Challenges Operators can choose to serve a challenge to incoming requests or client, depending on conditions or other rules. Challenges can be transparent (not shown to user, depends on backend or other logic), non-JavaScript (challenges common browser properties), or custom JavaScript (from Proof of Work to fingerprinting or Captcha is supported) The following examples are defined in policy snippets and are ready to use. Challenges can be redefined or new ones entirely can be added with different configuration. Transparent http Verify incoming requests against a specified backend to allow the user through. Cookies and some other headers are passed. For example, this allows verifying the user cookies against the backend to have the user skip all other challenges. Most request headers (including cookies / authorization) and other general headers from go-away are sent, some additional ones are set, of note: Header Description X-Away-Method Original request HTTP Method X-Away-Host Original request HTTP Host X-Away-Path Original request URL Path X-Away-Query Original request URL Query Example on Forgejo, checks that current user is authenticated: challenges : http-cookie-check : runtime : http parameters : http-url : http://forgejo:3000/user/stopwatches # http-url: http://forgejo:3000/repo/search # http-url: http://forgejo:3000/notifications/new http-method : GET http-cookie : i_like_gitea http-code : 200 verify-probability : 0.1 preload-link Requires HTTP/2+ response parsing and logic, silent challenge (does not display a challenge page). Browsers that support 103 Early Hints are indicated to fetch a CSS resource via Link preload that solves the challenge. The server waits until solved or defined timeout, then continues on other challenges if failed. Configured default is 2 seconds. Example: challenges : preload-link : condition : '"Sec-Fetch-Mode" in headers && headers["Sec-Fetch-Mode"] == "navigate"' runtime : "preload-link" parameters : preload-early-hint-deadline : 2s dnsbl You can configure a DNSBL (Domain Name System blocklist) to be queried. This allows you to serve harder or different challenges to higher risk clients, or block them from specific sections. Only rules that match a DNSBL challenge will cause a query to be sent, meaning the bulk of requests will not be sent to this service upstream. Results will be temporarily cached. By default, DroneBL is used. Example challenge definition and rule: challenges : dnsbl : runtime : dnsbl parameters : # dnsbl-host: "dnsbl.dronebl.org" dnsbl-decay : 1h dnsbl-timeout : 1s rules : # check DNSBL and serve harder challenges - name : undesired-dnsbl action : check settings : challenges : [ dnsbl] # if DNSBL fails, check additional challenges fail : check fail-settings : challenges : [ js-pow-sha256] Non-JavaScript cookie Requires HTTP parsing and a Cookie Jar, silent challenge (does not display a challenge page unless failed). Serves the client with a Set-Cookie that solves the challenge, and redirects it back to the same page. Browser must present the cookie to load. Several tools implement this, but usually not mass scrapers. Example: challenges : cookie : runtime : "cookie" refresh Requires HTTP response parsing and logic, displays challenge site instantly. refresh-via: header Have the browser solve the challenge by following the URL listed on HTTP Refresh instantly. Example: challenges : header-refresh : runtime : "refresh" parameters : refresh-via : "header" Have the browser solve the challenge by following the URL listed on HTML tag instantly. Equivalent to above. Example: challenges : header-refresh : runtime : "refresh" parameters : refresh-via : "meta" resource-load Requires HTTP and HTML response parsing and logic, displays challenge site. Servers a challenge page with a linked resource that is loaded by the browser, which solves the challenge. Page refreshes a few seconds later via Refresh. Example: challenges : resource-load : runtime : "resource-load" Custom JavaScript refresh refresh-via: javascript Have the browser solve the challenge by following the URL listed on a