Bug 1494436 - Unset MOZ_APP_LAUNCHER for external MIME handlers

If Thunderbird sets this in its startup script (as it does in Debian
and Fedora), Firefox does not set this in its startup script (it doesn't
in Debian), and Firefox is the handler for clicking a link in
Thunderbird, then Firefox will think it is part of Thunderbird and offer
to make Thunderbird (not Firefox!) the default browser. If the user
accepts this, it will break the ability to open normal HTTP links and
HTML files from other applications.

The same would be true for any other pair of Mozilla-based applications.
To avoid this, unset MOZ_APP_LAUNCHER for the Firefox child process.

Bug: https://bugzilla.mozilla.org/show_bug.cgi?id=1494436
Bug-Debian: https://bugs.debian.org/948691

Gbp-Pq: Topic fixes
Gbp-Pq: Name Bug-1494436-Unset-MOZ_APP_LAUNCHER-for-external-MIME-hand.patch

diff --git a/toolkit/system/gnome/nsGIOService.cpp b/toolkit/system/gnome/nsGIOService.cpp
index 3f0a53bc5118d0b5183d08ae21a005056741a76b..93b695fa47eee812d9922a3197c3d74cf115117a 100644 (file)
--- a/toolkit/system/gnome/nsGIOService.cpp
+++ b/toolkit/system/gnome/nsGIOService.cpp
@@ -23,6 +23,17 @@
 
 using namespace mozilla;
 
+static GAppLaunchContext* GetAppLaunchContext() {
+  GAppLaunchContext* context = g_app_launch_context_new();
+  // Unset this before launching third-party MIME handlers. Otherwise,
+  // if Thunderbird sets this in its startup script (as it does in Debian
+  // and Fedora), and Firefox does not set this in its startup script
+  // (it doesn't in Debian), then Firefox will think it is part of
+  // Thunderbird and try to make Thunderbird the default browser.
+  g_app_launch_context_unsetenv(context, "MOZ_APP_LAUNCHER");
+  return context;
+}
+
 // s. a. the code gtk_should_use_portal() uses to detect if in flatpak env
 // https://gitlab.gnome.org/GNOME/gtk/-/blob/4300a5c609306ce77cbc8a3580c19201dccd8d13/gdk/gdk.c#L472
 static bool GetFlatpakPortalEnv() {
@@ -240,7 +251,9 @@ nsGIOMimeApp::LaunchWithURI(nsIURI* aUri,
   uris.data = const_cast<char*>(spec.get());
 
   GError* error = nullptr;
-  gboolean result = g_app_info_launch_uris(mApp, &uris, nullptr, &error);
+  GAppLaunchContext* context = GetAppLaunchContext();
+  gboolean result = g_app_info_launch_uris(mApp, &uris, context, &error);
+  g_object_unref(context);
 
   if (!result) {
     g_warning("Cannot launch application: %s", error->message);
@@ -546,7 +559,10 @@ nsGIOService::ShowURI(nsIURI* aURI) {
   nsresult rv = aURI->GetSpec(spec);
   NS_ENSURE_SUCCESS(rv, rv);
   GError* error = nullptr;
-  if (!g_app_info_launch_default_for_uri(spec.get(), nullptr, &error)) {
+  GAppLaunchContext* context = GetAppLaunchContext();
+  g_app_info_launch_default_for_uri(spec.get(), context, &error);
+  g_object_unref(context);
+  if (error) {
     g_warning("Could not launch default application for URI: %s",
               error->message);
     g_error_free(error);
@@ -562,7 +578,9 @@ nsGIOService::ShowURIForInput(const nsACString& aUri) {
   nsresult rv = NS_ERROR_FAILURE;
   GError* error = nullptr;
 
-  g_app_info_launch_default_for_uri(spec, nullptr, &error);
+  GAppLaunchContext* context = GetAppLaunchContext();
+  g_app_info_launch_default_for_uri(spec, context, &error);
+  g_object_unref(context);
   if (error) {
     g_warning("Cannot launch default application: %s", error->message);
     g_error_free(error);