[Minor] Treat absent Content-Type more wisely

diff --git a/src/libmime/mime_parser.c b/src/libmime/mime_parser.c
index 0d665986745ea35b7331d5f7b32a64e63f52324d..a89b76b3a5c1d7d9a899ab0df1aaf7156be9206b 100644 (file)
--- a/src/libmime/mime_parser.c
+++ b/src/libmime/mime_parser.c
@@ -25,6 +25,7 @@
 #include "contrib/uthash/utlist.h"
 #include <openssl/cms.h>
 #include <openssl/pkcs7.h>
+#include "contrib/fastutf8/fastutf8.h"
 
 struct rspamd_mime_parser_lib_ctx {
        struct rspamd_multipattern *mp_boundary;
@@ -610,8 +611,20 @@ rspamd_mime_parse_normal_part (struct rspamd_task *task,
                                 * In theory, it is very unsafe to process it as a text part
                                 * as we unlikely get some sane result
                                 */
-                               part->ct->flags &= ~RSPAMD_CONTENT_TYPE_TEXT;
-                               part->ct->flags |= RSPAMD_CONTENT_TYPE_BROKEN;
+
+                               /*
+                                * On the other hand, there is an evidence that some
+                                * emails actually rely on that.
+                                * So we apply an expensive hack here:
+                                * if there are no 8bit characters -OR- the content is valid
+                                * UTF8, we can still imply Content-Type == text/plain
+                                */
+
+                               if (rspamd_str_has_8bit (part->raw_data.begin, part->raw_data.len) &&
+                                       !rspamd_fast_utf8_validate (part->raw_data.begin, part->raw_data.len)) {
+                                       part->ct->flags &= ~RSPAMD_CONTENT_TYPE_TEXT;
+                                       part->ct->flags |= RSPAMD_CONTENT_TYPE_BROKEN;
+                               }
                        }
                }