Add Async OHTTP client

[arminsabouri]

OHTTP lets a client send encrypted requests through a relay so the server can’t see who sent them and the relay can’t see what they contain. The following commit adds optional configurations to enable clients to proxy their requests through an OHTTP relay and gateway.

OHTTP functionality is feature flagged off behind async-ohttp. If a client provided OHTTP config it will attempt to use the relay instead of the target resource directly.

---

This work was first started by @alexlwn123
Tested against a blockstream's electrs and running an OHTTP relay and OHTTP Gateway locally. Automated tests are still TODO.

Seeking concept Ack/Nack

[luisschwab]

Concept ACK, this is a cool ideia. We are, however, in the process of completely dropping reqwest/minreq in favor of bitreq. Can you change the PR to use that?

[arminsabouri]

Concept ACK, this is a cool ideia. We are, however, in the process of completely dropping reqwest/minreq in favor of bitreq. Can you change the PR to use that?

Sure. Looks like the bitreq migration is a WIP #137. I may wait till thats in good shape before rebasing my commits on top of that.

[pseudozach]

I’ve also got a branch that ports this to the current bitreq client and gets the CI passing:
https://github.com/pseudozach/rust-esplora-client/tree/ohttp-bitreq

I also ended up building a compatible Bitcoin-HPKE OHTTP gateway (obitcoin) so I could actually do end-to-end testing with the client.

If any of that is useful, I’m happy to fold the gateway-backed smoke test, CI workflow, or related pieces into this PR, or you can cherry-pick whatever is helpful.

[arminsabouri]

I’ve also got a branch that ports this to the current bitreq client and gets the CI passing: https://github.com/pseudozach/rust-esplora-client/tree/ohttp-bitreq

This was useful ref for marking certain deps as duplicates. Thank you.

I also ended up building a compatible Bitcoin-HPKE OHTTP gateway (obitcoin) so I could actually do end-to-end testing with the client.
If any of that is useful, I’m happy to fold the gateway-backed smoke test, CI workflow, or related pieces into this PR, or you can cherry-pick whatever is helpful.

I suppose it could reduce the test boilerplate in this PR. i.e removing my dummy gateway. Do you already have a int. . e2e test that uses your gateway?

[pseudozach]

I’ve also got a branch that ports this to the current bitreq client and gets the CI passing: https://github.com/pseudozach/rust-esplora-client/tree/ohttp-bitreq

This was useful ref for marking certain deps as duplicates. Thank you.

happy to hear that!

I suppose it could reduce the test boilerplate in this PR. i.e removing my dummy gateway. Do you already have a int. . e2e test that uses your gateway?

e2e test is available here: https://github.com/pseudozach/rust-esplora-client/blob/ohttp-bitreq/tests/ohttp_smoke.rs
and runs here: https://github.com/pseudozach/rust-esplora-client/blob/ohttp-bitreq/.github/workflows/ohttp-smoke.yml