Tag Archive: syncrepl

A few weeks on since my last post (https://tickett.wordpress.com/2014/08/14/synology-directory-openldap-replication/) I have found a few bugs, fixed a few more issues and hopefully have a fully working solution.

One of issues with my previous post (that i’m not going to go into at the moment) was that I hadn’t cross-compiled openssl and cyrus-sasl2 so my version of slapd didn’t support either. I think i’ve now resolved this and you can download my latest slapd here: https://dl.dropboxusercontent.com/u/713/slapd

#1- I needed the slave to refer changes to the master

Documentation and discussion everywhere seems to suggest simply adding a line to the slave slapd.conf;

updateref ldap://

Would ensure any changes were written to the master but I couldn’t get this working (even with debug enabled). The only error I could really find (from memory) was an err=49 which I believe refers to invalid credentials but i’m unsure which credentials or how this is possible.

After further research, I found that there is an alternatively openldap configuration referred to as n-way multi master. Rather than specifying a master and slave, both nodes are masters and changes are replicated both ways. This was relatively easy to setup and “just worked” (not to mention, a better solution as before it was possible the “master” server would be unreachable (if the site-to-site VPN was down) and changes would fail).

You will find config details for n-way multi master / mirrormode in my next blog post.

#2- Unable to access shares after password change (from windows/pGina) with error “Element Not Found”

This was a real curve ball. Google sent me in completely the wrong direction, but I recalled a discussion about multiple passwords being stored in the LDAP database, which led me to wonder if the userPassword wasn’t the only field needing to be updated.

A colleague stumbled across the documentation for pGina fork: http://mutonufoai.github.io/pgina/documentation/plugins/ldap.html which shows a rather more complete “Change Password” configuration for the LDAP plugin. Unfortunately pGina main doesn’t support the DES or Timestamp methods so we couldn’t configure sambaLMPassword, shadowLastChange or sambaPwdLastSet, but adding sambaNTPassword (MD4) alongside userPassword (SHA1) seems to have done the trick.

#3- Data was replicating but the users could not login

I’m not sure exactly how I figured this one out. I think I had a vague recollection of reading a discussion about passwords not replication because default permissions do not allow them to be read from the database.

I added a line in slapd.conf above the existing ACL include;

include /usr/syno/etc/openldap/acls.conf
include /usr/syno/etc/openldap/slapd-acls.conf

The contents of which;

access to attrs=userPassword,sambaLMPassword,sambaNTPassword
     by dn.base="cn=replication,cn=users,dc=example,dc=com" write

Allow the password to be read from the database by the replication user.

This drove me close to insanity, but I got there eventually!

I found an old discussion on the Synology forum http://forum.synology.com/enu/viewtopic.php?f=183&t=55020 and was optimistic it’d be pretty simple. The thread talks about compiling a later version of OpenLDAP from source, but the version included (in DSM5.0) is later than that discussed;

file-20> slapd -VV
@(#) $OpenLDAP: slapd 2.4.34 (Feb 27 2014 03:17:07) $

I tried configuring my provider and consumer using the example and referring to http://www.openldap.org/doc/admin23/syncrepl.html but wasn’t getting anywhere (after changing slapd.conf I would disable and re-enable the LDAP server through the web ui). I was getting an error “Permission denied. Please contact the server administrator.” and an entry in /var/log/messages;

file-20> tail /var/log/messages
Aug 14 21:51:59 file-20 ldap.cgi: ldap_server_default_add.c:146 add [admin] to [cn=Directory Operators,cn=groups,dc=example,dc=com] failed, ldap_insufficient_access (53)

Oddly the slapd process continues to run but no replication is taking place. I believed the error might be because the admin account is locked in some way and wont allow any modification. I tried adding a filter;


This prevented the error message popping up and the error in /var/log/messages but still no replication was taking place.

I imagine it would have been a trivial task on a standard Linux distribution but it seems OpenLDAP has been compiled in a manner which does not allow debug;

file-20> slapd -d 1
must compile with LDAP_DEBUG for debugging

So there’s no real feedback as to what is (or isn’t) working.

After blindly fumbling around for hours I decided to try and compile myself so I could debug. This itself was a mammoth chore!

I wanted to stick with the same version currently running on DSM5.0 so started with the source for 2.4.34 from http://www.openldap.org/software/download/OpenLDAP/openldap-release/

In order to cross compile I followed the Synology 3rd-Party Package Developers guide; http://www.synology.com/en-uk/support/third_party_app_int. I had a spare ubuntu machine I could use for compiling… I needed the DSM5.0 toolchain from http://sourceforge.net/projects/dsgpl/files/DSM%205.0%20Tool%20Chains/ as i’m using the DS214 which apparently has a marvell amanda xp processor. And extracted the archive;

tar zxpf gcc464_glibc215_hard_armada-GPL.tgz –C /usr/local/

Then Berkeley DB 5.1.25 from http://pkgs.fedoraproject.org/repo/pkgs/libdb/db-5.1.25.tar.gz/06656429bfc1abb6c0498eaeff70cd04/

tar xvfdb-5.1.25.tar.gz
cd db-5.1.25
cd build_unix
export CC=/usr/local/arm-marvell-linux-gnueabi/bin/arm-marvell-linux-gnueabi-gcc
export LD=/usr/local/arm-marvell-linux-gnueabi/bin/arm-marvell-linux-gnueabi-ld
export RANLIB=/usr/local/arm-marvell-linux-gnueabi/bin/arm-marvell-linux-gnueabi-ranlib
export CFLAGS="-I/usr/local/arm-marvell-linux-gnueabi/arm-marvell-linux-gnueabi/libc/include -mhard-float -mfpu=vfpv3-d16"
export LDFLAGS="-L/usr/local/arm-marvell-linux-gnueabi/arm-marvell-linux-gnueabi/libc/lib"
../dist/configure --host=armle-unknown-linux --target=armle-unknown-linux --build=i686-pc-linux --prefix=/usr/local 

I also had to install;

sudo apt-get install lib32z1

Now I was able to configure OpenLDAP;

export LDFLAGS="-L/usr/local/lib -L/usr/local/BerkeleyDB.5.1/lib -R/usr/local/lib -R/usr/local/BerkeleyDB.5.1/lib"
export LD_LIBRARY_PATH=/usr/local/BerkeleyDB.5.1/lib
export LD_RUN_PATH=/usr/local/BerkeleyDB.5.1/lib
export CPPFLAGS="-I/usr/local/BerkeleyDB.5.1/include"
./configure --host=armle-unknown-linux --target=armle-unknown-linux --build=i686-pc-linux --prefix=/usr/local --with-yielding-select=no --enable-crypt

But when I tried to;

make depend

I received an error; cross compile openldap error: undefined reference to `lutil_memcmp’ – http://zhuqy.wordpress.com/2010/04/22/cross-compile-openldap-error-undefined-reference-to-lutil_memcmp/ put me straight- I just had to comment out a line from include/portable.h;


make was now successful and I moved my newly compiled slapd to the synology diskstation, chown’d & chmod’d it,  and tested debug… we see an instant result;

file-20> chown root:root slapd.me
file-20> chmod 755 slapd.me
file-20> slapd.me -d 1
ldap_init: trying /usr/local/etc/openldap/ldap.conf
ldap_init: HOME env is /root
ldap_init: trying /root/ldaprc

Now I disabled the directory server in the web ui and instead ran my new version from the commandline with debug 1;

./slapd.me -d 1 -f /usr/syno/etc/openldap/slapd.conf

It failed with an error referring to;

password-hash {CRYPT}

Turns out I had to recompile slapd with –enable-crypt. I copied the newly compiled slapd over, ran again with -d 1 and now I could see it failing with error relating to an invalid filter;


So I removed this… Try again, now;

ldap_sasl_bind_s failed

I think that sent me in the wrong direction (I thought it was an ssl/tls/authentication issue) and I spent hours messing with certificates, unsupported tls configuration parameters etc but got nowhere. Eventually I determined this error essentially means “can’t connect”. Eventually I tried without ssl and as if by magic everything sprung to life!

Here are the lines I added to the default slapd.conf on the provider;

index entryCSN eq
index entryUUID eq

overlay syncprov
syncprov-checkpoint 100 10
syncprov-sessionlog 10

And the consumer;

index entryCSN eq
index entryUUID eq

syncrepl rid=20
 retry="60 +"

If you want to download my compiled version of slapd you can find it here; https://www.dropbox.com/s/sfb06uo0leqxqq9/slapd

I hope this will help you!

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