Squid proxy server

Squid是基于Unix的代理服务器(proxy server)，支持缓存多种不同的网络对象，包括那些通过HTTP和FTP访问的对象。缓存频繁访问的网页、媒体文件等，实现加速应答时间并减少带宽堵塞。Squid通过追踪网络中的对象来实现作用。Squid最初担当中介，仅仅是把客户请求传递到服务器并存储请求对象的副本。如果同一个用户或同一批用户再次请求还缓存(cache)在Squid中的相同对象时，Squid能够立即服务，加速下载并保存带宽。Squid代理服务器提供更快的下载速度、缩短延迟时间，尤其是在提供丰富媒体和流式视频方面。网站经营者将频繁地把Squid代理服务器作为内容加速器、频繁查看内容的缓存和网络服务器的容位负载。内容发布网络和媒体公司会采用Squid代理服务器，并在整个网络中部署它们来改善浏览者的访问体验，特别是对流式内容的负载平衡(load balancing)和处理访问高峰等方面的优化有显著效果。
Squid can proxy http ftp ssl protocol.
Effect:Proxy server helps client users to gets and cache the data from targeted host. Realize more fast and more secure what access web protal.

Web proxy server operating principle

Cache web element object(static text,picture),reduce multiple request.
1. Forward Proxy(SNAT)
2. Reverse Proxy(DNAT)
Achieve firewall function via domain name limit(application layer).
Forward proxy:
1. Typical proxy: need setup proxy’s ip and port by manual in the browser.
2. Transparent proxy: host gateway IP assign to proxy server

Squid features

Software:squid-3.1.10-1.e16_2.4.X86_64
Service:squid
Configure file:/etc/squid/squid.conf
Squid control module store dirextory: /usr/lib64/squid/
Config option:

http_port     squidServerIP:3128
cache_mem     64 MB     #one half as cache(64MB) when the mem > 2G
cache_dir    nfs        /var/spool/squid    100        16        256
        #100 -->  Total disk space < 100M
        #16  -->  Total directory < 16
        #256 --> Total level2 directory in the level1 directory
visible_hostname    proxy.fan.com   #if have not hostname and this option, the proxy server can not start.
dns_testnames    www.baidu.com
reply_body_max_size    10 MB     #forbid download the file when the file size greater than 10MB
minimum_object_size    0kb         #don't cache data when the data count less than Xkb, 0 the meaning is no limit.
maximum_object_size 4096kb     #don't cache date when the data greater than Xkb

ACL list control mode.
1. Format:

acl    listName listType listContent
http_access  allow/deny  listName
http_access  allow/deny  "url"   #import url of ACLlist file,Create file for store ACLList when the ACLList have too much.

Example:Deny cache web paper

acl deny php,...
cache_deny:deny php

Acl list type:

src:source address     #Can define network segment example:IP or continuous IP. 192.168.1.10-192.168.1.20/24
dst:destination address
port:destination port
srcdomain:source domain
dstdomain:destination domain
time:access time,general the parameter is range, example:09:30-17:30
maxconn:max concurrency connect
url_regex:destination url address, example : ^rtsp://     #Beginning with this type
urlpath_regex:complete destination url path, example: -i Sex adult

Setup squid server

step1. General squid

yum install -y squid

step2. Edit configuration file
vim /etc/squid/squid.conf

http_port 10.20.0.210(proxyServerIP):3182
reply_body_max_size 10MB
cache_dir    nfs        /var/spool/squid    100        16        256
visible_hostname  proxy.fan.com

Attention:Frist make DNS analysis as IP in the client then send the data package to squid server, but squid do not proxy DNS server, so should be setup SDNA and use it to connect DNS in the squid server.

Setup transparent proxy

Transparent proxy can’t support 443 port
step1.Edit config file
vim /etc/squid/squid.conf

http_port ServerIP:3128        transparent

step2. Set the iptables rules

iptables -t nat -A PREROUTING -i eth1 -s 192.168.4.0/24 -p tcp --dport 80 -j REDIRECT --to-port 3128

Attention:

iptables -t nat -A PREROUTING -i eth1 -s 192.168.4.0/24 -p tcp --dport 443 -j REDIRECT --to-port 3128
#Will 80 port access session assign to squid server's 3128 port, resolve way is use the SNAT.

step3. Set the ACL rules

acl worktime time D 9:00-17:30
acl burl urlpath_regex -i game \.mp3$
http_deny burl
http_access allow localnet worktime

Squit authentication

Transparent proxy don’t use authentication ,but the classical proxy can.
step1. Add authentition module.

/usr/lib64/squid/ncsa_auth --> authentication mudule

step2. Set authentication parameter in the main config file.
step3. Set authentication ACL

acl auth_user proxy_auth REQUIRED
http_access allow auth_user

step4. Create authentication account
vim squid.conf

acc auth_user proxy_auth REQUIRED
http_access auth_user
auth_param basic program /usr/lib64/squid/ncsa_auth /etc/squid/auth_user.txt   #Frist line in the config file. Specify user list file for ncsa_auth authentication module

htpasswd -c /etc/squid/auth_user.txt jmilk    #create user list file, you have to install httpd service to use command htpasswd
cat /etc/squid/auth_user.txt

vim /etc/squid/squid.conf

auth_param basic children 5 --> deal with 5 concurrent authentication 
auth_param basic realm Squid proxy-caching web  --> welcome page
auth_param basic credentialstt2 2 hours  --> timeout

step5. Set the speed limit for every IP.

delay_pools 1   #relay pool number
delay_class 1 3
            #1 --> relay pool number
            #3 --> specify network type to B;1: one IP;2:type C;3:type B;4: type A
delay_access 1 allow localnet      #usr acl:localnet
delay_parameters 1 -1/-1 20000/20000(byte)
            #-1/-1  --> all network segment
            #20000/20000 --> no limit download speed before 200M/speed limit beyond 200M

Setup the Reverse Proxy Server

Web 服务器容易出现负载瓶颈，有下面解决办法
1. Web服务器集群
2. 使用反向代理服务器
反向代理服务器：类似DNS以缓存的方式，减轻web server的压力
Listen 80
no set ACL, allow all
step1.
vim squid.conf

http_port ProxyServerIP:80 vhost
cache_peer WebServerIP parent 80 0 originserer
http_access allow

Case: set the transparent proxy

vim squid.conf

http_port squidServerIP:3128 transparent
visible_hostname transparent.fan.com
cache_dir ufs /var/spool/squid 100 16 256
cache_mem 1024 MB

对超过3MB大小的文件不做缓存，禁止下载超过100M的文件

maximum_object__size 3 MB
reply_body_max_size 100 MB

启用网址过滤，禁止访问带有”Sex”,”adult”字样的链接

acl burl urlpath_regex -i Sex adult
        #-i --> key word
http_access deny burl

配置Squid使用基本的身份认证，并且创建用户jmilk，只有通过身份认证后才可以使用squid上网。(透明代理不支持，只有传统代理支持)
vim squid.conf

acl auth_user proxy_auth REQUIREP|-i userName     #支持所设定的用户|支持用户列表
http_access allow auth_user
htpasswd -c /etc/squid/auth_user.txt jmilk
cat /etc/squid/auth_user.txt