openvpnserv: Fix writing messages to the event log

There are two problems with the current implementation:

 - due to the code bug, we never display actual error message
corresponding to the Windows error code. We use
FORMAT_MESSAGE_ALLOCATE_BUFFER, in which case we must pass
a pointer to the LPTSTR, not the LPTSTR itself.

 - The error is not displayed in the "General" tab, which is very confusing.
One needs to go to the "Details" tab to see what is wrong.

This commit solves both problems. We now display a proper error
message in addition to the text provided by the service ("what went wrong").
While on it, remove trailing symbols ín a safer way.

To display the message in "General" tab, we create a registered message file
(openvpnservmsg.dll), which contains message template. Note that this requires
changes to the installer - we need to install the new DLL and
add a registry entry.

GitHub: https://github.com/OpenVPN/openvpn/issues/842

Change-Id: I9b9f38e11b06701142bdc1339d9bedf080de5f86
Signed-off-by: Lev Stipakov <lev@openvpn.net>
Acked-by: Gert Doering <gert@greenie.muc.de>
Gerrit URL: https://gerrit.openvpn.net/c/openvpn/+/1185
Message-Id: <20250917090653.25510-1-gert@greenie.muc.de>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg33008.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>
(backported from commit 06919a60ae61d6d88546b23b52092f742599a8ae)

diff --git a/src/openvpnserv/CMakeLists.txt b/src/openvpnserv/CMakeLists.txt
index 17cd90c628f6c565d6788b016d5b14ac5ed8ff6d..201350cd71b811d13c06df26103d3802d9c51e2f 100644 (file)
--- a/src/openvpnserv/CMakeLists.txt
+++ b/src/openvpnserv/CMakeLists.txt
@@ -6,11 +6,14 @@ project(openvpnserv)
 
 add_executable(openvpnserv)
 
+set(MC_GEN_DIR ${CMAKE_CURRENT_BINARY_DIR}/mc)
+
 target_include_directories(openvpnserv PRIVATE
     ${CMAKE_CURRENT_BINARY_DIR}/../../
     ../../include/
     ../openvpn/
     ../compat/
+    ${MC_GEN_DIR}
     )
 target_sources(openvpnserv PRIVATE
     common.c
@@ -32,3 +35,34 @@ if (MINGW)
     target_compile_options(openvpnserv PRIVATE -municode)
     target_link_options(openvpnserv PRIVATE -municode)
 endif ()
+
+# below we generate a DLL which contains an event source for event log messages from eventmsg.mc template
+file(MAKE_DIRECTORY ${MC_GEN_DIR})
+set(MC_FILE ${CMAKE_CURRENT_SOURCE_DIR}/eventmsg.mc)
+
+find_program(MC_COMPILER NAMES mc mc.exe x86_64-w64-mingw32-windmc i686-w64-mingw32-windmc windmc)
+
+if (NOT MC_COMPILER)
+    message(FATAL_ERROR "No message compiler found.")
+endif()
+
+add_custom_command(
+    OUTPUT ${MC_GEN_DIR}/eventmsg.rc ${MC_GEN_DIR}/eventmsg.h
+    COMMAND ${MC_COMPILER} -U -h ${MC_GEN_DIR} -r ${MC_GEN_DIR} ${MC_FILE}
+    DEPENDS ${CMAKE_CURRENT_SOURCE_DIR}/eventmsg.mc
+    VERBATIM
+    )
+
+# generate rc file for DLL and header for the service binary
+add_custom_target(msg_mc_gen ALL DEPENDS ${MC_GEN_DIR}/eventmsg.rc ${MC_GEN_DIR}/eventmsg.h)
+
+add_library(openvpnservmsg SHARED ${MC_GEN_DIR}/eventmsg.rc)
+
+if (MSVC)
+    set_target_properties(openvpnservmsg PROPERTIES LINK_FLAGS "/NOENTRY")
+else()
+    target_link_options(openvpnservmsg PRIVATE "-Wl,--no-entry")
+endif()
+
+add_dependencies(openvpnservmsg msg_mc_gen)
+add_dependencies(openvpnserv msg_mc_gen)

diff --git a/src/openvpnserv/common.c b/src/openvpnserv/common.c
index bd0a484e271398bb1b84a6b44e03bc280f32c580..feaae1992000291ec4990446b73d59ed5d08bd54 100644 (file)
--- a/src/openvpnserv/common.c
+++ b/src/openvpnserv/common.c
@@ -23,6 +23,7 @@
 
 #include "service.h"
 #include "validate.h"
+#include "eventmsg.h"
 
 LPCTSTR service_instance = TEXT("");
 static wchar_t win_sys_path[MAX_PATH];
@@ -219,24 +220,28 @@ GetLastErrorText()
     LPTSTR tmp = NULL;
 
     error = GetLastError();
-    len = FormatMessage(FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_ARGUMENT_ARRAY,
-                        NULL, error, LANG_NEUTRAL, tmp, 0, NULL);
+    len = FormatMessageW(FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM| FORMAT_MESSAGE_IGNORE_INSERTS,
+                         NULL, error, MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT), (LPTSTR)&tmp, 0, NULL);
 
-    if (len == 0 || (long) _countof(buf) < (long) len + 14)
+    if (!len || !tmp)
     {
-        buf[0] = TEXT('\0');
-    }
-    else
-    {
-        tmp[wcslen(tmp) - 2] = TEXT('\0'); /* remove CR/LF characters */
-        openvpn_swprintf(buf, _countof(buf), TEXT("%ls (0x%x)"), tmp, error);
+        openvpn_swprintf(buf, _countof(buf), TEXT("Unknown error (0x%lx)"), error);
+        if (tmp)
+        {
+            LocalFree(tmp);
+        }
+        return buf;
     }
 
-    if (tmp)
+    /* trim trailing CR / LF / spaces safely */
+    while (len && (tmp[len - 1] == TEXT('\r') || tmp[len - 1] == TEXT('\n') || tmp[len - 1] == TEXT(' ')))
     {
-        LocalFree(tmp);
+        tmp[--len] = TEXT('\0');
     }
 
+    openvpn_swprintf(buf, _countof(buf), TEXT("%ls (0x%lx)"), tmp, error);
+
+    LocalFree(tmp);
     return buf;
 }
 
@@ -268,9 +273,15 @@ MsgToEventLog(DWORD flags, LPCTSTR format, ...)
         va_end(arglist);
 
         const TCHAR *mesg[] = { msg[0], msg[1] };
-        ReportEvent(hEventSource, flags & MSG_FLAGS_ERROR ?
-                    EVENTLOG_ERROR_TYPE : EVENTLOG_INFORMATION_TYPE,
-                    0, 0, NULL, 2, 0, mesg, NULL);
+        ReportEvent(hEventSource,
+                    flags & MSG_FLAGS_ERROR ? EVENTLOG_ERROR_TYPE : EVENTLOG_INFORMATION_TYPE,
+                    0,
+                    EVT_TEXT_2,
+                    NULL,
+                    2,
+                    0,
+                    mesg,
+                    NULL);
         DeregisterEventSource(hEventSource);
     }
 

diff --git a/src/openvpnserv/eventmsg.mc b/src/openvpnserv/eventmsg.mc
new file mode 100644 (file)
index 0000000..722a30e
--- /dev/null
+++ b/src/openvpnserv/eventmsg.mc
@@ -0,0 +1,23 @@
+MessageIdTypedef=DWORD
+
+SeverityNames=(Success=0x0:STATUS_SEVERITY_SUCCESS
+    Informational=0x1:STATUS_SEVERITY_INFORMATIONAL
+    Warning=0x2:STATUS_SEVERITY_WARNING
+    Error=0x3:STATUS_SEVERITY_ERROR
+    )
+
+FacilityNames=(System=0x0:FACILITY_SYSTEM
+    Runtime=0x2:FACILITY_RUNTIME
+    Stubs=0x3:FACILITY_STUBS
+    Io=0x4:FACILITY_IO_ERROR_CODE
+)
+
+LanguageNames=(English=0x409:MSG00409)
+
+MessageId=0x1
+Severity=Error
+Facility=Runtime
+SymbolicName=EVT_TEXT_2
+Language=English
+%1%n%2
+.