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89 lines
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89 lines
4.0 KiB
Plaintext
---
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title: Server ACL
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description: |-
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An event to indicate which servers are permitted to participate in the
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room. Server ACLs may allow or deny groups of hosts. All servers participating
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in the room, including those that are denied, are expected to uphold the
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server ACL. Servers that do not uphold the ACLs MUST be added to the denied hosts
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list in order for the ACLs to remain effective.
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The ``allow`` and ``deny`` lists are lists of globs supporting ``?`` and ``*``
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as wildcards. When comparing against the server ACLs, the suspect server's port
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number must not be considered. Therefore ``evil.com``, ``evil.com:8448``, and
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``evil.com:1234`` would all match rules that apply to ``evil.com``, for example.
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The ACLs are applied to servers when they make requests, and are applied in
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the following order:
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1. If there is no ``m.room.server_acl`` event in the room state, allow.
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#. If the server name is an IP address (v4 or v6) literal, and ``allow_ip_literals``
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is present and ``false``, deny.
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#. If the server name matches an entry in the ``deny`` list, deny.
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#. If the server name matches an entry in the ``allow`` list, allow.
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#. Otherwise, deny.
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.. Note::
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Server ACLs do not restrict the events relative to the room DAG via authorisation
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rules, but instead act purely at the network layer to determine which servers are
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allowed to connect and interact with a given room.
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.. WARNING::
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Failing to provide an ``allow`` rule of some kind will prevent **all**
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servers from participating in the room, including the sender. This renders
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the room unusable. A common allow rule is ``[ "*" ]`` which would still
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permit the use of the ``deny`` list without losing the room.
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.. WARNING::
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All compliant servers must implement server ACLs. However, legacy or noncompliant
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servers exist which do not uphold ACLs, and these MUST be manually appended to
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the denied hosts list when setting an ACL to prevent them from leaking events from
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banned servers into a room. Currently, the only way to determine noncompliant hosts is
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to check the ``prev_events`` of leaked events, therefore detecting servers which
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are not upholding the ACLs. Server versions can also be used to try to detect hosts that
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will not uphold the ACLs, although this is not comprehensive. Server ACLs were added
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in Synapse v0.32.0, although other server implementations and versions exist in the world.
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allOf:
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- $ref: core-event-schema/state_event.yaml
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type: object
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properties:
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content:
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properties:
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allow_ip_literals:
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type: boolean
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description: |-
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True to allow server names that are IP address literals. False to
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deny. Defaults to true if missing or otherwise not a boolean.
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This is strongly recommended to be set to ``false`` as servers running
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with IP literal names are strongly discouraged in order to require
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legitimate homeservers to be backed by a valid registered domain name.
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allow:
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type: array
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description: |-
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The server names to allow in the room, excluding any port information.
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Wildcards may be used to cover a wider range of hosts, where ``*``
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matches zero or more characters and ``?`` matches exactly one character.
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**This defaults to an empty list when not provided, effectively disallowing
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every server.**
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items:
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type: string
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deny:
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type: array
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description: |-
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The server names to disallow in the room, excluding any port information.
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Wildcards may be used to cover a wider range of hosts, where ``*``
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matches zero or more characters and ``?`` matches exactly one character.
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This defaults to an empty list when not provided.
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items:
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type: string
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type: object
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state_key:
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description: A zero-length string.
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pattern: '^$'
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type: string
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type:
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enum: ['m.room.server_acl']
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type: enum
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