Dungog-dansguardian

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Dansguardian, Web Content Filter

Users on your LAN can have their web browsing filtered, to block objectionable sites, to perform realtime virus scanning of browsing, or to satisfy a regulatory requirement. Filtering of web content is performed by the DansGuardian program.

A word from the Dan behind DansGuardian, Please read http://dansguardian.org/?page=copyright2 and register and/or pay and/or donate for DansGuardian as you feel appropriate.

Translations

The dansguardian panel is now translated into most SME languages, refer to Translations

ClamAV and Updates

Previous to dansguardian-2.10.0.3-4, when ClamAV was upgraded library versions could get out of sync, eg libclamav.so.2 to libclamav.so.3 gave yum update errors.

To solve this upgrade dansguardian to at least dansguardian-2.10.0.3-4

yum update --enablerepo=smecontribs dansguardian 
http://bugs.contribs.org/show_bug.cgi?id=5111

smeserver-dansguardian

This provides all the SME intergration to get dansguardian running,
you will need to hand edit the configuration files in /etc/dansguardian to suit. Documentation here http://wiki.contribs.org/Dansguardian should help.

yum install dansguardian smeserver-dansguardian

Alternatively you can purchase dungog-dansguardian

dungog-dansguardian

Provides a server-manager panel to help in the ongoing configuration. You can use existing or make new SME groups to give users different levels of Filtering.

Other Features include
Filter Groups are setout logically with each config file presented clearly
A special everybody group exist to save time enter the same site for each group
Enhanced denied access page alternatives are preconfigured for you
Enhanced regexp checks are given as check box options
Settings are saved in a SME Database to preserve changes during upgrades

yum install dungog-dansguardian [& optionally dungog-blacklists]

Access at \server-manager > dungog.net > Web Content Filter

Overview

DansOverview2.png

Global Settings

DansGlobal.png

Proxy Settings

DansProxy.png

Filter Group

When the proxy access method is set to Authenticate, a user is required to enter their user password before they can have access to the internet. Or you can use Ident to authenticate your users which does away with the need to login, NB. Ident can be misled by multiple logins on the same PC

With authenticated users you can filters users differently, This is set by creating SME groups. Select your SME groups on the server-manager dansguardian panel (with ncsa use the proxy-user panel) You can also make PC's banned or unfiltered by adding their IP address to the panel.

Users are part of the default filter group, until you create a 2nd filter group by selecting a group from the list of pre arranged SME groups.

To keep your setup uncomplicated you could use two groups. One group can be more restrictive and the other less restrictive.

An example of a restrictive group is one that has a blanket ban on all sites, then a white or grey list of allowed sites

A less restrictive group may have a high weighted phrase limit, and just blacklist sites with ads, porn and warez

Each filter group can have their own custom denied access page

Settings

DansFilterGroup1.png

Lists

DansFilterGroup2.png

Lists

Phraselists

Phrase lists are installed by default by DansGuardian

They are the brains behind dansguardian. These contain the phrases that are checked on each web page page. A large selection of lists are available but you have to enable them for each filter group, select modify next to each filtergroup, select phraselists from the table, and check the lists you wish to use.

You are encouraged to send feedback and forward any changes and additions that have general use to the Phraselist maintainer, he has a later set of phrases that you can manually install over the release version.

You can add separate phrases in the weighted/allow/deny records or create you own lists. Create your own lists by making a new directory

mkdir /etc/dansguardian/lists/phraselists/mylist

Three files can be used, but weighted must exist for the group the be recognised. weighted contains phrases that are scored and count towards the Weighted phrase limit banned contains phrases that cause the page to be denied exception contains phrases that allow the page to pass now add this list to the internal database, from the command line

db phraselist set mylist list 

where mylist is the name of your list & use your own description

There are over 30 lists, below is just the top of the page DansPhraselist2.png

Blacklists

You can if you wish install blacklists from mesd.k12.or.us or many other sources, including commercial lists like those available from Squidblacklist.org - Blacklists For Squid Proxy & More. You can download a rpm from dungog.net/sme or this can be updated or installed with rsync, run from the command line or add /usr/bin/rsync-sgbl to cron, weekly or monthly. (sgbl=squidguard blacklist) There is alternate commercial blacklist from URLBlacklist.com You select which individual black/white/greylists to use for each filter group.

Although this is called a blacklist, the categories can be used as white or grey lists also. Being listed does not infer that the site is bad - these are just lists of sites.

If you choose to use or trial the lists from blacklist .com, download the tgz file, uncompress and move to the /etc/dansguardian/blacklists directory.

You can create your own lists by making a new directory

mkdir /etc/dansguardian/blacklists/mylist

two files are used domains contains whole sites eg mysite.com urls contains parts of sites eg mysite/part now add this list to the internal database

db blacklist set mylist list 

where mylist is the name of your list & use your own description

DansBlacklist2.png

General Lists

DansLists2.png

Also see http://wiki.contribs.org/Dansguardian/ConfigFiles

  • Banned, Exception and Grey Lists

These lists can override other settings such as weighted phrase or blacklists. They either allow or deny a page depending on the settings. The grey lists override the banned lists. The exception lists override the banned lists also. The difference is that the exception lists completely switch off *all* other filtering for the match. Grey lists only stop the URL filtering and allow the normal filtering to work.

You add records to the default lists in the Lists Configuration page. If you have a lot records to add you can prepare a file and insert it into the template directory. You are prompted with the file name on each page.

You can use symbolic links to expose the site config file into an ibay for easier access, you must be sure that anyone who edits the file knows to use a unix file format.

  • Exceptionsitelist, Bannedsitelist, Greysitelist

Affects the hostname part of a URL eg yahoo.com or for finer control mail.yahoo.com You can affect everything from the .us domain with .us or allow all things australian by using just using .au

  • ExceptionURLlist, BannedURLlist, GreyURLlist

Affects the parts of a domain eg abc.net.au/children or bbc.co.uk/cricket will affect the childrens and cricket sections of the domains

  • Exceptionphraselist, Bannedphraselist, Weightedphraselist

While checking the contents of a page will block or allow if these phrases are found. This is slightly different to weighted phrases which scores the contents and won't have an affect until enough the set limit is reached.

A word or phrase is enclosed by < sex> angle brackets, a leading or trailing space inside the angle brackets is significant. eg [space]sex will not find middlesex

  • Exceptioniplist, Bannediplist

Affects a PC on the local network with that IP address, Note. SMEserver can assign a static IP based on a network card's MAC address via the hostname and addresses panel

  • Exceptionuserlist, Banneduserlist

Affects a user when the proxy access method is set to Pam Auth, see the next section for details, This is set by selecting a SME group.

  • Exceptionvirusmimetype, Exceptionvirusextension, Exceptionvirussitelist, Exceptionvirusurllist

When virus scanning of browsing is enabled these files or sites are not scanned

  • Bannedregexpurllist

Affects a URL that contains a pattern that is matched by a unix regular expression. This is very powerful but also difficult to understand and get right if you don't know your regular expression rules.

  • Bannedfileextlist

Common catagories of files have been grouped so you only need to check a box on the filter group page. You can ban other file types not included in that list.

  • Bannedmimetypelist

Affects files of a defined mime type

  • Greyurllist, Greysitelist

An example of grey list use is when in Blanket Block (whitelist) mode and you want to allow some sites but still filter as normal on their content. Another example of grey list use is when you ban a site but want to allow part of it.
The greyurllist is for partly unblocking PART of a site
The greysitelist is for partly unblocking ALL of a site

Access Denied

When a page is blocked the denied usage screen is displayed. The details of why the page was blocked can be brief or detailed depending on the settings.

The override bypass link is shown if the user is authenticated, the reporting level is set to report details and the bypass link is enabled in the filtergroup

Each filter group can have their own denied access page

DansDenied.png

The denied access page can be stripped down to the bare minimum, x (blocked) + (bypass)

This version is available in the next release 2.9.9.1 with

db dungog setprop dansguardian deniedurl yourserver.net/cgi-bin/denied.pl 

DansDenied2.png

Proxy Access and Browser Setup

ldap

Authenticate against an LDAP server

BETA, from dungog-dansguardian-2.9-19

Tested with ldap on SME, may need refinement with MS Active Directory

This isn't 'Single Sign On'. The user is prompted for their LDAP/AD username and password. If users tick remember and save password this is only a small inconvenience.

Two tests need to be run to verify your LDAP settings and two db settings saved.

The settings are your ldap server hostname.domainname, just an IP will do

config setprop squid host ldap://k8.232.net

And your ldap server Distinguised Name

config setprop squid dn dc=232,dc=net

Test these are correct with

1. Authenticate against LDAP

/usr/lib/squid/squid_ldap_auth -b dc=232,dc=net -f uid=%s -h ldap://k8.232.net

the server waits for you to enter a username, then a space then the password, success with an OK

sam SamSam987^%$
OK

2. Retrieve filter group members, eg. for the group students, where the attribute of the users is memberUid

yum install openldap-clients
ldapsearch -x -LLL -H ldap://k8.232.net -b dc=232,dc=net cn=students memberUid
dn: cn=students,ou=Groups,dc=232,dc=net
memberUid: bernard
memberUid: stephen

Let us know if you need to change the command to connect, and we can add to dungog-dansguardian

see also

man squid_ldap_auth
man ldapsearch

eg if the LDAP server requires authentication, for squid_ldap_auth add something like -D cn=root,dc=232,dc=net -W /etc/ldap.pwd


set the browser to use http://proxy/proxy.pac, users are required to have valid accounts on the LDAP server and must enter their username/password to access the proxy.

pam

set the browser to use http://proxy/proxy.pac, users are required to have valid accounts on the server and must enter their username/password to access the proxy.

ncsa

set the browser to use http://proxy/proxy.pac, users are NOT required to have valid accounts on the server users must enter their username/password to access the proxy. Create a user password file and assign users to groups.

To add users to the NCSA database /home/e-smith/db/proxyusers

we have a panel dungog-proxyusers

yum install dungog-proxyusers

or ...

db proxyusers set stephen user password 6ecreT group staff
db proxyusers set jimmy user password wiggles group students

where groups staff and students are enabled in the dansguardian panel as 2nd or 3rd filter group, bypass, banned or unfiltered

you can edit passwords and groups by

db proxyusers setprop password fruit5ly group students

after adding users

signal-event proxy-passwd

you may create or import a file in this format

stephen=user|password|6ecreT|group|staff
jimmy=user|password|lItt6kk|group|students
then
chmod 640 /home/e-smith/db/proxyusers
chown root.admin /home/e-smith/db/proxyusers
ident

set the browser to use http://proxy/proxy.pac, If you are using ident auth, you will require a ident client on your workstation. One windows ident client is available from: https://sourceforge.net/projects/retinascan.

In some cases, the Windows firewall blocks access to the ident client and you will have to add an exception in your firewall rules as follows:
Control Panel > Windows Firewall > Exceptions > Add Port
Name: auth > Port number: 113 > TCP

transparent proxy

no browser setup is needed. will filter on 8080 or the port you nominate. Note, this can be bypassed by the user entering 3128 in their browser.

disable dansguardian

resets transparent proxy to 3128, remember to untick port blocking if you enabled it.

Your Operating system may allow you to lock down your browser proxy settings, an alternative is to use the tick box in the panel to block ports 3128 to stop the filter being bypassed.

Help

Restarting Dansguardian

With a 'save & restart' Squid is restarted, Squid must restart before dansguardian, if it hasn't try 'save & reload' which doesn't restart squid or drop to command line and check. You can check if dansguardian is running with:

ps ax |grep dans

to start or stop from the command line see

dansguardian -h

Restarting dansguardian from the panel affects users differently depending on the button the options are:

Restart
-Q kill any running copy AND start a new one with current options.

Reload
-r closes all connections and reloads config files by issuing a HUP, 
but this does not reset the maxchildren option.
Custom Access Denied Page
  • CGI

To create/edit a custom .pl you have two options
create a new .pl file, dansguardianfN.pl and edit to suit
cp /home/e-smith/files/ibays/Primary/cgi-bin/dansguardian.pl
to /home/e-smith/files/ibays/Primary/cgi-bin/dansguardianfN.pl
where N is the filtergroup number

or set a db value deniedurl which overrules the above method, see db section below

  • HTML

to create/edit a custom .html
You can edit a html template in /etc/dansguardian/languages / LANGUAGE / template.html
LANGUAGE defaults to ukenglish but you can set with a DB command

make a copy relative to your filter level eg templatef2.html in your language directory

you can edit the default but it will be overwritten when you upgrade the Dansguardian rpm, so make a copy as templatef0.html which will be used if it exists

html template doesn't include a bypass link

DB settings

Not all settings can be set from the panel, you can set these settings with db commands, activate db settings with

signal-event dansguardian-reload


  • Language support, see options in /etc/dansguardian/languages, default is ukenglish
db dungog setprop dansguardian language danish
  • Set an alternate page denied url, eg. for filter group 2
db dungog setprop dansguardianf2 deniedurl 2321.net/cgi-bin/deniedf2.pl

then select and save this value in the filtergroup panel

  • change default denied page
db dungog setprop dansguardian deniedurl 2321.net/cgi-bin/denied.pl
  • to just change from the Primary domain to another of your domains
db dungog setprop dansguardian wsn 4545.org
  • POST protection, eg. uploads, forms etc.

Maximum Size of file allowed to be uploaded
default is -1 (no restrictions)
or enter a size in kb's eg.
0 = complete block
500 = 500 kb
5000 = 5 mb

db dungog setprop dansguardian maxuploadsize -1
  • A shortcut to entering a set of banned extensions, where fX is the filtergroup f1-f5
db dungog setprop dansguardian bannedextfX exe on   (executable)
db dungog setprop dansguardian bannedextfX macro on (macros and viruses)
db dungog setprop dansguardian bannedextfX arc on   (archives)
db dungog setprop dansguardian bannedextfX time on  (bandwidth wasting)


Time base restrictions

An alternative or additional method of control is to use a script to change db settings with cron,

see /usr/bin/dproxy for an example.

This would allow you to ban access to the internet for a group or to give unfiltered access. Make a copy of your altered script so it isn't overwritten by the next rpm update, and enable the changes with a cron job.

say your copy is /usr/bin/kidproxy
give access at 17:00 with /usr/bin/kidproxy open
then shutdown at 19:00 with /usr/bin/kidproxy close

MSN

To block MSN Messanger add the following to [mime types - Deny]

application/x-msn-messenger

Troubleshooting
  • Switch off or modify firewalls which block port 8080 on the client PC
  • A few users have had problems with transparent proxying, and we cant work out why, it's probably network issues. If this happens, which is uncommon, the best we can suggest is to use ident and set 8080 in your browser. Without adding an ident client you are assumed to be in the default filter group.
  • If the 'denied access' page comes up as follows, it is a problem with the syntax of your edited denied page or denied page url.
DansGuardian - 400 Bad Request
  • Bypassing the proxy selectively

You have Transparent Proxy enabled but want to allow this to be selectively bypassed.
or you have devices eg TiVo that you want to bypass squid
http://wiki.contribs.org/Firewall#Bypass_Proxy

the smeserver-adv-masq rpm in dungogMembers contains these fragments, and the db entries can be added in the
Modify status and proxy values. sub-panel

  • Trusted sites that you want unauthenticated access to can be added to the 'Common' exceptionsitelist

ie Common > modify > a site > allow
this will bypass dansguardian and squid authentication.

  • Email if problems continue after running through these steps

check yum at the command line

yum update

and

yum update --enablerepo=smecontribs

check logs

/var/log/messages
/var/log/squid/access.log
/var/log/dansguardian/access.log

check if dansguardian is running

ps  ax

what error does if give trying to start

make sure it is stopped

dansguardian -q

start it

dansguardian


check templates are expanded and restarted

signal-event dansguardian-save

wait for squid to restart

signal-event dansguardian-reload