Lack of support for p521 signatures with the `ring`-based `reqwest/rustls` backend about rustup

[djc]

Yes -- rustls should support P521 since https://github.com/rustls/rustls/releases/tag/v%2F0.22.2 if we switch to aws-lc-rs.

[kornelski]

@djc I'll try to find the reason for the p521 curve, but I'm pretty sure the choice is quite deliberate. WARP is written in Rust, so the engineers developing it feel themselves the pain of ring being incompatible with it. The ring PR is by a Cloudflare engineer.

[djc]

@kornelski I think we'll be able to use aws-lc-rs but would still be interested in hearing the reasons that it's used!

[djc]

@rami3l reqwest allows configuring the ClientBuilder with a pre-built ClientConfig (of the matching Rustls release), so I think we can build a rustls 0.22 ClientConfig and configure reqwest to use this.

@djc That's the way to do manual resolution at runtime right? Shouldn't there be a way to simply remove ring if we're not using it?

Unfortunately it doesn't look like that exists in reqwest right now. Let's see if I can move that forward.

[djc]

@kornelski but in terms of impact: this specifically impacts Cloudflare's WARP deployment, right, not the default deployment one would get when setting up WARP for their organization?

(I revised seanmonstar/reqwest#2225 yesterday to try to make progress on this.)

[kornelski]

It impacts more than just internal Cloudflare deployment. Customers have an option to upload their own CA cert (which can use any signature algorithm), but if they don't, the default Cloudflare cert is used. I don't have data on how many deployments use the incompatible cert.

[rami3l]

@djc Can we use aws-lc instead of ring for rustls?

aws-lc seems to have p521 support already; OTOH comparing aws-lc's platform support and that of ring I can see that the former lacks mips*, but since we don't do mips* anymore (dfd71c0) this shouldn't be a problem...

I'm still not very familiar to the subject so please feel free to correct me if I'm wrong.

[rami3l]

@djc (A newbie question:) I tried adding

[dependencies]
rustls = { version = "0.22", optional = true, default-features = false, features = ["logging", "aws_lc_rs", "tls12"] }

... to our Cargo.toml but looks like ring is still there in the lockfile. Actually, both aws-lc-rs and ring are in the dependencies now, which may cause problems as described in seanmonstar/reqwest#2225 (comment).

Am I doing anything wrong, or we need to wait for something like seanmonstar/reqwest#2136?

[djc]

@rami3l reqwest allows configuring the ClientBuilder with a pre-built ClientConfig (of the matching Rustls release), so I think we can build a rustls 0.22 ClientConfig and configure reqwest to use this.

[rami3l]

@rami3l reqwest allows configuring the ClientBuilder with a pre-built ClientConfig (of the matching Rustls release), so I think we can build a rustls 0.22 ClientConfig and configure reqwest to use this.

@djc That's the way to do manual resolution at runtime right? Shouldn't there be a way to simply remove ring if we're not using it?

[kornelski]

In WARP, the p521 curve has been chosen as the best algorithm with FIPS compliance.

The p521 signature is necessary "only" to validate the root CA certificate used by WARP MITM. At the same time this is the hardest thing to change in this setup, so it's very unlikely to be changed anytime soon.