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SSL settings

Omnibus-gitlab ships with the official CAcert.org collection of trusted root certification authorities which are used to verify certificate authenticity.

For installations that use self-signed or custom certificates, Omnibus-gitlab provides a way to manage these certificates. For more technical details how this works, see the details at the bottom of this page.

Install custom certificate authorities:

Starting from GitLab version 8.9, the omnibus-gitlab package will handle custom certificates.

  1. Place your custom (Root CA) or a self-signed certificate in the /etc/gitlab/trusted-certs/ directory; For example, /etc/gitlab/trusted-certs/customcacert.pem. Note: The certificate must be either DER- or PEM-encoded.
  2. Run gitlab-ctl reconfigure.

This will create a symlink in /opt/gitlab/embedded/ssl/certs/ pointing to your custom certificate. The symlink name is the subject hash. Warning Any broken symlink found in /opt/gitlab/embedded/ssl/certs will be removed and any existing symlink will not be changed. If the directory contains valid certificates, they will be automatically moved to /etc/gitlab/trusted-certs. If the directory contains any other files, reconfigure run will fail with:

ERROR: Not a certificate: /opt/gitlab/embedded/ssl/certs/FILE -> /opt/gitlab/embedded/ssl/certs/FILE

Move the files that are not certificates out of /opt/gitlab/embedded/ssl/certs and run reconfigure once more.

WARNING In GitLab version 8.9.0, 8.9.1 and 8.9.2, the directory that was used to hold the custom certificates was mistakenly set to /etc/gitlab/ssl/trusted-certs/. If you do not have any files inside of this directory, it is safe to remove it. If you do have custom certificates in there, move them to /etc/gitlab/trusted-certs/ and run sudo gitlab-ctl reconfigure.

Let's Encrypt Integration

Omnibus-gitlab can automatically fetch and renew certificates from Let's Encrypt for you. Currently only the primary GitLab domain is supported. Other services like pages, registry, and Mattermost will be supported in a future release.

Enabling

To enable, ensure your external_url specifies https as the protocol, and add the following to your /etc/gitlab/gitlab.rb

letsencrypt['enable'] = true
letsencrypt['contact_emails'] = ['[email protected]'] # Optional

While the contact information is optional, it is recommended. You will receive an email alert when your certificate is nearing its 3 month expiration.

Renewing

There are two commands that can be used to renew your Let's Encrypt certificates.

  1. gitlab-ctl reconfigure
  2. gitlab-ctl renew-le-certs

Both commands require root privileges and will only perform a request to Let's Encrypt if the certificates are close to expiration date. Please consider LE rate limits if you get an error during renewal.

It is recommended to setup a scheduled task to run gitlab-ctl renew-le-certs to ensure your Let's Encrypt certificates stay up to date automatically.

An example cron entry to check daily

0 0 * * * /opt/gitlab/bin/gitlab-ctl renew-le-certs > /dev/null

Troubleshooting

If no symlinks are created in /opt/gitlab/embedded/ssl/certs/ and you see the message "Skipping cert.pem" after running gitlab-ctl reconfigure, that means there may be one of two issues:

  1. The file in /etc/gitlab/ssl/trusted-certs/ is a symlink
  2. The file is not a valid PEM or DER-encoded certificate

To test whether the certificate is in a valid PEM format, you can run openssl to decode the certificate. For example:

/opt/gitlab/embedded/bin/openssl x509 -in /etc/gitlab/trusted-certs/example.pem -text -noout

To test whether the certificate is in a valid DER format:

/opt/gitlab/embedded/bin/openssl x509 -inform DER -in /etc/gitlab/trusted-certs/example.der -text -noout

The output of a valid certificate will look something like the following:

Certificate:
        Data:
            Version: 1 (0x0)
            Serial Number: 3578 (0xdfa)
        Signature Algorithm: sha1WithRSAEncryption
            Issuer: C=JP, ST=Tokyo, L=Chuo-ku, O=Frank4DD, OU=WebCert Support, CN=Frank4DD Web CA/[email protected]
            Validity
                Not Before: Aug 22 05:26:54 2012 GMT
                Not After : Aug 21 05:26:54 2017 GMT
            Subject: C=JP, ST=Tokyo, O=Frank4DD, CN=www.example.com
            Subject Public Key Info:
                Public Key Algorithm: rsaEncryption
                    Public-Key: (512 bit)
                    Modulus:
                        00:9b:fc:66:90:79:84:42:bb:ab:13:fd:2b:7b:f8:
                        de:15:12:e5:f1:93:e3:06:8a:7b:b8:b1:e1:9e:26:
                        bb:95:01:bf:e7:30:ed:64:85:02:dd:15:69:a8:34:
                        b0:06:ec:3f:35:3c:1e:1b:2b:8f:fa:8f:00:1b:df:
                        07:c6:ac:53:07
                    Exponent: 65537 (0x10001)
        Signature Algorithm: sha1WithRSAEncryption
             14:b6:4c:bb:81:79:33:e6:71:a4:da:51:6f:cb:08:1d:8d:60:
             ec:bc:18:c7:73:47:59:b1:f2:20:48:bb:61:fa:fc:4d:ad:89:
             8d:d1:21:eb:d5:d8:e5:ba:d6:a6:36:fd:74:50:83:b6:0f:c7:
             1d:df:7d:e5:2e:81:7f:45:e0:9f:e2:3e:79:ee:d7:30:31:c7:
             20:72:d9:58:2e:2a:fe:12:5a:34:45:a1:19:08:7c:89:47:5f:
             4a:95:be:23:21:4a:53:72:da:2a:05:2f:2e:c9:70:f6:5b:fa:
             fd:df:b4:31:b2:c1:4a:9c:06:25:43:a1:e6:b4:1e:7f:86:9b:
             16:40

An invalid file will display something like:

unable to load certificate
140663131141784:error:0906D06C:PEM routines:PEM_read_bio:no start line:pem_lib.c:701:Expecting: TRUSTED CERTIFICATE

Details on how GitLab and SSL work

GitLab-Omnibus includes its own library of OpenSSL and links all compiled programs (e.g. Ruby, PostgreSQL, etc.) against this library. This library is compiled to look for certificates in /opt/gitlab/embedded/ssl/certs.

GitLab-Omnibus manages custom certificates by symlinking any certificate that gets added to /etc/gitlab/trusted-certs/ to /opt/gitlab/embedded/ssl/certs using the c_rehash tool. For example, let's suppose we add customcacert.pem to /etc/gitlab/trusted-certs/:

$ sudo ls -al /opt/gitlab/embedded/ssl/certs
total 272
drwxr-xr-x 2 root root   4096 Jul 12 04:19 .
drwxr-xr-x 4 root root   4096 Jul  6 04:00 ..
lrwxrwxrwx 1 root root     42 Jul 12 04:19 7f279c95.0 -> /etc/gitlab/trusted-certs/customcacert.pem
-rw-r--r-- 1 root root 263781 Jul  5 17:52 cacert.pem
-rw-r--r-- 1 root root    147 Feb  6 20:48 README

Here we see the fingerprint of the certificate is 7f279c95, which links to the custom certificate.

What happens when we make an HTTPS request? Let's take a simple Ruby program:

#!/opt/gitlab/embedded/bin/ruby
require 'openssl'
require 'net/http'

Net::HTTP.get(URI('https://www.google.com'))

This is what happens behind the scenes:

  1. The "require openssl" line causes the interpreter to load /opt/gitlab/embedded/lib/ruby/2.3.0/x86_64-linux/openssl.so.
  2. The Net::HTTP call then attempts to read the default certificate bundle in /opt/gitlab/embedded/ssl/certs/cacert.pem.
  3. SSL negotiation occurs.
  4. The server sends its SSL certificates.
  5. If the certificates that are sent are covered by the bundle, SSL finishes successfully.
  6. Otherwise, OpenSSL may validate other certificates by searching for files that match their fingerprints inside the predefined certificate directory. For example, if a certificate has the fingerprint 7f279c95, OpenSSL will attempt to read /opt/gitlab/embedded/ssl/certs/7f279c95.0.

Note that the OpenSSL library supports the definition of SSL_CERT_FILE and SSL_CERT_DIR environment variables. The former defines the default certificate bundle to load, while the latter defines a directory in which to search for more certificates. These variables should not be necessary if you have added certificates to the trusted-certs directory. However, if for some reason you need to set them, they can be defined as envirnoment variables. For example:

gitlab_rails['env'] = {"SSL_CERT_FILE" => "/usr/lib/ssl/private/customcacert.pem"}