Document importance of public_baseurl for delegation and OIDC (#19270)

I just stumbled across the fact that my config used delegation as
recommended by the docs, and hosted Synapse on a subdomain. However my
config never had `public_baseurl` set and worked without issues, until I
just now tried to setup OIDC.

OIDC is initialized by the client instructing to open a URL on the
homeserver, and initially the correct URL is called, but Synapse does
not recognize it without `public_baseurl` being set correctly. After
changing this it immediately started working.

So in order to prevent anybody from making the same mistake, this adds a
small clarifying block in the OIDC docs.
This commit is contained in:
Andre Klärner
2025-12-13 01:07:39 +01:00
committed by GitHub
parent df24e0f302
commit 466994743a
2 changed files with 6 additions and 0 deletions

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Document the importance of `public_baseurl` when configuring OpenID Connect authentication.

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@@ -50,6 +50,11 @@ setting in your configuration file.
See the [configuration manual](usage/configuration/config_documentation.md#oidc_providers) for some sample settings, as well as See the [configuration manual](usage/configuration/config_documentation.md#oidc_providers) for some sample settings, as well as
the text below for example configurations for specific providers. the text below for example configurations for specific providers.
For setups using [`.well-known` delegation](delegate.md), make sure
[`public_baseurl`](usage/configuration/config_documentation.md#public_baseurl) is set
appropriately. If unset, Synapse defaults to `https://<server_name>/` which is used in
the OIDC callback URL.
## OIDC Back-Channel Logout ## OIDC Back-Channel Logout
Synapse supports receiving [OpenID Connect Back-Channel Logout](https://openid.net/specs/openid-connect-backchannel-1_0.html) notifications. Synapse supports receiving [OpenID Connect Back-Channel Logout](https://openid.net/specs/openid-connect-backchannel-1_0.html) notifications.