84 lines
3.2 KiB
Markdown
84 lines
3.2 KiB
Markdown
+++
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title = HTML over DNS: Serving Blog Content Over DNS
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date = 2021-08-15
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author = Jacob Kiers
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+++
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## What's up?
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You might not be able to see it immediately, but the content of this page is served over DNS.
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This works because of [DNS over HTTPS] for which there is an [API from Cloudflare].
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Comments at [Hacker News, apparently][HN].
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## How it works
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That API is used to load the contents of this page, essentially like this:
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```js
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fetch("https://cloudflare-dns.com/dns-query?ct=application/dns-json&type=TXT&name=post.hod.experiments.jacobkiers.net");
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```
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The content itself is served over DNS, using CoreDNS, with these contents:
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```js
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hod.experiments.jacobkiers.net.:53 {
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log
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auto hod.experiments.jacobkiers.net. {
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directory /etc/coredns/zones/
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reload 10s
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}
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}
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```
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This feeds into a zone file, which looks like this:
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```js
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$TTL 5m ; Default TTL
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@ IN SOA experiments.jacobkiers.net. postmaster.jacobkiers.net. (
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2021081612 ; serial
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1h ; slave refresh interval
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15m ; slave retry interval
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1w ; slave copy expire time
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1h ; NXDOMAIN cache time
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)
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$ORIGIN hod.experiments.jacobkiers.net.
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;
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; domain name servers
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;
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@ IN NS experiments.jacobkiers.net.
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;; START BLOG RECORDS
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; posts-2021-08-17-serving-blog-content-over-dns-md
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posts-2021-08-17-serving-blog-content-over-dns-md 60 IN TXT "t=text/markdown;c=3;h=2fd63f0f408ad1336283999d0487ced9;m=eyJ0aXRsZSI6IlNlcnZpbmcgYmxvZyBjb250ZW50IG92ZXIgRE5TIiwiZGF0ZSI6IjIwMjEtMDgtMTUiLCJhdXRob3IiOiJKYWNvYiBLaWVycyJ9"
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0.2fd63f0f408ad1336283999d0487ced9 60 IN TXT "WW91IG1pZ2h0IG5vdCBiZSBhYmxlIHRvIHNlZSBpdCBpbW1lZGlhdGVseSwgYnV0IHRoZSBjb250ZW50IG9mIHRoaXMgcGFnZSBpcyB2ZXJ2ZWQgb3ZlciBETlMuCgpUaGlzIHdvcmtzIGJlY2F1c2Ugb2YgdGhlIG5ldyBETlMtb3Zlci1IVFRQIHN1cHBvcnQsIHdoaWNoLCBhdCBsZWFzdCBhdCBDbG91ZGZsYXJlLCBhbHNvIGhhcy"
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1.2fd63f0f408ad1336283999d0487ced9 60 IN TXT "BhbiBBUEkuCgpUaGF0IEFQSSBpcyB1c2VkIHRvIGxvYWQgdGhlIGNvbnRlbnRzIG9mIHRoaXMgcGFnZSwgZXNzZW50aWFsbHkgbGlrZSB0aGlzOgoKYGBganMKZmV0Y2goImh0dHBzOi8vY2xvdWRmbGFyZS1kbnMuY29tL2Rucy1xdWVyeT9jdD1hcHBsaWNhdGlvbi9kbnMtanNvbiZ0eXBlPVRYVCZuYW1lPXBvc3QuaG9kLmV4cGVy"
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2.2fd63f0f408ad1336283999d0487ced9 60 IN TXT "aW1lbnRzLmphY29ia2llcnMubmV0Iik7CmBgYAoKUGxlYXNlIHNlZSB0aGUgW3NvdXJjZSBjb2RlXSBmb3IgdGhlIGRldGFpbHMgb2YgaG93IGl0IHdvcmtzLgoKW3NvdXJjZSBjb2RlXTogaHR0cHM6Ly9naXRodWIuY29tL2phY29ia2llcnMvaHRtbC1vdmVyLWRucwo="
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```
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These records are base64 encoded content, so when concatenated and decoded, they give the content of the posts.
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Please see the [source code] for the details.
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## FAQ
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### Why, though?
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In short: just because I could. It was one of those ideas I was wondering idly about, and I decided to just try it.
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### Has it any practical use?
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It is not intended to have any. Since DNS records are fairly small, serving images or something would quickly start
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consuming 100s of requests per second. I wouldn't want to do that to Cloudflare 😉
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It would be an interesting experiment to see how feasible that is.
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[source code]: https://github.com/jacobkiers/html-over-dns "Yes, the title is a pun..."
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[DNS over HTTPS]: https://en.wikipedia.org/wiki/DNS_over_HTTPS
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[API from Cloudflare]: https://developers.cloudflare.com/1.1.1.1/dns-over-https/json-format
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[HN]: https://news.ycombinator.com/item?id=28218406
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