1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
|
/* Copyright (c) 2002,2003 Sam Trenholme
*
* TERMS
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* This software is provided 'as is' with no guarantees of correctness or
* fitness for purpose.
*/
/* This simply listens on port 53 and does nothing with what
it receives, simulating a dead host.
*/
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <time.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include "../MaraDns.h"
int harderror(char *msg) {
printf("Hard error: %s\n",msg);
exit(1);
}
main(int argc, char **argv) {
char *bind_address;
struct sockaddr_in dns_udp, client;
int len_inet; /* Length */
int s; /* Socket */
int q; /* Used for binding, etc */
js_string *indata; /* Incoming data */
js_string *outdata; /* Incoming data */
js_file desc;
q_header header; /* header data */
q_question question;
int counter,place,count;
/* Determine what IP address to bind to */
if(argc == 2)
bind_address = argv[1];
else
bind_address = "127.0.0.3";
if((indata = js_create(512,1)) == 0)
harderror("js_create with indata");
if((outdata = js_create(512,1)) == 0)
harderror("js_create with indata");
if((question.qname = js_create(512,1)) == 0)
harderror("js_create with qname");
/* Create a UDP socket */
if((s = socket(AF_INET,SOCK_DGRAM,0)) == -1)
harderror("Socket");
/* Create a socket address to use with bind() */
memset(&dns_udp,0,sizeof(dns_udp));
dns_udp.sin_family = AF_INET;
dns_udp.sin_port = htons(53);
if((dns_udp.sin_addr.s_addr = inet_addr(bind_address)) == INADDR_NONE)
harderror("Malformed IP");
len_inet = sizeof(dns_udp);
/* Bind to the socket. Note that we have to be root to do this */
if(bind(s,(struct sockaddr *)&dns_udp,len_inet) == -1)
harderror("Binding problem--must be root");
/* Drop elevated privileges */
if(setuid(99) != 0)
harderror("setuid failed");
/* Make sure they are dropped */
if(setuid(0) == 0)
harderror("we still have root privileges!");
/* loop to handle requests */
for(;;) {
recvfrom(s,indata->string,512,0,(struct sockaddr *)&client,&len_inet);
}
}
|
