[pve-devel] [PATCH proxmox 1/3] notify: smtp: move building of forwarded mails to separate function

[Lukas Wagner <l.wagner@proxmox.com>]

This allows us to write some tests for it.

No behavioral changes intended.

Signed-off-by: Lukas Wagner <l.wagner@proxmox.com>
---
 proxmox-notify/src/endpoints/smtp.rs | 189 ++++++++++++++-------------
 1 file changed, 97 insertions(+), 92 deletions(-)

diff --git a/proxmox-notify/src/endpoints/smtp.rs b/proxmox-notify/src/endpoints/smtp.rs
index b88e6c95..2f4bad3c 100644
--- a/proxmox-notify/src/endpoints/smtp.rs
+++ b/proxmox-notify/src/endpoints/smtp.rs
@@ -251,98 +251,8 @@ impl Endpoint for SmtpEndpoint {
                     .map_err(|err| Error::NotifyFailed(self.name().into(), Box::new(err)))?
             }
             #[cfg(feature = "mail-forwarder")]
-            Content::ForwardedMail { ref raw, title, .. } => {
-                use lettre::message::header::ContentTransferEncoding;
-                use lettre::message::Body;
-                use tracing::error;
-
-                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) => error!("could not set header: {e}"),
-                        }
-                    }
-                }
-
-                message
+            Content::ForwardedMail { ref raw, .. } => {
+                build_forwarded_message(email_builder, self.name(), raw)?
             }
         };
 
@@ -371,3 +281,98 @@ impl Endpoint for SmtpEndpoint {
         self.config.disable.unwrap_or_default()
     }
 }
+
+/// Construct a lettre `Message` from a raw email message.
+#[cfg(feature = "mail-forwarder")]
+fn build_forwarded_message(
+    email_builder: lettre::message::MessageBuilder,
+    endpoint_name: &str,
+    raw: &[u8],
+) -> Result<Message, Error> {
+    use lettre::message::header::ContentTransferEncoding;
+    use lettre::message::Body;
+    use tracing::error;
+
+    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(parsed_message.subject().unwrap_or_default())
+        .body(body)
+        .map_err(|err| Error::NotifyFailed(endpoint_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) => error!("could not set header: {e}"),
+            }
+        }
+    }
+
+    Ok(message)
+}
-- 
2.39.5



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