Posts Tagged ‘Networking’

no “setup” command – CentOS

October 12th, 2012 7 Comments »

 

I usually use “setup” to do the firewall setup for permissive or not and setting of SELINUX, etc….

But on a minimal install you don’t have access to setup command, which is my favorite

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1[root@tel ~]# setup
2-bash: setup: command not found

So how to install it in minimal install ?

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1yum –y install setuptool
2yum –y install system-config-network*
3yum -y install system-config-firewall*
4yum –y install system-config-securitylevel-tui
5yum –y install system-config-keyboard

(thanks JoVeN for spell mistake)

For system services utility install ntsysv (as Perico suggested in the user comments)

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1yum -y install ntsysv

setup-CentOS

That’s it….!! Enjoy


8 steps to protect your Cisco router

August 27th, 2010 5 Comments »

Network security is a completely changing area; new devices like IDS (Intrusion
Detection systems), IPS (Intrusion Prevention systems), and Honeypots are modifying the
way people think about security. Companies are spending thousand of dollars on new
security devices, but forgetting the basic, the first line of defense: the border router.

Although a lot of people may think that routers don’t need to be protect, they are
completely wrong. A lot of secure problems appear all time against this kind of device
and most of them are vulnerable. Read the rest of this entry »


Simple Construction of a RAW TCP/IP Packet

August 11th, 2010 1 Comment »
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001#!/usr/local/bin/perl
002 
003use Socket;
004 
005$src_host = $ARGV[0]; # The source IP/Hostname
006$src_port = $ARGV[1]; # The Source Port
007$dst_host = $ARGV[2]; # The Destination IP/Hostname
008$dst_port = $ARGV[3]; # The Destination Port.
009 
010 if(!defined $src_host or !defined $src_port or !defined $dst_host or !defined $dst_port) {
011   print "Usage: $0 <source host> <source port> <dest host> <dest port>\n";
012   exit;
013 }
014 else {
015  main();
016 }
017  
018sub main {
019 my $src_host = (gethostbyname($src_host))[4];
020 my $dst_host = (gethostbyname($dst_host))[4];
021 
022 socket(RAW, AF_INET, SOCK_RAW, 255) || die $!;
023 setsockopt(RAW, 0, 1, 1);
024  
025 my ($packet) = makeheaders($src_host, $src_port, $dst_host, $dst_port);
026 my ($destination) = pack('Sna4x8', AF_INET, $dst_port, $dst_host);
027 send(RAW,$packet,0,$destination);
028}
029 
030sub makeheaders {
031 local($src_host,$src_port,$dst_host,$dst_port) = @_;
032 my $zero_cksum = 0;
033 # Lets construct the TCP half
034 my $tcp_proto          = 6;
035 my ($tcp_len)          = 20;
036 my $syn                = 13456;
037 my $ack                = 0;
038 my $tcp_headerlen      = "5";
039 my $tcp_reserved       = 0;
040 my $tcp_head_reserved  = $tcp_headerlen .
041                          $tcp_reserved;
042 my $tcp_urg            = 0; # Flag bits
043 my $tcp_ack            = 0; # eh no
044 my $tcp_psh            = 0; # eh no
045 my $tcp_rst            = 0; # eh no
046 my $tcp_syn            = 1; # yeah lets make a connexion! :)
047 my $tcp_fin            = 0;
048 my $null               = 0;
049 my $tcp_win            = 124;
050 my $tcp_urg_ptr        = 0;
051 my $tcp_all            = $null . $null .
052                          $tcp_urg . $tcp_ack .
053                          $tcp_psh . $tcp_rst .
054                          $tcp_syn . $tcp_fin ;
055 
056 # In order to calculate the TCP checksum we have
057 # to create a fake tcp header, hence why we did
058 # all this stuff :) Stevens called it psuedo headers :)
059 
060 my ($tcp_pseudo) = pack('a4a4CCnnnNNH2B8nvn',
061  $tcp_len,$src_port,$dst_port,$syn,$ack,
062  $tcp_head_reserved,$tcp_all,$tcp_win,$null,$tcp_urg_ptr);
063 
064 my ($tcp_checksum) = &checksum($tcp_pseudo);
065 
066 # Now lets construct the IP packet
067 my $ip_ver             = 4;
068 my $ip_len             = 5;
069 my $ip_ver_len         = $ip_ver . $ip_len;
070 my $ip_tos             = 00;
071 my ($ip_tot_len)       = $tcp_len + 20;
072 my $ip_frag_id         = 19245;
073 my $ip_frag_flag       = "010";
074 my $ip_frag_oset       = "0000000000000";
075 my $ip_fl_fr           = $ip_frag_flag . $ip_frag_oset;
076 my $ip_ttl             = 30;
077 
078 # Lets pack this baby and ship it on out!
079 my ($pkt) = pack('H2H2nnB16C2na4a4nnNNH2B8nvn',
080  $ip_ver_len,$ip_tos,$ip_tot_len,$ip_frag_id,
081  $ip_fl_fr,$ip_ttl,$tcp_proto,$zero_cksum,$src_host,
082  $dst_host,$src_port,$dst_port,$syn,$ack,$tcp_head_reserved,
083  $tcp_all,$tcp_win,$tcp_checksum,$tcp_urg_ptr);
084 
085 return $pkt;
086}
087 
088sub checksum {
089 # This of course is a blatent rip from _the_ GOD,
090 # W. Richard Stevens.
091   
092 my ($msg) = @_;
093 my ($len_msg,$num_short,$short,$chk);
094 $len_msg = length($msg);
095 $num_short = $len_msg / 2;
096 $chk = 0;
097 foreach $short (unpack("S$num_short", $msg)) {
098  $chk += $short;
099 }
100 $chk += unpack("C", substr($msg, $len_msg - 1, 1)) if $len_msg % 2;
101 $chk = ($chk >> 16) + ($chk & 0xffff);
102 return(~(($chk >> 16) + $chk) & 0xffff);
103}