Add option to disable 077 umask (create new files with system default umask)

The option is only effective for either wallet-less builds or if
-disablewallet is specified as well.

Rebased-By: Wladimir J. van der Laan <laanwj@gmail.com>
Rebased-From: 34d5fc0 4e1a196 bd4307b d53a33b 7e09b36
Github-Pull: #4286

src/init.cpp

@@ -224,8 +224,12 @@ std::string HelpMessage(HelpMessageMode mode)
     strUsage += "  -par=<n>               " + strprintf(_("Set the number of script verification threads (%u to %d, 0 = auto, <0 = leave that many cores free, default: %d)"), -(int)boost::thread::hardware_concurrency(), MAX_SCRIPTCHECK_THREADS, DEFAULT_SCRIPTCHECK_THREADS) + "\n";
     strUsage += "  -pid=<file>            " + _("Specify pid file (default: bitcoind.pid)") + "\n";
     strUsage += "  -reindex               " + _("Rebuild block chain index from current blk000??.dat files") + " " + _("on startup") + "\n";
+#if !defined(WIN32)
+    strUsage += "  -sysperms              " + _("Create new files with system default permissions, instead of umask 077 (only effective with disabled wallet functionality)") + "\n";
+#endif
     strUsage += "  -txindex               " + _("Maintain a full transaction index (default: 0)") + "\n";
 
+
     strUsage += "\n" + _("Connection options:") + "\n";
     strUsage += "  -addnode=<ip>          " + _("Add a node to connect to and attempt to keep the connection open") + "\n";
     strUsage += "  -banscore=<n>          " + _("Threshold for disconnecting misbehaving peers (default: 100)") + "\n";
@@ -484,7 +488,15 @@ bool AppInit2(boost::thread_group& threadGroup)
     }
 #endif
 #ifndef WIN32
-    umask(077);
+
+    if (GetBoolArg("-sysperms", false)) {
+#ifdef ENABLE_WALLET
+        if (!GetBoolArg("-disablewallet", false))
+            return InitError("Error: -sysperms is not allowed in combination with enabled wallet functionality");
+#endif
+    } else {
+        umask(077);
+    }
 
     // Clean shutdown on SIGTERM
     struct sigaction sa;