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在TCP三次握手后插入伪造的TCP包

 2006-07-04 20:29:21 来源:WEB开发网   
核心提示:一、说明用Socket的API Connect完成TCP建立连接的三次握手,同时子进程抓包,在TCP三次握手后插入伪造的TCP包,抓完三次握手的包后,插入第四个包即可,帧的结构和Eth帧结构不同,不能使用NetPacket::Ethernet模块中的strip函数处理帧首部,从对端返回的第五个包来看插入成功了,但因为插

一、说明

用Socket的API Connect完成TCP建立连接的三次握手,同时子进程抓包,抓完三次握手的包后,插入第四个包即可,从对端返回的第五个包来看插入成功了,但因为插入了一个TCP包,之后的连接将发生混乱。可以将插入的那个包Data设置为HTTP Request,向WEB服务器提交请求。又如果目标系统的TCP序列号是可预计算的,那么是否可以做带伪源地址的Blind TCP three-time handshakes和插入,值得试验!

二、脚本

1、用到几个模块Net::RawIP Net::Pcap Net::PcapUtils NetPacket;

2、pretty_table()函数是我原来做的,用来在命令行下打印表格(Table);

3、测试环境-Linux、ADSL拨号,抓包的接口是ppp0,帧的结构和Eth帧结构不同,不能使用NetPacket::Ethernet模块中的strip函数处理帧首部,根据ethereal抓包的结构,我使用unpack函数取得了帧中的IP包;

三、源代码
#!/usr/bin/perl
#By i_am_jojo@msn.com, 2005/04
use strict;
use warnings;
use Net::RawIP;
use Net::PcapUtils;
use NetPacket::Ethernet;
use NetPacket::IP;
use NetPacket::TCP;
use Socket;
use Getopt::Std;
use POSIX qw(strftime);
my %opts;
getopts('ht:p:u:n:', \%opts);
print_help() and exit if(defined($opts{'h'}));
print_help() and exit if(not defined($opts{'t'}) or not defined($opts{'p'}));
die "\tInvalid Target Ipaddress!\n"
   if(defined($opts{'t'}) and $opts{'t'} !~ m/^\d+.\d+.\d+.\d+$/);
die "\tInvalid Service Port!\n"
   if(defined($opts{'p'}) and $opts{'p'} !~ m/^\d+$/);
my $request;
if(defined($opts{'u'})) {
   $request = "GET $opts{'u'} HTTP/1.1\r\n";
   $request.= "Accept: text/html; text/plain\r\n";
   $request.= "\r\n";
} else {
   $request = "GET / HTTP/1.1\r\n";
   $request.= "Accept: text/html; text/plain\r\n";
   $request.= "\r\n";
}
my $child = fork();
if($child == 0) {
   #child process
   my ($next_packet, %next_header);
   my ($frame_hdr, $ip_packet);
   my ($ip_obj, $tcp_obj);
   my $counter = 0;
   my $pkt_descriptor = Net::PcapUtils::open(
     FILTER => 'ip',
     PROMISC => 0,
     DEV   => 'ppp0',
     #DEV  => 'eth0'
   );
   die "Net::PcapUtils::open returned: $pkt_descriptor\n" if (!ref($pkt_descriptor));
   print strftime '%Y/%m/%d %H:%M:%S, ', localtime and print "begin sniffing ...\n";
   while(($next_packet, %next_header) = Net::PcapUtils::next($pkt_descriptor)) {    
     ($frame_hdr, $ip_packet) = unpack 'H32a*', $next_packet;
     $ip_obj = NetPacket::IP->decode($ip_packet);
     #$ip_obj = NetPacket::IP->decode(NetPacket::Ethernet::eth_strip($next_packet));
     next if ($ip_obj->{'proto'} != 6);
     next if (($ip_obj->{'src_ip'} ne $opts{'t'})
          and ($ip_obj->{'dest_ip'} ne $opts{'t'}));
     $tcp_obj = NetPacket::TCP->decode($ip_obj->{'data'});
     next if (($tcp_obj->{'src_port'} ne $opts{'p'})
          and ($tcp_obj->{'dest_port'} ne $opts{'p'}));
     $counter++;
     print "==ID.$counter==", '=' x 60, "\n";
     print get_ip_hdr($ip_obj);
     print get_tcp_hdr($tcp_obj);
     if($tcp_obj->{'data'}) {
       my $data;
       $data = unpack 'a*', $tcp_obj->{'data'};
       $data =~ s/[\r][\n]//g;
       print pretty_table('TCP data', [$data]);
     }
     if($counter == 3) {
       my $a = new Net::RawIP;
       $a->set({
         'ip' => {
           'id'  => $ip_obj->{'id'} + 1,
           'saddr' => $ip_obj->{'src_ip'},
           'daddr' => $ip_obj->{'dest_ip'}
           },
         'tcp' => {
           'source' => $tcp_obj->{'src_port'},
           'dest'  => $tcp_obj->{'dest_port'},
           'seq'   => $tcp_obj->{'seqnum'},
           'ack_seq' => $tcp_obj->{'acknum'},
           'window' => $tcp_obj->{'winsize'},
           'data'  => $request,
           'psh'   => 1,
           'ack'   => 1
           }
         });
       $a->send;
     }
     last if($counter == 5);
   }
   exit;
} else {
   sleep(1);
   my $trans_serv = getprotobyname('tcp');
   my $dest_sockaddr = sockaddr_in($opts{'p'}, inet_aton($opts{'t'}));
   socket(TCP_SOCK, PF_INET, SOCK_STREAM, $trans_serv);
   connect(TCP_SOCK, $dest_sockaddr);
   sleep(1);
   #close TCP_SOCK;
}
exit;
sub print_help {
   print <<HELP
   %./iamFool.pl [-h] <-t,-p,-u,-n>
   -h  print help
   -t  target ipaddr
   -p  service port
   -u  requested url
         by:i_am_jojo\@msn.com
HELP
}
sub get_ip_hdr {
   my $ip_obj = shift;
   my @ip_hdr;
   push @ip_hdr, [qw(ver tos flags id src_ip proto)];
   push @{$ip_hdr[1]}, $ip_obj->{$_} foreach (qw(ver tos flags id src_ip proto));
   push @ip_hdr, [qw(hlen len foffset ttl dest_ip cksum)];
   push @{$ip_hdr[3]}, $ip_obj->{$_} foreach (qw(hlen len foffset ttl dest_ip cksum));
   return pretty_table('IP Header', @ip_hdr);
}
sub get_tcp_hdr {
   my $tcp_obj = shift;
   my @tcp_hdr;
   push @tcp_hdr, [qw(src_port seqnum hlen flags)];
   push @{$tcp_hdr[1]}, $tcp_obj->{$_} foreach (qw(src_port seqnum hlen flags));
   push @tcp_hdr, [qw(dest_port acknum reserved winsize)];
   push @{$tcp_hdr[3]}, $tcp_obj->{$_} foreach (qw(dest_port acknum reserved winsize));
   return pretty_table('TCP Header', @tcp_hdr);
}
sub pretty_table {
   # prettyTable($aString, @aList); @aList = ( [...], [...] );
   # by i_am_jojo@msn.com
   my ($title, @data) = @_;
   my @temp;
   my @max_length;
   my $row_length;
   my $indent = 4;
   my $the_table;
   foreach my $col (0..$#{$data[0]}) { push @{$temp[$col]}, $_->[$col] foreach (@data); }
   $max_length[$_] = length( (sort{length($b) <=> length($a)} @{$data[$_]} )[0]) + 2 foreach (0..$#data);
   $row_length+= $max_length[$_] foreach (0..$#{$temp[0]}); 
   $row_length+= $#data;
   $the_table = ' ' x $indent.'+'.'-' x $row_length."+\n";
   $the_table.= ' ' x $indent.'| '.$title.' ' x ($row_length - length($title) - 1)."|\n";
   foreach my $row (0..$#temp) {
     $the_table.= ' ' x $indent;
     $the_table.= '+'.'-' x $max_length[$_] foreach (0.. $#{$temp[0]});
     $the_table.= "+\n";
     $the_table.= ' ' x $indent;
     $the_table.= '| '.@{$temp[$row]}[$_].' ' x ($max_length[$_] - length(@{$temp[$row]}[$_]) - 1) foreach (0.. $#{$temp[0]});
     $the_table.= "|\n";
   }
   $the_table.= ' ' x $indent;
   $the_table.= '+'.'-' x $max_length[$_] foreach (0.. $#{$temp[0]});
   $the_table.= "+\n";
   return $the_table;
}

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