From 7a670e9b7a1d55ed170940da1777b32ff42edad2 Mon Sep 17 00:00:00 2001
From: Philippe Antoine <pantoine@oisf.net>
Date: Mon, 16 Feb 2026 09:17:36 +0100
Subject: [PATCH] smtp/mime: avoid quadratic complexity in
 mime_smtp_find_url_strings

Ticket: 8292

When we have buffered something in ctx.decoded_line,
we already looked for '\n' in it, so we do not need to run it again

Otherwise, callers that supply mime_smtp_find_url_strings with
a few bytes at a time without "\n", have a quadratic
complexity

(cherry picked from commit 8bba47aa09cba87f9cb5d34a897b4bcca9a5ad38)
---
 rust/src/mime/smtp.rs | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/rust/src/mime/smtp.rs b/rust/src/mime/smtp.rs
index 10e98d2ff8..ad0ea46d48 100644
--- a/rust/src/mime/smtp.rs
+++ b/rust/src/mime/smtp.rs
@@ -332,7 +332,8 @@ fn mime_smtp_find_url_strings(ctx: &mut MimeStateSMTP, input_new: &[u8]) {
     }
 
     let mut input = input_new;
-    // use previosly buffered beginning of line if any
+    let new_len = input.len();
+    // use previously buffered beginning of line if any
     if !ctx.decoded_line.is_empty() {
         ctx.decoded_line.extend_from_slice(input_new);
         input = &ctx.decoded_line;
@@ -348,7 +349,7 @@ fn mime_smtp_find_url_strings(ctx: &mut MimeStateSMTP, input_new: &[u8]) {
         if !ctx.decoded_line.is_empty() {
             ctx.decoded_line.clear()
         }
-    } else if let Some(x) = input.iter().rev().position(|&x| x == b'\n') {
+    } else if let Some(x) = input.iter().rev().take(new_len).position(|&x| x == b'\n') {
         input = &input[..x];
         mime_smtp_extract_urls(&mut ctx.urls, input);
         if !ctx.decoded_line.is_empty() {