Smartcard authentication (PREMIUM ONLY)

GitLab supports authentication using smartcards.

Existing password authentication

Introduced in GitLab 12.6.

By default, existing users can continue to log in with a username and password when smartcard authentication is enabled.

To force existing users to use only smartcard authentication, disable username and password authentication.

Authentication methods

GitLab supports two authentication methods:

X.509 certificates with local databases.
LDAP servers.

Authentication against a local database with X.509 certificates

Introduced in GitLab Premium 11.6 as an experimental feature.

CAUTION: Caution: Smartcard authentication against local databases may change or be removed completely in future releases.

Smartcards with X.509 certificates can be used to authenticate with GitLab.

To use a smartcard with an X.509 certificate to authenticate against a local database with GitLab, CN and emailAddress must be defined in the certificate. For example:

Certificate:
    Data:
        Version: 1 (0x0)
        Serial Number: 12856475246677808609 (0xb26b601ecdd555e1)
    Signature Algorithm: sha256WithRSAEncryption
        Issuer: O=Random Corp Ltd, CN=Random Corp
        Validity
            Not Before: Oct 30 12:00:00 2018 GMT
            Not After : Oct 30 12:00:00 2019 GMT
        Subject: CN=Gitlab User, [email protected]

Authentication against a local database with X.509 certificates and SAN extension

Introduced in GitLab Premium 12.3.

Smartcards with X.509 certificates using SAN extensions can be used to authenticate with GitLab.

NOTE: Note: This is an experimental feature. Smartcard authentication against local databases may change or be removed completely in future releases.

To use a smartcard with an X.509 certificate to authenticate against a local database with GitLab, in:

GitLab 12.4 and later, at least one of the subjectAltName (SAN) extensions need to define the user identity (email) within the GitLab instance (URI). URI: needs to match Gitlab.config.host.gitlab.
From GitLab 12.5, if your certificate contains only one SAN email entry, you don't need to add or modify it to match the email with the URI.

For example:

Certificate:
    Data:
        Version: 1 (0x0)
        Serial Number: 12856475246677808609 (0xb26b601ecdd555e1)
    Signature Algorithm: sha256WithRSAEncryption
        Issuer: O=Random Corp Ltd, CN=Random Corp
        Validity
            Not Before: Oct 30 12:00:00 2018 GMT
            Not After : Oct 30 12:00:00 2019 GMT
        ...
        X509v3 extensions:
            X509v3 Key Usage:
                Key Encipherment, Data Encipherment
            X509v3 Extended Key Usage:
                TLS Web Server Authentication
            X509v3 Subject Alternative Name:
                email:[email protected], URI:http://gitlab.example.com/

Authentication against an LDAP server

Introduced in GitLab Premium 11.8 as an experimental feature. Smartcard authentication against an LDAP server may change or be removed completely in future releases.

GitLab implements a standard way of certificate matching following RFC4523. It uses the certificateExactMatch certificate matching rule against the userCertificate attribute. As a prerequisite, you must use an LDAP server that:

Supports the certificateExactMatch matching rule.
Has the certificate stored in the userCertificate attribute.

Configure GitLab for smartcard authentication

For Omnibus installations

Edit /etc/gitlab/gitlab.rb:

gitlab_rails['smartcard_enabled'] = true
gitlab_rails['smartcard_ca_file'] = "/etc/ssl/certs/CA.pem"
gitlab_rails['smartcard_client_certificate_required_port'] = 3444

Save the file and reconfigure GitLab for the changes to take effect.

For installations from source

Configure NGINX to request a client side certificate

In NGINX configuration, an additional server context must be defined with the same configuration except:

The additional NGINX server context must be configured to run on a different port:
```
listen *:3444 ssl;
```
It can also be configured to run on a different hostname:
```
listen smartcard.example.com:443 ssl;
```
The additional NGINX server context must be configured to require the client side certificate:
```
ssl_verify_depth 2;
ssl_client_certificate /etc/ssl/certs/CA.pem;
ssl_verify_client on;
```
The additional NGINX server context must be configured to forward the client side certificate:
```
proxy_set_header    X-SSL-Client-Certificate    $ssl_client_escaped_cert;
```

For example, the following is an example server context in an NGINX configuration file (such as in /etc/nginx/sites-available/gitlab-ssl):

server {
    listen smartcard.example.com:3443 ssl;

    # certificate for configuring SSL
    ssl_certificate /path/to/example.com.crt;
    ssl_certificate_key /path/to/example.com.key;

    ssl_verify_depth 2;
    # CA certificate for client side certificate verification
    ssl_client_certificate /etc/ssl/certs/CA.pem;
    ssl_verify_client on;

    location / {
        proxy_set_header    Host                        $http_host;
        proxy_set_header    X-Real-IP                   $remote_addr;
        proxy_set_header    X-Forwarded-For             $proxy_add_x_forwarded_for;
        proxy_set_header    X-Forwarded-Proto           $scheme;
        proxy_set_header    Upgrade                     $http_upgrade;
        proxy_set_header    Connection                  $connection_upgrade;

        proxy_set_header    X-SSL-Client-Certificate    $ssl_client_escaped_cert;

        proxy_read_timeout 300;

        proxy_pass http://gitlab-workhorse;
    }
}

Edit config/gitlab.yml:

## Smartcard authentication settings
smartcard:
  # Allow smartcard authentication
  enabled: true

  # Path to a file containing a CA certificate
  ca_file: '/etc/ssl/certs/CA.pem'

  # Host and port where the client side certificate is requested by the
  # webserver (NGINX/Apache)
  client_certificate_required_host: smartcard.example.com
  client_certificate_required_port: 3443

NOTE: Note Assign a value to at least one of the following variables: client_certificate_required_host or client_certificate_required_port.

Save the file and restart GitLab for the changes to take effect.

Additional steps when using SAN extensions

For Omnibus installations

Add to /etc/gitlab/gitlab.rb:

gitlab_rails['smartcard_san_extensions'] = true

Save the file and reconfigure GitLab for the changes to take effect.

For installations from source

Add the san_extensions line to config/gitlab.yml within the smartcard section:

smartcard:
   enabled: true
   ca_file: '/etc/ssl/certs/CA.pem'
   client_certificate_required_port: 3444

   # Enable the use of SAN extensions to match users with certificates
   san_extensions: true

Save the file and restart GitLab for the changes to take effect.

Additional steps when authenticating against an LDAP server

For Omnibus installations

Edit /etc/gitlab/gitlab.rb:

gitlab_rails['ldap_servers'] = YAML.load <<-EOS
main:
  # snip...
  # Enable smartcard authentication against the LDAP server. Valid values
  # are "false", "optional", and "required".
  smartcard_auth: optional
EOS

Save the file and reconfigure GitLab for the changes to take effect.

For installations from source

Edit config/gitlab.yml:

production:
  ldap:
    servers:
      main:
        # snip...
        # Enable smartcard authentication against the LDAP server. Valid values
        # are "false", "optional", and "required".
        smartcard_auth: optional

Save the file and restart GitLab for the changes to take effect.

Require browser session with smartcard sign-in for Git access

For Omnibus installations

Edit /etc/gitlab/gitlab.rb:

gitlab_rails['smartcard_required_for_git_access'] = true

Save the file and reconfigure GitLab for the changes to take effect.

For installations from source

Edit config/gitlab.yml:

## Smartcard authentication settings
smartcard:
  # snip...
  # Browser session with smartcard sign-in is required for Git access
  required_for_git_access: true

Save the file and restart GitLab for the changes to take effect.