Smartcard authentication [PREMIUM ONLY]

GitLab supports authentication using smartcards.

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. 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, emailAddress=gitlab-user@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;
```
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 (eg. in /etc/nginx/sites-available/gitlab-ssl):

server {
    listen *:3444 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'

  # Port where the client side certificate is requested by NGINX
  client_certificate_required_port: 3444

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

Additional steps when authenticating against an LDAP server