From ca6bb5d7ab22ac79f608fe6cbc6b12de6a5a19f0 Mon Sep 17 00:00:00 2001
From: David Woodhouse <dwmw2@infradead.org>
Date: Thu, 22 Jun 2006 16:07:52 -0700
Subject: [PATCH] [NET]: Require CAP_NET_ADMIN to create tuntap devices.
The tuntap driver allows an admin to create persistent devices and
assign ownership of them to individual users. Unfortunately, relaxing
the permissions on the /dev/net/tun device node so that they can
actually use those devices will _also_ allow those users to create
arbitrary new devices of their own. This patch corrects that, and
adjusts the recommended permissions for the device node accordingly.
Signed-off-By: David Woodhouse <dwmw2@infradead.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
---
Documentation/networking/tuntap.txt | 11 +++++++----
drivers/net/tun.c | 3 +++
2 files changed, 10 insertions(+), 4 deletions(-)
diff --git a/Documentation/networking/tuntap.txt b/Documentation/networking/tuntap.txt
index 76750fb9151a..839cbb71388b 100644
--- a/Documentation/networking/tuntap.txt
+++ b/Documentation/networking/tuntap.txt
@@ -39,10 +39,13 @@ Copyright (C) 1999-2000 Maxim Krasnyansky <max_mk@yahoo.com>
mknod /dev/net/tun c 10 200
Set permissions:
- e.g. chmod 0700 /dev/net/tun
- if you want the device only accessible by root. Giving regular users the
- right to assign network devices is NOT a good idea. Users could assign
- bogus network interfaces to trick firewalls or administrators.
+ e.g. chmod 0666 /dev/net/tun
+ There's no harm in allowing the device to be accessible by non-root users,
+ since CAP_NET_ADMIN is required for creating network devices or for
+ connecting to network devices which aren't owned by the user in question.
+ If you want to create persistent devices and give ownership of them to
+ unprivileged users, then you need the /dev/net/tun device to be usable by
+ those users.
Driver module autoloading
diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index a1ed2d983740..6c62d5c88268 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -490,6 +490,9 @@ static int tun_set_iff(struct file *file, struct ifreq *ifr)
err = -EINVAL;
+ if (!capable(CAP_NET_ADMIN))
+ return -EPERM;
+
/* Set dev type */
if (ifr->ifr_flags & IFF_TUN) {
/* TUN device */
--
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