Dameon Wagner wrote:
On Sat, Jan 03 2015 at 01:31:10 +0000, Howard Chu scribbled
Define lengthy - how many bytes?
For the complete LDIF of the entry update in question, it is 672808 bytes (658K) -- I haven't done an exhaustive "trial and error" analysis to find the boundary between OK and too-big, but at 68233 bytes (67K, or 1000 lines of updates for the entry) the update completes OK, but at 205105 bytes (201K or 3000 lines) the update fails as described.
That looks like a bug in Cyrus SASL. What SASL mechanism are you using?
GSSAPI -- we use Kerberos for nearly everything, and the task in question uses a credential cache created from a keytab using k5start, though as an independent process (we're not using k5start to run the task's commands itself).
/etc/sasl/slapd.conf for the system in question contains only "mech_list: gssapi".
While I must admit that C isn't my forte (I'm more on the admin side of sysadmin than on the development side), I'm comfortable reading code and had a look through the code-base for those sb_sasl* messages and didn't see anything specific enough for my untrained (or unfamiliar) eye to use as a clue for further sleuthing.
While it is quite probably an incorrect assumption, I assumed at the time that the messages may have been caused by the client side closing or dropping the connection unexpectedly.
If it is of any interest, I see the same issue with both libsasl2-modules-gssapi-heimdal and libsasl2-modules-gssapi-mit Debian packages.
That's good information. Unfortunately I can't reproduce the problem here, ldapmodifying a group with 4640 members (237KB) works fine for me thru SASL.
It might be enlightening to run slapd with -d2 to show the packet decoding activity. Also run ldapmodify with -d2.
The LDIF for the failed entry consists of:
#---8<------------------------------------------------------------- dn: <DN-FOR-FAILED-ENTRY> changetype: modify replace: member member: <DN-FOR-MEMBER> ... member: <DN-FOR-ANOTHER-MEMBER> #---8<-------------------------------------------------------------
where the list of members was, in this case, 9799 long. The LDIF itself is 30097 lines long, and was happy for the first ~15000 lines.
If I prune out the modifications for the troublesome DN, the remainder of the file also goes through happily.
As a work-around I can manually split up the list into several blocks (tested with roughly 1000 member updates per block) with "replace: member" for the first, to match the current behaviour, and "add: member" for the rest. In this format, ldapmodify is happy to process the LDIF (all in one connection, but as discreet operations). (Note: the authenticated user has "unlimited" limits in the config)
Given that, it sounds like it could be a bug in ldapmodify (I don't think it's on the slapd end). I've tested on both the debian stable package (version 2.4.31-1+nmu2), and with a locally compiled build direct from the project's download pages (also 2.4.31 to start with, to see if it was an introduced bug).
Has anyone else on the list seen anything like this before?
2.4.31 is over 2 years old. 2.4.41 is about to be released. Debian is known to break their packages from time to time with ill-advised "security" patches. You should try with freshly built source.
Yeah, we've hit that sort of thing before, and is one reason why we have compiled our own packages in the past (not just for openldap), but it's something we try to avoid if possible, and attempt to re-converge on Debian packages where patches and updates we we're applying are eventually applied in Debian.
Yesterday I complied 2.4.40 and switched the managed configuration to use that package for the test system in question. Unfortunately it had the same issue.
Since writing originally, I've had a look (with my previously admitted limited C skills) to compare any differences between ldapmodify for the (working) 2.4.24, the (not working) 2.4.31 and the (also not working) 2.4.40. There's little change to speak of from what I can see, and nothing that looked to my eye like it might be the cause (though I've only really looked through clients/tools/ldapmodify.c, and very briefly through libraries/libldap/modify.c)
I also see no relevant changes from 2.4.24 to the current RE for ldapmodify.c or libldap/cyrus.c (where encoding/decoding is done).
If your tools are dynamically linked, you might try mixing the tools and libraries. E.g., try the 2.4.24 ldapmodify against the newer libldap. If that reproduces the bug, then we know to look closer at libldap.
After that, I'm less sure that ldapmodify is where the problem lies (rather it's just where I'm seeing it manifest).
Thanks for your help Howard -- if you're at FlossUK again this year I should remember to buy you a pint by way of thanks in general (not just as a bribe for helping me out now :) and do bring the violin again, it's a great way to start a presentation! (Re: your talk about mdb in Edinburgh 2012)
Ah I hadn't submitted a talk for FlossUK this year. Will see if I get sufficiently motivated to come up with one...