[Serusers] avpops and ip based auth

[Greger V. Teigre]

Iqbal,
Sorry for being slow, I have been travelling.

I think what you are trying to do is sort of the pike module upside-down ;-)
You primarily purpose is to reduce the authentication requirements on 
INVITEs.  Now, if you use mysql as subscriber DB, the auth in itself is not 
really that bad, it's a DB read.  It scales pretty well.
So, to accomplish your goal and in order to reduce the number of DB hits, 
you need to find a way to avoid DB lookups alltogether.  avpops will not do, 
it is probably not more efficient than an auth (probably less because it is 
more generic).  Thus, you need to make a reverse pike module where the IPs 
are cached using a hash.  Dependent on the number of IPs you want to store, 
there will be added SER memory requirements.  Also, you will need a way to 
expire the IP from the auth DB.

    BUT: Maybe you could use a new usrloc table for this?  NOTE: There is 
(at least) one catch that prevents the following from working (see further 
down):
For an unauthorized INVITE (see check below), first challenge the user and 
authenticate, then on auth success, make sure that Contact has a public IP 
(which you probably do anyway). You will have the correct IP address in 
Contact. Then just save("ip_auth")

INVITE check:
You can then check if the IP is registered by changing the ruri to the IP 
address of the Contact and use if(registered("ip_auth")) to check if the IP 
is registered. Then do revert_uri();

Catch:
The username will prevent the registered("ip_auth") call from working, it 
will not match.  However, if you could change the username part of the 
Contact in the INVITE to "noone" or something static before saving and 
restore it before forwarding, you will get a usrloc table with:
noone at a1.b1.c1.d1
noone at a2.b2.c.2.d2
...

You must then change username part of ruri to none before the call to 
registered().

I don't know how to do that without any code.  Anybody?!

Mini-catch: You need to enable domain for usrloc, so if you use only 
username, you have a problem.

Mini-catch 2: I have not tried using save on an INVITE. I don't know how 
much error checking is done.

Hack? Oh yeah. But you reuse the memory cache of the usrloc and get no DB 
hits...

g-)

PS! If you tried, it would be interesting to hear the results...

Iqbal wrote:
> Hi
>
> I am using trusted mainly for inbound routes from my gateway to ser
> for inbound calling via pstn numbers mapped to IP phones. (I do think
> that trusted module/pacth bound to gateways listed in lcr could be a
> good idea).
> Now what I am looking for is to take several devices/gateways and have
> them hit ser but ignore all auth i.e no user/pass combos, but just
> detect IP's. I think I can get them to all have external IP adds,
> which would remove the problems of private IP's being used by other
> devices.
> My main problem is resource usage in all the scenarios, minimum DB
> hits is obviously best, lets assume the gateway will initiate 10000 calls
> (just to have alarge number :-)), and lets say all these calls are of
> 10 secs each, if I had to auth each call every time that would be a
> pain, however if I could auth once, and from there on in , just let
> all calls pass, and re-check the auth every so often (lets say once
> per hour) then thats fine.
>
> In terms of billing it would be per gateway, but I would need to break
> down per call, which shouldnt be hard since they would all have diff
> destinations I guess.
>
> trying to find the best scenario for a one time auth system with
> miminal db lookups in it.
>
> iqbal
>
> Greger V. Teigre wrote:
>
>> I would say that as allow_trusted uses a cached (and I believe
>> hashed) list of IP addresses to match against, it is better suited
>> for non-(or low) dynamic data like trusted peers etc. avpops is
>> better suited for subscriber specific operations (as avpops will do
>> the DB every time) and thus larger number of IPs and dynamic data.
>>    Are you thinking about storing the IPs with avp_db_store for each
>> register and then just allow any IP you have stored?  This would save
>> you some DB cycles probably (and some SIP messages) as you only do
>> one lookup and no digest challenge for INVITEs.  You would then allow
>> anybody behind a given NAT and again IP-based auth on UDP is not
>> really secure.
>>    And of course, you would probably need a way to expire the IPs?!
>>
>> Or have I misunderstood completely? What are you trying to achieve?
>> g-)
>>
>> Iqbal wrote:
>>
>>> allow_trusted I already use, just wanted to know which is better, or
>>> is it just personal preference here. If either is used and looking
>>> by the acc table billing could still be pulled even thought no
>>> username/password..any inputs here.
>>>
>>> Iqbal
>>>
>>> On 6/23/2005, "Greger V. Teigre" <greger at teigre.com> wrote:
>>>
>>>> Have you looked at allow_trusted() in (I believe) the domain
>>>> module. In fact, when I come to think of it, maybe the functions
>>>> are undocumented. I'm on GPRS right now, but I'll check when I get
>>>>    back over the weekend. You populate the trusted table and use
>>>> allow_trusted() before auth of INVITE's (and probably assume that
>>>> you don't get REGISTERs). There is also a FIFO command to reload
>>>> the trusted table. I guess it's feasible to use REGISTER to store
>>>> a new IP after a successful auth and then use IP for INVITE's.
>>>>    Ref. an earlier discussion, using IP for UDP is not really good
>>>> security-wise, you should use TCP.
>>>> g-)
>>>>
>>>> Iqbal wrote:
>>>>
>>>>> Hi
>>>>>
>>>>> If I use avpops for IP based auth, and drop the normal
>>>>> username/password combo aside from spoofing what is the downside
>>>>> if any. Also if I do IP based auth, can I auth once, and be done
>>>>> with it, or is it auth once per call, I guess its once per call,
>>>>> if so is there any way to bypass auth completely for a particular
>>>>> IP address, again I am assuming no, since the IP will still need
>>>>> to be checked for each request.
>>>>> Iqbal
>>>>>
>>>>> _______________________________________________
>>>>> Serusers mailing list
>>>>> serusers at lists.iptel.org
>>>>> http://lists.iptel.org/mailman/listinfo/serusers
>>>>
>>
>>
>> .