From b028e88fede97f349df48fbf6a936818104aeaf1 Mon Sep 17 00:00:00 2001
From: Nick Bolton <nick@symless.com>
Date: Mon, 2 Oct 2017 18:13:45 +0100
Subject: [PATCH] #6162 Add UID arg so service can change process user

---
 src/lib/core/App.cpp       | 26 +++++++++++++++++++++-----
 src/lib/core/ArgParser.cpp |  3 +++
 src/lib/core/ArgsBase.cpp  |  1 +
 src/lib/core/ArgsBase.h    |  1 +
 4 files changed, 26 insertions(+), 5 deletions(-)

diff --git a/src/lib/core/App.cpp b/src/lib/core/App.cpp
index 9d8771e7..06d0cd12 100644
--- a/src/lib/core/App.cpp
+++ b/src/lib/core/App.cpp
@@ -33,21 +33,22 @@
 #include "ipc/Ipc.h"
 #include "base/EventQueue.h"
 
+#include <iostream>
+#include <stdio.h>
+
 #if SYSAPI_WIN32
 #include "arch/win32/ArchMiscWindows.h"
 #include "base/IEventQueue.h"
 #include "base/TMethodJob.h"
 #endif
 
-#include <iostream>
-#include <stdio.h>
-
 #if WINAPI_CARBON
 #include <ApplicationServices/ApplicationServices.h>
+#include "platform/OSXDragSimulator.h"
 #endif
 
-#if defined(__APPLE__)
-#include "platform/OSXDragSimulator.h"
+#if WINAPI_XWINDOWS
+#include <unistd.h>
 #endif
 
 App* App::s_instance = nullptr;
@@ -172,6 +173,21 @@ App::initApp(int argc, const char** argv)
 {
     // parse command line
     parseArgs(argc, argv);
+
+#if WINAPI_XWINDOWS
+    // for use on linux, tell the core process what user id it should run as.
+    // this is a simple way to allow the core process to talk to X. this avoids
+    // the "WARNING: primary screen unavailable: unable to open screen" error.
+    // a better way would be to use xauth cookie and dbus to get access to X.
+    if (!argsBase().m_runAsUid != -1) {
+        if (setuid(argsBase().m_runAsUid) == 0) {
+            LOG((CLOG_DEBUG "process uid was set to: %d", argsBase().m_runAsUid));
+        }
+        else {
+            LOG((CLOG_WARN "failed to set process uid to: %d", argsBase().m_runAsUid));
+        }
+    }
+#endif
     
     ARCH->setProfileDirectory(argsBase().m_profileDirectory);
     ARCH->setPluginDirectory(argsBase().m_pluginDirectory);
diff --git a/src/lib/core/ArgParser.cpp b/src/lib/core/ArgParser.cpp
index 531554ad..284de5b3 100644
--- a/src/lib/core/ArgParser.cpp
+++ b/src/lib/core/ArgParser.cpp
@@ -299,6 +299,9 @@ ArgParser::parseGenericArgs(int argc, const char* const* argv, int& i)
     else if (isArg(i, argc, argv, NULL, "--plugin-dir", 1)) {
         argsBase().m_pluginDirectory = argv[++i];
     }
+    else if (isArg(i, argc, argv, NULL, "--run-as-uid", 1)) {
+        argsBase().m_runAsUid = std::stoi(argv[++i]);
+    }
     else {
         // option not supported here
         return false;
diff --git a/src/lib/core/ArgsBase.cpp b/src/lib/core/ArgsBase.cpp
index 4e9c449c..b78a2e06 100644
--- a/src/lib/core/ArgsBase.cpp
+++ b/src/lib/core/ArgsBase.cpp
@@ -29,6 +29,7 @@ m_daemon(true), // backward compatibility for unix (daemon by default)
 #endif
 #if WINAPI_XWINDOWS
 m_disableXInitThreads(false),
+m_runAsUid(-1),
 #endif
 m_backend(false),
 m_restartable(true),
diff --git a/src/lib/core/ArgsBase.h b/src/lib/core/ArgsBase.h
index 9ce6e98c..41e94157 100644
--- a/src/lib/core/ArgsBase.h
+++ b/src/lib/core/ArgsBase.h
@@ -44,6 +44,7 @@ public:
 #endif
 #if WINAPI_XWINDOWS
     bool                m_disableXInitThreads;
+    int                 m_runAsUid;
 #endif
     bool                m_shouldExit;
     String                m_synergyAddress;