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[smtp.rs, proxmox.com] Subject: Re: [pve-devel] [PATCH proxmox 1/2] notify: smtp: forward original message instead nesting X-BeenThere: pve-devel@lists.proxmox.com X-Mailman-Version: 2.1.29 Precedence: list List-Id: Proxmox VE development discussion List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 09 Jan 2024 13:27:18 -0000 On Wed, Dec 13, 2023 at 05:42:00PM +0100, Lukas Wagner wrote: > For mails forwarded by `proxmox-mail-forward` to an SMTP target, the > original message was nested as a 'message/rfc822' message part. > Originally this approach was chosen to avoid having to rewrite > message headers. > Good email-clients, such as Thunderbird can display these inline. > Other, more limited clients will show these messages as an attached > .eml file, which is not really a good user experience. > > This patch changes the approach for message forwarding to be more like > forwarding mails in a mail client. We create a new message and > add the original message body as a body. Additionally, we also copy > over all message headers that are relevant to correctly display the > original message body (e.g. Content-Type, Content-Transfer-Encoding) > > Tested with a couple of different email messages (varying in > structure, body parts, encoding, etc.) against the following SMTP > relays: > - gmail > - outlook > - our own webmail service > > Originally reported in our community forum: > https://forum.proxmox.com/threads/proxmox-mail-forward-sends-mails-as-eml.137710/ > > Signed-off-by: Lukas Wagner > --- > > Notes: > proxmox-mail-forward needs a bump once this is applied. > > proxmox-notify/src/endpoints/smtp.rs | 99 ++++++++++++++++++++++++---- > 1 file changed, 88 insertions(+), 11 deletions(-) > > diff --git a/proxmox-notify/src/endpoints/smtp.rs b/proxmox-notify/src/endpoints/smtp.rs > index 064c9f9..4b8ff2d 100644 > --- a/proxmox-notify/src/endpoints/smtp.rs > +++ b/proxmox-notify/src/endpoints/smtp.rs > @@ -1,8 +1,9 @@ > +use std::time::Duration; > + > use lettre::message::{Mailbox, MultiPart, SinglePart}; > use lettre::transport::smtp::client::{Tls, TlsParameters}; > use lettre::{message::header::ContentType, Message, SmtpTransport, Transport}; > use serde::{Deserialize, Serialize}; > -use std::time::Duration; > > use proxmox_schema::api_types::COMMENT_SCHEMA; > use proxmox_schema::{api, Updater}; > @@ -231,17 +232,93 @@ impl Endpoint for SmtpEndpoint { > } > #[cfg(feature = "mail-forwarder")] > Content::ForwardedMail { ref raw, title, .. } => { > - email_builder = email_builder.subject(title); > + use lettre::message::header::{ContentTransferEncoding, HeaderName, HeaderValue}; > + use lettre::message::Body; > > - // Forwarded messages are embedded inline as 'message/rfc822' > - // this let's us avoid rewriting any headers (e.g. From) > - email_builder > - .singlepart( > - SinglePart::builder() > - .header(ContentType::parse("message/rfc822").unwrap()) > - .body(raw.to_owned()), > - ) > - .map_err(|err| Error::NotifyFailed(self.name().into(), Box::new(err)))? > + let parsed_message = mail_parser::Message::parse(raw) > + .ok_or_else(|| Error::Generic("could not parse forwarded email".to_string()))?; > + > + let root_part = parsed_message > + .part(0) > + .ok_or_else(|| Error::Generic("root message part not present".to_string()))?; > + > + let raw_body = parsed_message > + .raw_message() > + .get(root_part.offset_body..root_part.offset_end) > + .ok_or_else(|| Error::Generic("could not get raw body content".to_string()))?; > + > + // We assume that the original message content is already properly > + // encoded, thus we add the original message body 'Binary' encoding. > + // This prohibits lettre from trying to re-encode our raw body data. > + // lettre will automatically set the `Content-Transfer-Encoding: binary` header, > + // which we need to remove. The actual transfer encoding is later > + // copied from the original message headers. > + let body = > + Body::new_with_encoding(raw_body.to_vec(), ContentTransferEncoding::Binary) > + .map_err(|_| Error::Generic("could not create body".into()))?; > + let mut message = email_builder > + .subject(title) > + .body(body) > + .map_err(|err| Error::NotifyFailed(self.name().into(), Box::new(err)))?; > + message > + .headers_mut() > + .remove_raw("Content-Transfer-Encoding"); > + > + // Copy over all headers that are relevant to display the original body correctly. > + // Unfortunately this is a bit cumbersome, as we use separate crates for mail parsing (mail-parser) > + // and creating/sending mails (lettre). > + // Note: Other MIME-Headers, such as Content-{ID,Description,Disposition} are only used > + // for body-parts in multipart messages, so we can ignore them for the messages headers. > + // Since we send the original raw body, the part-headers will be included any way. > + for header in parsed_message.headers() { > + let header_name = header.name.as_str(); > + // Email headers are case-insensitive, so convert to lowercase... > + let value = match header_name.to_lowercase().as_str() { > + "content-type" => { > + if let mail_parser::HeaderValue::ContentType(ct) = header.value() { > + // mail_parser does not give us access to the full decoded and unfolded > + // header value, so we unfortunately need to reassemble it ourselves. > + // Meh. urgh > + let mut value = ct.ctype().to_string(); > + if let Some(subtype) = ct.subtype() { > + value.push('/'); > + value.push_str(subtype); > + } > + if let Some(attributes) = ct.attributes() { > + for attribute in attributes { > + value.push_str(&format!( > + "; {}=\"{}\"", > + attribute.0, attribute.1 > + )); should be more efficient to use let _ = write!(value, "..."); instead of `push_str()` on a temporarily allocated (format!()) string. > + } > + } > + Some(value) > + } else { > + None > + } > + } > + "content-transfer-encoding" | "mime-version" => { > + if let mail_parser::HeaderValue::Text(text) = header.value() { > + Some(text.to_string()) > + } else { > + None > + } > + } > + _ => None, > + }; > + > + if let Some(value) = value { > + match HeaderName::new_from_ascii(header_name.into()) { > + Ok(name) => { > + let header = HeaderValue::new(name, value); > + message.headers_mut().insert_raw(header); > + } > + Err(e) => log::error!("could not set header: {e}"), > + } > + } > + } > + > + message > } > }; > > -- > 2.39.2