I try to implement an #activitypub server in #Rust, have problems talking to #mastodon and would appreciate some help.

I try to implement an #activitypub server in #Rust, have problems talking to #mastodon and would appreciate some help.

I try to send a follow action to Mastodon. The request is - as far as I can tell - signed according to https://docs.joinmastodon.org/spec/security/

The "keyId" of the signatrue is "https://pub.saar.social/user/achim/key". Mastodon calls this url as expected and my server returns: [...]

[...]

{
"@context":["https://www.w3.org/ns/activitystreams","https://w3id.org/security/v1"],
"id":"https://pub.saar.social/user/achim/key",
"type":"Key",
"publicKeyPem":"-----BEGIN PUBLIC KEY-----\nMIIBI[...]IDAQAB\n-----END PUBLIC KEY-----\n",
"owner":"https://pub.saar.social/user/achim"
}

But my follow http call gets this back from Mastodon:

{"error":"Unable to fetch key JSON at https://pub.saar.social/user/achim/key"}

Can somebody give me a hint how to figure out what the problem is?

@achim
Silly question but I tend to forget it every time I haven't done http requests for a while:
Did you set your request header "Content-Type: application/json" ?

@achim you can try to debug with https://activitypub.academy

It can display the activity exchanges that happen between the test account you create there and your instance.

@achim I don't know about Mastodon, but here are some general tips:

- Your actor is served with content-type application/json, but it should be application/ld+json; profile="https://www.w3.org/ns/activitystreams"
- It's better to embed the key in your actor document and identify it with a fragment ID. This is more widely supported than standalone keys.

@silverpill Thanks! Mitra looks very interesting. I'll have a look and will probably pop up in your Matrix channel. I was not aware that there is a maintained ActivityPub project in Rust.

@achim Lemmy is also in Rust! And there are two Rust libraries:

- https://docs.rs/activitypub_federation/latest/activitypub_federation/ (from Lemmy devs)
- https://docs.rs/apx_sdk/latest/apx_sdk/ (this one is developed by me)