Authentication

Configure custom PAM auth for NICE DCV Server

If you want to customize any steps during PAM authentication, like execute scripts during the login process or connect in remote auth system, you can change the PAM DCV Server file. Please follow the next topics.

  • First, edit the file /etc/dcv/dcv.conf and set or add, if is not active, this line:
    pam-service-name="dcv.custom"
  • Now we need to create the /etc/pam.d/dcv.custom file. To understand the content, please check the next topics. If you do not change the name, the default pam file is /etc/pam.d/dcv.

Trying local auth, SSSD auth and Kerberos auth

  • Create the file /etc/pam.d/dcv.custom with this content:
    auth include password-auth
    account include password-auth
  • Create the file /etc/pam.d/dcv-password-auth with this content:
# Load environment variables
auth        required      pam_env.so

# Introduce a delay on authentication failure to slow down brute-force attempts
auth        required      pam_faildelay.so delay=2000000

# Try local authentication first
# If successful, skip next auth module; if fails, continue to next
auth        [success=1 default=ignore]  pam_unix.so nullok try_first_pass

# If local fails, try SSSD
# If successful, skip next auth module; if fails, continue to next
auth        [success=1 default=ignore]  pam_sss.so use_first_pass

# If SSSD fails, try Kerberos
# If successful, skip next auth module; if fails, continue to next
auth        [success=1 default=ignore]  pam_krb5.so use_first_pass

# If all above fail, deny access
auth        required      pam_deny.so

# Check account validity using local passwd file
account     required      pam_unix.so

# Check account validity using SSSD
# Ignore if user unknown, succeed if check passes, fail otherwise
account     [default=bad success=ok user_unknown=ignore] pam_sss.so

# Check account validity using Kerberos
# Ignore if user unknown, succeed if check passes, fail otherwise
account     [default=bad success=ok user_unknown=ignore] pam_krb5.so

# Check password quality for local users
password    requisite     pam_pwquality.so local_users_only

# Change password in local passwd file
# Use SHA512 hashing, allow empty passwords if configured
password    sufficient    pam_unix.so sha512 shadow nullok use_authtok

# Change password in SSSD
password    sufficient    pam_sss.so use_authtok

# Change password in Kerberos
password    sufficient    pam_krb5.so use_authtok

# If all password changes fail, deny the password change
password    required      pam_deny.so

# Set up kernel keyring for the session
session     optional      pam_keyinit.so revoke

# Apply resource limits from /etc/security/limits.conf
session     required      pam_limits.so

# Register the session with systemd
-session    optional      pam_systemd.so

# Create home directory on first login
session     optional      pam_mkhomedir.so

# Skip session setup for cron jobs
session     [success=1 default=ignore] pam_succeed_if.so service in crond quiet use_uid

# Set up user session (update login records, etc.)
session     required      pam_unix.so

# Set up SSSD session (if SSSD is being used)
session     optional      pam_sss.so

# Set up Kerberos session (if Kerberos is being used)
session     optional      pam_krb5.so

Important: If you are using SSSD, then you need to add dcv.custom PAM file into your SSSD domain config to allow this script:
ad_gpo_map_service = +dcv.custom

Executing a script during auth process

You need to create your dcv.custom file (like was explained in the previous tutorial), but you will add one extra line in the dcv.custom file, like this:

auth required pam_exec.so /usr/bin/dcv_local_sessions
auth include password-auth
account include password-auth

The script /usr/bin/dcv_local_sessions will be executed after sucessful login, but before the end of the auth procedure.

No PEM-encoded certificate found

The error “No PEM-encoded certificate found” means that the server couldn’t load the certificate in file dcv.pem​.

The files must be placed in C:\Windows\System32\config\systemprofile\AppData\Local\NICE\dcv (not in the “private” subdirectory) and must be named dcv.pem and dcv.key. Check that the files are readable by the SYSTEM account.

You can check that the dcv.pem certificate is valid with the following PowerShell command:

[System.Security.Cryptography.X509Certificates.X509Certificate2]::CreateFromCertFile("C:\Windows\System32\config\systemprofile\AppData\Local\NICE\dcv\dcv.pem")

In alternative, you can install the openssl ​CLI tools and run:

openssl x509 -in C:\Windows\System32\config\systemprofile\AppData\Local\NICE\dcv\dcv.pem -text

Turning off the DCV authentication for test purposes

Windows

​To change the authentication method on Windows server-side

  1. Open the Windows Registry Editor.
  2. Navigate to the ​HKEY_USERS​\​S-1-5-18​\​Software​\​GSettings​\​com​\​nicesoftware​\​dcv​\security\
  3. key and select the authentication parameter.​ ​If there is no authentication parameter in the registry key, create one:
    • ​In the left-hand pane, open the context (right-click) menu for the authentication key and​ ​choose New, string value.
    • ​For Name, type authentication and press Enter.
  4. Open the authentication parameter. For Value data, enter either system or none.
  5. Choose OK and close the Windows Registry Editor.

Linux

Edit the /etc/dcv/dcv.conf file and set:

[security] 
authentication=none

Save and close the file. Then restart the DCV server:

systemctl restart dcvserver

Multi-Factor-Authentication (MFA) for DCV

Overview

Multi-Factor-Authentication (MFA) is becoming more and more important to raise the security level of applications. Integration of NICE DCV and EnginFrame with MFA is easy and adds additional security.

MFA typically integrates with PAM on the DCV server side in case of Linux. MFA integrations typically support

  • LDAP
  • Radius

as well as other authentication backends.

Here is the MFA authentication flow with PAM integration using an example MFA application. Other MFA applications like Microsoft Authenticator or OKTA (please see below) are supported as well:

(User logs in)

(User receives a request to acknowledge the login request e.g. on the mobile phone)

(User approves the login by clicking on the green button)

(And gets approved and logged in)

After acknowledging the MFA authorization request in the application e.g. on the mobile phone the login process is finished and the user logged in.

The same approach can be used to apply MFA to authenticate users when login into EnginFrame.

Microsoft Entra ID and MFA

If you want to use MFA from Microsoft Entra, you will need to integrade the Entra ID with your Linux PAM (Pluggable Authentication Modules) using SSSD (System Security Services Daemon) service.

You can do the integration checking the article: https://www.ni-sp.com/knowledge-base/dcv-general/authentication/#h-pam-sssd-entra-id-integration

NICE DCV External Authentication

NICE DCV offers an external authentication mechanism which allows to e.g. verify a token which has been sent with the DCV login request and delegate the authentication to an authentication verification script.

External authentication is e.g. used with the EnginFrame Views session management integrated with DCV to provide single-sign on (SSO) for Linux VDI sessions.

You can read more about NICE DCV external authentication at: https://docs.aws.amazon.com/dcv/latest/adminguide/external-authentication.html. A sampe external authentication implementation python script can be found in the NICE DCV Linux distribution.

Let us know if you have any questions regards MFA integration via our contact form. More background on NICE DCV and NICE DCV Tips and Tricks.

Using Microsoft Active Directory / Entra ID to Linux Authentication

Overview

By default the linux system authentication use the PAM library (ref: what is PAM). We are aware that there is a module called pam_aad (pam_aad) that can be used to directly integrate PAM with AD, however this module is not officialy supported anymore by the community.

To offer a complete and supported AD integration, we can use LDAP (ref: what is LDAP) or SSSD (ref: what is SSSD).

If you already have Open LDAP configured, plase skip the installing topic.

Note: Microsoft Active Directory was renamed to Microsoft Entra ID (ref: active directory renamed)

The Entra ID intgration can be done using:

  • PAM + LDAP, if you already have LDAP installed or want to use LDAP
  • PAM + SSSD, you want a simple way to integrate PAM with Entra ID with any Linux distro
  • PAM + AUTHD, if you are using very recent Debian (12+) and Ubuntu (24.04+)

PAM + LDAP + Entra ID integration

Installing Open LDAP

RedHat based systems, like CentOS

Open LDAP package as removed in EL8, so we will use Symas repository to provide updated Open LDAP package.

Please follow this steps to setup Open LDAP:

  1. Configuring the repository:
    yum erase openldap-clients openldap-servers
    7 version: wget -q https://repo.symas.com/configs/SOFL/rhel7/sofl.repo -O /etc/yum.repos.d/sofl.repo
    8 version: wget -q https://repo.symas.com/configs/SOFL/rhel8/sofl.repo -O /etc/yum.repos.d/sofl.repo
  2. Installing the Open LDAP service:
    yum install symas-openldap-clients symas-openldap-servers
  3. Starting the service:
    systemctl enable --now slapd
  4. Edit the file /etc/openldap/ldap.conf and look for:
    # BASE dc=example,dc=com
    # URI ldap://ldap.example.com ldap://ldap-master.example.com:666
    and replacd with
    BASE dc=my,dc=ldapserver,dc=com
    URI ldap://my.ldapserver.com

    Note: replace my.ldapserver.com URI with your comand and then the BASE config. And pay attention to replace both configs in the rest of this tutorial.
  5. Now execute the command slappasswd and create a password that will be used for Open LDAP root user (olcRootPW):
    slappasswd
    Copy the hash that will be printed.
  6. Create a file callend rootpw.ldif and add this content:
    dn: olcDatabase={0}config,cn=config
    changetype: modify
    add: olcRootPW
    olcRootPW: {SSHA}VoN6YuL6fTIWzT6xy41SpPDrfP4ce1Zx

    Note: The hash {SSHA}VoN6YuL6fTIWzT6xy41SpPDrfP4ce1Zx is just an example. You need to create one for you with slappasswd command.
  7. Then execute this ldif file:
    ldapadd -Y EXTERNAL -H ldapi:/// -f rootpw.ldif
  8. We need to import basic Open LDAP schemes . Please execute the follow commands:
    ldapadd -Y EXTERNAL -H ldapi:/// -f /etc/openldap/schema/cosine.ldif
    ldapadd -Y EXTERNAL -H ldapi:/// -f /etc/openldap/schema/nis.ldif
    ldapadd -Y EXTERNAL -H ldapi:/// -f /etc/openldap/schema/inetorgperson.ldif
    ldapadd -Y EXTERNAL -H ldapi:/// -f /etc/openldap/schema/openldap.ldif
    ldapadd -Y EXTERNAL -H ldapi:/// -f /etc/openldap/schema/dyngroup.ldif
  9. We also need to create a manager user for Open LDAP. We can use same root password if you think it is ok or execute slappasswd command again and create a new password. Create a file called manager.ldif and set this content:
    dn: olcDatabase={2}mdb,cn=config
    changetype: modify
    replace: olcSuffix
    olcSuffix: dc=my,dc=ldapserver,dc=com

    dn: olcDatabase={2}mdb,cn=config
    changetype: modify
    replace: olcRootDN
    olcRootDN: cn=Manager,dc=my,dc=ldapserver,dc=com

    dn: olcDatabase={2}mdb,cn=config
    changetype: modify
    add: olcRootPW
    olcRootPW: {SSHA}VoN6YuL6fTIWzT6xy41SpPDrfP4ce1Zx

    Note: Please remember to replace the domain config (dc=my,dc=ldapserver,dc=com) with your domand
  10. Then you can apply:
    ldapmodify -Y EXTERNAL -H ldapi:/// -f manager.ldif
  11. To create the Organization Group org.ldif file:
    dn: dc=my,dc=ldapserver,dc=com
    objectClass: top
    objectClass: dcObject
    objectclass: organization
    o: IBM RPA Server
    dc: rpa

    dn: cn=Manager,dc=my,dc=ldapserver,dc=com
    objectClass: organizationalRole
    cn: Manager
    description: LDAP Manager

    dn: ou=rpausers,dc=my,dc=ldapserver,dc=com
    objectClass: organizationalUnit
    ou: rpaUsers
  12. Then apply with:
    ldapadd -x -D cn=Manager,dc=my,dc=ldapserver,dc=com -W -f org.ldif

    Note: replace domain config (dc=my,dc=ldapserver,dc=com) with your config.

Setup a LDAP certificate to support LDAPS

For testing purposes we will create the key, then the CSR file, but we will continue with self-signed certificate.

  • Create the req.conf file:
[req]
distinguished_name = req_distinguished_name
req_extensions = v3_req
prompt = no
days = 365

[req_distinguished_name]
C = US
ST = US
L = LA
O = myorg
OU = myorgunit
CN = my.ldapserver.com

[ v3_req ]
basicConstraints       = CA:false
extendedKeyUsage       = serverAuth
subjectAltName         = @sans

[ sans ]
DNS.0 = localhost
DNS.1 = ldap.ldapserver.com
  • To create the CSR:
openssl req -new -out ldaps.csr -newkey rsa:2048 -nodes -sha256 -keyout ldaps.key -config req.conf
  • Check if your CSR file is right:
openssl req -noout -text -in ldaps.csr
  • Verify your private key:
openssl rsa -in ldaps.key -check
  • Finally create the self signed certificate:
openssl x509 -req -days 3650 -in ldaps.csr -signkey ldaps.key -out ldaps.crt
  • And convert the certo to PKCS12 format:
openssl pkcs12 -export -out ldaps.pfx -inkey ldaps.key.temp -in ldaps.crt
  • Edit the file /etc/nslcd.conf and set or add this config:
    tls_reqcert allow

    It will allow self-signed certs.
  • Copy the certs to /etc/openldap/cacerts/
    mkdir -p /etc/openldap/cacerts
    cp ldaps.csr /etc/openldap/cacerts/
    cp ldaps.crt /etc/openldap/cacerts/
    cp ldaps.key /etc/openldap/cacerts/
    cp ldaps.pfx /etc/openldap/cacerts/
  • And then fix the permissions:
    chown -R ldap:ldap /etc/openldap/cacerts/
  • Create a file called certs.ldif with this content:
    dn: cn=config
    changetype: modify
    replace: olcTLSCertificateFile
    olcTLSCertificateFile: /etc/openldap/certs/ldaps.crt

    dn: cn=config
    changetype: modify
    replace: olcTLSCertificateKeyFile
    olcTLSCertificateKeyFile: /etc/openldap/certs/ldaps.key
  • And finally apply the the ldif file:
    ldapmodify -Y EXTERNAL -H ldapi:/// -f certs.ldif
  • Finally, check if the LDAP config is correct with:
    slaptest -u

Integrating LDAP with Microsoft Active Directory / Entra ID

Now you need to follow the official guide to connect Generic LDAP Connector into your LDAP:

Important notes:

  • Microsot does not recommend to use self-signed certificates.
  • You can connect Entra ID with your LDAP using self-signed certificate.
  • Besides you can disable Secure LDAP (LDAPS) in Microsoft Entra ID, do not do that; You can expose your users data withotu encrypting the traffic,

Configuring Linux PAM to use LDAP

There is a PAM module called libpam-ldapd (ref: what is libpam-ldap) that can integrate PAM and LDAP protocol. This PAM module is the newest alternative of old libpam-ldap. This module already come installed with almost all distros, but you can check, usually in /usr/lib64/security/, if you have the pam_ldap.so module. If not, then you need to setup libpam-ldapd package. The name can change according each distro.

libpam-ldapd uses the same backend (nslcd) as libnss-ldapd, and thus also shares the same configuration file (/etc/nslcd.conf).

In order to globally enable LDAP authentication through PAM, configure /etc/pam_ldap.conf and edit the /etc/pam.d/common-* files so that they contain something like the examples below. We say something because it will depends of your distro and your customizations, but is simple.

/etc/pam.d/common-account:

account     required      pam_unix.so
account     sufficient    pam_succeed_if.so uid < 1000 quiet
account     [default=bad success=ok user_unknown=ignore] pam_ldap.so
account     required      pam_permit.so

/etc/pam.d/common-auth:

auth    sufficient      pam_unix.so nullok_secure
auth    requisite       pam_succeed_if.so uid >= 1000 quiet
auth    sufficient      pam_ldap.so use_first_pass
auth    required        pam_deny.so

/etc/pam.d/common-password:

session     required      pam_limits.so
session     required      pam_unix.so
session     optional      pam_ldap.so

Important note: If you have GPO rules being applied from your Active Directory, you must translate the GPO rules to all custom PAM configuration files that you created, specially if you have ad_gpo_default_right configured as Deny. You may need to apply custom PAM scripts into ad_gpo_map_remote_interactive or ad_gpo_map_service. If you have, for example, a custom DCV server PAM config file you need to explicity map the GPO rule with PAM.

PAM + SSSD + Entra ID integration

Overview

Important notes:

  • Direct integration with SSSD works only within a single AD forest by default.
  • Windows supported versions: 2008, 2012 R2, 2016, 2019 and 2022.

Installing and configuring SSSD

RedHat based systems, like CentOS
  • Install the service with the command:
    yum install samba-common-tools realmd oddjob oddjob-mkhomedir sssd sssd-tools adcli krb5-workstation
  • Use the authconfig tool to enable SSSD
    authconfig --enablesssd --update

    This command will update the file /etc/nsswitch.conf to have:
    passwd: files sss
    shadow: files sss
    group: files sss
    netgroup: files sss
  • Edit the file /etc/nsswitch.conf and edit or add, if does not exist:
    services: files sss
  • Edit the file /etc/sssd/sssd.conf (if does not exist, copy from /usr/lib64/sssd/conf/sssd.conf to /etc/sssd/) and look for [sssd] section
  • Add nss as first option:
    services = nss, pam
  • In the same file, look for the [nss] section
  • And configure how SSSD will interact with nss:
    [nss]
    filter_groups = root
    filter_users = root
    entry_cache_timeout = 300
    entry_cache_nowait_percentage = 75
  • Enable and restart the sssd service:
    systemctl enable sssd.service
    systemctl restart sssd.service

    Note: If the SSSD service fail to start, then please check what is the problem with the command: sssctl config-check

Configure SSSD to connect into Microsoft Entra ID

To join into Active Directory domain, follow these steps:

  • First try to discover the AD domain to check if you are able to join into the domain:
    realm discover ad.example.com
  • Then join into the domain:
    realm join ad.example.com
  • To check if you it worked, please try to get any info from Active Directory user, like this:
    getent passwd administrator@ad.example.com

You can check more details under this RedHat AD joining tutorial.

Configure PAM to use SSSD

  • Execute the command below to enable SSSD for auth
    authconfig --enablesssdauth --update

    This will update the files /etc/pam.d/system-auth and /etc/pam.d/password-auth with pam_sss module:
    [... file truncated ...]
    auth required pam_env.so
    auth sufficient pam_unix.so nullok try_first_pass
    auth requisite pam_succeed_if.so uid >= 500 quiet
    auth sufficient pam_sss.so use_first_pass
    auth required pam_deny.so
    [... file truncated ...]
  • Edit the file /etc/sssd/sssd.conf and look for [sssd] section
  • Check if pam service is listed, like this:
    [sssd]
    [... file truncated ...]
    services = nss, pam
  • In the same file, look for the [pam] section and configure how SSSD will interact with PAM:
    [pam]
    offline_credentials_expiration = 2
    offline_failed_login_attempts = 3
    offline_failed_login_delay = 5
  • Then restart the SSSD service:
    systemctl restart sssd.service

    Note: If the SSSD service fail to start, then please check what is the problem with the command: sssctl config-check

Important note: If you have GPO rules being applied from your Active Directory, you must translate the GPO rules to all custom PAM configuration files that you created, specially if you have ad_gpo_default_right configured as Deny. You may need to apply custom PAM scripts into ad_gpo_map_remote_interactive or ad_gpo_map_service. If you have, for example, a custom DCV server PAM config file you need to explicity map the GPO rule with PAM.

AUTHD + Entra ID integration

Overview

For Debian based distros, like Ubuntu, there is one alternative called authd (ref: https://github.com/ubuntu/authd).

Debian and Ubuntu

To integrate authd with your Linux, please setup the package below.

apt update && apt -y install authd

This command will install the authd the required modules for PAM and NSS and its dependencies.

For NSS it’ll update the file /etc/nsswitch.conf and add the service authd for the databases password, group and shadow.

For PAM it’ll update the files /etc/pam.d/common-auth, /etc/pam.d/common-account and /etc/pam.d/common-password to include the authd module.

Connecting authd with Microsoft Entra ID

Now you need to follow the Microsoft Entra ID official documentation to join into your domain: https://learn.microsoft.com/pt-br/entra/identity/domain-services/join-ubuntu-linux-vm