Submitted By: Jim Gifford (patches at jg555 dot com)
Date: 2003-09-14
Initial Package Version: 3.0pl2
Origin: http://www.episec.com/people/edelkind/patches
Description: Adds CHROOT capability to dhcp

Adds 3 options:

	-user <user>
	-group <group>
	-chroot <chroot_dir>

Notes:
	-DPARANOIA must be passed as an argument to the --copts option
	of configure.  Otherwise, the paranoia code will not be compiled
	in.  Example:  ./configure --copts -DPARANOIA

	The chroot() call has been delayed in order to allow /dev/log to
	be reopened after the configuration file has been read.  This is
	beneficial for systems on which /dev/log is a unix domain socket.
	The main side effect is that dhcpd.conf should be placed in /etc,
	instead of <chroot_dir>/etc.

	If dhcpd is to be run on a sysV-style architecture (or, more
	generally, if /dev/log is a character device), one may opt to
	create the <chroot_dir>/dev/log character device and add
	-DEARLY_CHROOT to the --copts option of configure (in addition to
	-DPARANOIA).  This will perform the chroot() call at the earliest
	convenience (before reading the configuration file).

	If the -user option is used, the lease and pid file directories
	should be writable to the server process after it drops
	privileges.

BLFS Instructions:
	 
	groupadd -g 201 dhcp
	useradd -m -g dhcp -u 201 -s /bin/false dhcp
	cd /home/dhcp
	mkdir -p etc var/run var/state
	
	patch -Np1 -i /tmp/dhcpd-3.0p12-chroot-1.patch
	./configure --copts "-DPARANOIA -DEARLY_CHROOT"
	make
	make install

	Create dhcp as listed. Change the Start line to the
	following:

        echo "Starting DHCP Server..."
        loadproc dhcpd -user dhcp -chroot /home/dhcp -cf /etc/dhcpd.conf -q eth1 \
                 -lf /var/state/dhcpd.leases
 
	Create dhcpd.conf in /home/dhcp/etc

	Create dhcpd.leases in /home/var/state/dhcpd.leases

	Last step: chown dhcp.dhcp /home/dhcp -R
	
diff -Naur dhcp-3.0pl2.orig/server/dhcpd.c dhcp-3.0pl2/server/dhcpd.c
--- dhcp-3.0pl2.orig/server/dhcpd.c	2003-01-14 23:02:33.000000000 +0000
+++ dhcp-3.0pl2/server/dhcpd.c	2003-09-15 06:52:08.000000000 +0000
@@ -56,6 +56,16 @@
 #include "version.h"
 #include <omapip/omapip_p.h>
 
+#if defined (PARANOIA)
+#  include <sys/types.h>
+#  include <unistd.h>
+#  include <pwd.h>
+/* get around the ISC declaration of group */
+#  define group real_group 
+#    include <grp.h>
+#  undef group
+#endif /* PARANOIA */
+
 static void usage PROTO ((void));
 
 TIME cur_time;
@@ -204,6 +214,22 @@
 	omapi_object_dereference (&listener, MDL);
 }
 
+#if defined (PARANOIA)
+/* to be used in one of two possible scenarios */
+static void setup_chroot (char *chroot_dir) {
+	if (geteuid())
+		log_fatal ("you must be root to use chroot");
+
+	if (chroot(chroot_dir)) {
+		log_fatal ("chroot(\"%s\"): %m", chroot_dir);
+	}
+	if (chdir ("/")) {
+		/* probably permission denied */
+		log_fatal ("chdir(\"/\"): %m");
+	}
+}
+#endif /* PARANOIA */
+
 int main (argc, argv, envp)
 	int argc;
 	char **argv, **envp;
@@ -236,6 +262,14 @@
 	char *traceinfile = (char *)0;
 	char *traceoutfile = (char *)0;
 #endif
+#if defined (PARANOIA)
+	char *set_user   = 0;
+	char *set_group  = 0;
+	char *set_chroot = 0;
+
+	uid_t set_uid = 0;
+	gid_t set_gid = 0;
+#endif /* PARANOIA */
 
 	/* Make sure we have stdin, stdout and stderr. */
 	status = open ("/dev/null", O_RDWR);
@@ -298,6 +332,20 @@
 			if (++i == argc)
 				usage ();
 			server = argv [i];
+#if defined (PARANOIA)
+		} else if (!strcmp (argv [i], "-user")) {
+			if (++i == argc)
+				usage ();
+			set_user = argv [i];
+		} else if (!strcmp (argv [i], "-group")) {
+			if (++i == argc)
+				usage ();
+			set_group = argv [i];
+		} else if (!strcmp (argv [i], "-chroot")) {
+			if (++i == argc)
+				usage ();
+			set_chroot = argv [i];
+#endif /* PARANOIA */
 		} else if (!strcmp (argv [i], "-cf")) {
 			if (++i == argc)
 				usage ();
@@ -397,6 +445,44 @@
 					     trace_seed_stop, MDL);
 #endif
 
+#if defined (PARANOIA)
+	/* get user and group info if those options were given */
+	if (set_user) {
+		struct passwd *tmp_pwd;
+
+		if (geteuid())
+			log_fatal ("you must be root to set user");
+
+		if (!(tmp_pwd = getpwnam(set_user)))
+			log_fatal ("no such user: %s", set_user);
+
+		set_uid = tmp_pwd->pw_uid;
+
+		/* use the user's group as the default gid */
+		if (!set_group)
+			set_gid = tmp_pwd->pw_gid;
+	}
+
+	if (set_group) {
+/* get around the ISC declaration of group */
+#define group real_group
+		struct group *tmp_grp;
+
+		if (geteuid())
+			log_fatal ("you must be root to set group");
+
+		if (!(tmp_grp = getgrnam(set_group)))
+			log_fatal ("no such group: %s", set_group);
+
+		set_gid = tmp_grp->gr_gid;
+#undef group
+	}
+
+#  if defined (EARLY_CHROOT)
+	if (set_chroot) setup_chroot (set_chroot);
+#  endif /* EARLY_CHROOT */
+#endif /* PARANOIA */
+
 	/* Default to the DHCP/BOOTP port. */
 	if (!local_port)
 	{
@@ -500,6 +586,10 @@
 
 	postconf_initialization (quiet);
 
+#if defined (PARANOIA) && !defined (EARLY_CHROOT)
+	if (set_chroot) setup_chroot (set_chroot);
+#endif /* PARANOIA && !EARLY_CHROOT */
+
         /* test option should cause an early exit */
  	if (cftest && !lftest) 
  		exit(0);
@@ -543,6 +633,22 @@
 			exit (0);
 	}
 
+#if defined (PARANOIA)
+	/* change uid to the specified one */
+
+	if (set_gid) {
+		if (setgroups (0, (void *)0))
+			log_fatal ("setgroups: %m");
+		if (setgid (set_gid))
+			log_fatal ("setgid(%d): %m", (int) set_gid);
+	}	
+
+	if (set_uid) {
+		if (setuid (set_uid))
+			log_fatal ("setuid(%d): %m", (int) set_uid);
+	}
+#endif /* PARANOIA */
+
 	/* Read previous pid file. */
 	if ((i = open (path_dhcpd_pid, O_RDONLY)) >= 0) {
 		status = read (i, pbuf, (sizeof pbuf) - 1);
@@ -888,6 +994,10 @@
 
 	log_fatal ("Usage: dhcpd [-p <UDP port #>] [-d] [-f]%s%s%s%s",
 		   "\n             [-cf config-file] [-lf lease-file]",
+#if defined (PARANOIA)
+		   /* meld into the following string */
+		   "\n             [-user user] [-group group] [-chroot dir]"
+#endif /* PARANOIA */
 #if defined (TRACING)
 		   "\n		   [-tf trace-output-file]",
 		   "\n		   [-play trace-input-file]",