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  3. Has anybody thought about modelling #activitypub with a tool like https://alloytools.org/book.htmlto find potential exploits?

Has anybody thought about modelling #activitypub with a tool like https://alloytools.org/book.htmlto find potential exploits?

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activitypub
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  • profpatsch@mastodon.xyzP This user is from outside of this forum
    profpatsch@mastodon.xyzP This user is from outside of this forum
    profpatsch@mastodon.xyz
    wrote last edited by
    #1

    Has anybody thought about modelling #activitypub with a tool like https://alloytools.org/book.html
    to find potential exploits? Thinking about the spec it’s missing any algorithms for authorization, but I already found a couple of edge-cases that make a server DoSssable or give an attacker the ability to spoof messages …

    silverpill@mitra.socialS 1 Reply Last reply
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    • tag-activitypub@relay.fedi.buzzT tag-activitypub@relay.fedi.buzz shared this topic
    • profpatsch@mastodon.xyzP profpatsch@mastodon.xyz

      Has anybody thought about modelling #activitypub with a tool like https://alloytools.org/book.html
      to find potential exploits? Thinking about the spec it’s missing any algorithms for authorization, but I already found a couple of edge-cases that make a server DoSssable or give an attacker the ability to spoof messages …

      silverpill@mitra.socialS This user is from outside of this forum
      silverpill@mitra.socialS This user is from outside of this forum
      silverpill@mitra.social
      wrote last edited by
      #2

      @Profpatsch I don't know Alloy, but I tried to analyze how authorization should be done in ActivityPub. The result is this document:

      https://fediverse.codeberg.page/fep/fep/fe34/

      profpatsch@mastodon.xyzP 1 Reply Last reply
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      • silverpill@mitra.socialS silverpill@mitra.social

        @Profpatsch I don't know Alloy, but I tried to analyze how authorization should be done in ActivityPub. The result is this document:

        https://fediverse.codeberg.page/fep/fep/fe34/

        profpatsch@mastodon.xyzP This user is from outside of this forum
        profpatsch@mastodon.xyzP This user is from outside of this forum
        profpatsch@mastodon.xyz
        wrote last edited by
        #3

        @silverpill does the http signature not contain the domain of the requesting server and if yes, can't it be used to compare origins after the signature check?

        silverpill@mitra.socialS 1 Reply Last reply
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        • profpatsch@mastodon.xyzP profpatsch@mastodon.xyz

          @silverpill does the http signature not contain the domain of the requesting server and if yes, can't it be used to compare origins after the signature check?

          silverpill@mitra.socialS This user is from outside of this forum
          silverpill@mitra.socialS This user is from outside of this forum
          silverpill@mitra.social
          wrote last edited by
          #4

          @Profpatsch Yes, the signature contains key ID, from which you can obtain actor ID and perform origin / ownership checks.

          profpatsch@mastodon.xyzP 1 Reply Last reply
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          • silverpill@mitra.socialS silverpill@mitra.social

            @Profpatsch Yes, the signature contains key ID, from which you can obtain actor ID and perform origin / ownership checks.

            profpatsch@mastodon.xyzP This user is from outside of this forum
            profpatsch@mastodon.xyzP This user is from outside of this forum
            profpatsch@mastodon.xyz
            wrote last edited by
            #5

            @silverpill I mean ideally we already have a cache from the corresponding server key to its origin, so we don’t have to do a https resolution on every incoming message

            silverpill@mitra.socialS 1 Reply Last reply
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            • profpatsch@mastodon.xyzP profpatsch@mastodon.xyz

              @silverpill I mean ideally we already have a cache from the corresponding server key to its origin, so we don’t have to do a https resolution on every incoming message

              silverpill@mitra.socialS This user is from outside of this forum
              silverpill@mitra.socialS This user is from outside of this forum
              silverpill@mitra.social
              wrote last edited by
              #6

              @Profpatsch I believe most implementations do that. My server re-fetches a key only if the cached key is 1 day old, for example.

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