[foobiekr]

Very much so. Pretty much all of these protocols are simplifications of asn1 and in some cases (like protobuf) there are a handful of things that got lost because the wire formats didn’t have them as they didn’t need them. A schema indicator being the single biggest flaw in protobuf.

[orf]

Why is the lack of a schema indicator the biggest flaw of protobuf?

[foobiekr]

It makes it impossible to write a general purpose dissector that takes captured messages or bytes and figure out how to parse it.

All they needed was a varint at the head of any marshaled from to at least provide some scoping clue.

[ptspts]

If you parse a serialized protobuf byte array without having a .proto file, you have no way to dustinguish a byte string field from a nested message field. Thus you have no way to know how deep your parser should go.

[css]

Semi-related, one of the `imessage-exporter` contributors provided a great write-up on reverse engineering the handwritten and digital touch message protobufs [0]. The reconstructed proto files are [1] [2].

[0]: https://github.com/trymoose/handwriting2svg/blob/0eb56cf4582...

[1]: https://github.com/ReagentX/imessage-exporter/blob/beeb853b2...

[2]: https://github.com/ReagentX/imessage-exporter/blob/beeb853b2...