When ALLOW_START_AS_NON_ROOT is defined, this patch prevents pppd from:
   a) calling seteuid(0) in connect_tty
   b) calling setuid(0) in run_program (for running scripts in /etc/ppp)
We don't want pppd trying to regain root privileges in either of these
cases.

diff --git a/pppd/main.c b/pppd/main.c
index 212540a..8217d80 100644
--- a/pppd/main.c
+++ b/pppd/main.c
@@ -1830,7 +1830,9 @@ run_program(prog, args, must_exist, done, arg, wait)
     (void) setsid();	/* No controlling tty. */
     (void) umask (S_IRWXG|S_IRWXO);
     (void) chdir ("/");	/* no current directory. */
+#ifndef ALLOW_START_AS_NON_ROOT
     setuid(0);		/* set real UID = root */
+#endif
     setgid(getegid());
 
 #ifdef BSD
diff --git a/pppd/tty.c b/pppd/tty.c
index c9a0b33..d76b098 100644
--- a/pppd/tty.c
+++ b/pppd/tty.c
@@ -575,8 +575,10 @@ int connect_tty()
 			}
 			real_ttyfd = open(devnam, O_NONBLOCK | O_RDWR, 0);
 			err = errno;
+#ifndef ALLOW_START_AS_NON_ROOT
 			if (prio < OPRIO_ROOT && seteuid(0) == -1)
 				fatal("Unable to regain privileges");
+#endif
 			if (real_ttyfd >= 0)
 				break;
 			errno = err;