Change the Remoting User-Agent string ?

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Brian Anderson - 21 Dec 2004 20:45 GMT

Hello,

a Client using HTTP-Binary sends a User string like this to the server:

Mozilla/4.0+(compatible;+MSIE+7.0b;+Windows+7.0.1942.0;+MS+.NET+Remoting;+MS
+.NET+CLR+3.0.1942.7528+)

Now I wonder if it's possible to override this string with something shorter
like "MyTool 1.0a".

It seems that in System.Remoting.dll the constructor of this string is
hardcoded and not accessable :(

<snip>
// transport sender sink used by HttpClientChannel
internal class HttpClientTransportSink : BaseChannelSinkWithProperties,
IClientChannelSink
{
private const String s_defaultVerb = "POST";

private static String s_userAgent =
"Mozilla/4.0+(compatible; MSIE 6.0; Windows " +
"; MS .NET Remoting; MS .NET CLR " +
System.Environment.Version.ToString() + " )";
</snip

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Sam Santiago - 23 Dec 2004 22:33 GMT

I guess the bigger question would be why do you want to do this?

Thanks,

Sam

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_______________________________
Sam Santiago
ssantiago@n0spam-SoftiTechture.com
http://www.SoftiTechture.com
_______________________________

> Hello,
>
[quoted text clipped - 22 lines]
> System.Environment.Version.ToString() + " )";
> </snip

Reply to this Message

Brian Anderson - 24 Dec 2004 10:31 GMT

Think about what kind of information is given from the Clients to the
Server:

Mozilla/4.0+(compatible;+MSIE+7.0b;+Windows+7.0.1942.0;+MS+.NET+Remoting;+MS

> > +.NET+CLR+3.0.1942.7528+)

Everybody who intercepts this string can run fine tuned attacks against the
client as he knows quite well what is going on.
Today, you won't give out any information about yourself if you don't have
to.
You might even have signed a paper with your cusomers that disallows your
Remoting Client to transmit any internal information into the outside world.
Giving detailed info about the Client OS IS internal information.
When I pass the default User-Agent string, it's kind of spying out my
customers and it's completely useless to transmit this string in normal
Remoting scenarios.

Hiding this string and tell the Server + Client to pass only strings like
"MyTool Client 1.0" or "MyServer 1.0" helps to make the communication a bit
more stealth.

---

> I guess the bigger question would be why do you want to do this?
>
[quoted text clipped - 5 lines]
> >
> > a Client using HTTP-Binary sends a User string like this to the server:

Mozilla/4.0+(compatible;+MSIE+7.0b;+Windows+7.0.1942.0;+MS+.NET+Remoting;+MS

> > +.NET+CLR+3.0.1942.7528+)
> >
[quoted text clipped - 17 lines]
> > System.Environment.Version.ToString() + " )";
> > </snip

Reply to this Message

Ken Kolda - 27 Dec 2004 16:17 GMT

If you're worried about this level of stealth and the possibility of
snooping, you're certainly using SSL to encrypt the transmisions. In that
case, the User Agent string is as protected as any of the rest of the HTTP
communication from eavesdropping.

Ken

> Think about what kind of information is given from the Clients to the
> Server:

Mozilla/4.0+(compatible;+MSIE+7.0b;+Windows+7.0.1942.0;+MS+.NET+Remoting;+MS

> > > +.NET+CLR+3.0.1942.7528+)
>
[quoted text clipped - 24 lines]
> > >
> > > a Client using HTTP-Binary sends a User string like this to the server:

Mozilla/4.0+(compatible;+MSIE+7.0b;+Windows+7.0.1942.0;+MS+.NET+Remoting;+MS

> > > +.NET+CLR+3.0.1942.7528+)
> > >
[quoted text clipped - 18 lines]
> > > System.Environment.Version.ToString() + " )";
> > > </snip

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Change the Remoting User-Agent string ?

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