Code shared from the Rust Playground

playground.rs

extern crate openssl;

use openssl::rsa::Rsa;
use openssl::pkey::PKey;
use std::str;
use openssl::x509::{X509, X509Name};
use openssl::hash::MessageDigest;
use openssl::nid::Nid;

fn main() {
    let rsa = Rsa::generate(2048).unwrap();
    let pkey = PKey::from_rsa(rsa).unwrap();

    let mut name = X509Name::builder().unwrap();
    name.append_entry_by_nid(Nid::COMMONNAME, "foobar.com").unwrap();
    let name = name.build();

    let mut builder = X509::builder().unwrap();
    builder.set_version(2).unwrap();
    builder.set_subject_name(&name).unwrap();
    builder.set_issuer_name(&name).unwrap();
    builder.set_pubkey(&pkey).unwrap();
    builder.sign(&pkey, MessageDigest::sha256()).unwrap();

    let certificate: X509 = builder.build();

    let pub_key: Vec<u8> = pkey.public_key_to_pem().unwrap();
    println!("{}", str::from_utf8(pub_key.as_slice()).unwrap());

    let pri_key: Vec<u8> = pkey.private_key_to_pem_pkcs8().unwrap();
    println!("{}", str::from_utf8(pri_key.as_slice()).unwrap());

    let pem: Vec<u8> = certificate.to_pem().unwrap();
    println!("{}", str::from_utf8(pem.as_slice()).unwrap());
}