Packet Sniffer Code in C using Linux Sockets (BSD) – Part 2
2012-07-11 00:52 Rollen Holt 阅读(851) 评论(0) 编辑 收藏 举报In the previous part we made a simple sniffer which created a raw socket and started receiving on it. But it had few drawbacks :
1. Could sniff only incoming data.
2. Could sniff only TCP or UDP or ICMP or any one protocol packets at a time.
3. Provided IP frames , so ethernet headers were not available.
In this article we are going to modify the same code to fix the above 3 drawbacks. However we shall not be using libpcap.
This will be done using pure linux sockets.
The difference is very small and is 2 lines :
Instead of :
sock_raw = socket(AF_INET , SOCK_RAW , IPPROTO_TCP);
We do :
sock_raw = socket( AF_PACKET , SOCK_RAW , htons(ETH_P_ALL)) ;
//Optional
//setsockopt(sock_raw , SOL_SOCKET , SO_BINDTODEVICE , "eth0" , strlen("eth0")+ 1 );
and we are done. Now it will :
1. Sniff both incoming and outgoing traffic.
2. Sniff ALL ETHERNET FRAMES , which includes all kinds of IP packets and even more if there are any.
3. Provides the Ethernet headers too , which contain the mac addresses.
The setsockopt line is optional.
Its important to provide the correct interface name to setsockopt , eth0 in this case and in most cases.
So may be you would like to present the user with a list of interfaces available and allow him to choose the one to be sniffed.
Here is the full source code :
#include<netinet/in.h>
#include<errno.h>
#include<netdb.h>
#include<stdio.h> //For standard things
#include<stdlib.h> //malloc
#include<string.h> //strlen
#include<netinet/ip_icmp.h> //Provides declarations for icmp header
#include<netinet/udp.h> //Provides declarations for udp header
#include<netinet/tcp.h> //Provides declarations for tcp header
#include<netinet/ip.h> //Provides declarations for ip header
#include<netinet/if_ether.h> //For ETH_P_ALL
#include<net/ethernet.h> //For ether_header
#include<sys/socket.h>
#include<arpa/inet.h>
#include<sys/ioctl.h>
#include<sys/time.h>
#include<sys/types.h>
#include<unistd.h>
void ProcessPacket(unsigned char* , int);
void print_ip_header(unsigned char* , int);
void print_tcp_packet(unsigned char * , int );
void print_udp_packet(unsigned char * , int );
void print_icmp_packet(unsigned char* , int );
void PrintData (unsigned char* , int);
FILE *logfile;
struct sockaddr_in source,dest;
int tcp=0,udp=0,icmp=0,others=0,igmp=0,total=0,i,j;
int main()
{
int saddr_size , data_size;
struct sockaddr saddr;
unsigned char *buffer = (unsigned char *) malloc(65536); //Its Big!
logfile=fopen("log.txt","w");
if(logfile==NULL)
{
printf("Unable to create log.txt file.");
}
printf("Starting...\n");
int sock_raw = socket( AF_PACKET , SOCK_RAW , htons(ETH_P_ALL)) ;
//setsockopt(sock_raw , SOL_SOCKET , SO_BINDTODEVICE , "eth0" , strlen("eth0")+ 1 );
if(sock_raw < 0)
{
//Print the error with proper message
perror("Socket Error");
return 1;
}
while(1)
{
saddr_size = sizeof saddr;
//Receive a packet
data_size = recvfrom(sock_raw , buffer , 65536 , 0 , &saddr , (socklen_t*)&saddr_size);
if(data_size <0 )
{
printf("Recvfrom error , failed to get packets\n");
return 1;
}
//Now process the packet
ProcessPacket(buffer , data_size);
}
close(sock_raw);
printf("Finished");
return 0;
}
void ProcessPacket(unsigned char* buffer, int size)
{
//Get the IP Header part of this packet , excluding the ethernet header
struct iphdr *iph = (struct iphdr*)(buffer + sizeof(struct ethhdr));
++total;
switch (iph->protocol) //Check the Protocol and do accordingly...
{
case 1: //ICMP Protocol
++icmp;
print_icmp_packet( buffer , size);
break;
case 2: //IGMP Protocol
++igmp;
break;
case 6: //TCP Protocol
++tcp;
print_tcp_packet(buffer , size);
break;
case 17: //UDP Protocol
++udp;
print_udp_packet(buffer , size);
break;
default: //Some Other Protocol like ARP etc.
++others;
break;
}
printf("TCP : %d UDP : %d ICMP : %d IGMP : %d Others : %d Total : %d\r", tcp , udp , icmp , igmp , others , total);
}
void print_ethernet_header(unsigned char* Buffer, int Size)
{
struct ethhdr *eth = (struct ethhdr *)Buffer;
fprintf(logfile , "\n");
fprintf(logfile , "Ethernet Header\n");
fprintf(logfile , " |-Destination Address : %.2X-%.2X-%.2X-%.2X-%.2X-%.2X \n", eth->h_dest[0] , eth->h_dest[1] , eth->h_dest[2] , eth->h_dest[3] , eth->h_dest[4] , eth->h_dest[5] );
fprintf(logfile , " |-Source Address : %.2X-%.2X-%.2X-%.2X-%.2X-%.2X \n", eth->h_source[0] , eth->h_source[1] , eth->h_source[2] , eth->h_source[3] , eth->h_source[4] , eth->h_source[5] );
fprintf(logfile , " |-Protocol : %u \n",(unsigned short)eth->h_proto);
}
void print_ip_header(unsigned char* Buffer, int Size)
{
print_ethernet_header(Buffer , Size);
unsigned short iphdrlen;
struct iphdr *iph = (struct iphdr *)(Buffer + sizeof(struct ethhdr) );
iphdrlen =iph->ihl*4;
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(logfile , "\n");
fprintf(logfile , "IP Header\n");
fprintf(logfile , " |-IP Version : %d\n",(unsigned int)iph->version);
fprintf(logfile , " |-IP Header Length : %d DWORDS or %d Bytes\n",(unsigned int)iph->ihl,((unsigned int)(iph->ihl))*4);
fprintf(logfile , " |-Type Of Service : %d\n",(unsigned int)iph->tos);
fprintf(logfile , " |-IP Total Length : %d Bytes(Size of Packet)\n",ntohs(iph->tot_len));
fprintf(logfile , " |-Identification : %d\n",ntohs(iph->id));
//fprintf(logfile , " |-Reserved ZERO Field : %d\n",(unsigned int)iphdr->ip_reserved_zero);
//fprintf(logfile , " |-Dont Fragment Field : %d\n",(unsigned int)iphdr->ip_dont_fragment);
//fprintf(logfile , " |-More Fragment Field : %d\n",(unsigned int)iphdr->ip_more_fragment);
fprintf(logfile , " |-TTL : %d\n",(unsigned int)iph->ttl);
fprintf(logfile , " |-Protocol : %d\n",(unsigned int)iph->protocol);
fprintf(logfile , " |-Checksum : %d\n",ntohs(iph->check));
fprintf(logfile , " |-Source IP : %s\n",inet_ntoa(source.sin_addr));
fprintf(logfile , " |-Destination IP : %s\n",inet_ntoa(dest.sin_addr));
}
void print_tcp_packet(unsigned char* Buffer, int Size)
{
unsigned short iphdrlen;
struct iphdr *iph = (struct iphdr *)( Buffer + sizeof(struct ethhdr) );
iphdrlen = iph->ihl*4;
struct tcphdr *tcph=(struct tcphdr*)(Buffer + iphdrlen + sizeof(struct ethhdr));
int header_size = sizeof(struct ethhdr) + iphdrlen + tcph->doff*4;
fprintf(logfile , "\n\n***********************TCP Packet*************************\n");
print_ip_header(Buffer,Size);
fprintf(logfile , "\n");
fprintf(logfile , "TCP Header\n");
fprintf(logfile , " |-Source Port : %u\n",ntohs(tcph->source));
fprintf(logfile , " |-Destination Port : %u\n",ntohs(tcph->dest));
fprintf(logfile , " |-Sequence Number : %u\n",ntohl(tcph->seq));
fprintf(logfile , " |-Acknowledge Number : %u\n",ntohl(tcph->ack_seq));
fprintf(logfile , " |-Header Length : %d DWORDS or %d BYTES\n" ,(unsigned int)tcph->doff,(unsigned int)tcph->doff*4);
//fprintf(logfile , " |-CWR Flag : %d\n",(unsigned int)tcph->cwr);
//fprintf(logfile , " |-ECN Flag : %d\n",(unsigned int)tcph->ece);
fprintf(logfile , " |-Urgent Flag : %d\n",(unsigned int)tcph->urg);
fprintf(logfile , " |-Acknowledgement Flag : %d\n",(unsigned int)tcph->ack);
fprintf(logfile , " |-Push Flag : %d\n",(unsigned int)tcph->psh);
fprintf(logfile , " |-Reset Flag : %d\n",(unsigned int)tcph->rst);
fprintf(logfile , " |-Synchronise Flag : %d\n",(unsigned int)tcph->syn);
fprintf(logfile , " |-Finish Flag : %d\n",(unsigned int)tcph->fin);
fprintf(logfile , " |-Window : %d\n",ntohs(tcph->window));
fprintf(logfile , " |-Checksum : %d\n",ntohs(tcph->check));
fprintf(logfile , " |-Urgent Pointer : %d\n",tcph->urg_ptr);
fprintf(logfile , "\n");
fprintf(logfile , " DATA Dump ");
fprintf(logfile , "\n");
fprintf(logfile , "IP Header\n");
PrintData(Buffer,iphdrlen);
fprintf(logfile , "TCP Header\n");
PrintData(Buffer+iphdrlen,tcph->doff*4);
fprintf(logfile , "Data Payload\n");
PrintData(Buffer + header_size , Size - header_size );
fprintf(logfile , "\n###########################################################");
}
void print_udp_packet(unsigned char *Buffer , int Size)
{
unsigned short iphdrlen;
struct iphdr *iph = (struct iphdr *)(Buffer + sizeof(struct ethhdr));
iphdrlen = iph->ihl*4;
struct udphdr *udph = (struct udphdr*)(Buffer + iphdrlen + sizeof(struct ethhdr));
int header_size = sizeof(struct ethhdr) + iphdrlen + sizeof udph;
fprintf(logfile , "\n\n***********************UDP Packet*************************\n");
print_ip_header(Buffer,Size);
fprintf(logfile , "\nUDP Header\n");
fprintf(logfile , " |-Source Port : %d\n" , ntohs(udph->source));
fprintf(logfile , " |-Destination Port : %d\n" , ntohs(udph->dest));
fprintf(logfile , " |-UDP Length : %d\n" , ntohs(udph->len));
fprintf(logfile , " |-UDP Checksum : %d\n" , ntohs(udph->check));
fprintf(logfile , "\n");
fprintf(logfile , "IP Header\n");
PrintData(Buffer , iphdrlen);
fprintf(logfile , "UDP Header\n");
PrintData(Buffer+iphdrlen , sizeof udph);
fprintf(logfile , "Data Payload\n");
//Move the pointer ahead and reduce the size of string
PrintData(Buffer + header_size , Size - header_size);
fprintf(logfile , "\n###########################################################");
}
void print_icmp_packet(unsigned char* Buffer , int Size)
{
unsigned short iphdrlen;
struct iphdr *iph = (struct iphdr *)(Buffer + sizeof(struct ethhdr));
iphdrlen = iph->ihl * 4;
struct icmphdr *icmph = (struct icmphdr *)(Buffer + iphdrlen + sizeof(struct ethhdr));
int header_size = sizeof(struct ethhdr) + iphdrlen + sizeof icmph;
fprintf(logfile , "\n\n***********************ICMP Packet*************************\n");
print_ip_header(Buffer , Size);
fprintf(logfile , "\n");
fprintf(logfile , "ICMP Header\n");
fprintf(logfile , " |-Type : %d",(unsigned int)(icmph->type));
if((unsigned int)(icmph->type) == 11)
{
fprintf(logfile , " (TTL Expired)\n");
}
else if((unsigned int)(icmph->type) == ICMP_ECHOREPLY)
{
fprintf(logfile , " (ICMP Echo Reply)\n");
}
fprintf(logfile , " |-Code : %d\n",(unsigned int)(icmph->code));
fprintf(logfile , " |-Checksum : %d\n",ntohs(icmph->checksum));
//fprintf(logfile , " |-ID : %d\n",ntohs(icmph->id));
//fprintf(logfile , " |-Sequence : %d\n",ntohs(icmph->sequence));
fprintf(logfile , "\n");
fprintf(logfile , "IP Header\n");
PrintData(Buffer,iphdrlen);
fprintf(logfile , "UDP Header\n");
PrintData(Buffer + iphdrlen , sizeof icmph);
fprintf(logfile , "Data Payload\n");
//Move the pointer ahead and reduce the size of string
PrintData(Buffer + header_size , (Size - header_size) );
fprintf(logfile , "\n###########################################################");
}
void PrintData (unsigned char* data , int Size)
{
int i , j;
for(i=0 ; i < Size ; i++)
{
if( i!=0 && i%16==0) //if one line of hex printing is complete...
{
fprintf(logfile , " ");
for(j=i-16 ; j<i ; j++)
{
if(data[j]>=32 && data[j]<=128)
fprintf(logfile , "%c",(unsigned char)data[j]); //if its a number or alphabet
else fprintf(logfile , "."); //otherwise print a dot
}
fprintf(logfile , "\n");
}
if(i%16==0) fprintf(logfile , " ");
fprintf(logfile , " %02X",(unsigned int)data[i]);
if( i==Size-1) //print the last spaces
{
for(j=0;j<15-i%16;j++)
{
fprintf(logfile , " "); //extra spaces
}
fprintf(logfile , " ");
for(j=i-i%16 ; j<=i ; j++)
{
if(data[j]>=32 && data[j]<=128)
{
fprintf(logfile , "%c",(unsigned char)data[j]);
}
else
{
fprintf(logfile , ".");
}
}
fprintf(logfile , "\n" );
}
}
}
The log file will looks somewhat like this :
***********************TCP Packet*************************
Ethernet Header
|-Destination Address : 00-25-5E-1A-3D-F1
|-Source Address : 00-1C-C0-F8-79-EE
|-Protocol : 8
IP Header
|-IP Version : 4
|-IP Header Length : 5 DWORDS or 20 Bytes
|-Type Of Service : 0
|-IP Total Length : 141 Bytes(Size of Packet)
|-Identification : 13122
|-TTL : 64
|-Protocol : 6
|-Checksum : 45952
|-Source IP : 192.168.1.6
|-Destination IP : 74.125.71.125
TCP Header
|-Source Port : 33655
|-Destination Port : 5222
|-Sequence Number : 78458457
|-Acknowledge Number : 2427066746
|-Header Length : 5 DWORDS or 20 BYTES
|-Urgent Flag : 0
|-Acknowledgement Flag : 1
|-Push Flag : 1
|-Reset Flag : 0
|-Synchronise Flag : 0
|-Finish Flag : 0
|-Window : 62920
|-Checksum : 21544
|-Urgent Pointer : 0
DATA Dump
IP Header
00 25 5E 1A 3D F1 00 1C C0 F8 79 EE 08 00 45 00 .%^.=.....y...E.
00 8D 33 42 ..3B
TCP Header
40 00 40 06 B3 80 C0 A8 01 06 4A 7D 47 7D 83 77 @.@..?....J}G}.w
14 66 04 AD .f..
Data Payload
17 03 01 00 60 A0 9C 5D 14 A1 25 AB CE 8B 7C EB ....`..]..%...|.
1A A4 43 A6 60 DD E8 6B 6E 43 C1 94 6A D2 25 23 ..C.`..knC..j.%#
03 98 59 67 1A 2C 07 D3 7E B2 B8 9F 83 38 4C 69 ..Yg.,..~....8Li
D3 3A 8E 0D 9E F0 6B CE 9E 6B F4 E1 BD 9E 50 53 .:....k..k....PS
6D F6 AB 11 05 D6 41 82 F0 03 0C A6 E2 48 2B 71 m.....A......H+q
16 81 FF 5B DF 50 D4 5B AD 90 04 5E 4C 94 E7 9B ...[.P.[...^L...
0B 72 7E 32 88 .r~2.
###########################################################
***********************TCP Packet*************************
Ethernet Header
|-Destination Address : 00-1C-C0-F8-79-EE
|-Source Address : 00-25-5E-1A-3D-F1
|-Protocol : 8
IP Header
|-IP Version : 4
|-IP Header Length : 5 DWORDS or 20 Bytes
|-Type Of Service : 32
|-IP Total Length : 141 Bytes(Size of Packet)
|-Identification : 30410
|-TTL : 48
|-Protocol : 6
|-Checksum : 49112
|-Source IP : 74.125.71.125
|-Destination IP : 192.168.1.6
TCP Header
|-Source Port : 5222
|-Destination Port : 33655
|-Sequence Number : 2427066746
|-Acknowledge Number : 78458558
|-Header Length : 5 DWORDS or 20 BYTES
|-Urgent Flag : 0
|-Acknowledgement Flag : 1
|-Push Flag : 1
|-Reset Flag : 0
|-Synchronise Flag : 0
|-Finish Flag : 0
|-Window : 63784
|-Checksum : 63942
|-Urgent Pointer : 0
DATA Dump
IP Header
00 1C C0 F8 79 EE 00 25 5E 1A 3D F1 08 00 45 20 ....y..%^.=...E
00 8D 76 CA ..v.
TCP Header
00 00 30 06 BF D8 4A 7D 47 7D C0 A8 01 06 14 66 ..0...J}G}.....f
83 77 90 AA .w..
Data Payload
17 03 01 00 60 01 B9 00 4E C7 79 0D 89 09 15 BF ....`...N.y.....
9C BB 53 8D 50 DB 97 4E 25 AC FA E2 55 20 94 8B ..S.P..N%...U ..
AF 6E 84 E2 95 8B D9 26 A3 63 7D E4 F0 CA 6F 72 .n.....&.c}...or
F6 29 95 79 98 BC 12 BF F1 C5 34 42 83 A3 F8 B6 .).y......4B....
9E B2 7B 1C FC F7 3E BA 4E B1 FB 36 89 93 E3 58 ..{...>.N..6...X
A7 FC 5B C3 68 9E 35 CC 25 00 7D 82 3D DB 86 EA ..[.h.5.%.}.=...
66 89 99 B3 65 f...e
###########################################################
In the above log we can see the ethernet headers being printed. They show the source and destination mac address along with the packet protocol. 8 means IP protocol
Note :
1. If you want to sniff only IP and ARP packets for example then you can try this :
sock_raw = socket( AF_PACKET , SOCK_RAW , htons(ETH_P_IP|ETH_P_ARP)) ;
The complete list of protocols is found in /usr/include/linux/if_ether.h
/* * These are the defined Ethernet Protocol ID's. */ #define ETH_P_LOOP 0x0060 /* Ethernet Loopback packet */ #define ETH_P_PUP 0x0200 /* Xerox PUP packet */ #define ETH_P_PUPAT 0x0201 /* Xerox PUP Addr Trans packet */ #define ETH_P_IP 0x0800 /* Internet Protocol packet */ #define ETH_P_X25 0x0805 /* CCITT X.25 */ #define ETH_P_ARP 0x0806 /* Address Resolution packet */ #define ETH_P_BPQ 0x08FF /* G8BPQ AX.25 Ethernet Packet [ NOT AN OFFICIALLY REGISTERED ID ] */ #define ETH_P_IEEEPUP 0x0a00 /* Xerox IEEE802.3 PUP packet */ #define ETH_P_IEEEPUPAT 0x0a01 /* Xerox IEEE802.3 PUP Addr Trans packet */ #define ETH_P_DEC 0x6000 /* DEC Assigned proto */ #define ETH_P_DNA_DL 0x6001 /* DEC DNA Dump/Load */ #define ETH_P_DNA_RC 0x6002 /* DEC DNA Remote Console */ #define ETH_P_DNA_RT 0x6003 /* DEC DNA Routing */ #define ETH_P_LAT 0x6004 /* DEC LAT */ #define ETH_P_DIAG 0x6005 /* DEC Diagnostics */ #define ETH_P_CUST 0x6006 /* DEC Customer use */ #define ETH_P_SCA 0x6007 /* DEC Systems Comms Arch */ #define ETH_P_TEB 0x6558 /* Trans Ether Bridging */ #define ETH_P_RARP 0x8035 /* Reverse Addr Res packet */ #define ETH_P_ATALK 0x809B /* Appletalk DDP */ #define ETH_P_AARP 0x80F3 /* Appletalk AARP */ #define ETH_P_8021Q 0x8100 /* 802.1Q VLAN Extended Header */ #define ETH_P_IPX 0x8137 /* IPX over DIX */ #define ETH_P_IPV6 0x86DD /* IPv6 over bluebook */ #define ETH_P_PAUSE 0x8808 /* IEEE Pause frames. See 802.3 31B */ #define ETH_P_SLOW 0x8809 /* Slow Protocol. See 802.3ad 43B */ #define ETH_P_WCCP 0x883E /* Web-cache coordination protocol * defined in draft-wilson-wrec-wccp-v2-00.txt */ #define ETH_P_PPP_DISC 0x8863 /* PPPoE discovery messages */ #define ETH_P_PPP_SES 0x8864 /* PPPoE session messages */ #define ETH_P_MPLS_UC 0x8847 /* MPLS Unicast traffic */ #define ETH_P_MPLS_MC 0x8848 /* MPLS Multicast traffic */ #define ETH_P_ATMMPOA 0x884c /* MultiProtocol Over ATM */ #define ETH_P_LINK_CTL 0x886c /* HPNA, wlan link local tunnel */ #define ETH_P_ATMFATE 0x8884 /* Frame-based ATM Transport * over Ethernet */ #define ETH_P_PAE 0x888E /* Port Access Entity (IEEE 802.1X) */ #define ETH_P_AOE 0x88A2 /* ATA over Ethernet */ #define ETH_P_TIPC 0x88CA /* TIPC */ #define ETH_P_1588 0x88F7 /* IEEE 1588 Timesync */ #define ETH_P_FCOE 0x8906 /* Fibre Channel over Ethernet */ #define ETH_P_FIP 0x8914 /* FCoE Initialization Protocol */ #define ETH_P_EDSA 0xDADA /* Ethertype DSA [ NOT AN OFFICIALLY REGISTERED ID ] */ /* * Non DIX types. Won't clash for 1500 types. */ #define ETH_P_802_3 0x0001 /* Dummy type for 802.3 frames */ #define ETH_P_AX25 0x0002 /* Dummy protocol id for AX.25 */ #define ETH_P_ALL 0x0003 /* Every packet (be careful!!!) */ #define ETH_P_802_2 0x0004 /* 802.2 frames */ #define ETH_P_SNAP 0x0005 /* Internal only */ #define ETH_P_DDCMP 0x0006 /* DEC DDCMP: Internal only */ #define ETH_P_WAN_PPP 0x0007 /* Dummy type for WAN PPP frames*/ #define ETH_P_PPP_MP 0x0008 /* Dummy type for PPP MP frames */ #define ETH_P_LOCALTALK 0x0009 /* Localtalk pseudo type */ #define ETH_P_CAN 0x000C /* Controller Area Network */ #define ETH_P_PPPTALK 0x0010 /* Dummy type for Atalk over PPP*/ #define ETH_P_TR_802_2 0x0011 /* 802.2 frames */ #define ETH_P_MOBITEX 0x0015 /* Mobitex (kaz@cafe.net) */ #define ETH_P_CONTROL 0x0016 /* Card specific control frames */ #define ETH_P_IRDA 0x0017 /* Linux-IrDA */ #define ETH_P_ECONET 0x0018 /* Acorn Econet */ #define ETH_P_HDLC 0x0019 /* HDLC frames */ #define ETH_P_ARCNET 0x001A /* 1A for ArcNet :-) */ #define ETH_P_DSA 0x001B /* Distributed Switch Arch. */ #define ETH_P_TRAILER 0x001C /* Trailer switch tagging */ #define ETH_P_PHONET 0x00F5 /* Nokia Phonet frames */ #define ETH_P_IEEE802154 0x00F6 /* IEEE802.15.4 frame */ #define ETH_P_CAIF 0x00F7 /* ST-Ericsson CAIF protocol */
Enjoy!!
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我喜欢程序员，他们单纯、固执、容易体会到成就感；面对压力，能够挑灯夜战不眠不休；面对困难，能够迎难而上挑战自我。他
们也会感到困惑与傍徨，但每个程序员的心中都有一个比尔盖茨或是乔布斯的梦想“用智慧开创属于自己的事业”。我想说的是，其
实我是一个程序员
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