Linux/SssdADauth

• Using Windows active directory to authenticate Linux users, through sssd

• Example login failure, in correct group but no local account (User was in wrong ldap_search_base)

  Jun 29 02:12:20 arm-p02 sshd[25151]: Invalid user Smitxx from 10.x.x.x port 43508
  Jun 29 02:12:20 arm-p02 sshd[25151]: input_userauth_request: invalid user Smitxxx [preauth]
  Jun 29 02:12:29 arm-p02 sshd[25151]: pam_unix(sshd:auth): check pass; user unknown
  Jun 29 02:12:29 arm-p02 sshd[25151]: pam_unix(sshd:auth): authentication failure; logname= uid=0 euid=0 tty=ssh ruser= rhost=jumphost
  Jun 29 02:12:31 arm-p02 sshd[25151]: Failed password for invalid user Smitxxx from 10.x.x.x port 43508 ssh2

• Test with AD user in correct ldap_search_base but not in correct group ldap_access_filter

  Jun 29 03:08:07 arm-p02 sshd[2630]: pam_sss(sshd:auth): authentication success; logname= uid=0 euid=0 tty=ssh ruser= rhost=jumphost user=SmitX
  Jun 29 03:08:07 arm-p02 sshd[2630]: pam_sss(sshd:account): Access denied for user SmitX: 6 (Permission denied)
  Jun 29 03:08:07 arm-p02 sshd[2630]: Failed password for SmitX from 10.2.1.1 port 53288 ssh2
  Jun 29 03:08:07 arm-p02 sshd[2630]: fatal: Access denied for user SmitX by PAM account configuration [preauth]

• Login working User in ldap_search_base and group for ldap_access_filter

  Jun 29 03:17:27 arm-p02 sshd[4343]: pam_sss(sshd:auth): authentication success; logname= uid=0 euid=0 tty=ssh ruser= rhost=jumphost user=SmitX
  Jun 29 03:17:27 arm-p02 sshd[4343]: Accepted password for SmitX from 10.2.1.1 port 55038 ssh2
  Jun 29 03:17:57 arm-p02 sshd[4343]: pam_systemd(sshd:session): Failed to create session: Connection reset by peer
  Jun 29 03:17:57 arm-p02 sshd[4343]: pam_unix(sshd:session): session opened for user SmitX by (uid=0)
  ...
  Jun 29 03:21:30 arm-p02 sshd[4343]: pam_unix(sshd:session): session closed for user SmitX

• Login working, faster after os upgrade

  Jun 29 04:51:35 arm-p02 sshd[3829]: pam_sss(sshd:auth): authentication success; logname= uid=0 euid=0 tty=ssh ruser= rhost=jumphost user=SmitX
  Jun 29 04:51:35 arm-p02 sshd[3829]: Accepted password for SmitP from 10.1.1.1 port 43760 ssh2
  Jun 29 04:51:35 arm-p02 systemd[1]: Created slice User Slice of SmitX.
  Jun 29 04:51:35 arm-p02 systemd-logind[1950]: New session 5 of user SmitX.
  Jun 29 04:51:35 arm-p02 systemd[1]: Started Session 5 of user SmitX.
  Jun 29 04:51:35 arm-p02 sshd[3829]: pam_unix(sshd:session): session opened for user SmitX by (uid=0)

Config example

• # cat /etc/sssd/sssd.conf

  [sssd]
  config_file_version = 2
  domains = my.domain.com
  services = nss, pam
  full_name_format = %1$s
  
  [nss]
  
  [pam]
  
  [domain/my.domain.com]
  id_provider = ldap
  access_provider = ldap
  ldap_access_filter = (memberOf=CN=Auth-Group,OU=Security,OU=Groups,OU=Production,DC=my,DC=domain,DC=com)
  cache_credentials = True
  ldap_uri = ldaps://ad-server.my.domain.com:636
  ldap_search_base = OU=Business Users,OU=Users,OU=Production,DC=my,DC=domain,DC=com
  ldap_schema = AD
  ldap_default_bind_dn = CN=svc_AcctLinuxLDAP,OU=Service Accounts,OU=Users,OU=Production,DC=my,DC=domain,DC=com
  ldap_default_authtok_type = obfuscated_password
  ldap_default_authtok = AAAxxxx...xxxxw==
  
  # Obtain the CA root certificate for your LDAPS connection.
  ldap_tls_cacert = /etc/pki/tls/certs/cacerts.pem
  ldap_tls_reqcert = allow
  
  # AWS SimpleAD doesn't provide a way to download
  # the CA root certificate at the moment.
  # This setting disables cert verification.
  #ldap_tls_reqcert = allow
  
  # Only if the LDAP directory doesn't provide uidNumber and gidNumber attributes
  ldap_id_mapping = True
  
  # Consider setting enumerate=False for very large directories
  enumerate = False
  
  # Only needed if LDAP doesn't provide homeDirectory and loginShell attributes
  fallback_homedir = /home/%u
  default_shell = /bin/bash

• Create obfuscated bind DN password in config file above with

  sss_obfuscate --domain my.domain.com

• Enable sssd authentication

  authconfig --enablesssd --enablesssdauth --enablemkhomedir --updateall

CategoryLinux