Move to newer TLS policies on CloudFront

[Mark-Simulacrum]

Policy docs are here - https://docs.aws.amazon.com/AmazonCloudFront/latest/DeveloperGuide/secure-connections-supported-viewer-protocols-ciphers.html

I suspect we want to choose TLSv1.2_2021, but I don't know if there's a good way to evaluate whether we're cutting anyone off. Anything routed through Fastly should be pretty safe to switch to the newer policy I think.

Our Fastly configuration is currently "TLS v1.2 & TLS v1.3 + 0RTT" across all 4 domains here -- afaict, that's limiting to 1.2 and 1.3 (with optional early data support).[^1]

[^1]: HTTP/3 is technically supported but seems to need a different domain (n.sni.global.fastly.net) which we don't CNAME to.

Current setup:

TLSv1:

• static.crates.io
• cloudfront-static.crates.io
• static.staging.crates.io
• cloudfront-static.staging.crates.io
• staging.crates.io
• crates.io
• www.crates.io
• cratesio.com
• www.cratesio.com
• www.docs.rs
• www.docsrs.com
• docsrs.com
• arewewebyet.org
• package.metadata.docs.rs
• index.crates.io
• index.staging.crates.io
• cfp.rustconf.com

TLSv1.1_2016:

• dev-static.rust-lang.org
• cloudfront-dev-static.rust-lang.org
• static.rust-lang.org
• cloudfront-static.rust-lang.org
• rust-lang.org
• www.rustlang.net
• www.rustlang.org
• www.rustlang.com
• www.rust-lang.com
• www.rust-lang.net
• win.rustup.rs
• sh.rustup.rs
• www.rustup.rs
• rustup.net
• www.rustup.org
• rustup.org
• www.rustup.net
• rustup.rs
• doc.rust-lang.org
• rustlang.net
• rustlang.com
• rustlang.org
• rust-lang.com
• rust-lang.net
• docs.rust-lang.org
• dev-doc.rust-lang.org
• beta.rust-lang.org
• www.rust-lang.org
• docs.rs
• thanks.rust-lang.org
• reach.rust-lang.org
• test.docs.rs
• dev.rustup.rs
• play.rust-lang.org
• dev-win.rustup.rs
• rustup-builds.rust-lang.org"

TLSv1.2_2021:

• prev.rust-lang.org
• forge.rust-lang.org
• ci-mirrors.rust-lang.org
• ci-caches.rust-lang.org
• ci-artifacts.rust-lang.org
• perf-data.rust-lang.org
• crates-io-index-temp.rust-lang.org
• static.docs.rs

[jdno]

When we rolled out Fastly, we started with their HTTP/3 & TLS v1.3 + 0RTT (n.sni.global.fastly.net) configuration, given that TLS v1.1 has been deprecated since forever. But that caused issues with cargo on Windows XP (https://github.com/rust-lang/cargo/issues/12296), so Fastly enabled a legacy configuration for us with TLS v1.2 and more cipher suites.

[i486]

index.crates.io (dualstack.n.sni.global.fastly.net) now only supports TLS 1.3 (2025) and TLS 1.2 with the following three cipher suites:

• ECDHE-RSA-AES256-GCM-SHA384
• ECDHE-RSA-AES128-GCM-SHA256
• ECDHE-RSA-CHACHA20-POLY1305

This configuration is even more restrictive than CloudFront’s TLSv1.2_2025 policy.

Is this change intentional? As a result, Cargo no longer works on any version of Windows older than Windows 10 unless a proxy/tunnel is used or the slower Git-based index fallback is enabled.

[Mark-Simulacrum]

I don't think that was intentional. We'll need to look at adjusting the configuration to match what our other Fastly endpoints use.