dhcp/dhcp-4.2.0-capability.patch

diff -up dhcp-4.2.0/client/dhclient.8.capability dhcp-4.2.0/client/dhclient.8
--- dhcp-4.2.0/client/dhclient.8.capability	2010-07-21 14:27:13.000000000 +0200
+++ dhcp-4.2.0/client/dhclient.8	2010-07-21 16:13:02.000000000 +0200
@@ -109,6 +109,9 @@ relay
 .B -n
 ]
 [
+.B -nc
+]
+[
 .B -nw
 ]
 [
@@ -395,6 +398,32 @@ Do not configure any interfaces.  Most u
 option.
 
 .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 \-nw
 Become a daemon process immediately (nowait) rather than waiting until an IP
 address has been acquired.
diff -up dhcp-4.2.0/client/dhclient.c.capability dhcp-4.2.0/client/dhclient.c
--- dhcp-4.2.0/client/dhclient.c.capability	2010-07-21 14:40:05.000000000 +0200
+++ dhcp-4.2.0/client/dhclient.c	2010-07-21 16:13:52.000000000 +0200
@@ -39,6 +39,10 @@
 #include <limits.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.
@@ -89,6 +93,9 @@ int wanted_ia_ta = 0;
 int wanted_ia_pd = 0;
 char *mockup_relay = NULL;
 int bootp_broadcast_always = 0;
+#ifdef HAVE_LIBCAP_NG
+static int keep_capabilities = 0;
+#endif
 
 extern u_int32_t default_requested_options[];
 
@@ -397,6 +404,10 @@ 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();
 		} else if (interfaces_requested < 0) {
@@ -445,6 +456,19 @@ 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-4.2.0/client/dhclient-script.8.capability dhcp-4.2.0/client/dhclient-script.8
--- dhcp-4.2.0/client/dhclient-script.8.capability	2010-07-21 14:00:16.000000000 +0200
+++ dhcp-4.2.0/client/dhclient-script.8	2010-07-21 16:13:02.000000000 +0200
@@ -239,6 +239,16 @@ 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-4.2.0/client/Makefile.am.capability dhcp-4.2.0/client/Makefile.am
--- dhcp-4.2.0/client/Makefile.am.capability	2009-10-28 05:12:29.000000000 +0100
+++ dhcp-4.2.0/client/Makefile.am	2010-07-21 16:15:29.000000000 +0200
@@ -5,7 +5,7 @@ dhclient_SOURCES = clparse.c dhclient.c 
 		   scripts/netbsd scripts/nextstep scripts/openbsd \
 		   scripts/solaris scripts/openwrt
 dhclient_LDADD = ../common/libdhcp.a ../omapip/libomapi.a \
-		 ../bind/lib/libdns.a ../bind/lib/libisc.a
+		 ../bind/lib/libdns.a ../bind/lib/libisc.a $(CAPNG_LDADD)
 man_MANS = dhclient.8 dhclient-script.8 dhclient.conf.5 dhclient.leases.5
 EXTRA_DIST = $(man_MANS)
 
diff -up dhcp-4.2.0/configure.ac.capability dhcp-4.2.0/configure.ac
--- dhcp-4.2.0/configure.ac.capability	2010-07-10 05:25:51.000000000 +0200
+++ dhcp-4.2.0/configure.ac	2010-07-21 16:13:02.000000000 +0200
@@ -419,6 +419,41 @@ AC_TRY_LINK(
 # 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
+
 # find an MD5 library
 AC_SEARCH_LIBS(MD5_Init, [crypto])
 AC_SEARCH_LIBS(MD5Init, [crypto])