Add option to disable media preview.

This disables image previews iff prefetchStorage is disabled. This
stops the client from making any requests to third-party sites.

defaults/config.js

@@ -110,6 +110,18 @@ module.exports = {
 	// This value is set to `false` by default.
 	prefetch: false,
 
+	// ### `disableMediaPreview`
+	//
+	// When set to `true`, The Lounge will not preview media (images, video and
+	// audio) hosted on third-party sites. This ensures the client does not
+	// make any requests to external sites. If `prefetchStorage` is enabled,
+	// images proxied via the The Lounge will be previewed.
+	//
+	// This has no effect if `prefetch` is set to `false`.
+	//
+	// This value is set to `false` by default.
+	disableMediaPreview: false,
+
 	// ### `prefetchStorage`
 
 	// When set to `true`, The Lounge will store and proxy prefetched images and

src/plugins/irc-events/link.js

@@ -84,11 +84,6 @@ function parseHtml(preview, res, client) {
 					$('meta[property="og:description"]').attr("content") ||
 					$('meta[name="description"]').attr("content") ||
 					"";
-				let thumb =
-					$('meta[property="og:image"]').attr("content") ||
-					$('meta[name="twitter:image:src"]').attr("content") ||
-					$('link[rel="image_src"]').attr("href") ||
-					"";
 
 				if (preview.head.length) {
 					preview.head = preview.head.substr(0, 100);
@@ -98,6 +93,17 @@ function parseHtml(preview, res, client) {
 					preview.body = preview.body.substr(0, 300);
 				}
 
+				if (!Helper.config.prefetchStorage && Helper.config.disableMediaPreview) {
+					resolve(res);
+					return;
+				}
+
+				let thumb =
+					$('meta[property="og:image"]').attr("content") ||
+					$('meta[name="twitter:image:src"]').attr("content") ||
+					$('link[rel="image_src"]').attr("href") ||
+					"";
+
 				// Make sure thumbnail is a valid and absolute url
 				if (thumb.length) {
 					thumb = normalizeURL(thumb, preview.link) || "";
@@ -127,6 +133,10 @@ function parseHtml(preview, res, client) {
 
 function parseHtmlMedia($, preview, client) {
 	return new Promise((resolve, reject) => {
+		if (Helper.config.disableMediaPreview) {
+			reject();
+		}
+
 		let foundMedia = false;
 
 		["video", "audio"].forEach((type) => {
@@ -203,6 +213,10 @@ function parse(msg, chan, preview, res, client) {
 		case "image/jpg":
 		case "image/jpeg":
 		case "image/webp":
+			if (!Helper.config.prefetchStorage && Helper.config.disableMediaPreview) {
+				return removePreview(msg, preview);
+			}
+
 			if (res.size > Helper.config.prefetchMaxImageSize * 1024) {
 				preview.type = "error";
 				preview.error = "image-too-big";
@@ -228,6 +242,10 @@ function parse(msg, chan, preview, res, client) {
 				break;
 			}
 
+			if (Helper.config.disableMediaPreview) {
+				return removePreview(msg, preview);
+			}
+
 			preview.type = "audio";
 			preview.media = preview.link;
 			preview.mediaType = res.type;
@@ -241,6 +259,10 @@ function parse(msg, chan, preview, res, client) {
 				break;
 			}
 
+			if (Helper.config.disableMediaPreview) {
+				return removePreview(msg, preview);
+			}
+
 			preview.type = "video";
 			preview.media = preview.link;
 			preview.mediaType = res.type;

test/plugins/link.js

@@ -222,6 +222,70 @@ Vivamus bibendum vulputate tincidunt. Sed vitae ligula felis.`;
 		});
 	});
 
+	describe("test disableMediaPreview", function () {
+		beforeEach(function (done) {
+			Helper.config.disableMediaPreview = true;
+			done();
+		});
+		afterEach(function (done) {
+			Helper.config.disableMediaPreview = false;
+			done();
+		});
+		it("should ignore og:image if disableMediaPreview", function (done) {
+			const port = this.port;
+
+			app.get("/nonexistent-test-image.png", function () {
+				throw "Should not fetch image";
+			});
+
+			app.get("/thumb", function (req, res) {
+				res.send(
+					"<title>Google</title><meta property='og:image' content='http://localhost:" +
+						port +
+						"/nonexistent-test-image.png'>"
+				);
+			});
+			const message = this.irc.createMessage({
+				text: "http://localhost:" + port + "/thumb",
+			});
+
+			link(this.irc, this.network.channels[0], message);
+
+			this.irc.once("msg:preview", function (data) {
+				expect(data.preview.head).to.equal("Google");
+				expect(data.preview.type).to.equal("link");
+				expect(data.preview.thumb).to.equal("");
+				done();
+			});
+		});
+		it("should ignore og:video if disableMediaPreview", function (done) {
+			const port = this.port;
+
+			app.get("/nonexistent-video.mpr", function () {
+				throw "Should not fetch video";
+			});
+
+			app.get("/thumb", function (req, res) {
+				res.send(
+					"<title>Google</title><meta property='og:video:type' content='video/mp4'><meta property='og:video' content='http://localhost:" +
+						port +
+						"/nonexistent-video.mp4'>"
+				);
+			});
+			const message = this.irc.createMessage({
+				text: "http://localhost:" + port + "/thumb",
+			});
+
+			link(this.irc, this.network.channels[0], message);
+
+			this.irc.once("msg:preview", function (data) {
+				expect(data.preview.head).to.equal("Google");
+				expect(data.preview.type).to.equal("link");
+				done();
+			});
+		});
+	});
+
 	it("should find image_src", function (done) {
 		const port = this.port;
 		const message = this.irc.createMessage({