diff -up firefox-45.0.1/extensions/pref/autoconfig/src/nsReadConfig.cpp.1170092 firefox-45.0.1/extensions/pref/autoconfig/src/nsReadConfig.cpp

--- firefox-45.0.1/extensions/pref/autoconfig/src/nsReadConfig.cpp.1170092	2016-03-15 23:37:54.000000000 +0100

+++ firefox-45.0.1/extensions/pref/autoconfig/src/nsReadConfig.cpp	2016-03-21 16:10:42.540417899 +0100

@@ -245,8 +245,20 @@ nsresult nsReadConfig::openAndEvaluateJS

             return rv;

         rv = NS_NewLocalFileInputStream(getter_AddRefs(inStr), jsFile);

-        if (NS_FAILED(rv)) 

-            return rv;

+        if (NS_FAILED(rv)) {

+          // Look for cfg file in /etc/<application>/pref

+          rv = NS_GetSpecialDirectory(NS_APP_PREFS_SYSTEM_CONFIG_DIR,

+                                      getter_AddRefs(jsFile));

+          NS_ENSURE_SUCCESS(rv, rv);

+

+          rv = jsFile->AppendNative(NS_LITERAL_CSTRING("pref"));

+          NS_ENSURE_SUCCESS(rv, rv);

+          rv = jsFile->AppendNative(nsDependentCString(aFileName));

+          NS_ENSURE_SUCCESS(rv, rv);

+

+          rv = NS_NewLocalFileInputStream(getter_AddRefs(inStr), jsFile);

+          NS_ENSURE_SUCCESS(rv, rv);

+        }

     } else {

         nsAutoCString location("resource://gre/defaults/autoconfig/");

diff -up firefox-45.0.1/modules/libpref/Preferences.cpp.1170092 firefox-45.0.1/modules/libpref/Preferences.cpp

--- firefox-45.0.1/modules/libpref/Preferences.cpp.1170092	2016-03-21 16:10:42.540417899 +0100

+++ firefox-45.0.1/modules/libpref/Preferences.cpp	2016-03-21 16:13:29.145888710 +0100

@@ -1214,6 +1214,8 @@ static nsresult pref_InitInitialObjects(

   // - jar:$gre/omni.jar!/defaults/preferences/*.js

   // Thus, in omni.jar case, we always load app-specific default preferences

   // from omni.jar, whether or not $app == $gre.

+  // At very end load configuration from system config location:

+  // - /etc/firefox/pref/*.js

   nsZipFind *findPtr;

   nsAutoPtr<nsZipFind> find;

diff -up firefox-45.0.1/toolkit/xre/nsXREDirProvider.cpp.1170092 firefox-45.0.1/toolkit/xre/nsXREDirProvider.cpp

--- firefox-45.0.1/toolkit/xre/nsXREDirProvider.cpp.1170092	2016-03-15 23:37:46.000000000 +0100

+++ firefox-45.0.1/toolkit/xre/nsXREDirProvider.cpp	2016-03-21 16:12:06.498655156 +0100

@@ -51,6 +51,7 @@

 #endif

 #ifdef XP_UNIX

 #include <ctype.h>

+#include "nsIXULAppInfo.h"

 #endif

 #ifdef XP_IOS

 #include "UIKitDirProvider.h"

@@ -457,6 +458,20 @@ nsXREDirProvider::GetFile(const char* aP

       }

     }

   }

+#if defined(XP_UNIX)

+  if (!strcmp(aProperty, NS_APP_PREFS_SYSTEM_CONFIG_DIR)) {

+    nsCString sysConfigDir = NS_LITERAL_CSTRING("/etc/");

+    nsCOMPtr<nsIXULAppInfo> appInfo = do_GetService("@mozilla.org/xre/app-info;1");

+    if (!appInfo)

+      return NS_ERROR_NOT_AVAILABLE;

+    nsCString appName;

+    appInfo->GetName(appName);

+    ToLowerCase(appName);

+    sysConfigDir.Append(appName);

+    return NS_NewNativeLocalFile(sysConfigDir, false, aFile);

+  }

+#endif

+

   if (NS_FAILED(rv) || !file)

     return NS_ERROR_FAILURE;

@@ -753,6 +768,14 @@ nsXREDirProvider::GetFilesInternal(const

     LoadDirIntoArray(mXULAppDir, kAppendPrefDir, directories);

     LoadDirsIntoArray(mAppBundleDirectories,

                       kAppendPrefDir, directories);

+    // Add /etc/<application>/pref/ directory if it exists

+    nsCOMPtr<nsIFile> systemPrefDir;

+    rv = NS_GetSpecialDirectory(NS_APP_PREFS_SYSTEM_CONFIG_DIR, getter_AddRefs(systemPrefDir));

+    if (NS_SUCCEEDED(rv)) {

+      rv = systemPrefDir->AppendNative(NS_LITERAL_CSTRING("pref"));

+      if (NS_SUCCEEDED(rv))

+        directories.AppendObject(systemPrefDir);

+    }

     rv = NS_NewArrayEnumerator(aResult, directories);

   }

diff -up firefox-45.0.1/xpcom/io/nsAppDirectoryServiceDefs.h.1170092 firefox-45.0.1/xpcom/io/nsAppDirectoryServiceDefs.h

--- firefox-45.0.1/xpcom/io/nsAppDirectoryServiceDefs.h.1170092	2016-03-15 23:37:47.000000000 +0100

+++ firefox-45.0.1/xpcom/io/nsAppDirectoryServiceDefs.h	2016-03-21 16:10:42.541417902 +0100

@@ -67,6 +67,7 @@

 #define NS_APP_PREFS_DEFAULTS_DIR_LIST          "PrefDL"

 #define NS_EXT_PREFS_DEFAULTS_DIR_LIST          "ExtPrefDL"

 #define NS_APP_PREFS_OVERRIDE_DIR               "PrefDOverride" // Directory for per-profile defaults

+#define NS_APP_PREFS_SYSTEM_CONFIG_DIR          "PrefSysConf"   // Directory with system-wide configuration

 #define NS_APP_USER_PROFILE_50_DIR              "ProfD"

 #define NS_APP_USER_PROFILE_LOCAL_50_DIR        "ProfLD"