Date: Mon, 6 Aug 2018 16:22:01 +0000 (UTC) From: Mark Johnston <markj@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r337382 - in head: etc/mtree sbin/dhclient sbin/init/rc.d Message-ID: <201808061622.w76GM1pY069971@repo.freebsd.org>
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Author: markj Date: Mon Aug 6 16:22:01 2018 New Revision: 337382 URL: https://svnweb.freebsd.org/changeset/base/337382 Log: dhclient: Don't chroot if we are in capability mode. The main dhclient process is Capsicumized but also chroots to restrict filesystem access. With r322369, pidfile(3) maintains a directory descriptor for the pidfile, which can cause the chroot to fail in certain cases. To minimize the problem, only chroot if we fail to enter capability mode, and store dhclient pidfiles in a subdirectory of /var/run, thus restricting access via pidfile(3)'s directory descriptor. PR: 223327 Reviewed by: cem, oshogbo Sponsored by: The FreeBSD Foundation Differential Revision: https://reviews.freebsd.org/D16584 Modified: head/etc/mtree/BSD.var.dist head/sbin/dhclient/dhclient.8 head/sbin/dhclient/dhclient.c head/sbin/init/rc.d/dhclient Modified: head/etc/mtree/BSD.var.dist ============================================================================== --- head/etc/mtree/BSD.var.dist Mon Aug 6 15:55:58 2018 (r337381) +++ head/etc/mtree/BSD.var.dist Mon Aug 6 16:22:01 2018 (r337382) @@ -74,6 +74,8 @@ preserve .. run + dhclient + .. ppp gname=network mode=0770 .. wpa_supplicant Modified: head/sbin/dhclient/dhclient.8 ============================================================================== --- head/sbin/dhclient/dhclient.8 Mon Aug 6 15:55:58 2018 (r337381) +++ head/sbin/dhclient/dhclient.8 Mon Aug 6 16:22:01 2018 (r337382) @@ -38,7 +38,7 @@ .\" .\" $FreeBSD$ .\" -.Dd October 13, 2011 +.Dd August 4, 2018 .Dt DHCLIENT 8 .Os .Sh NAME @@ -87,7 +87,7 @@ for the leases file. .It Fl p Ar file Specify an alternate location for the PID file. The default is -.Pa /var/run/dhclient. Ns Ar interface Ns Pa .pid . +.Pa /var/run/dhclient/dhclient. Ns Ar interface Ns Pa .pid . .It Fl q Forces .Nm @@ -194,3 +194,16 @@ and .Pp The current implementation was reworked by .An Henning Brauer Aq Mt henning@openbsd.org . +.Sh BUGS +The +.Nm +utility uses +.Xr capsicum 4 +to sandbox the main process. +If the requisite kernel support is not available, the main process will +attempt to run in a +.Xr chroot 2 +sandbox instead. +This will fail if the process is jailed or the +.Va kern.chroot_allow_open_directories +sysctl is set to 0. Modified: head/sbin/dhclient/dhclient.c ============================================================================== --- head/sbin/dhclient/dhclient.c Mon Aug 6 15:55:58 2018 (r337381) +++ head/sbin/dhclient/dhclient.c Mon Aug 6 16:22:01 2018 (r337382) @@ -371,6 +371,7 @@ init_casper(void) int main(int argc, char *argv[]) { + u_int capmode; int ch, fd, quiet = 0, i = 0; int pipe_fd[2]; int immediate_daemon = 0; @@ -419,7 +420,7 @@ main(int argc, char *argv[]) if (path_dhclient_pidfile == NULL) { asprintf(&path_dhclient_pidfile, - "%sdhclient.%s.pid", _PATH_VARRUN, *argv); + "%s/dhclient/dhclient.%s.pid", _PATH_VARRUN, *argv); if (path_dhclient_pidfile == NULL) error("asprintf"); } @@ -528,11 +529,6 @@ main(int argc, char *argv[]) if (cap_rights_limit(routefd, &rights) < 0 && errno != ENOSYS) error("can't limit route socket: %m"); - if (chroot(_PATH_VAREMPTY) == -1) - error("chroot"); - if (chdir("/") == -1) - error("chdir(\"/\")"); - if (setgroups(1, &pw->pw_gid) || setegid(pw->pw_gid) || setgid(pw->pw_gid) || seteuid(pw->pw_uid) || setuid(pw->pw_uid)) @@ -545,6 +541,19 @@ main(int argc, char *argv[]) if (caph_enter_casper() < 0) error("can't enter capability mode: %m"); + /* + * If we are not in capability mode (i.e., because Capsicum or + * libcasper is disabled), try to restrict filesystem access. This + * will fail if kern.chroot_allow_open_directories is 0 or the process + * is jailed. + */ + if (cap_getmode(&capmode) < 0 || capmode == 0) { + if (chroot(_PATH_VAREMPTY) == -1) + error("chroot"); + if (chdir("/") == -1) + error("chdir(\"/\")"); + } + if (immediate_daemon) go_daemon(); @@ -2449,13 +2458,8 @@ go_daemon(void) cap_rights_init(&rights); - if (pidfile != NULL) { + if (pidfile != NULL) pidfile_write(pidfile); - if (cap_rights_limit(pidfile_fileno(pidfile), &rights) < 0 && - errno != ENOSYS) { - error("can't limit pidfile descriptor: %m"); - } - } if (nullfd != -1) { close(nullfd); Modified: head/sbin/init/rc.d/dhclient ============================================================================== --- head/sbin/init/rc.d/dhclient Mon Aug 6 15:55:58 2018 (r337381) +++ head/sbin/init/rc.d/dhclient Mon Aug 6 16:22:01 2018 (r337382) @@ -14,7 +14,7 @@ ifn="$2" name="dhclient" desc="Dynamic Host Configuration Protocol (DHCP) client" rcvar= -pidfile="/var/run/${name}.${ifn}.pid" +pidfile="/var/run/dhclient/${name}.${ifn}.pid" start_precmd="dhclient_prestart" stop_precmd="dhclient_pre_check"
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