Fix error handling in SSL shutdown operations in examples

example/http/client/async-ssl/http_client_async_ssl.cpp

@@ -184,16 +184,25 @@ public:
     void
     on_shutdown(beast::error_code ec)
     {
-        if(ec == net::error::eof)
-        {
-            // Rationale:
-            // http://stackoverflow.com/questions/25587403/boost-asio-ssl-async-shutdown-always-finishes-with-an-error
-            ec = {};
-        }
-        if(ec)
-            return fail(ec, "shutdown");
+        // ssl::error::stream_truncated, also known as an SSL "short read",
+        // indicates the peer closed the connection without performing the
+        // required closing handshake (for example, Google does this to
+        // improve performance). Generally this can be a security issue,
+        // but if your communication protocol is self-terminated (as
+        // it is with both HTTP and WebSocket) then you may simply
+        // ignore the lack of close_notify.
+        //
+        // https://github.com/boostorg/beast/issues/38
+        //
+        // https://security.stackexchange.com/questions/91435/how-to-handle-a-malicious-ssl-tls-shutdown
+        //
+        // When a short read would cut off the end of an HTTP message,
+        // Beast returns the error beast::http::error::partial_message.
+        // Therefore, if we see a short read here, it has occurred
+        // after the message has been completed, so it is safe to ignore it.
 
-        // If we get here then the connection is closed gracefully
+        if(ec != net::ssl::error::stream_truncated)
+            return fail(ec, "shutdown");
     }
 };