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revert: "fix: skip provider button auth only redirect (#3309)" (#3314)

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This reverts commit 9c61c49ec2.

The original fix broke nginx deployments using `auth_request`. When `/oauth2/auth` returns 302,
nginx's `auth_request` module treats this as an internal error:

    [error] auth request unexpected status: 302 while sending to client

nginx then returns **500 Internal Server Error** to the browser.

> If the subrequest returns a 2xx response code, the access is allowed. If it returns 401 or 403,
> the access is denied with the corresponding error code. Any other response code returned by the
> subrequest is considered an error.
https://nginx.org/en/docs/http/ngx_http_auth_request_module.html

The nginx `auth_request` module has strict semantics (non-negotiable):

| Subrequest status | nginx behavior |
|---|---|
| 2xx | Allow request |
| 401 / 403 | Deny → trigger `error_page` |
| **Any other status** | **Internal error → 500** |

The `/oauth2/auth` endpoint is used as a **policy oracle** (yes/no decision),
not as a browser-facing endpoint. It cannot return redirects.

Any nginx deployment with:
- `skip-provider-button=true`
- Using `auth_request` directive

Will receive 500 errors instead of the expected authentication flow.

The correct fix for #334 is a **documentation update**, not a code change:

```nginx
error_page 401 = @oauth2_signin;

location @oauth2_signin {
    return 302 /oauth2/sign_in?rd=$scheme://$host$request_uri;
}
```

This keeps `/oauth2/auth` as a pure 401/2xx oracle and lets nginx perform the proper 302 redirect to the browser.

- Original Issue: #334
- Regression introduced in PR: #3309

Signed-off-by: Stefan Markmann <stefan@markmann.net>
Signed-off-by: Jan Larwig <jan@larwig.com>
Co-authored-by: Jan Larwig <jan@larwig.com>
This commit is contained in:
Stefan Markmann
2026-01-18 00:36:08 +01:00
committed by GitHub
co-authored by Jan Larwig
parent 7bf586c898
commit cf5d34acf6
5 changed files with 7 additions and 54 deletions
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docs/docs/configuration/overview.md
+1 -1
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@@ -214,7 +214,7 @@ Provider specific options can be found on their respective subpages.
| flag: `--skip-auth-regex`<br/>toml: `skip_auth_regex` | string \| list | (DEPRECATED for `--skip-auth-route`) bypass authentication for requests paths that match (may be given multiple times) | |
| flag: `--skip-auth-route`<br/>toml: `skip_auth_routes` | string \| list | bypass authentication for requests that match the method & path. Format: method=path_regex OR method!=path_regex. For all methods: path_regex OR !=path_regex | |
| flag: `--skip-jwt-bearer-tokens`<br/>toml: `skip_jwt_bearer_tokens` | bool | will skip requests that have verified JWT bearer tokens (the token must have [`aud`](https://en.wikipedia.org/wiki/JSON_Web_Token#Standard_fields) that matches this client id or one of the extras from `extra-jwt-issuers`) | false |
| flag: `--skip-provider-button`<br/>toml: `skip_provider_button` | bool | will skip sign-in-page to directly reach the next step: oauth/start. When enabled, the `/oauth2/auth` endpoint returns 302 redirects instead of 401, ensuring compatibility with nginx `auth_request` and similar reverse proxy authentication architectures. | false |
| flag: `--skip-provider-button`<br/>toml: `skip_provider_button` | bool | will skip sign-in-page to directly reach the next step: oauth/start | false |
| flag: `--ssl-insecure-skip-verify`<br/>toml: `ssl_insecure_skip_verify` | bool | skip validation of certificates presented when using HTTPS providers | false |
| flag: `--trusted-ip`<br/>toml: `trusted_ips` | string \| list | list of IPs or CIDR ranges to allow to bypass authentication (may be given multiple times). When combined with `--reverse-proxy` and optionally `--real-client-ip-header` this will evaluate the trust of the IP stored in an HTTP header by a reverse proxy rather than the layer-3/4 remote address. WARNING: trusting IPs has inherent security flaws, especially when obtaining the IP address from an HTTP header (reverse-proxy mode). Use this option only if you understand the risks and how to manage them. | |
| flag: `--whitelist-domain`<br/>toml: `whitelist_domains` | string \| list | allowed domains for redirection after authentication. Prefix domain with a `.` or a `*.` to allow subdomains (e.g. `.example.com`, `*.example.com`)&nbsp;[^2] | |
docs/versioned_docs/version-7.14.x/configuration/overview.md
+1 -1
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@@ -214,7 +214,7 @@ Provider specific options can be found on their respective subpages.
| flag: `--skip-auth-regex`<br/>toml: `skip_auth_regex` | string \| list | (DEPRECATED for `--skip-auth-route`) bypass authentication for requests paths that match (may be given multiple times) | |
| flag: `--skip-auth-route`<br/>toml: `skip_auth_routes` | string \| list | bypass authentication for requests that match the method & path. Format: method=path_regex OR method!=path_regex. For all methods: path_regex OR !=path_regex | |
| flag: `--skip-jwt-bearer-tokens`<br/>toml: `skip_jwt_bearer_tokens` | bool | will skip requests that have verified JWT bearer tokens (the token must have [`aud`](https://en.wikipedia.org/wiki/JSON_Web_Token#Standard_fields) that matches this client id or one of the extras from `extra-jwt-issuers`) | false |
| flag: `--skip-provider-button`<br/>toml: `skip_provider_button` | bool | will skip sign-in-page to directly reach the next step: oauth/start. When enabled, the `/oauth2/auth` endpoint returns 302 redirects instead of 401, ensuring compatibility with nginx `auth_request` and similar reverse proxy authentication architectures. | false |
| flag: `--skip-provider-button`<br/>toml: `skip_provider_button` | bool | will skip sign-in-page to directly reach the next step: oauth/start | false |
| flag: `--ssl-insecure-skip-verify`<br/>toml: `ssl_insecure_skip_verify` | bool | skip validation of certificates presented when using HTTPS providers | false |
| flag: `--trusted-ip`<br/>toml: `trusted_ips` | string \| list | list of IPs or CIDR ranges to allow to bypass authentication (may be given multiple times). When combined with `--reverse-proxy` and optionally `--real-client-ip-header` this will evaluate the trust of the IP stored in an HTTP header by a reverse proxy rather than the layer-3/4 remote address. WARNING: trusting IPs has inherent security flaws, especially when obtaining the IP address from an HTTP header (reverse-proxy mode). Use this option only if you understand the risks and how to manage them. | |
| flag: `--whitelist-domain`<br/>toml: `whitelist_domains` | string \| list | allowed domains for redirection after authentication. Prefix domain with a `.` or a `*.` to allow subdomains (e.g. `.example.com`, `*.example.com`)&nbsp;[^2] | |