dhcp/dhcp-capability.patch

diff -up dhcp-4.3.4/client/dhclient.8.capability dhcp-4.3.4/client/dhclient.8
--- dhcp-4.3.4/client/dhclient.8.capability	2016-04-29 12:19:40.657129322 +0200
+++ dhcp-4.3.4/client/dhclient.8	2016-04-29 12:19:40.715129297 +0200
@@ -134,6 +134,9 @@ dhclient - Dynamic Host Configuration Pr
 .B -w
 ]
 [
+.B -nc
+]
+[
 .B -B
 ]
 [
@@ -318,6 +321,32 @@ has been added or removed, so that the c
 address on that interface.
 
 .TP
+.BI \-nc
+Do not drop capabilities.
+
+Normally, if
+.B dhclient
+was compiled with libcap-ng support,
+.B dhclient
+drops most capabilities immediately upon startup.  While more secure,
+this greatly restricts the additional actions that hooks in
+.B dhclient-script (8)
+can take.  (For example, any daemons that 
+.B dhclient-script (8)
+starts or restarts will inherit the restricted capabilities as well,
+which may interfere with their correct operation.)  Thus, the
+.BI \-nc
+option can be used to prevent
+.B dhclient
+from dropping capabilities.
+
+The
+.BI \-nc
+option is ignored if
+.B dhclient
+was not compiled with libcap-ng support.
+
+.TP
 .BI \-B
 Set the BOOTP broadcast flag in request packets so servers will always
 broadcast replies.
diff -up dhcp-4.3.4/client/dhclient.c.capability dhcp-4.3.4/client/dhclient.c
--- dhcp-4.3.4/client/dhclient.c.capability	2016-04-29 12:19:40.691129307 +0200
+++ dhcp-4.3.4/client/dhclient.c	2016-04-29 12:21:07.620091930 +0200
@@ -40,6 +40,10 @@
 #include <isc/file.h>
 #include <dns/result.h>
 
+#ifdef HAVE_LIBCAP_NG
+#include <cap-ng.h>
+#endif
+
 /*
  * Defined in stdio.h when _GNU_SOURCE is set, but we don't want to define
  * that when building ISC code.
@@ -237,6 +241,9 @@ main(int argc, char **argv) {
 	int timeout_arg = 0;
 	char *arg_conf = NULL;
 	int arg_conf_len = 0;
+#ifdef HAVE_LIBCAP_NG
+	int keep_capabilities = 0;
+#endif
 
 	/* Initialize client globals. */
 	memset(&default_duid, 0, sizeof(default_duid));
@@ -537,6 +544,10 @@ main(int argc, char **argv) {
 			}
 
 			dhclient_request_options = argv[i];
+		} else if (!strcmp(argv[i], "-nc")) {
+#ifdef HAVE_LIBCAP_NG
+			keep_capabilities = 1;
+#endif
 		} else if (argv[i][0] == '-') {
 			usage("Unknown command: %s", argv[i]);
 		} else if (interfaces_requested < 0) {
@@ -597,6 +608,19 @@ main(int argc, char **argv) {
 		path_dhclient_script = s;
 	}
 
+#ifdef HAVE_LIBCAP_NG
+	/* Drop capabilities */
+	if (!keep_capabilities) {
+		capng_clear(CAPNG_SELECT_CAPS);
+		capng_update(CAPNG_ADD, CAPNG_EFFECTIVE|CAPNG_PERMITTED,
+				CAP_DAC_OVERRIDE); // Drop this someday
+		capng_updatev(CAPNG_ADD, CAPNG_EFFECTIVE|CAPNG_PERMITTED,
+				CAP_NET_ADMIN, CAP_NET_RAW,
+				CAP_NET_BIND_SERVICE, CAP_SYS_ADMIN, -1);
+		capng_apply(CAPNG_SELECT_CAPS);
+	}
+#endif
+
 	/* Set up the initial dhcp option universe. */
 	initialize_common_option_spaces();
 
diff -up dhcp-4.3.4/client/dhclient-script.8.capability dhcp-4.3.4/client/dhclient-script.8
--- dhcp-4.3.4/client/dhclient-script.8.capability	2016-04-29 12:19:40.668129317 +0200
+++ dhcp-4.3.4/client/dhclient-script.8	2016-04-29 12:19:40.717129296 +0200
@@ -243,6 +243,16 @@ repeatedly initialized to the values pro
 the other.   Assuming the information provided by both servers is
 valid, this shouldn't cause any real problems, but it could be
 confusing.
+.PP
+Normally, if dhclient was compiled with libcap-ng support,
+dhclient drops most capabilities immediately upon startup.
+While more secure, this greatly restricts the additional actions that
+hooks in dhclient-script can take. For example, any daemons that
+dhclient-script starts or restarts will inherit the restricted
+capabilities as well, which may interfere with their correct operation.
+Thus, the
+.BI \-nc
+option can be used to prevent dhclient from dropping capabilities.
 .SH SEE ALSO
 dhclient(8), dhcpd(8), dhcrelay(8), dhclient.conf(5) and
 dhclient.leases(5).
diff -up dhcp-4.3.4/client/Makefile.am.capability dhcp-4.3.4/client/Makefile.am
--- dhcp-4.3.4/client/Makefile.am.capability	2016-04-29 12:19:40.652129324 +0200
+++ dhcp-4.3.4/client/Makefile.am	2016-04-29 12:19:40.717129296 +0200
@@ -13,7 +13,7 @@ dhclient_SOURCES = clparse.c dhclient.c
 		   scripts/bsdos scripts/freebsd scripts/linux scripts/macos \
 		   scripts/netbsd scripts/nextstep scripts/openbsd \
 		   scripts/solaris scripts/openwrt
-dhclient_LDADD = ../common/libdhcp.a ../omapip/libomapi.la \
+dhclient_LDADD = ../common/libdhcp.a ../omapip/libomapi.la $(CAPNG_LDADD) \
 		 $(BIND9_LIBDIR) -lirs-export -ldns-export -lisccfg-export -lisc-export
 man_MANS = dhclient.8 dhclient-script.8 dhclient.conf.5 dhclient.leases.5
 EXTRA_DIST = $(man_MANS)
diff -up dhcp-4.3.4/configure.ac.capability dhcp-4.3.4/configure.ac
--- dhcp-4.3.4/configure.ac.capability	2016-04-29 12:19:40.652129324 +0200
+++ dhcp-4.3.4/configure.ac	2016-04-29 12:19:40.717129296 +0200
@@ -585,6 +585,41 @@ AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[]],
 # Look for optional headers.
 AC_CHECK_HEADERS(sys/socket.h net/if_dl.h net/if6.h regex.h)
 
+# look for capabilities library
+AC_ARG_WITH(libcap-ng,
+    [  --with-libcap-ng=[auto/yes/no]  Add Libcap-ng support [default=auto]],,
+    with_libcap_ng=auto)
+
+# Check for Libcap-ng API
+#
+# libcap-ng detection
+if test x$with_libcap_ng = xno ; then
+    have_libcap_ng=no;
+else
+    # Start by checking for header file
+    AC_CHECK_HEADER(cap-ng.h, capng_headers=yes, capng_headers=no)
+
+    # See if we have libcap-ng library
+    AC_CHECK_LIB(cap-ng, capng_clear,
+                 CAPNG_LDADD=-lcap-ng,)
+
+    # Check results are usable
+    if test x$with_libcap_ng = xyes -a x$CAPNG_LDADD = x ; then
+       AC_MSG_ERROR(libcap-ng support was requested and the library was not found)
+    fi
+    if test x$CAPNG_LDADD != x -a $capng_headers = no ; then
+       AC_MSG_ERROR(libcap-ng libraries found but headers are missing)
+    fi
+fi
+AC_SUBST(CAPNG_LDADD)
+AC_MSG_CHECKING(whether to use libcap-ng)
+if test x$CAPNG_LDADD != x ; then
+    AC_DEFINE(HAVE_LIBCAP_NG,1,[libcap-ng support])
+    AC_MSG_RESULT(yes)
+else
+    AC_MSG_RESULT(no)
+fi
+
 # Solaris needs some libraries for functions
 AC_SEARCH_LIBS(socket, [socket])
 AC_SEARCH_LIBS(inet_ntoa, [nsl])
diff -up dhcp-4.3.4/relay/dhcrelay.c.capability dhcp-4.3.4/relay/dhcrelay.c
--- dhcp-4.3.4/relay/dhcrelay.c.capability	2016-04-29 12:19:40.694129306 +0200
+++ dhcp-4.3.4/relay/dhcrelay.c	2016-04-29 12:22:30.278056386 +0200
@@ -32,6 +32,11 @@
 #include <sys/time.h>
 #include <isc/file.h>
 
+#ifdef HAVE_LIBCAP_NG
+#  include <cap-ng.h>
+   int keep_capabilities = 0;
+#endif
+
 TIME default_lease_time = 43200; /* 12 hours... */
 TIME max_lease_time = 86400; /* 24 hours... */
 struct tree_cache *global_options[256];
@@ -454,6 +459,10 @@ main(int argc, char **argv) {
 				usage(use_noarg, argv[i-1]);
 			dhcrelay_sub_id = argv[i];
 #endif
+		} else if (!strcmp(argv[i], "-nc")) {
+#ifdef HAVE_LIBCAP_NG
+			keep_capabilities = 1;
+#endif
 		} else if (!strcmp(argv[i], "-pf")) {
 			if (++i == argc)
 				usage(use_noarg, argv[i-1]);
@@ -528,6 +537,17 @@ main(int argc, char **argv) {
 #endif
 	}
 
+#ifdef HAVE_LIBCAP_NG
+	/* Drop capabilities */
+	if (!keep_capabilities) {
+		capng_clear(CAPNG_SELECT_BOTH);
+		capng_updatev(CAPNG_ADD, CAPNG_EFFECTIVE|CAPNG_PERMITTED,
+				CAP_NET_RAW, CAP_NET_BIND_SERVICE, -1);
+		capng_apply(CAPNG_SELECT_BOTH);
+		log_info ("Dropped all unnecessary capabilities.");
+	}
+#endif
+
 	if (!quiet) {
 		log_info("%s %s", message, PACKAGE_VERSION);
 		log_info(copyright);
@@ -680,6 +700,15 @@ main(int argc, char **argv) {
 	signal(SIGTERM, dhcp_signal_handler);  /* kill */
 #endif
 
+#ifdef HAVE_LIBCAP_NG
+	/* Drop all capabilities */
+	if (!keep_capabilities) {
+		capng_clear(CAPNG_SELECT_BOTH);
+		capng_apply(CAPNG_SELECT_BOTH);
+		log_info ("Dropped all capabilities.");
+	}
+#endif
+
 	/* Start dispatching packets and timeouts... */
 	dispatch();
 
diff -up dhcp-4.3.4/relay/Makefile.am.capability dhcp-4.3.4/relay/Makefile.am
--- dhcp-4.3.4/relay/Makefile.am.capability	2016-04-29 12:19:40.653129323 +0200
+++ dhcp-4.3.4/relay/Makefile.am	2016-04-29 12:19:40.718129295 +0200
@@ -2,7 +2,7 @@ AM_CPPFLAGS = -DLOCALSTATEDIR='"@localst
 
 sbin_PROGRAMS = dhcrelay
 dhcrelay_SOURCES = dhcrelay.c
-dhcrelay_LDADD = ../common/libdhcp.a ../omapip/libomapi.la \
+dhcrelay_LDADD = ../common/libdhcp.a ../omapip/libomapi.la $(CAPNG_LDADD) \
 		 $(BIND9_LIBDIR) -lirs-export -ldns-export -lisccfg-export -lisc-export
 man_MANS = dhcrelay.8
 EXTRA_DIST = $(man_MANS)