From 10a24bb1a2ed50ed2d5e542c829c9eb827838ad2 Mon Sep 17 00:00:00 2001
From: Kevin Heifner <heifnerk@objectcomputing.com>
Date: Mon, 10 Feb 2025 08:38:53 -0600
Subject: [PATCH] Do not allow replay-blockchain without snapshot unless a full
 block log is available.

---
 libraries/chain/block_log.cpp                 | 25 +++++++++++++++----
 .../chain/include/eosio/chain/block_log.hpp   |  3 +++
 plugins/chain_plugin/chain_plugin.cpp         |  5 ++++
 3 files changed, 28 insertions(+), 5 deletions(-)

diff --git a/libraries/chain/block_log.cpp b/libraries/chain/block_log.cpp
index 946e4764b8..c7112f334d 100644
--- a/libraries/chain/block_log.cpp
+++ b/libraries/chain/block_log.cpp
@@ -510,6 +510,9 @@ namespace eosio { namespace chain {
             else
                head = {};
          }
+
+         static block_log_preamble extract_block_log_preamble(const std::filesystem::path& block_dir,
+                                                              const std::filesystem::path& retained_dir);
       }; // block_log_impl
 
       /// Would remove pre-existing block log and index, never write blocks into disk.
@@ -1459,8 +1462,8 @@ namespace eosio { namespace chain {
    }
 
    // static
-   std::optional<block_log::chain_context> block_log::extract_chain_context(const std::filesystem::path& block_dir,
-                                                                            const std::filesystem::path& retained_dir) {
+   block_log_preamble detail::block_log_impl::extract_block_log_preamble(const std::filesystem::path& block_dir,
+                                                                         const std::filesystem::path& retained_dir) {
       std::filesystem::path first_block_file;
       if (!retained_dir.empty() && std::filesystem::exists(retained_dir)) {
          for_each_file_in_dir_matches(retained_dir, R"(blocks-1-\d+\.log)",
@@ -1474,9 +1477,9 @@ namespace eosio { namespace chain {
       }
 
       if (!first_block_file.empty()) {
-         return block_log_data(first_block_file).get_preamble().chain_context;
+         return block_log_data(first_block_file).get_preamble();
       }
-      
+
       if (!retained_dir.empty() && std::filesystem::exists(retained_dir)) {
          const std::regex        my_filter(R"(blocks-\d+-\d+\.log)");
          std::smatch             what;
@@ -1489,12 +1492,18 @@ namespace eosio { namespace chain {
             std::string file = p->path().filename().string();
             if (!std::regex_match(file, what, my_filter))
                continue;
-            return block_log_data(p->path()).chain_id();
+            return block_log_data(p->path()).get_preamble();
          }
       }
       return {};
    }
 
+   // static
+   std::optional<block_log::chain_context> block_log::extract_chain_context(const std::filesystem::path& block_dir,
+                                                                            const std::filesystem::path& retained_dir) {
+      return detail::block_log_impl::extract_block_log_preamble(block_dir, retained_dir).chain_context;
+   }
+
    // static
    std::optional<genesis_state> block_log::extract_genesis_state(const std::filesystem::path& block_dir,
                                                                  const std::filesystem::path& retained_dir) {
@@ -1516,6 +1525,12 @@ namespace eosio { namespace chain {
           } , *context);
    }
 
+   // static
+   uint32_t block_log::extract_first_block_num(const std::filesystem::path& block_dir,
+                                               const std::filesystem::path& retained_dir) {
+      return detail::block_log_impl::extract_block_log_preamble(block_dir, retained_dir).first_block_num;
+   }
+
    // static
    bool block_log::contains_genesis_state(uint32_t version, uint32_t first_block_num) {
       return version < genesis_state_or_chain_id_version || first_block_num == 1;
diff --git a/libraries/chain/include/eosio/chain/block_log.hpp b/libraries/chain/include/eosio/chain/block_log.hpp
index e933cb7920..5bd6196027 100644
--- a/libraries/chain/include/eosio/chain/block_log.hpp
+++ b/libraries/chain/include/eosio/chain/block_log.hpp
@@ -95,6 +95,9 @@ namespace eosio { namespace chain {
          extract_chain_id(const std::filesystem::path& data_dir,
                           const std::filesystem::path& retained_dir = std::filesystem::path{});
 
+         static uint32_t extract_first_block_num(const std::filesystem::path& block_dir,
+                                                 const std::filesystem::path& retained_dir = std::filesystem::path{});
+
          static void construct_index(const std::filesystem::path& block_file_name, const std::filesystem::path& index_file_name);
 
          static bool contains_genesis_state(uint32_t version, uint32_t first_block_num);
diff --git a/plugins/chain_plugin/chain_plugin.cpp b/plugins/chain_plugin/chain_plugin.cpp
index b1c380a2b9..e6143ff266 100644
--- a/plugins/chain_plugin/chain_plugin.cpp
+++ b/plugins/chain_plugin/chain_plugin.cpp
@@ -778,6 +778,11 @@ void chain_plugin_impl::plugin_initialize(const variables_map& options) {
          ilog( "Replay requested: deleting state database" );
          if( options.at( "truncate-at-block" ).as<uint32_t>() > 0 )
             wlog( "The --truncate-at-block option does not work for a regular replay of the blockchain." );
+         if (!options.count( "snapshot" )) {
+            auto first_block = block_log::extract_first_block_num(blocks_dir, retained_dir);
+            EOS_ASSERT(first_block == 1, plugin_config_exception,
+                       "replay-blockchain without snapshot requested without a full block log, first block: ${n}", ("n", first_block));
+         }
          clear_directory_contents( chain_config->state_dir );
       } else if( options.at( "truncate-at-block" ).as<uint32_t>() > 0 ) {
          wlog( "The --truncate-at-block option can only be used with --hard-replay-blockchain." );