[strongSwan] SHA1 vs SHA256

[Dusan Ilic]

Yep, both endpoints have loaded kernel-netlink.
However, the Strongswan versions is 5.2.2 and the other is 5.5.2.


Den 2017-08-04 kl. 21:15, skrev Noel Kuntze:
> Hi Dusan,
>
> That is unreliable.
> Check the list of loaded plugins in the output of `ipsec stausall` or `swanctl --status`.
>
> Kind regards
>
> Noel
>
> On 04.08.2017 21:11, Dusan Ilic wrote:
>> Hi Noel,
>>
>> I think I'm already using kernel-netlink on both endpoints.
>>
>> cat /etc/strongswan.d/charon/kernel-netlink.conf | grep load
>>      # Whether to load the plugin. Can also be an integer to increase the
>>      load = yes
>>
>>
>> Den 2017-08-04 kl. 21:00, skrev Noel Kuntze:
>>> Hi,
>>>
>>> If the pfkey API (nowadays a wrapper around XFRM) to the kernel is used, SHA-256 with 96 bit truncation is used[1][2]. That is because it is the default truncation length.
>>> It is not possible to choose the truncation length using pfkey.
>>> If XFRM over netlink socket is used to configure XFRM, one can choose the truncation length. strongSwan uses the 128 bit truncation length for HMAC-SHa256.
>>>
>>> Since 5.5.3, one can choose the truncation length on a per-conn basis.
>>>   From the roadmap[3]:
>>>
>>> With the sha256_96 compatibility option it's possible to locally configure 96-bit truncation
>>> for HMAC_SHA256 (the correct truncation is 128 bit) when negotiated using the official
>>> algorithm identifier (12). This is only useful for compatibility with peers that incorrectly
>>> use this shorter truncation as the actual truncation length is not negotiated.
>>>
>>> So the solution is to try using kernel-netlink instead of kernel-pfkey with strongSwan in an attempt to force the kernel to
>>> use the 128 bit truncation length, which strongSwan chooses by default.
>>>
>>> Kind regards
>>>
>>> Noel
>>>
>>> [1] https://wiki.strongswan.org/issues/2301
>>> [2] https://wiki.strongswan.org/issues/2391
>>> [3] https://wiki.strongswan.org/versions/65
>>> On 04.08.2017 20:50, Andreas Steffen wrote:
>>>> Hi Dusan,
>>>>
>>>> the only workaround I see is to either upgrade your Linux 2.6
>>>> kernel or fall back to a SHA-1 based ESP HMAC.
>>>>
>>>> Regards
>>>>
>>>> Andreas
>>>>
>>>> On 04.08.2017 20:46, Dusan Ilic wrote:
>>>>> Hi,
>>>>>
>>>>> Unfortunately, I'm not following you guys :)
>>>>> Could someone please clarify?
>>>>>
>>>>>
>>>>> Den 2017-08-04 kl. 19:04, skrev Noel Kuntze:
>>>>>> Hi,
>>>>>>
>>>>>> IIRC pfkey still uses the old truncation (It's mentioned in some
>>>>>> relatively recent ticket).
>>>>>> Try using kernel-netlink instead.
>>>>>>
>>>>>> Kind regards
>>>>>>
>>>>>> Noel
>>>>>>
>>>>>>
>>>>>> On 04.08.2017 19:02, Andreas Steffen wrote:
>>>>>>> Hi Dusan,
>>>>>>>
>>>>>>> hmmm, our documentation says that the correct ESP SHA256_128 HMAC
>>>>>>> truncation was introduced with the 2.6.33 kernel but your kernel
>>>>>>> might not be a vanilla 2.6.36 kernel:
>>>>>>>
>>>>>>>     https://wiki.strongswan.org/projects/strongswan/wiki/IKEv2CipherSuites
>>>>>>>
>>>>>>>     (ESP integrity algorithm footnote n)
>>>>>>>
>>>>>>> Regards
>>>>>>>
>>>>>>> Andreas
>>>>>>>
>>>>>>> On 04.08.2017 16:41, Dusan Ilic wrote:
>>>>>>>> Hi Andreas
>>>>>>>>
>>>>>>>> One side is 2.6.36 and the other 3.10.20
>>>>>>>>
>>>>>>>>
>>>>>>>> Den 2017-08-04 kl. 12:48, skrev Andreas Steffen:
>>>>>>>>> Hi Dusan,
>>>>>>>>>
>>>>>>>>> this is a Linux kernel issue. Which kernel versions are you running
>>>>>>>>> on the two endpoints?.
>>>>>>>>>
>>>>>>>>> Regards
>>>>>>>>>
>>>>>>>>> Andreas
>>>>>>>>>
>>>>>>>>> On 04.08.2017 12:41, Dusan Ilic wrote:
>>>>>>>>>> Hi Noel,
>>>>>>>>>>
>>>>>>>>>> One side is Strongswan 5.2.2 and the other is 5.5.2.
>>>>>>>>>> How do I switch?
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>> Den 2017-08-04 kl. 12:25, skrev Noel Kuntze:
>>>>>>>>>>> the remote peer probably uses the DRAFT variant of sha2-256, which
>>>>>>>>>>> uses 96 bit truncation. strongSwan uses the actual standardized
>>>>>>>>>>> variant that truncates to 128 bit.
>>>>>>>>>>> You can switch between the two in the newest version of strongSwan
>>>>>>>>>>>
>>>>>>>>>>> On 04.08.2017 12:23, Dusan Ilic wrote:
>>>>>>>>>>>> Hello!
>>>>>>>>>>>>
>>>>>>>>>>>> I have a strange issue, with both settings below the tunnel goes up
>>>>>>>>>>>> as it should, but only with SHA1 in ESP traffic goes through.
>>>>>>>>>>>> When I
>>>>>>>>>>>> ping the remote client with ESP SHA256 it times out, even though
>>>>>>>>>>>> the
>>>>>>>>>>>> tunnel reports as being up by Strongswan.
>>>>>>>>>>>>
>>>>>>>>>>>> Traffic working:
>>>>>>>>>>>>
>>>>>>>>>>>> ike=aes256-sha256-modp2048!
>>>>>>>>>>>> esp=aes128-sha1-modp2048!
>>>>>>>>>>>>
>>>>>>>>>>>> Traffic not working:
>>>>>>>>>>>>
>>>>>>>>>>>> ike=aes256-sha256-modp2048!
>>>>>>>>>>>> esp=aes256-sha256-modp2048!
>>>>>>>>>>>>
>>>>>>>>>>>> Below combo doesn't work either:
>>>>>>>>>>>>
>>>>>>>>>>>> ike=aes256-sha256-modp2048!
>>>>>>>>>>>> esp=aes128-sha256-modp2048!
>>>>>>>>>>>>
>>>>>>>>>>>>
>>>>>>>>>>>> Also, are above settings good? I'm having AES128 on ESP because
>>>>>>>>>>>> with
>>>>>>>>>>>> AES256 I loose too much througput. Do you have any suggestions for
>>>>>>>>>>>> change?
>>>>>>>>>>>>
>>>>>>>>>>>>