C语言实现Linux网络嗅探器
0x01 实验简介
网络嗅探器是拦截通过网络接口流入和流出的数据的程序。所以，如果你正在浏览的互联网，嗅探器以数据包的形式抓到它并且显示。在本实验中，我们用 C 语言实现了一个网络嗅探器。
0x02程序框架和功能描述
本程序使用c语言编程，实现linux环境下网络嗅探的功能，并实现对接收到的UDP数据报进行解析。
0x03程序代码
sniffer.h
#ifndef __SNIFFER_H__
#define __SNIFFER_H__
typedef struct s_protocol
{
int tcp;
int udp;
int icmp;
int igmp;
int others;
int total;
} t_protocol;
typedef struct s_sniffer
{
FILE *logfile;
t_protocol *prot;
} t_sniffer;
void ProcessPacket(unsigned char*, int, t_sniffer *);
void print_ip_header(unsigned char* , int, t_sniffer *);
void print_tcp_packet(unsigned char* , int, t_sniffer *);
void print_udp_packet(unsigned char * , int, t_sniffer *);
void print_icmp_packet(unsigned char* , int, t_sniffer *);
void PrintData (unsigned char* , int, t_sniffer *);
void display_time_and_date();
void getting_started();
void signal_white_now(int);
#endif
tools.h
#ifndef __COLOR_H__
#define __COLOR_H__
#include <stdio.h>
#define CLEARSCREEN() printf(" 33[H 33[2J")
#define INITCOLOR(color) printf(" 33[%sm", color)
#define RED_COLOR "31"
#define GREEN_COLOR "32"
#define YELLOW_COLOR "33"
#define BLUE_COLOR "34"
#define ZERO_COLOR "0"
#endif
tools.c
#include <signal.h>
#include <stdio.h>
/* 信号处理函数 */
void signal_white_now(int signum)
{
printf("Bye Bye !
");
}
show_data.c
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <netinet/ip_icmp.h>
#include <netinet/udp.h>
#include <netinet/tcp.h>
#include <netinet/ip.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include "sniffer.h"
#include "tools.h"
/* 写 IP 头部到日志文件 */
void print_ip_header(unsigned char *buf, int size, t_sniffer *sniffer)
{
unsigned short iphdrlen;
struct iphdr *iph;
struct sockaddr_in source;
struct sockaddr_in dest;
iph = (struct iphdr *)buf;
iphdrlen = iph->ihl*4;
(void)iphdrlen;
(void)size;
memset(&source, 0, sizeof(source));
source.sin_addr.s_addr = iph->saddr;
memset(&dest, 0, sizeof(dest));
dest.sin_addr.s_addr = iph->daddr;
fprintf(sniffer->logfile,"
");
fprintf(sniffer->logfile,"IP Header
");
fprintf(sniffer->logfile," |-IP Version : %d
",(unsigned int)iph->version);
fprintf(sniffer->logfile," |-IP Header Length : %d DWORDS or %d Bytes
",(unsigned int)iph->ihl,((unsigned int)(iph->ihl))*4);
fprintf(sniffer->logfile," |-Type Of Service : %d
",(unsigned int)iph->tos);
fprintf(sniffer->logfile," |-IP Total Length : %d Bytes(size of Packet)
",ntohs(iph->tot_len));
fprintf(sniffer->logfile," |-Identification : %d
",ntohs(iph->id));
fprintf(sniffer->logfile," |-TTL : %d
",(unsigned int)iph->ttl);
fprintf(sniffer->logfile," |-Protocol : %d
",(unsigned int)iph->protocol);
fprintf(sniffer->logfile," |-Checksum : %d
",ntohs(iph->check));
fprintf(sniffer->logfile," |-Source IP : %s
",inet_ntoa(source.sin_addr));
fprintf(sniffer->logfile," |-Destination IP : %s
",inet_ntoa(dest.sin_addr));
}
/* 写 TCP 数据包到日志文件 */
void print_tcp_packet(unsigned char *buf, int size, t_sniffer *sniffer)
{
unsigned short iphdrlen;
struct iphdr *iph;
struct tcphdr *tcph;
iph = (struct iphdr *)buf;
iphdrlen = iph->ihl * 4;
tcph = (struct tcphdr*)(buf + iphdrlen);
print_ip_header(buf, size, sniffer);
/* 把 tcp 头信息写入日志文件中 */
fprintf(sniffer->logfile,"
");
fprintf(sniffer->logfile,"TCP Header
");
fprintf(sniffer->logfile," |-Source Port : %u
",ntohs(tcph->source));
fprintf(sniffer->logfile," |-Destination Port : %u
",ntohs(tcph->dest));
fprintf(sniffer->logfile," |-Sequence Number : %u
",ntohl(tcph->seq));
fprintf(sniffer->logfile," |-Acknowledge Number : %u
",ntohl(tcph->ack_seq));
fprintf(sniffer->logfile," |-Header Length : %d DWORDS or %d BYTES
" ,(unsigned int)tcph->doff,(unsigned int)tcph->doff*4);
fprintf(sniffer->logfile," |-Urgent Flag : %d
",(unsigned int)tcph->urg);
fprintf(sniffer->logfile," |-Acknowledgement Flag : %d
",(unsigned int)tcph->ack);
fprintf(sniffer->logfile," |-Push Flag : %d
",(unsigned int)tcph->psh);
fprintf(sniffer->logfile," |-Reset Flag : %d
",(unsigned int)tcph->rst);
fprintf(sniffer->logfile," |-Synchronise Flag : %d
",(unsigned int)tcph->syn);
fprintf(sniffer->logfile," |-Finish Flag : %d
",(unsigned int)tcph->fin);
fprintf(sniffer->logfile," |-Window : %d
",ntohs(tcph->window));
fprintf(sniffer->logfile," |-Checksum : %d
",ntohs(tcph->check));
fprintf(sniffer->logfile," |-Urgent Pointer : %d
",tcph->urg_ptr);
fprintf(sniffer->logfile,"
");
fprintf(sniffer->logfile," DATA Dump ");
fprintf(sniffer->logfile,"
");
fprintf(sniffer->logfile,"IP Header
");
PrintData(buf, iphdrlen, sniffer);
fprintf(sniffer->logfile,"TCP Header
");
PrintData(buf+iphdrlen, tcph->doff*4, sniffer);
fprintf(sniffer->logfile,"Data Payload
");
/* 把用户数据写入日志文件 */
PrintData(buf + iphdrlen + tcph->doff*4,
(size - tcph->doff*4-iph->ihl*4),
sniffer );
fprintf(sniffer->logfile,"
###########################################################");
}
/* 写 UDP 数据包到日志文件 */
void print_udp_packet(unsigned char *buf , int size, t_sniffer *sniffer)
{
unsigned short iphdrlen;
struct iphdr *iph;
struct udphdr *udph;
iph = (struct iphdr *)buf;
iphdrlen = iph->ihl*4;
udph = (struct udphdr*)(buf + iphdrlen);
fprintf(sniffer->logfile,"
***********************UDP Packet*************************
");
print_ip_header(buf, size, sniffer);
/* 把 udp 头信息写入日志文件中 */
fprintf(sniffer->logfile,"
UDP Header
");
fprintf(sniffer->logfile," |-Source Port : %d
" , ntohs(udph->source));
fprintf(sniffer->logfile," |-Destination Port : %d
" , ntohs(udph->dest));
fprintf(sniffer->logfile," |-UDP Length : %d
" , ntohs(udph->len));
fprintf(sniffer->logfile," |-UDP Checksum : %d
" , ntohs(udph->check));
fprintf(sniffer->logfile,"
");
fprintf(sniffer->logfile,"IP Header
");
PrintData(buf , iphdrlen, sniffer);
fprintf(sniffer->logfile,"UDP Header
");
PrintData(buf+iphdrlen, sizeof(udph), sniffer);
fprintf(sniffer->logfile,"Data Payload
");
/* 把用户数据写入日志文件 */
PrintData(buf + iphdrlen + sizeof udph,
(size - sizeof udph - iph->ihl * 4),
sniffer);
fprintf(sniffer->logfile,"
###########################################################");
}
/* 写 ICMP 数据包到日志文件 */
void print_icmp_packet(unsigned char *buf , int size, t_sniffer *sniffer)
{
unsigned short iphdrlen;
struct iphdr *iph;
struct icmphdr *icmph;
iph = (struct iphdr *)buf;
iphdrlen = iph->ihl * 4;
icmph = (struct icmphdr *)(buf + iphdrlen);
/* 把 icmp 头信息写入日志文件中 */
fprintf(sniffer->logfile,"
***********************ICMP Packet*************************
");
print_ip_header(buf , size, sniffer);
fprintf(sniffer->logfile,"
");
fprintf(sniffer->logfile,"ICMP Header
");
fprintf(sniffer->logfile," |-Type : %d",(unsigned int)(icmph->type));
if((unsigned int)(icmph->type) == 11)
fprintf(sniffer->logfile," (TTL Expired)
");
else if((unsigned int)(icmph->type) == ICMP_ECHOREPLY)
fprintf(sniffer->logfile," (ICMP Echo Reply)
");
fprintf(sniffer->logfile," |-Code : %d
",(unsigned int)(icmph->code));
fprintf(sniffer->logfile," |-Checksum : %d
",ntohs(icmph->checksum));
fprintf(sniffer->logfile,"
");
fprintf(sniffer->logfile,"IP Header
");
PrintData(buf, iphdrlen, sniffer);
fprintf(sniffer->logfile,"UDP Header
");
PrintData(buf + iphdrlen , sizeof(icmph), sniffer);
fprintf(sniffer->logfile,"Data Payload
");
/* 最后将用户数据写入日志文件中 */
PrintData(buf + iphdrlen + sizeof(icmph),
(size - sizeof(icmph) - iph->ihl * 4),
sniffer);
fprintf(sniffer->logfile,"
###########################################################");
}
/* 写用户数据到日志文件 */
void PrintData(unsigned char *buf, int size, t_sniffer *sniffer)
{
int i;
for(i = 0 ; i < size ; i++)
{
if(i % 16 == 0)
fprintf(sniffer->logfile, "
");
fprintf(sniffer->logfile, " %02X",(unsigned int)buf[i]);
if( i == size - 1)
fprintf(sniffer->logfile, "
");
}
}
main.c
#include <signal.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <netinet/ip.h>
#include <sys/socket.h>
#include <sys/select.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/time.h>
#include <errno.h>
#include "sniffer.h"
#include "tools.h"
#define ETH_P_IP 0x0800
int exec_cmd(char *buffer, int len)
{
if (strncmp(buffer, "quit", 4) == 0)
return (1);
return (0);
}
int command_interpreter(int sd)
{
int len;
char buf[512];
len = read(0, buf, 512);
if (len > 0)
{
if (exec_cmd(buf, len) == 1)
return (1);
}
return (0);
}
void display_time_and_date()
{
INITCOLOR(RED_COLOR);
printf("[%s]", __DATE__); /* 打印日期 */
INITCOLOR(GREEN_COLOR);
printf("[%s] ", __TIME__); /* 打印时间 */
INITCOLOR(ZERO_COLOR);
}
void getting_started()
{
CLEARSCREEN(); /* 清空屏幕 */
display_time_and_date();
printf("Getting started of Network sniffer
");
}
/* 主函数入口 */
int main()
{
/* 声明部分 */
int sd;
int res;
int saddr_size;
int data_size;
struct sockaddr saddr;
unsigned char *buffer; /* 保存数据包的数据 */
t_sniffer sniffer; /* 保存数据包的类型和日志文件等信息 */
fd_set fd_read;
buffer = malloc(sizeof(unsigned char *) * 65536);
/* 以可写的方式在当前文件夹中创建日志文件 */
sniffer.logfile = fopen("log.txt", "w");
fprintf(sniffer.logfile,"***LOGFILE(%s - %s)***
", __DATE__, __TIME__);
if (sniffer.logfile == NULL)
{
perror("fopen(): ");
return (EXIT_FAILURE);
}
sniffer.prot = malloc(sizeof(t_protocol *));
/* 创建原始套接字，ETH_P_ALL 表示侦听负载为 IP 数据报的以太网帧 */
sd = socket(PF_PACKET, SOCK_RAW, htons(ETH_P_IP));
if (sd < 0)
{
perror("socket(): ");
return (EXIT_FAILURE);
}
getting_started();
signal(SIGINT, &signal_white_now);
signal(SIGQUIT, &signal_white_now);
/* 循环侦听以太网帧，并调用 ProcessPacket 函数解析 */
while (1)
{
FD_ZERO(&fd_read);
FD_SET(0, &fd_read);
FD_SET(sd, &fd_read);
/* 多路复用检测可读的套接字和标准输入 */
res = select(sd + 1, &fd_read, NULL, NULL, NULL);
if (res < 0)
{
close(sd);
if (errno != EINTR)
perror("select() ");
return (EXIT_FAILURE);
}
else
{
/* 如果是标准输入可读，进入命令行处理程序 command_interpreter，暂时只支持 'quit' 命令 */
if (FD_ISSET(0, &fd_read))
{
if (command_interpreter(sd) == 1)
break;
}
/* 如果是套接字可读，则读取以太网数据帧的内容，并调用 ProcessPacket 函数解析出数据包的类型 */
else if (FD_ISSET(sd, &fd_read))
{
/* 读取以太网数据帧的内容 */
saddr_size = sizeof(saddr);
data_size = recvfrom(sd, buffer, 65536, 0, &saddr,(socklen_t*)&saddr_size); /* 读取以太网数据帧的内容 */
if (data_size <= 0)
{
close(sd);
perror("recvfrom(): ");
return (EXIT_FAILURE);
}
ProcessPacket(buffer, data_size, &sniffer); /* 调用 ProcessPacket 函数解析出数据包的类型 */
}
}
}
close(sd);
return (EXIT_SUCCESS);
}
void ProcessPacket(unsigned char* buffer, int size, t_sniffer *sniffer)
{
buffer = buffer + 6 + 6 + 2; /* 根据太网帧结构，前 6B 是目的 MAC 地址，接下来的是源 MAC 地址，接下来 2B 是帧长度，其余的是负载（上层的 IP 数据报） */
struct iphdr *iph = (struct iphdr*)buffer;
++sniffer->prot->total; /* 数据包总数加 1 */
/* 根据 TCP/IP 协议规定的 IP 数据报头部的 protocol 字段的值，判断上层的数据包类型 */
switch (iph->protocol)
{
/* 1 表示 icmp 协议 */
case 1:
++sniffer->prot->icmp;
print_icmp_packet(buffer, size, sniffer);
break;
/* 2 表示 igmp 协议 */
case 2:
++sniffer->prot->igmp;
break;
/* 6 表示 tcp 协议 */
case 6:
++sniffer->prot->tcp;
print_tcp_packet(buffer , size, sniffer);
break;
/* 17 表示 udp 协议 */
case 17:
++sniffer->prot->udp;
print_udp_packet(buffer , size, sniffer);
break;
default:
++sniffer->prot->others;
break;
}
display_time_and_date(); /* 显示时间 */
/* 打印 sniffer 中的信息 */
printf("TCP : %d UDP : %d ICMP : %d IGMP : %d Others : %d Total : %d
",
sniffer->prot->tcp, sniffer->prot->udp,
sniffer->prot->icmp, sniffer->prot->igmp,
sniffer->prot->others, sniffer->prot->total);
}
0x04程序运行
本程序运行界面如下：
实现的功能之一就是解析UDP数据报，其扫描解析结果存放在log.txt中。这里从log.txt中以一个UDP数据包的解析为例
***LOGFILE(Dec 14 2017 - 21:41:38)***
***********************UDP Packet*************************
IP Header
|-IP Version : 4
|-IP Header Length : 5 DWORDS or 20 Bytes
|-Type Of Service : 0
|-IP Total Length : 213 Bytes(size of Packet)
|-Identification : 6639
|-TTL : 64
|-Protocol : 17
|-Checksum : 31927
|-Source IP : 172.16.69.82
|-Destination IP : 172.16.69.255
UDP Header
|-Source Port : 138
|-Destination Port : 138
|-UDP Length : 193
|-UDP Checksum : 26258
IP Header
保护隐私，这部分我删除了
AC 10 45 FF
UDP Header
保护隐私，这部分我删除了
Data Payload
保护隐私，这部分我删除了
###########################################################
0x05附
我认为本实验的亮点在于使用脚本控制，有必要好好学习下脚本编程
launcher.sh
#!/bin/sh
sigint()
{
printf '
QUIT !
'
exit 1
}
main()
{
clear
printf " Welcome to Sniffer Project r
"
while [ 1 ]; do
printf "Select option:
"
printf "1 : Build Project
"
printf "2 : Launch Project
"
printf "3 : Remove Object files
"
printf "4 : Rebuild
"
printf "0 : Exit
"
printf "
You choose: "
read option
if [ $option = 0 ]
then
exit
fi
if [ $option -ge 1 ] && [ $option -le 4 ]
then
if [ $option = 1 ]
then
make "network_sniffer"
fi
if [ $option = 2 ]
then
"./network_sniffer"
fi
if [ $option = 3 ]
then
make clean
fi
if [ $option = 4 ]
then
make re
fi
else
printf "This option does not exist
"
fi
done
}
trap 'sigint' 2
main