Follow RFC 2231 in order to properly encode the Content-Disposition header (#685)

Uses RFC 2231 to encode the Content-Disposition header

Cargo.toml

@@ -29,6 +29,7 @@ fastrand = { version = "1.4", optional = true }
 quoted_printable = { version = "0.4", optional = true }
 base64 = { version = "0.13", optional = true }
 regex = { version = "1", default-features = false, features = ["std", "unicode-case"] }
+email-encoding = { git = "https://github.com/lettre/email-encoding.git", rev = "9b55bae0ed02ca52f6fb86a82b4814baa712e45a", optional = true }
 
 # file transport
 uuid = { version = "0.8", features = ["v4"], optional = true }
@@ -81,7 +82,7 @@ name = "transport_smtp"
 
 [features]
 default = ["smtp-transport", "pool", "native-tls", "hostname", "builder"]
-builder = ["httpdate", "mime", "base64", "fastrand", "quoted_printable"]
+builder = ["httpdate", "mime", "base64", "fastrand", "quoted_printable", "email-encoding"]
 mime03 = ["mime"]
 
 # transports

src/message/header/content_disposition.rs

@@ -1,3 +1,7 @@
+use std::fmt::Write;
+
+use email_encoding::headers::EmailWriter;
+
 use super::{Header, HeaderName, HeaderValue};
 use crate::BoxError;
 
@@ -5,25 +9,47 @@ use crate::BoxError;
 ///
 /// Defined in [RFC2183](https://tools.ietf.org/html/rfc2183)
 #[derive(Debug, Clone, PartialEq)]
-pub struct ContentDisposition(String);
+pub struct ContentDisposition(HeaderValue);
 
 impl ContentDisposition {
     /// An attachment which should be displayed inline into the message
     pub fn inline() -> Self {
-        Self("inline".into())
+        Self(HeaderValue::dangerous_new_pre_encoded(
+            Self::name(),
+            "inline".to_string(),
+            "inline".to_string(),
+        ))
     }
 
     /// An attachment which should be displayed inline into the message, but that also
     /// species the filename in case it were to be downloaded
     pub fn inline_with_name(file_name: &str) -> Self {
-        debug_assert!(!file_name.contains('"'), "file_name shouldn't contain '\"'");
-        Self(format!("inline; filename=\"{}\"", file_name))
+        Self::with_name("inline", file_name)
     }
 
     /// An attachment which is separate from the body of the message, and can be downloaded separately
     pub fn attachment(file_name: &str) -> Self {
-        debug_assert!(!file_name.contains('"'), "file_name shouldn't contain '\"'");
-        Self(format!("attachment; filename=\"{}\"", file_name))
+        Self::with_name("attachment", file_name)
+    }
+
+    fn with_name(kind: &str, file_name: &str) -> Self {
+        let raw_value = format!("{}; filename=\"{}\"", kind, file_name);
+
+        let mut encoded_value = String::new();
+        let line_len = "Content-Disposition: ".len();
+        let mut w = EmailWriter::new(&mut encoded_value, line_len, false);
+        w.write_str(kind).expect("writing `kind` returned an error");
+        w.write_char(';').expect("writing `;` returned an error");
+        w.space();
+
+        email_encoding::headers::rfc2231::encode("filename", file_name, &mut w)
+            .expect("some Write implementation returned an error");
+
+        Self(HeaderValue::dangerous_new_pre_encoded(
+            Self::name(),
+            raw_value,
+            encoded_value,
+        ))
     }
 }
 
@@ -33,11 +59,19 @@ impl Header for ContentDisposition {
     }
 
     fn parse(s: &str) -> Result<Self, BoxError> {
-        Ok(Self(s.into()))
+        match (s.split_once(';'), s) {
+            (_, "inline") => Ok(Self::inline()),
+            (Some((kind @ ("inline" | "attachment"), file_name)), _) => file_name
+                .split_once(" filename=\"")
+                .and_then(|(_, file_name)| file_name.strip_suffix('"'))
+                .map(|file_name| Self::with_name(kind, file_name))
+                .ok_or_else(|| "Unsupported ContentDisposition value".into()),
+            _ => Err("Unsupported ContentDisposition value".into()),
+        }
     }
 
     fn display(&self) -> HeaderValue {
-        HeaderValue::new(Self::name(), self.0.clone())
+        self.0.clone()
     }
 }
 

src/message/header/mod.rs

@@ -275,7 +275,7 @@ impl PartialEq<HeaderName> for &str {
     }
 }
 
-#[derive(Debug, Clone)]
+#[derive(Debug, Clone, PartialEq)]
 pub struct HeaderValue {
     name: HeaderName,
     raw_value: String,
@@ -293,6 +293,18 @@ impl HeaderValue {
             encoded_value,
         }
     }
+
+    pub fn dangerous_new_pre_encoded(
+        name: HeaderName,
+        raw_value: String,
+        encoded_value: String,
+    ) -> Self {
+        Self {
+            name,
+            raw_value,
+            encoded_value,
+        }
+    }
 }
 
 const ENCODING_START_PREFIX: &str = "=?utf-8?b?";