synapse allows sending of unecrypted messages to encrypted rooms

[telmich]

Description

When posting a message wtih m.room.message type to synapse to a room that is encrypted, synapse accepts the message and stores it.

Steps to reproduce

Post an unencrypted message to an encrypted room.

Homeserver

any

Synapse Version

1.115.0

Installation Method

Docker (matrixdotorg/synapse)

Database

postgresql

Workers

Single process

Platform

Kubernetes

Configuration

Relevant log output

-

Anything else that would be useful to know?

Expected behaviour is after m.room.encryption unencrypted messages are rejected.

[telmich]

Element-web does show the unencrypted message with a warning sign, but conceptually I think synapse should not accept it after m.room.encryption has been sent to the room.