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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