Yep, essentially the botPolicy.yaml there could be a collectively developed anubis config, based on what works best.

Sure. I have found that the default botPolicy works fine for blocking the AI bots, but blocks federation.

At the reverse proxy level:

if ($request_method = POST) {
    proxy_pass http://nodebb; 
}

Because Anubis can't filter by HTTP method, unless I am mistaken. This just broadly allows all incoming activities. If you want to get specific, limit it to your shared inbox or individual user inboxes via regular expression or something. I didn't find that it was necessary.

As for botPolicies.yaml

  # Allow /inbox
  - name: allow-ap-headers
    headers_regex:
      Accept: application/ld\+json; profile="https://www.w3.org/ns/activitystreams"
      Accept: application/activity\+json
    action: ALLOW

  - name: allow-assets
    path_regex: /assets
    action: ALLOW

The former allows those specific AP headers (it is naive, some AP impls. send slight variations of those two headers.

The latter allows our uploads.

Lemmy has a separated UI and backend hosted on different ports, so its trivial for us to just only use anubis for the front end. We couldn't put it in front of everything due to apps also.

This is the botPolicy.yaml that we use on slrpnk.net :

bots:
  - name: known-crawler
    action: CHALLENGE
    expression:
      # https://anubis.techaro.lol/docs/admin/configuration/expressions
      all:
        # Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/125.0.0.0 Safari/537.36
        - userAgent.contains("Macintosh; Intel Mac") && userAgent.contains("Chrome/125.0.0.0") # very old chrome?
        - missingHeader(headers, "Sec-Ch-Ua") # a valid chrome has this header
    challenge:
      difficulty: 6
      algorithm: slow

    # Assert behaviour that only genuine browsers display.
    # This ensures that Chrome or Firefox versions
  - name: realistic-browser-catchall
    expression:
      all:
        - '"User-Agent" in headers'
        - '( userAgent.contains("Firefox") ) || ( userAgent.contains("Chrome") ) || ( userAgent.contains("Safari") )'
        - '"Accept" in headers'
        - '"Sec-Fetch-Dest" in headers'
        - '"Sec-Fetch-Mode" in headers'
        - '"Sec-Fetch-Site" in headers'
        - '"Accept-Encoding" in headers'
        - '( headers["Accept-Encoding"].contains("zstd") || headers["Accept-Encoding"].contains("br") )'
        - '"Accept-Language" in headers'
    action: CHALLENGE
    challenge:
      difficulty: 2
      algorithm: fast

  - name: generic-browser
    user_agent_regex: (?i:mozilla|opera)
    action: CHALLENGE
    challenge:
      difficulty: 4
      algorithm: fast

status_codes:
  CHALLENGE: 202
  DENY: 406

dnsbl: false

#store:
#  backend: valkey
#  parameters:
#    url: redis://valkey-primary:6379/0

I think I just took it over from Codeberg.org back from when they still used Anubis. Nothing really relevant to Lemmy specifically and it is only in front of the frontends, not the s2s federation API.

It seems though like there are some crawlers that use 3rd party hosted alternative frontends to crawl (unintentionally?) through the federation API, so something in front of that would be useful I guess.

Well behaved bots should see the origin in the headers and only crawl those.

Not Lemmy specific, but I wanted to set up Anubis in a setup where I have one reverse proxy (nginx) handling many different domains. Last time I looked, it seemed to need one Anubis instance per domain. Is that still the case? Goal was to have a single Anubis instance and route all through it

I'm not an expert, but I think the fact that you need to set a TARGET in anubis, IE, where does anubis send you after passing it, means that you do need separate anubis's for each site.

You could probably put Anubis in front of your reverse-proxy, but then you need something else in front of it that handles TLS certificates. So maybe something like this: HAProxy->Anubis->Nginx.

i think feddit.org and lemmy.dbzer0.com both use it

in feddit.org's case, the anubis loading screen displays for waaay too long. i've told the feddit.org admins repeatedly but got no response.

i'm not sure whether lemmy.dbzer0.com still uses it, but i think i remember seeing the loading screen there too. maybe they just reduced the loading time so much that i can't see it anymore.

We're actually using haphash, not anubis