Install squid proxy on centos
Squid is a caching and forwarding web proxy. It has a wide variety of uses, from speeding up a web server by caching repeated requests; to caching web, DNS and other computer network lookups for a group of people sharing network resources; to aiding security by filtering traffic. Although primarily used for HTTP and FTP, Squid includes limited support for several other protocols including TLS, SSL, Internet Gopher and HTTPS.
Update yum repositories and packages by typing the below command
[root@hackthesec ~]# yum update
Step 1:- Install squid package and dependencies using the below command
[root@hackthesec ~]# yum install squid
By default squid configuration file "/etc/squid/squid.conf" will contains recommended minimum configuration and squid caching feature will work without making any changes . Recommended minimum configuration will looks like the below
# # Recommended minimum configuration: # acl manager proto cache_object acl localhost src 127.0.0.1/32 ::1 acl to_localhost dst 127.0.0.0/8 0.0.0.0/32 ::1 # Example rule allowing access from your local networks. # Adapt to list your (internal) IP networks from where browsing # should be allowed acl localnet src 10.0.0.0/8 # RFC1918 possible internal network acl localnet src 172.16.0.0/12 # RFC1918 possible internal network acl localnet src 192.168.0.0/16 # RFC1918 possible internal network acl localnet src fc00::/7 # RFC 4193 local private network range acl localnet src fe80::/10 # RFC 4291 link-local (directly plugged) machines acl SSL_ports port 443 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 CONNECT method CONNECT # # Recommended minimum Access Permission configuration: # # Only allow cachemgr access from localhost http_access allow manager localhost http_access deny manager # Deny requests to certain unsafe ports http_access deny !Safe_ports # Deny CONNECT to other than secure SSL ports http_access deny CONNECT !SSL_ports # We strongly recommend the following be uncommented to protect innocent # web applications running on the proxy server who think the only # one who can access services on "localhost" is a local user #http_access deny to_localhost # # INSERT YOUR OWN RULE(S) HERE TO ALLOW ACCESS FROM YOUR CLIENTS # # Example rule allowing access from your local networks. # Adapt localnet in the ACL section to list your (internal) IP networks # from where browsing should be allowed http_access allow localnet http_access allow localhost # And finally deny all other access to this proxy http_access deny all # Squid normally listens to port 3128 http_port 3128 # We recommend you to use at least the following line. hierarchy_stoplist cgi-bin ? # Uncomment and adjust the following to add a disk cache directory. #cache_dir ufs /var/spool/squid 100 16 256 # Leave coredumps in the first cache dir coredump_dir /var/spool/squid # Add any of your own refresh_pattern entries above these. refresh_pattern ^ftp: 1440 20% 10080 refresh_pattern ^gopher: 1440 0% 1440 refresh_pattern -i (/cgi-bin/|?) 0 0% 0 refresh_pattern . 0 20% 4320
Step 2:- Now start squid service
[root@hackthesec ~]# service squid start
and type this below command to start squid service automatically while booting.
[root@hackthesec ~]# chkconfig --levels 235 squid on
Step 3:- Setup your web browser to access Internet through proxy server on port 3128
IE : Tools » Internet options »Connections » LAN settings » Choose "Use a proxy server for your LAN" » Type your Proxy server ip (192.168.1.11 ) and port no 3128
Firefox : Options / Preferences » Advanced » Network » Settings » Choose "Manual proxy configuration " » Type your Proxy server ip (192.168.1.11 ) and port no 3128
Step 4:- Browse some sites and check the access log file on proxy server
[root@hackthesec ~]# cat /var/log/squid/access.log 1343759484.645 265 192.168.1.15 TCP_MISS/304 477 GET http://platform.twitter.com/widgets.js - DIRECT/23.64.79.144 application/javascript 1343759484.681 309 192.168.1.15 TCP_MISS/304 839 GET http://apis.google.com/js/plusone.js - DIRECT/173.194.36.36 - 1343759485.005 178 192.168.1.15 TCP_MISS/200 495 GET http://www.google-analytics.com/__utm.gif? - DIRECT/74.125.236.142 image/gif 1343759502.763 20292 192.168.1.15 TCP_MISS/200 1898 CONNECT s-static.ak.facebook.com:443 - DIRECT/23.64.66.110 - 1343759502.765 20292 192.168.1.15 TCP_MISS/200 1898 CONNECT s-static.ak.facebook.com:443 - DIRECT/23.64.66.110 - 1343759723.040 240567 192.168.1.15 TCP_MISS/200 2904 CONNECT plusone.google.com:443 - DIRECT/173.194.36.41 - 1343759934.518 459 192.168.1.15 TCP_MISS/200 495 GET http://www.google-analytics.com/__utm.gif? - DIRECT/173.194.36.8 image/gif 1343759943.131 2186 192.168.1.15 TCP_MISS/200 8343 CONNECT www.facebook.com:443 - DIRECT/66.220.146.94 - 1343759943.266 10616 192.168.1.15 TCP_MISS/200 2790 CONNECT apis.google.com:443 - DIRECT/74.125.236.128 - 1343759943.267 10615 192.168.1.15 TCP_MISS/200 2228 CONNECT ssl.gstatic.com:443 - DIRECT/74.125.236.143 - 1343759950.875 2596 192.168.1.15 TCP_MISS/200 32219 CONNECT www.facebook.com:443 - DIRECT/66.220.146.94 - 1343759961.388 20443 192.168.1.15 TCP_MISS/200 1911 CONNECT s-static.ak.fbcdn.net:443 - DIRECT/23.64.77.177 -
Troubleshooting :
If you not able to browse using proxy settings , Disable the firewall ( iptables ) and selinux service on your squid proxy server .
Disable firewall ( Iptables ) :-
[root@hackthesec ~]# service iptables stop
[root@hackthesec ~]# chkconfig iptables off
Disable Selinux :- open the file /etc/selinux/config and find the line
SELINUX=enforcing
and replace with
SELINUX=disabled
now reboot the server and try step 4.
Configure squid proxy as web filter:
You can restrict user access to particular websites or keywords using access control lists (ACLs) .
Restricting Access to specific web sites :
For example , we can see how to block facebook.com and gmail.com .
Step 1:- create a file ( /etc/squid/blockedsites.squid ) and add the site names one per line.
[root@hackthesec ~]# cat /etc/squid/blockedsites.squid
#blocked sites
www.facebook.com
www.gmail.com
Step 2:- Open the /etc/squid/squid.conf and create a new acl " blocksites" and acl type "dstdomain" in the acl section like the below .
acl Safe_ports port 488 # gss-http acl Safe_ports port 591 # filemaker acl Safe_ports port 777 # multiling http acl CONNECT method CONNECT # ACL blocksites acl blocksites dstdomain "/etc/squid/blockedsites.squid"
and add the following line "http_access deny blocksites" to http_section to deny the access to the acl "blocksites" .
# Recommended minimum Access Permission configuration: # # Only allow cachemgr access from localhost http_access allow manager localhost # Deny access to blocksites ACL http_access deny blocksites
Step 3:- Now restart squid service
[root@hackthesec ~]# service squid restart
Step 4:- Try to access facebook.com in your browser . you could see the blocked page as below .
and check the log file you can see the facebook request is denied .
[root@hackthesec ~]# tail -f /var/log/squid/access.log ................................................................................. 1343820985.542 1 192.168.1.15 TCP_DENIED/403 4255 GET http://www.facebook.com/ - NONE/- text/html 1343820986.998 1411 192.168.1.15 TCP_MISS/200 13152 GET http://www.squid-cache.org/Artwork/SN.png - DIRECT/198.186.193.234 image/png 1343820987.004 0 192.168.1.15 TCP_DENIED/403 4178 GET http://www.facebook.com/favicon.ico - NONE/- text/html
Restricting Access to specific keywords :
Step 1:- create a file ( /etc/squid/blockkeywords.squid ) and add the keywords one per line.
[root@hackthesec ~]# cat /etc/squid/blockkeywords.squid
#blocked keywords
sex
porn
xxx
Step 2:- Open the /etc/squid/squid.conf and create a new acl "blockkeywords" and acl type "url_regex" in the acl section
acl Safe_ports port 488 # gss-http acl Safe_ports port 591 # filemaker acl Safe_ports port 777 # multiling http acl CONNECT method CONNECT # ACL blocksites acl blocksites dstdomain "/etc/squid/blockedsites.squid" # ACL blockkeywords acl blockkeywords url_regex -i "/etc/squid/blockkeywords.squid"
and add the following line "http_access deny blockkeywords" to http_section to deny the access to the acl "blockkeywords" .
# Recommended minimum Access Permission configuration: # # Only allow cachemgr access from localhost http_access allow manager localhost # Deny access to blocksites ACL http_access deny blocksites # Deny access to blockkeywords ACL http_access deny blockkeywords
Restricting Access to specific Ipaddress :
Step 1:- create a file ( /etc/squid/blockip.squid ) and add the ip adresses one per line.
[root@hackthesec ~]# cat /etc/squid/blockip.squid
#blocked ips
192.168.1.20
192.168.1.21
Step 2:- Open the /etc/squid/squid.conf and create a new acl "blockip" and acl type "src" in the acl section
acl Safe_ports port 488 # gss-http acl Safe_ports port 591 # filemaker acl Safe_ports port 777 # multiling http acl CONNECT method CONNECT # ACL blocksites acl blocksites dstdomain "/etc/squid/blockedsites.squid" # ACL blockkeywords acl blockkeywords url_regex -i "/etc/squid/blockkeywords.squid" # ACL blockip acl blockip src "/etc/squid/blockip.squid"
and add the following line "http_access deny blockip" to http_section to deny the access to the acl "blockip" .
# Recommended minimum Access Permission configuration: # # Only allow cachemgr access from localhost http_access allow manager localhost # Deny access to blockip ACL http_access deny blockip # Deny access to blocksites ACL http_access deny blocksites # Deny access to blockkeywords ACL http_access deny blockkeywords
Allow Full access to specific Ipaddress :
You can allow specific ip address to gain full access without blocking sites and keywords . just create a file "/etc/squid/allowip.squid" and add the ip address one per line and create an acl "allowip" and acl type "src" in the acl section
# ACL allowip acl allowip src "/etc/squid/allowip.squid"
and add the "allowip" in the http_access as below
# Recommended minimum Access Permission configuration: # # Only allow cachemgr access from localhost http_access allow manager localhost # Deny access to blockip ACL http_access deny blockip # Deny access to blocksites ACL http_access deny blocksites !allowip # Deny access to blockkeywords ACL http_access deny blockkeywords !allowip
Changing squid proxy port number:
You can change squid proxy port number , by default it uses 3128 port .
Just find the below line in "/etc/squid/squid.conf"
http_port 3128
and replace with
http_port 8000 # whatever port number you want
Restricting Download size :
You can restrict download file size using reply_body_max_size .
Add the below line at the bottom of the http_access section
#Restrict download size
reply_body_max_size 10 MB all
or
#Restrict download size
reply_body_max_size 10 MB !allowip
Configuring Squid as Transparent Proxy :
You can configure squid as transparent proxy .
Step 1:- just find the below line
# Squid normally listens to port 3128
http_port 3128
and replace with
# Squid normally listens to port 3128
http_port 3128 intercept
Step 2:- Create a file "/root/squidfw.sh" and add the following firewall script ( modify as per your interface configuration ).
#!/bin/sh # squid server IP SQUID_SERVER="192.168.1.11" # 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 $SQUID_SERVER:$SQUID_PORT # 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
Step 3:- just run the script
[root@hackthesec ~]# sh /root/squidfw.sh
and add the below line to "/etc/rc.local" to run the script during startup
sh /root/squidfw.sh
Step 4 (Updated):- Change default gateway ip to squid server ip on the user machines
Now users can access Internet without setting proxy in the browser settings.
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