imap::client::Client::authenticate: Base64 encode the result of the A…

[kmkaplan]

Fixes issue #95.

Please bear with me, I'm only beginning Rust.

I see two issues with this one-liner:

1. it is not backward compatible. What's the rules for this?
2. as Authenticator::process returns a String, it is not possible to submit arbitrary binary data. For fixing this process would have to return a Vec<u8>. What do you think?

[jonhoo]

There are already a number of breaking changes pending that are waiting on #69, so I'm not too concerned about 1. As for 2, that's a good question... In some sense, what we want is something that returns impl AsRef<[u8]> (which could be both Vec<u8> and &str). Can you try that type and change the .as_str() to .as_ref()?

[jonhoo]

Hmm, actually, no, that won't work. The way to actually do this is to change the Authenticator trait to be this:

pub trait Authenticator {
    type Response: AsRef<[u8]>;

    fn process(&self, challenge: &str) -> Self::Response;
}

Should we make challenge a &[u8] too? I don't know what the spec says here?

[kmkaplan]

IMAP 4rev1 says:

A server challenge consists of a command continuation request response with the "+" token followed by a BASE64 encoded string.

So I guess we should also change the challenge to &[u8].

Tasks for next pull request:

1. change Authenticator to accept and return AsRef([u8]),
2. update examples/gmail_oauth2.rs to use the new Authenticator.

[jonhoo]

Yeah, I think that means we should base64 decode the server challenge before passing it to the Authenticator, which suggests that we should have challenge: &[u8]. You should just make those changes to this PR instead of opening another one. You can make more modifications by pushing more commits to the branch you already have open :)

[jonhoo]

Awesome, I think we're nearly there! I'd like to request two more relatively straightforward changes:

• Change challenge from Vec<u8> to &[u8]
• Add a short documentation string to the associated type and method of Authenticate to mention that base64 encode/decode happens automatically :) Maybe also a line to the trait itself giving a reference to the relevant part of the IMAP spec for auth?

[jonhoo]

Beautiful, thank you!