Gerrit SAML Authentication Filter

This filter allows you to authenticate to Gerrit using a SAML identity provider.

Installation

Gerrit looks for 3 attributes (which are configurable) in the AttributeStatement:

• DisplayName: the full name of the user.
• EmailAddress: email address of the user.
• UserName: username (used for ssh).

If any of these attributes is not found in the assertion, their value is taken from the NameId field of the SAML assertion.

Setting Gerrit in your IdP

• Okta
• Keycloak
• ADFS
• SimpleSamlPHP

Download the plugin

Download Gerrit SAML plugin for the appropriate version of gerrit from the Gerrit-CI into $gerrit_site/lib/.

Building the SAML filter

This authentication filter is built with Bazel.

Build in Gerrit tree

Clone or link this filter to the plugins directory of Gerrit's source tree. Put the external dependency Bazel build file into the Gerrit /plugins directory, replacing the existing empty one.

  cd gerrit/plugins
  rm external_plugin_deps.bzl
  ln -s @PLUGIN@/external_plugin_deps.bzl .

Then issue

  bazel build plugins/@PLUGIN@

The output is created in

  bazel-bin/plugins/@PLUGIN@/@[email protected]

The @[email protected] should be deployed to gerrit_site/lib directory:

 cp bazel-bin/plugins/@PLUGIN@/@[email protected] `$gerrit_site/lib`

NOTE: Even though the project is built as a Gerrit plugin, it must be loaded as a Servlet filter by Gerrit and thus needs to be located with the libraries and cannot be dynamically loaded like other plugins.

This project can be imported into the Eclipse IDE. Add the plugin name to the CUSTOM_PLUGINS set in Gerrit core in tools/bzl/plugins.bzl, and execute:

  ./tools/eclipse/project.py

How to build the Gerrit Plugin API is described in the Gerrit documentation.

Configure Gerrit to use the SAML filter:

In $site_path/etc/gerrit.config file, the [httpd] and [gerrit] sections should contain:

[gerrit]
    installModule = com.googlesource.gerrit.plugins.saml.Module
[httpd]
    filterClass = com.googlesource.gerrit.plugins.saml.SamlWebFilter

Configure HTTP authentication for Gerrit:

Please make sure you are using Gerrit 2.11.5 or later.

In $site_path/etc/gerrit.config file, the [auth] section should include the following lines:

[auth]
	type = HTTP
    logoutUrl = https://mysso.example.com/logout
    httpHeader = X-SAML-UserName
    httpEmailHeader = X-SAML-EmailHeader
    httpExternalIdHeader = X-SAML-ExternalId

The header names are used internally between the SAML plugin and Gerrit to communicate the user's identity. You can use other names (as long as it will not conflict with any other HTTP header Gerrit might expect).

Create a local keystore

In $gerrit_site/etc create a local keystore:

keytool -genkeypair -alias pac4j -keypass pac4j-demo-password \
  -keystore samlKeystore.jks \
  -storepass pac4j-demo-password -keyalg RSA -keysize 2048 -validity 3650

Configure SAML

Add a new [saml] section to $site_path/etc/gerrit.config:

[saml]
    keystorePath = /path/to/samlKeystore.jks
    keystorePassword = pac4j-demo-password
    privateKeyPassword = pac4j-demo-password
    metadataPath = https://mycompany.okta.com/app/hashash/sso/saml/metadata

saml.metadataPath: Location of IdP Metadata from your SAML identity provider. The value can be a URL, or a local file (prefix with file://)

saml.keystorePath: Path to the keystore created above. If not absolute, the path is resolved relative to $site_path.

saml.privateKeyPassword: Password protecting the private key of the generated key pair (needs to be the same as the password provided throguh the keypass flag above.)

saml.keystorePassword: Password that is used to protect the integrity of the keystore (needs to be the same as the password provided throguh the keystore flag above.)

saml.maxAuthLifetime: (Optional) Max Authentication Lifetime (secs) configuration.

Default is 86400

saml.forceAuth: (Optional) Whether to force authentication with the IdP, when the session in Gerrit expires.

Default is false

saml.displayNameAttr: Gerrit will look for an attribute with this name in the assertion to find a display name for the user. If the attribute is not found, the NameId from the SAML assertion is used instead.

Default is DisplayName

saml.computedDisplayName: Set to compute display name attribute from first and last names.

Default is false.

saml.firstNameAttr: Gerrit will look for an attribute with this name in the assertion to find the first name of the user. Only used, when computedDisplayName is set to true. If the attribute is not found, the NameId from the SAML assertion is used instead.

Default is FirstName

saml.lastNameAttr: Gerrit will look for an attribute with this name in the assertion to find the last name of the user. Only used, when computedDisplayName is set to true. If the attribute is not found, the NameId from the SAML assertion is used instead.

Default is LastName

saml.emailAddressAttr: Gerrit will look for an attribute with this name in the assertion to find a the email address of the user. If the attribute is not found, the NameId from the SAML assertion is used instead.

Default is EmailAddress

saml.userNameAttr: Gerrit will look for an attribute with this name in the assertion to find a the email address of the user. If the attribute is not found, the NameId from the SAML assertion is used instead.

Default is UserName

saml.serviceProviderEntityId: SAML service provider entity id.

Default is not set.

saml.identityProviderEntityId: SAML identity provider entity id. When present a IDPSSODescriptor is expected in the SAML metadata document. When absent a saml service provider with its SPSSODescriptor is assumed. This value takes precedence over the value in saml.serviceProviderEntityId.

Default is not set.

saml.memberOfAttr: Gerrit will look for an attribute with this name in the assertion to find the groups the user is member of.

The user will receive these groups prefixed with saml/ in gerrit. When the groups do not exist, they will be created. When a user its membership is removed this group will also be removed from this user on his next login.

As group membership is only updated when a user logs in on the UI, so when a user loses membership to a group in SAML, he will still be able to execute his rights as if he is part of that group as long as he does not log in to the UI. So enabling this feature can be seen as a security risk in certain environments.

When this attribute is not set or empty, SAML membership synchronization is disabled.

Default is not set.

saml.useNameQualifier: By SAML specification, the authentication request must not contain a NameQualifier, if the SP entity is in the format nameid-format:entity. However, some IdP require that information to be present. You can force a NameQualifier in the request with the useNameQualifier parameter. For ADFS 3.0 support, set this to false.

Default is true.

Create SAML metadata offline

The SAML metadata file ($SITE/data/saml/sp-metadata.xml) will be created on the first login attempt, when the plugin has been installed. However, at that point authentication would fail until the identity provider was configured using the metadata file of Gerrit.

To avoid this period in which authentication is not possible, the metadata can be created offline. To do so, a separate java binary has to be built:

bazelisk build //plugins/saml:SamlMetadataCreator_deploy.jar

The resulting jar-file can then be used to create the metadata file based on the existing gerrit.config:

bazel-bin/plugins/saml/SamlMetaDataCreator \
  -d $SITE \    # Path to the Gerrit site
  --overwrite   # Whether to overwrite any existing metadata file

The resulting metadata will be printed to standard out and stored at $SITE/data/saml/sp-metadata.xml.