http&rtsp kernel 'proxy'

http&rtsp kernel 'proxy'

[Francisco Javier Cabello Torres]

Hello,
I'm new with kernel development. 
I would like to implement a http&rtsp port as a kernel module.
First, I will try to explain what I want to develop. I have two servers, one 
of then a HTTP server, listening on port 80, and the second one a RTSP 
server, listening on port 554. My system is besides a firewall which only 
allow traffic in port 80. Because of that I need a 'proxy' listen on port 80 
which redirect traffic to RTSP server (still listen on 554) or HTTP server 
(now listen on 8080). This 'proxy' should  analyze incoming packets and 
depending of contents redirect it to one of the servers.  If packet contents 
belongs to rtsp protocol, it will be redirect to port 554, however if it's a 
http packet, it will be redirect to 8080.

I have been reading some documentation, and it think it would be possible to 
implement a iptables 'match' for rtsp and http packets, modify iptables to 
accept new match and then, with my modified iptables, specify rules to send 
packets to correct servers.
Any ideas? Am I going crazy?  ;)

Thanks.

Paco

--
Stop software patents!
examples: http://www.base.com/software-patents/examples.html
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 11:44:07 up 1 day, 19:11,  1 user,  load average: 0.09, 0.07, 0.04

Re: http&rtsp kernel 'proxy'

[DarKRaveR]

Hello Francisco,

I don't know about rtsp, but consider this:

HTTP should not be a problem, since the server is just answering, or
to put it in other words: As soon as the server establishes a
connection, the client will start the 'communication'. So it should be
possible to to analyse, what the client wants. If for rtsp the order
is reversed, like for smtp or most other protocols, your plans are
impossible. If, in both cases, the client initiates the protocol, I
assume you plans can succeed, at least I don'T see any reason, why it
shouldn't work.

Thursday, October 2, 2003, 11:45:10 AM, you wrote:

FJCT> Hello,
FJCT> I'm new with kernel development. 
FJCT> I would like to implement a http&rtsp port as a kernel module.
FJCT> First, I will try to explain what I want to develop. I have two servers, one 
FJCT> of then a HTTP server, listening on port 80, and the second one a RTSP 
FJCT> server, listening on port 554. My system is besides a firewall which only 
FJCT> allow traffic in port 80. Because of that I need a 'proxy' listen on port 80 
FJCT> which redirect traffic to RTSP server (still listen on 554) or HTTP server 
FJCT> (now listen on 8080). This 'proxy' should  analyze incoming packets and 
FJCT> depending of contents redirect it to one of the servers.  If packet contents 
FJCT> belongs to rtsp protocol, it will be redirect to port 554, however if it's a 
FJCT> http packet, it will be redirect to 8080.

FJCT> I have been reading some documentation, and it think it would be possible to 
FJCT> implement a iptables 'match' for rtsp and http packets, modify iptables to 
FJCT> accept new match and then, with my modified iptables, specify rules to send 
FJCT> packets to correct servers.
FJCT> Any ideas? Am I going crazy?  ;)

FJCT> Thanks.

FJCT> Paco

FJCT> --
FJCT> Stop software patents!
FJCT> examples: http://www.base.com/software-patents/examples.html
FJCT> stop it, see http://petition.eurolinux.org & http://petition.ffii.org/eubsa/en

FJCT>  11:44:07 up 1 day, 19:11,  1 user,  load average: 0.09, 0.07, 0.04




-- 
Best regards,
 DarKRaveR                            mailto:DarKRaveR@habitat-b.de

Re: http&rtsp kernel 'proxy'

[Francisco Javier Cabello Torres]

Hello,
thanks for your reply.
RTSP protocol is similar to HTTP. There are some situations where server may 
start a connections, but not in my environment.
If I have understood it, I have to implement two 'matches', one of then for 
RTSP and the other one for HTTP. With iptables I could add rules to redirect 
rstp and http traffic to different ports. Should I modified iptables 
application, by adding a dynamic library, in order to support new 'matches'?

Regards,

Paco

-- 
Stop software patents!
examples: http://www.base.com/software-patents/examples.html
stop it, see http://petition.eurolinux.org & http://petition.ffii.org/eubsa/en

 15:26:00 up 1 day, 22:53,  1 user,  load average: 0.06, 0.02, 0.00

Re[2]: http&rtsp kernel 'proxy'

[DarKRaveR]

Hello Francisco,

I think that's a question for the 'hardcore' iptable hackers ...
I am not really sure about this, sorry ...
Another thought: If both clients start sending the first data/string,
the extended string match might be a simple solution for you,
concerning http, the client starts with GET etc. ... RTSP I don't
know, but with this you could redirect the first packet. the question
is, if connection tracking helps you to handle all following packets
for this connection ...
I wonder, if any CORE iptables guy might be able to help you with this
...


Thursday, October 2, 2003, 3:31:33 PM, you wrote:

FJCT> Hello,
FJCT> thanks for your reply.
FJCT> RTSP protocol is similar to HTTP. There are some situations where server may 
FJCT> start a connections, but not in my environment.
FJCT> If I have understood it, I have to implement two 'matches', one of then for 
FJCT> RTSP and the other one for HTTP. With iptables I could add rules to redirect 
FJCT> rstp and http traffic to different ports. Should I modified iptables 
FJCT> application, by adding a dynamic library, in order to support new 'matches'?

FJCT> Regards,

FJCT> Paco


-- 
Best regards,
 DarKRaveR                            mailto:DarKRaveR@habitat-b.de

Re: http&rtsp kernel 'proxy'

[Francisco Javier Cabello Torres]

Hello,
thanks for all replies.
After all I think it's impossible to do it with netfilter. The problem, as Don 
Cohen told me, it's that I don't know which server owns the connection with 
the first packet (SYN). I need to establish the connection and then choose 
one of the target servers... this should be at application level.

Don Cohen reply:
'You do need a proxy for this, it cannot be done in netfilter, and in
general almost certainly should not be done in the kernel.
The problem is that you have to establish the connection before you
can find out which server to use.  If you could tell on the basis
of the first packet then you'd be in good shape.  Normally this would
be possible cause the first packet (SYN) would specify a different
port for the two servers.  But since this is not the case for you,
the first packet does not determine the server.  Therefore you must
complete the connection with a proxy, and then have that proxy, after
it decides which server to use, open a new connection to that server.
And as long as you have a proxy listening to all the packets that
come in, you don't need to use netfilter - just parse the packets in
the proxy.'

Regards,

Paco.



On Thursday 02 October 2003 14:15, DarKRaveR wrote:
> Hello Francisco,
>
> I don't know about rtsp, but consider this:
>
> HTTP should not be a problem, since the server is just answering, or
> to put it in other words: As soon as the server establishes a
> connection, the client will start the 'communication'. So it should be
> possible to to analyse, what the client wants. If for rtsp the order
> is reversed, like for smtp or most other protocols, your plans are
> impossible. If, in both cases, the client initiates the protocol, I
> assume you plans can succeed, at least I don'T see any reason, why it
> shouldn't work.
>
> Thursday, October 2, 2003, 11:45:10 AM, you wrote:
>
> FJCT> Hello,
> FJCT> I'm new with kernel development.
> FJCT> I would like to implement a http&rtsp port as a kernel module.
> FJCT> First, I will try to explain what I want to develop. I have two
> servers, one FJCT> of then a HTTP server, listening on port 80, and the
> second one a RTSP FJCT> server, listening on port 554. My system is besides
> a firewall which only FJCT> allow traffic in port 80. Because of that I
> need a 'proxy' listen on port 80 FJCT> which redirect traffic to RTSP
> server (still listen on 554) or HTTP server FJCT> (now listen on 8080).
> This 'proxy' should  analyze incoming packets and FJCT> depending of
> contents redirect it to one of the servers.  If packet contents FJCT>
> belongs to rtsp protocol, it will be redirect to port 554, however if it's
> a FJCT> http packet, it will be redirect to 8080.
>
> FJCT> I have been reading some documentation, and it think it would be
> possible to FJCT> implement a iptables 'match' for rtsp and http packets,
> modify iptables to FJCT> accept new match and then, with my modified
> iptables, specify rules to send FJCT> packets to correct servers.
> FJCT> Any ideas? Am I going crazy?  ;)
>
> FJCT> Thanks.
>
> FJCT> Paco
>
> FJCT> --
> FJCT> Stop software patents!
> FJCT> examples: http://www.base.com/software-patents/examples.html
> FJCT> stop it, see http://petition.eurolinux.org &
> http://petition.ffii.org/eubsa/en
>
> FJCT>  11:44:07 up 1 day, 19:11,  1 user,  load average: 0.09, 0.07, 0.04

-- 
------------------------------------------------------
V I S U A L   T O O L S
Francisco Javier Cabello Torres
R&D Department / Departamento de I+D
C/Isla Graciosa, 1.
28034 Madrid - Spain 
Telephone: +34 91 72948 44
Fax:  +34 91 358 52 36
fjcabello@visual-tools.com 
------------------------------------------------------
Stop software patents!
examples: http://www.base.com/software-patents/examples.html
stop it, see http://petition.eurolinux.org & http://petition.ffii.org/eubsa/en

 08:53:44 up 54 min,  2 users,  load average: 1.98, 2.23, 1.47

Re: http&rtsp kernel 'proxy'

[Tom Marshall]

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On Thu, Oct 02, 2003 at 11:45:10AM +0200, Francisco Javier Cabello Torres wrote:
> Hello,
> I'm new with kernel development. 
> I would like to implement a http&rtsp port as a kernel module.
> First, I will try to explain what I want to develop. I have two servers, one 
> of then a HTTP server, listening on port 80, and the second one a RTSP 
> server, listening on port 554. My system is besides a firewall which only 
> allow traffic in port 80. Because of that I need a 'proxy' listen on port 80 
> which redirect traffic to RTSP server (still listen on 554) or HTTP server 
> (now listen on 8080). This 'proxy' should  analyze incoming packets and 
> depending of contents redirect it to one of the servers.  If packet contents 
> belongs to rtsp protocol, it will be redirect to port 554, however if it's a 
> http packet, it will be redirect to 8080.
> 
> I have been reading some documentation, and it think it would be possible to 
> implement a iptables 'match' for rtsp and http packets, modify iptables to 
> accept new match and then, with my modified iptables, specify rules to send 
> packets to correct servers.
> Any ideas? Am I going crazy?  ;)

Why is your firewall restricted to port 80?  If you require the use of RTSP,
your administrator should open the port for you.

You cannot do protocol multiplexing with iptables and remain standards
compliant.  This is a job for an application level proxy.  You could
probably make it work "most of the time" with some clever string matching. 
But in the end, using iptables for this would be a hack.

-- 
The intelligence of any discussion diminishes with the square of the
number of participants.
        -- Adam Walinsky

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