From: Ding Tianhong <dingtianhong@huawei•com>
To: "David S. Miller" <davem@davemloft•net>,
Alexey Kuznetsov <kuznet@ms2•inr.ac.ru>,
James Morris <jmorris@namei•org>,
Hideaki YOSHIFUJI <yoshfuji@linux-ipv6•org>,
Patrick McHardy <kaber@trash•net>,
Jon Maloy <jon.maloy@ericsson•com>,
Eric Dumazet <edumazet@google•com>,
Netdev <netdev@vger•kernel.org>, <kargig@void•gr>,
<ppandit@redhat•com>
Subject: Re: [PATCH 1/3 v4] ipv6: do not disable temp_address when reaching max_address
Date: Thu, 15 Aug 2013 10:16:51 +0800 [thread overview]
Message-ID: <520C3A13.3060106@huawei.com> (raw)
In-Reply-To: <20130815012457.GD13066@order.stressinduktion.org>
On 2013/8/15 9:24, Hannes Frederic Sowa wrote:
> On Thu, Aug 15, 2013 at 08:43:06AM +0800, Ding Tianhong wrote:
>> On 2013/8/14 18:15, Hannes Frederic Sowa wrote:
>>> On Wed, Aug 14, 2013 at 05:06:54PM +0800, Ding Tianhong wrote:
>>>> A LAN user can remotely disable temporary address which may lead
>>>> to privacy violatins and information disclosure.
>>>>
>>>> The reason is that the linux kernel uses the 'ipv6.max_addresses'
>>>> option to specify how many ipv6 addresses and interface may have.
>>>> The 'ipv6.regen_max_retry' (default value 3) option specifies
>>>> how many times the kernel will try to create a new address.
>>>>
>>>> But the kernel is not distinguish between the event of reaching
>>>> max_addresses for an interface and failing to generate a new address.
>>>> the kernel disable the temporary address after regenerate a new
>>>> address 'regen_max_retry' times.
>>>>
>>>> According RFC4941 3.3.7:
>>>>
>>>> ---------------------------------------
>>>>
>>>> If DAD indicates the address is already in use,
>>>> the node must generate a new randomized interface
>>>> identifier as described in section 3.2 above, and
>>>> repeat the previous steps as appropriate up to
>>>> TEMP_IDGEN_RETRIES times.
>>>>
>>>> If after TEMP_IDGEN_RETRIES consecutive attempts no
>>>> non-unique address was generated, the node must log
>>>> a system error and must not attempt to generate
>>>> temporary address for that interface.
>>>>
>>>> ------------------------------------------
>>>>
>>>> RFC4941 3.3.7 specifies that disabling the temp_address must happen
>>>> upon the address is already in use, not reach the max_address,
>>>> So we have to check the return err and distinguish the correct retry path.
>>>>
>>>> This fixes CVE-2013-0343
>>>
>>> I don't think this patch fixes CVE-2013-0343.
>>>
>>>>
>>>> Signed-off-by: Ding Tianhong <dingtianhong@huawei•com>
>>>> Tested-by: Wang Weidong <wangweidong1@huawei•com>
>>>> Cc: David S. Miller <davem@davemloft•net>
>>>> Cc: Sergei Shtylyov <sergei.shtylyov@cogentembedded•com>
>>>> Cc: Eric Dumazet <edumazet@google•com>
>>>> ---
>>>> net/ipv6/addrconf.c | 26 ++++++++++++++++++++++----
>>>> 1 file changed, 22 insertions(+), 4 deletions(-)
>>>>
>>>> diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
>>>> index da4241c..7b55464 100644
>>>> --- a/net/ipv6/addrconf.c
>>>> +++ b/net/ipv6/addrconf.c
>>>> @@ -1134,10 +1134,28 @@ retry:
>>>> if (IS_ERR_OR_NULL(ift)) {
>>>> in6_ifa_put(ifp);
>>>> in6_dev_put(idev);
>>>> - pr_info("%s: retry temporary address regeneration\n", __func__);
>>>> - tmpaddr = &addr;
>>>> - write_lock(&idev->lock);
>>>> - goto retry;
>>>> +
>>>> + /* According RFC4941 3.3.7:
>>>> + * If DAD indicates the address is already in use,
>>>> + * the node must generate a new randomized interface
>>>> + * identifier as described in section 3.2 above, and
>>>> + * repeat the previous steps as appropriate up to
>>>> + * TEMP_IDGEN_RETRIES times.
>>>> + * If after TEMP_IDGEN_RETRIES consecutive attempts no
>>>> + * non-unique address was generated, the node must log
>>>> + * a system error and must not attempt to generate
>>>> + * temporary address for that interface.
>>>> + * So we have to check the return err and distinguish
>>>> + * the correct retry path.
>>>> + */
>>>> + if (PTR_ERR(ift) == -EEXIST) {
>>>
>>> -EEXIST is not the same as "ipv6 address is is already used on the
>>> subnet". I really don't see the point here. IMHO this breaks the intended
>>> regeneration logic.
>>>
>>> I fear a fix of CVE-2013-0343 will be a bit more complicated. ;) I give it a
>>> thought.
>>>
>>> Greetings,
>>>
>>> Hannes
>>>
>>>
>> ok, thanks for your feedback, I'll waiting you for more information to fix the problem.:)
>
> [added George Kargiotakis and P J P to Cc and full quote]
>
> I wonder if the easiest solution would be to just drop the max_addresses
> limit from ipv6_create_tempaddr. max_addresses protects the kernel from
> installing an unlimited amount of addresses on an interface which gets flooded
> by RAs. Because we have a direct relation between interface address to temp
> address, I don't see that we would create the possiblity of DoS.
>
> Sure, an audit and testing is needed.
>
> Greetings,
>
> Hannes
>
I am afraid that if remove the max limit from the ipv6_create_tempaddr, the tool flood_route26 attack will create huge address to the temp_list, it will be a huge list,
may it destroy something or not?
Best regards
Ding Tianhong
> --
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>
> .
>
next prev parent reply other threads:[~2013-08-15 2:17 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-08-14 9:06 [PATCH 1/3 v4] ipv6: do not disable temp_address when reaching max_address Ding Tianhong
2013-08-14 10:15 ` Hannes Frederic Sowa
2013-08-15 0:43 ` Ding Tianhong
2013-08-15 1:24 ` Hannes Frederic Sowa
2013-08-15 2:16 ` Ding Tianhong [this message]
2013-08-15 17:36 ` Hannes Frederic Sowa
2013-08-15 19:07 ` Hannes Frederic Sowa
2013-08-16 0:48 ` Ding Tianhong
2013-08-16 11:07 ` Hannes Frederic Sowa
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