The child processes of snmpd(8) did not detach from the terminal.

Dup /dev/null to the stdio file descriptors in the children.
based on a fix for httpd(8) and relayd(8); from Jan Klemkow

3 files changed, 20 insertions, 9 deletions

diff --git a/usr.sbin/snmpd/proc.c b/usr.sbin/snmpd/proc.c
index eba26bd7e56..d3701186821 100644
--- a/usr.sbin/snmpd/proc.c
+++ b/usr.sbin/snmpd/proc.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: proc.c,v 1.25 2018/08/05 09:33:13 mestre Exp $	*/
+/*	$OpenBSD: proc.c,v 1.26 2019/01/08 15:38:36 bluhm Exp $	*/
 
 /*
  * Copyright (c) 2010 - 2016 Reyk Floeter <reyk@openbsd.org>
@@ -29,13 +29,14 @@
 #include <string.h>
 #include <errno.h>
 #include <signal.h>
+#include <paths.h>
 #include <pwd.h>
 #include <event.h>
 #include <imsg.h>
 
 #include "snmpd.h"
 
-void	 proc_exec(struct privsep *, struct privsep_proc *, unsigned int,
+void	 proc_exec(struct privsep *, struct privsep_proc *, unsigned int, int,
 	    int, char **);
 void	 proc_setup(struct privsep *, struct privsep_proc *, unsigned int);
 void	 proc_open(struct privsep *, int, int);
@@ -80,7 +81,7 @@ proc_getid(struct privsep_proc *procs, unsigned int nproc,
 
 void
 proc_exec(struct privsep *ps, struct privsep_proc *procs, unsigned int nproc,
-    int argc, char **argv)
+    int debug, int argc, char **argv)
 {
 	unsigned int		 proc, nargc, i, proc_i;
 	char			**nargv;
@@ -141,6 +142,16 @@ proc_exec(struct privsep *ps, struct privsep_proc *procs, unsigned int nproc,
 				} else if (fcntl(fd, F_SETFD, 0) == -1)
 					fatal("fcntl");
 
+				/* Daemons detach from terminal. */
+				if (!debug && (fd =
+				    open(_PATH_DEVNULL, O_RDWR, 0)) != -1) {
+					(void)dup2(fd, STDIN_FILENO);
+					(void)dup2(fd, STDOUT_FILENO);
+					(void)dup2(fd, STDERR_FILENO);
+					if (fd > 2)
+						(void)close(fd);
+				}
+
 				execvp(argv[0], nargv);
 				fatal("%s: execvp", __func__);
 				break;
@@ -191,7 +202,7 @@ proc_connect(struct privsep *ps)
 
 void
 proc_init(struct privsep *ps, struct privsep_proc *procs, unsigned int nproc,
-    int argc, char **argv, enum privsep_procid proc_id)
+    int debug, int argc, char **argv, enum privsep_procid proc_id)
 {
 	struct privsep_proc	*p = NULL;
 	struct privsep_pipes	*pa, *pb;
@@ -231,7 +242,7 @@ proc_init(struct privsep *ps, struct privsep_proc *procs, unsigned int nproc,
 		}
 
 		/* Engage! */
-		proc_exec(ps, procs, nproc, argc, argv);
+		proc_exec(ps, procs, nproc, debug, argc, argv);
 		return;
 	}
 
diff --git a/usr.sbin/snmpd/snmpd.c b/usr.sbin/snmpd/snmpd.c
index 4e962ae5eff..48fa45648fe 100644
--- a/usr.sbin/snmpd/snmpd.c
+++ b/usr.sbin/snmpd/snmpd.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: snmpd.c,v 1.40 2018/11/05 11:59:05 mestre Exp $	*/
+/*	$OpenBSD: snmpd.c,v 1.41 2019/01/08 15:38:36 bluhm Exp $	*/
 
 /*
  * Copyright (c) 2007, 2008, 2012 Reyk Floeter <reyk@openbsd.org>
@@ -230,7 +230,7 @@ main(int argc, char *argv[])
 	pf_init();
 	snmpd_generate_engineid(env);
 
-	proc_init(ps, procs, nitems(procs), argc0, argv0, proc_id);
+	proc_init(ps, procs, nitems(procs), debug, argc0, argv0, proc_id);
 	if (!debug && daemon(0, 0) == -1)
 		err(1, "failed to daemonize");
 
diff --git a/usr.sbin/snmpd/snmpd.h b/usr.sbin/snmpd/snmpd.h
index c941c6d9821..338eeea071b 100644
--- a/usr.sbin/snmpd/snmpd.h
+++ b/usr.sbin/snmpd/snmpd.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: snmpd.h,v 1.80 2018/08/05 09:33:13 mestre Exp $	*/
+/*	$OpenBSD: snmpd.h,v 1.81 2019/01/08 15:38:36 bluhm Exp $	*/
 
 /*
  * Copyright (c) 2007, 2008, 2012 Reyk Floeter <reyk@openbsd.org>
@@ -762,7 +762,7 @@ void		 usm_make_report(struct snmp_message *);
 /* proc.c */
 enum privsep_procid
 	    proc_getid(struct privsep_proc *, unsigned int, const char *);
-void	 proc_init(struct privsep *, struct privsep_proc *, unsigned int,
+void	 proc_init(struct privsep *, struct privsep_proc *, unsigned int, int,
 	    int, char **, enum privsep_procid);
 void	 proc_kill(struct privsep *);
 void	 proc_connect(struct privsep *);