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SSSD - Unable to Authenticate Against Google LDAP After 20.04 Upgrade - Could not start TLS encryption. unknown error

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I'm trying to authenticate against Google LDAP (G Suite/Google Admin) to allow my clients to log in using their Google credentials. I have no visibility on the LDAP side of things I can only generate the cert/key combo in Google Admin.

This was working well for me on 18.04, but with the upgrade to 20.04 I cannot get it to work. Additionally, it does work for me in other distributions (Fedora) I've included some details below. I read a Canonical post about TLS 1.X and below being disabled with 20.04; does that mean this could be a cipher suite issue?

Error Message

systemctl status sssd

● sssd.service - System Security Services Daemon Loaded: loaded (/lib/systemd/system/sssd.service; enabled; vendor preset: enabled) Active: active (running) since Mon 2021-08-02 15:38:22 EDT; 6s ago Main PID: 3165 (sssd) Tasks: 4 (limit: 9043) Memory: 37.3M CGroup: /system.slice/sssd.service ├─3165 /usr/sbin/sssd -i --logger=files ├─3167 /usr/libexec/sssd/sssd_be --domain mydomain.com --uid 0 --gid 0 --logger=files ├─3168 /usr/libexec/sssd/sssd_nss --uid 0 --gid 0 --logger=files └─3169 /usr/libexec/sssd/sssd_pam --uid 0 --gid 0 --logger=files

Aug 02 15:38:21 JY2D353 systemd[1]: Starting System Security Services Daemon...

Aug 02 15:38:21 JY2D353 sssd[3165]: Starting up

Aug 02 15:38:22 JY2D353 sssd_be[3167]: Starting up

Aug 02 15:38:22 JY2D353 sssd_pam[3169]: Starting up

Aug 02 15:38:22 JY2D353 sssd_nss[3168]: Starting up

Aug 02 15:38:22 JY2D353 sssd_be[3167]: Could not start TLS encryption. unknown error

Aug 02 15:38:22 JY2D353 systemd[1]: Started System Security Services Daemon.

Last Working Config

  • Ubuntu 18.04
  • SSSD 1.16.0
  • Followed instructions located here

I am still able to successfully authenticate using this setup.

Current Configuration

  • Ubuntu 20.04

  • SSSD 2.4.0

  • Same configuration

Logs/conf

etc/sssd.conf

sssd_mydomain.com.log

sssd.log

sssd_pam.log

sssd_nss.log

openssl s_client

Score:0
my flag

This is an issue with TLS 1.3 and google requiring SNI, which apparently isn't properly supported in Ubuntu 20. A workaround which seems to be working for me is to add to the domain section of sssd.conf:

ldap_tls_cipher_suite = NORMAL:!VERS-TLS1.3

which forces TLS1.2 and removes the SNI issue.

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