[strongSwan] Strongswan internal DNS-resolution

Dusan Ilic dusan at comhem.se
Sun Jul 23 14:45:18 CEST 2017 

One step closer, when adding @ infront of rightid and in ipsec.secrets 
on the remote endpoint I can connect again after running ipsec update, 
before I had to run ipsec restart for the connection to be established 
again. However, that's not optimal, it should be able to take care of 
this on its own without manual intervention. As already said, a 
Fortigate routers IP-sec implementation seem to take care of this 
automatically...

I can see that when the local endpoint changes public IP, ipsec 
statusall shows Tasks active: IKE_DPD for a while, then it takes down 
the SA's and starts trying to reconnect again. However looking at the 
remote endpoint, it still shows the connection as up. When I run ipsec 
down and afterwards ipsec update on the remote endpoint, the connection 
goes up (not without ipsec update, then it reports "no shared key 
foound"). Before that the local endpoint reports the same error as 
before, "no proposal chosen", from the remote endpoint.

Something is not behaving as it should here, according to how it's 
supposed to reading about the prefixes @ and %.

Den 2017-07-23 kl. 00:55, skrev Dusan Ilic:
> I meant this is the new IP (after running "ipsec update"), but 
> ipsec.secrets still refers to the old IP and therefore says no shared 
> key found for the new IP.
>
>
> Den 2017-07-23 kl. 00:51, skrev Dusan Ilic:
>> initiating IKE_SA to 85.24.241.x
>> generating IKE_SA_INIT request 0 [ SA KE No N(NATD_S_IP) N(NATD_D_IP) ]
>> sending packet: from 94.254.123.x[500] to 85.24.241.x[500]
>> received packet: from 85.24.241.x[500] to 94.254.123.x[500]
>> parsed IKE_SA_INIT response 0 [ SA KE No N(NATD_S_IP) N(NATD_D_IP) 
>> CERTREQ N(MULT_AUTH) ]
>> received 1 cert requests for an unknown ca
>> authentication of 'local.hostname' (myself) with pre-shared key
>> no shared key found for 'local.hostname' - '85.24.241.x'
>>
>> 85.24.241.x is old IP of the other peer.
>>
>>
>> Den 2017-07-23 kl. 00:47, skrev Dusan Ilic:
>>> I think the problem is that also ipsec.secrets is resolved to the 
>>> old IP, so the PSK's doesn't match.
>>>
>>> Jul 23 00:44:25 GW pluto[7661]: loading secrets from 
>>> "/etc/ipsec.secrets"
>>> Jul 23 00:44:25 GW pluto[7661]:   loaded PSK secret for 85.24.241.x
>>>
>>> How can I use the % feature in ipsec.secrets?
>>>
>>>
>>> Den 2017-07-22 kl. 21:32, skrev Noel Kuntze:
>>>>
>>>> On 22.07.2017 19:57, Dusan Ilic wrote:
>>>>> Okey, the remote endpoint dont know that the other side have 
>>>>> changed its IP, however according to below a connection should 
>>>>> still be able to be made if the end with the new IP initiates it.
>>>>>
>>>>> "parameter right|leftallowany parameters helps to handle
>>>>> the case where both peers possess dynamic IP addresses that are
>>>>> usually resolved using DynDNS or a similar service.
>>>>>
>>>>> The configuration
>>>>>
>>>>> right=peer.foo.bar <http://peer.foo.bar>
>>>>> rightallowany=yes
>>>>>
>>>>> can be used by the initiator to start up a connection to a peer
>>>>> by resolving peer.foo.bar <http://peer.foo.bar> into the currently 
>>>>> allocated IP address.
>>>>> Thanks to the rightallowany flag the connection behaves later on
>>>>> as
>>>>>
>>>>> right=%any
>>>>>
>>>>> so that the peer can rekey the connection as an initiator when his
>>>>> IP address changes. An alternative notation is
>>>>>
>>>>> right=%peer.foo.bar <http://peer.foo.bar>
>>>>>
>>>>> which will implicitly set rightallowany=yes
>>>>> "
>>>>>
>>>>> However, Strongswan on the side that have changed IP is obviously 
>>>>> aware of its new IP without restarting (how?), so why does it give 
>>>>> the following output when trying to initiate the connection?
>>>>>
>>>>> initiating IKE_SA to 94.254.123 <tel:94.254.123>.x
>>>>> generating IKE_SA_INIT request 0 [ SA KE No N(NATD_S_IP) 
>>>>> N(NATD_D_IP) N(FRAG_SUP) N(HASH_ALG) N(REDIR_SUP) ]
>>>>> sending packet: from 85.24.244 <tel:85.24.244>.x[500] to 
>>>>> 94.254.123 <tel:94.254.123>.x[500] (464 bytes)
>>>>> received packet: from 94.254.123 <tel:94.254.123>.x[500] to 
>>>>> 85.24.244 <tel:85.24.244>.x[500] (36 bytes)
>>>>> parsed IKE_SA_INIT response 0 [ N(NO_PROP) ]
>>>>> received NO_PROPOSAL_CHOSEN notify error
>>>>> establishing connection 'wesafe' failed
>>>> The remote peer sends that error. What does it log?
>>>>
>>>>> Why does it report no proposal chosen, until i restart the remote 
>>>>> endpoint?
>>>>> IF I have understood it right, the use of % in front of the 
>>>>> hostname should allow a connection attempt from whatever the IP 
>>>>> May be?
>>>>>
>>>>> ---- Noel Kuntze skrev ----
>>>>>
>>>>> Seems like it.
>>>>>
>>>>> On 22.07.2017 11:17, Dusan Ilic wrote:
>>>>>> Hi Noel,
>>>>>>
>>>>>> So, are you saying that there is no way to make Strongswan aware 
>>>>>> of a domain name have changed IP-address without restarting it 
>>>>>> manually?
>>>>>>
>>>>>>
>>>>>> Den 2017-07-22 kl. 01:49, skrev Noel Kuntze:
>>>>>>> Hi Dusan,
>>>>>>>
>>>>>>> I took a "quick" look at the code[1] and it seems the DNS names 
>>>>>>> are only resolved once the result replaces the original 
>>>>>>> destination.
>>>>>>> So it has nothing to do with caching. Just with a 
>>>>>>> disadvantageous design decision.
>>>>>>>
>>>>>>> Kind regards
>>>>>>>
>>>>>>> Noel
>>>>>>>
>>>>>>> [1] 
>>>>>>> https://github.com/strongswan/strongswan/blob/master/src/libcharon/sa/ike_sa.c#L1470
>>>>>>>
>>>>>>> On 21.07.2017 00:19, Dusan Ilic wrote:
>>>>>>>> Okey, so I just did a forced release/renew on the same 
>>>>>>>> endpoint, dynamic DNS updated shortly the new IP (ttl 5 min) 
>>>>>>>> and after like 10 min or so another endpoint reconnected again 
>>>>>>>> (a fortigate, I have two endpoints), however the troubling 
>>>>>>>> endpoint (also strongswan) havent connected yet.
>>>>>>>>
>>>>>>>> When logging in to the remote endpoint and pinging the domain 
>>>>>>>> name, it resolves to the new IP, but below are the output from 
>>>>>>>> both sides of the tunnel when trying to manually run ipsec 
>>>>>>>> up-command.
>>>>>>>>
>>>>>>>> On the remote endpoint:
>>>>>>>>
>>>>>>>> First of, running ipsec statusall connection shows as if the 
>>>>>>>> tunnel is still up, maybe thats the problem that Strongswan 
>>>>>>>> thinks its up even if it isn't?
>>>>>>>>
>>>>>>>> ESTABLISHED 46 minutes ago, 
>>>>>>>> 94.254.123.x[local.host.name]...85.24.241.x[85.24.241.x]
>>>>>>>> IKE SPIs: 1dffaab2cafa2f48_i 15e867fa149370f0_r*, pre-shared 
>>>>>>>> key reauthentication in 22 hours
>>>>>>>> IKE proposal: AES_CBC_128/HMAC_SHA1_96/PRF_HMAC_SHA1/MODP_2048
>>>>>>>> INSTALLED, TUNNEL, ESP SPIs: cf0473a2_i c45028cb_o
>>>>>>>> AES_CBC_128/HMAC_SHA1_96, 8275 bytes_i (2616s ago), 81235 
>>>>>>>> bytes_o (8s ago), rekeying in 7 hours
>>>>>>>> 192.168.1.0/24 === 10.1.1.0/26
>>>>>>>>
>>>>>>>> Command ipsec up connection
>>>>>>>>
>>>>>>>> initiating IKE_SA to 85.24.241.x
>>>>>>>> generating IKE_SA_INIT request 0 [ SA KE No N(NATD_S_IP) 
>>>>>>>> N(NATD_D_IP) ]
>>>>>>>> sending packet: from 94.254.123.x[500] to 85.24.241.x[500]
>>>>>>>> retransmit 1 of request with message ID 0
>>>>>>>> sending packet: from 94.254.123.x[500] to 85.24.241.x[500]
>>>>>>>>
>>>>>>>> On the local endpoint (with new IP):
>>>>>>>>
>>>>>>>> initiating IKE_SA to 94.254.123.x
>>>>>>>> generating IKE_SA_INIT request 0 [ SA KE No N(NATD_S_IP) 
>>>>>>>> N(NATD_D_IP) N(FRAG_SUP) N(HASH_ALG) N(REDIR_SUP) ]
>>>>>>>> sending packet: from 85.24.244.x[500] to 94.254.123.x[500] (464 
>>>>>>>> bytes)
>>>>>>>> received packet: from 94.254.123.x[500] to 85.24.244.x[500] (36 
>>>>>>>> bytes)
>>>>>>>> parsed IKE_SA_INIT response 0 [ N(NO_PROP) ]
>>>>>>>> received NO_PROPOSAL_CHOSEN notify error
>>>>>>>> establishing connection 'wesafe' failed
>>>>>>>>
>>>>>>>> And when restarting Strongswan on the remote endpoint, it 
>>>>>>>> connects again...
>>>>>>>>
>>>>>>>> Den 2017-07-20 kl. 12:00, skrev Dusan Ilic:
>>>>>>>>> Hi,
>>>>>>>>>
>>>>>>>>> I have some issues with a site to site tunnel with two dynamic 
>>>>>>>>> endpoints. One side almost never changes IP-adress (it is DHCP 
>>>>>>>>> however), the other side changes more frequently. Both 
>>>>>>>>> endpoints IP-adresses are using dynamic DNS and have a 
>>>>>>>>> corresponding domain name associated at all times.
>>>>>>>>>
>>>>>>>>> Today one side changed IP, and the new IP have been updated in 
>>>>>>>>> public DNS. I understand DNS propagation and caching, but I 
>>>>>>>>> seem to not understand how Strongswan handles and acts upon it.
>>>>>>>>>
>>>>>>>>> For example, I have set keyingtries to %forever on both sides, 
>>>>>>>>> so that they continuesly tries to reconnect when connections 
>>>>>>>>> is lost. I have also changed the global initiation parameter 
>>>>>>>>> from default 0 to 60 s, so that it retries unsuccesful 
>>>>>>>>> connections attempts.
>>>>>>>>> Now the other side is trying to reconnect to the old IP still, 
>>>>>>>>> however if I ping the hostname from that endpoint it resolves 
>>>>>>>>> to the new, correct IP. It seems like Strongswan is caching 
>>>>>>>>> the old DNS some how?
>>>>>>>>> At last I tried to restart Strongswan and then it picked up 
>>>>>>>>> the new IP.
>>>>>>>>>
>>>>>>>>> I would like to have a system that solves this by itself, so I 
>>>>>>>>> don't need to manually have to intervene each and everythime 
>>>>>>>>> any of the endpoints get a new IP. How can this best be achieved?
>>>>>>>>>
>>>
>>
>

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