From ad66ca1e475d2546dbbda206465307613108a15d Mon Sep 17 00:00:00 2001
From: Martin Zumsande <mzumsande@gmail.com>
Date: Fri, 2 Jun 2023 16:36:01 -0400
Subject: [PATCH 1/2] init: abort loading of blockindex in case of missing
 height.

If a height is missing we are facing a non-contiguous block index db, and could previously
hit an assert in GetAncestor() called from BuildSkip() instead of returning an error.
---
 src/node/blockstorage.cpp | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/src/node/blockstorage.cpp b/src/node/blockstorage.cpp
index 78416ec5765..a292ffe8698 100644
--- a/src/node/blockstorage.cpp
+++ b/src/node/blockstorage.cpp
@@ -259,8 +259,13 @@ bool BlockManager::LoadBlockIndex()
     std::sort(vSortedByHeight.begin(), vSortedByHeight.end(),
               CBlockIndexHeightOnlyComparator());
 
+    CBlockIndex* previous_index{nullptr};
     for (CBlockIndex* pindex : vSortedByHeight) {
         if (m_interrupt) return false;
+        if (previous_index && pindex->nHeight > previous_index->nHeight + 1) {
+            return error("%s: block index is non-contiguous, index of height %d missing", __func__, previous_index->nHeight + 1);
+        }
+        previous_index = pindex;
         pindex->nChainWork = (pindex->pprev ? pindex->pprev->nChainWork : 0) + GetBlockProof(*pindex);
         pindex->nTimeMax = (pindex->pprev ? std::max(pindex->pprev->nTimeMax, pindex->nTime) : pindex->nTime);
 

From d27b9a2248476439ddab7700327f074005a810d5 Mon Sep 17 00:00:00 2001
From: Martin Zumsande <mzumsande@gmail.com>
Date: Fri, 2 Jun 2023 13:45:02 -0400
Subject: [PATCH 2/2] test: fix feature_init.py file perturbation

Simultaneously opening the file in read and write mode would
lead to opening of an empty file instead of perturbing the existing
file.
Also, revert to the previous state after each perturbation so that
each perturbation is applied in isolation.
---
 test/functional/feature_init.py | 24 +++++++++++++++++++-----
 1 file changed, 19 insertions(+), 5 deletions(-)

diff --git a/test/functional/feature_init.py b/test/functional/feature_init.py
index 64ca312b842..94f5116f9b0 100755
--- a/test/functional/feature_init.py
+++ b/test/functional/feature_init.py
@@ -5,6 +5,7 @@
 """Stress tests related to node initialization."""
 import os
 from pathlib import Path
+import shutil
 
 from test_framework.test_framework import BitcoinTestFramework, SkipTest
 from test_framework.test_node import ErrorMatch
@@ -47,7 +48,7 @@ class InitStressTest(BitcoinTestFramework):
 
         def start_expecting_error(err_fragment):
             node.assert_start_raises_init_error(
-                extra_args=['-txindex=1', '-blockfilterindex=1', '-coinstatsindex=1'],
+                extra_args=['-txindex=1', '-blockfilterindex=1', '-coinstatsindex=1', '-checkblocks=200', '-checklevel=4'],
                 expected_msg=err_fragment,
                 match=ErrorMatch.PARTIAL_REGEX,
             )
@@ -101,9 +102,9 @@ class InitStressTest(BitcoinTestFramework):
         }
 
         files_to_perturb = {
-            'blocks/index/*.ldb': 'Error opening block database.',
+            'blocks/index/*.ldb': 'Error loading block database.',
             'chainstate/*.ldb': 'Error opening block database.',
-            'blocks/blk*.dat': 'Error opening block database.',
+            'blocks/blk*.dat': 'Corrupted block database detected.',
         }
 
         for file_patt, err_fragment in files_to_delete.items():
@@ -124,18 +125,31 @@ class InitStressTest(BitcoinTestFramework):
             check_clean_start()
             self.stop_node(0)
 
+        self.log.info("Test startup errors after perturbing certain essential files")
         for file_patt, err_fragment in files_to_perturb.items():
+            shutil.copytree(node.chain_path / "blocks", node.chain_path / "blocks_bak")
+            shutil.copytree(node.chain_path / "chainstate", node.chain_path / "chainstate_bak")
             target_files = list(node.chain_path.glob(file_patt))
 
             for target_file in target_files:
                 self.log.info(f"Perturbing file to ensure failure {target_file}")
-                with open(target_file, "rb") as tf_read, open(target_file, "wb") as tf_write:
+                with open(target_file, "rb") as tf_read:
                     contents = tf_read.read()
                     tweaked_contents = bytearray(contents)
-                    tweaked_contents[50:250] = b'1' * 200
+                    # Since the genesis block is not checked by -checkblocks, the
+                    # perturbation window must be chosen such that a higher block
+                    # in blk*.dat is affected.
+                    tweaked_contents[150:350] = b'1' * 200
+                with open(target_file, "wb") as tf_write:
                     tf_write.write(bytes(tweaked_contents))
 
             start_expecting_error(err_fragment)
 
+            shutil.rmtree(node.chain_path / "blocks")
+            shutil.rmtree(node.chain_path / "chainstate")
+            shutil.move(node.chain_path / "blocks_bak", node.chain_path / "blocks")
+            shutil.move(node.chain_path / "chainstate_bak", node.chain_path / "chainstate")
+
+
 if __name__ == '__main__':
     InitStressTest().main()