Samba and ntlm for Windows clients


Use one or the other:

1. Insecure but fast, in /etc/samba/smb.conf:

ntlm auth = yes

2. Best, on client Windows machine:

Windows Registry Editor Version 5.00


Samba and ntlm

With the published “ETERNALBLUE” vulnerability (CVE-2017-0146) a few months ago, the effects finally trickled down to the default settings for samba in CentOS 7.

After updating to samba 4.6.2, I was unable to access my samba share from a Windows client (using my freeipa credentials).

Here’s what I found in /var/log/samba/log.lsasd after setting [global] log level = 3:

  check_ntlm_password:  Authentication for user [bgstack15] -> [bgstack15] FAILED with error NT_STATUS_WRONG_PASSWORD
[2017/10/01 16:45:54.106771,  2, pid=5289] ../auth/gensec/spnego.c:768(gensec_spnego_server_negTokenTarg)
[2017/10/01 16:45:54.106860,  3, pid=5289] ../source3/smbd/smb2_server.c:3097(smbd_smb2_request_error_ex)
  smbd_smb2_request_error_ex: smbd_smb2_request_error_ex: idx[1] status[NT_STATUS_LOGON_FAILURE] || at ../source3/smbd/smb2_sesssetup.c:134
[2017/10/01 16:45:54.107513,  3, pid=5289] ../source3/smbd/server_exit.c:246(exit_server_common)
[2017/10/01 16:45:54.113588,  3, pid=5249] ../source3/lib/util_procid.c:54(pid_to_procid)
  pid_to_procid: messaging_dgm_get_unique failed: No such file or directory

After lots and lots of research, I finally found the answer at the FreeBSD forum! Gotta love the FreeBSD folks; they keep us all sane and grounded in free and open computing.
Just add ntlm auth = yes to your [global] section of smb.conf!

However, I looked it up and that enables samba to accept ntlmv1, which was the vulnerable protocol based on that CVE I mentioned earlier in this article.

I wanted to find out how to stick to ntlmv2 authentication, if possible, and I did discover it! You can just configure your Windows clients to use the more secure settings either using the registry or the graphical secpol.msc tool.
For the Local Security Policy (secpol.msc) tool, navigate to Security Settings->Local Policies->Security Options->”Network security: LAN Manager authentication level.” Set it to “Send LM & NTLM – use NTLMv2 session security if negotiated.”

secpol.msc utility showing directory tree navigated to Network security: LAN Manager authentication level setting
Local Security Policy window with setting

To automate this setting, you can make a registry file such as ntlmv2.reg with the following contents:

Windows Registry Editor Version 5.00


I recognize this location from when I’ve adjusted it in the past, at a place that would not have been affected by this vulnerability or its remediation because they were forcing NTLMv2 years ago on the workstations.



      1. Samba quick answer
      2. Client secpol.msc answer
      3. Client registry answer

Enabling mkhomedir on Ubuntu for FreeIPA

The story

In my endeavors to practice with FreeIPA, I tested the Ubuntu port of freeipa. There is a known bug where the –mkhomedir option of the ipa-client-install command for Ubuntu does not actually enable making homedirs for users on first login.

The solution

apt-get install freeipa-client
th="$( hostname --fqdn )"; case "${th}" in *.*) :;; *) th="${th}.$( awk '/search/ {print $2}' /etc/resolv.conf )";; esac;
ipa-client-install --mkhomedir --force-ntpd --enable-dns-updates --hostname "${th}"
sed -i -r -e 's/Default:\s\w+/Default: yes/;' /usr/share/pam-configs/mkhomedir
pam-auth-update # and add the homedir option manually because it cannot be scripted.




Generate certificate with SubjectAltName attributes in FreeIPA


If you want to serve webpages with ssl certificates that have Subject Alternative Names, and you use FreeIPA, you will need to take a few steps to make this possible. If you got to this page, you probably already know the importance of SAN on a cert.

This document will demonstrate how to get IPA to sign a certificate that has the ever-important SubjectAltName.

Example environment

Freeipa domain is at

Host is serving https, and I want to also serve on other domain names:

You don’t even need to have all the SANs in the same domain!

Generate certificate with SAN in freeipa

Generate private key

openssl genrsa -aes256 -out /root/certs/ 2048

Use a simple passphrase you can remember.

Generate certificate signing request

Before you generate the csr, you will need to modify the default openssl.cnf file so it will make a csr with Subject Alternative Names.
In CentOS 7, that file is /etc/pki/tls/openssl.cnf.
In section [req] add line

req_extensions = v3_req

In section [ v3_req ] add lines (to add a new section as well)

subjectAltName = @alt_names

DNS.1 =
DNS.2 =
DNS.3 =
DNS.4 =

You can also include IP.1 = entries.
On my CentOS 7 system, here is the diff:

# diff /etc/pki/tls/openssl.cnf /etc/pki/tls/openssl.cnf.2017-05-19.01 
< req_extensions = v3_req # The extensions to add to a certificate request --- > # req_extensions = v3_req # The extensions to add to a certificate request
< subjectAltName = @alt_names
< [alt_names]
< DNS.1 =
< DNS.2 =
< DNS.3 =
< DNS.4 =


Sign the certificate

In the web UI, you can navigate to Identity -> Services -> principal HTTP/
Select the Actions button, and then New Certificate.
Paste the contents of the csr file.

Retrieve the certificate

In the web UI, under the section Service Certificate, select the Actions button -> Get certificate. You can copy the text and save it in the terminal.



  1. Generate CSR with SAN
  2. Generate each host and HTTP service
  3. Generate CSR

Samba share with freeipa auth

Use FreeIPA Authentication for Samba CIFS Shares for Non-domain Windows Clients

I couldn’t find a singular place on the Internet for a descriptive guide of how to configure samba to use freeipa authentication for cifs shares for non-domain Windows clients.
There are guides out there for freeipa cross-domain trust, so you can share with a domain-joined Windows client, including

This document will show you how to set up Samba 4.4.4 to use FreeIPA 4.4.0 usernames and passwords to allow Windows clients to connect to cifs shares.

Example environment

  • Freeipa domain is
  • A freeipa master on CentOS7
  • A freeipa replica on CentOS7
  • Samba server will go on host2.vm.examplecom.
  • Windows client is

Samba share with freeipa auth

Install freeipa server (and replica)

You need a working freeipa environment, which is outside the scope of this document. A quick sample installation process is:

firewall-cmd --permanent --add-service=freeipa-ldap --add-service=freeipa-ldaps --add-service=ntp --add-service=dns --add-service=dhcp --add-service=kerberos
firewall-cmd --reload

yum install -y ipa-server ipa-client
ipa-server-install -r VM.EXAMPLE.COM -n --mkhomedir --hostname="$( hostname --fqdn )" --admin-password='adminpassword' --ds-password='dspassword'

firewall-cmd --permanent --add-service=freeipa-ldap --add-service=freeipa-ldaps --add-service=ntp --add-service=dns --add-service=dhcp --add-service=kerberos
firewall-cmd --reload

yum install -y ipa-server ipa-client
ipa-client-install --mkhomedir --force-ntpd --enable-dns-updates
ipa-replica-install --setup-ca --mkhomedir

Install samba server

Install the samba packages.

yum -y install samba samba-client sssd-libwbclient

Create the cifs principal for samba on one of the ipa controllers.

# run on an ipa controller. This principal name is "service/hostname"
ipa service-add cifs/

Fetch the keytab to the samba server. In this example, it’s the same as the replica.

# on samba server
kinit -kt /etc/krb5.keytab
ipa-getkeytab -s -p cifs/ -k /etc/samba/samba.keytab
setsebool -P samba_enable_home_dirs on &


Install adtrust components

On the freeipa controller

yum -y install ipa-server-trust-ad
ipa-adtrust-install --add-sids

I recommend running this interactively, as shown above. Let it overwrite your samba config. It will configure it to use the registry, and we will rewrite it to suit the demands here.
The ipa-adtrust-install command generates the records you need to add to dns. They will look like:

Add the following service records to your DNS server for DNS zone 86400 IN SRV 0 100 389 86400 IN SRV 0 100 88 86400 IN SRV 0 100 88 86400 IN SRV 0 100 389 86400 IN SRV 0 100 88 86400 IN SRV 0 100 88

I successfully added them just fine by pasting them into my zone file and running rndc reconfig or systemctl restart named.
The adtrust mechanism adds new attributes to each user and group, specifically ipaNTSecurityIdentifier (the SID) and ipaNTHash. Technically the ipaNTHash can only be generated when the user changes passwords.

On the samba server

Install the ipa-server-trust-ad package on the samba server. You need this package there to get the ipasam config option in smb.conf.

yum -y install ipa-server-trust-ad

Open the firewall for the ports mentioned in the output of the command. You can use this script.

touch "${tf}"; chmod 0644 "${tf}"; chown root:root "${tf}"; restorecon "${tf}"
cat <<EOFXML > "${tf}"
<?xml version="1.0" encoding="utf-8"?>
  <short>IPA and Samba</short>
  <description>This service provides the ports required by the ipa-adtrust-install command.</description>
  <port protocol="tcp" port="135"/>
  <port protocol="tcp" port="138"/>
  <port protocol="tcp" port="139"/>
  <port protocol="tcp" port="445"/>
  <port protocol="tcp" port="1024-1300"/>
  <port protocol="udp" port="138"/>
  <port protocol="udp" port="139"/>
  <port protocol="udp" port="389"/>
  <port protocol="udp" port="445"/>
systemctl restart firewalld
firewall-cmd --permanent --add-service=freeipa-samba
firewall-cmd --reload
echo done

Allow samba to read passwords

This is the magic part that is so hard to find on the Internet.
You will need to give special permissions to the samba service to read user passwords.

ipa permission-add "CIFS server can read user passwords" \
   --attrs={ipaNTHash,ipaNTSecurityIdentifier} \
   --type=user --right={read,search,compare} --bindtype=permission
ipa privilege-add "CIFS server privilege"
ipa privilege-add-permission "CIFS server privilege" \
   --permission="CIFS server can read user passwords"
ipa role-add "CIFS server"
ipa role-add-privilege "CIFS server" --privilege="CIFS server privilege"
ipa role-add-member "CIFS server" --services=cifs/



If you use ldapsearch with kerberos authentication (after a kinit admin, of course), you can see attributes about users.

ldapsearch -Y gssapi "(uid=username)"

Even if the user has generated a new password since the adtrust installation, even the admin cannot see the ipaNTHash attribute.
To confirm the samba service can read the ipaNTHash, use its keytab and search for that attribute.

# on the samba server, so
kdestroy -A
kinit -kt /etc/samba/samba.keytab cifs/
ldapsearch -Y gssapi "(ipaNTHash=*)" ipaNTHash

Configure samba to use freeipa auth

When freeipa adjusts the samba config, it will just make it use the registry backend. You can view the equivalent conf file with testparm.
Here is a complete /etc/samba/smb.conf.

touch "${tf}"; chmod 0644 "${tf}"; chown root:root "${tf}"; restorecon "${tf}"
cat <<EOFCONF > "${tf}"
	debug pid = yes
	workgroup = VM
	domain master = Yes
	ldap group suffix = cn=groups,cn=accounts
	ldap machine suffix = cn=computers,cn=accounts
	ldap ssl = off
	ldap suffix = dc=vm,dc=example,dc=com
	ldap user suffix = cn=users,cn=accounts
	log file = /var/log/samba/log
	max log size = 100000
	domain logons = Yes
	registry shares = Yes
	disable spoolss = Yes
	dedicated keytab file = FILE:/etc/samba/samba.keytab
	kerberos method = dedicated keytab
	#passdb backend = ipasam:ldapi://%2fvar%2frun%2fslapd-VM-EXAMPLE-COM.socket
	#passdb backend = ldapsam:ldapi://%2fvar%2frun%2fslapd-VM-EXAMPLE-COM.socket
	passdb backend = ipasam:ldap:// ldap://
	security = USER
	create krb5 conf = No
	rpc_daemon:lsasd = fork
	rpc_daemon:epmd = fork
	rpc_server:tcpip = yes
	rpc_server:netlogon = external
	rpc_server:samr = external
	rpc_server:lsasd = external
	rpc_server:lsass = external
	rpc_server:lsarpc = external
	rpc_server:epmapper = external
	ldapsam:trusted = yes
	idmap config * : backend = tdb

	ldap admin dn = cn=Directory Manager

	comment = Home Directories
	valid users = %S, %D%w%S
	browseable = No
	read only = No
	inherit acls = Yes
systemctl restart smb.service


Get localsid

Get the local SID

net getlocalsid

Changing ipa domains

It’s possible that if you change ipa domains, the sssd cache is not cleared and you will have cached information for the old domain which can prevent user authentication from happening. You can just clear the cache directory manually and restart sssd.

rm -rf /var/lib/sss/db/*
systemctl restart sssd.service




  1. install samba and kerberize it
  2. add cifs/servername entry
  3. cifs service needs custom privilege to read password
  4. Each user must generate a new password
  5. Seminal article about freeipa and samba integration
  6. Changing ipa domains

Freeipa client uninstall and reinstall

If you are changing ipa domains on a client, you first uninstall the client.

ipa-client-install --uninstall

Then you install in the new domain. (The lack of options here indicates it will search dns, so make sure your _kerberos entries are correct!)

ipa-client-install --mkhomedir --force-ntpd --enable-dns-updates

If you have problems with user accounts on the client for the new domain, it’s possible you need to manually clear out the sss cache to remove traces of the old domain.

rm -rf /var/lib/sss/db/*
systemctl restart sssd.service




New user in freeipa has plain bash shell instead of reading .bashrc

So you have a new user in freeipa, and he can successfully log in to a freeipa client. And you know for certain you executed ipa-client-install with the –mkhomedir option. But when you open a terminal as the new user, it shows you the boring bash prompt ‘bash-4.1$’ or whatever version.

You checked the /etc/skel, and it has a valid .bashrc file, and when you dot source your own ~/.bashrc, it then loads the prompt you expect.

Here’s your issue: do a getent passwd username. Look at the login shell of the user. It’s going to be the default /bin/sh. Just change it in ipa to be /bin/bash! An sss_cache -E command was not enough; you have to log out and then back in to have it take effect. It’s probably because the terminal emulator is being called from a process that was started before the account was changed.