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Ask HN: How to stop people using my RSS reader web app as a proxy for evil sites

3 points by shadowfaxRodeo ↗ HN
I'm building an RSS reader web app. It takes a list of urls for feeds, and returns links to items in the feed.

Due to CORS, the requests have to go through a server. The server also parses the rss feed and just returns a few bits of relevant information. The url, title, and date of the entries.

If I allow anyone to use my server to fetch any RSS feed they want.

What can I do to stop someone nefarious using my server as a proxy to build a list of links to evil/illegal things?

Other than building a database of trustworthy sites, which i'm not willing to do, I can't think of a solution.

4 comments

[ 6.0 ms ] story [ 22.9 ms ] thread
phillipseamore
Usually the RSS feed is on the same domain, so you could simply whitelist automatically. If a user adds example.com/rss you'd add example.com to the whitelist. If you expect any kind of traffic you'd probably be refreshing the RSS feeds server-side on a schedule. You could then change all the URL's to signed URL's to use with your proxy (e.g. nginx securelink, ngx_http_hmac_secure_link_module and multiple other modules for nginx).
shadowfaxRodeo
Thank you. I don't fully understand your answer. But i'll do some research until I do.
rukshn
Yes the best thing is to create a list of blacklisted domains, and don’t allow users to add a blacklisted domain.

Btw is rss a thing now? I was having an idea of creating an rss reader, but gave up because rss is almost dead,

Shoot me an email love to hear from you, arkruka@gmail.com

susam
> Btw is rss a thing now? I was having an idea of creating an rss reader, but gave up because rss is almost dead

I provide an RSS feed for my blog at https://susam.in/ . From my access.log, I see there is a decent number of subscribers to my feed. Here is the data I could pull from it:

  Feedly          56 subscribers
  Inoreader       17 subscribers
  Feedbin          6 subscribers
  NewsBlur         4 subscribers
  The Old Reader   3 subscribers
  BazQux           2 subscribers
  WordPress        2 subscribers
  ------------------------------
  Total           90 subscribers
I get about 4000-6000 hits to my website on a normal day. It increases by 5 to 10 times if a post hits the HN front page but I will talk about ordinary day traffic only here. From the HTTP referer (sic) information in the logs I can see that about 30-50 of those hits have a feed reader in the referer field, that is, at least 0.5%-0.75% of the total hits are coming from users who clicked on a blog post link in their feed reader and landed on the website. It is a very small percentage but 30-50 hits per day from users consuming the feed and 90 subscribers to the feed are reasons good enough to keep the feed alive.