feat: show call participants in room list (Discord-style)

apps/web/src/utils/DecryptFile.ts

@@ -0,0 +1,73 @@
+/*
+Copyright 2024 New Vector Ltd.
+Copyright 2016-2018 , 2021 The Matrix.org Foundation C.I.C.
+
+SPDX-License-Identifier: AGPL-3.0-only OR GPL-3.0-only OR LicenseRef-Element-Commercial
+Please see LICENSE files in the repository root for full details.
+*/
+
+// Pull in the encryption lib so that we can decrypt attachments.
+import encrypt from "matrix-encrypt-attachment";
+import { parseErrorResponse } from "matrix-js-sdk/src/matrix";
+import { type EncryptedFile, type MediaEventInfo } from "matrix-js-sdk/src/types";
+
+import { mediaFromContent } from "../customisations/Media";
+import { getBlobSafeMimeType } from "./blobs";
+
+export class DownloadError extends Error {
+    public constructor(e: Error) {
+        super(e.message);
+        this.name = "DownloadError";
+        this.stack = e.stack;
+    }
+}
+
+export class DecryptError extends Error {
+    public constructor(e: Error) {
+        super(e.message);
+        this.name = "DecryptError";
+        this.stack = e.stack;
+    }
+}
+
+/**
+ * Decrypt a file attached to a matrix event.
+ * @param {EncryptedFile} file The encrypted file information taken from the matrix event.
+ *   This passed to [link]{@link https://github.com/matrix-org/matrix-encrypt-attachment}
+ *   as the encryption info object, so will also have the those keys in addition to
+ *   the keys below.
+ * @param {MediaEventInfo} info The info parameter taken from the matrix event.
+ * @returns {Promise<Blob>} Resolves to a Blob of the file.
+ */
+export async function decryptFile(file?: EncryptedFile, info?: MediaEventInfo): Promise<Blob> {
+    // throws if file is falsy
+    const media = mediaFromContent({ file });
+
+    let responseData: ArrayBuffer;
+    try {
+        // Download the encrypted file as an array buffer.
+        const response = await media.downloadSource();
+        if (!response.ok) {
+            throw parseErrorResponse(response, await response.text());
+        }
+        responseData = await response.arrayBuffer();
+    } catch (e) {
+        throw new DownloadError(e as Error);
+    }
+
+    try {
+        // Decrypt the array buffer using the information taken from the event content.
+        const dataArray = await encrypt.decryptAttachment(responseData, file!);
+        // Turn the array into a Blob and give it the correct MIME-type.
+
+        // IMPORTANT: we must not allow scriptable mime-types into Blobs otherwise
+        // they introduce XSS attacks if the Blob URI is viewed directly in the
+        // browser (e.g. by copying the URI into a new tab or window.)
+        // See warning at top of file.
+        const mimetype = getBlobSafeMimeType(info?.mimetype?.split(";")[0].trim() ?? "");
+
+        return new Blob([dataArray], { type: mimetype });
+    } catch (e) {
+        throw new DecryptError(e as Error);
+    }
+}