Add room intro warning when e2ee is not enabled

res/css/views/rooms/_NewRoomIntro.scss

@@ -69,4 +69,24 @@ limitations under the License.
         font-size: $font-15px;
         color: $secondary-fg-color;
     }
+
+    .mx_NewRoomIntro_message:not(:first-child) {
+        padding-top: 1em;
+        margin-top: 1em;
+        border-top: 1px solid currentColor;
+    }
+
+    .mx_NewRoomIntro_message[role=alert]::before {
+        --size: 25px;
+        content: "!";
+        float: left;
+        border-radius: 50%;
+        width: var(--size);
+        height: var(--size);
+        line-height: var(--size);
+        text-align: center;
+        background: $button-danger-bg-color;
+        color: #fff;
+        margin-right: calc(var(--size) / 2);
+    }
 }

src/components/views/rooms/NewRoomIntro.tsx

@@ -31,6 +31,14 @@ import dis from "../../../dispatcher/dispatcher";
 import SpaceStore from "../../../stores/SpaceStore";
 import {showSpaceInvite} from "../../../utils/space";
 
+import { privateShouldBeEncrypted } from "../../../createRoom";
+
+function hasExpectedEncryptionSettings(room): boolean {
+    const isEncrypted: boolean = room._client.isRoomEncrypted(room.roomId);
+    const isPublic: boolean = room.getJoinRule() === "public";
+    return isPublic || !privateShouldBeEncrypted() || isEncrypted;
+}
+
 const NewRoomIntro = () => {
     const cli = useContext(MatrixClientContext);
     const {room, roomId} = useContext(RoomContext);
@@ -168,6 +176,18 @@ const NewRoomIntro = () => {
 
     return <div className="mx_NewRoomIntro">
         { body }
+
+        { !hasExpectedEncryptionSettings(room) && <p className="mx_NewRoomIntro_message" role="alert">
+            {_t("Messages in this room are not end-to-end encrypted. " +
+                    "Messages sent in an unencrypted room can be seen by the server and third parties. " +
+                    "<a>Learn more about encryption.</a>", {},
+            {
+                a: sub => <a href="https://element.io/help#encryption"
+                    rel="noreferrer noopener" target="_blank"
+                >{sub}</a>,
+            })}
+
+        </p>}
     </div>;
 };
 

src/i18n/strings/en_EN.json

@@ -1490,6 +1490,7 @@
     "Invite to just this room": "Invite to just this room",
     "Add a photo, so people can easily spot your room.": "Add a photo, so people can easily spot your room.",
     "This is the start of <roomName/>.": "This is the start of <roomName/>.",
+    "Messages in this room are not end-to-end encrypted. Messages sent in an unencrypted room can be seen by the server and third parties. <a>Learn more about encryption.</a>": "Messages in this room are not end-to-end encrypted. Messages sent in an unencrypted room can be seen by the server and third parties. <a>Learn more about encryption.</a>",
     "No pinned messages.": "No pinned messages.",
     "Loading...": "Loading...",
     "Pinned Messages": "Pinned Messages",