write Content-Disposition->filename* wrt RFC 2231 and RFC 5987, tackles

deltachat#98 and deltachat#162

cmdline/stress.c

@@ -468,6 +468,13 @@ void stress_functions(mrmailbox_t* mailbox)
 		assert( strcmp(buf1, "") == 0 );
 		free(buf1);
 
+		assert(  mr_needs_ext_header("Björn") );
+		assert( !mr_needs_ext_header("Bjoern") );
+		assert( !mr_needs_ext_header("") );
+		assert(  mr_needs_ext_header(" ") );
+		assert(  mr_needs_ext_header("a b") );
+		assert( !mr_needs_ext_header(NULL) );
+
 		buf1 = mr_encode_modified_utf7("Björn Petersen", 1);
 		assert( strcmp(buf1, "Bj&APY-rn_Petersen")==0 );
 		buf2 = mr_decode_modified_utf7(buf1, 1);

src/mrmimefactory.c

@@ -391,20 +391,44 @@ static struct mailmime* build_body_file(const mrmsg_t* msg, const char* base_nam
 	/* create mime part, for Content-Disposition, see RFC 2183.
 	`Content-Disposition: attachment` seems not to make a difference to `Content-Disposition: inline` at least on tested Thunderbird and Gma'l in 2017.
 	But I've heard about problems with inline and outl'k, so we just use the attachment-type until we run into other problems ... */
+	int needs_ext = mr_needs_ext_header(filename_to_send);
+
 	mime_fields = mailmime_fields_new_filename(MAILMIME_DISPOSITION_TYPE_ATTACHMENT,
-		mr_encode_header_words(filename_to_send), MAILMIME_MECHANISM_BASE64);
+		needs_ext? NULL : safe_strdup(filename_to_send), MAILMIME_MECHANISM_BASE64);
 
-	if( ret_file_name_as_sent ) {
-		*ret_file_name_as_sent = safe_strdup(filename_to_send);
+	if( needs_ext ) {
+		for( clistiter* cur1 = clist_begin(mime_fields->fld_list); cur1 != NULL; cur1 = clist_next(cur1) ) {
+			struct mailmime_field* field = (struct mailmime_field*)clist_content(cur1);
+			if( field && field->fld_type == MAILMIME_FIELD_DISPOSITION && field->fld_data.fld_disposition )
+			{
+				struct mailmime_disposition* file_disposition = field->fld_data.fld_disposition;
+				if( file_disposition )
+				{
+					struct mailmime_disposition_parm* parm = mailmime_disposition_parm_new(
+						MAILMIME_DISPOSITION_PARM_PARAMETER, NULL, NULL, NULL, NULL, 0,
+						mailmime_parameter_new(strdup("filename*"), mr_encode_ext_header(filename_to_send)));
+					if( parm ) {
+						clist_append(file_disposition->dsp_parms, parm);
+					}
+				}
+
+				break;
+			}
+		}
 	}
 
 	content = mailmime_content_new_with_str(mimetype);
-	clist_append(content->ct_parameters, mailmime_param_new_with_data("name", (filename_encoded=mr_encode_header_words(filename_to_send))));
+	clist_append(content->ct_parameters, mailmime_param_new_with_data("name",
+			(filename_encoded=mr_encode_header_words(filename_to_send))));
 
 	mime_sub = mailmime_new_empty(content, mime_fields);
 
 	mailmime_set_body_file(mime_sub, safe_strdup(pathNfilename));
 
+	if( ret_file_name_as_sent ) {
+		*ret_file_name_as_sent = safe_strdup(filename_to_send);
+	}
+
 cleanup:
 	free(pathNfilename);
 	free(mimetype);

src/mrmimeparser.c

@@ -1140,13 +1140,12 @@ static int mrmimeparser_add_single_part_if_known(mrmimeparser_t* ths, struct mai
 				or `Content-Disposition: ... filename=...` */
 				mrstrbuilder_t filename_parts;
 				mrstrbuilder_init(&filename_parts, 0);
-				struct mailmime_disposition* file_disposition = NULL; /* must not be free()'d */
 				for( clistiter* cur1 = clist_begin(mime->mm_mime_fields->fld_list); cur1 != NULL; cur1 = clist_next(cur1) )
 				{
 					struct mailmime_field* field = (struct mailmime_field*)clist_content(cur1);
 					if( field && field->fld_type == MAILMIME_FIELD_DISPOSITION && field->fld_data.fld_disposition )
 					{
-						file_disposition = field->fld_data.fld_disposition;
+						struct mailmime_disposition* file_disposition = field->fld_data.fld_disposition;
 						if( file_disposition )
 						{
 							for( clistiter* cur2 = clist_begin(file_disposition->dsp_parms); cur2 != NULL; cur2 = clist_next(cur2) )

src/mrstrencode.c

@@ -751,12 +751,37 @@ char* mr_decode_modified_utf7(const char *to_decode, int change_spaces)
  ******************************************************************************/
 
 
+/**
+ * Check if extended header format is needed for a given string.
+ *
+ * @param to_check Null-terminated UTF-8 string to check.
+ *
+ * @return 0=extended header encoding is not needed,
+ *     1=extended header encoding is needed,
+ *     use mr_encode_ext_header() for this purpose.
+ */
+int mr_needs_ext_header(const char* to_check)
+{
+	if( to_check ) {
+		while( *to_check )
+		{
+			if( !isalnum(*to_check) && *to_check!='-' && *to_check!='_' && *to_check!='.' && *to_check!='~' ) {
+				return 1;
+			}
+			to_check++;
+		}
+	}
+
+	return 0;
+}
+
+
 /**
  * Encode an UTF-8 string to the extended header format.
  *
  * Example: `Björn Petersen` gets encoded to `utf-8''Bj%C3%B6rn%20Petersen`
  *
- * @param to_encode Null-terminated UTF-8 string to encode
+ * @param to_encode Null-terminated UTF-8 string to encode.
  *
  * @return Null-terminated encoded string. Must be free()'d after usage.
  *     Halts the program on memory allocation errors,

src/mrstrencode.h

@@ -36,6 +36,7 @@ char*   mr_decode_header_words    (const char*);
 char*   mr_encode_modified_utf7   (const char*, int change_spaces);
 char*   mr_decode_modified_utf7   (const char*, int change_spaces);
 
+int     mr_needs_ext_header       (const char*);
 char*   mr_encode_ext_header      (const char*);
 char*   mr_decode_ext_header      (const char*);