[pbs-devel] [PATCH proxmox 1/1] email: add small function to send multi-part emails using sendmail

[Stoiko Ivanov]

Thanks for the patch!

some comments/suggestions on e-mail inline:

On Thu, 20 Aug 2020 11:23:50 +0200
Hannes Laimer <h.laimer at proxmox.com> wrote:

> Signed-off-by: Hannes Laimer <h.laimer at proxmox.com>
> ---
>  proxmox/src/tools/email.rs | 130 +++++++++++++++++++++++++++++++++++++
>  proxmox/src/tools/mod.rs   |   1 +
>  2 files changed, 131 insertions(+)
>  create mode 100644 proxmox/src/tools/email.rs
> 
> diff --git a/proxmox/src/tools/email.rs b/proxmox/src/tools/email.rs
> new file mode 100644
> index 0000000..b73a6d6
> --- /dev/null
> +++ b/proxmox/src/tools/email.rs
> @@ -0,0 +1,130 @@
> +//! Email related utilities.
> +
> +use std::process::{Command, Stdio};
> +use anyhow::{bail, Error};
> +use std::io::Write;
> +use crate::tools::time::time;
> +
> +
> +/// Sends multi-part mail with text and/or html to a list of recipients
> +///
> +/// ``sendmail`` is used for sending the mail.
> +pub fn sendmail(mailto: Vec<&str>,
> +                subject: &str,
> +                text: Option<&str>,
> +                html: Option<&str>,
> +                mailfrom: Option<&str>,
> +                author: Option<&str>) -> Result<(), Error> {
> +    let mail_regex = regex::Regex::new(r"^[a-zA-Z\.0-9]+@[a-zA-Z\.0-9]+$").unwrap();
> +
> +    if mailto.is_empty() {
> +        bail!("At least one recipient has to be specified!")
> +    }
> +
> +    for recipient in &mailto {
> +        if !mail_regex.is_match(recipient) {
> +            bail!("'{}' is not a valid email address", recipient)
> +        }
> +    }
> +
> +    let mailfrom = mailfrom.unwrap_or("root");
> +    if !mailfrom.eq("root") && !mail_regex.is_match(mailfrom) {
> +        bail!("'{}' is not a valid email address", mailfrom)
> +    }
> +
> +    let recipients = mailto.join(",");
> +    let author = author.unwrap_or("Proxmox Backup Server");
> +
> +    let mut sendmail_process = match Command::new("/usr/sbin/sendmail")
> +        .arg("-B")
> +        .arg("8BITMIME")
> +        .arg("-f")
> +        .arg(mailfrom)
> +        .arg("--")
> +        .arg(&recipients)
> +        .stdin(Stdio::piped())
> +        .spawn() {
> +        Err(err) => bail!("could not spawn sendmail process: {}", err),
> +        Ok(process) => process
> +    };
> +    let mut body = String::new();
> +    let boundary = format!("----_=_NextPart_001_{}", time()?);
> +
> +    body.push_str("Content-Type: multipart/alternative;\n");
> +    body.push_str(&format!("\tboundary=\"{}\"\n", boundary));
> +    body.push_str("MIME-Version: 1.0\n");
> +    body.push_str(&format!("FROM: {} <{}>\n", author, mailfrom));
> +    body.push_str(&format!("TO: {}\n", &recipients));
> +    body.push_str(&format!("SUBJECT: {}\n", subject));

iirc the header needs to be encoded if it contains non-ascii characters
(the content-type charset only relates to the body) - I assume that
postfix/exim would do the correct thing these days (and send the mail with
smtputf-8 extension (though I'm not sure what would happen if the
receiving server does not support that)
- would suggest to test sending such a mail with a non-ascii character
in the subject.

writing the header names (TO FROM SUBJECT) in all-caps seems odd to my
eyes (but I guess this is pretty cosmetic)

I would suggest adding a Date header (though postfix does that for locally
submitted e-mail) - else the mails are more likely to be considered spam.

Finally - if you only have a text/plain part I would only send that part
(without the wrapping in multipart/alternative) (similarly for a
single text/html part without text/plain part).


> +    body.push('\n');
> +    body.push_str("This is a multi-part message in MIME format.\n\n");
> +    body.push_str(&format!("--{}\n", boundary));
> +    if let Some(text) = text {
> +        body.push_str("Content-Type: text/plain;\n");
> +        body.push_str("\tcharset=\"UTF8\"\n");
While most MTA, scanners, MUAs won't care much - the charset should
probably be written as 'UTF-8' (see https://tools.ietf.org/html/rfc3629
(section 8))



> +        body.push_str("Content-Transfer-Encoding: 8bit\n");
> +        body.push('\n');
> +        body.push_str(text);
> +        body.push_str(&format!("\n--{}\n", boundary));
> +    }
> +    if let Some(html) = html {
> +        body.push_str("Content-Type: text/html;\n");
> +        body.push_str("\tcharset=\"UTF8\"\n");
> +        body.push_str("Content-Transfer-Encoding: 8bit\n");
> +        body.push('\n');
> +        body.push_str(html);
> +        body.push_str(&format!("\n--{}\n", boundary));
> +    }
> +
> +    if let Err(err) = sendmail_process.stdin.take().unwrap().write_all(body.as_bytes()) {
> +        bail!("couldn't write to sendmail stdin: {}", err)
> +    };
> +
> +    // wait() closes stdin of the child
> +    if let Err(err) = sendmail_process.wait() {
> +        bail!("sendmail did not exit successfully: {}", err)
> +    }
> +
> +    Ok(())
> +}
> +
> +#[cfg(test)]
> +mod test {
> +    use crate::tools::email::sendmail;
> +
> +    #[test]
> +    fn test1() {
> +        let result = sendmail(
> +            vec!["somenotvalidemail!", "somealmostvalid email"],
> +            "Subject1",
> +            Some("TEXT"),
> +            Some("<b>HTML</b>"),
> +            Some("bim at bam.bum"),
> +            Some("test1"));
> +        assert!(result.is_err());
> +    }
> +
> +    #[test]
> +    fn test2() {
> +        let result = sendmail(
> +            vec![],
> +            "Subject2",
> +            None,
> +            Some("<b>HTML</b>"),
> +            None,
> +            Some("test1"));
> +        assert!(result.is_err());
> +    }
> +
> +    #[test]
> +    fn test3() {
> +        let result = sendmail(
> +            vec!["a at b.c"],
> +            "Subject3",
> +            None,
> +            Some("<b>HTML</b>"),
> +            Some("notv at lid.com!"),
> +            Some("test1"));
> +        assert!(result.is_err());
> +    }
> +}
> \ No newline at end of file
> diff --git a/proxmox/src/tools/mod.rs b/proxmox/src/tools/mod.rs
> index 721e5d1..df6c429 100644
> --- a/proxmox/src/tools/mod.rs
> +++ b/proxmox/src/tools/mod.rs
> @@ -10,6 +10,7 @@ pub mod borrow;
>  pub mod byte_buffer;
>  pub mod common_regex;
>  pub mod constnamemap;
> +pub mod email;
>  pub mod fd;
>  pub mod fs;
>  pub mod io;