:


  
http://www.atmsk.ru/popups/articleswindow.php?id=27&print=print


    ,      
 .

         ()   ssh

 wneshnijserver   mashina  .

mashina$   ssh    -R new_port_tam:localhost:port_nash     wneshnijserver
mashina$   ssh -C -L     port_tam:localhost:new_port_nash wneshnijserver
 -L -      localhost
 -R -      .
 -C -  

   1.       

mashina$   ssh -R 2222:localhost:22 wneshnijserver
wneshnijserver@username password:
wneshnijserver$

:

wneshnijserver$ netstat -an | grep 2222
tcp        0      0 127.0.0.1:2222          0.0.0.0:*               LISTEN

:

wneshnijserver$  ssh    -p 2222 localhost  #   mashina ssh2
wneshnijserver$  ssh -1 -p 2222 localhost  #   mashina ssh1

 2.           ,   


mashina$   ssh -C -L 3128:localhost:8080 wneshnijserver



mashina$   netstat -an | grep 8080
tcp        0      0 127.0.0.1:8080          0.0.0.0:*               LISTEN

:

Netscape > Preference > Proxy > localhost: 8080



        squid


1.  squid     
http_port 10.10.10.7:3128   #  http_port 3128
http_port 12.0.0.7:3128

2.   
# acl rfc-user ident moshkow root

# ,     IP
acl our_network  src 10.10.10.1-10.10.10.4
acl our_network2 src 12.0.0.0/255.255.255.0
#     ,  
acl passwd_user proxy_auth REQUIRED

http_access allow our_network
http_access allow our_network2
http_access allow passwd_user
http_access deny all   #  - 

# ,       /etc/passwd
authenticate_program /usr/lib/squid/ncsa_auth /etc/passwd

####################################
/usr/lib/squid/ncsa_auth /etc/passwd
Password:
root parolroota
OK
###  /etc/shadow     -    


    NAT  RedHat 8++

10 - , 172 - 

     1.
      ip forwarding,    ,
    /sbin/sysctl -w net.ipv4.ip_forward = 1

  2.
/sbin/iptables -t nat -A POSTROUTING -s 10.0.0.0/255.255.255.0 -o if1 -j SNAT --to-source 172.10.10.1

           3.
           /sbin/iptables-save > /etc/sysconfig/iptables
           chkconfig --levels 2345 on


     


  - ipfw  altq.
  - ipa +    .


          


Iproute2   ,    default route,   - .
       .
 
ip route add default via a.c.b.c table tablenumberone
ip rule add from v.x.y.w/24 table tablenumberone
    .   . , ,     .
  , ,  - 
ip rule add from v.x.y.w/24 table to k.l.m.o tablenumberone
, ,  .
,   .     .     iproute2.
, ,  iptables  ,       .
    ,    ,    iproute2  :-).
    http://lartc.org.






      ipchains. Redhat 7.0


# ,     
ls -al /proc/net/ip_fwchains

#  -   
ipchains -A input -s 155.208.157.51 -p tcp -j DENY

ipchains -L  #  
ipchains -F  #  


       -. IPFWADM, redhat 6.2

echo 1 > /proc/sys/net/ipv4/ip_forward  #    
ipfwadm -F -p deny            #  
ipfwadm -F -a m -S 195.0.0.2/0 -D 0.0.0.0/0 #   195.0.0.2


         


while sleep 5
do
  ipfw add 111 drop ip from baduser.host.name to any
  sleep 15
  ipfw delete 111
done


     sendmail


HContent-disposition: $>CheckSircam

SCheckSircam
Rmultipart message              $#error $@ 5.7.1 $: 554 Sircam infected message


      accounting


NET-3 HOWTO (razdel "IP Accounting") i "man ipfwadm"


          


myhost:82 -- > secondhost:8499
ipfwadm -Fa accept -b -P tcp -S 0/0 82 -D secondIPaddr/32 8499


      


 Date: 7 May 1998
 From: Igor Mikhayliuk 

- ,   06 1998 10:06, Dima Volodin  All:

 DV >   .   __,     , 
 DV >  - 80   http  443   https.    , 
 DV >     -  -  ,  
 DV >   NT,        CNN
 DV >  -    ( CNN)   -   (, 8765).
 DV >  .      , ssh 
 DV >  proxy.  ,   22    ( 
 DV >     ).

   , ,   .
;)

 DV > ,   ,   "     
 DV >  "     TCP     IP
 DV > ,         ,   
 DV >    .

, ,   : "WinNT    "?

 DV >      -

    .
:)

 DV >    __ T
 DV > ,         ,
 DV > 
 DV >     .  ,  
 DV > UD   domain (53), ntp (123), real--   .. , 
 DV > ,  icmp.   ping,     icmp,
 DV >    traceroute - udp    ,  
 DV >  . ,   , MS tracert 
 DV >  ,   traceroute,    .  ,
 DV > ,       src ( 
 DV >  security,   ),      dst
 DV >       src.

      , .

 DV >  , - ,    ,   
 DV > .

 , - ,       . 
      ,   ,  / 
.  ,      21- , 
  ,    20-.      - 
,  .     
,   ,   ,   ,  
.       .
   ,  -    
,    .     ,   /
  ,   ..    .   

.
,         
,       .      ,  
 .   -       
WinTalk.   ,      ,  
  ,   ,   ,
    -     
  1024.    ,   .   

  -  , Guardian Session Wall-3, 
  ,  ,   ,  , 
    .
:(
 ,     ,       
 /,  WAN,   - DTP .
 ,      ,  ,  
,   ,        
,         
.
:)


    Sentry Port Scan Detector 0.60

 Date: 28 May 1998 05:45:05 -0000
 From: crowland@psionic.com

Sentry is a port scan detector for Linux, *BSD, and most UNIX variants.
Sentry monitors your systems for port probing activity and will then take
any of the following actions:

1) Log the attacker hostname/IP and ports probed.
2) Run external program.
3) Configure routing table to drop route of attacking host.
4) Configure local packet filter (ipfwadm/ipfw) to drop all packets from
attacking host.
Sentry will now detect and respond to stealth scans against your host from
advanced scanners such as nmap:

http://www.insecure.org/nmap/index.html


     *   firewall  * 


NAT - Network Address Translation -    
 ipfwadm

 .
 Kernel reconfigure

  .
 TCPD

Proxy  httpd, ftp,  ..
 squid

Proxy  , ftp, X11
 TIS fw tollkit

Proxy   TCP 
 socks5


       IPFWADM


 Date: 17 Jun 1998
 From: MushyPea 

On Tue, 16 Jun 1998, Avery Pennarun wrote:

> Here is the script I use on my home IP masquerade system.  It is designed
> to deny everything except what is specifically allowed in some of the
> definitions near the top.  Note that there is one fatal problem -- the
> input firewall is changed to allow incoming data back to ports 1024
> through 65535, because any of those might have been used to create an
> _outgoing_ connection (and thus might have data been sent back to them).
> NFS servers might run on one of these high port numbers, so watch out.

I do the following:

1) To make the script more readable, use variables:

ME="a.b.c.d/32"
HI="1024:65535"
ANY="0.0.0.0/0"

2) Use "-y -o" options to log all connection attempts (ie. SYN bit set) to
syslog (you need verbose firewall logging compiled into the kernel), and
accept the packets in both directions for these connections.

2a) Example of a bi-directional service

# SMTP mail traffic
/bin/echo -n "SMTP/"
/sbin/ipfwadm -O -a accept -P tcp -S ${ME} ${HI} -D ${ANY} 25 -y -o
/sbin/ipfwadm -O -a accept -P tcp -S ${ME} ${HI} -D ${ANY} 25
/sbin/ipfwadm -I -a accept -P tcp -S ${ANY} 25 -D ${ME} ${HI}
/sbin/ipfwadm -I -a accept -P tcp -S ${ANY} ${HI} -D ${ME} 25 -y -o
/sbin/ipfwadm -I -a accept -P tcp -S ${ANY} ${HI} -D ${ME} 25
/sbin/ipfwadm -O -a accept -P tcp -S ${ME} 25 -D ${ANY} ${HI}

2b) A tricky one - FTP

# Incoming FTP
/bin/echo -n "FTPin/"
/sbin/ipfwadm -I -a accept -P tcp -S ${ANY} ${HI} -D ${ME} 20:21 -y -o
/sbin/ipfwadm -I -a accept -P tcp -S ${ANY} ${HI} -D ${ME} 20:21
/sbin/ipfwadm -O -a accept -P tcp -S ${ME} 20:21 -D ${ANY} ${HI}

3) Drop everything else - note, the 'without logging' section only applies
if you ever set your interface(s) into promiscuous mode... it's wise not
to log packets to/from elsewhere, otherwise the machine load hits the
roof, and the log file expands rapidly... I found out the hard way. ;)

# Deny everything else
# with logging... (target = me)
/sbin/ipfwadm -I -a deny -S 0/0 -D ${ME} -o
/sbin/ipfwadm -O -a deny -S ${ME} -D 0/0 -o
# without logging... (target != me)
/sbin/ipfwadm -I -a deny -S 0/0 -D 0/0
/sbin/ipfwadm -O -a deny -S 0/0 -D 0/0

Hope that's of some help - oh, one thing - if you decide to use logging,
make sure the logfile is on another partition somewhere, in case someone
floods your box to try and fill up the disk!  Logging is worth the effort
- I've detected port scans and other such nasties this way.


Ian.

--
Ian Marsh
mushypea@dominion.net.uk                                   ... Email
http://www.etchq.demon.co.uk/                              ... WWW
http://www.dominion.net.uk/ telnet://dominion.net.uk:2468/ ... Dominion
http://www.alpha4.com/      telnet://alpha4.com:3214/      ... MBa4


      


rc.firewall:

ifconfig eth0 promisc
ifconfig eth1 promisc
ifconfig eth1 arp
ifconfig eth0 arp
route add -net default gw 193.232.173.45 dev eth1
brcfg -enable >> /dev/null
ipfwadm -I -f
ipfwadm -O -f
ipfwadm -F -f
ipfwadm -I -a reject -S 0.0.0.0/0.0.0.0               -D 0.0.0.0/0.0.0.0
ipfwadm -I -i accept -S 195.231.183.1/255.255.255.255 -D 0.0.0.0/0.0.0.0
ipfwadm -I -i accept -S 195.231.183.2/255.255.255.255 -D 0.0.0.0/0.0.0.0
ipfwadm -I -i accept -P tcp    -S 195.231.183.0/255.255.255.0 ftp telnet -D 0.0.0.0/0.0.0.0
ipfwadm -O -a reject -P tcp -k -S 195.231.183.0/255.255.255.0 -D 0.0.0.0/0.0.0.0 137 138 139



     named


From: Adam Sulmicki 

One of reasons for presenting is that in all examples shown so far
it seemed that everyone suggested to leave named full-open. However,
it does not always have to be case. Say, if you are running an private
network then you want just to allow named get data transfers from
trusted host and that is all.

[root@eax /root]# cat ipfwadm-named
#!/bin/sh
#allow connection only from trusted named servers
ME="1.2.3.4"             # MY ip
NS1="10.20.30.41"        # IP of the primary name server
NS2="10.20.30.42"        # IP of the secondary name server
NS3="10.20.30.43"        # IP of the trietary name server
SRV="domain"
/sbin/ipfwadm -I -f
/sbin/ipfwadm -I -a accept -D ${ME} $SRV -W eth0 -P udp -S $NS1 $SRV
/sbin/ipfwadm -I -a accept -D ${ME} $SRV -W eth0 -P tcp -S $NS1 $SRV
/sbin/ipfwadm -I -a accept -D ${ME} $SRV -W eth0 -P udp -S $NS2 $SRV
/sbin/ipfwadm -I -a accept -D ${ME} $SRV -W eth0 -P tcp -S $NS2 $SRV
/sbin/ipfwadm -I -a accept -D ${ME} $SRV -W eth0 -P udp -S $NS3 $SRV
/sbin/ipfwadm -I -a accept -D ${ME} $SRV -W eth0 -P tcp -S $NS3 $SRV
/sbin/ipfwadm -I -a reject -D ${ME} $SRV -W eth0 -P tcp -o -v -x -e
/sbin/ipfwadm -I -a reject -D ${ME} $SRV -W eth0 -P udp -o -v -x -e


And while we are speaking about named. Here is an example
as someone from "Catholic liberal arts institution" (as per their web
page) connecting to my box. I assume that person was scanning
whole subnet searching for vulnerable versions of named.


        

 mrtg,    smnpget.

"ipfwadm configuration utility"
http://www.ejj.net/~sonny/fwconfig/fwconfig.html


     ,     




1. Security Problems in the TCP/IP Protocol Suite
-- S.M. Bellovin then of AT&T
ftp://research.att.com/dist/internet_security/ipext.ps.Z

2. A Weekness in the 4.2 BSD Unix TCP/IP Software
-- R.T. Morris then of AT&T
ftp://research.att.com/dist/internet_security/117.ps.Z

*3.* Network (In)Security Through IP Packet Filtering
-- D. Brent Chapman
ftp://coast.cs.purdue.edu/pub/doc/firewalls/Brent_Chapman_packet_filtering.ps.ZOn the subject of firewall and IP packet filtering just go
to (and read the whole directory):
ftp://coast.cs.purdue.edu/pub/doc/firewalls/

In case of interest, the source of the IP filter that
OpenBSD uses, are at:(claims it runs under linux 2.0.31 too)
http://cheops.anu.edu.au/~avalon/

But one of the best monitoring tools is tcpdump, its
current version being 3.4, and you need libpcap-0.x, to
work. Both of the packages are ready to download from:
ftp://ftp.ee.lbl.gov/tcpdump.tar.Z
ftp://ftp.ee.lbl.gov/libpcap.tar.Z
ftp://ftp.ee.lbl.gov/tcpslice.tar.Z
The last one is for reading files with live snapshots
from your net, these written by tcpdump, at later times,
when needed.
WARN: untar libpcap where your *current untarred* tcpdump
files lie, in other words under the tcpdump-3.4 directory!



      firewall - LRP


 From: Rob Bringman 
   To:
           linux-security@redhat.com

I am the Firewall-1 administrator where I work and it has a very nice
GUI tool for defining objects (can be hosts, networks, DNS domains,
groups of hosts, etc.) and a straightforward way of building a
rulebase.

At home I use the LRP with a mini-qmail daemon forwarding the e-mail
via  qmqp to the real mailhost,  and sshd for remote admin.  It has
ipautofw, ipportfw and masquerading.

I really can't think of anything I can do with the Firewall-1 machine
that I can't do with this LRP machine.  The whole OS used to fit on a
floppy until I added the mini-qmail and sshd packages.  Now it boots
off a small HD and runs only on ramdisks.  Except for the GUI and the
price, I'd say they are about equal in terms of power and protection.

I've looked into TIS but never used it.  It involved running proxy
daemons on the firewall for telnet ftp and snmp.   I like the LRP much
better.

(for those that don't know, LRP is the Linux Router Project.  see
http://www.linuxrouter.org )


    TCPwrapper: hosts.deny


# /etc/hosts/deny
#
# deny all, send an alert email to root...
ALL : ALL : \
        banners /etc/banners/deny : \
        spawn ( \
/bin/echo -e "\n\
TCP Wrappers\:  Connection Refused\n\
By\:            $(uname -n)\n\
Process\:       %d (pid %p)\n\
\n\
User\:          %u\n\
Host\:          %c\n\
Date\:          $(date)\n\
" | /bin/mail -s "$(uname -n) wrappers\: %d refused for %c" \
root@localhost ) &

====8<------ end of cut --------------------------

This will deny access to anyone not specifically allowed (from
/etc/hosts.allow), give banners message (specific for the daemon being
called - see the man pages), and generate a very informative mail message
sent to root.  (You can add other recipients to that line, btw).

We have found this to be VERY useful here...

[mod: Some remarked that things like "%u" are "client controlled" and
could be used to exploit Tony's system. The manual however claims:

      Characters in % expansions that may confuse the shell
      are replaced by underscores.

so that should be OK. -- REW]

                send
mail -        .


    IPFilter


  ipfILTER    ?

ipf -z -f my_ipfilter_rules_file






     ,   ssh1 & ssh2 , :


1.  ssh-1.2.26 (!)
2.  ssh-2.x.x
3.  "sshd2_config"  (  ):
     Ssh1Compatibility               yes
     Sshd1Path                       /usr/sbin/sshd1
4.  "ssh2_config"  (  ):
     Ssh1Compatibility               yes
     Ssh1Path                        /usr/bin/ssh1

  ssh2   ,     -
   inetd.conf      TCP-wrappera hosts.allow/hosts.deny

/etc/inetd.conf
ssh2	stream  tcp 	nowait  root    /usr/sbin/tcpd	sshd2 -i

/etc/hosts.allow
sshd2 : 123.232.175.0/255.255.255.0, 127.0.0.0/255.0.0.0, 234.567.890.12





    Linux ,     
   sshd,        ssh.

  Dec 6 11:03:11 artur sshd[2177]: Invalid user test from 193.220.141.151
  Dec 6 11:03:11 artur sshd[2177]: Failed password for invalid user test from 193.220.141.151 port 46079 ssh2
  Dec 6 11:03:15 artur sshd[2180]: Failed password for root from 193.220.141.151 port 46144 ssh2
          -  .  
  "".       
  IP     recent .

  iptables -A INPUT -p tcp -m state --state NEW --dport 22 -m recent --update --seconds 20 -j DROP
  iptables -A INPUT -p tcp -m state --state NEW --dport 22 -m recent --set -j ACCEPT


      


 # iptables -F INPUT
 # iptables -A INPUT -m state -state EASTABLISHED,RELATED -j ACCEPT
 # iptables -A INPUT -i lo -j ACCEPT
 # iptables -P INPUT DROP
 # iptables -F FORWARD
 # iptables -P FORWARD ACCEPT
 # iptables -t nat -F
 # iptables -t nat -A POSTROUTING -o { } -j SNAT to { IP}
 #  ip  
 # iptables -t nat -A POSTROUTING -o { } -j MASQUERADE



Last-modified: Sun, 08 Jan 2006 12:19:38 GMT

  :