Certificate verification fails on Windows native build

[LPardue]

The http3-client fails certificate verification when built natively, e.g.

$ http3-client https://cloudflare-quic.com
snip...
[2019-06-15T11:43:24.931343300Z TRACE quiche::tls] error:1000007d:SSL routines:OPENSSL_internal:CERTIFICATE_VERIFY_FAILED
[2019-06-15T11:43:24.937788700Z ERROR http3_client] 88dab5f9b993280072028d5b4d34d30a4e3c recv failed: TlsFail

The cert for cloudflare-quic.com is trusted by my machine. So I suspect this is something related to building quiche in a way that properly imports my system trust store.

[LPardue]

One path of research suggests this used to be a problem for rustup. They had a mini crate that could attempt to load certs manually from the platform store and then manually populate the store object used by SSL library. The code for windows is here, https://github.com/rust-lang/rustup.rs/blob/27fccd3500321ee66da77589d3f4a65fcc7bddfb/src/ca-loader/src/sys/windows.rs

Based on that example, you'd do something like below in quiche's tls.rs, which would require exposing a few new functions

let bundle = CertBundle::new();
let store = X509_STORE_new();
for cert in bundle {
    X509_STORE_add_cert(store, cert);
}

[LPardue]

I have a working PoC for this. Needs some tidy up but I can create a PR soon.