[Openvpn-devel,1/2,v4] buffer: use memcpy in buf_catrunc

Message ID 20230517113619.82808-1-frank@lichtenheld.com
State Accepted
Headers show
Series [Openvpn-devel,1/2,v4] buffer: use memcpy in buf_catrunc | expand

Commit Message

Frank Lichtenheld May 17, 2023, 11:36 a.m. UTC
Since we use strlen() to determine the length
and then check it ourselves, there is really
no point in using strncpy.

But the compiler might complain that we use
the output of strlen() for the length of
strncpy which is usually a sign for bugs:

error: ‘strncpy’ specified bound depends
 on the length of the source argument

Warning was at least triggered for
mingw-gcc version 10-win32 20220113.

Also change the type of len to size_t
which avoids potential problems with
signed overflow.

 - make len size_t and change code to avoid any theoretical overflows
 - remove useless casts
 - fix off-by-one introduced by v2 %)
 - ignore unsigned overflow to simplify code

Change-Id: If4a67adac4d2e870fd719b58075d39efcd67c671
Signed-off-by: Frank Lichtenheld <frank@lichtenheld.com>
 src/openvpn/buffer.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)


Gert Doering May 17, 2023, 5:16 p.m. UTC | #1
Acked-by: Gert Doering <gert@greenie.muc.de>

Change looks good (less +/-1, so easier for my old brain), and our nice
and shiny new unit test confirms that things still work.

Your patch has been applied to the master branch.

commit c89a97e449baaf60924a362555d35184f188a646
Author: Frank Lichtenheld
Date:   Wed May 17 13:36:19 2023 +0200

     buffer: use memcpy in buf_catrunc

     Signed-off-by: Frank Lichtenheld <frank@lichtenheld.com>
     Acked-by: Gert Doering <gert@greenie.muc.de>
     Message-Id: <20230517113619.82808-1-frank@lichtenheld.com>
     URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg26683.html
     Signed-off-by: Gert Doering <gert@greenie.muc.de>

kind regards,

Gert Doering


diff --git a/src/openvpn/buffer.c b/src/openvpn/buffer.c
index d099795b..7725438e 100644
--- a/src/openvpn/buffer.c
+++ b/src/openvpn/buffer.c
@@ -316,10 +316,10 @@  buf_catrunc(struct buffer *buf, const char *str)
     if (buf_forward_capacity(buf) <= 1)
-        int len = (int) strlen(str) + 1;
+        size_t len = strlen(str) + 1;
         if (len < buf_forward_capacity_total(buf))
-            strncpynt((char *)(buf->data + buf->capacity - len), str, len);
+            memcpy(buf->data + buf->capacity - len, str, len);