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75 lines
2.9 KiB
75 lines
2.9 KiB
import {tbind} from 'app/common/tbind';
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import {NextFunction, Request, RequestHandler, Response} from 'express';
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export type RequestWithTag = Request & {tag: string|null};
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/**
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*
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* Middleware to handle a /v/TAG/ prefix on urls.
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*
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*/
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export class TagChecker {
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// Use app.use(tagChecker.inspectTag) to strip /v/TAG/ from urls (if it is present).
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// If the tag is present and matches what is expected, then `tag` is set on the request.
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// If the tag is present but does not match what is expected, a 400 response is returned.
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// If the tag is absent, `tag` is not set on the request.
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public readonly inspectTag: RequestHandler = tbind(this._inspectTag, this);
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// Use app.get('/path', tagChecker.requireTag, ...) to serve something only if the tag was
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// present in the url. If the tag was not present, the route will not match and express will
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// look further.
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public readonly requireTag: RequestHandler = tbind(this._requireTag, this);
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// pass in the tag to expect.
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public constructor(public tag: string) {
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}
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// Like requireTag but for use wrapping other handlers in app.use().
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// Whatever it wraps will be skipped if that tag was not set.
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// See https://github.com/expressjs/express/issues/2591
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public withTag(handler: RequestHandler) {
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return function fn(req: Request, resp: Response, next: NextFunction) {
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if (!(req as RequestWithTag).tag) { return next(); }
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return handler(req, resp, next);
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};
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}
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// Removes tag from url if present.
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// Returns [remainder, tagInUrl, isMatch]
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private _removeTag(url: string): [string, string|null, boolean] {
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if (url.startsWith('/v/')) {
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const taggedUrl = url.match(/^\/v\/([a-zA-Z0-9.\-_]+)(\/.*)/);
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if (taggedUrl) {
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const tag = taggedUrl[1];
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// Turn off tag matching as we transition to serving
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// static resources from CDN. We don't have version-sensitive
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// routing, so under ordinary operation landing page html served
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// by one home server could have its assets served by another home server.
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// Once the CDN is active, those asset requests won't reach the home
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// servers. TODO: turn tag matching back on when tag mismatches
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// imply a bug.
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return [taggedUrl[2], tag, true /* tag === this.tag */];
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}
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}
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return [url, null, true];
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}
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private async _inspectTag(req: Request, resp: Response, next: NextFunction) {
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const [newUrl, urlTag, isOk] = this._removeTag(req.url);
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if (!isOk) {
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return resp.status(400).send({error: "Tag mismatch",
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expected: this.tag,
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received: urlTag});
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}
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req.url = newUrl;
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(req as RequestWithTag).tag = urlTag;
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return next();
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}
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private async _requireTag(req: Request, resp: Response, next: NextFunction) {
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if ((req as RequestWithTag).tag) { return next(); }
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return next('route');
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}
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}
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