Ok, I solved my problem now. My cacert.pem was a x509 v3 certificate, with Signature Algorithm: md5WithRSAEncryption. With that cacert I got a "Verification failed" from the gnutls-cli command (but not from the openssl command like posted above).
After creating a new x509 v3 cacert.pem with Signature Algorithm: sha1WithRSAEncryption, the gnutls-cli command succeeds with "Peer's certificate is trusted", and the ldap authentication works fine now on my Ubuntu 8.04 machine. Software: dpkg-query -W -f='${Package} ${Version} ${Source} ${Status}\n' | egrep 'slapd|ldap|gnutls' gnutls-bin 2.0.4-1ubuntu2.6 gnutls13 install ok installed ldap-auth-client 0.5 install ok installed ldap-auth-config 0.5 ldap-auth-client install ok installed ldap-utils 2.4.9-0ubuntu0.8.04.1 openldap2.3 install ok installed libcurl3-gnutls 7.18.0-1ubuntu2.2 curl install ok installed libgnutls13 2.0.4-1ubuntu2.6 gnutls13 install ok installed libldap-2.4-2 2.4.9-0ubuntu0.8.04.1 openldap2.3 install ok installed libnss-ldap 258-1ubuntu3 install ok installed libpam-ldap 184-2ubuntu2 install ok installed -- "TLS: peer cert untrusted or revoked (0x82)" error in Hardy's version of ldap-utils https://bugs.launchpad.net/bugs/257153 You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs