90 lines
2.9 KiB
TypeScript
90 lines
2.9 KiB
TypeScript
/**
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* The link preview routes.
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*
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* - `GET /api/preview?url=` — signed in. Answers the preview of a link, and
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* whether its page could be reached.
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* - `GET /api/proxy-image?url=` — public. Serves a remote raster image through
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* this site; 400 when it isn't one, 502 when its host can't be reached.
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*
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* @module
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*/
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import { Router } from "@oak/oak";
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import { isValidHttpUrl } from "../remote/fetch.ts";
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import { fetchProxiedImage } from "../remote/image-proxy.ts";
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import { tryFetchRichContent } from "../services/rich-content-service.ts";
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import {
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APIErrorCode,
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type APIFailure,
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type APIResponse,
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} from "../../shared/api.ts";
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import type { LinkPreview } from "../../shared/dump.ts";
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import { authMiddleware } from "../middleware/auth.ts";
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/** The router serving the endpoints the module doc lists. */
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const previewRouter: Router = new Router();
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// Signed-in only: it's the create form's preview, and an open one lets anyone
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// use the server to fetch pages for them.
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previewRouter.get("/api/preview", authMiddleware, async (ctx) => {
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const url = ctx.request.url.searchParams.get("url") ?? "";
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if (!isValidHttpUrl(url)) {
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const responseBody: APIFailure = {
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success: false,
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error: { code: APIErrorCode.VALIDATION_ERROR, message: "Invalid URL" },
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};
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ctx.response.status = 400;
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ctx.response.body = responseBody;
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return;
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}
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// `reached` is reported separately because a failed fetch still yields a
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// usable stub (hostname only). Without the flag the create form cannot tell
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// "this page has no preview" from "this link is dead", and shows the same
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// bare card for both.
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const { ok, content } = await tryFetchRichContent(url);
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const responseBody: APIResponse<LinkPreview> = {
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success: true,
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data: { reached: ok, richContent: content ?? null },
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};
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ctx.response.body = responseBody;
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});
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/** Answers with a proxied image, sandboxed so it can't run as a document. */
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function sendImage(
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ctx: { response: { headers: Headers; body?: unknown } },
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bytes: Uint8Array,
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contentType: string,
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): void {
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ctx.response.headers.set("Content-Type", contentType);
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ctx.response.headers.set("X-Content-Type-Options", "nosniff");
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ctx.response.headers.set(
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"Content-Security-Policy",
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"sandbox; default-src 'none'",
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);
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ctx.response.headers.set("Cache-Control", "public, max-age=86400");
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ctx.response.body = bytes;
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}
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// Proxies an external image through the server so HTTP thumbnail URLs don't
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// trigger mixed-content blocks when the frontend is served over HTTPS.
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previewRouter.get("/api/proxy-image", async (ctx) => {
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const url = ctx.request.url.searchParams.get("url") ?? "";
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if (!isValidHttpUrl(url)) {
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ctx.response.status = 400;
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return;
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}
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try {
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const image = await fetchProxiedImage(url);
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if (!image) {
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ctx.response.status = 400;
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return;
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}
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sendImage(ctx, image.bytes, image.contentType);
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} catch {
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ctx.response.status = 502;
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}
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});
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export default previewRouter;
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