From a29dc514d330f8f544fa4b52f33ae65d92aaf410 Mon Sep 17 00:00:00 2001
From: "B. Petersen" <r10s@b44t.com>
Date: Sun, 15 Nov 2020 17:41:29 +0100
Subject: [PATCH] decode filenames as CHARSET'LANG'test%2E%70%64%66

---
 src/mimeparser.rs | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/src/mimeparser.rs b/src/mimeparser.rs
index 07aa0c34d..b86cf34a7 100644
--- a/src/mimeparser.rs
+++ b/src/mimeparser.rs
@@ -26,6 +26,7 @@ use crate::param::*;
 use crate::peerstate::Peerstate;
 use crate::simplify::*;
 use crate::stock::StockMessage;
+use percent_encoding::percent_decode_str;
 
 /// A parsed MIME message.
 ///
@@ -1302,6 +1303,18 @@ fn get_attachment_filename(mail: &mailparse::ParsedMail) -> Result<Option<String
     let desired_filename =
         desired_filename.or_else(|| mail.ctype.params.get("name").map(|s| s.to_string()));
 
+    // decode filename as CHARSET'LANG'test%2E%70%64%66.
+    // we're always assuming utf-8,
+    // however, due to lossy decoding, the extension is preserved
+    // and things should not be totally bad for other encodings.
+    // we can tweak that when we see sth. else really used in the wild nowadays.
+    let desired_filename = if let Some(name) = desired_filename {
+        let name = name.splitn(3, '\'').last().unwrap().to_string();
+        Some(percent_decode_str(&name).decode_utf8_lossy().to_string())
+    } else {
+        None
+    };
+
     // If there is no filename, but part is an attachment, guess filename
     if ct.disposition == DispositionType::Attachment && desired_filename.is_none() {
         if let Some(subtype) = mail.ctype.mimetype.split('/').nth(1) {