Teach ntpd(8) how to fork+exec.

ok reyk@, bcook@

src/usr.sbin/ntpd/control.c

@@ -1,4 +1,4 @@
-/*	$OpenBSD: control.c,v 1.10 2016/03/27 11:16:12 krw Exp $ */
+/*	$OpenBSD: control.c,v 1.11 2016/09/14 13:20:16 rzalamena Exp $ */
 
 /*
  * Copyright (c) 2003, 2004 Henning Brauer <henning@openbsd.org>
@@ -43,7 +43,7 @@ control_init(char *path)
 	int			 fd;
 	mode_t			 old_umask;
 
-	if ((fd = socket(AF_UNIX, SOCK_STREAM, 0)) == -1) {
+	if ((fd = socket(AF_UNIX, SOCK_STREAM | SOCK_CLOEXEC, 0)) == -1) {
 		log_warn("control_init: socket");
 		return (-1);
 	}

src/usr.sbin/ntpd/ntp.c

@@ -1,4 +1,4 @@
-/*	$OpenBSD: ntp.c,v 1.142 2016/09/03 11:52:06 reyk Exp $ */
+/*	$OpenBSD: ntp.c,v 1.143 2016/09/14 13:20:16 rzalamena Exp $ */
 
 /*
  * Copyright (c) 2003, 2004 Henning Brauer <henning@openbsd.org>
@@ -66,17 +66,16 @@ ntp_sighdlr(int sig)
 	}
 }
 
-pid_t
-ntp_main(int pipe_prnt[2], int fd_ctl, struct ntpd_conf *nconf,
-    struct passwd *pw)
+void
+ntp_main(struct ntpd_conf *nconf, struct passwd *pw, int argc, char **argv)
 {
 	int			 a, b, nfds, i, j, idx_peers, timeout;
 	int			 nullfd, pipe_dns[2], idx_clients;
 	int			 ctls;
+	int			 fd_ctl;
 	u_int			 pfd_elms = 0, idx2peer_elms = 0;
 	u_int			 listener_cnt, new_cnt, sent_cnt, trial_cnt;
 	u_int			 ctl_cnt;
-	pid_t			 pid;
 	struct pollfd		*pfd = NULL;
 	struct servent		*se;
 	struct listen_addr	*la;
@@ -90,15 +89,11 @@ ntp_main(int pipe_prnt[2], int fd_ctl, struct ntpd_conf *nconf,
 	time_t			 nextaction, last_sensor_scan = 0, now;
 	void			*newp;
 
-	switch (pid = fork()) {
-	case -1:
-		fatal("cannot fork");
-		break;
-	case 0:
-		break;
-	default:
-		return (pid);
-	}
+	if (socketpair(AF_UNIX, SOCK_STREAM | SOCK_CLOEXEC, PF_UNSPEC,
+	    pipe_dns) == -1)
+		fatal("socketpair");
+
+	start_child(NTPDNS_PROC_NAME, pipe_dns[1], argc, argv);
 
 	/* in this case the parent didn't init logging and didn't daemonize */
 	if (nconf->settime && !nconf->debug) {
@@ -111,15 +106,14 @@ ntp_main(int pipe_prnt[2], int fd_ctl, struct ntpd_conf *nconf,
 	if ((se = getservbyname("ntp", "udp")) == NULL)
 		fatal("getservbyname");
 
+	/* Start control socket. */
+	if ((fd_ctl = control_init(CTLSOCKET)) == -1)
+		fatalx("control socket init failed");
+	if (control_listen(fd_ctl) == -1)
+		fatalx("control socket listen failed");
 	if ((nullfd = open("/dev/null", O_RDWR, 0)) == -1)
 		fatal(NULL);
 
-	close(pipe_prnt[0]);
-	if (socketpair(AF_UNIX, SOCK_STREAM, PF_UNSPEC, pipe_dns) == -1)
-		fatal("socketpair");
-	ntp_dns(pipe_dns, nconf, pw);
-	close(pipe_dns[1]);
-
 	if (stat(pw->pw_dir, &stb) == -1) {
 		fatal("privsep dir %s could not be opened", pw->pw_dir);
 	}
@@ -163,7 +157,7 @@ ntp_main(int pipe_prnt[2], int fd_ctl, struct ntpd_conf *nconf,
 
 	if ((ibuf_main = malloc(sizeof(struct imsgbuf))) == NULL)
 		fatal(NULL);
-	imsg_init(ibuf_main, pipe_prnt[1]);
+	imsg_init(ibuf_main, PARENT_SOCK_FILENO);
 	if ((ibuf_dns = malloc(sizeof(struct imsgbuf))) == NULL)
 		fatal(NULL);
 	imsg_init(ibuf_dns, pipe_dns[0]);
@@ -422,7 +416,7 @@ ntp_main(int pipe_prnt[2], int fd_ctl, struct ntpd_conf *nconf,
 	free(ibuf_dns);
 
 	log_info("ntp engine exiting");
-	_exit(0);
+	exit(0);
 }
 
 int

src/usr.sbin/ntpd/ntp_dns.c

@@ -1,4 +1,4 @@
-/*	$OpenBSD: ntp_dns.c,v 1.17 2016/09/03 11:52:06 reyk Exp $ */
+/*	$OpenBSD: ntp_dns.c,v 1.18 2016/09/14 13:20:16 rzalamena Exp $ */
 
 /*
  * Copyright (c) 2003-2008 Henning Brauer <henning@openbsd.org>
@@ -49,23 +49,12 @@ sighdlr_dns(int sig)
 	}
 }
 
-pid_t
-ntp_dns(int pipe_ntp[2], struct ntpd_conf *nconf, struct passwd *pw)
+void
+ntp_dns(struct ntpd_conf *nconf, struct passwd *pw)
 {
-	pid_t			 pid;
 	struct pollfd		 pfd[1];
 	int			 nfds, nullfd;
 
-	switch (pid = fork()) {
-	case -1:
-		fatal("cannot fork");
-		break;
-	case 0:
-		break;
-	default:
-		return (pid);
-	}
-
 	if (setpriority(PRIO_PROCESS, 0, 0) == -1)
 		log_warn("could not set priority");
 
@@ -89,8 +78,6 @@ ntp_dns(int pipe_ntp[2], struct ntpd_conf *nconf, struct passwd *pw)
 
 	setproctitle("dns engine");
 
-	close(pipe_ntp[0]);
-
 	if (setgroups(1, &pw->pw_gid) ||
 	    setresgid(pw->pw_gid, pw->pw_gid, pw->pw_gid) ||
 	    setresuid(pw->pw_uid, pw->pw_uid, pw->pw_uid))
@@ -102,7 +89,7 @@ ntp_dns(int pipe_ntp[2], struct ntpd_conf *nconf, struct passwd *pw)
 
 	if ((ibuf_dns = malloc(sizeof(struct imsgbuf))) == NULL)
 		fatal(NULL);
-	imsg_init(ibuf_dns, pipe_ntp[1]);
+	imsg_init(ibuf_dns, PARENT_SOCK_FILENO);
 
 	if (pledge("stdio dns", NULL) == -1)
 		err(1, "pledge");
@@ -135,7 +122,7 @@ ntp_dns(int pipe_ntp[2], struct ntpd_conf *nconf, struct passwd *pw)
 
 	msgbuf_clear(&ibuf_dns->w);
 	free(ibuf_dns);
-	_exit(0);
+	exit(0);
 }
 
 int

src/usr.sbin/ntpd/ntpd.c

@@ -1,4 +1,4 @@
-/*	$OpenBSD: ntpd.c,v 1.108 2016/09/03 11:52:06 reyk Exp $ */
+/*	$OpenBSD: ntpd.c,v 1.109 2016/09/14 13:20:16 rzalamena Exp $ */
 
 /*
  * Copyright (c) 2003, 2004 Henning Brauer <henning@openbsd.org>
@@ -112,7 +112,7 @@ main(int argc, char *argv[])
 	struct pollfd		*pfd = NULL;
 	pid_t			 chld_pid = 0, pid;
 	const char		*conffile;
-	int			 fd_ctl, ch, nfds, i, j;
+	int			 ch, nfds, i, j;
 	int			 pipe_chld[2];
 	extern char		*__progname;
 	u_int			 pfd_elms = 0, new_cnt;
@@ -122,6 +122,9 @@ main(int argc, char *argv[])
 	uid_t			pw_uid;
 	gid_t			pw_gid;
 	void			*newp;
+	int			argc0 = argc;
+	char			**argv0 = argv;
+	char			*pname = NULL;
 
 	if (strcmp(__progname, "ntpctl") == 0) {
 		ctl_main(argc, argv);
@@ -132,7 +135,7 @@ main(int argc, char *argv[])
 
 	memset(&lconf, 0, sizeof(lconf));
 
-	while ((ch = getopt(argc, argv, "df:nsSv")) != -1) {
+	while ((ch = getopt(argc, argv, "df:nP:sSv")) != -1) {
 		switch (ch) {
 		case 'd':
 			lconf.debug = 2;
@@ -144,6 +147,9 @@ main(int argc, char *argv[])
 			lconf.debug = 2;
 			lconf.noaction = 1;
 			break;
+		case 'P':
+			pname = optarg;
+			break;
 		case 's':
 			lconf.settime = 1;
 			break;
@@ -181,6 +187,22 @@ main(int argc, char *argv[])
 	if ((pw = getpwnam(NTPD_USER)) == NULL)
 		errx(1, "unknown user %s", NTPD_USER);
 
+	if (pname != NULL) {
+		/* Remove our proc arguments, so child doesn't need to. */
+		if (sanitize_argv(&argc0, &argv0) == -1)
+			fatalx("sanitize_argv");
+
+		if (strcmp(NTP_PROC_NAME, pname) == 0)
+			ntp_main(&lconf, pw, argc0, argv0);
+		else if (strcmp(NTPDNS_PROC_NAME, pname) == 0)
+			ntp_dns(&lconf, pw);
+		else
+			fatalx("%s: invalid process name '%s'", __func__,
+			    pname);
+
+		fatalx("%s: process '%s' failed", __func__, pname);
+	}
+
 	pw_dir = strdup(pw->pw_dir);
 	pw_uid = pw->pw_uid;
 	pw_gid = pw->pw_gid;
@@ -198,17 +220,14 @@ main(int argc, char *argv[])
 	} else
 		timeout = SETTIME_TIMEOUT * 1000;
 
-	if (socketpair(AF_UNIX, SOCK_STREAM, PF_UNSPEC, pipe_chld) == -1)
+	if (socketpair(AF_UNIX, SOCK_STREAM | SOCK_CLOEXEC, PF_UNSPEC,
+	    pipe_chld) == -1)
 		fatal("socketpair");
 
-	if ((fd_ctl = control_init(CTLSOCKET)) == -1)
-		fatalx("control socket init failed");
-	if (control_listen(fd_ctl) == -1)
-		fatalx("control socket listen failed");
-
 	signal(SIGCHLD, sighdlr);
+
 	/* fork child process */
-	chld_pid = ntp_main(pipe_chld, fd_ctl, &lconf, pw);
+	chld_pid = start_child(NTP_PROC_NAME, pipe_chld[1], argc0, argv0);
 
 	log_procinit("[priv]");
 	readfreq();
@@ -217,7 +236,6 @@ main(int argc, char *argv[])
 	signal(SIGINT, sighdlr);
 	signal(SIGHUP, sighdlr);
 
-	close(pipe_chld[1]);
 	constraint_purge();
 
 	if ((ibuf = malloc(sizeof(struct imsgbuf))) == NULL)

src/usr.sbin/ntpd/ntpd.h

@@ -1,4 +1,4 @@
-/*	$OpenBSD: ntpd.h,v 1.131 2016/09/03 11:52:06 reyk Exp $ */
+/*	$OpenBSD: ntpd.h,v 1.132 2016/09/14 13:20:16 rzalamena Exp $ */
 
 /*
  * Copyright (c) 2003, 2004 Henning Brauer <henning@openbsd.org>
@@ -82,6 +82,11 @@
 #define CONSTRAINT_PASSFD		(STDERR_FILENO + 1)
 #define CONSTRAINT_CA			"/etc/ssl/cert.pem"
 
+#define PARENT_SOCK_FILENO		3
+
+#define NTP_PROC_NAME			"ntp_main"
+#define NTPDNS_PROC_NAME		"ntp_dns"
+
 enum client_state {
 	STATE_NONE,
 	STATE_DNS_INPROGRESS,
@@ -302,7 +307,7 @@ enum ctl_actions {
 /* prototypes */
 
 /* ntp.c */
-pid_t	 ntp_main(int[2], int, struct ntpd_conf *, struct passwd *);
+void	 ntp_main(struct ntpd_conf *, struct passwd *, int, char **);
 int	 priv_adjtime(void);
 void	 priv_settime(double);
 void	 priv_dns(int, char *, u_int32_t);
@@ -372,6 +377,8 @@ double			 sfp_to_d(struct s_fixedpt);
 struct s_fixedpt	 d_to_sfp(double);
 char			*print_rtable(int);
 const char		*log_sockaddr(struct sockaddr *);
+pid_t			 start_child(char *, int, int, char **);
+int			 sanitize_argv(int *, char ***);
 
 /* sensors.c */
 void			sensor_init(void);
@@ -379,7 +386,7 @@ int			sensor_scan(void);
 void			sensor_query(struct ntp_sensor *);
 
 /* ntp_dns.c */
-pid_t	ntp_dns(int[2], struct ntpd_conf *, struct passwd *);
+void			ntp_dns(struct ntpd_conf *, struct passwd *);
 
 /* control.c */
 int			 control_init(char *);

src/usr.sbin/ntpd/util.c

@@ -1,4 +1,4 @@
-/*	$OpenBSD: util.c,v 1.21 2016/09/14 08:24:08 reyk Exp $ */
+/*	$OpenBSD: util.c,v 1.22 2016/09/14 13:20:16 rzalamena Exp $ */
 
 /*
  * Copyright (c) 2004 Alexander Guy <alexander.guy@andern.org>
@@ -18,7 +18,9 @@
 
 #include <limits.h>
 #include <stdio.h>
+#include <stdlib.h>
 #include <time.h>
+#include <unistd.h>
 
 #include "ntpd.h"
 
@@ -151,3 +153,80 @@ log_sockaddr(struct sockaddr *sa)
 	else
 		return (buf);
 }
+
+pid_t
+start_child(char *pname, int cfd, int argc, char **argv)
+{
+	char		**nargv;
+	int		  nargc, i;
+	pid_t		  pid;
+
+	/* Prepare the child process new argv. */
+	nargv = calloc(argc + 3, sizeof(char *));
+	if (nargv == NULL)
+		fatal("%s: calloc", __func__);
+
+	/* Copy the program name first. */
+	nargc = 0;
+	nargv[nargc++] = argv[0];
+
+	/* Set the process name and copy the original args. */
+	nargv[nargc++] = "-P";
+	nargv[nargc++] = pname;
+	for (i = 1; i < argc; i++)
+		nargv[nargc++] = argv[i];
+
+	nargv[nargc] = 0;
+
+	switch (pid = fork()) {
+	case -1:
+		fatal("%s: fork", __func__);
+		break;
+	case 0:
+		/* Prepare the parent socket and execute. */
+		dup2(cfd, PARENT_SOCK_FILENO);
+
+		execvp(argv[0], nargv);
+		fatal("%s: execvp", __func__);
+		break;
+
+	default:
+		/* Close child's socket end. */
+		close(cfd);
+		break;
+	}
+
+	free(nargv);
+	return (pid);
+}
+
+int
+sanitize_argv(int *argc, char ***argv)
+{
+	char		**nargv;
+	int		  nargc;
+	int		  i;
+
+	/*
+	 * We need at least three arguments:
+	 * Example: '/usr/sbin/ntpd' '-P' 'foobar'.
+	 */
+	if (*argc < 3)
+		return (-1);
+
+	*argc -= 2;
+
+	/* Allocate new arguments vector and copy pointers. */
+	nargv = calloc((*argc) + 1, sizeof(char *));
+	if (nargv == NULL)
+		return (-1);
+
+	nargc = 0;
+	nargv[nargc++] = (*argv)[0];
+	for (i = 1; i < *argc; i++)
+		nargv[nargc++] = (*argv)[i + 2];
+
+	nargv[nargc] = NULL;
+	*argv = nargv;
+	return (0);
+}