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as_string() produces empty line in header that can cause MTA rejection #59

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Hocuri opened this issue Dec 30, 2020 · 1 comment · May be fixed by #60
Open

as_string() produces empty line in header that can cause MTA rejection #59

Hocuri opened this issue Dec 30, 2020 · 1 comment · May be fixed by #60

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@Hocuri
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Hocuri commented Dec 30, 2020

Under some circumstances a the header in the final email contains an empty line. We are building an email client, and some messages are rejected because of this: deltachat/deltachat-core-rust#2118

This test reproduces the problem:

#[test]
fn test_no_empty_directly() {
    let to_tuples = vec![
        ("Nnnn", "[email protected]"),
        ("😀 ttttttt", "[email protected]"),
        ("dididididididi", "[email protected]"),
        ("Ttttttt", "[email protected]"),
        ("Mmmmm", "[email protected]"),
        ("Zzzzzz", "[email protected]"),
        ("Xyz", "[email protected]"),
        ("", "[email protected]"),
        ("qqqqqq", "[email protected]"),
        ("bbbb", "[email protected]"),
        ("", "[email protected]"),
        ("rqrqrqrqr", "[email protected]"),
        ("tttttttt", "[email protected]"),
        ("", "[email protected]"),
    ];
    let mut to = Vec::new();
    for (name, addr) in to_tuples {
        if name.is_empty() {
            to.push(Address::new_mailbox(addr.to_string()));
        } else {
            to.push(Address::new_mailbox_with_name(
                name.to_string(),
                addr.to_string(),
            ));
        }
    }

    let mut message = email::MimeMessage::new_blank_message();
    message.headers.insert(
        (
            "Content-Type".to_string(),
            "text/plain; charset=utf-8; format=flowed; delsp=no".to_string(),
        )
            .into(),
    );
    message
        .headers
        .insert(Header::new_with_value("To".into(), to).unwrap());
    message.body = "Hi".to_string();

    println!("======= HEADERS BEFORE CALL TO AS_STRING: =======");
    for h in message.headers.iter() {
        println!("{}", h);
    }
    let msg = message.as_string(); // <-- seems like here the empty line is introduced

    let header_end = msg.find("Hi").unwrap();
    let headers = msg[0..header_end].trim();
    println!(
        "======= HEADERS AFTER CALL TO AS_STRING: =======\n{}\n",
        headers
    );
    assert!(!headers.lines().any(|l| l.trim().is_empty())); // <--  panics
}

Output:

======= HEADERS BEFORE CALL TO AS_STRING: =======
Content-Type: text/plain; charset=utf-8; format=flowed; delsp=no
To: Nnnn <[email protected]>, 
        =?utf-8?q?=F0=9F=98=80_ttttttt?= <[email protected]>, 
        dididididididi <[email protected]>, Ttttttt <[email protected]>, 
        Mmmmm <[email protected]>, Zzzzzz <[email protected]>, 
        Xyz <[email protected]>, <[email protected]>, qqqqqq <[email protected]>, 
        bbbb <[email protected]>, <[email protected]>, rqrqrqrqr <[email protected]>, 
        tttttttt <[email protected]>, <[email protected]>
======= HEADERS AFTER CALL TO AS_STRING: =======
Content-Type: text/plain; charset=utf-8; format=flowed; delsp=no
To: Nnnn <[email protected]>, 
        =?utf-8?q?=F0=9F=98=80_ttttttt?= <[email protected]>, 
        dididididididi <[email protected]>, Ttttttt <[email protected]>, 
        Mmmmm <[email protected]>, Zzzzzz <[email protected]>, 
        Xyz <[email protected]>, <[email protected]>, qqqqqq <[email protected]>, 
        bbbb <[email protected]>, <[email protected]>, rqrqrqrqr <[email protected]>,

        tttttttt <[email protected]>, <[email protected]>

thread 'mimefactory::tests::test_no_empty_directly' panicked at 'assertion failed: !headers.lines().any(|l| l.trim().is_empty())', src/mimefactory.rs:1649:9
@Hocuri
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Hocuri commented Jan 1, 2021

I just realized that the test doesn't correctly reproduce the problem in the newest version, but it's still there. Here is a test that should work:

#[test]
fn test_emit_no_empty_lines() {
    // Please don't change anything to the intendation:
    let header = "To: Nnnn <[email protected]>, 
=?utf-8?q?=F0=9F=98=80_ttttttt?= <[email protected]>, 
dididididididi <[email protected]>, Ttttttt <[email protected]>, 
Mmmmm <[email protected]>, Zzzzzz <[email protected]>, 
Xyz <[email protected]>, <[email protected]>, qqqqqq <[email protected]>, 
bbbb <[email protected]>, <[email protected]>, rqrqrqrqr <[email protected]>, 
tttttttt <[email protected]>, <[email protected]>";

    let mut builder = Rfc5322Builder::new();

    builder.emit_folded(&header.to_string()[..]);
    builder.emit_raw("\r\n");
    builder.emit_raw("\r\n");

    let res = builder.result().trim();
    println!("{}", res);
    assert!(!res.lines().any(|l| l.trim().is_empty())); // <--  panics
}

@Hocuri Hocuri linked a pull request Jan 1, 2021 that will close this issue
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Don't let headers contain newlines, fix fn emit_folded() deltachat/rust-email
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@Hocuri