[metrics-bugs] #33010 [Metrics/Exit Scanner]: Monitor cloudflare captcha rate: do a periodic onionperf-like query to a cloudflare-hosted static site

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#33010: Monitor cloudflare captcha rate: do a periodic onionperf-like query to a
cloudflare-hosted static site
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 Reporter:  arma                  |          Owner:  metrics-team
     Type:  task                  |         Status:  new
 Priority:  Medium                |      Milestone:
Component:  Metrics/Exit Scanner  |        Version:
 Severity:  Normal                |     Resolution:
 Keywords:  network-health        |  Actual Points:
Parent ID:                        |         Points:
 Reviewer:                        |        Sponsor:
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Comment (by cypherpunks):

 >One catch is that Cloudflare currently gives alt-svc headers in response
 to fetches from Tor addresses. So that means we need a web client that can
 follow alt-srv headers -- maybe we need a full Selenium like client?
 Tor Browser does not upgrade immediately, so that's not too much reason to
 use real web browser. However, Cloudflare is doing fingerprinting of TLS
 handshake Client Hello (cipher suites and group in tls 1.3) to tell real
 Tor Browser from spoofed. Must build curl from NSS and set correct headers
 and cipher suites to pass.

 Cloudflare have also different levels of protection, and some
 grandfathered protection levels have no Tor Browser whitelisting. Should
 test them all.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/33010#comment:5>
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