ptr<const CBlock>& pblock, BlockValidationState& state, CBlockIndex** ppindex, bool fRequested, const FlatFilePos* dbp, bool* fNewBlock)
+bool CChainState::AcceptBlock(const std::shared_ptr<const CBlock>& pblock, BlockValidationState& state, CBlockIndex** ppindex, bool fRequested, const FlatFilePos* dbp, bool* fNewBlock, bool min_pow_checked)
 {
     const CBlock& block = *pblock;
 
@@ -3701,7 +3747,7 @@ bool CChainState::AcceptBlock(const std::shared_ptr<const CBlock>& pblock, Block
     CBlockIndex *pindexDummy = nullptr;
     CBlockIndex *&pindex = ppindex ? *ppindex : pindexDummy;
 
-    bool accepted_header{m_chainman.AcceptBlockHeader(block, state, &pindex)};
+    bool accepted_header{m_chainman.AcceptBlockHeader(block, state, &pindex, min_pow_checked)};
     CheckBlockIndex();
 
     if (!accepted_header)
@@ -3774,7 +3820,7 @@ bool CChainState::AcceptBlock(const std::shared_ptr<const CBlock>& pblock, Block
     return true;
 }
 
-bool ChainstateManager::ProcessNewBlock(const std::shared_ptr<const CBlock>& block, bool force_processing, bool* new_block)
+bool ChainstateManager::ProcessNewBlock(const std::shared_ptr<const CBlock>& block, bool force_processing, bool min_pow_checked, bool* new_block)
 {
     AssertLockNotHeld(cs_main);
 
@@ -3795,7 +3841,7 @@ bool ChainstateManager::ProcessNewBlock(const std::shared_ptr<const CBlock>& blo
         bool ret = CheckBlock(*block, state, GetConsensus());
         if (ret) {
             // Store to disk
-            ret = ActiveChainstate().AcceptBlock(block, state, &pindex, force_processing, nullptr, new_block);
+            ret = ActiveChainstate().AcceptBlock(block, state, &pindex, force_processing, nullptr, new_block, min_pow_checked);
         }
         if (!ret) {
             GetMainSignals().BlockChecked(*block, state);
@@ -4332,7 +4378,7 @@ void CChainState::LoadExternalBlockFile(
                     const CBlockIndex* pindex = m_blockman.LookupBlockIndex(hash);
                     if (!pindex || (pindex->nStatus & BLOCK_HAVE_DATA) == 0) {
                       BlockValidationState state;
-                      if (AcceptBlock(pblock, state, nullptr, true, dbp, nullptr)) {
+                      if (AcceptBlock(pblock, state, nullptr, true, dbp, nullptr, true)) {
                           nLoaded++;
                       }
                       if (state.IsError()) {
@@ -4370,7 +4416,7 @@ void CChainState::LoadExternalBlockFile(
                                     head.ToString());
                             LOCK(cs_main);
                             BlockValidationState dummy;
-                            if (AcceptBlock(pblockrecursive, dummy, nullptr, true, &it->second, nullptr)) {
+                            if (AcceptBlock(pblockrecursive, dummy, nullptr, true, &it->second, nullptr, true)) {
                                 nLoaded++;
                                 queue.push_back(pblockrecursive->GetHash());
                             }