Dex is an identity service that uses OpenID Connect to drive authentication for other apps. Dex 2.37.0 serves HTTPS with insecure TLS 1.0 and TLS 1.1. `cmd/dex/serve.go` line 425 seemingly sets TLS 1.2 as minimum version, but the whole `tlsConfig` is ignored after `TLS cert reloader` was introduced in v2.37.0. Configured cipher suites are not respected either. This issue is fixed in Dex 2.38.0.

Affected: Go: github.com/dexidp/dex

### Summary

Dex 2.37.0 is serving HTTPS with insecure TLS 1.0 and TLS 1.1.

### Details While working on https://github.com/dexidp/dex/issues/2848 and implementing configurable TLS support, I noticed my changes did not have any effect in TLS config, so I started investigating.

https://github.com/dexidp/dex/blob/70d7a2c7c1bb2646b1a540e49616cbc39622fb83/cmd/dex/serve.go#L425 is seemingly setting TLS 1.2 as minimum version, but the whole tlsConfig is ignored after "TLS cert reloader" was introduced in https://github.com/dexidp/dex/pull/2964. Configured cipher suites are not respected either, as seen on the output.

### PoC Build Dex, generate certs with `gencert.sh`, modify `config.dev.yaml` to run on https, using generated certs.

```console issuer: http://127.0.0.1:5556/dex

storage: type: sqlite3 config: file: dex.db

web: https: 127.0.0.1:5556 tlsCert: examples/k8s/ssl/cert.pem tlsKey: examples/k8s/ssl/key.pem

<rest as default> ```

Run dex `bin/dex serve config.dev.yaml`.

Install `sslyze`, easy to use SSL connection analyzer:

```console pip3 install sslyze sslyze 127.0.0.1:5556 ```

In Dex 2.37.0, TLS 1.0 and TLS 1.1 are enabled in addition to expected TLS 1.2 and TLS 1.3. ```console * TLS 1.0 Cipher Suites: Attempted to connect using 80 cipher suites.

The server accepted the following 6 cipher suites: TLS_RSA_WITH_AES_256_CBC_SHA 256 TLS_RSA_WITH_AES_128_CBC_SHA…