From 3e6cf593845bc8a25450efbe73221873677ea0f7 Mon Sep 17 00:00:00 2001
From: Daniel Frey <d.frey@gmx.de>
Date: Thu, 2 Jan 2025 22:32:51 +0100
Subject: [PATCH] Secure pipeline ctor

---
 include/tao/pq/pipeline.hpp | 12 +++++++++++-
 src/lib/pq/pipeline.cpp     |  2 +-
 src/lib/pq/transaction.cpp  |  2 +-
 3 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/include/tao/pq/pipeline.hpp b/include/tao/pq/pipeline.hpp
index 8bc5bf5..e938b70 100644
--- a/include/tao/pq/pipeline.hpp
+++ b/include/tao/pq/pipeline.hpp
@@ -13,6 +13,7 @@
 namespace tao::pq
 {
    class connection;
+   class transaction;
 
    class pipeline
       : public transaction_base
@@ -20,8 +21,17 @@ namespace tao::pq
    private:
       std::shared_ptr< transaction_base > m_previous;
 
+      friend class transaction;
+
+      // pass-key idiom
+      class private_key final
+      {
+         private_key() = default;
+         friend class transaction;
+      };
+
    public:
-      explicit pipeline( const std::shared_ptr< pq::connection >& connection );
+      pipeline( const private_key /*unused*/, const std::shared_ptr< pq::connection >& connection );
 
       ~pipeline() override
       {
diff --git a/src/lib/pq/pipeline.cpp b/src/lib/pq/pipeline.cpp
index 3ce9669..2a1f170 100644
--- a/src/lib/pq/pipeline.cpp
+++ b/src/lib/pq/pipeline.cpp
@@ -10,7 +10,7 @@
 
 namespace tao::pq
 {
-   pipeline::pipeline( const std::shared_ptr< pq::connection >& connection )
+   pipeline::pipeline( const pipeline::private_key /*unused*/, const std::shared_ptr< pq::connection >& connection )
       : transaction_base( connection ),
         m_previous( current_transaction()->shared_from_this() )
    {
diff --git a/src/lib/pq/transaction.cpp b/src/lib/pq/transaction.cpp
index aad8d0c..e171dd9 100644
--- a/src/lib/pq/transaction.cpp
+++ b/src/lib/pq/transaction.cpp
@@ -107,7 +107,7 @@ namespace tao::pq
    auto transaction::pipeline() -> std::shared_ptr< pq::pipeline >
    {
       check_current_transaction();
-      return std::make_shared< pq::pipeline >( m_connection );
+      return std::make_shared< pq::pipeline >( pq::pipeline::private_key(), m_connection );
    }
 
    void transaction::commit()