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Nicholas J. Kain
2010-11-12 04:02:18 -05:00
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13
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udhcp server/client package
-----------------------
Russ Dill <Russ.Dill@asu.edu>
Matthew Ramsay <matthewr@moreton.com.au>
Chris Trew <christ@moreton.com.au>
Other Credits:
--------------
Moreton Bay (http://www.moretonbay.com/)
Lineo (http://opensource.lineo.com)

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GNU GENERAL PUBLIC LICENSE
Version 2, June 1991
Copyright (C) 1989, 1991 Free Software Foundation, Inc.
675 Mass Ave, Cambridge, MA 02139, USA
Everyone is permitted to copy and distribute verbatim copies
of this license document, but changing it is not allowed.
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Public License instead of this License.

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All modifications are to udhcp 0.9.8
All bugs should be blamed on Nicholas Kain, not the udhcp folks!
Great thanks go to the authors of udhcp (primarily Russ Dill), from which
ndhc is adapted.
CHANGES
-------
C99 compiler required
removed dhcp server support (use mainline udhcp)
removed sample scripts
added chroot support
added capability support
added setuid/setgid support
run_script now takes int argument (from enum)
script.c heavily modified to call ifchd
stripped command line option for custom script
bounds check all string functions
removed pidfile support: backgrounding model + chroot preclude it
manpage updated
removed busybox compat wrapper
convert all strncpy -> strlcpy
u_int*_t -> uint*_t (C99)
add_simple_option no longer does unspeakable things to the C language
character signedness issues fixed
casting bug [dhcpc.c:549 sizeof(signal) should be sizeof sig]
- won't bite except on an architecture where sizeof fnptr != sizeof int
LOG and DEBUG are abolished - functions are used instead, see log.c/log.h
C99 structure initializers used exclusively (C99)
Linux kernel headers no longer used under any circumstances.
- this is likely to break prehistoric systems running <glibc 2.1
exit() return codes now use EXIT_(SUCCESS|FAILURE) #defines and make more sense
close fd leak on failure in read_interface()
close fd leak on failure in kernel_packet()
char buffer[16] in perform_release() should not be static
don't bother to use a signal pipe - instead use static sig_atomic_t bools
convert lots of #defines to enums
break apart main client loop into maintainable functions
more discerning error handling
boundary check end_option()

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# ndhc makefile
prefix=/usr
SBINDIR=/sbin
USRSBINDIR=${prefix}/sbin
USRBINDIR=${prefix}/bin
USRSHAREDIR=${prefix}/share
# Uncomment this for extra output and to compile with debugging symbols
#DEBUG=1
#CROSS_COMPILE=arm-uclibc-
CC = $(CROSS_COMPILE)gcc
LD = $(CROSS_COMPILE)gcc
INSTALL = install
VER := 0.9.8
OBJS_SHARED = nstrl.o log.o options.o socket.o packet.o rootcap.o
DHCPC_OBJS = dhcpc.o clientpacket.o script.o
EXEC2 = ndhc
OBJS2 = -lcap $(DHCPC_OBJS) $(OBJS_SHARED)
BOOT_PROGRAMS = ndhc
ifdef SYSLOG
CFLAGS += -DSYSLOG
endif
CFLAGS += -W -Wall -Wstrict-prototypes -DVERSION='"$(VER)"'
ifdef DEBUG
CFLAGS += -g -DDEBUG
STRIP=true
else
CFLAGS += -Os -fomit-frame-pointer
STRIP=$(CROSS_COMPILE)strip
endif
all: $(EXEC2)
$(STRIP) --remove-section=.note --remove-section=.comment $(EXEC2)
$(OBJS2) $(OBJS3): *.h Makefile
$(EXEC2): Makefile
.c.o:
$(CC) -c $(CFLAGS) $<
$(EXEC2): $(OBJS2)
$(LD) $(LDFLAGS) $(OBJS2) -o $(EXEC2)
tags:
-ctags -f tags *.[ch]
-cscope -b
install: all
$(INSTALL) $(BOOT_PROGRAMS) $(USRSBINDIR)
mkdir -p $(USRSHAREDIR)/man/man8
$(INSTALL) ndhc.8 ndhc.8 $(USRSHAREDIR)/man/man8
clean:
-rm -f ndhc *.o core
distclean:
-rm -f ndhc *.o tags cscope.out

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ndhc client
--------------------
The ndhc client negotiates a lease with the DHCP server and notifies
ifchd when a leases is obtained or lost.
command line options
-------------------
The command line options for the ndhc client are:
-c, --clientid=CLIENTID Client identifier
-H, --hostname=HOSTNAME Client hostname
-h, Alias for -H
-f, --foreground Do not fork after getting lease
-b, --background Fork to background if lease cannot be
immediately negotiated.
-i, --interface=INTERFACE Interface to use (default: eth0)
-n, --now Exit with failure if lease cannot be
immediately negotiated.
-q, --quit Quit after obtaining lease
-r, --request=IP IP address to request (default: none)
-v, --version Display version
If the requested IP address cannot be obtained, the client accepts the
address that the server offers.
note on ndhc's random seed
---------------------------
ndhc will seed its random number generator (used for generating xid's)
by reading /dev/urandom. If you have a lot of embedded systems on the same
network, with no entropy, you can either seed /dev/urandom by a method of
your own, or doing the following on startup:
ifconfig eth0 > /dev/urandom
in order to seed /dev/urandom with some data (mac address) unique to your
system. If reading /dev/urandom fails, ndhc will fall back to its old
behavior of seeding with time(0).
signals accepted by ndhc
-------------------------
ndhc also responds to SIGUSR1 and SIGUSR2. SIGUSR1 will force a renew state,
and SIGUSR2 will force a release of the current lease, and cause ndhc to
go into an inactive state (until it is killed, or receives a SIGUSR1). You do
not need to sleep between sending signals, as signals received are processed
sequencially in the order they are received.

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TODO
----
+ using time(0) breaks if the system clock changes, find a portable solution
+ make failure of reading functions revert to previous value, not the default
+ sanity code for option[OPT_LEN]
+ fix aliasing (ie: eth0:0)

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/* clientpacket.c
*
* Packet generation and dispatching functions for the DHCP client.
*
* Russ Dill <Russ.Dill@asu.edu> July 2001
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
#include <string.h>
#include <sys/socket.h>
#include <features.h>
#include <netpacket/packet.h>
#include <net/ethernet.h>
#include <stdlib.h>
#include <time.h>
#include <unistd.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include "dhcpd.h"
#include "packet.h"
#include "options.h"
#include "dhcpc.h"
#include "log.h"
/* Create a random xid */
unsigned long random_xid(void)
{
static int initialized;
if (!initialized) {
int fd;
unsigned long seed;
fd = open("/dev/urandom", O_RDONLY);
if (fd == -1 || read(fd, &seed, sizeof(seed)) < 0) {
log_line(LOG_WARNING, "Could not load seed from /dev/urandom: %s\n",
strerror(errno));
seed = time(0);
}
if (fd != -1)
close(fd);
srand(seed);
initialized++;
}
return rand();
}
/* initialize a packet with the proper defaults */
static void init_packet(struct dhcpMessage *packet, char type)
{
struct vendor {
char vendor;
char length;
char str[sizeof("ndhc "VERSION)];
} vendor_id = { DHCP_VENDOR, sizeof("ndhc "VERSION) - 1, "ndhc "VERSION};
init_header(packet, type);
memcpy(packet->chaddr, client_config.arp, 6);
add_option_string(packet->options, client_config.clientid);
if (client_config.hostname)
add_option_string(packet->options, client_config.hostname);
add_option_string(packet->options, (unsigned char *)&vendor_id);
}
/* Add a paramater request list for stubborn DHCP servers. Pull the data
* from the struct in options.c. Don't do bounds checking here because it
* goes towards the head of the packet. */
static void add_requests(struct dhcpMessage *packet)
{
int end = end_option(packet->options);
int i, len = 0;
packet->options[end + OPT_CODE] = DHCP_PARAM_REQ;
for (i = 0; options[i].code; i++)
if (options[i].flags & OPTION_REQ)
packet->options[end + OPT_DATA + len++] = options[i].code;
packet->options[end + OPT_LEN] = len;
packet->options[end + OPT_DATA + len] = DHCP_END;
}
/* Broadcast a DHCP discover packet to the network, with an optionally
* requested IP */
int send_discover(unsigned long xid, unsigned long requested)
{
struct dhcpMessage packet;
init_packet(&packet, DHCPDISCOVER);
packet.xid = xid;
if (requested)
add_simple_option(packet.options, DHCP_REQUESTED_IP, requested);
add_requests(&packet);
log_line(LOG_DEBUG, "Sending discover...\n");
return raw_packet(&packet, INADDR_ANY, CLIENT_PORT, INADDR_BROADCAST,
SERVER_PORT, MAC_BCAST_ADDR, client_config.ifindex);
}
/* Broadcasts a DHCP request message */
int send_selecting(unsigned long xid, unsigned long server,
unsigned long requested)
{
struct dhcpMessage packet;
struct in_addr addr;
init_packet(&packet, DHCPREQUEST);
packet.xid = xid;
add_simple_option(packet.options, DHCP_REQUESTED_IP, requested);
add_simple_option(packet.options, DHCP_SERVER_ID, server);
add_requests(&packet);
addr.s_addr = requested;
log_line(LOG_DEBUG, "Sending select for %s...\n", inet_ntoa(addr));
return raw_packet(&packet, INADDR_ANY, CLIENT_PORT, INADDR_BROADCAST,
SERVER_PORT, MAC_BCAST_ADDR, client_config.ifindex);
}
/* Unicasts or broadcasts a DHCP renew message */
int send_renew(unsigned long xid, unsigned long server, unsigned long ciaddr)
{
struct dhcpMessage packet;
int ret = 0;
init_packet(&packet, DHCPREQUEST);
packet.xid = xid;
packet.ciaddr = ciaddr;
add_requests(&packet);
log_line(LOG_DEBUG, "Sending renew...\n");
if (server)
ret = kernel_packet(&packet, ciaddr, CLIENT_PORT, server, SERVER_PORT);
else
ret = raw_packet(&packet, INADDR_ANY, CLIENT_PORT, INADDR_BROADCAST,
SERVER_PORT, MAC_BCAST_ADDR, client_config.ifindex);
return ret;
}
/* Unicasts a DHCP release message */
int send_release(unsigned long server, unsigned long ciaddr)
{
struct dhcpMessage packet;
init_packet(&packet, DHCPRELEASE);
packet.xid = random_xid();
packet.ciaddr = ciaddr;
add_simple_option(packet.options, DHCP_REQUESTED_IP, ciaddr);
add_simple_option(packet.options, DHCP_SERVER_ID, server);
log_line(LOG_DEBUG, "Sending release...\n");
return kernel_packet(&packet, ciaddr, CLIENT_PORT, server, SERVER_PORT);
}
/* return -1 on errors that are fatal for the socket,
* -2 for those that aren't */
int get_raw_packet(struct dhcpMessage *payload, int fd)
{
int bytes;
struct udp_dhcp_packet packet;
uint32_t source, dest;
uint16_t check;
memset(&packet, 0, sizeof(struct udp_dhcp_packet));
bytes = read(fd, &packet, sizeof(struct udp_dhcp_packet));
if (bytes < 0) {
debug(LOG_INFO, "couldn't read on raw listening socket -- ignoring\n");
usleep(500000); /* possible down interface, looping condition */
return -1;
}
if (bytes < (int) (sizeof(struct iphdr) + sizeof(struct udphdr))) {
debug(LOG_INFO, "message too short, ignoring\n");
return -2;
}
if (bytes < ntohs(packet.ip.tot_len)) {
debug(LOG_INFO, "Truncated packet\n");
return -2;
}
/* ignore any extra garbage bytes */
bytes = ntohs(packet.ip.tot_len);
/* Make sure its the right packet for us, and that it passes
* sanity checks */
if (packet.ip.protocol != IPPROTO_UDP
|| packet.ip.version != IPVERSION
|| packet.ip.ihl != sizeof(packet.ip) >> 2
|| packet.udp.dest != htons(CLIENT_PORT)
|| bytes > (int)sizeof(struct udp_dhcp_packet)
|| ntohs(packet.udp.len) != (short)(bytes - sizeof(packet.ip))) {
debug(LOG_INFO, "unrelated/bogus packet\n");
return -2;
}
/* check IP checksum */
check = packet.ip.check;
packet.ip.check = 0;
if (check != checksum(&(packet.ip), sizeof(packet.ip))) {
debug(LOG_INFO, "bad IP header checksum, ignoring\n");
return -1;
}
/* verify the UDP checksum by replacing the header with a psuedo header */
source = packet.ip.saddr;
dest = packet.ip.daddr;
check = packet.udp.check;
packet.udp.check = 0;
memset(&packet.ip, 0, sizeof(packet.ip));
packet.ip.protocol = IPPROTO_UDP;
packet.ip.saddr = source;
packet.ip.daddr = dest;
packet.ip.tot_len = packet.udp.len; /* cheat on the psuedo-header */
if (check && check != checksum(&packet, bytes)) {
debug(LOG_ERR, "packet with bad UDP checksum received, ignoring\n");
return -2;
}
memcpy(payload, &(packet.data),
bytes - (sizeof(packet.ip) + sizeof(packet.udp)));
if (ntohl(payload->cookie) != DHCP_MAGIC) {
log_line(LOG_ERR, "received bogus message (bad magic) -- ignoring\n");
return -2;
}
debug(LOG_INFO, "oooooh!!! got some!\n");
return bytes - (sizeof(packet.ip) + sizeof(packet.udp));
}

12
ndhc/clientpacket.h Normal file
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#ifndef _CLIENTPACKET_H
#define _CLIENTPACKET_H
unsigned long random_xid(void);
int send_discover(unsigned long xid, unsigned long requested);
int send_selecting(unsigned long xid, unsigned long server, unsigned long requested);
int send_renew(unsigned long xid, unsigned long server, unsigned long ciaddr);
int send_renew(unsigned long xid, unsigned long server, unsigned long ciaddr);
int send_release(unsigned long server, unsigned long ciaddr);
int get_raw_packet(struct dhcpMessage *payload, int fd);
#endif

594
ndhc/dhcpc.c Normal file
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/* dhcpc.c
*
* ndhc DHCP client
*
* Russ Dill <Russ.Dill@asu.edu> July 2001
* Nicholas Kain <njk@-N0SPaM-.kain.us> 2004
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
#include <stdio.h>
#include <sys/time.h>
#include <sys/types.h>
#include <sys/file.h>
#include <unistd.h>
#include <getopt.h>
#include <stdlib.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <signal.h>
#include <time.h>
#include <string.h>
#include <sys/ioctl.h>
#include <net/if.h>
#include <errno.h>
#include <sys/capability.h>
#include <sys/prctl.h>
#include <pwd.h>
#include <grp.h>
#include "dhcpd.h"
#include "dhcpc.h"
#include "options.h"
#include "clientpacket.h"
#include "packet.h"
#include "script.h"
#include "socket.h"
#include "log.h"
#include "rootcap.h"
#include "nstrl.h"
static unsigned long requested_ip, server_addr, timeout;
static unsigned long lease, t1, t2, xid, start;
static int state, packet_num, fd, listen_mode;
static sig_atomic_t pending_exit, pending_renew, pending_release;
enum {
LISTEN_NONE,
LISTEN_KERNEL,
LISTEN_RAW
};
struct client_config_t client_config = {
/* Default options. */
.abort_if_no_lease = 0,
.foreground = 0,
.quit_after_lease = 0,
.background_if_no_lease = 0,
.interface = "eth0",
.script = "none",
.clientid = NULL,
.hostname = NULL,
.ifindex = 0,
.arp = "\0",
};
static void show_usage(void)
{
printf(
"Usage: ndhc [OPTIONS]\n\n"
" -c, --clientid=CLIENTID Client identifier\n"
" -H, --hostname=HOSTNAME Client hostname\n"
" -h Alias for -H\n"
" -f, --foreground Do not fork after getting lease\n"
" -b, --background Fork to background if lease cannot be\n"
" immediately negotiated.\n"
" -i, --interface=INTERFACE Interface to use (default: eth0)\n"
" -n, --now Exit with failure if lease cannot be\n"
" immediately negotiated.\n"
" -q, --quit Quit after obtaining lease\n"
" -r, --request=IP IP address to request (default: none)\n"
" -u, --user Change privileges to this user\n"
" -C, --chroot Directory to which udhcp should chroot\n"
" -v, --version Display version\n"
);
exit(EXIT_SUCCESS);
}
/* just a little helper */
static void change_mode(int new_mode)
{
debug(LOG_INFO, "entering %s listen mode",
new_mode ? (new_mode == 1 ? "kernel" : "raw") : "none");
close(fd);
fd = -1;
listen_mode = new_mode;
}
/* perform a renew */
static void perform_renew(void)
{
log_line(LOG_INFO, "Performing a DHCP renew...\n");
switch (state) {
case BOUND:
change_mode(LISTEN_KERNEL);
case RENEWING:
case REBINDING:
state = RENEW_REQUESTED;
break;
case RENEW_REQUESTED: /* impatient are we? fine, square 1 */
run_script(NULL, SCRIPT_DECONFIG);
case REQUESTING:
case RELEASED:
change_mode(LISTEN_RAW);
state = INIT_SELECTING;
break;
case INIT_SELECTING:
break;
}
/* start things over */
packet_num = 0;
/* Kill any timeouts because the user wants this to hurry along */
timeout = 0;
}
/* perform a release */
static void perform_release(void)
{
char buf[16];
struct in_addr temp_addr;
buf[16] = '\0';
/* send release packet */
if (state == BOUND || state == RENEWING || state == REBINDING) {
temp_addr.s_addr = server_addr;
snprintf(buf, sizeof buf, "%s", inet_ntoa(temp_addr));
temp_addr.s_addr = requested_ip;
log_line(LOG_INFO, "Unicasting a release of %s to %s.\n",
inet_ntoa(temp_addr), buf);
send_release(server_addr, requested_ip); /* unicast */
run_script(NULL, SCRIPT_DECONFIG);
}
log_line(LOG_INFO, "Entering released state.\n");
change_mode(LISTEN_NONE);
state = RELEASED;
timeout = 0x7fffffff;
}
static void signal_handler(int sig)
{
switch (sig) {
case SIGUSR1:
pending_renew = 1;
break;
case SIGUSR2:
pending_release = 1;
break;
case SIGTERM:
pending_exit = 1;
break;
}
}
static void background(void)
{
if (daemon(0, 0) == -1) {
perror("fork");
exit(EXIT_SUCCESS);
}
client_config.foreground = 1; /* Do not fork again. */
}
static void handle_timeout(void)
{
time_t now = time(0);
/* timeout dropped to zero */
switch (state) {
case INIT_SELECTING:
if (packet_num < 3) {
if (packet_num == 0)
xid = random_xid();
/* send discover packet */
send_discover(xid, requested_ip); /* broadcast */
timeout = now + ((packet_num == 2) ? 4 : 2);
packet_num++;
} else {
if (client_config.background_if_no_lease) {
log_line(LOG_INFO, "No lease, going to background.\n");
background();
} else if (client_config.abort_if_no_lease) {
log_line(LOG_INFO, "No lease, failing.\n");
exit(EXIT_FAILURE);
}
/* wait to try again */
packet_num = 0;
timeout = now + 60;
}
break;
case RENEW_REQUESTED:
case REQUESTING:
if (packet_num < 3) {
/* send request packet */
if (state == RENEW_REQUESTED)
/* unicast */
send_renew(xid, server_addr, requested_ip);
else
/* broadcast */
send_selecting(xid, server_addr, requested_ip);
timeout = now + ((packet_num == 2) ? 10 : 2);
packet_num++;
} else {
/* timed out, go back to init state */
if (state == RENEW_REQUESTED)
run_script(NULL, SCRIPT_DECONFIG);
state = INIT_SELECTING;
timeout = now;
packet_num = 0;
change_mode(LISTEN_RAW);
}
break;
case BOUND:
/* Lease is starting to run out, time to enter renewing state */
state = RENEWING;
change_mode(LISTEN_KERNEL);
debug(LOG_INFO, "Entering renew state.\n");
/* fall right through */
case RENEWING:
/* Either set a new T1, or enter REBINDING state */
if ((t2 - t1) <= (lease / 14400 + 1)) {
/* timed out, enter rebinding state */
state = REBINDING;
timeout = now + (t2 - t1);
debug(LOG_INFO, "Entering rebinding state.\n");
} else {
/* send a request packet */
send_renew(xid, server_addr, requested_ip); /* unicast */
t1 = ((t2 - t1) >> 1) + t1;
timeout = t1 + start;
}
break;
case REBINDING:
/* Either set a new T2, or enter INIT state */
if ((lease - t2) <= (lease / 14400 + 1)) {
/* timed out, enter init state */
state = INIT_SELECTING;
log_line(LOG_INFO, "Lease lost, entering init state.\n");
run_script(NULL, SCRIPT_DECONFIG);
timeout = now;
packet_num = 0;
change_mode(LISTEN_RAW);
} else {
/* send a request packet */
send_renew(xid, 0, requested_ip); /* broadcast */
t2 = ((lease - t2) >> 1) + t2;
timeout = t2 + start;
}
break;
case RELEASED:
/* yah, I know, *you* say it would never happen */
timeout = 0x7fffffff;
break;
}
}
static void handle_packet(void)
{
unsigned char *temp = NULL, *message = NULL;
int len;
time_t now = time(0);
struct in_addr temp_addr;
struct dhcpMessage packet;
debug(LOG_INFO, "got a packet\n");
if (listen_mode == LISTEN_KERNEL)
len = get_packet(&packet, fd);
else
len = get_raw_packet(&packet, fd);
if (len == -1 && errno != EINTR) {
debug(LOG_INFO, "error on read, %s, reopening socket.\n",
strerror(errno));
change_mode(listen_mode); /* just close and reopen */
}
if (len < 0)
return;
if (packet.xid != xid) {
debug(LOG_INFO, "Ignoring XID %lx (our xid is %lx).\n",
(unsigned long) packet.xid, xid);
return;
}
if ((message = get_option(&packet, DHCP_MESSAGE_TYPE)) == NULL) {
debug(LOG_ERR, "couldnt get option from packet -- ignoring\n");
return;
}
switch (state) {
case INIT_SELECTING:
/* Must be a DHCPOFFER to one of our xid's */
if (*message == DHCPOFFER) {
if ((temp = get_option(&packet, DHCP_SERVER_ID))) {
memcpy(&server_addr, temp, 4);
xid = packet.xid;
requested_ip = packet.yiaddr;
/* enter requesting state */
state = REQUESTING;
timeout = now;
packet_num = 0;
} else {
debug(LOG_ERR, "No server ID in message\n");
}
}
break;
case RENEW_REQUESTED:
case REQUESTING:
case RENEWING:
case REBINDING:
if (*message == DHCPACK) {
if (!(temp = get_option(&packet, DHCP_LEASE_TIME))) {
log_line(LOG_ERR,
"No lease time received, assuming 1h.\n");
lease = 60 * 60;
} else {
memcpy(&lease, temp, 4);
lease = ntohl(lease);
}
/* enter bound state */
t1 = lease >> 1;
/* little fixed point for n * .875 */
t2 = (lease * 0x7) >> 3;
temp_addr.s_addr = packet.yiaddr;
log_line(LOG_INFO,
"Lease of %s obtained, lease time %ld.\n",
inet_ntoa(temp_addr), lease);
start = now;
timeout = t1 + start;
requested_ip = packet.yiaddr;
run_script(&packet,
((state == RENEWING || state == REBINDING)
? SCRIPT_RENEW : SCRIPT_BOUND));
state = BOUND;
change_mode(LISTEN_NONE);
if (client_config.quit_after_lease)
exit(EXIT_SUCCESS);
if (!client_config.foreground)
background();
} else if (*message == DHCPNAK) {
/* return to init state */
log_line(LOG_INFO, "Received DHCP NAK.\n");
run_script(&packet, SCRIPT_NAK);
if (state != REQUESTING)
run_script(NULL, SCRIPT_DECONFIG);
state = INIT_SELECTING;
timeout = now;
requested_ip = 0;
packet_num = 0;
change_mode(LISTEN_RAW);
sleep(3); /* avoid excessive network traffic */
}
break;
case BOUND:
case RELEASED:
default:
break;
}
}
static int do_work(void)
{
struct timeval tv;
fd_set rfds;
for (;;) {
/* Handle signals asynchronously. */
if (pending_renew)
perform_renew();
if (pending_release)
perform_release();
if (pending_exit) {
log_line(LOG_INFO, "Received SIGTERM. Exiting gracefully.\n");
exit(EXIT_SUCCESS);
}
tv.tv_sec = timeout - time(0);
tv.tv_usec = 0;
if (listen_mode != LISTEN_NONE && fd < 0) {
if (listen_mode == LISTEN_KERNEL)
fd = listen_socket(INADDR_ANY, CLIENT_PORT,
client_config.interface);
else
fd = raw_socket(client_config.ifindex);
if (fd < 0) {
log_line(LOG_ERR, "FATAL: couldn't listen on socket: %s.\n",
strerror(errno));
exit(EXIT_FAILURE);
}
}
if (tv.tv_sec <= 0) {
handle_timeout();
continue;
}
FD_ZERO(&rfds);
if (fd >= 0)
FD_SET(fd, &rfds);
debug(LOG_INFO, "Waiting on select...\n");
if (select(fd + 1, &rfds, NULL, NULL, &tv) == -1) {
switch (errno) {
case EBADF:
fd = -1;
default:
debug(LOG_ERR, "Error: \"%s\" on select!\n",
strerror(errno));
case EINTR: /* Signal received, go back to top. */
continue;
}
}
debug(LOG_INFO, "select suceeded\n");
if (listen_mode != LISTEN_NONE && FD_ISSET(fd, &rfds))
handle_packet();
}
}
int main(int argc, char **argv)
{
char *chroot_dir = NULL;
int c, len;
struct passwd *pwd;
uid_t uid = 0;
gid_t gid = 0;
static struct option arg_options[] = {
{"clientid", required_argument, 0, 'c'},
{"foreground", no_argument, 0, 'f'},
{"background", no_argument, 0, 'b'},
{"hostname", required_argument, 0, 'H'},
{"hostname", required_argument, 0, 'h'},
{"interface", required_argument, 0, 'i'},
{"now", no_argument, 0, 'n'},
{"quit", no_argument, 0, 'q'},
{"request", required_argument, 0, 'r'},
{"version", no_argument, 0, 'v'},
{"user", required_argument, 0, 'u'},
{"chroot", required_argument, 0, 'C'},
{"help", no_argument, 0, '?'},
{0, 0, 0, 0}
};
/* get options */
while (1) {
int option_index = 0;
c = getopt_long(argc, argv, "c:fbH:h:i:np:qr:u:C:v", arg_options,
&option_index);
if (c == -1) break;
switch (c) {
case 'c':
len = strlen(optarg) > 255 ? 255 : strlen(optarg);
if (client_config.clientid)
free(client_config.clientid);
client_config.clientid = malloc(len + 2);
client_config.clientid[OPT_CODE] = DHCP_CLIENT_ID;
client_config.clientid[OPT_LEN] = len;
client_config.clientid[OPT_DATA] = '\0';
strlcpy((char *)client_config.clientid + OPT_DATA, optarg, len);
break;
case 'f':
client_config.foreground = 1;
break;
case 'b':
client_config.background_if_no_lease = 1;
break;
case 'h':
case 'H':
len = strlen(optarg) > 255 ? 255 : strlen(optarg);
if (client_config.hostname)
free(client_config.hostname);
client_config.hostname = malloc(len + 2);
client_config.hostname[OPT_CODE] = DHCP_HOST_NAME;
client_config.hostname[OPT_LEN] = len;
strlcpy((char*)client_config.hostname + 2, optarg, len);
break;
case 'i':
client_config.interface = optarg;
break;
case 'n':
client_config.abort_if_no_lease = 1;
break;
case 'q':
client_config.quit_after_lease = 1;
break;
case 'r':
requested_ip = inet_addr(optarg);
break;
case 'u':
pwd = getpwnam(optarg);
if (pwd) {
uid = (int)pwd->pw_uid;
gid = (int)pwd->pw_gid;
} else {
printf("Bad username provided.\n");
exit(EXIT_FAILURE);
}
break;
case 'C':
len = strlen(optarg) > 255 ? 255 : strlen(optarg);
chroot_dir = malloc(len + 2);
memset(chroot_dir, '\0', len + 2);
strlcpy(chroot_dir, optarg, len);
break;
case 'v':
printf("ndhc, version %s\n\n", VERSION);
exit(EXIT_SUCCESS);
break;
default:
show_usage();
}
}
log_line(LOG_INFO, "ndhc client (v%s) started.\n", VERSION);
if (read_interface(client_config.interface, &client_config.ifindex,
NULL, client_config.arp) < 0)
exit(EXIT_FAILURE);
if (!client_config.clientid) {
client_config.clientid = malloc(6 + 3);
client_config.clientid[OPT_CODE] = DHCP_CLIENT_ID;
client_config.clientid[OPT_LEN] = 7;
client_config.clientid[OPT_DATA] = 1;
memcpy(client_config.clientid + 3, client_config.arp, 6);
}
/* setup signal handlers */
signal(SIGUSR1, signal_handler);
signal(SIGUSR2, signal_handler);
signal(SIGTERM, signal_handler);
if (chdir(chroot_dir)) {
printf("Failed to chdir(%s)!\n", chroot_dir);
exit(EXIT_FAILURE);
}
if (chroot(chroot_dir)) {
printf("Failed to chroot(%s)!\n", chroot_dir);
exit(EXIT_FAILURE);
}
drop_root(uid, gid,
"cap_net_bind_service,cap_net_broadcast,cap_net_raw=ep");
state = INIT_SELECTING;
run_script(NULL, SCRIPT_DECONFIG);
change_mode(LISTEN_RAW);
do_work();
return EXIT_SUCCESS;
}

31
ndhc/dhcpc.h Normal file
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#ifndef _DHCPC_H
#define _DHCPC_H
enum {
INIT_SELECTING,
REQUESTING,
BOUND,
RENEWING,
REBINDING,
INIT_REBOOT,
RENEW_REQUESTED,
RELEASED
};
struct client_config_t {
char foreground; /* Do not fork */
char quit_after_lease; /* Quit after obtaining lease */
char abort_if_no_lease; /* Abort if no lease */
char background_if_no_lease; /* Fork to background if no lease */
char *interface; /* The name of the interface to use */
char *script; /* User script to run at dhcp events */
unsigned char *clientid; /* Optional client id to use */
unsigned char *hostname; /* Optional hostname to use */
int ifindex; /* Index number of the interface to use */
unsigned char arp[6]; /* Our arp address */
};
extern struct client_config_t client_config;
#endif

132
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/* dhcpd.h */
#ifndef _DHCPD_H
#define _DHCPD_H
#include <netinet/ip.h>
#include <netinet/udp.h>
#include "leases.h"
/************************************/
/* Defaults _you_ may want to tweak */
/************************************/
/* the period of time the client is allowed to use that address */
#define LEASE_TIME (60*60*24*10) /* 10 days of seconds */
/*****************************************************************/
/* Do not modify below here unless you know what you are doing!! */
/*****************************************************************/
/* DHCP protocol -- see RFC 2131 */
#define SERVER_PORT 67
#define CLIENT_PORT 68
#define DHCP_MAGIC 0x63825363
/* DHCP option codes (partial list) */
#define DHCP_PADDING 0x00
#define DHCP_SUBNET 0x01
#define DHCP_TIME_OFFSET 0x02
#define DHCP_ROUTER 0x03
#define DHCP_TIME_SERVER 0x04
#define DHCP_NAME_SERVER 0x05
#define DHCP_DNS_SERVER 0x06
#define DHCP_LOG_SERVER 0x07
#define DHCP_COOKIE_SERVER 0x08
#define DHCP_LPR_SERVER 0x09
#define DHCP_HOST_NAME 0x0c
#define DHCP_BOOT_SIZE 0x0d
#define DHCP_DOMAIN_NAME 0x0f
#define DHCP_SWAP_SERVER 0x10
#define DHCP_ROOT_PATH 0x11
#define DHCP_IP_TTL 0x17
#define DHCP_MTU 0x1a
#define DHCP_BROADCAST 0x1c
#define DHCP_NTP_SERVER 0x2a
#define DHCP_WINS_SERVER 0x2c
#define DHCP_REQUESTED_IP 0x32
#define DHCP_LEASE_TIME 0x33
#define DHCP_OPTION_OVER 0x34
#define DHCP_MESSAGE_TYPE 0x35
#define DHCP_SERVER_ID 0x36
#define DHCP_PARAM_REQ 0x37
#define DHCP_MESSAGE 0x38
#define DHCP_MAX_SIZE 0x39
#define DHCP_T1 0x3a
#define DHCP_T2 0x3b
#define DHCP_VENDOR 0x3c
#define DHCP_CLIENT_ID 0x3d
#define DHCP_END 0xFF
enum {
BOOTREQUEST = 1,
BOOTREPLY = 2
};
#define ETH_10MB 1
#define ETH_10MB_LEN 6
enum {
DHCPDISCOVER = 1,
DHCPOFFER = 2,
DHCPREQUEST = 3,
DHCPDECLINE = 4,
DHCPACK = 5,
DHCPNAK = 6,
DHCPRELEASE = 7,
DHCPINFORM = 8
};
#define BROADCAST_FLAG 0x8000
enum {
OPTION_FIELD = 0,
FILE_FIELD = 1,
SNAME_FIELD = 2
};
#define MAC_BCAST_ADDR (unsigned char *) "\xff\xff\xff\xff\xff\xff"
enum {
OPT_CODE = 0,
OPT_LEN = 1,
OPT_DATA = 2
};
struct option_set {
unsigned char *data;
struct option_set *next;
};
struct server_config_t {
uint32_t server; /* Our IP, in network order */
uint32_t start; /* Start address of leases, network order */
uint32_t end; /* End of leases, network order */
struct option_set *options; /* List of DHCP options loaded from the config file */
char *interface; /* The name of the interface to use */
int ifindex; /* Index number of the interface to use */
unsigned char arp[6]; /* Our arp address */
unsigned long lease; /* lease time in seconds (host order) */
unsigned long max_leases; /* maximum number of leases (including reserved address) */
char remaining; /* should the lease file be interpreted as lease time remaining, or
* as the time the lease expires */
unsigned long auto_time; /* how long should udhcpd wait before writing a config file.
* if this is zero, it will only write one on SIGUSR1 */
unsigned long decline_time; /* how long an address is reserved if a client returns a
* decline message */
unsigned long conflict_time; /* how long an arp conflict offender is leased for */
unsigned long offer_time; /* how long an offered address is reserved */
unsigned long min_lease; /* minimum lease a client can request*/
char *lease_file;
char *notify_file; /* What to run whenever leases are written */
uint32_t siaddr; /* next server bootp option */
char *sname; /* bootp server name */
char *boot_file; /* bootp boot file option */
};
extern struct server_config_t server_config;
extern struct dhcpOfferedAddr *leases;
#endif

24
ndhc/leases.h Normal file
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/* leases.h */
#ifndef _LEASES_H
#define _LEASES_H
struct dhcpOfferedAddr {
uint8_t chaddr[16];
uint32_t yiaddr; /* network order */
uint32_t expires; /* host order */
};
extern unsigned char blank_chaddr[];
void clear_lease(uint8_t *chaddr, uint32_t yiaddr);
struct dhcpOfferedAddr *add_lease(uint8_t *chaddr, uint32_t yiaddr, unsigned long lease);
int lease_expired(struct dhcpOfferedAddr *lease);
struct dhcpOfferedAddr *oldest_expired_lease(void);
struct dhcpOfferedAddr *find_lease_by_chaddr(uint8_t *chaddr);
struct dhcpOfferedAddr *find_lease_by_yiaddr(uint32_t yiaddr);
uint32_t find_address(int check_expired);
int check_ip(uint32_t addr);
#endif

20
ndhc/log.c Normal file
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#include <stdio.h>
#include <strings.h>
#include <stdarg.h>
#include <syslog.h>
void log_line(int level, char *format, ...) {
va_list argp;
if (format == NULL) return;
va_start(argp, format);
vfprintf(stderr, format, argp);
va_end(argp);
openlog("ndhc", 0, 0);
va_start(argp, format);
vsyslog(level, format, argp);
va_end(argp);
closelog();
}

11
ndhc/log.h Normal file
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#ifndef H_LOG_H__
#define H_LOG_H__
#include <syslog.h>
void log_line(int level, char *format, ...);
#ifdef DEBUG
#define debug log_line
#else
#define debug(...)
#endif
#endif

56
ndhc/ndhc.8 Normal file
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.TH NDHC 8 2004-02-25 Linux "Linux Administrator's Manual"
.SH NAME
ndhc \- secure DHCP client
.SH SYNOPSIS
.B ndhc
.RI [ OPTION ]...
.SH DESCRIPTION
The ndhc client negotiates a lease with the DHCP server and
informs ifchd of the change when it is obtained or lost.
.SH OPTIONS
.TP
.BI \-c\ CLIENTID ,\ \-\-clientid= CLIENTID
Send the client identifier
.IR CLIENTID .
.TP
.BR -f ,\ \-\-foreground
Do not fork after obtaining a lease.
.TP
.BI \-H\ HOSTNAME ,\ \-\-hostname= HOSTNAME
Send the client hostname
.IR HOSTNAME .
.TP
.BI \-h\ HOSTNAME
Alias for -H
.IR HOSTNAME .
.TP
.BI \-i\ INTERFACE ,\ \-\-interface= INTERFACE
Configure
.IR INTERFACE .
.TP
.BR -n ,\ \-\-now
Exit with failure if a lease cannot be obtained.
.TP
.BR -q ,\ \-\-quit
Exit after obtaining a lease.
.TP
.BI \-r\ ADDRESS ,\ \-\-request= ADDRESS
Request IP address
.IR ADDRESS .
.TP
.BR -v ,\ \-\-version
Display version.
.SH NOTES
.B ndhc
responds to the following signals:
.TP
.B SIGUSR1
This signal causes
.B ndhc
to renew the current lease or, if it does not have one, obtain a
new lease.
.TP
.B SIGUSR2
This signal caused
.B ndhc
to release the current lease.

48
ndhc/nstrl.c Normal file
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/* nstrl.c - strlcpy/strlcat implementation
Time-stamp: <2003-05-28 02:35:13 njk>
(C) 2003 Nicholas Jay Kain <njk@aerifal.cx>
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA */
#include <unistd.h>
#ifndef HAVE_STRLCPY
size_t strlcpy (char *dest, char *src, size_t size)
{
register char *d = dest, *s = src;
for (; *s != '\0' && size > 0; size--, d++, s++)
*d = *s;
*d = '\0';
return (d - dest) + (s - src);
}
size_t strlcat (char *dest, char *src, size_t size)
{
register char *d = dest, *s = src;
for (; size > 0 && *d != '\0'; size--, d++);
for (; *s != '\0' && size > 0; size--, d++, s++)
*d = *s;
*d = '\0';
return (d - dest) + (s - src);
}
#endif

25
ndhc/nstrl.h Normal file
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/* nstrl.h - header file for strlcpy/strlcat implementation
Time-stamp: <2003-05-28 02:34:47 njk>
(C) 2003 Nicholas Jay Kain <njk@aerifal.cx>
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA */
#ifndef NJK_HAVE_STRL_
size_t strlcpy (char *dest, char *src, size_t size);
size_t strlcat (char *dest, char *src, size_t size);
#endif
#define NJK_HAVE_STRL_ 1

228
ndhc/options.c Normal file
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/*
* options.c -- DHCP server option packet tools
* Rewrite by Russ Dill <Russ.Dill@asu.edu> July 2001
* Fixes and hardening: Nicholas Kain <njk@-n0xZpam-.kain.us>
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "log.h"
#include "dhcpd.h"
#include "options.h"
#include "leases.h"
/* supported options are easily added here */
struct dhcp_option options[] = {
/* name[10] flags code */
{"subnet", OPTION_IP | OPTION_REQ, 0x01},
{"timezone", OPTION_S32, 0x02},
{"router", OPTION_IP | OPTION_LIST | OPTION_REQ, 0x03},
{"timesvr", OPTION_IP | OPTION_LIST, 0x04},
{"namesvr", OPTION_IP | OPTION_LIST, 0x05},
{"dns", OPTION_IP | OPTION_LIST | OPTION_REQ, 0x06},
{"logsvr", OPTION_IP | OPTION_LIST, 0x07},
{"cookiesvr", OPTION_IP | OPTION_LIST, 0x08},
{"lprsvr", OPTION_IP | OPTION_LIST, 0x09},
{"hostname", OPTION_STRING | OPTION_REQ, 0x0c},
{"bootsize", OPTION_U16, 0x0d},
{"domain", OPTION_STRING | OPTION_REQ, 0x0f},
{"swapsvr", OPTION_IP, 0x10},
{"rootpath", OPTION_STRING, 0x11},
{"ipttl", OPTION_U8, 0x17},
{"mtu", OPTION_U16, 0x1a},
{"broadcast", OPTION_IP | OPTION_REQ, 0x1c},
{"ntpsrv", OPTION_IP | OPTION_LIST, 0x2a},
{"wins", OPTION_IP | OPTION_LIST, 0x2c},
{"requestip", OPTION_IP, 0x32},
{"lease", OPTION_U32, 0x33},
{"dhcptype", OPTION_U8, 0x35},
{"serverid", OPTION_IP, 0x36},
{"message", OPTION_STRING, 0x38},
{"tftp", OPTION_STRING, 0x42},
{"bootfile", OPTION_STRING, 0x43},
{"", 0x00, 0x00}
};
/* Lengths of the different option types */
int option_lengths[] = {
[OPTION_IP] = 4,
[OPTION_IP_PAIR] = 8,
[OPTION_BOOLEAN] = 1,
[OPTION_STRING] = 1,
[OPTION_U8] = 1,
[OPTION_U16] = 2,
[OPTION_S16] = 2,
[OPTION_U32] = 4,
[OPTION_S32] = 4
};
/* get an option with bounds checking (warning, not aligned). */
unsigned char *get_option(struct dhcpMessage *packet, int code)
{
int i = 0, length = 308;
unsigned char *optionptr;
int over = 0, done = 0, curr = OPTION_FIELD;
optionptr = packet->options;
while (!done) {
if (i >= length) {
log_line(LOG_WARNING, "bogus packet, option fields too long.\n");
return NULL;
}
if (optionptr[i + OPT_CODE] == code) {
if (i + 1 + optionptr[i + OPT_LEN] >= length) {
log_line(LOG_WARNING, "bogus packet, option fields too long.\n");
return NULL;
}
return optionptr + i + 2;
}
switch (optionptr[i + OPT_CODE]) {
case DHCP_PADDING:
i++;
break;
case DHCP_OPTION_OVER:
if (i + 1 + optionptr[i + OPT_LEN] >= length) {
log_line(LOG_WARNING,
"bogus packet, option fields too long.\n");
return NULL;
}
over = optionptr[i + 3];
i += optionptr[OPT_LEN] + 2;
break;
case DHCP_END:
if (curr == OPTION_FIELD && over & FILE_FIELD) {
optionptr = packet->file;
i = 0;
length = 128;
curr = FILE_FIELD;
} else if (curr == FILE_FIELD && over & SNAME_FIELD) {
optionptr = packet->sname;
i = 0;
length = 64;
curr = SNAME_FIELD;
} else done = 1;
break;
default:
i += optionptr[OPT_LEN + i] + 2;
}
}
return NULL;
}
/* return the position of the 'end' option */
int end_option(unsigned char *optionptr)
{
int i = 0;
while (i < 308 && optionptr[i] != DHCP_END) {
if (optionptr[i] == DHCP_PADDING)
++i;
else
i += optionptr[i + OPT_LEN] + 2;
}
return (i < 308 ? i : 308);
}
/* add an option string to the options (an option string contains an option
* code, length, then data) */
int add_option_string(unsigned char *optionptr, unsigned char *string)
{
int end = end_option(optionptr);
/* end position + string length + option code/length + end option */
if (end + string[OPT_LEN] + 2 + 1 >= 308) {
log_line(LOG_ERR, "Option 0x%02x did not fit into the packet!\n",
string[OPT_CODE]);
return 0;
}
debug(LOG_INFO, "adding option 0x%02x\n", string[OPT_CODE]);
memcpy(optionptr + end, string, string[OPT_LEN] + 2);
optionptr[end + string[OPT_LEN] + 2] = DHCP_END;
return string[OPT_LEN] + 2;
}
int add_simple_option(unsigned char *optionptr, unsigned char code,
uint32_t data)
{
int i, length = 0;
unsigned char option[2 + 4];
for (i = 0; options[i].code; i++)
if (options[i].code == code) {
length = option_lengths[options[i].flags & TYPE_MASK];
}
option[OPT_CODE] = code;
option[OPT_LEN] = (unsigned char)length;
if (!length) {
debug(LOG_ERR, "Could not add option 0x%02x\n", code);
return 0;
} else if (length == 1) {
uint8_t t = (uint8_t)data;
memcpy(option + 2, &t, 1);
} else if (length == 2) {
uint16_t t = (uint16_t)data;
memcpy(option + 2, &t, 2);
} else if (length == 4) {
uint32_t t = (uint32_t)data;
memcpy(option + 2, &t, 4);
}
return add_option_string(optionptr, option);
}
/* find option 'code' in opt_list */
struct option_set *find_option(struct option_set *opt_list, char code)
{
while (opt_list && opt_list->data[OPT_CODE] < code)
opt_list = opt_list->next;
if (opt_list && opt_list->data[OPT_CODE] == code) return opt_list;
else return NULL;
}
/* add an option to the opt_list */
void attach_option(struct option_set **opt_list, struct dhcp_option *option,
char *buffer, int length)
{
struct option_set *existing, *new, **curr;
/* add it to an existing option */
if ((existing = find_option(*opt_list, option->code))) {
debug(LOG_INFO, "Attaching option %s to existing member of list\n",
option->name);
if (option->flags & OPTION_LIST) {
if (existing->data[OPT_LEN] + length <= 255) {
existing->data = realloc(existing->data,
existing->data[OPT_LEN] + length + 2);
memcpy(existing->data + existing->data[OPT_LEN] + 2, buffer,
length);
existing->data[OPT_LEN] += length;
} /* else, ignore the data; we could put this in a second option
in the future */
} /* else, ignore the new data */
} else {
debug(LOG_INFO, "Attaching option %s to list\n", option->name);
/* make a new option */
new = malloc(sizeof(struct option_set));
new->data = malloc(length + 2);
new->data[OPT_CODE] = option->code;
new->data[OPT_LEN] = length;
memcpy(new->data + 2, buffer, length);
curr = opt_list;
while (*curr && (*curr)->data[OPT_CODE] < option->code)
curr = &(*curr)->next;
new->next = *curr;
*curr = new;
}
}

40
ndhc/options.h Normal file
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@@ -0,0 +1,40 @@
/* options.h */
#ifndef _OPTIONS_H
#define _OPTIONS_H
#include "packet.h"
#define TYPE_MASK 0x0F
enum {
OPTION_IP=1,
OPTION_IP_PAIR,
OPTION_STRING,
OPTION_BOOLEAN,
OPTION_U8,
OPTION_U16,
OPTION_S16,
OPTION_U32,
OPTION_S32
};
#define OPTION_REQ 0x10 /* have the client request this option */
#define OPTION_LIST 0x20 /* There can be a list of 1 or more of these */
struct dhcp_option {
char name[10];
char flags;
unsigned char code;
};
extern struct dhcp_option options[];
extern int option_lengths[];
unsigned char *get_option(struct dhcpMessage *packet, int code);
int end_option(unsigned char *optionptr);
int add_option_string(unsigned char *optionptr, unsigned char *string);
int add_simple_option(unsigned char *optionptr, unsigned char code, uint32_t data);
struct option_set *find_option(struct option_set *opt_list, char code);
void attach_option(struct option_set **opt_list, struct dhcp_option *option, char *buffer, int length);
#endif

203
ndhc/packet.c Normal file
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#include <unistd.h>
#include <string.h>
#include <netinet/in.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <features.h>
#include <netpacket/packet.h>
#include <net/ethernet.h>
#include <errno.h>
#include "packet.h"
#include "log.h"
#include "dhcpd.h"
#include "options.h"
void init_header(struct dhcpMessage *packet, char type)
{
memset(packet, 0, sizeof(struct dhcpMessage));
switch (type) {
case DHCPDISCOVER:
case DHCPREQUEST:
case DHCPRELEASE:
case DHCPINFORM:
packet->op = BOOTREQUEST;
break;
case DHCPOFFER:
case DHCPACK:
case DHCPNAK:
packet->op = BOOTREPLY;
}
packet->htype = ETH_10MB;
packet->hlen = ETH_10MB_LEN;
packet->cookie = htonl(DHCP_MAGIC);
packet->options[0] = DHCP_END;
add_simple_option(packet->options, DHCP_MESSAGE_TYPE, type);
}
/* read a packet from socket fd, return -1 on read error, -2 on packet error */
int get_packet(struct dhcpMessage *packet, int fd)
{
int bytes;
int i;
const char broken_vendors[][8] = {
"MSFT 98",
""
};
unsigned char *vendor;
memset(packet, 0, sizeof(struct dhcpMessage));
bytes = read(fd, packet, sizeof(struct dhcpMessage));
if (bytes < 0) {
debug(LOG_INFO, "couldn't read on listening socket, ignoring\n");
return -1;
}
if (ntohl(packet->cookie) != DHCP_MAGIC) {
log_line(LOG_ERR, "received bogus message, ignoring.\n");
return -2;
}
debug(LOG_INFO, "Received a packet\n");
if (packet->op == BOOTREQUEST
&& (vendor = get_option(packet, DHCP_VENDOR)))
{
for (i = 0; broken_vendors[i][0]; i++) {
if (vendor[OPT_LEN - 2] == (unsigned char)strlen(broken_vendors[i])
&& !strncmp((char *)vendor, broken_vendors[i],
vendor[OPT_LEN - 2]))
{
debug(LOG_INFO, "broken client (%s), forcing broadcast\n",
broken_vendors[i]);
packet->flags |= htons(BROADCAST_FLAG);
}
}
}
return bytes;
}
uint16_t checksum(void *addr, int count)
{
/* Compute Internet Checksum for "count" bytes
* beginning at location "addr".
*/
register int32_t sum = 0;
uint16_t *source = (uint16_t *)addr;
while (count > 1) {
sum += *source++;
count -= 2;
}
/* Add left-over byte, if any */
if (count > 0) {
/* Make sure that the left-over byte is added correctly both
* with little and big endian hosts */
uint16_t tmp = 0;
*(unsigned char *) (&tmp) = * (unsigned char *) source;
sum += tmp;
}
/* Fold 32-bit sum to 16 bits */
while (sum >> 16)
sum = (sum & 0xffff) + (sum >> 16);
return ~sum;
}
/* Constuct a ip/udp header for a packet, and specify the source and dest
* hardware address */
int raw_packet(struct dhcpMessage *payload, uint32_t source_ip,
int source_port, uint32_t dest_ip, int dest_port,
unsigned char *dest_arp, int ifindex)
{
int fd, result = -1;
struct sockaddr_ll dest;
struct udp_dhcp_packet packet;
if ((fd = socket(PF_PACKET, SOCK_DGRAM, htons(ETH_P_IP))) < 0) {
debug(LOG_ERR, "socket call failed: %s\n", strerror(errno));
goto out;
}
memset(&dest, 0, sizeof(dest));
memset(&packet, 0, sizeof(packet));
dest.sll_family = AF_PACKET;
dest.sll_protocol = htons(ETH_P_IP);
dest.sll_ifindex = ifindex;
dest.sll_halen = 6;
memcpy(dest.sll_addr, dest_arp, 6);
if (bind(fd, (struct sockaddr *)&dest, sizeof(struct sockaddr_ll)) < 0) {
debug(LOG_ERR, "bind call failed: %s\n", strerror(errno));
goto out_fd;
}
packet.ip.protocol = IPPROTO_UDP;
packet.ip.saddr = source_ip;
packet.ip.daddr = dest_ip;
packet.udp.source = htons(source_port);
packet.udp.dest = htons(dest_port);
/* cheat on the psuedo-header */
packet.udp.len = htons(sizeof(packet.udp) + sizeof(struct dhcpMessage));
packet.ip.tot_len = packet.udp.len;
memcpy(&(packet.data), payload, sizeof(struct dhcpMessage));
packet.udp.check = checksum(&packet, sizeof(struct udp_dhcp_packet));
packet.ip.tot_len = htons(sizeof(struct udp_dhcp_packet));
packet.ip.ihl = sizeof(packet.ip) >> 2;
packet.ip.version = IPVERSION;
packet.ip.ttl = IPDEFTTL;
packet.ip.check = checksum(&(packet.ip), sizeof(packet.ip));
result = sendto(fd, &packet, sizeof(struct udp_dhcp_packet), 0,
(struct sockaddr *)&dest, sizeof dest);
if (result <= 0) {
debug(LOG_ERR, "write on socket failed: %s\n",
strerror(errno));
}
out_fd:
close(fd);
out:
return result;
}
/* Let the kernel do all the work for packet generation */
int kernel_packet(struct dhcpMessage *payload, uint32_t source_ip,
int source_port, uint32_t dest_ip, int dest_port)
{
int n = 1, fd, result = -1;
struct sockaddr_in client;
if ((fd = socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP)) < 0)
goto out;
if (setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, (char *) &n, sizeof(n)) == -1)
goto out_fd;
memset(&client, 0, sizeof(client));
client.sin_family = AF_INET;
client.sin_port = htons(source_port);
client.sin_addr.s_addr = source_ip;
if (bind(fd, (struct sockaddr *)&client, sizeof(struct sockaddr)) == -1)
goto out_fd;
memset(&client, 0, sizeof(client));
client.sin_family = AF_INET;
client.sin_port = htons(dest_port);
client.sin_addr.s_addr = dest_ip;
if (connect(fd, (struct sockaddr *)&client, sizeof(struct sockaddr)) == -1)
goto out_fd;
result = write(fd, payload, sizeof(struct dhcpMessage));
out_fd:
close(fd);
out:
return result;
}

41
ndhc/packet.h Normal file
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@@ -0,0 +1,41 @@
#ifndef _PACKET_H
#define _PACKET_H
#include <netinet/udp.h>
#include <netinet/ip.h>
struct dhcpMessage {
uint8_t op;
uint8_t htype;
uint8_t hlen;
uint8_t hops;
uint32_t xid;
uint16_t secs;
uint16_t flags;
uint32_t ciaddr;
uint32_t yiaddr;
uint32_t siaddr;
uint32_t giaddr;
uint8_t chaddr[16];
uint8_t sname[64];
uint8_t file[128];
uint32_t cookie;
uint8_t options[308]; /* 312 - cookie */
};
struct udp_dhcp_packet {
struct iphdr ip;
struct udphdr udp;
struct dhcpMessage data;
};
void init_header(struct dhcpMessage *packet, char type);
int get_packet(struct dhcpMessage *packet, int fd);
uint16_t checksum(void *addr, int count);
int raw_packet(struct dhcpMessage *payload, uint32_t source_ip, int source_port,
uint32_t dest_ip, int dest_port, unsigned char *dest_arp, int ifindex);
int kernel_packet(struct dhcpMessage *payload, uint32_t source_ip, int source_port,
uint32_t dest_ip, int dest_port);
#endif

67
ndhc/rootcap.c Normal file
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#include <unistd.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/capability.h>
#include <sys/prctl.h>
#include <grp.h>
#include "log.h"
static void set_cap(uid_t uid, gid_t gid, char *captxt)
{
cap_t caps;
if (!captxt) {
log_line(LOG_ERR, "FATAL - set_cap: captxt == NULL\n");
exit(EXIT_FAILURE);
}
if (prctl(PR_SET_KEEPCAPS, 1)) {
log_line(LOG_ERR, "FATAL - set_cap: prctl() failed\n");
exit(EXIT_FAILURE);
}
if (setgroups(0, NULL) == -1) {
log_line(LOG_ERR, "FATAL - set_cap: setgroups() failed\n");
exit(EXIT_FAILURE);
}
if (setegid(gid) == -1 || seteuid(uid) == -1) {
log_line(LOG_ERR, "FATAL - set_cap: seteuid() failed\n");
exit(EXIT_FAILURE);
}
caps = cap_from_text(captxt);
if (!caps) {
log_line(LOG_ERR, "FATAL - set_cap: cap_from_text() failed\n");
exit(EXIT_FAILURE);
}
if (cap_set_proc(caps) == -1) {
log_line(LOG_ERR, "FATAL - set_cap: cap_set_proc() failed\n");
exit(EXIT_FAILURE);
}
cap_free(caps);
}
void drop_root(uid_t uid, gid_t gid, char *captxt)
{
if (!captxt) {
log_line(LOG_ERR, "FATAL - drop_root: captxt == NULL\n");
exit(EXIT_FAILURE);
}
if (uid == 0 || gid == 0) {
log_line(LOG_ERR, "FATAL - drop_root: attempt to drop root to root?\n");
exit(EXIT_FAILURE);
}
set_cap(uid, gid, captxt);
if (setregid(gid, gid) == -1 || setreuid(uid, uid) == -1) {
log_line(LOG_ERR, "FATAL - drop_root: failed to drop root!\n");
exit(EXIT_FAILURE);
}
}

2
ndhc/rootcap.h Normal file
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@@ -0,0 +1,2 @@
void drop_root(uid_t uid, gid_t gid, char *captxt);

258
ndhc/script.c Normal file
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@@ -0,0 +1,258 @@
/* script.c
*
* Functions to call the interface change daemon
*
* Russ Dill <Russ.Dill@asu.edu> July 2001
* Nicholas Kain <njk@nozspamz.aerifal.cx> 2004
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
#include <string.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <sys/types.h>
#include <sys/un.h>
#include <sys/wait.h>
#include <errno.h>
#include "options.h"
#include "dhcpd.h"
#include "dhcpc.h"
#include "packet.h"
#include "options.h"
#include "log.h"
#include "script.h"
static int snprintip(char *dest, size_t size, unsigned char *ip) {
if (!dest) return -1;
return snprintf(dest, size, "%d.%d.%d.%d", ip[0], ip[1], ip[2], ip[3]);
}
static int sprintip(char *dest, size_t size, char *pre, unsigned char *ip) {
if (!dest) return -1;
return snprintf(dest, size, "%s%d.%d.%d.%d", pre, ip[0], ip[1], ip[2], ip[3]);
}
/* Fill dest with the text of option 'option'. */
static void fill_options(char *dest, unsigned char *option, struct dhcp_option *type_p, unsigned int maxlen)
{
int type, optlen;
uint16_t val_u16;
int16_t val_s16;
uint32_t val_u32;
int32_t val_s32;
int len = option[OPT_LEN - 2];
char *odest;
odest = dest;
dest += snprintf(dest, maxlen, "%s=", type_p->name);
type = type_p->flags & TYPE_MASK;
optlen = option_lengths[type];
for(;;) {
switch (type) {
case OPTION_IP_PAIR:
dest += sprintip(dest, maxlen - (dest - odest), "", option);
*(dest++) = '/';
option += 4;
optlen = 4;
case OPTION_IP: /* Works regardless of host byte order. */
dest += sprintip(dest, maxlen - (dest - odest), "", option);
break;
case OPTION_BOOLEAN:
dest += snprintf(dest, maxlen - (dest - odest), *option ? "yes " : "no ");
break;
case OPTION_U8:
dest += snprintf(dest, maxlen - (dest - odest), "%u ", *option);
break;
case OPTION_U16:
memcpy(&val_u16, option, 2);
dest += snprintf(dest, maxlen - (dest - odest), "%u ", ntohs(val_u16));
break;
case OPTION_S16:
memcpy(&val_s16, option, 2);
dest += snprintf(dest, maxlen - (dest - odest), "%d ", ntohs(val_s16));
break;
case OPTION_U32:
memcpy(&val_u32, option, 4);
dest += snprintf(dest, maxlen - (dest - odest), "%lu ", (unsigned long) ntohl(val_u32));
break;
case OPTION_S32:
memcpy(&val_s32, option, 4);
dest += snprintf(dest, maxlen - (dest - odest), "%ld ", (long) ntohl(val_s32));
break;
case OPTION_STRING:
if ( (maxlen - (dest - odest)) < (unsigned)len) return;
memcpy(dest, option, len);
dest[len] = '\0';
return; /* Short circuit this case */
}
option += optlen;
len -= optlen;
if (len <= 0) break;
}
}
static int open_ifch(void) {
int sockfd, ret;
struct sockaddr_un address =
{
.sun_family = AF_UNIX,
.sun_path = "ifchange"
};
sockfd = socket(AF_UNIX, SOCK_STREAM, 0);
ret = connect(sockfd, (struct sockaddr *)&address, sizeof(address));
if (ret == -1) {
log_line(LOG_ERR, "unable to connect to ifchd!\n");
exit(EXIT_FAILURE);
}
return sockfd;
}
static void sockwrite(int fd, const void *buf, size_t count)
{
int ret;
sockwrite_again:
ret = write(fd, buf, count);
if (ret == -1) {
if (errno == EAGAIN)
goto sockwrite_again;
log_line(LOG_ERR, "error while writing to unix socket!\n");
exit(EXIT_FAILURE);
}
if (ret < 0) ret = 0;
if ((unsigned int)ret < strlen(buf)) {
log_line(LOG_ERR, "incomplete write!\n");
}
debug(LOG_INFO, "writing: %s\n", (char *)buf);
}
static void deconfig_if(void)
{
int sockfd;
char buf[256];
memset(buf, '\0', sizeof buf);
sockfd = open_ifch();
snprintf(buf, sizeof buf, "interface:%s:",
client_config.interface);
sockwrite(sockfd, buf, strlen(buf));
snprintf(buf, sizeof buf, "ip:0.0.0.0:");
sockwrite(sockfd, buf, strlen(buf));
close(sockfd);
exit(EXIT_SUCCESS);
}
static void translate_option(int sockfd, struct dhcpMessage *packet, int opt) {
char buf[256], buf2[256];
unsigned char *p;
int i;
if (!packet) return;
memset(buf, '\0', sizeof(buf));
memset(buf2, '\0', sizeof(buf2));
p = get_option(packet, options[opt].code);
fill_options(buf2, p, &options[opt], sizeof(buf2) - 1);
snprintf(buf, sizeof buf, "%s:", buf2);
for (i=0; i<256; i++) {
if (buf[i] == '\0') break;
if (buf[i] == '=') {
buf[i] = ':';
break;
}
}
sockwrite(sockfd, buf, strlen(buf));
}
static void bound_if(struct dhcpMessage *packet)
{
int sockfd;
char buf[256], buf2[256];
char ip[32];
if (!packet) return;
memset(buf, '\0', sizeof(buf));
memset(ip, '\0', sizeof(ip));
memset(buf2, '\0', sizeof(buf2));
sockfd = open_ifch();
snprintf(buf, sizeof buf, "interface:%s:", client_config.interface);
sockwrite(sockfd, buf, strlen(buf));
snprintip(ip, sizeof ip, (unsigned char *) &packet->yiaddr);
snprintf(buf, sizeof buf, "ip:%s:", ip);
sockwrite(sockfd, buf, strlen(buf));
translate_option(sockfd, packet, 0);
translate_option(sockfd, packet, 2);
translate_option(sockfd, packet, 5);
translate_option(sockfd, packet, 9);
translate_option(sockfd, packet, 11);
translate_option(sockfd, packet, 15);
translate_option(sockfd, packet, 16);
translate_option(sockfd, packet, 17);
close(sockfd);
exit(EXIT_SUCCESS);
}
void run_script(struct dhcpMessage *packet, int mode)
{
int pid;
pid = fork();
if (pid) {
waitpid(pid, NULL, 0);
return;
} else if (pid == 0) {
switch (mode) {
case SCRIPT_DECONFIG:
deconfig_if();
break;
case SCRIPT_BOUND:
bound_if(packet);
break;
case SCRIPT_RENEW:
bound_if(packet);
break;
case SCRIPT_NAK:
deconfig_if();
break;
default:
break;
}
log_line(LOG_ERR, "invalid script mode: %d\n", mode);
exit(EXIT_FAILURE);
}
}

13
ndhc/script.h Normal file
View File

@@ -0,0 +1,13 @@
#ifndef _SCRIPT_H
#define _SCRIPT_H
enum {
SCRIPT_DECONFIG = 0,
SCRIPT_BOUND = 1,
SCRIPT_RENEW = 2,
SCRIPT_NAK = 4
};
void run_script(struct dhcpMessage *packet, int mode);
#endif

155
ndhc/socket.c Normal file
View File

@@ -0,0 +1,155 @@
/*
* socket.c -- DHCP server client/server socket creation
*
* udhcp client/server
* Copyright (C) 1999 Matthew Ramsay <matthewr@moreton.com.au>
* Chris Trew <ctrew@moreton.com.au>
*
* Rewrite by Russ Dill <Russ.Dill@asu.edu> July 2001
*
* Cleanup and fixes, Nicholas Kain <njk@n0sPaM.kain.us> 2004
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/ioctl.h>
#include <netinet/in.h>
#include <unistd.h>
#include <string.h>
#include <arpa/inet.h>
#include <net/if.h>
#include <errno.h>
#include <features.h>
#include <netpacket/packet.h>
#include <net/ethernet.h>
#include "log.h"
#include "nstrl.h"
int read_interface(char *interface, int *ifindex, uint32_t *addr,
unsigned char *arp)
{
int fd, ret = -1;
struct ifreq ifr;
struct sockaddr_in *our_ip;
memset(&ifr, 0, sizeof(struct ifreq));
if((fd = socket(AF_INET, SOCK_RAW, IPPROTO_RAW)) == -1) {
log_line(LOG_ERR, "socket failed!: %s\n", strerror(errno));
goto out;
}
ifr.ifr_addr.sa_family = AF_INET;
strlcpy(ifr.ifr_name, interface, IFNAMSIZ);
if (addr) {
if (ioctl(fd, SIOCGIFADDR, &ifr)) {
log_line(LOG_ERR, "Couldn't get IP for %s.\n", strerror(errno));
goto out_fd;
}
our_ip = (struct sockaddr_in *) &ifr.ifr_addr;
*addr = our_ip->sin_addr.s_addr;
debug(LOG_INFO, "%s (our ip) = %s\n", ifr.ifr_name,
inet_ntoa(our_ip->sin_addr));
}
if (ioctl(fd, SIOCGIFINDEX, &ifr)) {
log_line(LOG_ERR, "SIOCGIFINDEX failed!: %s\n", strerror(errno));
goto out_fd;
}
debug(LOG_INFO, "adapter index %d\n", ifr.ifr_ifindex);
*ifindex = ifr.ifr_ifindex;
if (ioctl(fd, SIOCGIFHWADDR, &ifr)) {
log_line(LOG_ERR, "Couldn't get MAC for %s\n", strerror(errno));
goto out_fd;
}
memcpy(arp, ifr.ifr_hwaddr.sa_data, 6);
debug(LOG_INFO, "adapter hardware address %02x:%02x:%02x:%02x:%02x:%02x\n",
arp[0], arp[1], arp[2], arp[3], arp[4], arp[5]);
ret = 0;
out_fd:
close(fd);
out:
return ret;
}
int listen_socket(unsigned int ip, int port, char *inf)
{
struct ifreq interface;
int fd;
struct sockaddr_in addr;
int n = 1;
debug(LOG_INFO, "Opening listen socket on 0x%08x:%d %s\n", ip, port, inf);
if ((fd = socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP)) < 0) {
debug(LOG_ERR, "socket call failed: %s\n", strerror(errno));
goto out;
}
memset(&addr, 0, sizeof(addr));
addr.sin_family = AF_INET;
addr.sin_port = htons(port);
addr.sin_addr.s_addr = ip;
if (setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, (char *)&n, sizeof n) == -1)
goto out_fd;
if (setsockopt(fd, SOL_SOCKET, SO_BROADCAST, (char *)&n, sizeof n) == -1)
goto out_fd;
strlcpy(interface.ifr_ifrn.ifrn_name, inf, IFNAMSIZ);
if (setsockopt(fd, SOL_SOCKET, SO_BINDTODEVICE,
(char *)&interface, sizeof interface) < 0)
goto out_fd;
if (bind(fd, (struct sockaddr *)&addr, sizeof(struct sockaddr)) == -1)
goto out_fd;
return fd;
out_fd:
close(fd);
out:
return -1;
}
int raw_socket(int ifindex)
{
int fd;
struct sockaddr_ll sock;
debug(LOG_INFO, "Opening raw socket on ifindex %d\n", ifindex);
if ((fd = socket(PF_PACKET, SOCK_DGRAM, htons(ETH_P_IP))) < 0) {
debug(LOG_ERR, "socket call failed: %s\n", strerror(errno));
goto out;
}
sock.sll_family = AF_PACKET;
sock.sll_protocol = htons(ETH_P_IP);
sock.sll_ifindex = ifindex;
if (bind(fd, (struct sockaddr *) &sock, sizeof(sock)) < 0) {
debug(LOG_ERR, "bind call failed: %s\n", strerror(errno));
goto out_fd;
}
return fd;
out_fd:
close(fd);
out:
return -1;
}

9
ndhc/socket.h Normal file
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@@ -0,0 +1,9 @@
/* socket.h */
#ifndef _SOCKET_H
#define _SOCKET_H
int read_interface(char *interface, int *ifindex, uint32_t *addr, unsigned char *arp);
int listen_socket(unsigned int ip, int port, char *inf);
int raw_socket(int ifindex);
#endif