netdev - Re: [PATCH] netfilter: xt_condition: add security capability support

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Message-ID: <AANLkTi=2H+ytOQU9nC_dRp_GB5Sy1831VY14oW=YSOrG@mail.gmail.com>
Date:	Mon, 23 Aug 2010 21:37:35 +0800
From:	Changli Gao <xiaosuo@...il.com>
To:	luciano.coelho@...ia.com
Cc:	kaber@...sh.net, netfilter-devel@...r.kernel.org,
	netdev@...r.kernel.org, James Morris <jmorris@...ei.org>,
	linux-security-module@...r.kernel.org
Subject: Re: [PATCH] netfilter: xt_condition: add security capability support

On Mon, Aug 23, 2010 at 8:50 PM,  <luciano.coelho@...ia.com> wrote:
> From: Luciano Coelho <luciano.coelho@...ia.com>
>
> Add a module parameter that allows the required security capability to
> change the conditions from userspace to be specified.  By default the
> module will require the CAP_NET_ADMIN capability.
>
> Signed-off-by: Luciano Coelho <luciano.coelho@...ia.com>
> ---
>  net/netfilter/xt_condition.c |   10 ++++++++++
>  1 files changed, 10 insertions(+), 0 deletions(-)
>
> diff --git a/net/netfilter/xt_condition.c b/net/netfilter/xt_condition.c
> index 06205aa..fd279e5 100644
> --- a/net/netfilter/xt_condition.c
> +++ b/net/netfilter/xt_condition.c
> @@ -29,11 +29,13 @@
>  #include <linux/netfilter/xt_condition.h>
>  #include <net/netns/generic.h>
>  #include <asm/uaccess.h>
> +#include <linux/capability.h>
>
>  /* Defaults, these can be overridden on the module command-line. */
>  static unsigned int condition_list_perms = S_IRUGO | S_IWUSR;
>  static unsigned int condition_uid_perms = 0;
>  static unsigned int condition_gid_perms = 0;
> +static unsigned int condition_capabilities = CAP_NET_ADMIN;
>
>  MODULE_AUTHOR("Stephane Ouellette <ouellettes@...eotron.ca>");
>  MODULE_AUTHOR("Massimiliano Hofer <max@...leus.it>");
> @@ -47,6 +49,8 @@ module_param(condition_uid_perms, uint, S_IRUSR | S_IWUSR);
>  MODULE_PARM_DESC(condition_uid_perms, "default user owner of /proc/net/nf_condition/* files");
>  module_param(condition_gid_perms, uint, S_IRUSR | S_IWUSR);
>  MODULE_PARM_DESC(condition_gid_perms, "default group owner of /proc/net/nf_condition/* files");
> +module_param(condition_capabilities, uint, CAP_NET_ADMIN);
> +MODULE_PARM_DESC(condition_capabilities, "default capabilities required to change /proc/net/nf_condition/* files");

It is strange that we set security policy in this way. Maybe the
permission of the proc file is enough in this case.

>  MODULE_ALIAS("ipt_condition");
>  MODULE_ALIAS("ip6t_condition");
>
> @@ -88,6 +92,12 @@ static int condition_proc_write(struct file *file, const char __user *input,
>        char buf[sizeof("+037777777777")];
>        unsigned long long value;
>
> +       if (!capable(condition_capabilities)) {
> +               pr_debug("not enough capabilities (requires %0X)\n",
> +                       condition_capabilities);
> +               return -EPERM;
> +       }
> +
>        if (length == 0)
>                return 0;
>
> --
> 1.7.0.4
>
> --
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-- 
Regards,
Changli Gao(xiaosuo@...il.com)
--
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