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42 lines
2.3 KiB
Markdown
Executable File
42 lines
2.3 KiB
Markdown
Executable File
# Anti-Censorship Solution based on PAC-Script
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## Censorship in Russia
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Censorship in Russia plagues the Freedoms of
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[Information](https://en.wikipedia.org/wiki/Freedom_of_information) and [Speech](https://en.wikipedia.org/wiki/Freedom_of_speech),
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slowly building analogue of [China Golden Shield](https://en.wikipedia.org/wiki/Golden_Shield_Project).
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For good or bad, it blocks
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[Main Kampf](https://en.wikipedia.org/wiki/Mein_Kampf),
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[lolicon](https://en.wikipedia.org/wiki/Lolicon) (rearly distinguishing from hentai) and
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[critics of Putin](http://www.reuters.com/article/2014/03/13/us-russia-internet-idUSBREA2C21L20140313).
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Looking at how Russian government [distorts TV](https://therussianreader.wordpress.com/2015/11/22/russian-truckers-strike-dagestan/) and blocks Internet, I decided to write an Anti-Censorship extension for Chomium.
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I believe __the freedom of information is a virtue and important information mustn't be blocked based on political or other subjective views__.
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## Task Technical Formulation
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You have a list of blocked domains.
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Per each outcoming request you have to check whether host is a subdomain of the blocked domains.
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If host is blocked, you have serve it via proxy.
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[PAC (proxy auto-config)](https://en.wikipedia.org/wiki/Proxy_auto-config) is executed on each request.
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If it returns `PROXY address` to the browser then proxy is used, otherwise it returns `DIRECT`.
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## `Is_subdomain_of( host, blocked_hosts )`
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You have check `host belongs to subdomains of the blocked hosts` very fast.
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This check is executed on each request. You should watch memeory consumption also.
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The naive solution is to keep array of blocked ips and check if the host resolves to one of the ips.
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You may do it with `indexOf`, binary search, etc.
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The shortcoming of every ip solution is that some providers resolve blocked hosts to wrong ips, so we eventually need list of hosts.
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* __IPs indexOf__ – Blocked IP is search by `indexOf`
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* __IPs binary__ – Blocked IP is search by binary search. For some reason miss time slightly increased.
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* __IPs switch__ – Simply `switch(Blocked_IP) { case1: ... caseN: return true }`. Works even better than binary search. Magic.
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* __Hosts switch__ – Radix trie built on `switch`. Comparable to __IPs switch__.
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