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- A [complete GitLab with SAML testing environment using Docker compose](https://gitlab.com/gitlab-com/support/toolbox/replication/tree/master/compose_files).
- A [quick start guide to start a Docker container](../../../administration/troubleshooting/test_environments.md#saml)
with a plug and play SAML 2.0 identity provider if you only require a SAML provider.
For convenience, we've included some [example resources](../../../user/group/saml_sso/example_saml_config.md) used by our Support Team. While they may help you verify the SAML app configuration, they are not guaranteed to reflect the current state of third-party products.
## Searching Rails log for a SAML response **(FREE SELF)**
You can find the base64-encoded SAML Response in the [`production_json.log`](../../../administration/logs/index.md#production_jsonlog).
This response is sent from the identity provider, and contains user information that is consumed by GitLab.
Many errors in the SAML integration can be solved by decoding this response and comparing it to the SAML settings in the GitLab configuration file.
For example, with SAML for groups,
you should be able to find the base64 encoded SAML response by searching with the following filters:
[map the attribute names in your SAML Response to the corresponding OmniAuth `info` hash names](../../../integration/saml.md#map-saml-response-attribute-names).
### Message: "SAML authentication failed: Extern UID has already been taken"
This error suggests you are signed in as a GitLab user but have already linked your SAML identity to a different GitLab user. Sign out and then try to sign in again using SAML, which should log you into GitLab with the linked user account.
If you do not wish to use that GitLab user with the SAML login, you can [unlink the GitLab account from the SAML app](index.md#unlinking-accounts).
### Message: "SAML authentication failed: User has already been taken"
| You've tried to link multiple SAML identities to the same user, for a given identity provider. | Change the identity that you sign in with. To do so, [unlink the previous SAML identity](index.md#unlinking-accounts) from this GitLab account before attempting to sign in again. |
| The `NameID` changes every time the user requests SSO identification | [Check the `NameID`](#verify-nameid) is not set with `Transient` format, or the `NameID` is not changing on subsequent requests.|
| When a user account with the email address already exists in GitLab, but the user does not have the SAML identity tied to their account. | The user needs to [link their account](index.md#user-access-and-management). |
User accounts are created in one of the following ways:
- User registration
- Sign in through OAuth
- Sign in through SAML
- SCIM provisioning
### Message: "SAML authentication failed: Extern UID has already been taken, User has already been taken"
Getting both of these errors at the same time suggests the `NameID` capitalization provided by the identity provider didn't exactly match the previous value for that user.
This can be prevented by configuring the `NameID` to return a consistent value. Fixing this for an individual user involves changing the identifier for the user. For GitLab.com, the user needs to [unlink their SAML from the GitLab account](index.md#unlinking-accounts).
### Message: "Request to link SAML account must be authorized"
Ensure that the user who is trying to link their GitLab account has been added as a user within the identity provider's SAML app.
Alternatively, the SAML response may be missing the `InResponseTo` attribute in the
`samlp:Response` tag, which is [expected by the SAML gem](https://github.com/onelogin/ruby-saml/blob/9f710c5028b069bfab4b9e2b66891e0549765af5/lib/onelogin/ruby-saml/response.rb#L307-L316).
The identity provider administrator should ensure that the login is
initiated by the service provider and not only the identity provider.
### Message: "Sign in to GitLab to connect your organization's account" **(PREMIUM SAAS)**
A user can see this message when they are trying to [manually link SAML to their existing GitLab.com account](index.md#linking-saml-to-your-existing-gitlabcom-account).
In troubleshooting, any authenticated user can use the API to verify the `NameID` GitLab already has linked to their user by visiting [`https://gitlab.com/api/v4/user`](https://gitlab.com/api/v4/user) and checking the `extern_uid` under identities.
For self-managed, administrators can use the [users API](../../../api/users.md) to see the same information.
When using SAML for groups, group members of a role with the appropriate permissions can make use of the [members API](../../../api/members.md) to view group SAML identity information for members of the group.
This can then be compared to the `NameID` being sent by the identity provider by decoding the message with a [SAML debugging tool](#saml-debugging-tools). We require that these match to identify users.
Ensure that the **GitLab single sign-on URL** (for GitLab.com) or the instance URL (for self-managed) has been configured as "Login URL" (or similarly named field) in the identity provider's SAML app.
For GitLab.com, alternatively, when users need to [link SAML to their existing GitLab.com account](index.md#linking-saml-to-your-existing-gitlabcom-account), provide the **GitLab single sign-on URL** and instruct users not to use the SAML app on first sign in.
### Users receive a 404 **(PREMIUM SAAS)**
Because SAML SSO for groups is a paid feature, your subscription expiring can result in a `404` error when you're signing in using SAML SSO on GitLab.com.
[there is an active subscription](../../../subscriptions/gitlab_com/index.md#view-your-gitlab-saas-subscription) being used in this SAML SSO namespace.
If you receive a `404` during setup when using "verify configuration", make sure you have used the correct
If a user is trying to sign in for the first time and the GitLab single sign-on URL has not [been configured](index.md#configure-your-identity-provider), they may see a 404.
As outlined in the [user access section](index.md#linking-saml-to-your-existing-gitlabcom-account), a group Owner needs to provide the URL to users.
### 500 error after login **(FREE SELF)**
If you see a "500 error" in GitLab when you are redirected back from the SAML
sign-in page, this could indicate that:
- GitLab couldn't get the email address for the SAML user. Ensure the identity provider provides a claim containing the user's
email address using the claim name `email` or `mail`.
- The certificate set your `gitlab.rb` file for `identity provider_cert_fingerprint` or `identity provider_cert` file is incorrect.
- Your `gitlab.rb` file is set to enable `identity provider_cert_fingerprint`, and `identity provider_cert` is being provided, or the reverse.
### 422 error after login **(FREE SELF)**
If you see a "422 error" in GitLab when you are redirected from the SAML
sign-in page, you might have an incorrectly configured Assertion Consumer
Service (ACS) URL on the identity provider.
Make sure the ACS URL points to `https://gitlab.example.com/users/auth/saml/callback`, where
`gitlab.example.com` is the URL of your GitLab instance.
If the ACS URL is correct, and you still have errors, review the other
Troubleshooting sections.
### User is blocked when signing in through SAML **(FREE SELF)**
The following are the most likely reasons that a user is blocked when signing in through SAML:
- In the configuration, `gitlab_rails['omniauth_block_auto_created_users'] = true` is set and this is the user's first time signing in.
- [`required_groups`](../../../integration/saml.md#required-groups) are configured but the user is not a member of one.
## Google workspace troubleshooting tips
The Google Workspace documentation on [SAML app error messages](https://support.google.com/a/answer/6301076?hl=en) is helpful for debugging if you are seeing an error from Google while signing in.
Pay particular attention to the following 403 errors:
