From 3bd7fa12e146c6051490d048a4acbfba974eeb04 Mon Sep 17 00:00:00 2001
From: Christian Brabandt <cb@256bit.org>
Date: Mon, 2 Oct 2023 20:59:08 +0200
Subject: [PATCH 2156/2205] patch 9.0.1969: [security] buffer-overflow in
 trunc_string()

Problem:  buffer-overflow in trunc_string()
Solution: Add NULL at end of buffer

Currently trunc_string() assumes that when the string is too long,
buf[e-1] will always be writeable. But that assumption may not always be
true. The condition currently looks like this

    else if (e + 3 < buflen)
    [...]
    else
    {
	// can't fit in the "...", just truncate it
	buf[e - 1] = NUL;
    }

but this means, we may run into the last else clause with e still being
larger than buflen. So a buffer overflow occurs.

So instead of using `buf[e - 1]`, let's just always
truncate at `buf[buflen - 1]` which should always be writable.

Signed-off-by: Christian Brabandt <cb@256bit.org>
---
 src/message.c              | 2 +-
 1 files changed, 1 insertions(+), 1 deletion(-)

diff --git a/src/message.c b/src/message.c
index 2fc6cefa9..83c8b4f4a 100644
--- a/src/message.c
+++ b/src/message.c
@@ -353,7 +353,7 @@ trunc_string(
     else
     {
 	// can't fit in the "...", just truncate it
-	buf[e - 1] = NUL;
+	buf[buflen - 1] = NUL;
     }
 }
 
-- 
2.27.0
