Perfect Squid with Transparent proxy and SSL log

This will be a transparent SQUID proxy for your home or corporate network  ,  it  will transparently  intercept  all  traffic http and https  ,  for  https  you  will  need  to  push  to  clients  the CA certificate of the SQUID server, it  has  been tested to be working without problems with lastest Internet Explorer, Mozilla Firefox and Chrome browsers.

STEP 1 – Installing Base system , upgrading it and disabling IPtables , SeLINUX

We  start  by  downloading  the  CentOS  6.5  iso from CentOS website (x86 or x64) : CentOS 6.5 ISO’s , install Base system. Partitioning , software or hardware raid is up to the user. In this example hostname is : proxy.home.lan and ip address is : .

chkconfig iptables off
chkconfig ip6tables off
vi /etc/selinux/config

Press i , look for SELINUX= line and change it  to  SELINUX=disabled

Once you are done editing press ESC , then type :wq then pres ENTER.

Type into console :


Once the system is rebooted , type into console :

yum upgrade

STEP 2 – Enable EPEL repo, install SQUID

CentOS provided SQUID does not have ssl_crtd for some reason, thus it  cannot  be configured to generate certificates for https sites. Type the following into console :

cd /home
rpm -Uvh epel-release-6.8.noarch.rpm
cd /etc/yum.repos.d
vi SQUID.repo

Enter the following text into this file :

name=SQUID repo for CentOS Linux 6 - $basearch
#IL mirror

Once done we update the system again and install SQUID, type into terminal :

yum update
yum install perl-Crypt-OpenSSL-X509
yum install squid

Now we initialize SQUID ssl_db directory , type this into console :

/usr/lib/squid/ssl_crtd -c -s /var/lib/ssl_db
chown -R squid.squid /var/lib/ssl_db

* On the above state- I encountered problem, so had to do some tweaking,

First remove Squid and re-install using squid-helpers

yum remove squid
yum install squid-helpers 

Finally we edit our Squid config file to look like this :

acl localnet src
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
http_access deny !Safe_ports
http_access deny CONNECT !SSL_ports
http_access allow all
http_port 3130
http_port 3128 intercept
https_port 3129 intercept ssl-bump generate-host-certificates=on dynamic_cert_mem_cache_size=4MB cert=/etc/squid/ssl_cert/myca.pem key=/etc/squid/ssl_cert/myca.pem
#always_direct allow all
ssl_bump server-first all
#sslproxy_cert_error deny all
#sslproxy_flags DONT_VERIFY_PEER
sslcrtd_program /usr/lib/squid/ssl_crtd -s /var/lib/ssl_db -M 4MB
sslcrtd_children 8 startup=1 idle=1
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
shutdown_lifetime 1 second

STEP 3 – Generate Certificate for SQUID using OpenSSL

We will first edit our /etc/pki/tls/openssl.conf file , and alter only the following

default_days    = 1365           # How long to certify for
[ req_distinguished_name ]
countryName                     = Country Name (code)
countryName_default             = DE
countryName_min                 = 2
countryName_max                 = 2

stateOrProvinceName             = State or Province Name (full name)
stateOrProvinceName_default     = NRW

localityName                    = Locality Name (eg, city)
localityName_default            = Paderborn

0.organizationName              = Organization Name (eg, company)
0.organizationName_default      = Home.LAN

# we can do this but it is not needed normally :-)
#1.organizationName             = Second Organization Name (eg, company)
#1.organizationName_default     = World Wide Web Pty Ltd

organizationalUnitName          = Organizational Unit Name (eg, section)
organizationalUnitName_default  = Proxy Server

commonName                      = Common Name (eg, your name or your server's hostname)
# (Very Important, in order to keep mail clients and other user agents from complaining, this name must
# match exactly the name that the user will be entering into their client settings.  Whether that be
# domain.extension or mail.domain.extension or what.  It must be a valid DNS name pointing at your
# server.
commonName_default              = proxy.home.lan   # this line you need to add
commonName_max                  = 64

emailAddress                    = Email Address
emailAddress_default            = robert@proxy.home.lan  # this line you need to add
emailAddress_max                = 64

Once this is done we go to SQUID directory , create the certificate folder and generate the keys :

mkdir /etc/squid/ssl_cert
chown -R squid.squid /etc/squid/ssl_cert
cd /etc/squid/ssl_cert

For SQUID server the key :

openssl req -new -newkey rsa:1024 -days 1365 -nodes -x509 -keyout myca.pem -out myca.pem

For Windows clients the key :

openssl x509 -in myca.pem -outform DER -out myca.der

STEP 4 – install our own DNS server

Enter the following into console :

yum install bind

Then we go and modify the /etc/named.conf to look like this :

// named.conf
// Provided by Red Hat bind package to configure the ISC BIND named(8) DNS
// server as a caching only nameserver (as a localhost DNS resolver only).
// See /usr/share/doc/bind*/sample/ for example named configuration files.

acl mynet {; # test network; # localhost

options {
    listen-on { 
    listen-on-v6 port 53 { ::1; };
    directory     "/var/named";
    dump-file     "/var/named/data/cache_dump.db";
        statistics-file "/var/named/data/named_stats.txt";
        memstatistics-file "/var/named/data/named_mem_stats.txt";
    allow-query     { mynet; };
    recursion yes;

   forward only;
    forwarders {;

    dnssec-enable yes;
    dnssec-validation yes;
    dnssec-lookaside auto;
    /* Path to ISC DLV key */
    bindkeys-file "/etc/named.iscdlv.key";
    managed-keys-directory "/var/named/dynamic";

logging {
        channel default_debug {
                file "data/";
                severity dynamic;

zone "." IN {
    type hint;
    file "";

include "/etc/named.rfc1912.zones";
include "/etc/named.root.key";

#    home.lan

zone "home.lan" IN {
    type master;
    file "/var/named/home.lan/db.home";
    allow-query {

Type this into terminal :

mkdir /var/named/home.lan
touch /var/named/home.lan/db.home
chown -R named.named /var/named/home.lan

Then we add the following to the file /var/named/home.lan/db.home

$ORIGIN home.lan.
$TTL 86400
@    IN    SOA    proxy.home.lan.    proxy.home.lan. (
    2014032801 ; Serial
    28800 ; Refresh
    7200 ; Retry
    604800 ; Expire
    86400 ; Negative Cache TTL
@    IN    NS    proxy.home.lan.
proxy    IN    A

Next we make sure that both SQUID and NAMED are automatically started every time we reboot. Type this into terminal :

chkconfig squid on
chkconfig named on
/etc/init.d/named start
/etc/init.d/squid start

Then we alter /etc/resolv.conf to use local DNS server :

search localdomain home.lan


Since we are issuing certificates with this machine it is highly recommended to sync it’s time with our  internal NTP server or a external one. We can setup a cronjob for it like this :

vi /home/timesync
Then add the following into this file :

0 3,9,15,21 * * * /usr/sbin/ntpdate -u

And finally we add it to the crontab like this

crontab /home/timesync

This way it will sync the time regularely with our own internal or in this case with this external NTP server.

STEP 5 – Redirect HTTP and HTTPS traffic on our router to Proxy

On our router we add the following rules to IPtables :

iptables -t nat -A PREROUTING -p tcp -s --dport 80 -j DNAT --to
iptables -t nat -A PREROUTING -p tcp -s --dport 443 -j DNAT --to

STEP 6 – Client Configuration

We need to copy the /etc/squid/ssl_cert/myca.der file to our Windows  clients  ,  we  can  use  WinSCP  .  Installation  and configuration  is  straightforward  so  I wont go into detail here .

For Internet Explorer :

Tools -> Internet Options -> Content -> Certificates Click on Import , select  myca.der file , make sure that you import to Root Trusted Certificates  ,  close  down the browser and try for example.

For Mozilla Firefox :

Tools-> Options-> Advanced -> Certificates – > View Certificates
(x) Trust this CA to identify websites
(x) Trust this CA to identify email users
(x) Trust this CA to identify software developers

Click OK you are done.

For Google Chrome same as Internet Explorer.

There’s a good tutorial on installing SARG a squid report generation program in perl. The link is below-

NOTE : If the main certificate expires for SQUID , and you generate a  new  one ,  don’t  forget  to  delete  the  old  certificates  , /var/lib/ssl_db/certs also empty the file /var/lib/ssl_db/index.txt , and set the number inside the file /var/lib/ssl_db/size to 0 .



2 thoughts on “Perfect Squid with Transparent proxy and SSL log

    • Yhese are quick installation processes. SELinux most of the time does some protection where expected system might not work. For quick around, I usually disable it. ANywone who’d be using system for production grade, should keep it enable it. Thanks.

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