Hi,

the internet is full of "tips" to solve the above problem. I'm pulling my hairs and can not find the real issue since days. any help is greatly appreciated.

--------- enable_ssl.ldiff ---------------
dn: cn=config
changetype: modify
add: olcTLSCertificateKeyFile
olcTLSCertificateKeyFile: /etc/ldap/key.key

dn: cn=config
changetype: modify
add: olcTLSCertificateFile
olcTLSCertificateFile: /etc/ldap/cert.pem
--------- enable_ssl.ldiff ---------------

# ls -alh /etc/ldap/cert.pem /etc/ldap/key.key
-rwxrwxrwx 1 root root 1,1K Mär  1 21:43 /etc/ldap/cert.pem
-rwxrwxrwx 1 root root 1,7K Mär  1 21:21 /etc/ldap/key.key

# openssl rsa -noout -modulus -in /etc/ldap/key.key | openssl md5
(stdin)= 45b4165df200817a20857fb453acd33e
# openssl x509 -noout -modulus -in /etc/ldap/cert.pem | openssl md5
(stdin)= 45b4165df200817a20857fb453acd33e

# head -n2 /etc/ldap/cert.pem
-----BEGIN CERTIFICATE-----
MIIFmDCCBICgAwIBAgIQBFMR6HMGTGjQIjSj4sQX+TANBgkqhkiG9w0BAQsFADBu
# head -n2 /etc/ldap/key.key
-----BEGIN RSA PRIVATE KEY-----
MIIEowIBAAKCAQEAvrDddMwXoy10diqDpqd45jaC8HiGKz7KC5X3W0ZLvCshylu0


ldapmodify -Y EXTERNAL -H ldapi:/// -f enable_ssl.ldif  -v

# ldapmodify -Y EXTERNAL -H ldapi:/// -f enable_ssl.ldif  -v
ldap_initialize( ldapi:///??base )
SASL/EXTERNAL authentication started
SASL username: gidNumber=0+uidNumber=0,cn=peercred,cn=external,cn=auth
SASL SSF: 0
add olcTLSCertificateKeyFile:
/etc/ldap/key.key
modifying entry "cn=config"
ldap_modify: Other (e.g., implementation specific) error (80)

I can however modify other values like olcLogLevel without problems.

Debian 10 latest:
2.4.47+dfsg-3+deb10u6
# slapd -VVV
@(#) $OpenLDAP: slapd  (Feb 14 2021 18:32:34) $
Debian OpenLDAP Maintainers <pkg-openldap-devel@lists.alioth.debian.org>

Included static backends:
    config
    ldif

Stefan.