On Sun, 16 Oct 2011, Hugo Deprez wrote:
It seems that the proper configuration for my case is :
syncrepl rid=003 provider=ldaps://ldap.mydomain.fr:1024/ type=refreshOnly retry="60 10 600 +" interval=00:00:00:10 searchbase="dc=mydomain,dc=fr" scope=sub schemachecking=on bindmethod=simple tls_reqcert=never binddn="cn=syncrepluser,o=others,dc=mydomain,dc=fr" credentials=my_password
It works, but I am confuse with those parameters. If I understand well, I will never use TLS here, but only ssl ? Hence, it was a TLS issue ?
No, you're using TLS. You're just not using the StartTLS operation.
There are two ways to use SSL/TLS: "negotiate-on-connect" and "upgrade from clear". The former is what you get when you use an ldaps:// URL, where the first data the client sends is the raw SSL/TLS ClientHello packet. The latter is what you get when you use an ldap:// URL and have starttls=yes or starttls=critical, where the first data the client sends is LDAP protocol data in the clear, including a StartTLS request. If the server sends a success response to that StartTLS request, then the client starts the SSL/TLS handshake with its ClientHello packet.
This should answer why it failed when you tried to combine an ldaps:// URL with starttls=yes: the exchange was already using SSL/TLS and (rightly) libldap won't let you negotiate multiple levels of SSL/TLS encryption.
(You may note that I write "SSL/TLS". That's because they're just different versions of the same protocol. Using 'SSL' as a shorthand for "negotiate on connect" and 'TLS' for "upgrade from clear" is poor naming, as the choice of method is orthogonal to the protocol version. Your ldaps:// connection is probably negotiating the TLS 1.0 protocol (aka SSL version 3.1), just as an ldap:// connection using StartTLS may, on a poorly configured server, negotiate SSL 3.0)
Next: the fact that you need tls_reqcert=never for TLS negotiation to succeed strongly suggests the problem is either a) the subject and subjectAltName of the cert don't match the hostname in the URL, OR b) the client doesn't have the self-signed CA cert at the root of the signing chain for the server's cert.
Those are both necessary to protect the server against Man-in-the-Middle attacks.
(It used to be that tls_reqcert=allow would disable check (b) and only perform check (a), or at least that was the case when using the OpenSSL crypto backend, but that behavior has apparently been removed from the version in git as of August. Given the vagaries of the error reporting of the underlying crypto libraries, this was a useful tool in tracking down which check was causing TLS failures. Oh well.)
So, does the server's certificate subject or subjectAltName match the hostname from the URL the client is using? Have you verified that the CA at the root of the server's cert's chain really is configured for the client?
Philip Guenther