Metadata: escape display name in email addresses

src/metadata.rs

@@ -226,7 +226,7 @@ impl Metadata21 {
                 for author in authors {
                     match (&author.name, &author.email) {
                         (Some(name), Some(email)) => {
-                            emails.push(format!("{name} <{email}>"));
+                            emails.push(format_email_with_display_name(name, email));
                         }
                         (Some(name), None) => {
                             names.push(name.as_str());
@@ -251,7 +251,7 @@ impl Metadata21 {
                 for maintainer in maintainers {
                     match (&maintainer.name, &maintainer.email) {
                         (Some(name), Some(email)) => {
-                            emails.push(format!("{name} <{email}>"));
+                            emails.push(format_email_with_display_name(name, email));
                         }
                         (Some(name), None) => {
                             names.push(name.as_str());
@@ -555,6 +555,23 @@ impl Metadata21 {
     }
 }
 
+/// Escape email addresses with display name if necessary
+/// according to RFC 822 Section 3.3. "specials".
+fn format_email_with_display_name(mut display_name: &str, email: &str) -> String {
+    if display_name.chars().any(|c| {
+        matches!(
+            c,
+            '(' | ')' | '<' | '>' | '@' | ',' | ';' | ':' | '\\' | '"' | '.' | '[' | ']'
+        )
+    }) {
+        return format!(
+            "\"{}\" <{email}>",
+            display_name.replace("\\", "\\\\").replace("\"", "\\\"")
+        );
+    }
+    format!("{display_name} <{email}>")
+}
+
 /// Fold long header field according to RFC 5322 section 2.2.3
 /// https://datatracker.ietf.org/doc/html/rfc5322#section-2.2.3
 fn fold_header(text: &str) -> String {