From 00487f1de65922d2bcb1c7ac83898023ef2a1312 Mon Sep 17 00:00:00 2001
From: Vinnie Falco <vinnie.falco@gmail.com>
Date: Thu, 28 Feb 2019 10:27:43 -0800
Subject: [PATCH] Reusing an HTTP parser returns an error

---
 CHANGELOG.md                            |  1 +
 doc/qbk/release_notes.qbk               |  2 ++
 include/boost/beast/http/error.hpp      | 11 +++++++++-
 include/boost/beast/http/impl/error.ipp |  1 +
 include/boost/beast/http/parser.hpp     | 29 +++++++++++++++++++++++++
 test/beast/http/error.cpp               |  2 ++
 6 files changed, 45 insertions(+), 1 deletion(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 9a406048..54d0ab1a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,7 @@ Version 224:
 
 * Remove extraneous error check in advanced-server-flex
 * Advanced servers use HTTP parser interfaces for reading
+* Reusing an HTTP parser returns an error
 
 --------------------------------------------------------------------------------
 
diff --git a/doc/qbk/release_notes.qbk b/doc/qbk/release_notes.qbk
index 864fc169..8a9d67c9 100644
--- a/doc/qbk/release_notes.qbk
+++ b/doc/qbk/release_notes.qbk
@@ -353,6 +353,8 @@
 
 * ([issue 1460]) Large WebSocket Upgrade response no longer overflows
 
+* Reusing an HTTP parser returns an error
+
 * Handler bind wrappers use the associated allocator
 
 * `buffers_cat`
diff --git a/include/boost/beast/http/error.hpp b/include/boost/beast/http/error.hpp
index 8dc59053..1f4dfea2 100644
--- a/include/boost/beast/http/error.hpp
+++ b/include/boost/beast/http/error.hpp
@@ -144,7 +144,16 @@ enum class error
     bad_chunk_extension,
 
     /// An obs-fold exceeded an internal limit.
-    bad_obs_fold
+    bad_obs_fold,
+
+    /** The parser is stale.
+
+        This happens when attempting to re-use a parser that has
+        already completed parsing a message. Programs must construct
+        a new parser for each message. This can be easily done by
+        storing the parser in an boost or std::optional container.
+    */
+    stale_parser
 };
 
 } // http
diff --git a/include/boost/beast/http/impl/error.ipp b/include/boost/beast/http/impl/error.ipp
index bf15c690..e0167b30 100644
--- a/include/boost/beast/http/impl/error.ipp
+++ b/include/boost/beast/http/impl/error.ipp
@@ -55,6 +55,7 @@ public:
         case error::bad_chunk: return "bad chunk";
         case error::bad_chunk_extension: return "bad chunk extension";
         case error::bad_obs_fold: return "bad obs-fold";
+        case error::stale_parser: return "stale parser";
 
         default:
             return "beast.http error";
diff --git a/include/boost/beast/http/parser.hpp b/include/boost/beast/http/parser.hpp
index 854d93bb..7a4e83e7 100644
--- a/include/boost/beast/http/parser.hpp
+++ b/include/boost/beast/http/parser.hpp
@@ -61,6 +61,7 @@ class parser
     message<isRequest, Body, basic_fields<Allocator>> m_;
     typename Body::reader rd_;
     bool rd_inited_ = false;
+    bool used_ = false;
 
     std::function<void(
         std::uint64_t,
@@ -335,6 +336,20 @@ private:
         error_code& ec,
         std::true_type)
     {
+        // If this assert goes off, it means you tried to re-use a
+        // parser after it was done reading a message. This is not
+        // allowed, you need to create a new parser for each message.
+        // The easiest way to do that is to store the parser in
+        // an optional object.
+
+        BOOST_ASSERT(! used_);
+        if(used_)
+        {
+            ec = error::stale_parser;
+            return;
+        }
+        used_ = true;
+
         try
         {
             m_.target(target);
@@ -378,6 +393,20 @@ private:
         error_code& ec,
         std::true_type)
     {
+        // If this assert goes off, it means you tried to re-use a
+        // parser after it was done reading a message. This is not
+        // allowed, you need to create a new parser for each message.
+        // The easiest way to do that is to store the parser in
+        // an optional object.
+
+        BOOST_ASSERT(! used_);
+        if(used_)
+        {
+            ec = error::stale_parser;
+            return;
+        }
+        used_ = true;
+
         m_.result(code);
         m_.version(version);
         try
diff --git a/test/beast/http/error.cpp b/test/beast/http/error.cpp
index ed71bb63..37d4784d 100644
--- a/test/beast/http/error.cpp
+++ b/test/beast/http/error.cpp
@@ -65,6 +65,8 @@ public:
         check("beast.http", error::bad_chunk);
         check("beast.http", error::bad_chunk_extension);
         check("beast.http", error::bad_obs_fold);
+
+        check("beast.http", error::stale_parser);
     }
 };