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there and back again, a hobbits tail

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This commit is contained in:
Bjorn Andersson 2006-06-05 18:47:09 +00:00
parent f9381aa723
commit f701f3c6ca
5 changed files with 379 additions and 9 deletions
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20
Makefile
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@ -1,20 +1,26 @@
CC = gcc
OUT = dnstun
OBJS = dnstun.o tun.o dns.o
DNS = dnstun
DNSOBJS = dnstun.o tun.o dns.o
DNSD = dnstund
DNSDOBJS = dnstund.o tun.o dnsd.o
OS = `uname | tr "a-z" "A-Z"`
LDFLAGS =
CFLAGS = -c -g -Wall -D$(OS)
all: stateos $(OUT)
all: stateos $(DNS) $(DNSD)
stateos:
@echo OS is $(OS)
$(OUT): $(OBJS)
$(DNS): $(DNSOBJS)
@echo LD $@
@$(CC) $(OBJS) -o $(OUT) $(LDFLAGS)
@$(CC) $(DNSOBJS) -o $(DNS) $(LDFLAGS)
$(DNSD): $(DNSDOBJS)
@echo LD $@
@$(CC) $(DNSDOBJS) -o $(DNSD) $(LDFLAGS)
.c.o:
@echo CC $<
@ -22,7 +28,5 @@ $(OUT): $(OBJS)
clean:
@echo "Cleaning..."
@rm -f $(OUT) *~ *.o *.core
@rm -f $(DNS) $(DNSD) *~ *.o *.core
run: $(OUT)
./$(OUT)

236
dnsd.c Normal file
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@ -0,0 +1,236 @@
/*
* Copyright (c) 2006 Bjorn Andersson <flex@kryo.se>, Erik Ekman <yarrick@kryo.se>
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <arpa/nameser.h>
#include <netdb.h>
#include <time.h>
#include <err.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <ctype.h>
#include "dns.h"
static int host2dns(const char *, char *, int);
struct sockaddr_in peer;
char topdomain[256];
static int
readname(char *packet, char *dst, char *src)
{
char l;
int len;
int offset;
len = 0;
while(*src) {
l = *src++;
len++;
if(l & 0x80 && l & 0x40) {
offset = ((src[-1] & 0x3f) << 8) | src[0];
readname(packet, dst, packet + offset);
dst += strlen(dst);
break;
}
while(l) {
*dst++ = *src++;
l--;
len++;
}
*dst++ = '.';
}
*dst = '\0';
src++;
len++;
return len;
}
#define READNAME(packet, dst, src) (src) += readname((packet), (dst), (src));
#define READSHORT(dst, src) \
(dst) = ntohs(*(short*)(src)); (src)+=2;
#define READLONG(dst, src) \
(dst) = ntohl(*(long*)(src)); (src)+=4;
#define READDATA(dst, src, len) \
memcpy((dst), (src), (len)); (src)+=(len);
int
open_dnsd(const char *domain)
{
int fd;
int flag;
struct sockaddr_in addr;
bzero(&addr, sizeof(addr));
addr.sin_family = AF_INET;
addr.sin_port = htons(53);
addr.sin_addr.s_addr = htonl(INADDR_ANY);
fd = socket(AF_INET, SOCK_DGRAM, 0);
if(fd < 0) {
warn("socket");
return 0;
}
flag = 1;
#ifdef SO_REUSEPORT
setsockopt(fd, SOL_SOCKET, SO_REUSEPORT, &flag, sizeof(flag));
#endif
setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &flag, sizeof(flag));
if(bind(fd, (struct sockaddr*)&addr, sizeof(addr)) < 0) {
warn("bind");
return 0;
}
printf("Opened UDP socket\n");
return fd;
}
void
close_dnsd(int fd)
{
close(fd);
}
static int
host2dns(const char *host, char *buffer, int size)
{
char *h;
char *p;
char *word;
h = strdup(host);
memset(buffer, 0, size);
p = buffer;
word = strtok(h, ".");
while(word) {
*p++ = (char)strlen(word);
memcpy(p, word, strlen(word));
p += strlen(word);
word = strtok(NULL, ".");
}
*p++ = 0;
free(h);
return p - buffer;
}
static void
dnsd_respond(int fd, struct sockaddr_in from)
{
int len;
int size;
HEADER *header;
char *p;
char buf[1024];
memset(buf, 0, sizeof(buf));
len = 0;
header = (HEADER*)buf;
header->id = 0;
header->qr = 1;
header->opcode = 0;
header->aa = 1;
header->tc = 0;
header->rd = 0;
header->ra = 0;
header->ancount = htons(1);
p = buf + sizeof(HEADER);
p += host2dns("fluff", p, 5);
PUTSHORT(T_PTR, p);
PUTSHORT(C_IN, p);
PUTLONG(htons(3600), p);
size = host2dns("mupp", p+2, 4);
PUTSHORT(size, p);
p += size;
len = p - buf;
printf("%d\n", len);
sendto(fd, buf, len, 0, (struct sockaddr*)&from, sizeof(from));
}
int
dnsd_read(int fd, char *buf, int buflen)
{
int i;
int r;
short type;
short class;
short qdcount;
char *data;
char name[255];
HEADER *header;
socklen_t addrlen;
char packet[64*1024];
struct sockaddr_in from;
addrlen = sizeof(struct sockaddr);
r = recvfrom(fd, packet, sizeof(packet), 0, (struct sockaddr*)&from, &addrlen);
printf("Read %d bytes DNS query from %s\n", r, inet_ntoa(from.sin_addr));
if(r == -1) {
perror("recvfrom");
} else {
header = (HEADER*)packet;
data = packet + sizeof(HEADER);
if(!header->qr) {
qdcount = ntohs(header->qdcount);
for(i=0;i<qdcount;i++) {
bzero(name, sizeof(name));
READNAME(packet, name, data);
READSHORT(type, data);
READSHORT(class, data);
printf("%s %d %d\n", name, type, class);
dnsd_respond(fd, from);
}
}
}
return 0;
}

28
dnsd.h Normal file
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@ -0,0 +1,28 @@
/*
* Copyright (c) 2006 Bjorn Andersson <flex@kryo.se>, Erik Ekman <yarrick@kryo.se>
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
#ifndef _DNSD_H_
#define _DNSD_H_
extern struct sockaddr_in peer;
int open_dnsd(const char *);
void close_dnsd(int);
int dnsd_read(int, char *, int);
#endif /* _DNSD_H_ */

102
dnstund.c Normal file
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@ -0,0 +1,102 @@
/*
* Copyright (c) 2006 Bjorn Andersson <flex@kryo.se>, Erik Ekman <yarrick@kryo.se>
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
#include <stdio.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <signal.h>
#include <unistd.h>
#include <sys/types.h>
#include <err.h>
#include "tun.h"
#include "dns.h"
#include "dnsd.h"
#define MAX(a,b) ((a)>(b)?(a):(b))
int running = 1;
static void
sigint(int sig) {
running = 0;
}
static int
tunnel(int tun_fd, int dns_fd)
{
int i;
int read;
fd_set fds;
char buf[1024];
struct timeval tv;
while (running) {
tv.tv_sec = 1;
tv.tv_usec = 0;
FD_ZERO(&fds);
FD_SET(tun_fd, &fds);
FD_SET(dns_fd, &fds);
i = select(MAX(tun_fd, dns_fd) + 1, &fds, NULL, NULL, &tv);
if(i < 0) {
if (running) {
warn("select");
}
return 1;
}
if(i != 0) {
if(FD_ISSET(tun_fd, &fds)) {
}
if(FD_ISSET(dns_fd, &fds)) {
read = dnsd_read(dns_fd, buf, sizeof(buf));
}
}
}
return 0;
}
int
main(int argc, char **argv)
{
int tun_fd;
int dnsd_fd;
if (argc != 2) {
printf("Usage: %s topdomain\n", argv[0]);
exit(2);
}
tun_fd = open_tun();
dnsd_fd = open_dnsd(argv[1]);
signal(SIGINT, sigint);
tunnel(tun_fd, dnsd_fd);
printf("Closing tunnel\n");
close_dnsd(dnsd_fd);
close_tun(tun_fd);
return 0;
}