[PATCH 1/2] ipv6: do not disable temp_address when reaching max_address

[PATCH 1/2] ipv6: do not disable temp_address when reaching max_address

[Ding Tianhong]

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

Signed-off-by: Ding Tianhong <dingtianhong@huawei.com>
Tested-by: Wang Weidong <wangweidong1@huawei.com>
Cc: David S. Miller <davem@davemloft.net>
---
 net/ipv6/addrconf.c | 25 +++++++++++++++++++++----
 1 file changed, 21 insertions(+), 4 deletions(-)

diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index da4241c..99f9fd5 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -1134,10 +1134,27 @@ 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) {
+			pr_info("%s: retry temporary address regeneration\n", __func__);
+			tmpaddr = &addr;
+			write_lock(&idev->lock);
+			goto retry;
+		} else
+			goto out;
 	}
 
 	spin_lock_bh(&ift->lock);
-- 
1.8.2.1

Re: [PATCH 1/2] ipv6: do not disable temp_address when reaching max_address

[Sergei Shtylyov]

Hello.

On 08/13/2013 10:14 AM, 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

> Signed-off-by: Ding Tianhong <dingtianhong@huawei.com>
> Tested-by: Wang Weidong <wangweidong1@huawei.com>
> Cc: David S. Miller <davem@davemloft.net>
> ---
>   net/ipv6/addrconf.c | 25 +++++++++++++++++++++----
>   1 file changed, 21 insertions(+), 4 deletions(-)

> diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
> index da4241c..99f9fd5 100644
> --- a/net/ipv6/addrconf.c
> +++ b/net/ipv6/addrconf.c
> @@ -1134,10 +1134,27 @@ retry:
[...]
> +		if (PTR_ERR(ift) == -EEXIST) {
> +			pr_info("%s: retry temporary address regeneration\n", __func__);
> +			tmpaddr = &addr;
> +			write_lock(&idev->lock);
> +			goto retry;
> +		} else
> +			goto out;

    According to CodingStyle, both arms of the *if* statement should have {} 
if one has it.

WBR, Sergei

Re: [PATCH 1/2] ipv6: do not disable temp_address when reaching max_address

[Ding Tianhong]

On 2013/8/13 22:31, Sergei Shtylyov wrote:
> Hello.
> 
> On 08/13/2013 10:14 AM, 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
> 
>> Signed-off-by: Ding Tianhong <dingtianhong@huawei.com>
>> Tested-by: Wang Weidong <wangweidong1@huawei.com>
>> Cc: David S. Miller <davem@davemloft.net>
>> ---
>>   net/ipv6/addrconf.c | 25 +++++++++++++++++++++----
>>   1 file changed, 21 insertions(+), 4 deletions(-)
> 
>> diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
>> index da4241c..99f9fd5 100644
>> --- a/net/ipv6/addrconf.c
>> +++ b/net/ipv6/addrconf.c
>> @@ -1134,10 +1134,27 @@ retry:
> [...]
>> +        if (PTR_ERR(ift) == -EEXIST) {
>> +            pr_info("%s: retry temporary address regeneration\n", __func__);
>> +            tmpaddr = &addr;
>> +            write_lock(&idev->lock);
>> +            goto retry;
>> +        } else
>> +            goto out;
> 
>    According to CodingStyle, both arms of the *if* statement should have {} if one has it.
> 
> WBR, Sergei
> 

thanks your opinion. I will collect feedback and resend v3 for the patch set.

regards
Ding Tianhong

> 
> .
>