From 4d827f0d75a53d3952288ab882efbddea7ffadfe Mon Sep 17 00:00:00 2001
From: "djm@openbsd.org" <djm@openbsd.org>
Date: Tue, 4 Apr 2017 00:24:56 +0000
Subject: [PATCH] upstream commit

disallow creation (of empty files) in read-only mode;
reported by Michal Zalewski, feedback & ok deraadt@

Upstream-ID: 5d9c8f2fa8511d4ecf95322994ffe73e9283899b
---
 sftp-server.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/sftp-server.c b/sftp-server.c
index 3619cdfc0..df0fb5068 100644
--- a/sftp-server.c
+++ b/sftp-server.c
@@ -678,8 +678,8 @@ process_open(u_int32_t id)
 	logit("open \"%s\" flags %s mode 0%o",
 	    name, string_from_portable(pflags), mode);
 	if (readonly &&
-	    ((flags & O_ACCMODE) == O_WRONLY ||
-	    (flags & O_ACCMODE) == O_RDWR)) {
+	    ((flags & O_ACCMODE) != O_RDONLY ||
+	    (flags & (O_CREAT|O_TRUNC)) != 0)) {
 		verbose("Refusing open request in read-only mode");
 	  	status = SSH2_FX_PERMISSION_DENIED;
 	} else {