LDAP and BER size

I recently came across a unique problem that didn’t “stand” out until I got to thinking about a couple of different situations that I had tested this in. So the scenario is that I needed to create a static group of unique members in LDAP (Sun Directory Server Enterprise Edition 6.3.1 and/or Oracle Directory Server Enterprise Edition that has a extremely huge amount of members in it. So I created the LDIF file with all 60,000+ uids in it and proceeded to run an ldapadd against the server with the file. Well it immediately would come back with:

adding cn=testgroup,ou=group,dc=sungeek,dc=net

However, when looking in the LDAP, the group never showed up. Also when you look at the access log on the server you would see something similar to this:

[07/Aug/2012:21:22:39 -0400] conn=3 op=-1 msgId=-1 – closing from – B1 – Client request contains an ASN.1 BER tag that is corrupt or connection aborted

Now some times, depending on the versions of LDAP server and ldapadd programs, I got a “broken pipe” right after the adding output.

As you can see from the output in the error log it is not very descriptive on what the actual error is. I know I spent about 6 hours looking in to it to figure out what was actually the problem. Well this morning I was poking around the cn=config docs and found this:


What this document shows is the attribute nsslapd-maxbersize, which is:

Defines the maximum size in bytes allowed for an incoming message. This limits the size of LDAP requests that can be handled by Directory Server. Limiting the size of requests prevents some kinds of denial of service attacks.

The limit applies to the total size of the LDAP request. For example, if the request is to add an entry, and the entry in the request is larger than two megabytes, then the add request is denied. Care should be taken when changing this attribute.

So by DEFAULT it is set to 2MB. Well my LDIF file was over 3.5MB in size. Which means that it was too big for the addition. To change it, do an ldapmodify with this ldif:

dn: cn=config
nsslapd-maxbersize: ########

I changed mine to 6MB, or 6291456, to hopefully cover any sizable additions in the future. Once done I restarted the directory server and tested again, and everything was good. According to the docs, the max size you can make this attribute is 2GB in size, and a size of 0 means default to 2MB, or 2097152. I think Oracle needs to make the error that is in the access log a little more descriptive, like “hey your query/add is too big yo”.

Hope this helps some one..