[Date Prev][Date Next]
Re: masking LDAP_SIZELIMIT_EXCEEDED
I'm not sure how I'm failing to achieve 1-to-1 mapping. There is zero
rewriting involved in any of this. The client must search for and use an
unambigious target DN for the bind request. This presupposes knowledge of
(.*)Org1 or (.*)Org2 at authentication time. "person2,o=Org1" and
"person2,o=Org2" are as unambigious as "x,o=Org1" and "y,o=Org1"--they
just plain don't strcmp() identical. Client and server logs both reflect
Org1 or Org2, access can be granted as appropriate, etc.
The fact that this doesn't trickle all the way down to the primary key
being "uid=person2@Org1" doesn't mean that the client and server can't
tell an absolute identity. If somebody writes a client that binds to one
DN of person2/org2 and then reads the attributes of a different DN
person2/org1, they're way beyond what I can help them with. (Although the
masked sizelimit might work there too, because the brain dead client will
only see person2/org1 in all cases :) Or I could ACL out reading org1 from
the org2 identity.) What I'm guessing would be a more X.500 way of doing
this -- only have person1@bigOrg and give org1Password and org2Password
attributes -- would also be beyond my help if somebody decided to bind
against org2Password and then read org1AccessLevel. Actually, I might be
even worse off with that, because I can't think of any way to ACL out the
org1 attributes from the org2 identity. I can only give rope in the
directory; tying the knots is left for the client developers...
Anyway, the whole point of the dialogue here is to avoid needing a private
overlay and to try and find something that at least tries to comply with
the spirit of the standards, lets you have multiple identities that are
easy to access (I'm sure there's some awesome idassert stuff out there,
but I can't beat a TLS-encrypted userPassword for client compatibility),
and if I do need to write something, might have a hope of being useful
outside of my crazy world. "What you're doing is so insane that nobody
else would want it" is perfectly acceptable, though.
On Thu, 8 Mar 2007, Howard Chu wrote:
First off - what you do in the privacy of your own network is your business,
go ahead and write the 8 line overlay if that's what you want.
But realize that the design you have here is an epic security breach waiting
to happen. The purpose of authentication is to unambiguously identify the
client of a service. (And in the case of mutual authentication, the provider
of the service as well.) When you do not enforce a 1-to-1 mapping of users to
login IDs and credentials, you don't have "authentication" - you just have a
guess. I.e., all of your client software in group (1) below is broken, by
Presumably one reason for giving person2 two separate entries is to give them
two separate roles, two separate classes of authorization. You might entrust
someone with the person2/org2 username and password to accomplish one set of
tasks; if the software accepts that password but then looks up and uses the
person2/org1 privileges instead, you're in trouble and most of the time you
won't even detect when something bad happens until you read about it in the
Aaron Richton wrote:
Hmm, maybe drawing a parallel to an ACL was a bad idea (although this
behavior does sound similar to "disclose" to me because I want to not
expose the truth to some unprivileged clients). The clients I want to keep
in the dark are due to their code path, not because the information is
something that I want to keep from them for privacy/security per se.
We have entries along the lines of:
This is totally valid in our (feel free to call it warped) view of the
world. person2 is indeed the same physical person, but they only intersect
on "uid" from the directory perspective. Very notably, person2@Org1 and
person2@Org2 have different userPassword attributes.
I'm sure this all sounds slightly ridiculous, but it actually works quite
well. It makes things particularly easy for administrators of systems in
either Org1 or Org2. The exception is on queries that span Org*. We've seen
two basic client behaviors with off-the-shelf software:
1. Search, and use the first candidate entry that's returned. Our users hae
been trained that "Org1" is the most important and they should use that
password/expect those attributes on systems that span units.
2. Search, and error out since multiple candidates are returned.
I don't necessarily think there's anything wrong with (2), but it causes my
example "person2" to not get access. What I'd like is to mimic (1). I've
been patching client software to that behavior, but it seems that there's a
lot of (2) out there. So I'm looking for something server-side to fix this
"permanently". If I set a sizelimit of 1, then only
will be returned on a '(uid=person2)' query. The problem is that the return
code is not LDAP_SUCCESS, so I error out on that issue. If I mask the
exceeded result, then the (2) clients will be blissfully ignorant that
person2 spans multiple entries, and grant access under the Org1 candidate
dn (which is what I want).
On Thu, 8 Mar 2007, Howard Chu wrote:
Aaron Richton wrote:
I've found a situation similar to what I believe inspired "disclose"
ACLs, in which giving out the return value of LDAP_SIZELIMIT_EXCEEDED is
telling clients something that I don't want them to know (i.e. "keep
digging.") I'd like to just throw away the code and change it to
LDAP_SUCCESS. Can anybody think of a way to do this (slapo-retcode comes
to mind, but I can't see how it would work on these very non-dynamic
entries) or should I just write an eight line overlay?
Is this something that enough people want that there should be, say, a
"silent" option to the limits directive?
This seems like a pointless option. If I do a search for (cn>=a) and get
500 entries returned, and another search for (cn>=b) and still get 500
entries returned, then it's obvious there are more entries out there even
if you mask the result code. The "disclose" feature of ACLs is a real
security measure, because it prevents you from seeing that which you could
not see by any means. What you're proposing here is not; the information
you're hiding can still be discovered by other legitimate mechanisms. It
is easily circumvented and it's contrary to the specification of the
Directory System models.
-- Howard Chu
Chief Architect, Symas Corp. http://www.symas.com
Director, Highland Sun http://highlandsun.com/hyc
Chief Architect, OpenLDAP http://www.openldap.org/project/