[bug] Avoid reliance on a dead JSON-LD namespace link

[MrPetovan]

See friendica/friendica#10740

If mastodon/joinmastodon#148 doesn't get addressed, there is another way to prevent a remote lookup to a dead namespace link which can break federation.

Instead of just

"@context": [
    "http://joinmastodon.org/ns",
    "https://w3id.org/security/v1",
    "https://www.w3.org/ns/activitystreams"
  ],

Safe interoperability solution

you can bring the whole namespace definition in the context array like this:

"@context": [
        "https://www.w3.org/ns/activitystreams",
        "https://w3id.org/security/v1",
        {
            "manuallyApprovesFollowers": "as:manuallyApprovesFollowers",
            "toot": "http://joinmastodon.org/ns#",
            "featured": {
                "@id": "toot:featured",
                "@type": "@id"
            },
            "featuredTags": {
                "@id": "toot:featuredTags",
                "@type": "@id"
            },
            "alsoKnownAs": {
                "@id": "as:alsoKnownAs",
                "@type": "@id"
            },
            "movedTo": {
                "@id": "as:movedTo",
                "@type": "@id"
            },
            "schema": "http://schema.org#",
            "PropertyValue": "schema:PropertyValue",
            "value": "schema:value",
            "IdentityProof": "toot:IdentityProof",
            "discoverable": "toot:discoverable",
            "Device": "toot:Device",
            "Ed25519Signature": "toot:Ed25519Signature",
            "Ed25519Key": "toot:Ed25519Key",
            "Curve25519Key": "toot:Curve25519Key",
            "EncryptedMessage": "toot:EncryptedMessage",
            "publicKeyBase64": "toot:publicKeyBase64",
            "deviceId": "toot:deviceId",
            "claim": {
                "@type": "@id",
                "@id": "toot:claim"
            },
            "fingerprintKey": {
                "@type": "@id",
                "@id": "toot:fingerprintKey"
            },
            "identityKey": {
                "@type": "@id",
                "@id": "toot:identityKey"
            },
            "devices": {
                "@type": "@id",
                "@id": "toot:devices"
            },
            "messageFranking": "toot:messageFranking",
            "messageType": "toot:messageType",
            "cipherText": "toot:cipherText",
            "suspended": "toot:suspended",
            "focalPoint": {
                "@container": "@list",
                "@id": "toot:focalPoint"
            }
        }
    ],

Solution requiring JSON-LD compacting on the receiving end

If this is too verbose for you in every single outgoing message, you can instead declare your namespace like this:

"@context": [
    {
        "toot": "http://joinmastodon.org/ns"
    },
    "https://w3id.org/security/v1",
    "https://www.w3.org/ns/activitystreams"
  ],

And update every key listed in the above namespace to the corresponding value. "discoverable": false would become "toot:discoverable": false for example. I do not have more information on the more complex declarations but I assume it works the same, just by replacing the key by the @id value.

Thanks to @annando for the technical details.

[tsmethurst]

Thanks for the investigation :) I'll bring this up with the go-fed library dev and see what he thinks

[annando]

Transmitting something with "toot:discoverable": false wouldf work with Friendica on the remote side since we compact the received data. But many other systems don't do so. So it is better to adress every used parameter of a non standard namespace in the context.

[MrPetovan]

Thanks for the investigation :) I'll bring this up with the go-fed library dev and see what he thinks

I submitted this and I can ping CJ about it: go-fed/activity#152

[tsmethurst]

causes #169