From 89b9f42f7f56a97c16834c65a768c7817bc36114 Mon Sep 17 00:00:00 2001
From: Aaron Campbell <aaron@cvs.openbsd.org>
Date: Thu, 19 Oct 2000 18:18:55 +0000
Subject: Put the fmt strings CAVEATS section into userland printf(1) man page,
 too; it applies here as well.

---
 usr.bin/printf/printf.1 | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

(limited to 'usr.bin')

diff --git a/usr.bin/printf/printf.1 b/usr.bin/printf/printf.1
index c63bb3baffa..7dd31b6eda1 100644
--- a/usr.bin/printf/printf.1
+++ b/usr.bin/printf/printf.1
@@ -1,4 +1,4 @@
-.\"	$OpenBSD: printf.1,v 1.11 2000/03/23 21:10:18 aaron Exp $
+.\"	$OpenBSD: printf.1,v 1.12 2000/10/19 18:18:54 aaron Exp $
 .\"
 .\" Copyright (c) 1989, 1990 The Regents of the University of California.
 .\" All rights reserved.
@@ -316,6 +316,17 @@ The
 .Nm
 command appeared in
 .Bx 4.3 Reno .
+.Sh CAVEATS
+It is important to never pass a string with user-supplied data as a
+format without using
+.Ql %s .
+An attacker can put format specifiers in the string to mangle your stack,
+leading to a possible security hole.
+.Pp
+Be sure to always use the proper secure idiom:
+.Bd -literal -offset indent
+printf "%s" "$STRING"
+.Ed
 .Sh BUGS
 Since arguments are translated from
 .Tn ASCII
-- 
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