debian-mirror-gitlab/doc/security/webhooks.md

stage	group	info	type
Manage	Authentication and Authorization	To determine the technical writer assigned to the Stage/Group associated with this page, see https://about.gitlab.com/handbook/product/ux/technical-writing/#assignments	concepts, reference, howto

Filtering outbound requests (FREE SELF)

To protect against the risk of data loss and exposure, GitLab administrators can now use outbound request filtering controls to restrict certain outbound requests made by the GitLab instance.

Secure webhooks and integrations

Users with at least the Maintainer role can set up webhooks that are triggered when specific changes occur in a project or group. When triggered, a POST HTTP request is sent to a URL. A webhook is usually configured to send data to a specific external web service, which processes the data in an appropriate way.

However, a webhook can be configured with a URL for an internal web service instead of an external web service. When the webhook is triggered, non-GitLab web services running on your GitLab server or in its local network could be exploited.

Webhook requests are made by the GitLab server itself and use a single optional secret token per hook for authorization instead of:

• A user token.
• A repository-specific token.

As a result, these requests can have broader access than intended, including access to everything running on the server that hosts the webhook including:

• The GitLab server.
• The API itself.
• For some webhooks, network access to other servers in that webhook server's local network, even if these services are otherwise protected and inaccessible from the outside world.

Webhooks can be used to trigger destructive commands using web services that don't require authentication. These webhooks can get the GitLab server to make POST HTTP requests to endpoints that delete resources.

Allow requests to the local network from webhooks and integrations

Prerequisite:

• You must have administrator access to the instance.

To prevent exploitation of insecure internal web services, all webhook and integration requests to the following local network addresses are not allowed:

• The current GitLab instance server address.
• Private network addresses, including 127.0.0.1, ::1, 0.0.0.0, 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16, and IPv6 site-local (ffc0::/10) addresses.

To allow access to these addresses:

1. On the top bar, select Main menu > Admin.
2. On the left sidebar, select Settings > Network.
3. Expand Outbound requests.
4. Select the Allow requests to the local network from webhooks and integrations checkbox.

Prevent requests to the local network from system hooks

Prerequisite:

• You must have administrator access to the instance.

System hooks can make requests to the local network by default. To prevent system hook requests to the local network:

1. On the top bar, select Main menu > Admin.
2. On the left sidebar, select Settings > Network.
3. Expand Outbound requests.
4. Clear the Allow requests to the local network from system hooks checkbox.

Filter requests

Introduced in GitLab 15.10 with a flag named deny_all_requests_except_allowed. Disabled by default.

FLAG: On self-managed GitLab, by default this feature is not available. To make it available, ask an administrator to enable the feature flag named deny_all_requests_except_allowed. On GitLab.com, this feature is not available.

Prerequisite:

• You must have administrator access to the instance.

To filter requests by blocking many requests:

1. On the top bar, select Main menu > Admin.
2. On the left sidebar, select Settings > Network.
3. Expand Outbound requests.
4. Select the Block all requests, except for IP addresses, IP ranges, and domain names defined in the allowlist checkbox.

When this checkbox is selected, requests to the following are still not blocked:

• Core services like Geo, Git, GitLab Shell, Gitaly, PostgreSQL, and Redis.
• Object storage.
• IP addresses and domains in the allowlist.

This setting is respected by the main GitLab application only, so other services like Gitaly can still make requests that break the rule. Additionally, some areas of GitLab do not respect outbound filtering rules.

Allow outbound requests to certain IP addresses and domains

Introduced in GitLab 12.2.

Prerequisite:

• You must have administrator access to the instance.

To allow outbound requests to certain IP addresses and domains:

1. On the top bar, select Main menu > Admin.
2. On the left sidebar, select Settings > Network.
3. Expand Outbound requests.
4. In Local IP addresses and domain names that hooks and integrations can access, enter your IP addresses and domains.

The entries can:

• Be separated by semicolons, commas, or whitespaces (including newlines).
• Be in different formats like hostnames, IP addresses, IP address ranges. IPv6 is supported. Hostnames that contain Unicode characters should use Internationalized Domain Names in Applications (IDNA) encoding.
• Include ports. For example, 127.0.0.1:8080 only allows connections to port 8080 on 127.0.0.1. If no port is specified, all ports on that IP address or domain are allowed. An IP address range allows all ports on all IP addresses in that range.
• Number no more than 1000 entries of no more than 255 characters for each entry.
• Not contain wildcards (for example, *.example.com).

For example:

example.com;gitlab.example.com
127.0.0.1,1:0:0:0:0:0:0:1
127.0.0.0/8 1:0:0:0:0:0:0:0/124
[1:0:0:0:0:0:0:1]:8080
127.0.0.1:8080
example.com:8080

Troubleshooting

When filtering outbound requests, you might encounter the following issues.

Configured URLs are blocked

You can only select the Block all requests, except for IP addresses, IP ranges, and domain names defined in the allowlist checkbox if no configured URLs would be blocked. Otherwise, you might get an error message that says the URL is blocked.

If you can't enable this setting, do one of the following:

• Disable the URL setting.
• Configure another URL, or leave the URL setting empty.
• Add the configured URL to the allowlist.

Public runner releases URL is blocked

Most GitLab instances have their public_runner_releases_url set to https://gitlab.com/api/v4/projects/gitlab-org%2Fgitlab-runner/releases. You can't change or disable this setting in the Admin Area, which can prevent you from filtering requests.

To enable the setting, use the Rails console to set public_runner_releases_url to the instance host:

current_settings = ApplicationSetting.find_or_create_without_cache;
ApplicationSettings::UpdateService.new(current_settings, nil, public_runner_releases_url: Gitlab.config.gitlab.base_url).execute

GitLab subscription management is blocked

When you filter requests, GitLab subscription management is blocked.

To work around this problem, add customers.gitlab.com:443 to the allowlist.