Always clear LD_PRELOAD on host process start

Some apps might not use the same execve call to start child processes,
so clearing LD_PRELOAD there isn't actually safe.

Fixes #32.

Signed-off-by: Ryan Gonzalez <ryan.gonzalez@collabora.com>

Author: refi64

Makefile

@@ -66,6 +66,14 @@ preload_host_SOURCES := \
 
 $(call build_shlib,preload_host)
 
+preload_host_mimic_strategy_SOURCE_DIR := preload/host/mimic_strategy
+preload_host_mimic_strategy_NAME := zypak-preload-host-mimic-strategy
+preload_host_mimic_strategy_DEPS := preload base
+preload_host_mimic_strategy_SOURCES := \
+	initialize.cc \
+
+$(call build_shlib,preload_host_mimic_strategy)
+
 preload_host_spawn_strategy_SOURCE_DIR := preload/host/spawn_strategy
 preload_host_spawn_strategy_NAME := zypak-preload-host-spawn-strategy
 preload_host_spawn_strategy_DEPS := preload dbus base
@@ -140,6 +148,7 @@ install : all
 	install -Dm 755 -t $(FLATPAK_DEST)/bin build/zypak-helper
 	install -Dm 755 -t $(FLATPAK_DEST)/bin build/zypak-sandbox
 	install -Dm 755 -t $(FLATPAK_DEST)/lib build/libzypak-preload-host.so
+	install -Dm 755 -t $(FLATPAK_DEST)/lib build/libzypak-preload-host-mimic-strategy.so
 	install -Dm 755 -t $(FLATPAK_DEST)/lib build/libzypak-preload-host-spawn-strategy.so
 	install -Dm 755 -t $(FLATPAK_DEST)/lib build/libzypak-preload-child.so
 	install -Dm 755 -t $(FLATPAK_DEST)/lib build/libzypak-preload-child-mimic-strategy.so

src/helper/main.cc

@@ -124,7 +124,7 @@ std::string GetPreload(std::string_view mode, std::string_view libdir) {
   preload_names.emplace_back(mode);
   if (Env::Test(Env::kZypakZygoteStrategySpawn)) {
     preload_names.push_back(std::string(mode) + "-spawn-strategy");
-  } else if (mode == "child") {
+  } else {
     preload_names.push_back(std::string(mode) + "-mimic-strategy");
   }
 

src/preload/host/exec_zypak_sandbox.cc

@@ -55,8 +55,6 @@ DECLARE_OVERRIDE(int, execvp, const char* file, char* const* argv) {
     return -1;
   }
 
-  Env::Clear("LD_PRELOAD");
-
   if (file == SandboxPath::instance()->sandbox_path()) {
     file = "zypak-sandbox";
   } else if (auto type = GetTypeArg(argv);

src/preload/host/mimic_strategy/initialize.cc

@@ -0,0 +1,15 @@
+// Copyright 2023 Ryan Gonzalez
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "base/env.h"
+#include "preload/main_override.h"
+
+using namespace zypak;
+
+int MAIN_OVERRIDE(int argc, char** argv, char** envp) {
+  Env::Clear("LD_PRELOAD");
+  return true_main(argc, argv, envp);
+}
+
+INSTALL_MAIN_OVERRIDE()

src/preload/host/spawn_strategy/initialize.cc

@@ -10,6 +10,7 @@
 
 #include "base/base.h"
 #include "base/debug.h"
+#include "base/env.h"
 #include "base/socket.h"
 #include "dbus/bus.h"
 #include "preload/declare_override.h"
@@ -20,6 +21,8 @@ using namespace zypak;
 using namespace zypak::preload;
 
 int MAIN_OVERRIDE(int argc, char** argv, char** envp) {
+  Env::Clear("LD_PRELOAD");
+
   DebugContext::instance()->LoadFromEnvironment();
   DebugContext::instance()->set_name("preload-host-spawn-strategy");