There is an unexploitable buffer overflow in sendmail's test mode (-bt).
This patch also allows one to cause sendmail to drop privileges by
defining _FFR_TESTMODE_DROP_PRIVS in the Makefile.

Apply by doing:
	cd /usr/src
	patch -p0 < 029_sendmail.patch

And then rebuild and install sendmail:
	cd gnu/usr.sbin/sendmail
	make depend
	make
	make install

Index: gnu/usr.sbin/sendmail/sendmail/macro.c
===================================================================
RCS file: /cvs/src/gnu/usr.sbin/sendmail/sendmail/macro.c,v
retrieving revision 1.1.1.1
retrieving revision 1.2
diff -u -r1.1.1.1 -r1.2
--- gnu/usr.sbin/sendmail/sendmail/macro.c	2000/04/02 19:05:45	1.1.1.1
+++ gnu/usr.sbin/sendmail/sendmail/macro.c	2000/10/09 23:45:01	1.2
@@ -377,7 +377,7 @@
 			*ep = p + 1;
 		if (tTd(35, 14))
 			dprintf("%c\n", *p);
-		return *p;
+		return ((unsigned int)*p) & 0xff;
 	}
 	bp = mbuf;
 	while (*++p != '\0' && *p != '}' && bp < &mbuf[sizeof mbuf - 1])
@@ -401,7 +401,7 @@
 	else if (mbuf[1] == '\0')
 	{
 		/* ${x} == $x */
-		mid = mbuf[0];
+		mid = ((unsigned int)mbuf[0]) & 0xff;
 		p++;
 	}
 	else
@@ -428,6 +428,11 @@
 	}
 	if (ep != NULL)
 		*ep = p;
+	if (mid < 0 || mid > MAXMACROID)
+	{
+		syserr("Unable to assign macro/class ID (mid = 0x%x)", mid);
+		mid = 0;
+	}
 	if (tTd(35, 14))
 		dprintf("0x%x\n", mid);
 	return mid;
Index: gnu/usr.sbin/sendmail/sendmail/main.c
===================================================================
RCS file: /cvs/src/gnu/usr.sbin/sendmail/sendmail/main.c,v
retrieving revision 1.2
retrieving revision 1.3
diff -u -r1.2 -r1.3
--- gnu/usr.sbin/sendmail/sendmail/main.c	2000/04/07 19:20:41	1.2
+++ gnu/usr.sbin/sendmail/sendmail/main.c	2000/10/09 23:45:01	1.3
@@ -1517,6 +1517,15 @@
 	{
 		char buf[MAXLINE];
 
+#if _FFR_TESTMODE_DROP_PRIVS
+		dp = drop_privileges(TRUE);
+		if (dp != EX_OK)
+		{
+			CurEnv->e_id = NULL;
+			finis(TRUE, dp);
+		}
+#endif /* _FFR_TESTMODE_DROP_PRIVS */
+
 		if (isatty(fileno(stdin)))
 			Verbose = 2;
 
Index: gnu/usr.sbin/sendmail/sendmail/readcf.c
===================================================================
RCS file: /cvs/src/gnu/usr.sbin/sendmail/sendmail/readcf.c,v
retrieving revision 1.2
retrieving revision 1.3
diff -u -r1.2 -r1.3
--- gnu/usr.sbin/sendmail/sendmail/readcf.c	2000/04/07 19:20:43	1.2
+++ gnu/usr.sbin/sendmail/sendmail/readcf.c	2000/10/09 23:45:01	1.3
@@ -2985,7 +2985,7 @@
 			dprintf("setclass(%s, %s)\n", macname(class), str);
 
 		s = stab(str, ST_CLASS, ST_ENTER);
-		setbitn(class, s->s_class);
+		setbitn(((unsigned int)class) & 0xff, s->s_class);
 	}
 }
 /*
Index: gnu/usr.sbin/sendmail/sendmail/stab.c
===================================================================
RCS file: /cvs/src/gnu/usr.sbin/sendmail/sendmail/stab.c,v
retrieving revision 1.1.1.1
retrieving revision 1.2
diff -u -r1.1.1.1 -r1.2
--- gnu/usr.sbin/sendmail/sendmail/stab.c	2000/04/02 19:05:48	1.1.1.1
+++ gnu/usr.sbin/sendmail/sendmail/stab.c	2000/10/09 23:45:01	1.2
@@ -306,6 +306,7 @@
 	register STAB **shead;
 	register STAB *s;
 
+	dst = ((unsigned int)dst) & 0xff;
 	for (shead = SymTab; shead < &SymTab[STABSIZE]; shead++)
 	{
 		for (s = *shead; s != NULL; s = s->s_next)
Index: gnu/usr.sbin/sendmail/sendmail/Makefile
===================================================================
RCS file: /cvs/src/gnu/usr.sbin/sendmail/sendmail/Makefile,v
retrieving revision 1.6
diff -u -r1.6 Makefile
--- gnu/usr.sbin/sendmail/sendmail/Makefile	2000/04/06 15:45:44	1.6
+++ gnu/usr.sbin/sendmail/sendmail/Makefile	2000/10/09 23:51:01
@@ -5,6 +5,9 @@
 WANT_LIBWRAP=1
 WANT_LIBSMUTIL=1
 
+# To casue sendmail to drop privs in test mode (-bt) uncomment the following
+#ENVDEF+= -D_FFR_TESTMODE_DROP_PRIVS
+
 SRCS=	main.c alias.c arpadate.c bf_torek.c clock.c collect.c \
 	conf.c control.c convtime.c daemon.c deliver.c domain.c \
 	envelope.c err.c headers.c macro.c map.c mci.c milter.c \