Improve plaintext formatting of Matrix messages sent via webhooks

changelog.d/778.feature

@@ -0,0 +1 @@
+Improve plaintext formatting of Matrix messages sent via webhooks.

docs/link_channels.md

@@ -6,6 +6,13 @@ first the individual Matrix room and Slack channel need to be created, and then
 a command needs to be issued in the administration console room to add the link
 to the bridge's database.
 
+## Determining your channel ID
+
+You'll need a "channel ID" to link rooms.
+To obtain it, right-click your channel name in Slack and select "Copy Link".
+The channel id is the last argument in the url
+(`https://XXX.Slack.com/messages/<channel id>/`)
+
 ## RTM API
 
 The Real Time Messaging (RTM) API is the newer and recommended way to use the bridge.
@@ -47,12 +54,9 @@ The Real Time Messaging (RTM) API is the newer and recommended way to use the br
        /invite @bot-user-name
        ```
 
-       You will also need to determine the "channel ID" that Slack uses to identify
-       the channel. Right-click your channel name in Slack and select "Copy Link".
-       The channel id is the last argument in the url
-       (`https://XXX.Slack.com/messages/<channel id>/`)
+   4. Obtain the channel ID (see "Determining your channel ID")
 
-   4. Issue a ``link`` command in the administration control room with these
+   5. Issue a ``link`` command in the administration control room with these
       collected values as arguments:
 
       ```
@@ -104,17 +108,13 @@ although it can be useful for single channels or if you are using Mattermost.
    of its `token` field. Add a URL to this web hook pointing back at the
    application service port you configured during setup.
 
-   You will also need to determine the "channel ID" that Slack uses to identify
-   the channel. Unfortunately, it is not easily obtained from the Slack UI. The
-   easiest way to do this is to send a message from Slack to the bridge; the
-   bridge will log the channel ID as part of the unrecognised message output.
-   You can then take note of the `channel_id` field.
+1. Obtain the channel ID (see "Determining your channel ID")
 
 1. Issue a ``link`` command in the administration control room with these
    collected values as arguments:
 
     ```
-    link --channel_id CHANNELID --room !the-matrix:room.id --webhook_url https://hooks.Slack.com/services/ABC/DEF/123
+    link --channel_id CHANNELID --room !the-matrix:room.id --webhook_url https://hooks.Slack.com/services/ABC/DEF/123 --webhook_token TOKEN
     ```
 
 ## Unlink Channels

package.json

@@ -86,6 +86,7 @@
     "eslint-plugin-react-hooks": "^4.6.0",
     "js-yaml": "^4.1.0",
     "mocha": "^10.0.0",
+    "node-mocks-http": "^1.14.1",
     "nyc": "^15.1.0",
     "postcss": "^8.4.21",
     "prom-client": "^14.0.1",

src/AdminCommands.ts

@@ -181,11 +181,12 @@ export class AdminCommands {
         return new AdminCommand(
             "link",
             "connect a Matrix and a Slack room together",
-            async ({respond, room, channel_id, webhook_url, slack_bot_token, team_id}: {
+            async ({respond, room, channel_id, webhook_url, webhook_token, slack_bot_token, team_id}: {
                 respond: ResponseCallback,
                 room?: string,
                 channel_id?: string,
                 webhook_url?: string,
+                webhook_token?: string,
                 slack_bot_token?: string,
                 team_id?: string,
             }) => {
@@ -200,6 +201,7 @@ export class AdminCommands {
                         team_id,
                         slack_channel_id: channel_id,
                         slack_webhook_uri: webhook_url,
+                        slack_webhook_token: webhook_token,
                     });
                     respond("Room is now " + r.getStatus());
                     if (r.SlackWebhookUri) {
@@ -234,6 +236,10 @@ export class AdminCommands {
                     alias: "u",
                     description: "Slack webhook URL. Used with Slack outgoing hooks integration",
                 },
+                webhook_token: {
+                    alias: "k",
+                    description: "Slack webhook token. Used with Slack outgoing hooks integration",
+                },
             },
         );
     }

src/BridgedRoom.ts

@@ -14,7 +14,7 @@
 limitations under the License.
 */
 
-import axios from "axios";
+import axios, { AxiosInstance } from "axios";
 import { Logger, Intent } from "matrix-appservice-bridge";
 import { SlackGhost } from "./SlackGhost";
 import { Main, METRIC_SENT_MESSAGES } from "./Main";
@@ -36,6 +36,7 @@
     slack_channel_name?: string;
     slack_channel_id?: string;
     slack_webhook_uri?: string;
+    slack_webhook_token?: string;
     slack_team_id?: string;
     slack_type: SlackChannelTypes;
     is_private?: boolean;
@@ -95,6 +96,14 @@
         this.setValue("slackWebhookUri", value);
     }
 
+    public get SlackWebhookToken(): string|undefined {
+        return this.slackWebhookToken;
+    }
+
+    public set SlackWebhookToken(value: string|undefined) {
+        this.setValue("slackWebhookToken", value);
+    }
+
     public get MatrixRoomId(): string {
         return this.matrixRoomId;
     }
@@ -135,6 +144,7 @@
             slack_channel_name: entry.remote.name,
             slack_team_id: entry.remote.slack_team_id,
             slack_webhook_uri: entry.remote.webhook_uri,
+            slack_webhook_token: entry.remote.webhook_token,
             puppet_owner: entry.remote.puppet_owner,
             is_private: entry.remote.slack_private,
             slack_type: entry.remote.slack_type as SlackChannelTypes,
@@ -146,6 +156,7 @@
     private slackChannelName?: string;
     private slackChannelId?: string;
     private slackWebhookUri?: string;
+    private slackWebhookToken?: string;
     private slackTeamId?: string;
     private slackType: SlackChannelTypes;
     private isPrivate?: boolean;
@@ -169,7 +180,13 @@
      */
     private dirty: boolean;
 
-    constructor(private main: Main, opts: IBridgedRoomOpts, private team?: TeamEntry, private botClient?: WebClient) {
+    constructor(
+        private main: Main,
+        opts: IBridgedRoomOpts,
+        private team?: TeamEntry,
+        private botClient?: WebClient,
+        private httpClient: AxiosInstance = axios
+    ) {
 
         this.MatrixRoomActive = true;
         if (!opts.inbound_id) {
@@ -184,6 +201,7 @@
         this.slackChannelName = opts.slack_channel_name;
         this.slackChannelId = opts.slack_channel_id;
         this.slackWebhookUri = opts.slack_webhook_uri;
+        this.slackWebhookToken = opts.slack_webhook_token;
         this.slackTeamId = opts.slack_team_id;
         this.slackType = opts.slack_type || "channel";
         if (opts.is_private === undefined) {
@@ -241,13 +259,14 @@
             id: `INTEG-${this.inboundId}`,
             matrix_id: this.matrixRoomId,
             remote: {
                 id: this.slackChannelId!,
                 name: this.slackChannelName!,
                 slack_team_id: this.slackTeamId!,
                 slack_type: this.slackType!,
                 slack_private: this.isPrivate!,
                 webhook_uri: this.slackWebhookUri!,
+                webhook_token: this.slackWebhookToken!,
                 puppet_owner: this.puppetOwner!,
             },
             remote_id: this.inboundId,
         };
@@ -256,7 +275,7 @@
     }
 
     public async getClientForRequest(userId: string): Promise<{id: string, client: WebClient}|null> {
         const puppet = await this.main.clientFactory.getClientForUserWithId(this.SlackTeamId!, userId);
         if (puppet) {
             return puppet;
         }
@@ -457,7 +476,7 @@
             }
             log.debug("Room might be encrypted, uploading file to Slack");
             // Media might be encrypted, upload it to Slack to be safe.
-            const response = await axios.get<ArrayBuffer>(matrixToSlackResult.encrypted_file, {
+            const response = await this.httpClient.get<ArrayBuffer>(matrixToSlackResult.encrypted_file, {
                 headers: {
                     Authorization: `Bearer ${slackClient.token}`,
                 },
@@ -513,13 +532,27 @@
 
         user.bumpATime();
         this.matrixATime = Date.now() / 1000;
+
         if (!slackClient) {
             if (!this.slackWebhookUri) {
                 throw Error('No slackClient and slackWebhookUri');
             }
-            const webhookRes = await axios.post(this.slackWebhookUri, body);
+            let plainText = body.text;
+            if (!plainText && body.attachments) {
+                const parts: string[] = [];
+                for (const attachment of body.attachments) {
+                    parts.push(`Uploaded "${attachment.fallback}": ${attachment.image_url}`);
+                }
+                plainText = parts.join("\n");
+            }
+            if (!plainText) {
+                log.warn("Nothing to send via webhook from message", body);
+                return false;
+            }
+            const webhookRes = await this.httpClient.post(this.slackWebhookUri, { text: `<${body.username}> ${plainText}` });
             if (webhookRes.status !== 200) {
                 log.error("Failed to send webhook message");
+                return false;
             }
             // Webhooks don't give us any ID, so we can't store this.
             return true;
@@ -885,7 +918,7 @@
         if (file.mode === "snippet") {
             let htmlString: string;
             try {
-                const fileReq = await axios.get<string>(filePrivateUrl, {
+                const fileReq = await this.httpClient.get<string>(filePrivateUrl, {
                     headers: {
                         // Token is checked above.
                         Authorization: `Bearer ${authToken}`,

src/Main.ts

@@ -1351,6 +1351,7 @@ export class Main {
     public async actionLink(opts: {
         matrix_room_id: string,
         slack_webhook_uri?: string,
+        slack_webhook_token?: string,
         slack_channel_id?: string,
         slack_bot_token?: string,
         team_id?: string,
@@ -1450,6 +1451,11 @@ export class Main {
 
         if (opts.slack_webhook_uri) {
             room.SlackWebhookUri = opts.slack_webhook_uri;
+            if (opts.slack_webhook_token) {
+                room.SlackWebhookToken = opts.slack_webhook_token;
+            } else {
+                throw new Error("Cannot link via a webhook without a webhook token");
+            }
         }
 
         if (opts.slack_channel_id) {

src/SlackHookHandler.ts

@@ -67,7 +67,7 @@ export class SlackHookHandler extends BaseSlackHandler {
             createServer = (cb) => httpsCreate(tlsOptions, cb);
         }
         return new Promise<void>((resolve, reject) => {
-            const srv = createServer(this.onRequest.bind(this));
+            const srv = createServer(this._onRequest.bind(this));
             srv.once("error", reject);
             srv.listen(port, () => {
                 const protocol = tlsConfig ? "https" : "http";
@@ -85,7 +85,7 @@ export class SlackHookHandler extends BaseSlackHandler {
         }
     }
 
-    private onRequest(req: IncomingMessage, res: ServerResponse) {
+    public _onRequest(req: IncomingMessage, res: ServerResponse) {
         const HTTP_SERVER_ERROR = 500;
         const {method, url } = req;
         if (!method || !url) {
@@ -234,6 +234,16 @@ export class SlackHookHandler extends BaseSlackHandler {
             return;
         }
 
+        if (params.token !== room.SlackWebhookToken) {
+            log.warn(`Ignoring message for ${room.MatrixRoomId} due to webhook token mismatch`);
+
+            response.writeHead(HTTP_CODES.FORBIDDEN);
+            response.end();
+
+            endTimer({outcome: "dropped"});
+            return;
+        }
+
         if (method === "POST" && path === "post") {
             try {
                 if (!room) {

src/datastore/Models.ts

@@ -28,6 +28,7 @@ export interface RoomEntry {
         id: string;
         name: string;
         webhook_uri?: string;
+        webhook_token?: string;
         slack_private?: boolean;
         puppet_owner?: string;
     };