hpr-knowledge-base/hpr_transcripts/hpr0227.txt

Episode: 227
Title: HPR0227: Local Squid
Source: https://hub.hackerpublicradio.org/ccdn.php?filename=/eps/hpr0227/hpr0227.mp3
Transcribed: 2025-10-07 14:22:29

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So
Hello there ladies and gentlemen, my name is Ken Fallon and today we will be talking
about Squid Proxy for local use.
Now first of all what is Squid, it's a free open source proxy server, what's a proxy
server, well that's nothing more than a server that clients and an internal network will
go through to have their request forwarded out onto the internet and the reason you might
want to do that is in a corporate IT environment you typically will block access to the internet
so that worms and viruses and all that sort of good stuff can get out if a PC is infected,
they can get straight out to the internet.
So they go through a proxy server that may or may not require a username and password
to get out and then on the proxy server, dangerous URLs can be blocked or more than likely
has been used for in the past is to monitor employee access so that they're not waste
in time on the internet.
That of course is illegal in some countries specifically Germany so you want to check
the licensing laws in your country when applying a proxy server, however that is not why
I would use a proxy or why what spawned me to install an proxy in the first place.
There's really two reasons, so first of all is getting a secure connection to the internet
when you're at a hostile location and the other one is getting around URL obfuscation
or hiking of URL, well let's talk about the first one first.
So say for example you've got a laptop and you're at an internet cafe and you want to
securely check your email or you want to do some banking.
Now there's no idea who you have no idea who's listening on that connection.
So what you typically do, excuse me, what you would typically do is you would set up a
proxy server on your home server, you would set up a secure shell tunnel into that server
and then you would redirect your browser to use your local host and you would forward
a port over the SSH tunnel into your browser, into your server at home.
There's been a few episodes on that but a few podcasts on that, I don't think there's
been any on the HPR network but I'll give you all what you need to do.
First of all you need to install it and that is get install squid.
So then you would create, once you've done that you've got a squid proxy listening on
the default port of 3128 and I think by default and most distributions it allows the local
host to connect out specifically for this reason but I won't let anything else.
So then you drop to a shell and you would type SSH space minus capital L, space 3128
colon local host colon 3128 and then use the name add server and whatever other options
that you have.
What that will do is it will open a SSH shell to your home server and it will say anything
coming in on port 13128 on this piece in my laptop, PC in the hostel environment, you
encrypt all the traffic and you pump it out the other side of the tunnel and you dump
it up to the local local port of 3128 on your server.
So then you open up a browser and you go into your browser settings and you set the
proxy server to be local host and the port to be 3128 and in Firefox you'll set all
the, use this for all the other ports.
There's a nice little add-on called quick proxy I think for Firefox that will allow you
just quickly turn on and turn off the proxy server.
Okay, so that's handy.
You could also use that theoretically if your company blocks, blocks access to the internet
but they do allow SSH out, I would strongly advise you not to do them that because the
traffic on an SSH tunnel can be examined with deep packet analysis and also it's kind
of unprofessional so I would recommend do your work at home unless if your company has
specific exemptions that allow you to do that, do your work at home, otherwise just don't
do it, there's no point but near job at risk.
Now the other reason, the real reason that I installed this was to get around URL upsthucations
so word that I don't like so we're referring that to that as URL hiding.
So what they tried to do is to try to make it very difficult for you to work out what
the links are on the page.
So they kind of do that too is, first of all they'll use a whole go of tricks so if you
go to www.pchelp.pc-help.org you'll forward such upscure.htm you'll get a list of tricks
but it's also very common now to use javascript to do that so they'll have several include
files and some functions and they'll generate the URL based on different parts of the
in different locations of the file and then they'll put it all together and they also quite
common to use things like timed URLs where the URLs only remain valid for a certain period
of time and the logic is that by the time you figured out, by the time you figured out
what the URL is, the URL is no longer valid.
So all that does matter amount of hill beans because if you pipe your redirect your browser
to use a local host on either on a remote machine or use the squid proxy either on a local
machine or on a remote machine you can just tail the squid logs and your browser will
have done all the hard work for you and that will simply give you a list of guest commands
or posts or whatever typically to get commands with the URLs all reconstructed for you and
you can copy and use a copy them and use wget to get whatever you want.
Now why would somebody be bothered to do that?
First of all, most common one reason is to prevent the loss of their intellectual property
and the other reason I have seen is to do restrictions on streaming servers.
So let's deal with the first one first.
An example of that would be a cycle like called marked platz.nl, doesn't know, which
is a Dutch version of eBay, they're actually owned by eBay but they were bought over.
And what they do is they put a, for some reason they don't want you to take while they
don't want people to create databases of stuff on marked platz.
So what they do is they hide the URLs and they put a transparent gif file over all the
images.
So if you're looking to create a scraper or something that would go out and you know check
the website for you know new deals or whatever.
So they have it so that they, if you right click on the image, it, they have a transparent
gif over the image of say, you know, somebody selling a telephone or whatever.
They have a transparent gif over the image itself and when you right click on that and go
follow save as you get the transparent gif because that's over.
You can, it's also on YouTube but for a different reason and that is that YouTube uses a nice
trick where they have all the graphics on the page are sent down as one single image.
So the YouTube logo, the up arrow down arrow keys, the stars, all the stuff that you
see in a typical YouTube page is generated and sent down as one image.
And then they use CSS to show certain parts of that image on the web page.
I thought that was pretty cool.
To get on to the other reason why they would use stream, they would you hide the URLs
is for streaming servers.
So you have regional licenses in place where TV traditionally has been broken off onto
regions.
And for example, if you want the latest episode of desperate housewives, for instance,
the Republic of Ireland would have a different deal done than with the island of England.
And they would have a different deal done with the Netherlands.
So they would release it at different times and the charge different amounts depending
on where you are and where you live and your market segment, bloody, bloody, bloody.
However, that doesn't hold up any water in this internet age where people can connect
into machines and where people can connect from anywhere in the world to your streaming
service.
So to get around that, they use a service called GOIP and that's at www.maxmind.com and if
you go to slash app for slash support, you'll see that they actually provide free, and
I don't know what the license is.
I don't think it's GPL, but they provide modules for, let me have a look here.
Various different, various different programming languages that provide a module for Apache.
They provide a C-Lower, Bridge, Java, Class, Pascal, Per module, PHP module, Python and Ruby.
They also provide Windows APIs, Pascal and various different things.
And they also supply the GOIP country database in various different formats, CBS, MySQL,
Oracle and that sort of thing.
And they allow you to use the country data for free.
They won't catch you that you need to automate the downloading of it yourself and they don't
provide city or regional level or company name level, which they do do for, you know,
to sign up to the service button.
This is used by a lot of TV streaming people to block access to the playlists for the
streaming service.
Interesting side note is that quite often the streaming service themselves are proprietary
blobs and they don't support GOIP and to put in firewall rules on firewalls or whatever
slows down the streaming service.
So quite often if you get the URL somehow, for example, having a proxy server hypothetically
in your brother's house and you can use the Squid proxy over there to get the real audio
file and you can look at that to get what the real audio stream actually is and hypothetically
purely for research and reference purposes.
You open up a player from say another country, for example, the Netherlands, you could hypothetically
stream directly from the hypothetical servers that might hypothetically be in RTE.i.e.
However, that of course would probably be illegal.
Well, you're moral.
Anyway, to install Squid, we did aptitude install Squid and here's a quick technical tip
for working with config files.
Now the Squid config file is very much like the traditional Unix or Linux config file
in that it's got a lot of commons in it.
It explains that the config file itself is self-documenting in that the documentation
and on the values are in the config file and the documentation is typically commented
out with the oct-torp hash character.
And a quick tip that I've used here is how to filter out the common files and filter
out the blank line files so that if you know the configuration of a config file rather
than it would be in 16 pages long, you can cut it down to just the meeting bit it was
over and get the very essence of all commands that are actually been run.
So for the Squid config file, which is kept on ETCSquidSquid.conf, what you would do is you
would run the command grip, space minus v and the v says rather than displaying all the
files that you've found, it says don't display these files that don't display the lines
that correspond to the this search entry, excuse me.
So we have grip, space minus v, double quotes and we have the shark character which is the
circumflex accent and it's typically over the six in the US keyboard, I'll include a link
to that.
Some people have referred to it as a Chinese hat before.
Then you have the octetork character and what that is is the tic-tac-toe, what incorrectly
is called the pound sign and the double quotes space ETCS for slash ETC for slash squid for
slash squid.conf and then pipe that into grip, space min v, space double quotes, the Chinese
hat again and the dollar sign and the double quotes and what that does, the first one says
look for any hash marks that are at the beginning of the line and the second one says look for
any beginning in the line and the end of the line where there's no space between them,
essentially a carriage return line and don't show those.
So essentially then you get a nice list of just the comments in the file.
So I'll include links in the show notes to that and what actually if anyone is looking
for an idea to do a hacker public radio episode, deviate and doesn't want to do a LPI certification
module, although I don't know why because all the documentation is there all you have
to do is do it and then a topic on regular expressions would be very cool because while
the syntax changes more or less a little bit between Pearl and different websites and
bash and whatever, sorry, Pearl and bash and the syntax changes between programs and the
ideas more or less remain the same.
Okay, the important config changes that you need to make in that file are ACL local holes
source 172.0.0.1 for such 32.
More than likely that will be allowed and to allow access from the local holes you need
to have the line HTTP underscore access allow space local host also uncommented.
Now if you want to have a proxy server on serving the machines on your local network and
use private net networking, private subnets, you also need to have the line's ACL local
net space source space and then you have 3 10.0.0.0 for such as 172.16.0.0 for such 12 192.168.0.0.0 for such 16,
whichever one of those you're using uncommented probably already is, then you need to scroll
down to the little bit further in your file and look for another line which says HTTP underscore
access space allow space local net and once you do that save that file,
you can restart squid by calling ETC forward slash in a D forward slash squid space restart and
then you will be able to proxy out from the internal network. Now one good thing about squid is
for some reason you're not allowed out, you will still see a squid error message coming up
in your browser so you'll know that that part is working. If you don't see anything then your tunnel
is probably not working correctly or you can't communicate with your proxy server. So
that's a good good way to know where they are lies. If you don't see anything,
it's a tunnel issue communication with the proxy server. If you see or on the proxy server,
you know it's a permissions issue on the proxy server. Another thing that you can do is go to
whatismyip.com or ipchicken.com or moremyip.com and you will be able to see that your IP address has
changed to the IP address of your machine at all. Okay ladies and gentlemen, well that's been
another episode of Hacker Public Radio. It's actually the fourth time that I've recorded. I tried
to record it this morning on the train platform. I'm going to work on my bicycle and on the train
following advice from Davids and that did not work out at all. Okay, I hope you found something
interesting on that. I am available as always. The email address can.fanon at gmail.com. You can also
see comments on Hacker Public Radio.org for this episode or it should also be available on my blog
canfanon.com. Feel free to send me your comments and suggestions and that's all I have to say for now
and I wish you all a very good day. Thank you for listening to Hacker Public Radio.
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