[strongSwan] SHA1 vs SHA256

[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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