Stem can't fetch hidden service descriptors with descriptor ID.

https://gitweb.torproject.org/torspec.git/tree/control-spec.txt#n1548

"HSFETCH" SP (HSAddress / "v" Version "-" DescId)
              *[SP "SERVER=" Server] CRLF

Control-spec states that HSFETCH can be done with a specific descriptor ID, but because stem enforcesa address check with stem.util.tor_tools.is_valid_hidden_service_address() this can't be done.

Trac:
Username: moonsikpark

added component::archived/stem owner::atagar priority::medium resolution::not a bug severity::normal status::closed tor-hs type::defect + 1 deleted label

PR: https://github.com/torproject/stem/pull/25

Trac:
Username: moonsikpark

Thanks moonsikpark! If await_result is provided this looks like it'll fail (note the "event.address == address" conditionals below).

Would you mind describing your use case? I've never run across someone that wanted to query HS descriptors via their identifier.

In checking the spec there's a couple other wrinkles with identifier queries...

• "DescIDs can only be version 2 IDs."

  So despite taking a version prefix this doesn't work at all with v3 services. This is a bit concerning because v2 will be deprecated at some point. Is there a ticket for adding tor support for querying v3 services by their descriptor id? If not then it sounds like this capability might be going away.

• "If a DescId is specified, at least one Server MUST also be provided"

  If we do decide to support this within stem we'll need to raise a ValueError if we get a descriptor id and a server argument is not supplied.

Replying to atagar:

Thanks moonsikpark! If await_result is provided this looks like it'll fail (note the "event.address == address" conditionals below).

Would you mind describing your use case? I've never run across someone that wanted to query HS descriptors via their identifier.

In checking the spec there's a couple other wrinkles with identifier queries...

• "DescIDs can only be version 2 IDs."

  So despite taking a version prefix this doesn't work at all with v3 services. This is a bit concerning because v2 will be deprecated at some point. Is there a ticket for adding tor support for querying v3 services by their descriptor id? If not then it sounds like this capability might be going away.

• "If a DescId is specified, at least one Server MUST also be provided"

  If we do decide to support this within stem we'll need to raise a ValueError if we get a descriptor id and a server argument is not supplied.

There's no equivalent for the "Descriptor ID" in the v3 onion service protocol.

The onion address can be used to derive a blinded public key for each time period: https://gitweb.torproject.org/torspec.git/tree/rend-spec-v3.txt#n655

The blinded public key works on any HSDir: https://gitweb.torproject.org/torspec.git/tree/rend-spec-v3.txt#n974

And the blinded public key can be used to find the relevant set of HSDirs: https://gitweb.torproject.org/torspec.git/tree/rend-spec-v3.txt#n781

For debugging, we might eventually want to query the previous/current/next sets of HSDirs, but that's complicated, and not implemented yet: https://gitweb.torproject.org/torspec.git/tree/rend-spec-v3.txt#n885

Trac:
Resolution: N/A to not a bug
Status: new to closed

closed