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一个half-open的扫描器 <br>
---------------------------------------------------------------------------- <br>
---- <br>
coal 于 00-5-19 16:48:11 加贴在 绿盟科技论坛(bbs.nsfocus.com)--UNIX系统安全 <br>
： <br>
刚刚写好，可以用来学习socket的编程/* <br>
============================================================================ <br>
====== <br>
This is a half-open scanner <br>
coded by coal( coal2000@263.net ) <br>
============================================================================ <br>
====== <br>
*/ <br>
#include <stdio.h> <br>
#include <stdlib.h> <br>
#include <sys/socket.h> <br>
#include <netinet/in.h> <br>
#include <netinet/ip.h> <br>
#include <netinet/tcp.h> <br>
#include <sys/ioctl.h> <br>
#include <sys/types.h> <br>
#include <signal.h> <br>
#include <unistd.h> <br>
struct pseudohdr { <br>
u_int32_t source; <br>
u_int32_t dest; <br>
u_int8_t zero; <br>
u_int8_t protocol; <br>
u_int16_t len; <br>
}; <br>
struct rect <br>
{ <br>
struct iphdr ip; <br>
struct tcphdr tcp; <br>
unsigned char blah[65535]; <br>
} recv_tcp; <br>
void banner( void ); <br>
void usage( char* me ); <br>
void handler(int whateva); <br>
u_short in_chksum(u_short *ptr, int nbytes); <br>
struct sockaddr_in to; <br>
char buffer[2024]; <br>
int timeout=0; <br>
int main( int argc, char* argv[] ) <br>
{ <br>
int i; <br>
if ( argc < 2 ) { <br>
usage( argv[0] ); <br>
exit(1); <br>
} <br>
banner(); <br>
to.sin_family = AF_INET; <br>
to.sin_addr.s_addr = inet_addr( argv[1] ); <br>
printf("start scan....\n"); <br>
for ( i = 0 ; i < 100 ; i ++ ) { <br>
if ( scan ( i )==1 ) <br>
printf("port %d is opened!\n"); <br>
} <br>
printf("scan over!!!\n"); <br>
} <br>
int scan ( int i ) <br>
{ <br>
int sock; <br>
static int count = 0; <br>
struct tcphdr *pTcpHdr = ( struct tcphdr* ) buffer ; <br>
char* data = ( char* ) ( pTcpHdr + 1 ); <br>
char* fakehdr; <br>
struct pseudohdr pseudohdr; <br>
int ret,clen; <br>
int incl = 1; <br>
signal(SIGALRM, handler); <br>
sock = socket( AF_INET, SOCK_RAW, IPPROTO_TCP ); <br>
if ( sock < 0 ) { <br>
perror( "socket:" ); <br>
exit(1); <br>
} <br>
count ++; <br>
to.sin_port = htons( i ); <br>
// fill tcp packet; <br>
pTcpHdr->dest = htons( i ); // only for http server; <br>
pTcpHdr->source = getpid() + count ; <br>
pTcpHdr->seq = 100+count; <br>
pTcpHdr->ack_seq = 0; <br>
pTcpHdr->res1 = 0; <br>
pTcpHdr->fin = 0; <br>
pTcpHdr->syn = 1; // this tcp packet is a sync packet; <br>
pTcpHdr->rst = 0; <br>
pTcpHdr->ack = 0; <br>
pTcpHdr->urg = 0; <br>
pTcpHdr->doff = sizeof(struct tcphdr) >> 2; <br>
pTcpHdr->window = htons( 512 ); <br>
pTcpHdr->check = 0; <br>
pTcpHdr->urg_ptr = 0; <br>
// fill pseudo header <br>
fakehdr = calloc( sizeof( struct pseudohdr )+ sizeof( struct tcphdr <br>
), 1); <br>
pseudohdr.source = inet_addr("10.11.81.195"); <br>
pseudohdr.dest = to.sin_addr.s_addr; <br>
pseudohdr.protocol = IPPROTO_TCP; <br>
pseudohdr.zero = 0; <br>
pseudohdr.len = htons(sizeof( struct tcphdr )); <br>
memcpy ( fakehdr, &pseudohdr, sizeof( struct pseudohdr ) ); <br>
memcpy ( (void*)(fakehdr+sizeof( struct pseudohdr )), pTcpHdr, sizeo <br>
f(struct tcphdr) ); <br>
pTcpHdr->check = in_chksum( (u_short*)fakehdr , sizeof( struct pseud <br>
ohdr ) + sizeof( struct tcphdr) ); <br>
// send the packet out; <br>
sendto( sock , pTcpHdr , sizeof(struct tcphdr), 0, &to, sizeof(struc <br>
t sockaddr) ); <br>
timeout = 0; <br>
alarm(5); <br>
while(1) <br>
{ <br>
read(sock, (struct recv_tcp *)&recv_tcp, 65535); <br>
if( timeout == 1) <br>
{ <br>
close(sock); <br>
timeout=0; <br>
return -1; <br>
} <br>
if ( recv_tcp.tcp.dest == getpid()+count ) <br>
{ <br>
alarm(0); <br>
close(sock); <br>
/* It shouldnt be 1 */ <br>
if(recv_tcp.tcp.rst == 1) <br>
return 0; <br>
else <br>
return 1; <br>
} <br>
} <br>
} <br>
} <br>
u_short in_chksum(u_short *ptr, int nbytes) <br>
{ <br>
register long sum; /* assumes long == 32 bits */ <br>
u_short oddbyte; <br>
register u_short answer; /* assumes u_short == 16 bits */ <br>
sum = 0; <br>
while (nbytes > 1) <br>
{ <br>
sum += *ptr++; <br>
nbytes -= 2; <br>
} <br>
if (nbytes == 1) <br>
{ <br>
oddbyte = 0; /* make sure top half is zero */ <br>
*((u_char *) &oddbyte) = *(u_char *)ptr; /* one byte only */ <br>
sum += oddbyte; <br>
} <br>
sum = (sum >> 16) + (sum & 0xffff); /* add high-16 to low-16 */ <br>
sum += (sum >> 16); /* add carry */ <br>
answer = ~sum; /* ones-complement, then truncate to 16 bits */ <br>
return((u_short) answer); <br>
} <br>
} <br>
void usage( char* me ) <br>
{ <br>
printf("usage:%s host\n", me ); <br>
} <br>
void banner( void ) <br>
{ <br>
printf("This is a half-open connection scanner.\n"); <br>
printf("coded by coal(coal2000@263.net),5/18/2000\n"); <br>
} <br>
void handler(int whateva) <br>
{ <br>
alarm(0); <br>
timeout = 1; <br>
} <br>
———————————————————————— <br>
回复:一个half-open的扫描器 <br>
---------------------------------------------------------------------------- <br>
---- <br>
backend 于 00-5-20 15:55:56 加贴在 绿盟科技论坛(bbs.nsfocus.com)--UNIX系统安 <br>
全： <br>
我来回答，如何？ <br>
1、pTcpHdr->res1 对应 TCP 头的哪一部分？ <br>
res1变量的长度为4 bits，它指向TCP报文头部的保留字段（共6 bits）的前4 bits。另 <br>
外还有一个变量是res2，长度为2 bits，指向剩下的2 bits。 <br>
2、pTcpHdr->source = getpid() + count ; 用意何在？ <br>
无它，只不过是随便指定一个TCP源端口而已。 <br>
3、pTcpHdr->doff = sizeof(struct tcphdr) >> 2; 用意何在？ <br>
doff即"data offset"，通常也称为HLEN（Head LENgth：头部长度）。按RFC793标准说 <br>
明是指“数据区在报文段中的偏移量”。由于它是一个以32 bits（双字）为单位的长度 <br>
值，所以要进行移位操作。 <br>
=== 说难不难，说易不易。=== <br>
</small><hr>
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