From: Vsevolod Stakhov <vsevolod@rspamd.com>
Date: Mon, 2 Feb 2026 14:27:16 +0000 (+0000)
Subject: [Fix] R_PARTS_DIFFER: handle empty alternative parts
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=e5a8281ab10d81811864379357eadf0cdfcaa373;p=thirdparty%2Frspamd.git

[Fix] R_PARTS_DIFFER: handle empty alternative parts

Previously, R_PARTS_DIFFER only triggered when both text/html and
text/plain parts had content. When one part was empty (e.g., empty
HTML with non-empty plain text), the distance was never calculated.

Now detect when exactly one part is empty and treat it as 100%
difference, which will trigger R_PARTS_DIFFER with maximum score.
---

diff --git a/src/libmime/message.c b/src/libmime/message.c
index 0a7a445a18..8bd2c11b5c 100644
--- a/src/libmime/message.c
+++ b/src/libmime/message.c
@@ -1909,6 +1909,38 @@ void rspamd_message_process(struct rspamd_task *task)
 													NULL);
 					}
 				}
+				else if (IS_TEXT_PART_EMPTY(p1) != IS_TEXT_PART_EMPTY(p2)) {
+					/*
+					 * One part is empty, another is not - this is 100% difference
+					 */
+					struct rspamd_mime_text_part *non_empty =
+						IS_TEXT_PART_EMPTY(p1) ? p2 : p1;
+
+					if (non_empty->normalized_hashes &&
+						non_empty->normalized_hashes->len > 0) {
+						tw = non_empty->normalized_hashes->len;
+
+						msg_debug_task(
+							"one part is empty, another has %d words, "
+							"got diff between parts of 1.0",
+							tw);
+
+						pdiff = rspamd_mempool_alloc(task->task_pool,
+													 sizeof(double));
+						*pdiff = 1.0;
+						rspamd_mempool_set_variable(task->task_pool,
+													"parts_distance",
+													pdiff,
+													NULL);
+						ptw = rspamd_mempool_alloc(task->task_pool,
+												   sizeof(int));
+						*ptw = tw;
+						rspamd_mempool_set_variable(task->task_pool,
+													"total_words",
+													ptw,
+													NULL);
+					}
+				}
 			}
 		}
 		else {