wabowabo's blog

By wabowabo, history, 15 months ago, In English

Hello All!

When I try to access codeforces.com, I get a 403 error.

This is the response for codeforces.com/

<html><body>Redirecting... Please, wait.<script type="text/javascript" src="/aes.min.js" ></script><script>function toNumbers(d){var e=[];d.replace(/(..)/g,function(d){e.push(parseInt(d,16))});return e}function toHex(){for(var d=[],d=1==arguments.length&&arguments[0].constructor==Array?arguments[0]:arguments,e="",f=0;f<d.length;f++)e+=(16>d[f]?"0":"")+d[f].toString(16);return e.toLowerCase()}var a=toNumbers("e9ee4b03c1d0822987185d27bca23378"),b=toNumbers("188fafdbe0f87ef0fc2810d5b3e34705"),c=toNumbers("f7480ad2e21e5dca78cdb18dade0a3a1");document.cookie="RCPC="+toHex(slowAES.decrypt(c,2,a,b))+"; expires=Thu, 31-Dec-37 23:55:55 GMT; path=/";document.location.href="https://codeforces.com/?f0a28=1";</script></body></html>

This is the curl representation of the request for the above response (for the redirect):

curl 'https://codeforces.com/?f0a28=1' -H 'User-Agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:78.0) Gecko/20100101 Firefox/78.0' -H 'Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8' -H 'Accept-Language: en-US,en;q=0.5' --compressed -H 'Connection: keep-alive' -H 'Referer: https://codeforces.com/' -H 'Cookie: RCPC=c2c90c250d2e9dc04517bdc72fe23d' -H 'Upgrade-Insecure-Requests: 1' -H 'TE: Trailers'

I verified that the RCPC request matches the AES parameters in the response by testing the AES parameters on a different system.

I tried changing browsers and resetting cache for codeforces.com to no avail.

After changing IP addresses, I could access codeforces.com successfully, so I suspect my IP address has been blocked.

I would appreciate any help, MikeMirzayanov or anyone.

Thanks!

UPD: A very kind codeforces user by the name of prophet_ has solved the issue by stating that I have to change my RCPC token! His solution is described here: https://codeforces.com/blog/entry/80070.

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