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Add docs for using builtin auth mechanism #10719

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baccenfutter
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@baccenfutter baccenfutter commented Feb 26, 2025 •
edited by AThousandShips
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Took a huge unnecessary detour, today. it was an upstream battle...

Since there was no mention of it whatsoever, I intuitively concluded that I would have to build my own authentication on top of SceneMultiplayer. The authentication part was easy, but when trying to figure out how to hook into Godot's RPC call-stack to prevent unauthenticated RPC calls, I got stuck and was made aware of SceneMultiplayer.auth_callback by Discord.

Getting the builtin auth mechanism to work with the available docs on SceneMultiplayer was an upstream battle.

But the main issue to me, is the complete lack of mentioning the availability of the builtin auth mechanism, at all.

Wanted to share my results and prevent others from having to take the same detour.

@baccenfutter baccenfutter force-pushed the high-level-multiplayer-authentication branch 2 times, most recently from 04ec47d to bfa5410 Compare February 26, 2025 23:59
@skyace65 skyace65 added enhancement area:manual Issues and PRs related to the Manual/Tutorials section of the documentation topic:network labels Feb 27, 2025
@baccenfutter baccenfutter force-pushed the high-level-multiplayer-authentication branch from bfa5410 to b9c3c6e Compare February 27, 2025 12:33
@skyace65 skyace65 requested a review from a team March 17, 2025 01:25
@skyace65 skyace65 requested a review from mhilbrunner April 16, 2025 21:52
@AThousandShips AThousandShips mentioned this pull request Jun 7, 2025
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SchnozzleCat commented Jun 7, 2025 •
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In addition to discoverability of the authentication mechanism being low, there also appears to be misleading information in the relevant documentation.

The SceneMultiplayer authentication docs (specifically the docs for peer_authenticating and complete_auth) seem to imply that any given peer does not receive the peer_connected signal for another peer until it has authenticated with that specific peer (by both of them calling complete_auth on each other's peer IDs), but that is not what is happening from what I can tell.

I can only see the authentication handshake happen between a client peer and the server, and once the authentication with the server has completed, peer_connected signals are emitted for all others peers on a peer, even though complete_auth was never called for those peers.

I'm not terribly familiar with the godot source code, but that also appears to be what is happening. _admit_peer checks if the server is calling the function, and if so, forwards peer IDs to other peers. Clients receive this message, check that they aren't the server, and that the message came from the server, and then add the peers. The comment in the code also indicates that these peer connection messages are just being relayed over the server (if relaying is enabled), and the clients automatically accept the peers, without authenticating first.

Ideally the previously mentioned documentation can also be updated as part of this PR to make the entire mechanism more clear.

skyace65
skyace65 requested changes Jul 27, 2025
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tutorials/networking/high_level_multiplayer.rst
# signal to the MultiplayerAPI that the authentication was successful
multiplayer.complete_auth(peer_id)

As soon as both, the client's and the the server's :ref:`complete_auth() <class_SceneMultiplayer_method_complete_auth>`, have been called, the connection is considered to be established and the `connected_to_server` and `peer_connected` signals fire.
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As soon as both, the client's and the the server's :ref:`complete_auth() <class_SceneMultiplayer_method_complete_auth>`, have been called, the connection is considered to be established and the `connected_to_server` and `peer_connected` signals fire.
As soon as both, the client's and the server's :ref:`complete_auth() <class_SceneMultiplayer_method_complete_auth>`,
have been called, the connection is considered to be established and the
`connected_to_server` and `peer_connected` signals fire.

Calinou
Calinou reviewed Jul 28, 2025
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tutorials/networking/high_level_multiplayer.rst
Comment on lines +677 to +678
Before hosting your game online to a public audience, you may want to consider adding authentication and protecting your RPCs against unauthenticated access.
For this you can use the :ref:`SceneMultiplayer <class_SceneMultiplayer>`'s builtin authentication mechanism.
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Suggested change
Before hosting your game online to a public audience, you may want to consider adding authentication and protecting your RPCs against unauthenticated access.
For this you can use the :ref:`SceneMultiplayer <class_SceneMultiplayer>`'s builtin authentication mechanism.
Before hosting your game online to a public audience, you may want to consider adding authentication and protecting your RPCs against unauthenticated access.
You can use the :ref:`SceneMultiplayer <class_SceneMultiplayer>`'s builtin authentication mechanism for this.

Calinou
Calinou reviewed Jul 28, 2025
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tutorials/networking/high_level_multiplayer.rst
.. tabs::
.. code-tab:: gdscript GDScript

# after multiplayer.multiplayer_peer = peer
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# after multiplayer.multiplayer_peer = peer
# This goes after `multiplayer.multiplayer_peer = peer`.

Calinou
Calinou reviewed Jul 28, 2025
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tutorials/networking/high_level_multiplayer.rst
multiplayer.auth_timout = 3
multiplayer.auth_callback = func(peer_id: int, payload: PackedByteArray):
var auth_data: Dictionary = JSON.parse_string(payload.get_string_from_utf8())
# your authentication logic goes here...
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Suggested change
# your authentication logic goes here...
# Your authentication logic (such as checking the supplied username/password against a database)
# goes here.

Calinou
Calinou reviewed Jul 28, 2025
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tutorials/networking/high_level_multiplayer.rst
var auth_data: Dictionary = JSON.parse_string(payload.get_string_from_utf8())
# your authentication logic goes here...

# signal to the MultiplayerAPI that the authentication was successful
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@Calinou Calinou Jul 28, 2025 •
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"Signal" may be confused with emitting a signal here.

Suggested change
# signal to the MultiplayerAPI that the authentication was successful
# Tell the MultiplayerAPI that the authentication was successful.

Calinou
Calinou reviewed Jul 28, 2025
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tutorials/networking/high_level_multiplayer.rst
.. tabs::
.. code-tab:: gdscript GDScript

# after multiplayer.multiplayer_peer = peer
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Suggested change
# after multiplayer.multiplayer_peer = peer
# This goes after `multiplayer.multiplayer_peer = peer`.

Calinou
Calinou reviewed Jul 28, 2025
View reviewed changes
tutorials/networking/high_level_multiplayer.rst

# after multiplayer.multiplayer_peer = peer
multiplayer.auth_callback = func:
# we have to set this on the client in order for the peer_authenticating signal to fire
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@Calinou Calinou Jul 28, 2025 •
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Suggested change
# we have to set this on the client in order for the peer_authenticating signal to fire
# We have to set this on the client for the `peer_authenticating`
# signal to emit.

Calinou
Calinou reviewed Jul 28, 2025
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tutorials/networking/high_level_multiplayer.rst
}
multiplayer.send_auth(1, JSON.stringify(auth_data).to_utf8_buffer())

# signal to the MultiplayerAPI that the authentication was successful
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Suggested change
# signal to the MultiplayerAPI that the authentication was successful
# Tell the MultiplayerAPI that the authentication was successful.

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Misleading documentation for SceneMultiplayer authentication
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@baccenfutter @SchnozzleCat @Calinou @skyace65