How can I get details about the SSL certificate returned by the server?

Hey,

I'm wondering if it is possible to obtain details of the SSL certificate returned by the server when using Hyper as an HTTPS client? I've got this example:

#![deny(warnings)]
#![warn(rust_2018_idioms)]
use std::{env};

use hyper::{Client};
use hyper_tls::HttpsConnector;

// A simple type alias so as to DRY.
type Result<T> = std::result::Result<T, Box<dyn std::error::Error + Send + Sync>>;

#[tokio::main]
async fn main() -> Result<()> {
    pretty_env_logger::init();

    // Some simple CLI args requirements...
    let url = match env::args().nth(1) {
        Some(url) => url,
        None => {
            println!("Usage: client <url>");
            return Ok(());
        }
    };

    // HTTPS requires picking a TLS implementation, so give a better
    // warning if the user tries to request an 'https' URL.
    let url = url.parse::<hyper::Uri>().unwrap();

    fetch_url(url).await
}

async fn fetch_url(url: hyper::Uri) -> Result<()> {
    let https = HttpsConnector::new();
    let client = Client::builder().build::<_, hyper::Body>(https);

    let res = client.get(url).await?;

    println!("Response: {}", res.status());
    println!("Headers: {:#?}\n", res.headers());

    println!("Extensions: {:#?}\n", res.extensions().len());

    // Stream the body, writing each chunk to stdout as we get it
    // (instead of buffering and printing at the end).
    // while let Some(next) = res.data().await {
    //     let chunk = next?;
    //     io::stdout().write_all(&chunk).await?;
    // }

    println!("\n\nDone!");

    Ok(())
}

And I'm wondering how can I use the https object or the response object to get the details of the server certificate?

I tried following the code, and it seems that the cert value is not exposed in the public API of this package, but I thought I'd ask.

Thanks in advance for your help!

hyperium / hyper-tls

How can I get details about the SSL certificate returned by the server? #91