I am trying to upgrade from 2.3.42 to 2.4.15 and my setup uses single-master replication over TLS. When I do the upgrade I have noticed that replication fails. I have reproduced the problem in my lab, using a single server and multiple slapd instances, and I get the following error on the slave:
[root@otm-hp11 cnd]# ./slapd -f slapdSlave.conf -d sync -h "ldap://188.8.131.52:20389 ldaps://184.108.40.206:20636"
@(#) $OpenLDAP: slapd 2.4.15 (Feb 25 2009 22:27:30) $
bdb_db_open: warning - no DB_CONFIG file found in directory /opt/nortel/cnd/slave-data: (2).
Expect poor performance for suffix "dc=Nortel,dc=com".
TLS certificate verification: Error, self signed certificate in certificate chain
TLS: can't connect: error:14090086:SSL routines:SSL3_GET_SERVER_CERTIFICATE:certificate verify failed.
slap_client_connect: URI=ldaps://220.127.116.11:10636 DN="cn=replicationagent,ou=replication,dc=nortel,dc=com" ldap_sasl_bind_s failed (-1)
do_syncrepl: rid=983 retrying (4 retries left)
The corresponding trace on the master is:
TLS: can't accept: error:14094418:SSL routines:SSL3_READ_BYTES:tlsv1 alert unknown ca.
Based on the error messages, I thought that there was a problem with the certificates I am using, but when I revert the slapd executable to the old 2.3.42 version, replication succeeds. Were more stringent CA checks added between 2.3.42 and 2.4.15? Note that the same OpenSSL version was used to build both slapd executables (0.9.8b). Also, the same configuration options were used to build both versions.