Tag Archives: distribution

Browser Auto-config and Wpad deployment

Using a Proxy Server in your Company’s Network is one of the best decisions you have made.
But this decision can bring you some administration overhead if you don’t have an automatic way to provision the browser settings.
Fortunately, for Microsoft Operating Systems there is a way to accomplish this.
The procedure involves a configuration file that tells browsers how to connect to Internet.
This file is published via the existing Infrastructure using DNS, DHCP and a WEB Server.

Create the configuration file

Create the wpad.dat file inserting the following text:
function FindProxyForURL(url, host) {
return "PROXY 192.168.100.10:3128; DIRECT";
}

IIS

Create a new website and link it to a folder of your choice, (for instance c:\wpad). Place the wpad.dat file inside the folder.
Create a mime type for the .dat  file type with the mime type  “application/x-ns-proxy-autoconfig”.
Restart IIS. If you already have an IIS just place the file in the root directory.

Apache:

Create the wpad.dat file on the www directory depending on your distribution (on a Debian is /var/www/).
For instance:
#nano /var/www/wpad.dat
would open the nano editor. If nano is not install use vi or mcedit or any other text editor.
Edit httpd.conf:
#nano /etc/apache/httpd.conf
and insert the following line:  
AddType application/x-ns-proxy-autoconfig .dat

Make sure apache daemon is starting at boot time, (update-rc.d  apache2 defaults)
Restart apache #/etc/init.d/apache2 restart.

DHCP – Configuration for Proxy Auto discovery

(on a Microsoft DHCP server)

  1. Click Start, point to All Programs, point to Administrative Tools, and then click DHCP.
  2. In the console tree, right-click the applicable DHCP server, click Set Predefined Options, and then click Add.
  3. In Name, type WPAD.
  4. In Code, type 252.
  5. In Data type, select String, and then click OK.
  6. In String, type http://internalserver/wpad.dat where:
    • internalserver is the domain name of the Server that hosts the wpad.dat file. (Alternatively you can use fully qualified domain name, (eg. http://internalserver.domain.local:3129/wpad.dat)
    • Port is the port number on which automatic discovery information is published. You can specify any port number. I put 3129.
  7. Right-click Server options, and then click Configure options.
  8. Confirm that Option 252 is selected.

If you configure this on a Unix DHCP server you might need to add an extra blank character at the end of the DNS Configuration
Create an alias (CNAME) with the name wpad pointing at the webserver that hosts your wpad.dat file. For instance the alias is wpad and the fully qualified domain name is internalserver.domain.local

Troubleshooting

WPAD alias DNS entry not responding
After creating your alias when you ping wpad you get host not found this could be related to a security improvement on Microsoft’s DNS servers.
To fix this you need to edit the following registry value: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\DNS\Parameters\GlobalQueryBlockList
Edit this on all of your Microsoft DNS servers and remove wpad from the list of values. See the image below:

Registry Fix for Implementation of WPAD

Note that this configuration requires you or your user to configure your browser to “Automatically Detect Settings”.
For Internet Explorer this can be automatically configured for all the users in an Active Directory domain via a Group Policy.
The same policy will be used by Google Chrome, which uses the Windows Internet Connection configuration.
Other browsers such as Opera, and Mozilla will have to be manually configured. Alternatively, for an automatic configuration they can be tweaked via registry hacks or configured via third party software.
The disadvantage with manual configuration is of course the cost of deployment and the fact that this can be changed by the user. If you want to enforce the use of the proxy you have to restrict the gateway access and allow only the proxy machine to access it. Another way would be to configure your proxy to be your router and set up a transparent proxy.

How to Install Squid with Active Directory Authentication on Debian

How to Install Squid with Active Directory Authentication on Debian

Squid is a caching proxy software, licensed under GNU GPL, (free software).
It can help your Organization to reduce bandwidth and improves response times by caching and reusing frequently-requested web pages.
Squid has extensive access controls and if you don’t mind Command Line Interface is not too hard to configure. It runs on most available operating systems including Windows.
The following article is a step by step HOW TO Install Squid on Debian. Most of the steps are easily applicable to any other Linux distribution such as: RedHat, Suse, Ubuntu, etc…

Hardware requirements

Choose the machine wisely – if you are running a 50 computers Network a PIII should be enough provided that all you do is Web Caching and Filtering.
The memory is the most important and after that the disk speed. If you plan your proxy for a bigger Network you should consider using SCSI drives or SAS, and a faster CPU.
Memory requirements are explained later in the document.

Package Installation

Instal Debian minimal. The install cd, (only 650Mb) should be enough for this.
Reboot after installing and add packages with Aptitude (grafical interface) or "apt-get install program".
Add the following packages:
Openldap
Samba
Kerberos apt-get install krb5-{admin-server,kdc}
PAM apt-get install libpam0g-dev
Squid
Apache if you want proxy Auto-Configuration apt-get install apache2
Dansguardian if you need advanced WEB filtering
SARG if you want a log analyzer for your WEB access/filter

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Configure Samba

Samba is going to be used for authentication.
Note that if you run squid in transparent mode the authentication will not work.

#nano -w /etc/samba/smb.conf

Add or remove daemons to autostart
#update-rc.d  winbind defaults
#update-rc.d  samba defaults

– – – – – – – – – – – – – – – – – – – – – –
[global]
netbios name = proxy
realm = SUBDOMAIN.DOMAIN.ROOT
workgroup = SUBDOMAIN
security = ADS
password server = server1.subdomain.domain.root server2.subdomain.domain.root
socket options = TCP_NODELAY SO_RCVBUF=8192 SO_SNDBUF=8192
idmap uid = 10000-20000
domain master = no
local master = no
preferred master = no
winbind enum groups = yes
winbind enum users = yes
winbind uid = 10000-20000
winbind gid = 10000-20000
winbind separator = +
winbind use default domain = Yes
encrypt passwords = yes
log level = 5 passdb:5 auth:10 winbind:5
server string = proxy
dns proxy = no
log file = /var/log/samba/log.%m
max log size = 1000
syslog only = no
syslog = 0
encrypt passwords = true
load printers = no

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Do not add other parameters to the configuration file as they are not needed.
You can always tweak your configuration file later on if you need additional tweaking. If you do need further modifications do one at a time and test it extensively before release to production.
After editing smb.conf run the following command
# testparm
This will test your samba configuration file against any errors.
If there are no errors restart samba:
proxy:~# /etc/init.d/samba restart
proxy:~# /etc/init.d/winbind start
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Add the server to the domain
#net ads join "Ottawa Computers/Servers" -U Administrator -S server1.sub-domain.domain.edu
If you have Windows 7 you might get this in your /var/log/samba/log.wb: "NTLM CRAP authentication for user returned NT_STATUS_INVALID_PARAM"
If you get it follow the instructions below to tell Windows to use NTLM version1. Note that this is a security downgrade and it opens the door for an SMB man-in-the-middle attack. Asses the risks and the advantages before you do the change.

Run local GP on W7 gpedit.msc and look for:
Local Policies Security Options Network security: LAN Manager authentication level
Change from "Not Defined" to "LM & NTLM – Use NTLMv2 session if negotiated"
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Configure Squid

Make a backup copy of the default configuration file:
# cp /etc/squid/squid.conf /etc/squid/squid.conf.original
Edit the file squid.conf:
#nano –w /etc/squid/squid.conf
Replace everything in the file with the below text:

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#Proxy configurationuration - /etc/squid.squid.conf

# AUTHENTICATION
# -----------------------------------------------------------------------------
auth_param ntlm program /usr/bin/ntlm_auth --helper-protocol=squid-2.5-ntlmssp
auth_param ntlm children 30
auth_param basic program /usr/bin/ntlm_auth --helper-protocol=squid-2.5-basic
auth_param basic children 5
auth_param basic realm Squid Proxy Server
auth_param basic credentialsttl 2 hours
acl authenticated_users proxy_auth REQUIRED
http_access allow authenticated_users
auth_param ntlm keep_alive on

# ACCESS CONTROLS
# -----------------------------------------------------------------------------
#Deafult acl’s
acl all src all
acl manager proto cache_object
acl localhost src 127.0.0.1/32
acl to_localhost dst 127.0.0.0/8

#Declare your local network and any additional subnets
acl localnet src 192.168.100.0/24                # RFC1918 possible internal network
#acl remotesite src 192.168.200.0/24

#You would like that some of the users to be excluded from the logging.
###acl bosses src 192.168.100.255/30
###log_access deny bosses

#Tell Squid to not log google.ca
#Define the acl for google using regex
acl google url_regex ^http://www.google.ca
#Deny logging the acl
log_access deny google

#Allow the access for your localnet.
http_access allow localnet
#http_access allow remotesite

#Define allowed ports
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

http_access allow manager localhost
http_access deny manager
http_access allow purge localhost
http_access deny purge
http_access deny !Safe_ports
http_access deny CONNECT !SSL_ports
http_access allow localnet
http_access allow localhost

# And finally deny all other access to this proxy
http_access deny all

# NETWORK OPTIONS
# -----------------------------------------------------------------------------
http_port 3128

# MEMORY CACHE OPTIONS
# -----------------------------------------------------------------------------
#The memory needed for caching used files. The more you have the faster works. (No disk access.)
cache_mem 256 MB
#Objects bigger than this should be stored on the hard-drive. This can be lower than 8kb if your server has little memory.
maximum_object_size_in_memory 8 KB

# DISK CACHE OPTIONS
# -----------------------------------------------------------------------------
#Make sure you have enough space. And mount this on a fast disk or a raid0.
##cache_dir ufs /var/squid/cache 1000 16 256
cache_dir diskd /var/squid/cache 500 16 256

#This is extremely useful if your users download big files. You can even increase this depending on usage.
maximum_object_size 40960 KB

# LOGFILE OPTIONS
# -----------------------------------------------------------------------------
#This logging format includes the date the address requested the IP address of the requestor and the AD user who made the request.
#Human resources need to know what your users browse during the workday.
logformat squid %tl %6tr %>a %Ss/%03Hs %<st %rm %ru %un %Sh/%<A %mt
#Where to store all of this data.
access_log /var/log/squid/access.log squid

# ADMINISTRATIVE PARAMETERS
# -----------------------------------------------------------------------------
cache_mgr admin@mycompany.net
mail_from squid@ mycompany.net
visible_hostname proxy

# DNS OPTIONS
# -----------------------------------------------------------------------------
##You have the option to use the ISP’s DNS here
# dns_nameservers 10.0.0.1 192.168.0.254
hosts_file /etc/hosts
uri_whitespace allow
http_access deny all

#### --- End of the configuration file --- ####

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Run the command squid –z to let squid create the necessary directories.
#squid –z
Add the squid daemon to auto-startup, on a Debian machine the command is: 
#update-rc.d  squid defaults
Start squid
#/etc/init.d/squid start

Suggestion:
Test squid without authentication first. If this works go to the next step.
To test without authentication, comment all of the parameters in the Authentication section by adding the “#” sign at the beginning of line and restart squid.

Add or remove daemons to autostart
cd /etc/init.d/
update-rc.d  winbind defaults
update-rc.d -f apache2 remove

Tweaking performance on SQUID

A few settings that can dramaticaly improve the performance on your proxy:

cache_dir ufs /var/spool/squid 1000 50 256
This is the default Squid storage type configuration.
Change the storage type from ufs to aufs if using a Linux or variants.
Change the storage type from ufs to diskd if using BSD or variants.
If you use Windows, is probably for testing purposes, or because you don’t have a machine. Once the testing is done change to Linux or BSD.
The numeric parameters are:
First parameter is the amount of disk space in Mbytes to be used by Squid. The more you use the more physical memory (RAM) you need for indexes in order to be effective.
The rule is that you need
If you want to use the whole drive’s, (partition), space make sure you subtract 20% and use that value. In other words you can only use 80% of the drive.
The second and third parameters are the number of first and second level subdirectories that are created.

cache_mem 64 MB
The more memory you have the better it performs. Local, (cached), objects are much faster to retrieve than external ones.
The more local objects you can store the faster Squid responds.
Squid uses cache for many things other than memory cache, so make sure you have enough memory left when you configure cache_mem.

Memory cache is better for speed than disk, but is lost more easily and you can get bigger cache total spending RAM on indexes.

maximum_object_size 20480 KB
Today’s Internet usage contains has a lot of traffic in the 2MB to 200MB range. This traffic is comprised of multimedia objects, update files, etc.
You need to investigate your traffic and see what is a good number for you.

maximum_object_size_in_memory 64 KB
If you have little memory keep the default 8 KB. It is better to serve more fast pages from memory than a few slow pages that will run faster.

Check if your proxy works and if is logging properly the access.
On your proxy machine run the following command to see realtime access on the proxy: tail -f /var/log/squid/access.log On a client computer open the browser of your choice and change Networking options so that the browser uses the newly installed proxy.
Start to browse and look on the proxy’s console to see your activity logged.