Re: [Slashcode-development] Slash::Apache::User on PerlAuthzhandler?

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Hi Cliff,

  Yep this helps. I did some more testing with a stripped down set of 
scripts and this is what I've found out:

* User opens up a brand new Firefox session with no cookies or history 
of any sort.

* Request comes in to apache and the first relavent thing apache does is 
PerlAccessHandler. $r->user is undefined.

* Then apache (which is setup to do Cosign (i.e. kerberos with cookies) 
calls its Authentication routines but does not call PerlAuthenHandler, 
ever (or at least I can't get it to)

* At this point the users is taken to another URL, asked to enter their 
password etc. Then they are returned to the original URL /with/ a brand 
new encrypted authentication (Cosgin) cookie.

* So Apache starts up again and the call reaches PerlAccessHandler which 
now has a defined $r->user.

* Again Apache doesn't call PerlAuthenHandler. But does its cosign stuff 
again but as we have a valid cookie it passes through OK and doesn't 
redirect.

* Then we get to PerlAuthzHandler, which does get called and has a 
defined $r->user.

I.e, in order

PerlAccessHandler
Apache Auth
PerlAccessHandler
PerlAuthzHandler

---

So the upshot of this is that I need to rely upon $r->user (and 
therefore REMOTE_USER).  And it seems to me (but I'm prepared to stand 
corrected) that the first time Slash::Apache::User gets called it looks 
to slash like we're anonymous.

What I've not investigated yet is weather slash gives me a cookie at 
that point which says "I'm anonymous".

---

Which is why from MPOV it'd be better to either:

1) Move the whole shebang to PerlAuthzHandler, or
2) Leave the IP blocking stuff of Slash::Apache::User on the 
PerlAccessHandler and move every thing else to PerlAuthzHandler

Either way instead of hacking my fix directly into Slash::Apache::User I 
might just put a hook into it and make things a bit more generic.

  If I get to to work I'll submit a patch.

Yours
Faye

Clifton Wood wrote:
> Ah, you make a good point, here.  It's probably easier to think about
> things in this manner, and it's been a while since I've done mod_perl
> 1 so I think I might have missed critical differences in each of the
> necessary handlers -- there are *3*, not 2. Presented in the order
> they execute (I hope I have this right):
> 
> PerlAccessHandler - Determine if the client is to have access to a
> specific resource, this is generally used to deal with IP banning as
> such and doesn't require the need for specific credentials (usually
> indicated by directives like "AuthType", "AuthName", and "require").
> THIS is why Slash uses this handler. Really, Slash::Apache::User is
> probably doing too much, but since there is an IP ban list in Slash,
> it was probably just easier to handle everything in one piece of
> monolithic code. If other Slash sites needed the extra security, they
> could handle those pieces on their own. As it is, the only
> "authentication" necessary is handled by Slash's perl scripts and need
> *not* be handled by specific client/server interaction. (as is the
> case with PerlAuthenHandler and PerlAuthzHandler). The only
> distinction that Slash cares about at this point is "logged in" and
> "not logged in", and this is handled by the presence of a specific
> cookie. All other security measures are handled by the script code,
> not by specific server code.
> 
> PerlAuthenHandler - Handles authorization, ala verifying user
> credentials and the like. You would think that this would be the
> natural place for your code, but it isn't, as it would require  an
> "AuthType", "AuthName" and "require" directive, which Slash doesn't
> use. Since Slash has already done it's magic in PerlAccessHandler,
> this also makes this handler redundant.
> 
> PerlAuthzHandler - Determins if an *authenticated user* is to have
> access to specific site resources. This assumes that a client *has
> already authenticated* based on the results of PerlAuthenHandler and
> is intrinsically linked to that particular phase. Since
> PerlAuthenHandler isn't used for Slash, neither is PerlAuthzHandler.
> 
> Slash doesn't need $REMOTE_USER to do it's magic, you do. What you
> might want to try is to use stacked PerlAccessHandlers to check
> $REMOTE_USER. You would perform this check and automatically generate
> a properly formatted Slash cookie for that user, then let Slash's
> existing code run afterwards to do that voodoo that it do.
> 
> For your purposes, your code would need to run first, and then the
> existing Slash handler would run last.
> 
>     PerlAccessHandler Slash::Apache::User::RemoteUserCheck Slash::Apache::User
> 
> Here's an outline on how I think your PerlAccessHandler should work:
>    - Check $REMOTE_USER. Robust code says you should do this. Do not expect it
>      to exist. If it doesn't, fail out ("return
> Apache::Constants::FORBIDDEN" --
>      Apache::Constants::AUTH_REQUIRED might work here, too.).
>    - [optional] If it exists, perform a check to see if the Kerberos
> credentials are valid.
>    - Do a query on the $REMOTE_USER user in the database, if she does not exist,
>      create an account with your default password.
>    - If any errors, return "Apache::Constants::SERVER_ERROR".
>    - If you get to this point with no problems, bake a properly formed
> Slash cookie,
>      and send it to the client.
>    - Done. "return Apache::Constants::OK"
> 
> I *think* this is how it should work. I had to go back to the mod_perl
> 1.0 docs and check my assumptions and this is maybe the 3rd or 4th
> version of this email since I got several things wrong! ;-)  -- I'm
> sure that probably doesn't instill great confidence in what I've
> written above, but it's the best I've got to offer at this time. If
> anyone else can correct any errors or misconceptions in the above,
> please do. I know I ain't perfect and am not arrogant enough to push
> forward that assertion. ^_^
> 
> Hope this helps!
> 
> - Cliff
> 
>> On 5/14/07, Faye Gibbins <fgi...@st...> wrote:
>> Hi,
>>
>> Disclaimer:
>>              Please forgive a slashcode novice if this discussion covers
>> well trod land.
>>
>> The default install of slashcode attaches Slash::Apache::User to
>> PerlAccessHandler.
>>
>>   PerlAccessHandler is run before PerlAuthenHandler which is in turn
>> runs before PerlAuthzHandler.
>>
>>   So if using Apache external authentication the REMOTE_USER env var is
>> not available at the "PerlAccessHandler" but _is_ available at the
>> "PerlAuthzHandler" phase. This makes it difficult to setup accounts
>> based upon the Authentication phase.
>>
>>   So to gain finer control over user access would it not make sense to
>> move Slash::Apache::User to the PerlAuthzHandler phase?
>>
>> Yours
>> Faye
>>
>> --
>> ---------------------------------------------------------
>> Faye Gibbins, Computing Officer (Infrastructure Services)
>> GeoS KB; Linux, Unix, Security and Networks; 0131 6506426
>> ---------------------------------------------------------
> 
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-- 
---------------------------------------------------------
Faye Gibbins, Computing Officer (Infrastructure Services)
GeoS KB; Linux, Unix, Security and Networks; 0131 6506426
---------------------------------------------------------