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sniffer.c
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#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <linux/if_ether.h>
//#include <linux/in.h>
#include <sys/ioctl.h>
#include <net/if.h>
#include <netinet/in.h>
unsigned char buffer[2048];
void num2p(int num, char *prot){//TCP和UDP协议端口号转协议类型
switch (num)
{
case 7:
strcpy(prot,"echo");
break;
case 15:
strcpy(prot,"netstat");
break;
case 21:
strcpy(prot,"ftp");
break;
case 22:
strcpy(prot,"ssh");
break;
case 23:
strcpy(prot,"telnet");
break;
case 25:
strcpy(prot,"smtp");
break;
case 37:
strcpy(prot,"time");
break;
case 53:
strcpy(prot,"dns");
break;
case 57:
strcpy(prot,"mtp");
break;
case 69:
strcpy(prot,"tftp");
break;
case 80:
strcpy(prot,"http");
break;
case 110:
strcpy(prot,"pop3");
break;
case 179:
strcpy(prot,"bgp");
break;
case 443:
strcpy(prot,"https");
break;
case 1521:
strcpy(prot,"oracle");
break;
case 1900:
strcpy(prot,"ssdp");
break;
case 3306:
strcpy(prot,"mysql");
break;
default:
strcpy(prot,"");
break;
}
}
void analyse_udp(unsigned char *udphead){//UDP协议分析函数
printf("UDP:\n");
int sport=(udphead[0]<<8)+udphead[1];
int dport=(udphead[2]<<8)+udphead[3];
printf(" 源端口: %d ",sport);
char udp_sprot[10]={};
char udp_dprot[10]={};
num2p(sport,udp_sprot);
if(strlen(udp_sprot)) printf("(%s) ",udp_sprot);
printf(", ");
printf("目的端口: %d ",dport);
num2p(dport,udp_dprot);
if(strlen(udp_dprot)) printf("(%s) ",udp_dprot);
printf("\n");
}
void analyse_tcp(unsigned char *tcphead){//TCP协议分析函数
printf("TCP:\n");
int sport=(tcphead[0]<<8)+tcphead[1];
int dport=(tcphead[2]<<8)+tcphead[3];
printf(" 源端口: %d ",sport);
char tcp_sprot[10]={};
char tcp_dprot[10]={};
num2p(sport,tcp_sprot);
if(strlen(tcp_sprot)) printf("(%s) ",tcp_sprot);
printf(", ");
printf("目的端口: %d ",dport);
num2p(dport,tcp_dprot);
if(strlen(tcp_dprot)) printf("(%s) ",tcp_dprot);
printf("\n");
int urg,ack,psh,rst,syn,fin;
int flag=tcphead[13] % 0b1000000;
//获取标志位，URG ACK PSH RST SYN FIN
urg=flag/0b100000;flag=flag%0b100000;
ack=flag/0b10000 ;flag=flag%0b10000 ;
psh=flag/0b1000 ;flag=flag%0b1000 ;
rst=flag/0b100 ;flag=flag%0b100 ;
syn=flag/0b10 ;flag=flag%0b10 ;
fin=flag;
printf(" 标志位: ");
if(urg) printf("URG ");
if(ack) printf("ACK ");
if(psh) printf("PSH ");
if(rst) printf("RST ");
if(syn) printf("SYN ");
if(fin) printf("FIN ");
printf("\n");
//获取序号和确认号
unsigned long SEQ=0,ACK=0;
int i;
for(i=0;i<3;i++){
SEQ+=tcphead[i+4];
SEQ=SEQ<<8;
ACK+=tcphead[i+8];
ACK=ACK<<8;
}
SEQ+=tcphead[i+4];
ACK+=tcphead[i+8];
printf(" seq: %lu ",SEQ);
if(ack) printf(", ack: %lu \n",ACK);
else printf("\n");
}
void analyse_icmp(unsigned char *icmphead){//ICMP协议分析函数
printf("ICMP: \n");
unsigned int type,code;
type = icmphead[0];//类型
code = icmphead[1];//代码
printf(" 类型: %d ",type);
if(type == 8){
printf("(Echo (ping) 请求) , 代码: %d \n",code);
}else if(type == 0){
printf("(Echo (ping) 响应) , 代码: %d \n",code);
}else if(type == 3){
printf("(目标不可达) , 代码: %d ",code);
if(code == 0){
printf("(网络不可达) \n");
}else if(code == 1){
printf("(主机不可达) \n");
}else if(code == 2){
printf("(协议不可达) \n");
}else if(code == 3){
printf("(端口不可达) \n");
}else{
printf("\n");
}
}else if(type == 11){
printf("(TTL超时) , 代码: %d \n",code);
}else{
printf(", 代码: %d \n",code);
}
}
void analyse_igmp(unsigned char *igmphead){//IGMP协议分析函数
printf("IGMP: \n");
}
void analyse_ip(unsigned char *iphead){//IP协议分析函数
if(iphead[0] / 0x10 == 4){//IPv4，IP版本号
int lenth = (iphead[0] % 0x10)*4;//首部长度
printf("IPv4: \n");
printf(" 源IP: %d.%d.%d.%d , ",iphead[12],iphead[13],iphead[14],iphead[15]);
printf("目的IP: %d.%d.%d.%d \n",iphead[16],iphead[17],iphead[18],iphead[19]);
printf(" TTL: %d , 首部长度: %dByte \n",iphead[8],lenth);
//根据协议id调用内层协议分析函数
if(iphead[9]==6) analyse_tcp(iphead+lenth);
else if(iphead[9]==17) analyse_udp(iphead+lenth);
else if(iphead[9]==1) analyse_icmp(iphead+lenth);
else if(iphead[9]==2) analyse_igmp(iphead+lenth);
else printf(" 协议id: %d\n",iphead[9]);
}else{
printf(" IP版本: %d\n",iphead[0] / 0x10);
return ;
}
}
void analyse_arp(unsigned char *arphead){//ARP协议分析函数
printf("ARP: \n");
unsigned int opcode = (arphead[6]<<8)+arphead[7];//操作码
printf(" 操作类型: %d ",opcode);
if(opcode == 1){
printf("(ARP请求) \n");
printf(" 描述: Who has %d.%d.%d.%d? Tell %d.%d.%d.%d\n",
arphead[24],arphead[25],arphead[26],arphead[27],
arphead[14],arphead[15],arphead[16],arphead[17]
);
}else if(opcode == 2){
printf("(ARP应答) \n");
printf(" 描述: %d.%d.%d.%d is at %02x:%02x:%02x:%02x:%02x:%02x\n",
arphead[14],arphead[15],arphead[16],arphead[17],
arphead[8],arphead[9],arphead[10],arphead[11],arphead[12],arphead[13]
);
}else{
printf("\n");
}
}
void analyse_eth(unsigned char *ethhead){//以太网帧协议分析函数
printf("Ethernet:\n");
printf(" 源MAC地址: %02x:%02x:%02x:%02x:%02x:%02x , ",ethhead[6],ethhead[7],ethhead[8],ethhead[9],ethhead[10],ethhead[11]);
printf("目的MAC地址: %02x:%02x:%02x:%02x:%02x:%02x\n",ethhead[0],ethhead[1],ethhead[2],ethhead[3],ethhead[4],ethhead[5]);
int eth_type = (ethhead[12]<<8)+ethhead[13];//下层协议类型
printf(" 类型: 0x%04x\n",eth_type);
if(eth_type == 0x0800)//IP协议
analyse_ip(ethhead+14);
else if(eth_type == 0x0806)//ARP协议
analyse_arp(ethhead+14);
}
int main(int argc, char **argv){
int sock,n;
struct ip *ip;
struct ifreq ethreq;
int no=0;
//设置原始套接字方式为接收所有数据包
if((sock = socket(PF_PACKET, SOCK_RAW, htons(ETH_P_ALL)))<0){
perror("原始套接字建立失败\n");
exit(1);
}
//设置网卡工作方式为混杂模式
strncpy(ethreq.ifr_name,"ens160",IFNAMSIZ);
if(ioctl(sock,SIOCGIFFLAGS,ðreq)==-1){
perror("设置混杂工作模式失败\n");
close(sock);
exit(1);
}
ethreq.ifr_flags|=IFF_PROMISC;
if(ioctl(sock,SIOCSIFFLAGS,ðreq)==-1){
perror("设置混杂工作模式失败\n");
close(sock);
exit(1);
}
//开始捕获数据并进行简单分析
char ch;
char proto[6]={},
saddr[20]={},
daddr[20]={},
address[20]={};
int addrnum = 0;
int slen = 0;
while((ch = getopt(argc, argv, "p:s:d:h")) != -1){//参数捕获
switch (ch) {
case 'p':
slen = strlen(optarg);
if(slen > 5){
fprintf(stdout, "协议类型错误\n");
return -1;
}
memcpy(proto, optarg, slen);
proto[slen] = '\0';
break;
case 's':
slen = strlen(optarg);
if(slen > 15 || slen < 7){
fprintf(stdout, "源IP地址格式错误\n");
return -1;
}
memcpy(saddr, optarg, slen);
saddr[slen] = '\0';
break;
case 'd':
slen = strlen(optarg);
if(slen > 15 || slen < 7){
fprintf(stdout, "目标IP地址格式错误\n");
return -1;
}
memcpy(daddr, optarg, slen);
saddr[slen] = '\0';
break;
case 'h':
fprintf(stdout, "usage: snffer [-p 协议] [-s 源IP地址] [-d 目标IP地址]\n"
" -p 协议[tcp/udp/icmp/igmp/arp]\n"
" -s 源IP地址 address\n"
" -d 目标IP地址 address\n");
exit(0);
case '?':
fprintf(stdout, "无法识别参数: %c\n", ch);
exit(-1);
}
}
while(1){
n = recvfrom(sock,buffer,2048,0,NULL,NULL);
if(strlen(proto)){
if(strcmp(proto, "tcp\0")==0){//根据协议过滤
if(buffer[23] != 6)
continue;
else
goto addr;
}else if(strcmp(proto, "udp\0")==0){
if(buffer[23] != 17)
continue;
else
goto addr;
}else if(strcmp(proto, "icmp\0")==0){
if(buffer[23] != 1)
continue;
else
goto addr;
}else if(strcmp(proto, "igmp\0")==0){
if(buffer[23] != 2)
continue;
else
goto addr;
}else if(strcmp(proto, "arp\0")==0){
if(((buffer[12]<<8)+buffer[13]) != 0x0806)
continue;
else
goto start;
}
}
addr:
if(strlen(saddr)){//根据源地址过滤
if(buffer[14] / 0x10 != 4)
continue;
sprintf(address,"%d.%d.%d.%d",(int)buffer[26],(int)buffer[27],(int)buffer[28],(int)buffer[29]);
if(strcmp(address, saddr) != 0)
continue;
}
if(strlen(daddr)){//根据目标地址过滤
if(buffer[14] / 0x10 != 4)
continue;
sprintf(address,"%d.%d.%d.%d",buffer[30],buffer[31],buffer[32],buffer[33]);
if(strcmp(address, saddr) != 0)
continue;
}
start:
no++;
printf("\n\n---- 第%d个:%d字节 ----\n",no,n);
//检查包是否包含了至少完整的以太帧(14)，IP(20)和TCP/UDP(8)包头
if(n<42){
perror("recvfrom():");
printf("不完整以太网帧 (errno: %d)\n",errno);
close(sock);
exit(0);
}
analyse_eth(buffer);//调用以太网桢分析函数
}
return 0;
}