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/* This file is part of the KDE Libraries
Copyright (c) 2001 Malte Starostik <malte@kde.org>
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Library General Public
License version 2 as published by the Free Software Foundation.
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
Library General Public License for more details.
You should have received a copy of the GNU Library General Public License
along with this library; see the file COPYING.LIB. If not, write to
the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
Boston, MA 02110-1301, USA.
*/
#include <config.h>
#include <sys/types.h>
#include <grp.h>
#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <sys/time.h>
#include <sys/socket.h>
#include <time.h>
#include <netdb.h>
#include <netinet/in.h>
#include "dhcp.h"
#ifndef INADDR_NONE /* some OSes don't define this */
#define INADDR_NONE -1
#endif
int set_gid(gid_t);
int set_uid(uid_t);
int get_port(const char *);
int init_socket(void);
uint32_t send_request(int);
void get_reply(int, uint32_t);
int set_gid(gid_t gid)
{
#ifdef HAVE_SHORTSETGROUPS
short x[2];
x[0] = gid;
x[1] = 73; /* catch errors */
if (setgroups(1, x) == -1)
return -1;
#else
if (setgroups(1, &gid) == -1)
return -1;
#endif
return setgid(gid); /* _should_ be redundant, but on some systems it isn't */
}
int set_uid(uid_t uid)
{
return setuid(uid);
}
/* All functions below do an exit(1) on the slightest error */
/* Returns the UDP port number for the given service name */
int get_port(const char *service)
{
struct servent *serv = getservbyname(service, "udp");
if (serv == NULL)
exit(1);
return serv->s_port;
}
/* Opens the UDP socket, binds to the bootpc port and drops root privileges */
int init_socket()
{
struct sockaddr_in addr;
struct protoent *proto;
int sock;
int bcast = 1;
memset(&addr, 0, sizeof(addr));
addr.sin_family = AF_INET;
addr.sin_addr.s_addr = INADDR_ANY;
addr.sin_port = get_port("bootpc");
if ((proto = getprotobyname("udp")) == NULL ||
(sock = socket(AF_INET, SOCK_DGRAM, proto->p_proto)) == -1)
exit(1);
if (setsockopt(sock, SOL_SOCKET, SO_BROADCAST, &bcast, sizeof(bcast)) == -1 ||
setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, &bcast, sizeof(bcast)) == -1 ||
bind(sock, (struct sockaddr *)&addr, sizeof(addr)) == -1)
exit(1);
if (set_gid(getgid()) != 0 || /* we don't need it anymore */
set_uid(getuid()) != 0)
exit(1);
return sock;
}
/* Fills the DHCPINFORM request packet, returns the transaction id */
uint32_t send_request(int sock)
{
char hostname[256];
struct hostent *hent;
struct sockaddr_in addr;
struct dhcp_msg request;
uint8_t *offs = request.options;
hostname[0] = '\0';
hostname[255] = '\0';
if (gethostname(hostname, 255) == -1 ||
strlen(hostname) == 0 ||
(hent = gethostbyname(hostname)) == NULL)
exit(1);
memset(&addr, 0, sizeof(addr));
addr.sin_family = AF_INET;
addr.sin_addr.s_addr = INADDR_NONE;
addr.sin_port = get_port("bootps");
memset(&request, 0, sizeof(request));
request.op = DHCP_BOOTREQUEST;
srand(time(NULL));
request.xid = rand();
request.ciaddr = *(uint32_t*)*hent->h_addr_list;
*offs++ = DHCP_MAGIC1;
*offs++ = DHCP_MAGIC2;
*offs++ = DHCP_MAGIC3;
*offs++ = DHCP_MAGIC4;
*offs++ = DHCP_OPT_MSGTYPE;
*offs++ = 1; /* length */
*offs++ = DHCP_INFORM;
*offs++ = DHCP_OPT_PARAMREQ;
*offs++ = 1; /* length */
*offs++ = DHCP_OPT_WPAD;
*offs++ = DHCP_OPT_END;
if (sendto(sock, &request, sizeof(request), 0,
(struct sockaddr *)&addr, sizeof(addr)) != sizeof(request))
exit(1);
return request.xid;
}
/* Reads the reply from the socket, checks it and outputs the URL to STDOUT */
void get_reply(int sock, uint32_t xid)
{
struct dhcp_msg reply;
int len;
char wpad[DHCP_OPT_LEN + 1];
uint8_t wpad_len;
uint8_t *offs = reply.options;
uint8_t *end;
if ((len = recvfrom(sock, &reply, sizeof(reply), 0, NULL, NULL)) <= 0)
exit(1);
end = (uint8_t *)&reply + len;
if (end < offs + 4 ||
end > &reply.options[DHCP_OPT_LEN] ||
reply.op != DHCP_BOOTREPLY ||
reply.xid != xid ||
*offs++ != DHCP_MAGIC1 ||
*offs++ != DHCP_MAGIC2 ||
*offs++ != DHCP_MAGIC3 ||
*offs++ != DHCP_MAGIC4)
exit(1);
for ( ; offs < end - 1; offs += *offs+1)
{
switch (*offs++)
{
case DHCP_OPT_END:
exit(1);
case DHCP_OPT_MSGTYPE:
if (*offs != 1 || (offs >= end - 1) || *(offs + 1) != DHCP_ACK)
exit(1);
break;
case DHCP_OPT_WPAD:
memset(wpad, 0, sizeof(wpad));
wpad_len = *offs++;
if (offs >= end)
exit(1);
if (wpad_len > end - offs)
wpad_len = end - offs;
strncpy(wpad, (char *)offs, wpad_len);
wpad[wpad_len] = 0;
printf("%s\n", wpad);
close(sock);
exit(0);
}
}
exit(1);
}
int main()
{
fd_set rfds;
struct timeval tv;
int sock;
uint32_t xid;
sock = init_socket();
xid = send_request(sock);
FD_ZERO(&rfds);
FD_SET(sock, &rfds);
tv.tv_sec = 5;
tv.tv_usec = 0;
if (select(sock + 1, &rfds, NULL, NULL, &tv) == 1 && FD_ISSET(sock, &rfds))
get_reply(sock, xid);
close(sock);
exit(1);
}
/* vim: ts=4 sw=4 noet
*/
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