Debian El Salvador Blog

Autor:  Carlos Torrento

Objetivo: Tener un servidor dhcp que filtre contenido web y que sirva como router para accesar a internet a través de el.
lo obtendrá al final seria un servidor dhcp con proxy transparente.

Nota: tengo eth0:192.168.0.3 # acceso a mi red con internet
eth1:192.168.2.1 # acceso de mi red
-> Que necesito.
1) acceso a internet (obvio), 2 tarjetas de red y debían por su puesto.

2) Instalar dhcp3-server, squid, dansguardian, iptables

como?

# apt-get install squid
# apt-get install dansguardian
# apt-get install iptables
# apt-get install dhcp3-server

y ahora?

Lo primero que hice y lo más fácil es configurar mi /etc/dhcp/dhcpd.conf
ddns-update-style none;
default-lease-time 600;
max-lease-time 7200;
authoritative;
log-facility local7;

subnet 192.168.2.0 netmask 255.255.255.0 {
range 192.168.2.3 192.168.2.250;
option domain-name-servers 200.85.0.104;
option domain-name-servers 200.85.0.107;
option domain-name “tuxito.net”;
option routers 192.168.2.1;
option broadcast-address 192.168.2.255;
default-lease-time 600;
max-lease-time 7200;
}
Con esta configuración lo que estamos haciendo es que estamos asignando ip´s dinámicas desde la 192.168.0.3 hasta la 192.168.2.250 con netmask 255.255.255.0,
DNS 200.85.0.104 y 200.85.0.107, como puerta de enlace la 192.168.2.1 y un broadcast de 192.168.2.255.

3) Ahora procedemos a configurar el /etc/squid/squid.conf
visible_hostname proxy
http_port 3128 transparent
#We recommend you to use at least the following line.
hierarchy_stoplist cgi-bin ?
#We recommend you to use the following two lines.
acl QUERY urlpath_regex cgi-bin \?
cache deny QUERY
# Apache to signal ETag correctly on such responses
acl apache rep_header Server ^Apache
broken_vary_encoding allow apache
#  To log the request via syslog specify a filepath of “syslog”
access_log /var/log/squid/access.log squid
#Default: hosts_file /etc/hosts
hosts_file /etc/hosts
#Suggested default:
refresh_pattern ^ftp:        1440    20%    10080
refresh_pattern ^gopher:    1440    0%    1440
refresh_pattern .        0    20%    4320
#Recommended minimum configuration:
acl mired src 192.168.0.0 192.168.2.0/255.255.255.0 #agregamos nuestras redes
acl all src 0.0.0.0/0.0.0.0
acl manager proto cache_object
acl localhost src 127.0.0.1/255.255.255.255
acl to_localhost dst 127.0.0.0/8
acl SSL_ports port 443        # https
acl SSL_ports port 563        # snews
acl SSL_ports port 873        # rsync
acl Safe_ports port 80        # http
acl Safe_ports port 21        # ftp
acl Safe_ports port 443    # https
acl Safe_ports port 70        # gopher
acl Safe_ports port 210    # wais
acl Safe_ports port 1025-65535    # unregistered ports
acl Safe_ports port 280        # http-mgmt
acl Safe_ports port 488        # gss-http
acl Safe_ports port 591        # filemaker
acl Safe_ports port 777        # multiling http
acl Safe_ports port 631        # cups
acl Safe_ports port 873        # rsync
acl Safe_ports port 901        # SWAT
acl purge method PURGE
acl CONNECT method CONNECT

# Only allow cachemgr access from localhost
http_access allow mired #damos acceso a nuestras redes
http_access allow localhost
http_access allow manager localhost
http_access deny manager
http_access deny all
# Only allow purge requests from localhost
http_access allow purge localhost
http_access deny purge
# Deny requests to unknown ports
http_access deny !Safe_ports
# Deny CONNECT to other than SSL ports
http_access deny CONNECT !SSL_ports
#http_access allow our_networks
http_access allow localhost
# And finally deny all other access to this proxy
http_access deny all
# and finally allow by default
http_reply_access allow all
#Allow ICP queries from everyone
icp_access allow all
#  TAG: cache_effective_group
#    If you want Squid to run with a specific GID regardless of
#    the group memberships of the effective user then set this
#    to the group (or GID) you want Squid to run as. When set
#    all other group privileges of the effective user is ignored
#    and only this GID is effective. If Squid is not started as
#    root the user starting Squid must be member of the specified
#    group.
#cache_effective_group proxy
# Nota: debo de crear un usuario squid y un grupo squid
#agregamos el usuario y el grupo con que va a trabajar
cache_effective_user squid
cache_effective_group squid
Con esto tendríamos configurado en dhcp y el squid

4) ahora vamos a configurar el dansguardian
Como son un montón de líneas solo mostrare las de configuración:
# DansGuardian config file for version 2.8.0 with Anti-Virus plug-in 6.4.3
# **NOTE** as of version 2.7.5 most of the list files are now in dansguardianf1.conf
#UNCONFIGURED - Please remove this line after configuration
reportinglevel = 3
languagedir = ‘/etc/dansguardian/languages’
language = ’spanish’
loglevel = 3
logexceptionhits = on
logfileformat = 1
loglocation = ‘/var/log/dansguardian/access.log’
filterip = 192.168.0.3
filterport = 8080
proxyip = 192.168.0.3
proxyport = 3128
accessdeniedaddress = ‘http://localhost/’
nonstandarddelimiter = on
usecustombannedimage = 1
custombannedimagefile = ‘/etc/dansguardian/transparent1×1.gif’
filtergroups = 1
filtergroupslist = ‘/etc/dansguardian/filtergroupslist’
bannediplist = ‘/etc/dansguardian/bannediplist’
exceptioniplist = ‘/etc/dansguardian/exceptioniplist’
banneduserlist = ‘/etc/dansguardian/banneduserlist’
exceptionuserlist = ‘/etc/dansguardian/exceptionuserlist’
bannedurllist = ‘/etc/dansguardian/bannedurllist’
exceptionurllist = ‘/etc/dansguardian/bannedurllist’
showweightedfound = on
weightedphrasemode = 2
urlcachenumber = 3000
urlcacheage = 900
phrasefiltermode = 2
preservecase = 0
hexdecodecontent = 0
forcequicksearch = 0
reverseaddresslookups = off
reverseclientiplookups = off
createlistcachefiles = on
maxuploadsize = -1
maxcontentfiltersize = 256
usernameidmethodproxyauth = on
usernameidmethodntlm = off # **NOT IMPLEMENTED**
usernameidmethodident = off
preemptivebanning = on
forwardedfor = off
usexforwardedfor = off
logconnectionhandlingerrors = on
maxchildren = 120
minchildren = 8
minsparechildren = 4
preforkchildren = 6
maxsparechildren = 32
maxagechildren = 500
ipcfilename = ‘/tmp/.dguardianipc’
urlipcfilename = ‘/tmp/.dguardianurlipc’
nodaemon = off
nologger = off
softrestart = off
# ANTIVIRUS SETTINGS
# ——————–
virusscan = on
virusengine = ‘clamav’
tricklelength = 32768
forkscanlength = 32768
firsttrickledelay = 10
followingtrickledelay = 10
maxcontentscansize = 41904304
virusscanexceptions = on
urlcachecleanonly = on
virusscannertimeout = 60
notify = 0
emaildomain = ‘your.domain.com’
postmaster = ‘postmaster@your.domain.com’
emailserver = ‘127.0.0.1:25′
downloaddir = ‘/tmp/dgvirus’
# CLAMAV SETTINGS
# ——————–
clmaxfiles = 1500
clmaxreclevel = 3
clmaxfilesize = 10485760
clblockencryptedarchives = off
cldetectbroken = off
# CLAMDSCAN SETTINGS
# ——————–
clamdsocket = ‘/tmp/clamd’
# KASPERSKY 5 SETTINGS
# ——————–
avesocket = ‘/var/run/aveserver’
# TROPHIE SETTINGS
# ——————–
trophiesocket = ‘/var/run/trophie’
# SOPHIE SETTINGS
# ——————–
sophiesocket = ‘/var/run/sophie’
# ICAP SETTINGS (experimental)
# —————————-
icapsocket = ‘localhost:1344′

# OPTION: icapservice
icapservice = ‘icap://localhost/avscan’
daemonuser = ’squid’
daemongroup = ’squid’
bueno ya con eso tendriamos el dansguardian configurado(nota:_ aquí le agregue el usuario y grupo que tuve que haber creado “squid”)
5) acontinuacion les muestro el script con iptables que funciona para bloquear puertos y redireccionar el trafico.
#!/bin/sh

# squid server IP
SQUID_SERVER=”192.168.0.3″

# Interface connected to Internet
INTERNET=”eth0″
# Interface connected to LAN
LAN_IN=”eth1″
# Squid port
SQUID_PORT=”3128″
# DO NOT MODIFY BELOW
# Clean old firewall
iptables –F
iptables –X
iptables -t nat –F
iptables -t nat –X
iptables -t mangle –F
iptables -t mangle –X
# Load IPTABLES modules for NAT and IP conntrack support
modprobe ip_conntrack
modprobe ip_conntrack_ftp
# For win xp ftp client
#modprobe ip_nat_ftp
echo 1 > /proc/sys/net/ipv4/ip_forward
# Setting default filter policy
iptables -P INPUT DROP
iptables -P OUTPUT ACCEPT
# Unlimited access to loop back
iptables -A INPUT -i lo -j ACCEPT
iptables -A OUTPUT -o lo -j ACCEPT

# Allow UDP, DNS and Passive FTP
iptables -A INPUT -i $INTERNET -m state –state ESTABLISHED,RELATED -j ACCEPT
# set this system as a router for Rest of LAN
iptables –table nat –append POSTROUTING –out-interface $INTERNET -j MASQUERADE
iptables –append FORWARD –in-interface $LAN_IN -j ACCEPT
# unlimited access to LAN
iptables -A INPUT -i $LAN_IN -j ACCEPT
iptables -A OUTPUT -o $LAN_IN -j ACCEPT
# DNAT port 80 request comming from LAN systems to squid 3128 ($SQUID_PORT) aka #transparent proxy
iptables -t nat -A PREROUTING -i $LAN_IN -p tcp –dport 80 -j DNAT –to $SQUID_SERVER:8080
# if it is same system
iptables -t nat -A PREROUTING -i $INTERNET -p tcp –dport 80 -j REDIRECT –to-port $SQUID_PORT
# DROP everything and Log it
iptables -A INPUT -j LOG
iptables -A INPUT -j DROP
lo guardamos proxy.sh
y le asignamos permisos de ejecucion # chmod +x proxy.sh
para correrlo seria #sh proxy.sh

6) como ultimo paso para bloquear las urls o expresiones, nos descargarnos la blacklist de http://urlblacklist.com/ la descomprimimos en /etc/dansguardian/
Y eso seria todo ya tenemos un servidor dhcp con proxy transparente.
Espero que les sirva tanto como a mi.

Cualquier corrección hacérmela saber a cltorrento AT gmail.com o tuxito AT linuxmail.org