mirror of https://github.com/vacp2p/rfc.git
784 lines
30 KiB
Markdown
784 lines
30 KiB
Markdown
---
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slug: 59
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title: 59/PUSH-NOTIFICATION-SERVER
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name: Push notification server RFC Template
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status: raw
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editor: Andrea Maria Piana <andreap@status.im>
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contributors:
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---
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# 16/PUSH-NOTIFICATION-SERVER
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- [Push Notification Server](#16push-notification-server)
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- [Reason](#reason)
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- [Requirements](#requirements)
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- [Components](#components)
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- [Registering with the push notification service](#registering-with-the-push-notification-service)
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- [Re-registering with the push notification service](#re-registering-with-the-push-notification-server)
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- [Changing options](#changing-options)
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- [Unregistering from push notifications](#unregistering-from-push-notifications)
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- [Advertising a push notification server](#advertising-a-push-notification-server)
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- [Discovering a push notification server](#discovering-a-push-notification-server)
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- [Querying the push notification service](#querying-the-push-notification-server)
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- [Sending a push notification](#sending-a-push-notification)
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- [Flow](#flow)
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- [Registration process](#registration-process)
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- [Sending a notification](#sending-a-notification)
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- [Receiving a push notification](#receiving-a-push-notification)
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- [Protobuf description](#protobuf-description)
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- [PushNotificationRegistration](#pushnotificationregistration)
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- [PushNotificationRegistrationResponse](#pushnotificationregistrationresponse)
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- [ContactCodeAdvertisement](#contactcodeadvertisement)
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- [PushNotificationQuery](#pushnotificationquery)
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- [PushNotificationQueryInfo](#pushnotificationqueryinfo)
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- [PushNotificationQueryResponse](#pushnotificationqueryresponse)
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- [PushNotification](#pushnotification)
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- [PushNotificationRequest](#pushnotificationrequest)
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- [PushNotificationResponse](#pushnotificationacknowledgement)
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- [PushNotificationReport](#pushnotificationreport)
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- [Anonymous mode of operations](#anonymous-mode-of-operations)
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- [Security considerations](#security-considerations)
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- [FAQ](#faq)
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- [Changelog](#changelog)
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- [Version 0.1](#version-01)
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- [Copyright](#copyright)
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## Reason
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Push notifications for iOS devices and some Android devices can only be
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implemented by relying on [APN service](https://developer.apple.com/library/archive/documentation/NetworkingInternet/Conceptual/RemoteNotificationsPG/APNSOverview.html#//apple_ref/doc/uid/TP40008194-CH8-SW1) for iOS or [Firebase](https://firebase.google.com/).
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This is useful for Android devices that do not support foreground services or that often kill the
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foreground service.
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iOS only allows certain kind of applications to keep a connection open when in the
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background, VoIP for example, which current status client does not qualify for.
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Applications on iOS can also request execution time when they are in the [background](https://developer.apple.com/documentation/uikit/app_and_environment/scenes/preparing_your_ui_to_run_in_the_background/updating_your_app_with_background_app_refresh)
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but it has a limited set of use cases, for example it won't schedule any time
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if the application was force quit, and generally is not responsive enough to implement
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a push notification system.
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Therefore Status provides a set of Push notification services that can be used
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to achieve this functionality.
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Because this can't be safely implemented in a privacy preserving manner, clients
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MUST be given an option to opt-in to receiving and sending push notifications. They are disabled by default.
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## Requirements
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The party releasing the app MUST possess a certificate for the Apple Push Notification service and its has to run a [gorush](https://github.com/appleboy/gorush) publicly accessible server for sending the actual notification.
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The party releasing the app, Status in this case, needs to run its own [gorush](https://github.com/appleboy/gorush)
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## Components
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### Gorush instance
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A [gorush](https://github.com/appleboy/gorush) instance MUST be publicly
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available, this will be used only by push notification servers.
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### Push notification server
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A push notification server used by clients to register for receiving and sending push notifications.
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### Registering client
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A Status client that wants to receive push notifications
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### Sending client
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A Status client that wants to send push notifications
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## Registering with the push notification service
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A client MAY register with one or more Push Notification services of their choice.
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A `PNR message` (Push Notification Registration) MUST be sent to the [partitioned topic](../stable/10-waku-usage.md#partitioned-topic) for the
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public key of the node, encrypted with this key.
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The message MUST be wrapped in a [`ApplicationMetadataMessage`](../stable/6-payloads.6#payload-wrapper) with type set to `PUSH_NOTIFICATION_REGISTRATION`.
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The marshaled protobuf payload MUST also be encrypted with AES-GCM using the Diffie–Hellman key
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generated from the client and server identity.
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This is done in order to ensure that the extracted key from the signature will be
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considered invalid if it can't decrypt the payload.
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The content of the message MUST contain the following [protobuf record](https://developers.google.com/protocol-buffers/):
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```protobuf
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message PushNotificationRegistration {
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enum TokenType {
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UNKNOWN_TOKEN_TYPE = 0;
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APN_TOKEN = 1;
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FIREBASE_TOKEN = 2;
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}
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TokenType token_type = 1;
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string device_token = 2;
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string installation_id = 3;
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string access_token = 4;
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bool enabled = 5;
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uint64 version = 6;
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repeated bytes allowed_key_list = 7;
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repeated bytes blocked_chat_list = 8;
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bool unregister = 9;
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bytes grant = 10;
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bool allow_from_contacts_only = 11;
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string apn_topic = 12;
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bool block_mentions = 13;
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repeated bytes allowed_mentions_chat_list = 14;
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}
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```
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A push notification server will handle the message according to the following rules:
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- it MUST extract the public key of the sender from the signature and verify that
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the payload can be decrypted successfully.
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- it MUST verify that `token_type` is supported
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- it MUST verify that `device_token` is non empty
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- it MUST verify that `installation_id` is non empty
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- it MUST verify that `version` is non-zero and greater than the currently stored version for the public key and installation id of the sender, if any
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- it MUST verify that `grant` is non empty and according to the [specs](#server-grant)
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- it MUST verify that `access_token` is a valid [`uuid`](https://tools.ietf.org/html/rfc4122)
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- it MUST verify that `apn_topic` is set if `token_type` is `APN_TOKEN`
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If the message can't be decrypted, the message MUST be discarded.
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If `token_type` is not supported, a response MUST be sent with `error` set to
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`UNSUPPORTED_TOKEN_TYPE`.
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If `token`,`installation_id`,`device_tokens`,`version` are empty, a response MUST
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be sent with `error` set to `MALFORMED_MESSAGE`.
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If the `version` is equal or less than the currently stored version, a response MUST
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be sent with `error` set to `VERSION_MISMATCH`.
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If any other error occurs the `error` should be set to `INTERNAL_ERROR`.
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If the response is successful `success` MUST be set to `true` otherwise a response MUST be sent with `success` set to `false`.
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`request_id` should be set to the `SHAKE-256` of the encrypted payload.
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The response MUST be sent on the [partitioned topic][./10-waku-usage.md#partitioned-topic] of the sender
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and MUST not be encrypted using the [secure transport](../docs/stable/5-secure-transport.md) to facilitate
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the usage of ephemeral keys.
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The payload of the response is:
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```protobuf
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message PushNotificationRegistrationResponse {
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bool success = 1;
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ErrorType error = 2;
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bytes request_id = 3;
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enum ErrorType {
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UNKNOWN_ERROR_TYPE = 0;
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MALFORMED_MESSAGE = 1;
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VERSION_MISMATCH = 2;
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UNSUPPORTED_TOKEN_TYPE = 3;
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INTERNAL_ERROR = 4;
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}
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}
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```
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The message MUST be wrapped in a [`ApplicationMetadataMessage`](../stable/6-payloads.6#payload-wrapper) with type set to `PUSH_NOTIFICATION_REGISTRATION_RESPONSE`.
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A client SHOULD listen for a response sent on the [partitioned topic][./10-waku-usage.md#partitioned-topic]
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that the key used to register.
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If `success` is `true` the client has registered successfully.
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If `success` is `false`:
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- If `MALFORMED_MESSAGE` is returned, the request SHOULD NOT be retried without ensuring
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that it is correctly formed.
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- If `INTERNAL_ERROR` is returned, the request MAY be retried, but the client MUST
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backoff exponentially
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A client MAY register with multiple Push Notification Servers in order to increase availability.
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A client SHOULD make sure that all the notification services they registered with have the same information about their tokens.
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If no response is returned the request SHOULD be considered failed and MAY be retried with the same server or a different one, but clients MUST exponentially backoff after each trial.
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If the request is successful the token SHOULD be [advertised](#advertising-a-push-notification-server) as described below
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### Query topic
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On successful registration the server MUST be listening to the topic derived from:
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```
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0XHexEncode(Shake256(CompressedClientPublicKey))
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```
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Using the topic derivation algorithm described [here](../stable/10-waku-usage.md#public-chats)
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and listen for client queries.
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### Server grant
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A push notification server needs to demonstrate to a client that it was authorized
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by the client to send them push notifications. This is done by building
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a grant which is specific to a given client-server pair.
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The grant is built as follow:
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```
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Signature(Keccak256(CompressedPublicKeyOfClient . CompressedPublicKeyOfServer . AccessToken), PrivateKeyOfClient)
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```
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When receiving a grant the server MUST be validate that the signature matches the registering client.
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## Re-registering with the push notification server
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A client SHOULD re-register with the node if the APN or FIREBASE token changes.
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When re-registering a client SHOULD ensure that it has the most up-to-date
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`PushNotificationRegistration` and increment `version` if necessary.
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Once re-registered, a client SHOULD advertise the changes.
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## Changing options
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This is handled in exactly the same way as re-registering above.
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## Unregistering from push notifications
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To unregister a client MUST send a `PushNotificationRegistration` request as described
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above with `unregister` set to `true`, or removing
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their device information.
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The server MUST remove all data about this user if `unregistering` is `true`,
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apart from the `hash` of the public key and the `version` of the last options,
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in order to make sure that old messages are not processed.
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A client MAY unregister from a server on explicit logout if multiple chat keys
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are used on a single device.
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## Advertising a push notification server
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Each user registered with one or more push notification servers SHOULD
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advertise periodically the push notification services that they have registered with for each device they own.
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```protobuf
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message PushNotificationQueryInfo {
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string access_token = 1;
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string installation_id = 2;
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bytes public_key = 3;
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repeated bytes allowed_user_list = 4;
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bytes grant = 5;
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uint64 version = 6;
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bytes server_public_key = 7;
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}
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message ContactCodeAdvertisement {
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repeated PushNotificationQueryInfo push_notification_info = 1;
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}
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```
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The message MUST be wrapped in a [`ApplicationMetadataMessage`](../stable/6-payloads.6#payload-wrapper) with type set to `PUSH_NOTIFICATION_QUERY_INFO`.
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If no filtering is done based on public keys,
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the access token SHOULD be included in the advertisement.
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Otherwise it SHOULD be left empty.
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This SHOULD be advertised on the [contact code topic](./10-waku-usage.md#contact-code-topic)
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and SHOULD be coupled with normal contact-code advertisement.
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Every time a user register or re-register with a push notification service, their
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contact-code SHOULD be re-advertised.
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Multiple servers MAY be advertised for the same `installation_id` for redundancy reasons.
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## Discovering a push notification server
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To discover a push notification service for a given user, their [contact code topic](./10-waku-usage.md#contact-code-topic)
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SHOULD be listened to.
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A mailserver can be queried for the specific topic to retrieve the most up-to-date
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contact code.
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## Querying the push notification server
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If a token is not present in the latest advertisement for a user, the server
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SHOULD be queried directly.
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To query a server a message:
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```protobuf
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message PushNotificationQuery {
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repeated bytes public_keys = 1;
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}
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```
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The message MUST be wrapped in a [`ApplicationMetadataMessage`](../stable/6-payloads.6#payload-wrapper) with type set to `PUSH_NOTIFICATION_QUERY`.
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MUST be sent to the server on the topic derived from the hashed public key of the
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key we are querying, as [described above](#query-topic).
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An ephemeral key SHOULD be used and SHOULD NOT be encrypted using the [secure transport](../docs/stable/5-secure-transport.md).
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If the server has information about the client a response MUST be sent:
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```protobuf
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message PushNotificationQueryInfo {
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string access_token = 1;
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string installation_id = 2;
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bytes public_key = 3;
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repeated bytes allowed_user_list = 4;
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bytes grant = 5;
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uint64 version = 6;
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bytes server_public_key = 7;
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}
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message PushNotificationQueryResponse {
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repeated PushNotificationQueryInfo info = 1;
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bytes message_id = 2;
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bool success = 3;
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}
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```
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A `PushNotificationQueryResponse` message MUST be wrapped in a [`ApplicationMetadataMessage`](../stable/6-payloads.6#payload-wrapper) with type set to `PUSH_NOTIFICATION_QUERY_RESPONSE`.
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Otherwise a response MUST NOT be sent.
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If `allowed_key_list` is not set `access_token` MUST be set and `allowed_key_list` MUST NOT
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be set.
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If `allowed_key_list` is set `allowed_key_list` MUST be set and `access_token` MUST NOT be set.
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If `access_token` is returned, the `access_token` SHOULD be used to send push notifications.
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If `allowed_key_list` are returned, the client SHOULD decrypt each
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token by generating an `AES-GCM` symmetric key from the Diffie–Hellman between the
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target client and itself
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If AES decryption succeeds it will return a valid [`uuid`](https://tools.ietf.org/html/rfc4122) which is what is used for access_token.
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The token SHOULD be used to send push notifications.
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The response MUST be sent on the [partitioned topic][./10-waku-usage.md#partitioned-topic] of the sender
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and MUST not be encrypted using the [secure transport](../docs/stable/5-secure-transport.md) to facilitate
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the usage of ephemeral keys.
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On receiving a response a client MUST verify `grant` to ensure that the server
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has been authorized to send push notification to a given client.
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## Sending a push notification
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When sending a push notification, only the `installation_id` for the devices targeted
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by the message SHOULD be used.
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If a message is for all the user devices, all the `installation_id` known to the client MAY be used.
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The number of devices MAY be capped in order to reduce resource consumption.
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At least 3 devices SHOULD be targeted, ordered by last activity.
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For any device that a token is available, or that a token is successfully queried,
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a push notification message SHOULD be sent to the corresponding push notification server.
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|
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```protobuf
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message PushNotification {
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string access_token = 1;
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string chat_id = 2;
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bytes public_key = 3;
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string installation_id = 4;
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bytes message = 5;
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PushNotificationType type = 6;
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enum PushNotificationType {
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UNKNOWN_PUSH_NOTIFICATION_TYPE = 0;
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MESSAGE = 1;
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MENTION = 2;
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}
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bytes author = 7;
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}
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message PushNotificationRequest {
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repeated PushNotification requests = 1;
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bytes message_id = 2;
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}
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```
|
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|
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A `PushNotificationRequest` message MUST be wrapped in a [`ApplicationMetadataMessage`](../stable/6-payloads.6#payload-wrapper) with type set to `PUSH_NOTIFICATION_REQUEST`.
|
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|
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Where `message` is the encrypted payload of the message and `chat_id` is the
|
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`SHAKE-256` of the `chat_id`.
|
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`message_id` is the id of the message
|
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`author` is the `SHAKE-256` of the public key of the sender.
|
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|
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If multiple server are available for a given push notification, only one notification
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MUST be sent.
|
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|
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If no response is received
|
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a client SHOULD wait at least 3 seconds, after which the request MAY be retried against a different server
|
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|
||
|
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This message SHOULD be sent using an ephemeral key.
|
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|
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On receiving the message, the push notification server MUST validate the access token.
|
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If the access token is valid, a notification MUST be sent to the gorush instance with the
|
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following data:
|
||
|
||
```
|
||
{
|
||
"notifications": [
|
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{
|
||
"tokens": ["token_a", "token_b"],
|
||
"platform": 1,
|
||
"message": "You have a new message",
|
||
"data": {
|
||
"chat_id": chat_id,
|
||
"message": message,
|
||
"installation_ids": [installation_id_1, installation_id_2]
|
||
}
|
||
}
|
||
]
|
||
}
|
||
```
|
||
|
||
Where platform is `1` for IOS and `2` for Firebase, according to the [gorush
|
||
documentation](https://github.com/appleboy/gorush)
|
||
|
||
A server MUST return a response message:
|
||
|
||
```protobuf
|
||
message PushNotificationReport {
|
||
bool success = 1;
|
||
ErrorType error = 2;
|
||
enum ErrorType {
|
||
UNKNOWN_ERROR_TYPE = 0;
|
||
WRONG_TOKEN = 1;
|
||
INTERNAL_ERROR = 2;
|
||
NOT_REGISTERED = 3;
|
||
}
|
||
bytes public_key = 3;
|
||
string installation_id = 4;
|
||
}
|
||
|
||
message PushNotificationResponse {
|
||
bytes message_id = 1;
|
||
repeated PushNotificationReport reports = 2;
|
||
}
|
||
```
|
||
|
||
|
||
A `PushNotificationResponse` message MUST be wrapped in a [`ApplicationMetadataMessage`](../stable/6-payloads.6#payload-wrapper) with type set to `PUSH_NOTIFICATION_RESPONSE`.
|
||
|
||
Where `message_id` is the `message_id` sent by the client.
|
||
|
||
The response MUST be sent on the [partitioned topic][./10-waku-usage.md#partitioned-topic] of the sender
|
||
and MUST not be encrypted using the [secure transport](../docs/stable/5-secure-transport.md) to facilitate
|
||
the usage of ephemeral keys.
|
||
|
||
If the request is accepted `success` MUST be set to `true`.
|
||
Otherwise `success` MUST be set to `false`.
|
||
|
||
If `error` is `BAD_TOKEN` the client MAY query again the server for the token and
|
||
retry the request.
|
||
|
||
If `error` is `INTERNAL_ERROR` the client MAY retry the request.
|
||
|
||
## Flow
|
||
|
||
### Registration process
|
||
|
||
- A client will generate a notification token through `APN` or `Firebase`.
|
||
- The client will [register](#registering-with-the-push-notification-service) with one or more push notification server of their choosing.
|
||
- The server should process the response and respond according to the success of the operation
|
||
- If the request is not successful it might be retried, and adjusted according to the response. A different server can be also used.
|
||
- Once the request is successful the client should [advertise](#advertising-a-push-notification-server) the new coordinates
|
||
|
||
### Sending a notification
|
||
|
||
- A client should prepare a message and extract the targeted installation-ids
|
||
- It should retrieve the most up to date information for a given user, either by
|
||
querying a push notification server, a mailserver if not listening already to the given topic, or checking
|
||
the database locally
|
||
- It should then [send](#sending-a-push-notification) a push notification according
|
||
to the rules described
|
||
- The server should then send a request to the gorush server including all the required
|
||
information
|
||
|
||
### Receiving a push notification
|
||
|
||
- On receiving the notification, a client can open the right account by checking the
|
||
`installation_id` included. The `chat_id` MAY be used to open the chat if present.
|
||
- `message` can be decrypted and presented to the user. Otherwise messages can be pulled from the mailserver if the `message_id` is no already present.
|
||
|
||
## Protobuf description
|
||
|
||
### PushNotificationRegistration
|
||
|
||
`token_type`: the type of token. Currently supported is `APN_TOKEN` for Apple Push
|
||
`device_token`: the actual push notification token sent by `Firebase` or `APN`
|
||
and `FIREBASE_TOKEN` for firebase.
|
||
`installation_id`: the [`installation_id`](./2-account.md) of the device
|
||
`access_token`: the access token that will be given to clients to send push notifications
|
||
`enabled`: whether the device wants to be sent push notifications
|
||
`version`: a monotonically increasing number identifying the current `PushNotificationRegistration`. Any time anything is changed in the record it MUST be increased by the client, otherwise the request will not be accepted.
|
||
`allowed_key_list`: a list of `access_token` encrypted with the AES key generated
|
||
by Diffie–Hellman between the publisher and the allowed
|
||
contact.
|
||
`blocked_chat_list`: a list of `SHA2-256` hashes of chat ids.
|
||
Any chat id in this list will not trigger a notification.
|
||
`unregister`: whether the account should be unregistered
|
||
`grant`: the grant for this specific server
|
||
`allow_from_contacts_only`: whether the client only wants push notifications from contacts
|
||
`apn_topic`: the APN topic for the push notification
|
||
`block_mentions`: whether the client does not want to be notified on mentions
|
||
`allowed_mentions_chat_list`: a list of `SHA2-256` hashes of chat ids where we want to receive mentions
|
||
|
||
#### Data disclosed
|
||
|
||
- Type of device owned by a given user
|
||
- The `FIREBASE` or `APN` push notification token
|
||
- Hash of the chat_id a user is not interested in for notifications
|
||
- The times a push notification record has been modified by the user
|
||
- The number of contacts a client has, in case `allowed_key_list` is set
|
||
|
||
### PushNotificationRegistrationResponse
|
||
|
||
`success`: whether the registration was successful
|
||
`error`: the error type, if any
|
||
`request_id`: the `SHAKE-256` hash of the `signature` of the request
|
||
`preferences`: the server stored preferences in case of an error
|
||
|
||
### ContactCodeAdvertisement
|
||
|
||
`push_notification_info`: the information for each device advertised
|
||
|
||
#### Data disclosed
|
||
|
||
- The chat key of the sender
|
||
|
||
|
||
### PushNotificationQuery
|
||
|
||
`public_keys`: the `SHAKE-256` of the public keys the client is interested in
|
||
|
||
#### Data disclosed
|
||
|
||
- The hash of the public keys the client is interested in
|
||
|
||
### PushNotificationQueryInfo
|
||
|
||
`access_token`: the access token used to send a push notification
|
||
`installation_id`: the `installation_id` of the device associated with the `access_token`
|
||
`public_key`: the `SHAKE-256` of the public key associated with this `access_token` and `installation_id`
|
||
`allowed_key_list`: a list of encrypted access tokens to be returned
|
||
to the client in case there's any filtering on public keys in place.
|
||
`grant`: the grant used to register with this server.
|
||
`version`: the version of the registration on the server.
|
||
`server_public_key`: the compressed public key of the server.
|
||
|
||
### PushNotificationQueryResponse
|
||
|
||
`info`: a list of `PushNotificationQueryInfo`.
|
||
`message_id`: the message id of the `PushNotificationQueryInfo` the server is replying to.
|
||
`success`: whether the query was successful.
|
||
|
||
### PushNotification
|
||
|
||
`access_token`: the access token used to send a push notification.
|
||
`chat_id`: the `SHAKE-256` of the `chat_id`.
|
||
`public_key`: the `SHAKE-256` of the compressed public key of the receiving client.
|
||
`installation_id`: the installation id of the receiving client.
|
||
`message`: the encrypted message that is being notified on.
|
||
`type`: the type of the push notification, either `MESSAGE` or `MENTION`
|
||
`author`: the `SHAKE-256` of the public key of the sender
|
||
|
||
### Data disclosed
|
||
|
||
- The `SHAKE-256` of the `chat_id` the notification is to be sent for
|
||
- The cypher text of the message
|
||
- The `SHAKE-256` of the public key of the sender
|
||
- The type of notification
|
||
|
||
### PushNotificationRequest
|
||
|
||
`requests`: a list of `PushNotification`
|
||
`message_id`: the [status message id](./6-payloads.md)
|
||
|
||
### Data disclosed
|
||
|
||
- The status message id for which the notification is for
|
||
|
||
### PushNotificationResponse
|
||
|
||
`message_id`: the `message_id` being notified on.
|
||
`reports`: a list of `PushNotificationReport`
|
||
|
||
### PushNotificationReport
|
||
|
||
`success`: whether the push notification was successful.
|
||
`error`: the type of the error in case of failure.
|
||
`public_key`: the public key of the user being notified.
|
||
`installation_id`: the installation id of the user being notified.
|
||
|
||
## Anonymous mode of operations
|
||
|
||
An anonymous mode of operations MAY be provided by the client, where the
|
||
responsibility of propagating information about the user is left to the client,
|
||
in order to preserve privacy.
|
||
|
||
A client in anonymous mode can register with the server using a key different
|
||
from their chat key.
|
||
This will hide their real chat key.
|
||
|
||
This public key is effectively a secret and SHOULD only be disclosed to clients that you the user wants to be notified by.
|
||
|
||
A client MAY advertise the access token on the contact-code topic of the key generated.
|
||
A client MAY share their public key through [contact updates](./6-payloads.md#contact-update)
|
||
|
||
A client receiving a push notification public key SHOULD listen to the contact code
|
||
topic of the push notification public key for updates.
|
||
|
||
The method described above effectively does not share the identity of the sender
|
||
nor the receiver to the server, but MAY result in missing push notifications as
|
||
the propagation of the secret is left to the client.
|
||
|
||
This can be mitigated by [device syncing](./6-payloads.md), but not completely
|
||
addressed.
|
||
|
||
## Security considerations
|
||
|
||
If no anonymous mode is used, when registering with a push notification service a client discloses:
|
||
|
||
- The chat key
|
||
- The devices that will receive notifications
|
||
|
||
A client MAY disclose:
|
||
|
||
- The hash of the chat_ids they want to filter out
|
||
|
||
When running in anonymous mode, the client's chat key is not disclosed.
|
||
|
||
When querying a push notification server a client will disclose:
|
||
|
||
- That it is interested in sending push notification to another client,
|
||
but the querying client's chat key is not disclosed
|
||
|
||
When sending a push notification a client discloses:
|
||
- The `SHAKE-256` of the chat id
|
||
|
||
[//]: This section can be removed, for now leaving it here in order to help with the
|
||
review process. Point can be integrated, suggestion welcome.
|
||
|
||
## FAQ
|
||
|
||
### Why having ACL done at the server side and not the client?
|
||
|
||
We looked into silent notification for
|
||
[IOS](https://developer.apple.com/documentation/usernotifications/setting_up_a_remote_notification_server/pushing_background_updates_to_your_app) (android has no equivalent)
|
||
but can't be used as it's expected to receive maximum 2/3 per hour, so not our use case. There
|
||
are also issue when the user force quit the app.
|
||
|
||
### Why using an access token?
|
||
|
||
The access token is used to decouple the requesting information from the user from
|
||
actually sending the push notification.
|
||
|
||
Some ACL is necessary otherwise it would be too easy to spam users (it's still fairly
|
||
trivial, but with this method you could allow only contacts to send you push notifications).
|
||
|
||
Therefore your identity must be revealed to the server either when sending or querying.
|
||
|
||
By using an access token we increase deniability, as the server would know
|
||
who requested the token but not necessarily who sent a push notification.
|
||
Correlation between the two can be trivial in some cases.
|
||
|
||
This also allows a mode of use as we had before, where the server does not propagate
|
||
info at all, and it's left to the user to propagate the token, through contact requests
|
||
for example.
|
||
|
||
### Why advertise with the bundle?
|
||
|
||
Advertising with the bundle allows us to piggy-back on an already implemented behavior
|
||
and save some bandwidth in cases where is not filtering by public keys
|
||
|
||
### What's the bandwidth impact for this?
|
||
|
||
Generally speaking, for each 1-to-1 message and group chat message you will sending
|
||
1 and `number of participants` push notifications. This can be optimized if
|
||
multiple users are using the same push notification server. Queries have also
|
||
a bandwidth impact but they are made only when actually needed
|
||
|
||
### What's the information disclosed?
|
||
|
||
The data disclosed with each message sent by the client is above, but for a summary:
|
||
|
||
When you register with a push notification service you may disclose:
|
||
|
||
1) Your chat key
|
||
2) Which devices you have
|
||
3) The hash of the chat_ids you want to filter out
|
||
4) The hash of the public keys you are interested/not interested in
|
||
|
||
When you query a notification service you may disclose:
|
||
|
||
1) Your chat key
|
||
2) The fact that you are interested in sending push notification to a given user
|
||
|
||
Effectively this is fairly revealing if the user has a whitelist implemented.
|
||
Therefore sending notification should be optional.
|
||
|
||
### What prevents a user from generating a random key and getting an access token and spamming?
|
||
|
||
Nothing really, that's the same as the status app as a whole. the only mechanism that prevents
|
||
this is using a white-list as described above, but that implies disclosing your true identity to the push notification server.
|
||
|
||
### Why not 0-knowledge proofs/quantum computing
|
||
|
||
We start simple, we can iterate
|
||
|
||
### How to handle backward/forward compatibility
|
||
|
||
Most of the request have a target, so protocol negotiation can happen. We cannot negotiated
|
||
the advertisement as that's effectively a broadcast, but those info should not change and we can
|
||
always accrete the message.
|
||
|
||
### Why ack_key?
|
||
|
||
That's necessary to avoid duplicated push notifications and allow for the retry
|
||
in case the notification is not successful.
|
||
|
||
Deduplication of the push notification is done on the client side, to reduce a bit
|
||
of centralization and also in order not to have to modify gorush.
|
||
|
||
### Can I run my own node?
|
||
|
||
Sure, the methods allow that
|
||
|
||
### Can I register with multiple nodes for redundancy
|
||
|
||
Yep
|
||
|
||
### What does my node disclose?
|
||
|
||
Your node will disclose the IP address is running from, as it makes an HTTP post to
|
||
gorush. A waku adapter could be used, but please not now.
|
||
|
||
### Does this have high-reliability requirements?
|
||
|
||
The gorush server yes, no way around it.
|
||
|
||
The rest, kind of, at least one node having your token needs to be up for you to receive notifications.
|
||
But you can register with multiple servers (desktop, status, etc) if that's a concern.
|
||
|
||
### Can someone else (i.e not status) run this?
|
||
|
||
Push notification servers can be run by anyone. Gorush can be run by anyone I take,
|
||
but we are in charge of the certificate, so they would not be able to notify status-clients.
|
||
|
||
## Changelog
|
||
|
||
### Version 0.1
|
||
|
||
Released [](https://github.com/status-im/specs/commit/)
|
||
|
||
- Initial version
|
||
|
||
## Copyright
|
||
|
||
Copyright and related rights waived via [CC0](https://creativecommons.org/publicdomain/zero/1.0/).
|