Capsicumize rtsol(8) and rtsold(8).

These programs parse ND6 Router Advertisement messages; rtsold(8) has
required an SA, SA-14:20.rtsold, for a bug in this code.  Thus, they
are good candidates for sandboxing.

The approach taken is to run the main executable in capability mode
and use Casper services to provide functionality that cannot be
implemented within the sandbox.  In particular, several custom services
were required.

- A Casper service is used to send Router Solicitation messages on a
  raw ICMP6 socket.  Initially I took the approach of creating a
  socket for each interface upon startup, and connect(2)ing it to
  the all-routers multicast group for the interface.  This permits
  the use of sendmsg(2) in capability mode, but only works if the
  interface's link is up when rtsol(d) starts.  So, instead, the
  rtsold.sendmsg service is used to transmit RS messages on behalf
  of the main process.  One could alternately define a service
  which simply creates and connects a socket for each destination
  address, and returns the socket to the sandboxed process.  However,
  to implement rtsold's -m option we also need to read the ND6 default
  router list, and this cannot be done in capability mode.
- rtsold may execute resolvconf(8) in response to RDNSS and DNSSL
  options in received RA messages.  A Casper service is used to
  fork and exec resolvconf(8), and to reap the child process.
- A service is used to determine whether a given interface's
  link-local address is useable (i.e., not duplicated or undergoing
  DAD).  This information is supplied by getifaddrs(3), which reads
  a sysctl not available in capability mode.  The SIOCGIFCONF socket
  ioctl provides equivalent information and can be used in capability
  mode, but I decided against it for now because of some limitations
  of that interface.

In addition to these new services, cap_syslog(3) is used to send
messages to syslogd.

Reviewed by:	oshogbo
Tested by:	bz (previous versions)
MFC after:	2 months
Sponsored by:	The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D17572

1 files changed, 17 insertions, 3 deletions

diff --git a/sbin/rtsol/Makefile b/sbin/rtsol/Makefile
index 80b38a6af77a..ee22f5756b64 100644
--- a/sbin/rtsol/Makefile
+++ b/sbin/rtsol/Makefile
@@ -18,10 +18,24 @@
 
 PACKAGE=runtime
 PROG=	rtsol
-SRCS=	rtsold.c rtsol.c if.c probe.c dump.c rtsock.c
+SRCS=	cap_llflags.c \
+	cap_script.c \
+	cap_sendmsg.c \
+	dump.c \
+	if.c \
+	rtsol.c \
+	rtsold.c \
+	rtsock.c
 MAN=
+LIBADD=	util
 
-WARNS?=	3
-CFLAGS+= -DSMALL
+.include <src.opts.mk>
+
+.if ${MK_DYNAMICROOT} == "no"
+.warning ${PROG} built without libcasper support
+.elif ${MK_CASPER} != "no" && !defined(RESCUE)
+CFLAGS+= -DWITH_CASPER
+LIBADD+= cap_syslog casper nv
+.endif
 
 .include <bsd.prog.mk>