[tor-bugs] #33650 [Core Tor/Tor]: Verify that intro2 cell extensions actually work

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#33650: Verify that intro2 cell extensions actually work
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 Reporter:  arma                                 |          Owner:
                                                 |  mikeperry
     Type:  task                                 |         Status:
                                                 |  accepted
 Priority:  Medium                               |      Milestone:
Component:  Core Tor/Tor                         |        Version:
 Severity:  Normal                               |     Resolution:
 Keywords:  tor-dos tor-dos-2020 anonymous-      |  Actual Points:
  credentials research                           |
Parent ID:                                       |         Points:
 Reviewer:                                       |        Sponsor:
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Comment (by mikeperry):

 Notes on v3 HSDesc codepaths:
  - We probably want to add our field in the superencrypted section. The
 spec says this may be extended.
  - v3 descriptors are built via `hs_desc_encode_descriptor()`, which calls
 `desc_encode_v3()` via a table lookup
  - The superencrypted stuff is done in `encode_superencrypted_data()`,
 which builds the fields in `build_secret_data()`
  - Decoding on the client side happens via `hs_desc_decode_descriptor()`,
 which calls down to `desc_decode_encrypted_v3()`, and then
 `hs_desc_decode_superencrypted()` and `hs_desc_decode_encrypted()`

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/33650#comment:6>
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