From ca6bb5d7ab22ac79f608fe6cbc6b12de6a5a19f0 Mon Sep 17 00:00:00 2001 From: David Woodhouse 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 Signed-off-by: David S. Miller --- 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 76750fb915..839cbb7138 100644 --- a/Documentation/networking/tuntap.txt +++ b/Documentation/networking/tuntap.txt @@ -39,10 +39,13 @@ Copyright (C) 1999-2000 Maxim Krasnyansky 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 a1ed2d9837..6c62d5c882 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 */ -- 2.39.5