Re: SMTP smuggling with NUL char - m4 option to reject them

On 04/05/2024 17:25, Claus Aßmann wrote:

What's the problem?
 LOCAL_CONFIG
O RejectNUL=true
 

Being relatively new to sendmail configuration myself that had escaped me too.  cf/README does mention it, but it looks so different to most of   the other settings in sendmail.mc.  Embarrassingly I see now that there was already a similar example in sendmal.mc only for LOCAL_NET_CONFIG.  livin' and learnin':
# diff -u sendmail.mc test.mc
--- sendmail.mc 2023-10-17 03:29:33.826913320 -0700
+++ test.mc     2024-05-17 03:12:22.832629965 -0700
@@ -26,5 +26,8 @@
  MAILER(`local')dnl
  MAILER(`smtp')dnl
+LOCAL_CONFIG
+O RejectNUL=true
+
  LOCAL_NET_CONFIG
  R$* < @ $* .$m. > $*   $#esmtp $@ $2.$m $: $1 < @ $2.$m. > $3