Termux is Android terminal emulator and Linux environment app, some users are expecting to use rustc on termux (including some chromebook users). This will help fix rust-lang/rustup#1058.

Even if rust-openssl/rust-openssl#610 got fixed, termux has its own environment, so it seems reasonable to use termux installed certificates.

According to this comment this may not work? In testing locally though does this work out for you?

Running this program

extern crate openssl_probe;

pub fn main() {
    openssl_probe::init_ssl_cert_env_vars();
    println!("{:?}", ::std::env::var_os("SSL_CERT_FILE"));
}

on my phone prints:

Some("/data/data/com.termux/files/usr/etc/tls/cert.pem")

Which is the correct path. Testing with rustup is a bit more complicated (I would have to set various path dependencies...), but considering this simple example, I think it will work. Note that init_ssl_cert_env_vars is called direct in the rustup code and indirect (via curl easy) in cargo.

Can you clarify why the comment you link suggest that it may not work?

Oh right yeah I'm confident the env vars are set, but is that actually read by Cargo/rustup and does it fix the certificate problems you were seeing?

Ok, after some trouble I was able to build rustup-init with this update and can assert that it worked.

I checked the rustup code and it is using curl crate (the direct call to init_ssl_cert_env_vars is in rustls backend). The curl crate is calling init_ssl_cert_env_vars. Considering that cargo is also using curl,
I suppose that cargo will work too.

Sorry for trying to hurry...

Oh no worries! Just wanted to make sure we had at least one data point :)

Thanks for checking!

Thanks! You you mind releasing a 0.1.1 version?

Certainly, done!

Could it be something like this?

pub fn find_certs_dirs() -> Vec<PathBuf> {
    // see http://gagravarr.org/writing/openssl-certs/others.shtml
    let prefix = var_os("PREFIX").unwrap_or("");
    [
        "/var/ssl",
        "/usr/share/ssl",
        "/usr/local/ssl",
        "/usr/local/openssl",
        "/usr/local/share",
        "/usr/lib/ssl",
        "/usr/ssl",
        "/etc/openssl",
        "/etc/pki/tls",
        "/etc/ssl",
        "/etc/tls",
    ].iter().map(|s| PathBuf::from(*s)).filter(|p| {
        fs::metadata(format!("{}{}", prefix, p)).is_ok()
    }).collect()
}

so, every system that has a PREFIX like termux does would be covered here

Do you know other systems that use PREFIX env var?

@malbarbo I don't know but it would be cool because autotools also allows --prefix