Tag Archives: proxy

Antinat outgoing ip same as incoming

Problem

The previous post shows you how you can configure the outgoing ip in antinat but if you have multiple ips and you want to use all of them and you want to be able to control which one to be used for certain things that patch doesn't do enough for you.

Solution

Antinat should bind the ougoing connection on the same ip on which it receives the connection from the client.

So if you want to use a different ip just set your configure your socks settings in the browser or proxifier to the ip you want antinat to use.

And here's the patch to let you do that ...

Antinat outgoing ip same as Incomming-1.0 (10.1 KB)

This patch is incompatible with the one on the previous post, you can either have that one or  this one so make sure you apply it on the original antinat source.

Questions or suggestions are welcome as always ...

http://www.google.com/url?sa=t&source=web&ct=res&cd=1&ved=0CAgQFjAA&url=http%3A%2F%2Fantinat.sourceforge.net%2F&ei=WoKjS9DcKczFsgaGwJjMCA&usg=AFQjCNEOlqPAc6T7bkDx0VQpJc2kIBBYHA&sig2=Mdve5s6Ylxdz72SqWJdYfA

Antinat outgoing ip

This post is the first in a series of posts about antinat. The posts will provide solutions for some "problems' with antinat. So here goes the first one ....

Problem

Antinat creates outgoing connection from the primary ip defined on the machine where it's running. There's a config option to make antinat listen on a specific ip but no config option to make it use a specific ip for outgoing connections.

Solution

The attached patch will make antinat use the same ip that it's listening on for outgoing connections. You specify the listening ip with the "interface" config option and now that ip will also be used for outgoing connections.

Antinat outgoing ip-1.0 (3.57 KB)

I assume you already know how to patch ... if not ... just ask in the comments or hire me to patch it for you 🙂

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HowTo: Shared Hosting as Socks Proxy

Problem

You need a proxy to connect to a service that would only accept connections from a certain location.

You have a shared hosting account on a server in location that is accepted by the service where you want to connect. Could you use it as a proxy server.?

You could install one of those proxy scripts made in php but that would only let you browse the web, what you want is be able to proxify any application and for that you need a socks server working with one of those proxifier applications  (like tsocks on linux/unix ).

So could you use a socks proxy on your shared hosting account?

Solutions

The solutions are listed starting with the most simple working on the most permissive hosting accounts and ending with the most complex suited for the least permissive accounts.
There will be further posts describing the solutions in detail. This post is mostly an introduction.

  1. SSH Tunnel

    This is the simplest but it assumes that your hosts allows ssh access to your account and they don't block ssh tunnels.

    1. ssh user@hosting-server.com -D1080

    This creates a socks server on your local host , then you can use it in the proxifyer app to forward all connections through it.

  2. Custom SSH Tunnel

    This is a solution for those hosting accounts that don't allow ssh tunneling, but allow you to connect over ssh and run a program ( antinat - a socks server ) once connected over ssh.

    ( One might wonder: why create a tunnel when you could just run antinat and connect directly to it? If you can do that then that's the best way to do it but most shared hosting servers would have all ports blocked so you would not be able to connect to any port other then the standard ones ( 80,443,25,110,143, etc ) but those are only available to root and are already busy anyway. )

    The idea is to forward the traffic from your computer to the proxy server through the actual ssh connection instead of using the standard tunneling mechanisms which are blocked by server's configuration.

    For this you would need a program on your host to act both as a socks server ( sort of ) and as a forwarder through a ssh connection. On the other side ( hosting account ) you would need another program that would receive data from the ssh connection and forward it to antinat. Both programs would actually have to forward data both ways.

    Both forwarders would have to multiplex connections and forward them through a single ssh connection because most hosting accounts only allow one connection / user

  3. Callback Socks server

    This is a solution in case your hosting account has no ssh access.

    It's similar to previous solution but in this case instead of having the local forwarder connect to the remote ( hosting ) forwarder through ssh, you eliminate the remote forwarder and just have the socks server connect back to the local forwarder and then forward everything through that connection.

    This would require modification to the socks server as antinat doesn't have this callback feature built in.

    Another requirement is that you are able to upload and run antinat on the server. Usually you can do this by just calling it in a php script ( eg.: system('antinat') ) or from a perl script if the host offers cgi access.

  4. Custom script ?

    What if for some reason (no cgi or php system() blocked ) you can't run antinat?

    Well in this case I'm guessing it would be possible to write a script that you could call over a http connection, and forward through it, but php's socket functions would need to be available and script's max execution time would limit your connection time so don't expect much of this.

I have used solution #1 and I wrote the software and patches required to make #2 and #3 work. In the following weeks I'll write the posts to describe them in more details.

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If you know other ways of doing this or ideas about my solutions I'd love to read about them in the comments.

How to set up an anonymous proxy on debian

This document describes the steps required to install squid proxy server from http://squid-cache.org and webmin from http://webmin.com on a debian 4.0 system as well as basic steps required to configure squid to listen on multiple ip addresses and use them as outgoing source address for connections. This will also show you how to configure squid from webmin to accept connections only from predefined clients based on the client's ip address.

For the steps presented below root access over ssh on the server or physical ( console ) access will be required.

Squid installation

Installing squid on a debian system is straight forward. The administrator must be logged in as root and just type: apt-get install squid. This will install squid along with all required dependencies (it may ask for the user permission to install, in that case just approve ).

Webmin installation

download the webmin .deb package from http://webmin.com/download.html and upload it on your server, then type: dpkg -i webmin_1.xyz.deb where xyz is the current webmin version.
This will look for required dependencies and will let you know if something is missing. In case anything is missing you can just install it using apt-get install command simiar to how you installed squid.

Once webmin is installed you can access it over web from your browser like https://yourdomain.com:10000

Webmin configuration

If wedmin and squid were both installed from the standard debian package then webmin should already know where squid configuration files are and be able to modify it and stop/start squid. If this is not the case then you can set the paths in the module's configuration section.

Squid Anonymous configuration

Set http_port to specify the port and ips where squid will listen for incoming connections. If you want squid to listen on any of the available ips just set it like this: http_port 3128

Make squid anonymous by specifying which headers it should allow/deny. For highly anonymous proxies here is the suggested configuration:
header_access Allow allow all
header_access Authorization allow all
header_access WWW-Authenticate allow all
header_access Proxy-Authorization allow all
header_access Proxy-Authenticate allow all
header_access Cache-Control allow all
header_access Content-Encoding allow all
header_access Content-Length allow all
header_access Content-Type allow all
header_access Date allow all
header_access Expires allow all
header_access Host allow all
header_access If-Modified-Since allow all
header_access Last-Modified allow all
header_access Location allow all
header_access Pragma allow all
header_access Accept allow all
header_access Accept-Charset allow all
header_access Accept-Encoding allow all
header_access Accept-Language allow all
header_access Content-Language allow all
header_access Mime-Version allow all
header_access Retry-After allow all
header_access Title allow all
header_access Connection allow all
header_access Proxy-Connection allow all
header_access Cookie allow all
header_access Set-Cookie allow all
header_access All deny all

Some may want to remove the lines that contain Cookie and Set-Cookie headers but if you do that most sites will not work anymore cause most require cookie / session support.

Squid multiple ip configuration

We want connections that come from one ip to go out on the same ip. First set acls to identify the ips where squid listens for incoming connections. Let's say we have 3 ips : 10.0.0.1 , 10.0.1.1 and 10.0.2.1 . The acls would look like this:
acl in_10_0_0_1 myip 10.0.0.1/32
acl in_10_0_1_1 myip 10.0.1.1/32
acl in_10_0_2_1 myip 10.0.2.1/32

Now you can set up tcp_outgoing address using the above acls:

tcp_outgoing_address 10.0.0.1 in_10_0_0_1
tcp_outgoing_address 10.0.1.1 in_10_0_1_1
tcp_outgoing_address 10.0.2.1 in_10_0_2_1

Set up access rules based on client ip

You will have to set up acls similar to the above but they identify the client's ip ( not proxy server's ip). The the acls will be used in the http_access directive. This can be done directly from the configuration file.

Here is a sample that shows how to allow access for a client with the ip 10.0.0.10 :
acl cli_10_0_0_10 src 10.0.0.0.10
http_access allow cli_10_0_0_10
Just put those two lines in squid.conf before the “http_access deny All” line.

You can also add an ACL from webmin -> Servers -> Squid Proxy Server -> Access Control ->> Edit Acl . The acl type has to be “Client address” . You just have to set a name and a “From address” ( the address you want to allow access to squid ) for it and then save it. After you set the ACL you have to go to "Add proxy restriction" , set the Action on “Allow” , select your acl from the "Match ACLs" box and click save. After the save you should be redirected on the main acls page where you should see your acl in the “Proxy restrictions” list, right at the bottom.
You will have to make sure your acl goes before the “Deny all” entry or else it will have no effect. You can put it one row up by clicking the “Up” arrow.

Now you can Start/Restart squid from command line /etc/init.d/squid start/restart or from webmin -> squid proxy server
You can test your squid configuration by setting any of the available ips as a HTTP proxy in your browser ( port 3128 ) and then go to http://spotip.com . That site should show you the exact ip you have set up as proxy in your browser.

No browser supporting socks5 authentication?

If you're trying to use a socks server with Internet Explorer , Firefox, Opera or Safari everything will work just fine, except for authentication.

From my point of view this is a big problem. Who in the world would leave such a proxy server unprotected? Yeah of course you can always limit access to a proxy server based on ip address, but in some cases ( see NAT ) this is just not going to work.

Internet explorer supports only the socks4 protocol which doesn't even support full password authentication ( only username and it defaults to the current logged in username ) .

Firefox supports socks5 but no authentication mechanism so supporting socks5 is pretty much useless. I think I saw some ticket in bugzilla about this but no one managed to commit a fix yet.

Opera doesn't even support socks protocol but I thought I should mention all major browsers 🙂

Safari supports SOCKS5 and even allows you to set a username and password to access the SOCKS server but it does not use them.

I tried Konqueror, but I was unable to specify the Socks server, I guess this is because it was not compiled with a socks library.  Has anyone had any success with Konqueror and Socks ?

squid digest authentication


If you use authentication in squid you have several mechanisms ( authenticators ) to chose from. The Basic authenticator is the easiest to set up and the most insecure because the client sends the username and password in plain text to the proxy server.

Instead of using the basic you would consider using the digest authenticator. This authenticator does not require the client to send the user and password in plain text but encoded in an MD5 hash so that an attacker that captures the data between the client and proxy server will not be able to use the user and password.

Continue reading

squid 2.6 transparent proxy

In case you used squid 2.5 to create a transparent proxy and you decided to switch to 2.6 or this is the first time you try to set up a transparent proxy and most/all of the tutorials out there are for squid 2.5 here is a brief howto for this setup.

In squid 2.6 the configuration options:
httpd_accel_host
httpd_accel_port
httpd_accel_with_proxy
httpd_accel_uses_host_header
are not defined anymore ( see squid 2.6 release notes ), so if you are using them in your config file squid will give you an error like "parseConfigFile: line 41 unrecognized: 'httpd_accel_host virtual'" and will refuse to start.

To activate transparent proxy in squid 2.6 all you have to do is use the "tranparent" option on http_port. Something like:

http_port 3128 transparent

Of course squid has to be compiled with transparent proxy support for netfilter (iptables) by adding --enable-linux-netfilter to the ./configure line, the linux kernel needs to be compiled with netfilter and you will also need a rule in iptables that will redirect packets from your local network interface with a destination port 80 to the port squid is listening on.

Assuming your local network interface is eth1 and squid listens on port 3128 here is the rule that has to be added to iptables:

iptables -A PREROUTING -i "eth1" -p tcp –dport 80 -j REDIRECT –to-port 3128