Project on squid proxy in rhel 6

Squid Proxy in RHEL 6

PRIYANATH BARIK
Under Guidance OF
ER. Nutan Kumar Panda


What is Linux?
Linux is a high-level operating system based on UNIX. It was originally
created by Linus Torvalds. Linux has over-come Apple in the race to gain 2nd
place in the OS market share. While Linux has been around since the early
1990's, it has only recently gained popularity and attention. In early 2000,
Linux began to open eyes as I.T. projects began to test the value of the Linux
OS. Most of the world's websites are run on Linux or UNIX. Red Hat is the
leader of the Linux distribution serving 1,465,310 hostnames according to
Netcraft. All Linux articles on this site are produced using Red Hat products.

What Can Linux Do?
Linux is a high-level operating system just as Windows XP or UNIX. Linux is
deployed all over the world in businesses and mission-critical environments such as
hospitals, research centers, financial institutions, and more. While Linux is primarily
used to run servers, several distributions of Linux are aimed towards satisfying
desktop/workstation users. Distributions from Novell and Fedora are geared towards
production and end user environments. Linux supports all current hardware such as
the Athlon 64 and legacy devices for compatibility on older systems.

Specification in RHEL 6:

Power management – tickless kernel and improvements through the
application stack to reduce wakeups, power consumption measurement by
Powertop, Power Management (ASPM, ALPM), and adaptive system tuning
by Tuned, all enhance more efficient system power usage.
Next generation networking – comprehensive IPv6 support (NFS 4, CIFS,
mobile support [RFC 3775], ISATAP support), FCoE, iSCSI, and a new and
improved mac 802.11 wireless stack.
Scalable filesystems – ext4 file system provides support for larger file sizes
and significantly reduces repair times over ext3. XFS® is a high-performance
file system that supports extremely large files and is optimized for large
data transfers.
Virtualization – KVM includes performance improvements and new
features, sVirt protects the guest and host from unauthorized access, SR-
IOV and NPIV deliver high-performance virtual use of physical devices, and
libvirt leverages kernel resource management functionality.
Enterprise security enhancement – SELinux includes improved ease of use,
application sandboxing, and significantly increased coverage of system
services, while SSSD provides unified access to identity and authentication
services as well as caching for off-line use.
Development and runtime support – SystemTap improvements, ABRT is a
new framework for simple collection and reporting of bug information, and

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improvements are made to GCC (version 4.4.3), glibc (version 2.11.1), and
GDB (version 7.0.1).

Red Hat 6 RHEL Installation
1. Select Install or upgrade an existing system option on Grub Menu

2. Choose a language

3. Choose a keyboard type

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4. Choose a installation media

5. Skip DVD media test (or select media test, if you want to test installation
media before installation)

6. Red Hat 6 graphical installer starts, select next

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7. Accept Pre-Release Installation

8. Select storage devices

9. Insert computer name

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10. Select time zone

11. Enter a password for root user

12. Select type of installationRead every options info carefully. And select
encrypting if needed and option to review and modify partition layout.

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13. Review partition layout
Modify if needed. Default setup with ext4 and LVM looks good for desktop machine.

14. Accept write changes to disc

15. Writing changes (creating partitions) to disc

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16. Configure boot loader options
Select device to install bootloader and check/create boot loader operating system
list.

17. Select softwares to install and enable repositories
This case we select Software Development Workstation and enable Red Hat Enterprise
Linux 6.0 Beta Repository and select Customize now.

18. Customize package selection
Select PHP and Web Server to installation.

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Select MySQL and PostgreSQL Databases.

Select set of Development tools like Eclipse IDE.

19. Checking dependencies for installation

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20. Starting installation process

21. Installing packages

22. Installation is complete
Click reboot computer and remove installation media.

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Red Hat 6 RHEL Finishing Installation
23. Selecting RHEL 6 from grub

24. Booting Red Hat 6

25. Red Hat 6 Welcome screen

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26. Create normal user

27. Setup date and time and keep up-to-date with NTP

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28. Login Red Hat 6 Gnome Desktop

29. Red Hat (RHEL) 6 Gnome Desktop, empty and default look

Proxy server
In computer networks, a proxy server is a server (a computer system or an
application) that acts as an intermediary for requests from clients seeking resources
from other servers. A client connects to the proxy server, requesting some service,
such as a file, connection, web page, or other resource available from a different
server. The proxy server evaluates the request according to its filtering rules. For
example, it may filter traffic by IP address or protocol. If the request is validated by
the filter, the proxy provides the resource by connecting to the relevant server and
requesting the service on behalf of the client. A proxy server may optionally alter the
client's request or the server's response, and sometimes it may serve the request
without contacting the specified server. In this case, it 'caches' responses from the
remote server, and returns subsequent requests for the same content directly.

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The proxy concept was invented in the early days of distributed systems as a way to
simplify and control their complexity. Today, most proxies are a web proxy, allowing
access to content on the World Wide Web.

Uses

A proxy server has a large variety of potential purposes, including:

To keep machines behind it anonymous, mainly for security.
To speed up access to resources (using caching). Web proxies are commonly
used to cache web pages from a web server.
To apply access policy to network services or content, e.g. to block undesired
sites.
To access sites prohibited or filtered by your ISP or institution.
To log / audit usage, i.e. to provide company employee Internet usage
reporting.
To bypass security / parental controls.
To circumvent Internet filtering to access content otherwise blocked by
governments.
To scan transmitted content for malware before delivery.
To scan outbound content, e.g., for data loss prevention.
To allow a web site to make web requests to externally hosted resources (e.g.
images, music files, etc.) when cross-domain restrictions prohibit the web site
from linking directly to the outside domains.

A proxy server that passes requests and responses unmodified is usually called a
gateway or sometimes tunneling proxy.

A proxy server can be placed in the user's local computer or at various points
between the user and the destination servers on the Internet.

A reverse proxy is (usually) an Internet-facing proxy used as a front-end to control
and protect access to a server on a private network, commonly also performing tasks
such as load-balancing, authentication, decryption or caching.

Types of proxy

Forward proxies

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A forward proxy taking requests from an internal network and forwarding them to the
Internet.

Forward proxies are proxies where the client server names the target server to
connect to.Forward proxies are able to retrieve from a wide range of sources (in
most cases anywhere on the Internet).

The terms "forward proxy" and "forwarding proxy" are a general description of
behavior (forwarding traffic) and thus ambiguous. Except for Reverse proxy, the
types of proxies described in this article are more specialized sub-types of the
general forward proxy concept.

Open proxies

An open proxy forwarding requests from and to anywhere on the Internet.

An open proxy is a forwarding proxy server that is accessible by any Internet user.
Gordon Lyon estimates there are "hundreds of thousands" of open proxies on the
Internet. An anonymous open proxy allows users to conceal their IP address while
browsing the Web or using other Internet services. There are varying degrees of
anonymity however, as well as a number of methods of 'tricking' the client into
revealing itself regardless of the proxy being used.

Reverse proxies

A reverse proxy taking requests from the Internet and forwarding them to
servers in an internal network. Those making requests connect to the proxy
and may not be aware of the internal network.

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A reverse proxy (or surrogate) is a proxy server that appears to clients to be an
ordinary server. Requests are forwarded to one or more origin servers which handle
the request. The response is returned as if it came directly from the proxy server.

Reverse proxies are installed in the neighborhood of one or more web servers. All
traffic coming from the Internet and with a destination of one of the neighborhood's
web servers goes through the proxy server. The use of "reverse" originates in its
counterpart "forward proxy" since the reverse proxy sits closer to the web server and
serves only a restricted set of websites.

There are several reasons for installing reverse proxy servers:

Encryption / SSL acceleration: when secure web sites are created, the SSL encryption
is often not done by the web server itself, but by a reverse proxy that is equipped
with SSL acceleration hardware. See Secure Sockets Layer. Furthermore, a host can
provide a single "SSL proxy" to provide SSL encryption for an arbitrary number of
hosts; removing the need for a separate SSL Server Certificate for each host, with the
downside that all hosts behind the SSL proxy have to share a common DNS name or
IP address for SSL connections. This problem can partly be overcome by using the
SubjectAltName feature of X.509 certificates.
Load balancing: the reverse proxy can distribute the load to several web servers, each
web server serving its own application area. In such a case, the reverse proxy may
need to rewrite the URLs in each web page (translation from externally known URLs
to the internal locations).
Serve/cache static content: A reverse proxy can offload the web servers by caching
static content like pictures and other static graphical content.
Compression: the proxy server can optimize and compress the content to speed up
the load time.
Spoon feeding: reduces resource usage caused by slow clients on the web servers by
caching the content the web server sent and slowly "spoon feeding" it to the client.
This especially benefits dynamically generated pages.
Security: the proxy server is an additional layer of defense and can protect against
some OS and WebServer specific attacks. However, it does not provide any
protection to attacks against the web application or service itself, which is generally
considered the larger threat.
Extranet Publishing: a reverse proxy server facing the Internet can be used to
communicate to a firewalled server internal to an organization, providing extranet
access to some functions while keeping the servers behind the firewalls. If used in
this way, security measures should be considered to protect the rest of your
infrastructure in case this server is compromised, as its web application is exposed to
attack from the Internet.

Performance Enhancing Proxies

A proxy that is designed to mitigate specific link related issues or degradations. PEPs
(Performance Enhancing Proxies) are typically used to improve TCP performance in
the presence of high Round Trip Times (RTTs) and wireless links with high packet loss.

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They are also frequently used for highly asynchronous links featuring very different
upload and download rates.

Uses of proxy servers

Filtering

A content-filtering web proxy server provides administrative control over the content
that may be relayed through the proxy. It is commonly used in both commercial and
non-commercial organizations (especially schools) to ensure that Internet usage
conforms to acceptable use policy. In some cases users can circumvent the proxy,
since there are services designed to proxy information from a filtered website
through a non filtered site to allow it through the user's proxy.

A content filtering proxy will often support user authentication, to control web
access. It also usually produces logs, either to give detailed information about the
URLs accessed by specific users, or to monitor bandwidth usage statistics. It may also
communicate to daemon-based and/or ICAP-based antivirus software to provide
security against virus and other malware by scanning incoming content in real time
before it enters the network.

Many work places, schools, and colleges restrict the web sites and online services
that are made available in their buildings. This is done either with a specialized proxy,
called a content filter (both commercial and free products are available), or by using
a cache-extension protocol such as ICAP, that allows plug-in extensions to an open
caching architecture.

Some common methods used for content filtering include: URL or DNS blacklists, URL
regex filtering, MIME filtering, or content keyword filtering. Some products have
been known to employ content analysis techniques to look for traits commonly used
by certain types of content providers.

Requests made to the open internet must first pass through an outbound proxy
filter. The web-filtering company provides a database of URL patterns (regular
expressions) with associated content attributes. This database is updated weekly by
site-wide subscription, much like a virus filter subscription. The administrator
instructs the web filter to ban broad classes of content (such as sports, pornography,
online shopping, gambling, or social networking). Requests that match a banned URL
pattern are rejected immediately.

Assuming the requested URL is acceptable, the content is then fetched by the proxy.
At this point a dynamic filter may be applied on the return path. For example, JPEG
files could be blocked based on fleshtone matches, or language filters could
dynamically detect unwanted language. If the content is rejected then an HTTP fetch
error is returned and nothing is cached.

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Extranet Publishing: a reverse proxy server facing the Internet can be used to
communicate to a firewalled server internal to an organization, providing extranet
access to some functions while keeping the servers behind the firewalls. If used in
this way, security measures should be considered to protect the rest of your
infrastructure in case this server is compromised, as its web application is exposed to
attack from the Internet

Most web filtering companies use an internet-wide crawling robot that assesses the
likelihood that content is a certain type. The resultant database is then corrected by
manual labor based on complaints or known flaws in the content-matching
algorithms.

Web filtering proxies are not able to peer inside secure sockets HTTP transactions,
assuming the chain-of-trust of SSL/TLS has not been tampered with. As a result, users
wanting to bypass web filtering will typically search the internet for an open and
anonymous HTTPS transparent proxy. They will then program their browser to proxy
all requests through the web filter to this anonymous proxy. Those requests will be
encrypted with https. The web filter cannot distinguish these transactions from, say,
a legitimate access to a financial website. Thus, content filters are only effective
against unsophisticated users.

As mentioned above, the SSL/TLS chain-of-trust does rely on trusted root certificate
authorities; in a workplace setting where the client is managed by the organization,
trust might be granted to a root certificate whose private key is known to the proxy.
Concretely, a root certificate generated by the proxy is installed into the browser CA
list by IT staff. In such scenarios, proxy analysis of the contents of a SSL/TLS
transaction becomes possible. The proxy is effectively operating a man-in-the-middle
attack, allowed by the client's trust of a root certificate the proxy owns.

A special case of web proxies is "CGI proxies". These are web sites that allow a user
to access a site through them. They generally use PHP or CGI to implement the proxy
functionality. These types of proxies are frequently used to gain access to web sites
blocked by corporate or school proxies. Since they also hide the user's own IP
address from the web sites they access through the proxy, they are sometimes also
used to gain a degree of anonymity, called "Proxy Avoidance".

Caching

A caching proxy server accelerates service requests by retrieving content saved from
a previous request made by the same client or even other clients. Caching proxies
keep local copies of frequently requested resources, allowing large organizations to
significantly reduce their upstream bandwidth usage and costs, while significantly
increasing performance. Most ISPs and large businesses have a caching proxy.
Caching proxies were the first kind of proxy server.

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Some poorly-implemented caching proxies have had downsides (e.g., an inability to
use user authentication). Some problems are described in RFC 3143 (Known HTTP
Proxy/Caching Problems).

Another important use of the proxy server is to reduce the hardware cost. An
organization may have many systems on the same network or under control of a
single server, prohibiting the possibility of an individual connection to the Internet
for each system. In such a case, the individual systems can be connected to one
proxy server, and the proxy server connected to the main server. An example of a
software caching proxy is Squid.

DNS proxy

A DNS proxy server takes DNS queries from a (usually local) network and forwards
them to an Internet Domain Name Server. It may also cache DNS records.

Bypassing filters and censorship

If the destination server filters content based on the origin of the request, the use of
a proxy can circumvent this filter. For example, a server using IP-based geolocation to
restrict its service to a certain country can be accessed using a proxy located in that
country to access the service.

Likewise, a badly configured proxy can provide access to a network otherwise
isolated from the Internet.

Logging and eavesdropping

Proxies can be installed in order to eavesdrop upon the data-flow between client
machines and the web. All content sent or accessed – including passwords submitted
and cookies used – can be captured and analyzed by the proxy operator. For this
reason, passwords to online services (such as webmail and banking) should always be
exchanged over a cryptographically secured connection, such as SSL.

By chaining proxies which do not reveal data about the original requester, it is
possible to obfuscate activities from the eyes of the user's destination. However,
more traces will be left on the intermediate hops, which could be used or offered up
to trace the user's activities. If the policies and administrators of these other proxies
are unknown, the user may fall victim to a false sense of security just because those
details are out of sight and mind.

In what is more of an inconvenience than a risk, proxy users may find themselves
being blocked from certain Web sites, as numerous forums and Web sites block IP
addresses from proxies known to have spammed or trolled the site. Proxy bouncing
can be used to maintain your privacy.

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Gateways to private networks

Proxy servers can perform a role similar to a network switch in linking two networks.

Accessing services anonymously

An anonymous proxy server (sometimes called a web proxy) generally attempts to
anonymize web surfing. There are different varieties of anonymizers. The destination
server (the server that ultimately satisfies the web request) receives requests from
the anonymizing proxy server, and thus does not receive information about the end
user's address. However, the requests are not anonymous to the anonymizing proxy
server, and so a degree of trust is present between the proxy server and the user.
Many of them are funded through a continued advertising link to the user.

Access control: Some proxy servers implement a logon requirement. In large
organizations, authorized users must log on to gain access to the web. The
organization can thereby track usage to individuals.

Some anonymizing proxy servers may forward data packets with header lines such as
HTTP_VIA, HTTP_X_FORWARDED_FOR, or HTTP_FORWARDED, which may reveal the
IP address of the client. Other anonymizing proxy servers, known as elite or high
anonymity proxies, only include the REMOTE_ADDR header with the IP address of
the proxy server, making it appear that the proxy server is the client. A website could
still suspect a proxy is being used if the client sends packets which include a cookie
from a previous visit that did not use the high anonymity proxy server. Clearing
cookies, and possibly the cache, would solve this problem.

Implementations of proxies

Web proxy

A web proxy passes along http protocol requests like any other proxy server.
However, the web proxy accepts target URLs within a user's browser window,
processes the request, and then displays the contents of the requested URL
immediately back within the users browser. This is generally quite different than a
corporate intranet proxy which some people mistakenly refer to as a web proxy.

Suffix proxy

A suffix proxy allows a user to access web content by appending the name of the
proxy server to the URL of the requested content (e.g.
"en.wikipedia.org.SuffixProxy.com"). Suffix proxy servers are easier to use than
regular proxy servers. But do not offer anonymity and the primary use is bypassing
web filters; however, this is rarely used due to more advanced web filters.

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Transparent proxy

Also known as an intercepting proxy or forced proxy, a transparent proxy intercepts
normal communication without requiring any special client configuration. Clients
need not be aware of the existence of the proxy. A transparent proxy is normally
located between the client and the Internet, with the proxy performing some of the
functions of a gateway or router.

RFC 2616 (Hypertext Transfer Protocol—HTTP/1.1) offers standard definitions:

"A 'transparent proxy' is a proxy that does not modify the request or response
beyond what is required for proxy authentication and identification".

"A 'non-transparent proxy' is a proxy that modifies the request or response in order
to provide some added service to the user agent, such as group annotation services,
media type transformation, protocol reduction, or anonymity filtering".

In 2009 a security flaw in the way that transparent proxies operate was published by
Robert Auger,and the Computer Emergency Response Team issued an advisory
listing dozens of affected transparent and intercepting proxy servers.

Purpose

Intercepting proxies are commonly used in businesses to prevent avoidance of
acceptable use policy, and to ease administrative burden, since no client browser
configuration is required. This second reason however is mitigated by features such
as Active Directory group policy, or DHCP and automatic proxy detection.

Intercepting proxies are also commonly used by ISPs in some countries to save
upstream bandwidth and improve customer response times by caching. This is more
common in countries where bandwidth is more limited (e.g. island nations) or must
be paid for.

Issues

The diversion / interception of a TCP connection creates several issues. Firstly the
original destination IP and port must somehow be communicated to the proxy. This
is not always possible (e.g. where the gateway and proxy reside on different hosts).
There is a class of cross site attacks which depend on certain behaviour of
intercepting proxies that do not check or have access to information about the
original (intercepted) destination. This problem can be resolved by using an
integrated packet-level and application level appliance or software which is then able
to communicate this information between the packet handler and the proxy.

Intercepting also creates problems for HTTP authentication, especially connection-
oriented authentication such as NTLM, since the client browser believes it is talking

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to a server rather than a proxy. This can cause problems where an intercepting proxy
requires authentication, then the user connects to a site which also requires
authentication.

Finally intercepting connections can cause problems for HTTP caches, since some
requests and responses become uncacheble by a shared cache.

Therefore intercepting connections is generally discouraged. However due to the
simplicity of deploying such systems, they are in widespread use.

Implementation methods

Interception can be performed using Cisco's WCCP (Web Cache Control Protocol).
This proprietary protocol resides on the router and is configured from the cache,
allowing the cache to determine what ports and traffic is sent to it via transparent
redirection from the router. This redirection can occur in one of two ways: GRE
Tunneling (OSI Layer 3) or MAC rewrites (OSI Layer 2).

Once traffic reaches the proxy machine itself interception is commonly performed
with NAT (Network Address Translation). Such setups are invisible to the client
browser, but leave the proxy visible to the web server and other devices on the
internet side of the proxy. Recent Linux and some BSD releases provide TPROXY
(transparent proxy) which performs IP-level (OSI Layer 3) transparent interception
and spoofing of outbound traffic, hiding the proxy IP address from other network
devices.

Detection

There are several methods that can often be used to detect the presence of an
intercepting proxy server:

By comparing the client's external IP address to the address seen by an
external web server, or sometimes by examining the HTTP headers received
by a server. A number of sites have been created to address this issue, by
reporting the user's IP address as seen by the site back to the user in a web
page.
By comparing the sequence of network hops reported by a tool such as
traceroute for a proxied protocol such as http (port 80) with that for a non
proxied protocol such as SMTP (port 25).
By attempting to make a connection to an IP address at which there is known
to be no server. The proxy will accept the connection and then attempt to
proxy it on. When the proxy finds no server to accept the connection it may
return an error message or simply close the connection to the client. This
difference in behaviour is simple to detect. For example most web browsers
will generate a browser created error page in the case where they cannot

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connect to an HTTP server but will return a different error in the case where
the connection is accepted and then closed.
By serving the end-user specially programmed flash files that send HTTP calls
back to their server.

Tor onion proxy software

The Vidalia Tor-network map.

Tor (short for The Onion Router) is a system intended to enable online
anonymity.Tor client software routes Internet traffic through a worldwide volunteer
network of servers in order to conceal a user's location or usage from someone
conducting network surveillance or traffic analysis. Using Tor makes it more difficult
to trace Internet activity, including "visits to Web sites, online posts, instant
messages and other communication forms", back to the user.It is intended to protect
users' personal freedom, privacy, and ability to conduct confidential business by
keeping their internet activities from being monitored.

"Onion routing" refers to the layered nature of the encryption service: The original
data are encrypted and re-encrypted multiple times, then sent through successive
Tor relays, each one of which decrypts a "layer" of encryption before passing the
data on to the next relay and ultimately the destination. This reduces the possibility
of the original data being unscrambled or understood in transit.

The Tor client is free software, and there are no additional charges to use the
network.

I2P anonymous proxy(Invisible Internet Project)

The I2P anonymous network ('I2P') is a proxy network aiming at online anonymity. It
implements garlic routing, which is an enhancement of Tor's onion routing. I2P is
fully distributed and works by encrypting all communications in various layers and
relaying them through a network of routers run by volunteers in various locations. By

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keeping the source of the information hidden, I2P offers censorship resistance. The
goals of I2P are to protect users' personal freedom, privacy, and ability to conduct
confidential business.

Each user of I2P runs an I2P router on their computer (node). The I2P router takes
care of finding other peers and building anonymizing tunnels through them. I2P
provides proxies for all protocols (HTTP, irc, SOCKS, ...).

The software is free and open-source, and the network is free of charge to use.

Squid Proxy:

Squid is a caching proxy for the Web supporting HTTP, HTTPS, FTP, and more. It
reduces bandwidth and improves response times by caching and reusing frequently-
requested web pages. Squid has extensive access controls and makes a great server
accelerator. It runs on most available operating systems, including Windows and is
licensed under the GNU GPL.

Making the most of your Internet Connection

Squid is used by hundreds of Internet Providers world-wide to provide their users
with the best possible web access. Squid optimises the data flow between client and
server to improve performance and caches frequently-used content to save
bandwidth. Squid can also route content requests to servers in a wide variety of ways
to build cache server hierarchies which optimise network throughput.

Website Content Acceleration and Distribution

Thousands of web-sites around the Internet use Squid to drastically increase their
content delivery. Squid can reduce your server load and improve delivery speeds to
clients. Squid can also be used to deliver content from around the world - copying
only the content being used, rather than inefficiently copying everything. Finally,
Squid's advanced content routing configuration allows you to build content clusters
to route and load balance requests via a variety of web servers.

Configuring Server

After installation of RHEL 6 if you want to install some extra packages in Server then
all packages are available in the RHEL DVD. In Linux there are so many installer is
available but in default installer is RPM (Redhat Package Manager) and another
installer is YUM (Yellowdog Updater Modifier). If you want to use “rpm” command
then simple use rpm command but if you want to use “yum” then you must

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configure YUM Server. Before configuring YUM Server you must install FTP Server at
the time of package installation at the time of Linux installing. Here I am copy all the
contains of RHEL 6 DVD in /var/ftp/pub.

Installing Squid Proxy in RHEL 6:

 Package Required :- squid-stables
 Configuration Files :- /etc/squid/squid.conf
 Daemon :- squid

Step 1. Check if the package is installed or not

#rpm –qa | grep squid

Step 2. If not, then install it

#rpm –ivh /var/ftp/pub/squid
(i- install, v- verbose, h- progress bar of the installation)
OR

#yum install squid

Before changes something in conf file create a backup file of it.

Check the file

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Step 3. Edit the Configuration File (Giving the ACL/rules)
#vim /etc/squid/squid.conf

Search http_port_8080 (Give the port number where squid listen in 3128 port
No.)

Search “Insert your own rules here”

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Here you give your own rules. Like

acl<name1>src 192.168.1.0/24

http_access allow <name1>

Then save it.

Start the Squid Service

#service squid start

In client site configure the proxy settings in your Browser. Here I am using Mozilla
Firefox. In other Browser the settings are little bit changes. Settings of Mozilla Firefox
are given below.

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Start Mozilla Firefox-Tools-Options

Click on Advanced- Click on Settings

Click on Manual Proxy Configuration- Give the HTTP Proxy address
(192.168.1.1)- Give the Port No. (8080)

Then - OK -OK

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There are some ACL Elements are given below which are using in proxy configuration
files.

src: source (client) IP addresses
dst: destination (server) IP addresses
myip: the local IP address of a client's connection
arp: Ethernet (MAC) address matching
srcdomain: source (client) domain name
dstdomain: destination (server) domain name
srcdom_regex: source (client) regular expression pattern matching
dstdom_regex: destination (server) regular expression pattern matching
src_as: source (client) Autonomous System number
dst_as: destination (server) Autonomous System number
peername: name tag assigned to the cache_peer where request is expected
to be sent.
time: time of day, and day of week
url_regex: URL regular expression pattern matching
urlpath_regex: URL-path regular expression pattern matching, leaves out the
protocol and hostname
port: destination (server) port number
myport: local port number that client connected to
myportname: name tag assigned to the squid listening port that client
connected to
proto: transfer protocol (http, ftp, etc)
method: HTTP request method (get, post, etc)
http_status: HTTP response status (200 302 404 etc.)
browser: regular expression pattern matching on the request user-agent
header
referer_regex: regular expression pattern matching on the request http-
referer header
ident: string matching on the user's name
ident_regex: regular expression pattern matching on the user's name
proxy_auth: user authentication via external processes
proxy_auth_regex: regular expression pattern matching on user
authentication via external processes
snmp_community: SNMP community string matching
maxconn: a limit on the maximum number of connections from a single client
IP address
max_user_ip: a limit on the maximum number of IP addresses one user can
login from
req_mime_type: regular expression pattern matching on the request content-
type header
req_header: regular expression pattern matching on a request header content

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rep_mime_type: regular expression pattern matching on the reply
(downloaded content) content-type header. This is only usable in the
http_reply_access directive, not http_access.
rep_header: regular expression pattern matching on a reply header content.
This is only usable in the http_reply_access directive, not http_access.
external: lookup via external acl helper defined by external_acl_type
user_cert: match against attributes in a user SSL certificate
ca_cert: match against attributes a users issuing CA SSL certificate
ext_user: match on user= field returned by external acl helper defined by
external_acl_type
ext_user_regex: regular expression pattern matching on user= field returned
by external acl helper defined by external_acl_type

Conclusion
• Again, a Proxy Server is a medium in which users within the LAN can gain
access to the Internet efficiently and much more securely.

• It functions in two different ways: as a cache and as a firewall.

• It can also be implemented in different ways: as a dual-home host, as a
screened host, as a screened subnetwork, and as a reverse proxy.

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