| 在TCP三次握手后插入伪造的TCP包
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 <
-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;
}
四、结果举例
==Result eXample==
2005/05/02 21:51:23, begin sniffing ...
==ID.1==============================================================
+---------------------------------------------------+
| IP Header |
+--------+---------------+---------+----------------+
| ver | 4 | hlen | 5 |
+--------+---------------+---------+----------------+
| tos | 0 | len | 60 |
+--------+---------------+---------+----------------+
| flags | 2 | foffset | 0 |
+--------+---------------+---------+----------------+
| id | 20682 | ttl | 64 |
+--------+---------------+---------+----------------+
| src_ip | 218.11.149.14 | dest_ip | 64.233.189.104 |
+--------+---------------+---------+----------------+
| proto | 6 | cksum | 31878 |
+--------+---------------+---------+----------------+
+------------------------------------------+
| TCP Header |
+----------+------------+-----------+------+
| src_port | 32851 | dest_port | 80 |
+----------+------------+-----------+------+
| seqnum | 1104143983 | acknum | 0 |
+----------+------------+-----------+------+
| hlen | 10 | reserved | 0 |
+----------+------------+-----------+------+
| flags | 2 | winsize | 5808 |
+----------+------------+-----------+------+
==ID.2==============================================================
+---------------------------------------------------+
| IP Header |
+--------+----------------+---------+---------------+
| ver | 4 | hlen | 5 |
+--------+----------------+---------+---------------+
| tos | 0 | len | 44 |
+--------+----------------+---------+---------------+
| flags | 0 | foffset | 0 |
+--------+----------------+---------+---------------+
| id | 63029 | ttl | 241 |
+--------+----------------+---------+---------------+
| src_ip | 64.233.189.104 | dest_ip | 218.11.149.14 |
+--------+----------------+---------+---------------+
| proto | 6 | cksum | 26154 |
+--------+----------------+---------+---------------+
+------------------------------------------------+
| TCP Header |
+----------+------------+-----------+------------+
| src_port | 80 | dest_port | 32851 |
+----------+------------+-----------+------------+
| seqnum | 3660731207 | acknum | 1104143984 |
+----------+------------+-----------+------------+
| hlen | 6 | reserved | 0 |
+----------+------------+-----------+------------+
| flags | 18 | winsize | 4356 |
+----------+------------+-----------+------------+
==ID.3==============================================================
+---------------------------------------------------+
| IP Header |
+--------+---------------+---------+----------------+
| ver | 4 | hlen | 5 |
+--------+---------------+---------+----------------+
| tos | 0 | len | 40 |
+--------+---------------+---------+----------------+
| flags | 2 | foffset | 0 |
+--------+---------------+---------+----------------+
| id | 20684 | ttl | 64 |
+--------+---------------+---------+----------------+
| src_ip | 218.11.149.14 | dest_ip | 64.233.189.104 |
+--------+---------------+---------+----------------+
| proto | 6 | cksum | 31896 |
+--------+---------------+---------+----------------+
+------------------------------------------------+
| TCP Header |
+----------+------------+-----------+------------+
| src_port | 32851 | dest_port | 80 |
+----------+------------+-----------+------------+
| seqnum | 1104143984 | acknum | 3660731208 |
+----------+------------+-----------+------------+
| hlen | 5 | reserved | 0 |
+----------+------------+-----------+------------+
| flags | 16 | winsize | 5808 |
+----------+------------+-----------+------------+
==ID.4==============================================================
+---------------------------------------------------+
| IP Header |
+--------+---------------+---------+----------------+
| ver | 4 | hlen | 5 |
+--------+---------------+---------+----------------+
| tos | 16 | len | 89 |
+--------+---------------+---------+----------------+
| flags | 2 | foffset | 0 |
+--------+---------------+---------+----------------+
| id | 20685 | ttl | 64 |
+--------+---------------+---------+----------------+
| src_ip | 218.11.149.14 | dest_ip | 64.233.189.104 |
+--------+---------------+---------+----------------+
| proto | 6 | cksum | 31830 |
+--------+---------------+---------+----------------+
+------------------------------------------------+
| TCP Header |
+----------+------------+-----------+------------+
| src_port | 32851 | dest_port | 80 |
+----------+------------+-----------+------------+
| seqnum | 1104143984 | acknum | 3660731208 |
+----------+------------+-----------+------------+
| hlen | 5 | reserved | 0 |
+----------+------------+-----------+------------+
| flags | 24 | winsize | 5808 |
+----------+------------+-----------+------------+
+--------------------------------------------+
| TCP data |
+--------------------------------------------+
| GET / HTTP/1.1Accept: text/html; text/plai |
+--------------------------------------------+
==ID.5==============================================================
+---------------------------------------------------+
| IP Header |
+--------+----------------+---------+---------------+
| ver | 4 | hlen | 5 |
+--------+----------------+---------+---------------+
| tos | 0 | len | 40 |
+--------+----------------+---------+---------------+
| flags | 0 | foffset | 0 |
+--------+----------------+---------+---------------+
| id | 47931 | ttl | 241 |
+--------+----------------+---------+---------------+
| src_ip | 64.233.189.104 | dest_ip | 218.11.149.14 |
+--------+----------------+---------+---------------+
| proto | 6 | cksum | 41256 |
+--------+----------------+---------+---------------+
+------------------------------------------------+
| TCP Header |
+----------+------------+-----------+------------+
| src_port | 80 | dest_port | 32851 |
+----------+------------+-----------+------------+
| seqnum | 3660731208 | acknum | 1104144033 |
+----------+------------+-----------+------------+
| hlen | 5 | reserved | 0 |
+----------+------------+-----------+------------+
| flags | 16 | winsize | 4356 |
+----------+------------+-----------+------------+
===End=== |
