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 <l.wag...@proxmox.com> --- Notes: proxmox-mail-forward needs a bump once this is applied. Changes since v1: - Use more efficient method for string formatting when reassembling mail headers (thx @ Wolfgang) proxmox-notify/src/endpoints/smtp.rs | 102 ++++++++++++++++++++++++--- 1 file changed, 91 insertions(+), 11 deletions(-) diff --git a/proxmox-notify/src/endpoints/smtp.rs b/proxmox-notify/src/endpoints/smtp.rs index 064c9f9..28f9909 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 +232,96 @@ 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 in '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. + 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() { + use std::fmt::Write; + + for attribute in attributes { + let _ = write!( + &mut value, + "; {}=\"{}\"", + attribute.0, attribute.1 + ); + } + } + 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 _______________________________________________ pve-devel mailing list pve-devel@lists.proxmox.com https://lists.proxmox.com/cgi-bin/mailman/listinfo/pve-devel
