fix: infinite loop when decoding invalid 2231 charset

Changelog.md

@@ -40,6 +40,7 @@ Changelog [format](http://keepachangelog.com/en/1.0.0/)
 * Issue causing deadlock when reloading users keys due to double-locking of a mutex.
 * Correctly handle failure to unlock single key.
 * GODT-479 Fix flaky integration tests.
+* GODT-484 Fix infinite loop when decoding invalid 2231 charset
 
 ## [v1.2.7] Donghai-hotfix - beta (2020-05-07)
 

pkg/mime/encoding_test.go

@@ -107,6 +107,11 @@ func TestParseMediaType(t *testing.T) {
 			wantMediaType: "attachment",
 			wantParams:    map[string]string{"filename": "備a忘b錄.m4a", "title": "memorandum"},
 		},
+		"Bad2231EncodingKeepsJustTitle": {
+			arg:           "attachment;\nfilename*=utf-8'%F0%9F%98%81%F0%9F%98%82.txt;\n title=smile",
+			wantMediaType: "attachment",
+			wantParams:    map[string]string{"title": "smile"},
+		},
 	}
 	for name, testData := range testTable {
 		t.Run(name, testData.run)

pkg/mime/mediaType.go

@@ -69,6 +69,7 @@ func changeEncodingAndKeepLastParamDefinition(v string) (out string, err error)
 				charset, _, err := get2231Charset(value)
 				if err != nil {
 					log.Errorln("Filter params:", err)
+					v = rest
 					continue
 				}
 				if charset != "utf-8" && charset != "us-ascii" {