Fixed crash caused by unloading NScurl.dll after curl_global_init(..)…

… and curl_global_cleanup(..) get called.

Once curl gets initialized NScurl.dll will be pinned in memory until the process exits.

curl.c

@@ -9,6 +9,7 @@
 
 
 typedef struct {
+	volatile HMODULE		hPinnedModule;
 	CRITICAL_SECTION		csLock;
 	CHAR					szVersion[64];
 	CHAR					szUserAgent[128];
@@ -185,7 +186,6 @@ ULONG CurlInitialize()
 		_snprintf( g_Curl.szUserAgent, ARRAYSIZE( g_Curl.szUserAgent ), "nscurl/%s", g_Curl.szVersion );
 	}
 
-	curl_global_init( CURL_GLOBAL_ALL );
 	return ERROR_SUCCESS;
 }
 
@@ -196,7 +196,41 @@ void CurlDestroy()
 	TRACE( _T( "%hs()\n" ), __FUNCTION__ );
 
 	DeleteCriticalSection( &g_Curl.csLock );
-	curl_global_cleanup();
+}
+
+
+//++ CurlInitializeLibcurl
+ULONG CurlInitializeLibcurl()
+{
+	if (InterlockedCompareExchangePointer( &g_Curl.hPinnedModule, NULL, NULL ) == NULL) {
+
+		TCHAR szPath[MAX_PATH];
+		TRACE( _T( "%hs()\n" ), __FUNCTION__ );
+
+		// Initialize libcurl
+		curl_global_init( CURL_GLOBAL_ALL );
+
+		//! CAUTION:
+		//? https://curl.haxx.se/libcurl/c/curl_global_cleanup.html
+		//? curl_global_cleanup does not block waiting for any libcurl-created threads
+		//? to terminate (such as threads used for name resolving). If a module containing libcurl
+		//? is dynamically unloaded while libcurl-created threads are still running then your program
+		//? may crash or other corruption may occur. We recommend you do not run libcurl from any module
+		//? that may be unloaded dynamically. This behavior may be addressed in the future.
+
+		// It's confirmed that NScurl.dll crashes when unloaded after curl_global_cleanup() gets called
+		// Easily reproducible in XP and Vista
+		//! We'll pin it in memory forever and never call curl_global_cleanup()
+		if (GetModuleFileName( g_hInst, szPath, ARRAYSIZE( szPath ) ) > 0) {
+			g_Curl.hPinnedModule = LoadLibrary( szPath );
+			assert( g_Curl.hPinnedModule );
+		}
+
+		// kernel32!GetModuleHandleEx is available in XP+
+		//x	GetModuleHandleEx( GET_MODULE_HANDLE_EX_FLAG_PIN | GET_MODULE_HANDLE_EX_FLAG_FROM_ADDRESS, (LPCTSTR)__FUNCTION__, (HMODULE*)&g_Curl.hPinnedModule );
+	}
+
+	return ERROR_SUCCESS;
 }
 
 

curl.h

@@ -148,6 +148,9 @@ ULONG  CurlRequestErrorCode( _In_ PCURL_REQUEST pReq );		//? e.g. 404
 //+ Initialization
 ULONG CurlInitialize();
 void  CurlDestroy();
+
+ULONG CurlInitializeLibcurl();	//! Must be called only when starting transfers. This will lock NScurl.dll in memory until the process exists
+
 ULONG CurlExtractCacert();		/// Called automatically
 
 //+ CurlParseRequestParam

main.c

@@ -235,9 +235,13 @@ void __cdecl http( HWND parent, int string_size, TCHAR *variables, stack_t **sta
 
 	TRACE( _T( "%s!%hs\n" ), PLUGINNAME, __FUNCTION__ );
 
-	// Lock the plugin in memory
+	// Lock the plugin in memory (against NSIS framework trying to unload it)
 	extra->RegisterPluginCallback( g_hInst, UnloadCallback );
 
+	// Lock the plugin in memory (against Windows itself trying to FreeLibrary it)
+	// Once curl_global_init gets called, the current module must never unload
+	CurlInitializeLibcurl();
+
 	// Working structures
 	psz = (LPTSTR)MyAlloc( string_size * sizeof(TCHAR) );
 	pReq = (PCURL_REQUEST)MyAlloc( sizeof( *pReq ) );

resource.rc

@@ -51,7 +51,7 @@ END
 //
 
 VS_VERSION_INFO VERSIONINFO
- FILEVERSION 1,2020,6,6
+ FILEVERSION 1,2020,6,21
  PRODUCTVERSION 1,0,0,0
  FILEFLAGSMASK 0x3fL
 #ifdef _DEBUG
@@ -69,7 +69,7 @@ BEGIN
         BEGIN
             VALUE "CompanyName", "Marius Negrutiu ([email protected])"
             VALUE "FileDescription", "NSIS libcurl plugin"
-            VALUE "FileVersion", "1.2020.6.6"
+            VALUE "FileVersion", "1.2020.6.21"
             VALUE "InternalName", "NScurl.dll"
             VALUE "LegalCopyright", "(C)2019-present, Marius Negrutiu. All rights reserved."
             VALUE "LegalTrademarks", "https://github.com/negrutiu/nsis-nscurl"