Subject: Re: Persistent Search questions

From: "Timothy Hahn" <[email-masked]>
Date: Tue, 30 Jan 2001 20:44:02 -0500

Jim,

I would expect behavior as described in b) below.

I cannot confirm that sizeLimit and timeLimit are ignored - but it seems 
reasonable.  It also seems reasonable that there may be some other 
administrative configuration that implementations support to help reduce 
the thread of DOS attacks when employing this control.  (I can envison 
500,000 clients all setting up a persistent search to a single server 
....)

Regards,
Tim Hahn

Internet: [email-masked]
Internal: Timothy Hahn/Endicott/IBM@IBMUS or IBMUSM00(HAHNT)
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To:     <[email-masked]>
cc: 
Subject:        Persistent Search questions

The persistent search control (draft-ietf-ldapext-psearch-03.txt) states 
in section 3 that the search operation is modified in such a way that the 
searcResultDone message is never sent. This implies that the size and time 
limits are ignored, but it's not explicitly stated. Can anyone confirm if 
this is the case?

Also, there is a little blurb in the security considerations section about 
making sure access controls are checked for entries being returned. This 
is more of a question to other implementors, a server could:
a) check access control information once at the beginning of the search, 
and use that information without refreshing it later (could speed response 
time, and "fix" authorization to a specific view, or it could
b) recalculate access control information everytime an entry is to be 
returned (provides consistency over long persistent search sessions).

My feeling is that b is better, does anyone expect a?

Jim

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From: "Kurt D. Zeilenga" <[email-masked]>
Date: Tue, 30 Jan 2001 17:57:18 -0800

In regards to DoS attacks, seems you could really drive a
server crazy by asking it to sort a persistent search.

Kurt

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From: Stig Ven�s <[email-masked]>
Date: Wed, 31 Jan 2001 08:35:48 +0100

> server crazy by asking it to sort a persistent search.

To be of any use in an open environment I think it must be possible
with acls to specify who can make persistent search on what, and
perhaps also how many simultaneous searches are allowed. As an
administrator I wouldn't allow this for anonymous binds. There is
a danger of DoS attacks even when not sorting. It might be because
I haven't read all the details, but I fail to see how sorting can
be of any use with persistent searches, except for possibly returning
the entries already present.

Stig