Short Version
How can I configure a CentOS 7 machine with Samba 4.8.0 serving users on Windows 7 clients to authenticate using their domain login credentials (winbindd
and Active Directory) but be authorized (i.e. perform user/group lookup) against a separate OpenLDAP server?
This was easy with CentOS 6 and the Samba fallback mechanism. It seems to be more complicated once winbind must be involved.
Long Version
We have a CentOS 7 machine that needs to share files with Windows 7 machines in an Active Directory domain (that I do not control) for users in the EXAMPLE.COM domain but perform user/group lookup against a separate OpenLDAP server (that I do control) at ldap.mydomain.com. With current versions of CentOS 7, as of Samba 4.8.0, the winbindd fallback is no longer available and winbindd is required.
So we do the following:
- open firewall port 445 (but for testing,
systemctl stop firewalld
) - set SELinux Booleans for sharing home directories (but for testing,
setenforce 0
) - add trust for the certificate authority that certified ldap.mydomain.com (tested and LDAP lookups are functional on the system)
- install packages
samba
,samba-client
,samba-winbind
,samba-winbind-clients
, andsamba-winbind-krb5-locator
net ads join -U 'user'
(the domain allows non-admin creation of machine accounts;net ads testjoin
returns 'Join is OK')authconfig --enablesssd --enablesssdauth --disablemkhomedir --update
Here is the smb.conf
with provisions for winbind, which was not configured by authconfig
above:
[global]
strict locking = no
workgroup = EXAMPLE
server string = Samba Server Version %v
disable netbios = yes
log file = /var/log/samba/log.%m
max log size = 50
security = ads
realm = EXAMPLE.COM
ldap ssl = off
idmap config * : backend = ldap
idmap config * : ldap_url = ldaps://ldap.mydomain.com:636/
idmap config * : ldap_base_dn = dc=mydomain,dc=com
idmap config * : ldap_user_dn = uid=samba,ou=agents,dc=mydomain,dc=com
idmap config * : read only = yes
idmap config * : range = 1000-65535
kerberos method = secrets and keytab
load printers = no
printcap name = /dev/null
printing = bsd
disable spoolss = yes
[home]
comment = Home Directories
path = /home/%U
browseable = no
writable = yes
create mask = 0600
directory mask = 0700
valid users = EXAMPLE\%U
preexec = ls /home/%U
[share]
path = /home/share
writable = yes
valid users = @share
force group = share
create mask = 0660
directory mask = 0770
preexec = ls /home/share
Here is the problem:
smbclient //myhost.fqdn/home -U <user>
performs winbind authentication and successfully connects to the share for any value of<user>
smbclient //myhost.fqdn/share -U <user
performs winbind authentication but fails to determine from ldap.mydomain.com that<user>
is in group 'share', thus returningtree connect failed: NT_STATUS_ACCESS_DENIED
Additional information:
testparm
shows no errors or warningswbinfo -u
returns list of EXAMPLE.COM domain userswbinfo -g
returns list of EXAMPLE.COM domain groups- SSH login of domain users (i.e. ssh user@host) works
log.winbindd-idmap
shows:
[2019/06/08 15:58:23.175342, 3] ../source3/winbindd/idmap.c:397(idmap_init_domain)
idmap backend ldap not found
[2019/06/08 15:58:23.177972, 3] ../lib/util/modules.c:167(load_module_absolute_path)
load_module_absolute_path: Module '/usr/lib64/samba/idmap/ldap.so' loaded
[2019/06/08 15:58:23.179407, 2] ../source3/lib/smbldap.c:847(smbldap_open_connection)
smbldap_open_connection: connection opened
[2019/06/08 15:58:23.340963, 3] ../source3/lib/smbldap.c:1069(smbldap_connect_system)
ldap_connect_system: successful connection to the LDAP server
[2019/06/08 15:58:23.343603, 1] ../source3/winbindd/idmap_ldap.c:484(idmap_ldap_db_init)
idmap_ldap_db_init: failed to verify ID pool (NT_STATUS_UNSUCCESSFUL)
[2019/06/08 15:58:23.343810, 1] ../source3/winbindd/idmap.c:447(idmap_init_domain)
idmap initialization returned NT_STATUS_UNSUCCESSFUL
Setting a higher debug level suggests that the final NT_STATUS_UNSUCCESSFUL comes from an attempt to make changes to the basedn, but I do not understand why idmap backend ldap not found
appears or why Samba/winbind needs to make changes to the LDAP database, particularly when the readonly property is set in smb.conf
. Finally, I am not sure if these lines even explain the problem.
We have a working CentOS 6 deployment that perfectly functions without winbind while performing this split Active Directory authentication with separate LDAP user/group lookup. How can we achieve what we want with Samba 4.8.0 in CentOS 7? Why are the idmap config
lines in smb.conf not instructing Samba to get group membership information from ldap.mydomain.com
?