File: [local] / src / usr.sbin / rarpd / rarpd.c (download)
Revision 1.80, Tue Oct 4 07:01:38 2022 UTC (20 months ago) by kn
Branch: MAIN
CVS Tags: OPENBSD_7_5_BASE, OPENBSD_7_5, OPENBSD_7_4_BASE, OPENBSD_7_4, OPENBSD_7_3_BASE, OPENBSD_7_3, HEAD Changes since 1.79: +4 -3 lines
Unveil /tftpboot only if needed
Unless -t is used, this directory is not accessed in any way.
OK millert
|
/* $OpenBSD: rarpd.c,v 1.80 2022/10/04 07:01:38 kn Exp $ */
/* $NetBSD: rarpd.c,v 1.25 1998/04/23 02:48:33 mrg Exp $ */
/*
* Copyright (c) 1990 The Regents of the University of California.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that: (1) source code distributions
* retain the above copyright notice and this paragraph in its entirety, (2)
* distributions including binary code include the above copyright notice and
* this paragraph in its entirety in the documentation or other materials
* provided with the distribution, and (3) all advertising materials mentioning
* features or use of this software display the following acknowledgement:
* ``This product includes software developed by the University of California,
* Lawrence Berkeley Laboratory and its contributors.'' Neither the name of
* the University nor the names of its contributors may be used to endorse
* or promote products derived from this software without specific prior
* written permission.
* THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
* WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
*/
/*
* rarpd - Reverse ARP Daemon
*/
#include <sys/socket.h>
#include <sys/ioctl.h>
#include <net/bpf.h>
#include <net/if.h>
#include <net/if_dl.h>
#include <net/if_types.h>
#include <netinet/in.h>
#include <netinet/if_ether.h>
#include <stdio.h>
#include <stdlib.h>
#include <syslog.h>
#include <string.h>
#include <stdarg.h>
#include <unistd.h>
#include <limits.h>
#include <errno.h>
#include <fcntl.h>
#include <netdb.h>
#include <arpa/inet.h>
#include <dirent.h>
#include <poll.h>
#include <ifaddrs.h>
/*
* The structures for each interface.
*/
struct if_addr {
in_addr_t ia_ipaddr; /* IP address of this interface */
in_addr_t ia_netmask; /* subnet or net mask */
struct if_addr *ia_next;
};
struct if_info {
int ii_fd; /* BPF file descriptor */
char ii_name[IFNAMSIZ]; /* if name, e.g. "en0" */
u_char ii_eaddr[ETHER_ADDR_LEN]; /* Ethernet address of this iface */
struct if_addr *ii_addrs; /* Networks this interface is on */
struct if_info *ii_next;
};
/*
* The list of all interfaces that are being listened to. rarp_loop()
* "selects" on the descriptors in this list.
*/
struct if_info *iflist;
int rarp_open(char *);
void init_one(char *);
void init_all(void);
void rarp_loop(void);
void lookup_addrs(char *, struct if_info *);
__dead void usage(void);
void rarp_process(struct if_info *, u_char *);
void rarp_reply(struct if_info *, struct if_addr *,
struct ether_header *, u_int32_t, struct hostent *);
void arptab_init(void);
int arptab_set(u_char *, u_int32_t);
__dead void error(const char *, ...);
void warning(const char *, ...);
void debug(const char *, ...);
u_int32_t ipaddrtonetmask(u_int32_t);
int rarp_bootable(u_int32_t);
int aflag = 0; /* listen on "all" interfaces */
int dflag = 0; /* print debugging messages */
int fflag = 0; /* don't fork */
int lflag = 0; /* log all replies */
int tflag = 0; /* tftpboot check */
#ifndef TFTP_DIR
#define TFTP_DIR "/tftpboot"
#endif
int
main(int argc, char *argv[])
{
extern char *__progname;
int op;
/* All error reporting is done through syslogs. */
openlog(__progname, LOG_PID | LOG_CONS, LOG_DAEMON);
opterr = 0;
while ((op = getopt(argc, argv, "adflt")) != -1) {
switch (op) {
case 'a':
++aflag;
break;
case 'd':
++dflag;
break;
case 'f':
++fflag;
break;
case 'l':
++lflag;
break;
case 't':
++tflag;
break;
default:
usage();
}
}
argc -= optind;
argv += optind;
if ((aflag && argc > 0) || (!aflag && argc == 0))
usage();
if (aflag)
init_all();
else
while (argc > 0) {
init_one(argv[0]);
argc--;
argv++;
}
if ((!fflag) && (!dflag)) {
if (daemon(0, 0) == -1)
error("failed to daemonize: %s", strerror(errno));
}
rarp_loop();
exit(0);
}
/*
* Add 'ifname' to the interface list. Lookup its IP address and network
* mask and Ethernet address, and open a BPF file for it.
*/
void
init_one(char *ifname)
{
struct if_info *p;
int fd;
/* first check to see if this "if" was already opened? */
for (p = iflist; p; p = p->ii_next)
if (!strncmp(p->ii_name, ifname, IFNAMSIZ))
return;
fd = rarp_open(ifname);
if (fd < 0)
return;
p = malloc(sizeof(*p));
if (p == 0)
error("malloc: %s", strerror(errno));
p->ii_next = iflist;
iflist = p;
p->ii_fd = fd;
strncpy(p->ii_name, ifname, IFNAMSIZ);
p->ii_addrs = NULL;
lookup_addrs(ifname, p);
}
/*
* Initialize all "candidate" interfaces that are in the system
* configuration list. A "candidate" is up, not loopback and not
* point to point.
*/
void
init_all(void)
{
struct ifaddrs *ifap, *ifa;
struct sockaddr_dl *sdl;
if (getifaddrs(&ifap) != 0)
error("getifaddrs: %s", strerror(errno));
for (ifa = ifap; ifa; ifa = ifa->ifa_next) {
if (ifa->ifa_addr == NULL)
continue;
sdl = (struct sockaddr_dl *)ifa->ifa_addr;
if (sdl->sdl_family != AF_LINK || sdl->sdl_type != IFT_ETHER ||
sdl->sdl_alen != 6)
continue;
if ((ifa->ifa_flags &
(IFF_UP | IFF_LOOPBACK | IFF_POINTOPOINT)) != IFF_UP)
continue;
init_one(ifa->ifa_name);
}
freeifaddrs(ifap);
}
__dead void
usage(void)
{
(void) fprintf(stderr, "usage: rarpd [-adflt] if0 [... ifN]\n");
exit(1);
}
static struct bpf_insn insns[] = {
BPF_STMT(BPF_LD | BPF_H | BPF_ABS, 12),
BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, ETHERTYPE_REVARP, 0, 3),
BPF_STMT(BPF_LD | BPF_H | BPF_ABS, 20),
BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, ARPOP_REVREQUEST, 0, 1),
BPF_STMT(BPF_RET | BPF_K, sizeof(struct ether_arp) +
sizeof(struct ether_header)),
BPF_STMT(BPF_RET | BPF_K, 0),
};
static struct bpf_program filter = {
sizeof insns / sizeof(insns[0]),
insns
};
/*
* Open a BPF file and attach it to the interface named 'device'.
* Set immediate mode, and set a filter that accepts only RARP requests.
*/
int
rarp_open(char *device)
{
int fd, immediate;
struct ifreq ifr;
u_int dlt;
if ((fd = open("/dev/bpf", O_RDWR)) == -1)
error("/dev/bpf: %s", strerror(errno));
/* Set immediate mode so packets are processed as they arrive. */
immediate = 1;
if (ioctl(fd, BIOCIMMEDIATE, &immediate) == -1) {
error("BIOCIMMEDIATE: %s", strerror(errno));
}
(void) strncpy(ifr.ifr_name, device, sizeof ifr.ifr_name);
if (ioctl(fd, BIOCSETIF, (caddr_t)&ifr) == -1) {
if (aflag) { /* for -a skip not ethernet interfaces */
close(fd);
return -1;
}
error("BIOCSETIF: %s", strerror(errno));
}
/*
* Check that the data link layer is an Ethernet; this code
* won't work with anything else.
*/
if (ioctl(fd, BIOCGDLT, (caddr_t) &dlt) == -1)
error("BIOCGDLT: %s", strerror(errno));
if (dlt != DLT_EN10MB) {
if (aflag) { /* for -a skip not ethernet interfaces */
close(fd);
return -1;
}
error("%s is not an ethernet", device);
}
/* Set filter program. */
if (ioctl(fd, BIOCSETF, (caddr_t)&filter) == -1)
error("BIOCSETF: %s", strerror(errno));
return fd;
}
/*
* Perform various sanity checks on the RARP request packet. Return
* false on failure and log the reason.
*/
static int
rarp_check(u_char *p, int len)
{
struct ether_header *ep = (struct ether_header *) p;
struct ether_arp *ap = (struct ether_arp *) (p + sizeof(*ep));
(void) debug("got a packet");
if (len < sizeof(*ep) + sizeof(*ap)) {
warning("truncated request");
return 0;
}
/* XXX This test might be better off broken out... */
if (ntohs (ep->ether_type) != ETHERTYPE_REVARP ||
ntohs (ap->arp_hrd) != ARPHRD_ETHER ||
ntohs (ap->arp_op) != ARPOP_REVREQUEST ||
ntohs (ap->arp_pro) != ETHERTYPE_IP ||
ap->arp_hln != 6 || ap->arp_pln != 4) {
warning("request fails sanity check");
return 0;
}
if (memcmp((char *) &ep->ether_shost, (char *) &ap->arp_sha, 6) != 0) {
warning("ether/arp sender address mismatch");
return 0;
}
if (memcmp((char *) &ap->arp_sha, (char *) &ap->arp_tha, 6) != 0) {
warning("ether/arp target address mismatch");
return 0;
}
return 1;
}
/*
* Loop indefinitely listening for RARP requests on the
* interfaces in 'iflist'.
*/
void
rarp_loop(void)
{
int cc, fd, numfd = 0, i;
u_int bufsize;
struct pollfd *pfd;
u_char *buf, *bp, *ep;
struct if_info *ii;
if (iflist == 0)
error("no interfaces");
if (ioctl(iflist->ii_fd, BIOCGBLEN, (caddr_t)&bufsize) == -1)
error("BIOCGBLEN: %s", strerror(errno));
arptab_init();
if (tflag)
if (unveil(TFTP_DIR, "r") == -1)
error("unveil %s", TFTP_DIR);
if (unveil("/etc/ethers", "r") == -1)
error("unveil /etc/ethers");
if (pledge("stdio rpath dns", NULL) == -1)
error("pledge");
buf = malloc((size_t) bufsize);
if (buf == 0)
error("malloc: %s", strerror(errno));
/*
* Initialize the set of descriptors to listen to.
*/
for (ii = iflist; ii; ii = ii->ii_next)
numfd++;
pfd = reallocarray(NULL, numfd, sizeof(*pfd));
if (pfd == NULL)
error("reallocarray: %s", strerror(errno));
for (i = 0, ii = iflist; ii; ii = ii->ii_next, i++) {
pfd[i].fd = ii->ii_fd;
pfd[i].events = POLLIN;
}
while (1) {
if (poll(pfd, numfd, -1) == -1) {
if (errno == EINTR)
continue;
error("poll: %s", strerror(errno));
}
for (i = 0, ii = iflist; ii; ii = ii->ii_next, i++) {
if (pfd[i].revents == 0)
continue;
fd = ii->ii_fd;
again:
cc = read(fd, (char *)buf, bufsize);
/* Don't choke when we get ptraced */
if (cc == -1 && errno == EINTR)
goto again;
if (cc == -1)
error("read: %s", strerror(errno));
/* Loop through the packet(s) */
#define bhp ((struct bpf_hdr *)bp)
bp = buf;
ep = bp + cc;
while (bp < ep) {
int caplen, hdrlen;
caplen = bhp->bh_caplen;
hdrlen = bhp->bh_hdrlen;
if (rarp_check(bp + hdrlen, caplen))
rarp_process(ii, bp + hdrlen);
bp += BPF_WORDALIGN(hdrlen + caplen);
}
}
}
free(pfd);
}
/*
* True if this server can boot the host whose IP address is 'addr'.
* This check is made by looking in the tftp directory for the
* configuration file.
*/
int
rarp_bootable(u_int32_t addr)
{
struct dirent *dent;
char ipname[40];
static DIR *dd = 0;
DIR *d;
(void) snprintf(ipname, sizeof ipname, "%08X", addr);
/* If directory is already open, rewind it. Otherwise, open it. */
if ((d = dd))
rewinddir(d);
else {
if (chdir(TFTP_DIR) == -1)
error("chdir: %s", strerror(errno));
d = opendir(".");
if (d == 0)
error("opendir: %s", strerror(errno));
dd = d;
}
while ((dent = readdir(d)))
if (strncmp(dent->d_name, ipname, 8) == 0)
return 1;
return 0;
}
/*
* Given a list of IP addresses, 'alist', return the first address that
* is on network 'net'; 'netmask' is a mask indicating the network portion
* of the address.
*/
static u_int32_t
choose_ipaddr(u_int32_t **alist, u_int32_t net, u_int32_t netmask)
{
for (; *alist; ++alist) {
if ((**alist & netmask) == net)
return **alist;
}
return 0;
}
/*
* Answer the RARP request in 'pkt', on the interface 'ii'. 'pkt' has
* already been checked for validity. The reply is overlaid on the request.
*/
void
rarp_process(struct if_info *ii, u_char *pkt)
{
char ename[HOST_NAME_MAX+1];
u_int32_t target_ipaddr;
struct ether_header *ep;
struct ether_addr *ea;
struct hostent *hp;
struct in_addr in;
struct if_addr *ia;
ep = (struct ether_header *) pkt;
ea = (struct ether_addr *) &ep->ether_shost;
debug("%s", ether_ntoa(ea));
if (ether_ntohost(ename, ea) != 0) {
debug("ether_ntohost failed");
return;
}
if ((hp = gethostbyname(ename)) == 0) {
debug("gethostbyname (%s) failed", ename);
return;
}
/* Choose correct address from list. */
if (hp->h_addrtype != AF_INET)
error("cannot handle non IP addresses");
for (target_ipaddr = 0, ia = ii->ii_addrs; ia; ia = ia->ia_next) {
target_ipaddr = choose_ipaddr((u_int32_t **) hp->h_addr_list,
ia->ia_ipaddr & ia->ia_netmask, ia->ia_netmask);
if (target_ipaddr)
break;
}
if (target_ipaddr == 0) {
for (ia = ii->ii_addrs; ia; ia = ia->ia_next) {
in.s_addr = ia->ia_ipaddr & ia->ia_netmask;
warning("cannot find %s on net %s",
ename, inet_ntoa(in));
}
return;
}
if (tflag == 0 || rarp_bootable(htonl(target_ipaddr)))
rarp_reply(ii, ia, ep, target_ipaddr, hp);
debug("reply sent");
}
/*
* Lookup the ethernet address of the interface attached to the BPF
* file descriptor 'fd'; return it in 'eaddr'.
*/
void
lookup_addrs(char *ifname, struct if_info *p)
{
struct ifaddrs *ifap, *ifa;
struct sockaddr_dl *sdl;
u_char *eaddr = p->ii_eaddr;
struct if_addr *ia, **iap = &p->ii_addrs;
struct in_addr in;
int found = 0;
if (getifaddrs(&ifap) != 0)
error("getifaddrs: %s", strerror(errno));
for (ifa = ifap; ifa; ifa = ifa->ifa_next) {
if (strcmp(ifa->ifa_name, ifname))
continue;
if (ifa->ifa_addr == NULL)
continue;
sdl = (struct sockaddr_dl *) ifa->ifa_addr;
if (sdl->sdl_family == AF_LINK &&
sdl->sdl_type == IFT_ETHER && sdl->sdl_alen == 6) {
memcpy((caddr_t)eaddr, (caddr_t)LLADDR(sdl), 6);
if (dflag)
fprintf(stderr, "%s: %x:%x:%x:%x:%x:%x\n",
ifa->ifa_name,
eaddr[0], eaddr[1], eaddr[2],
eaddr[3], eaddr[4], eaddr[5]);
found = 1;
} else if (sdl->sdl_family == AF_INET) {
ia = malloc(sizeof (struct if_addr));
if (ia == NULL)
error("lookup_addrs: malloc: %s",
strerror(errno));
ia->ia_next = NULL;
ia->ia_ipaddr =
((struct sockaddr_in *) ifa->ifa_addr)->
sin_addr.s_addr;
ia->ia_netmask =
((struct sockaddr_in *) ifa->ifa_netmask)->
sin_addr.s_addr;
/* Figure out a mask from the IP address class. */
if (ia->ia_netmask == 0)
ia->ia_netmask =
ipaddrtonetmask(ia->ia_ipaddr);
if (dflag) {
in.s_addr = ia->ia_ipaddr;
fprintf(stderr, "\t%s\n",
inet_ntoa(in));
}
*iap = ia;
iap = &ia->ia_next;
}
}
freeifaddrs(ifap);
if (!found)
error("lookup_addrs: Never saw interface `%s'!", ifname);
}
/*
* Build a reverse ARP packet and sent it out on the interface.
* 'ep' points to a valid ARPOP_REVREQUEST. The ARPOP_REVREPLY is built
* on top of the request, then written to the network.
*
* RFC 903 defines the ether_arp fields as follows. The following comments
* are taken (more or less) straight from this document.
*
* ARPOP_REVREQUEST
*
* arp_sha is the hardware address of the sender of the packet.
* arp_spa is undefined.
* arp_tha is the 'target' hardware address.
* In the case where the sender wishes to determine his own
* protocol address, this, like arp_sha, will be the hardware
* address of the sender.
* arp_tpa is undefined.
*
* ARPOP_REVREPLY
*
* arp_sha is the hardware address of the responder (the sender of the
* reply packet).
* arp_spa is the protocol address of the responder (see the note below).
* arp_tha is the hardware address of the target, and should be the same as
* that which was given in the request.
* arp_tpa is the protocol address of the target, that is, the desired address.
*
* Note that the requirement that arp_spa be filled in with the responder's
* protocol is purely for convenience. For instance, if a system were to use
* both ARP and RARP, then the inclusion of the valid protocol-hardware
* address pair (arp_spa, arp_sha) may eliminate the need for a subsequent
* ARP request.
*/
void
rarp_reply(struct if_info *ii, struct if_addr *ia, struct ether_header *ep,
u_int32_t ipaddr, struct hostent *hp)
{
struct ether_arp *ap = (struct ether_arp *) (ep + 1);
int len, n;
/*
* Poke the kernel arp tables with the ethernet/ip address
* combination given. When processing a reply, we must
* do this so that the booting host (i.e. the guy running
* rarpd), won't try to ARP for the hardware address of the
* guy being booted (he cannot answer the ARP).
*/
if (arptab_set((u_char *)&ap->arp_sha, ipaddr) > 0)
syslog(LOG_ERR, "couldn't update arp table");
/* Build the rarp reply by modifying the rarp request in place. */
ep->ether_type = htons(ETHERTYPE_REVARP);
ap->ea_hdr.ar_hrd = htons(ARPHRD_ETHER);
ap->ea_hdr.ar_pro = htons(ETHERTYPE_IP);
ap->arp_op = htons(ARPOP_REVREPLY);
memcpy((char *) &ep->ether_dhost, (char *) &ap->arp_sha, 6);
memcpy((char *) &ep->ether_shost, (char *) ii->ii_eaddr, 6);
memcpy((char *) &ap->arp_sha, (char *) ii->ii_eaddr, 6);
memcpy((char *) ap->arp_tpa, (char *) &ipaddr, 4);
/* Target hardware is unchanged. */
memcpy((char *) ap->arp_spa, (char *) &ia->ia_ipaddr, 4);
if (lflag) {
struct ether_addr ea;
memcpy(&ea.ether_addr_octet, &ap->arp_sha, 6);
syslog(LOG_INFO, "%s asked; %s replied", hp->h_name,
ether_ntoa(&ea));
}
len = sizeof(*ep) + sizeof(*ap);
n = write(ii->ii_fd, (char *) ep, len);
if (n != len)
warning("write: only %d of %d bytes written", n, len);
}
/*
* Get the netmask of an IP address.
*/
u_int32_t
ipaddrtonetmask(u_int32_t addr)
{
if (IN_CLASSA(addr))
return IN_CLASSA_NET;
if (IN_CLASSB(addr))
return IN_CLASSB_NET;
if (IN_CLASSC(addr))
return IN_CLASSC_NET;
error("unknown IP address class: %08X", addr);
}
void
warning(const char *fmt,...)
{
va_list ap;
if (dflag) {
(void) fprintf(stderr, "rarpd: warning: ");
va_start(ap, fmt);
(void) vfprintf(stderr, fmt, ap);
va_end(ap);
(void) fprintf(stderr, "\n");
}
va_start(ap, fmt);
vsyslog(LOG_ERR, fmt, ap);
va_end(ap);
}
__dead void
error(const char *fmt,...)
{
va_list ap;
if (dflag) {
(void) fprintf(stderr, "rarpd: error: ");
va_start(ap, fmt);
(void) vfprintf(stderr, fmt, ap);
va_end(ap);
(void) fprintf(stderr, "\n");
}
va_start(ap, fmt);
vsyslog(LOG_ERR, fmt, ap);
va_end(ap);
exit(1);
}
void
debug(const char *fmt,...)
{
va_list ap;
if (dflag) {
va_start(ap, fmt);
(void) fprintf(stderr, "rarpd: ");
(void) vfprintf(stderr, fmt, ap);
va_end(ap);
(void) fprintf(stderr, "\n");
}
}