Returning objects in a collection vs. IDs
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@grishka @silverpill @julian @technical-discussion point being, you can completely upend a lot of fedi applications' security models with just nginx and curl and subdirectories.
@trwnh @silverpill @julian @technical-discussion I still wouldn't call that "upending". The actor objects — that reside on that server — contain public keys, which the entire security model of the entire fediverse relies on. So it follows, then, that since a server can serve any arbitrary public key for any of its actors, and the rest of the fediverse will unquestionably trust it, it can also be trusted with any other objects on the same domain.
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@trwnh @silverpill @julian @technical-discussion I still wouldn't call that "upending". The actor objects — that reside on that server — contain public keys, which the entire security model of the entire fediverse relies on. So it follows, then, that since a server can serve any arbitrary public key for any of its actors, and the rest of the fediverse will unquestionably trust it, it can also be trusted with any other objects on the same domain.
@grishka @silverpill @julian @technical-discussion the key can be on a different keyserver
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@grishka @silverpill @julian @technical-discussion the key can be on a different keyserver
@trwnh @silverpill @julian @technical-discussion it can in theory but no software currently in existence supports that
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@trwnh @silverpill @julian @technical-discussion it can in theory but no software currently in existence supports that
@trwnh @silverpill @julian @technical-discussion but even if, the actor object is still the ultimate source of truth as it's the one which contains the key ID
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@trwnh @silverpill @julian @technical-discussion but even if, the actor object is still the ultimate source of truth as it's the one which contains the key ID
@grishka @silverpill @julian @technical-discussion true but we are talking about mistakes. like taking the origin of the keyId on the http sig instead of following the link to the owner/controller. such assumptions might be true for monoliths, but not everything is a monolith
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Web Annotations has a neat solution here which is prefers representation, which allows the requestor to ask for minimal or full representation (i.e., just the IDs or the full representations)
You'd still likely want to gate that on authorization
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@silverpill @julian @technical-discussion ideally you would traverse everything and replace anything you don't understand with "id" references.
But anyway, I feel like we're getting too carried away about a very niche aspect of the whole thing. Almost like on that SocialHub forum.
In my own AP extensions I always just act like C2S doesn't exist because I've never seen it used in practice, and it's wildly impractical to use anyway.
@grishka I am developing a client application where this is a real concern.
But I agree that in general, originating servers are responsible for verification of client data. This part of FEP-fe34 will likely be revised in the future. -
@silverpill @julian @technical-discussion ideally you would traverse everything and replace anything you don't understand with "id" references.
But anyway, I feel like we're getting too carried away about a very niche aspect of the whole thing. Almost like on that SocialHub forum.
In my own AP extensions I always just act like C2S doesn't exist because I've never seen it used in practice, and it's wildly impractical to use anyway.
> and it's wildly impractical to use anyway.
@grishka shush, you! 🤫
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@grishka I am developing a client application where this is a real concern.
But I agree that in general, originating servers are responsible for verification of client data. This part of FEP-fe34 will likely be revised in the future.@silverpill do you mean that the "malicious" attachment is not a facsimile of an actual note produced by that actor, but a forgery?
In these cases, I'll agree with
@grishka that some validation based on the ID should be necessary.For embedded object attachments on the other hand (like mastodon produces), probably the validation needs to check that attributedTo corresponds to the one of the parent object or missing.
Interesting corner case.
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@silverpill do you mean that the "malicious" attachment is not a facsimile of an actual note produced by that actor, but a forgery?
In these cases, I'll agree with
@grishka that some validation based on the ID should be necessary.For embedded object attachments on the other hand (like mastodon produces), probably the validation needs to check that attributedTo corresponds to the one of the parent object or missing.
Interesting corner case.
@mariusor Yes, a forged note. I've come up with a more realistic example:
{ "type": "Create", "id": "https://social.example/activity/345", "actor": "https://social.example/alice" "object": { "type": "Note", "id": "https://social.example/note/123", "attributedTo": "https://social.example/alice", "content": "This is just a note, nothing to see here", "replies": { "type": "Collection", "id": "https://social.example/note/123/replies", "items": [{ "type": Note", "id": "https://social.example/note/987", "attributedTo": "https://social.example/bob", "inReplyTo": "https://social.example/note/123", "content": "Ha ha ha... Yes!" }] } } }If the originating server doesn't check the embedded
repliescollection, a recipient that processesrepliesand trusts same-origin embeddings unconditionally may end up trusting the forged note.What we can do?
- Sender: find all embedded objects with local
idand reject activity if they are not known.
- Recipient: trust embedded object only if the wrapping object has the same owner.I think the second solution is much easier to implement. It reduces the utility of embedding in the use case described by @julian, but to be honest I doubt that embedding significantly reduces the number of required HTTP requests in that case.
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@mariusor Yes, a forged note. I've come up with a more realistic example:
{ "type": "Create", "id": "https://social.example/activity/345", "actor": "https://social.example/alice" "object": { "type": "Note", "id": "https://social.example/note/123", "attributedTo": "https://social.example/alice", "content": "This is just a note, nothing to see here", "replies": { "type": "Collection", "id": "https://social.example/note/123/replies", "items": [{ "type": Note", "id": "https://social.example/note/987", "attributedTo": "https://social.example/bob", "inReplyTo": "https://social.example/note/123", "content": "Ha ha ha... Yes!" }] } } }If the originating server doesn't check the embedded
repliescollection, a recipient that processesrepliesand trusts same-origin embeddings unconditionally may end up trusting the forged note.What we can do?
- Sender: find all embedded objects with local
idand reject activity if they are not known.
- Recipient: trust embedded object only if the wrapping object has the same owner.I think the second solution is much easier to implement. It reduces the utility of embedding in the use case described by @julian, but to be honest I doubt that embedding significantly reduces the number of required HTTP requests in that case.
> - Recipient: trust embedded object only if the wrapping object has the same owner.
@silverpill no, dereference object and use that instead. The canonical version of an object is the one retrieved from the originating service.
Mastodon has popularised this behaviour where embedding collections (like your replies) is done by servers in the name of "optimizing" for request counts. But this introduces issues and personally I think it's a "code smell" for ActivityPub. Embedding should be restricted to anonymous objects. When an ID exists it should be used most of the time.
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> - Recipient: trust embedded object only if the wrapping object has the same owner.
@silverpill no, dereference object and use that instead. The canonical version of an object is the one retrieved from the originating service.
Mastodon has popularised this behaviour where embedding collections (like your replies) is done by servers in the name of "optimizing" for request counts. But this introduces issues and personally I think it's a "code smell" for ActivityPub. Embedding should be restricted to anonymous objects. When an ID exists it should be used most of the time.
mariusor@metalhead.club silverpill@mitra.social C2S brings with it a whole other rat's nest of security concerns.
In an S2S context same origin content ought to be trusted as having been verified. I'd argue a server blindly reflecting received AP content is a vulnerability.
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@julian I'm not sure what "blindly reflecting" means, but it's at most as vulnerable as using iframes and way less than trusting CDN scripts.
The way GoActivityPub uses C2S is through clients that validate and sanitize content that they serve back to users, or store in a persistence layer.
Personally I don't understand why it would make it different than S2S?
Are you thinking about C2S from a JavaScript client perspective only?
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> - Recipient: trust embedded object only if the wrapping object has the same owner.
@silverpill no, dereference object and use that instead. The canonical version of an object is the one retrieved from the originating service.
Mastodon has popularised this behaviour where embedding collections (like your replies) is done by servers in the name of "optimizing" for request counts. But this introduces issues and personally I think it's a "code smell" for ActivityPub. Embedding should be restricted to anonymous objects. When an ID exists it should be used most of the time.
@mariusor This is basically what my FEP currently recommends: you can trust embedded anonymous objects, fragments and
objectofCreate. Everything else should be authenticated using a different method (e.g. fetched from origin). -
@silverpill oh, I see. I must have missed the context for the discussion, sorry. :)
@technical-discussion @julian @grishka
Gli ultimi otto messaggi ricevuti dalla Federazione
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@jon I'm using that, and Bluesky pulls out an image, but the aspect ratio of that image appears to be all wrong, so Bsky crops it in weird ways. What I'm looking for is 1) a bluesky-specific OpenGraph tag -- like there is one for Twitter and 2) just what the heck is the aspect ratio supposed to be on Bsky?
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@rimu It looks like display_name was changed to name in Lemmy: https://github.com/LemmyNet/lemmy/pull/5976
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Open Graph is all you need.
https://coywolf.com/guides/open-graph-twitter-card-image-optimization/
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I'm looking for a guide on how to specify images in HTML pages so that Mastodon and Bluesky posts linking to those pages have nicely formatted images in them.
Twitter has <meta name="twitter:image" etc ... what's the equivalent for Mastodon and Bluesky? And Threads? And what are the best image sizes?
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julian@fietkau.social IIRC I think Rimu wrote an FEP for it but it was not submitted through the official FEP processes.
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Oh hey @rimu, what's the story behind the color attributes? Does other software besides PieFed use them, is there an FEP?
It's way down on my to do list, but I've still got a brain cell or two dedicated to declarative federated profile accent colors. @hollo has configurable profile colors, but doesn't federate them yet AFAIK.
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Hi rimu@piefed.social did Piefed.social update recently to include community tags? I recall this was announced awhile back but it only just started breaking on NodeBB.
"tag": [ { "background_color": "#99c1f1", "blur_images": null, "display_name": "Feature request", "id": "https://piefed.social/c/piefed_meta/tag/198", "text_color": "#000000", "type": "lemmy:CommunityTag" }, ... ]I should point out that there's nothing wrong with the JSON. NodeBB's naive logic just expected every object in tag to have a name property, which your community tags do not, so things exploded :cold_sweat:
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@silverpill oh, I see. I must have missed the context for the discussion, sorry. :)
@technical-discussion @julian @grishka
