Adding upstream version 115.7.0esr.upstream/115.7.0esrupstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

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+# Push
+<div class="note">
+<div class="admonition-title">Note</div>
+This document describes how Firefox implements the Web Push standard internally, and is intended for developers working directly on Push. If you are looking for how to consume push, please refer to the <a href="https://developer.mozilla.org/en-US/docs/Web/API/Push_API" target="_blank">following MDN document</a>
+
+</div>
+
+## High level push architecture
+The following sequence diagram describes the high level push architecture as observed by web application. The diagram describes the interactions between a Web application's client code running in the browser, Firefox, [Autopush](https://autopush.readthedocs.io/en/latest/) (Firefox's push server that delivers push notifications) and a third party server that sends the push notifications to Autopush
+
+The dotted lines are done by the consumer of push.
+```{mermaid}
+sequenceDiagram
+	participant TP as Web Application JS
+	participant F as Firefox
+	participant A as Autopush
+	participant TPS as Third party Server
+		TP->>F: subscribe(scope)
+		activate TP
+		activate F
+		F->>A: subscribe(scope) using web socket
+		activate A
+		A->>F: URL
+		deactivate A
+		F->>F: Create pub/privKey Encryption pair
+		F->>F: Persist URL, pubKey, privKey indexed using an id derived from scope
+		F->>TP: URL + pubKey
+		deactivate F
+		TP-->>TPS: URL + pubKey
+		deactivate TP
+		TPS-->>TPS: Encrypt payload using pubKey
+		TPS-->>A: Send encrypted payload using URL
+		activate A
+		A->>F: Send encrypted payload using web socket
+		deactivate A
+		activate F
+		F->>F: Decrypt payload using privKey
+		F->>F: Display Notification
+		deactivate F
+```
+
+## Flow diagram for source code
+
+The source code for push is available under [`dom/push`](https://searchfox.org/mozilla-central/source/dom/push) in mozilla-central.
+
+The following flow diagram describes how different modules interact with each other to provide the push API to consumers.
+
+```{mermaid}
+flowchart TD
+    subgraph Public API
+
+    W[Third party Web app]-->|imports| P[PushManager.webidl]
+    end
+    subgraph Browser Code
+        P-->|Implemented by| MM
+        MM{Main Thread?}-->|Yes| B[Push.sys.mjs]
+        MM -->|NO| A[PushManager.cpp]
+        B-->|subscribe,getSubscription| D[PushComponents.sys.mjs]
+        A-->|subscribe,getSubscription| D
+        D-->|subscribe,getSubscription| M[PushService.sys.mjs]
+        M-->|Storage| S[PushDB.sys.mjs]
+        M-->|Network| N[PushWebSocket.sys.mjs]
+        F[FxAccountsPush.sys.mjs] -->|uses| D
+    end
+    subgraph Server
+    N-. Send, Receive.-> O[Autopush]
+    end
+    subgraph Local Storage
+    S-->|Read,Write| PP[(IndexedDB)]
+    end
+```
+
+## The Push Web Socket
+Push in Firefox Desktop communicates with Autopush using a web socket connection.
+
+The web socket connection is created as the browser initializes and is managed by the following state diagram.
+
+```{mermaid}
+stateDiagram-v2
+		state "Shut Down" as SD
+		state "Waiting for WebSocket to start" as W1
+		state "Waiting for server hello" as W2
+		state "Ready" as R
+    [*] --> SD
+		 SD --> W1: beginWSSetup
+		 W1 --> W2: wsOnStart Success
+		 W2 --> R: handleHelloReply
+		 R --> R: send (subscribe)
+         R --> R: Receive + notify observers
+		 R --> SD: wsOnStop
+		 R --> SD: sendPing Fails
+		 W1 --> SD: wsOnStart fails
+		 W2 --> SD: invalid server hello
+		 R --> [*]
+```
+
+Once the Push web socket is on the `Ready` state, it is ready to send new subscriptions to Autopush, and receive push notifications from those subscriptions.
+
+Push uses an observer pattern to notify observers of any incoming push notifications. See the [high level architecture](#high-level-push-architecture) section.
+
+
+## Push Storage
+Push uses IndexedDB to store subscriptions for the following reasons:
+1. In case the consumer attempts to re-subscribe, storage is used as a cache to serve the URL and the public key
+1. In order to persist the private key, so that it can be used to decrypt any incoming push notifications
+
+The following is what gets persisted:
+
+```{mermaid}
+erDiagram
+    Subscription {
+        string channelID "Key, Derived from scope"
+        string pushEndpoint "Unique endpoint for this subscription"
+        string scope "Usually the origin, unique value for internal consumers"
+        Object p256dhPublicKey "Object representing the public key"
+        Object p256dhPrivateKey "Object representing the private key"
+    }
+```