[strongSwan] SHA1 vs SHA256

[Noel Kuntze]

Okay. Is kernel-pfkey loaded?

On 04.08.2017 21:31, Dusan Ilic wrote:
> 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?
>>>>>>>>>>>>>
>>>>>>>>>>>>>
> 

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