[strongSwan] Sudden issues with Windows 10 clients

[Christian Salway]

The problem with Windows (10 at least) is that it offers the weakest ciphers first, so you should remove sha1 and 3des.

The minimum proposals you should have and which are compatible with Windows 10, OSX, IOS and Linux are the following.

proposals = aes256-sha256-prfsha256-modp2048-modp1024

Although I would recommend adding the Windows 10 registry key [NegotiateDH2048_AES256] to use strong ciphers and then you can remove MODP1024


 <http://www.naimuri.com/>

> On 7 May 2018, at 15:50, Jafar Al-Gharaibeh <jafar at atcorp.com> wrote:
> 
> Houman,
> 
>   The Windows client proposals do not match your configured proposals. Your Windows client expect DG group 15 (MODP2048), where as you have:
> 
> aes256-3des-sha1-modp1024
> 
> change that to:
> 
> aes256-3des-sha1-modp2048
> 
> I'd also add sha256 at least before sha1 (deemed insecure). If you still have other clients expecting modp1024, make it:
> 
> aes256-3des-sha256-sha1-modp2048-modp1024
> 
> That should get you covered. 
> 
> Regards,
> Jafar
> 
> 
> On 5/7/2018 8:17 AM, Houman wrote:
>> Hello,
>> 
>> Until a week ago a user with Windows 10 had no issue connecting to the StrongSwan server. But now out of the blue, he can't connect to the StrongSwan server anymore.
>> 
>> The log on the server is:
>> 
>> May  7 12:31:06 vpn-p1 charon: 08[IKE] received proposals inacceptable
>> May  7 12:31:06 vpn-p1 charon: 08[ENC] generating IKE_SA_INIT response 0 [ N(NO_PROP) ]
>> May  7 12:31:06 vpn-p1 charon: 08[NET] sending packet: from xxx.x.xx.92[500] to 91.98.xxx.xxx[500] (36 bytes)
>> May  7 12:32:09 vpn-p1 systemd[1]: Started Session 35 of user root.
>> May  7 12:46:21 vpn-p1 systemd[1]: Starting Cleanup of Temporary Directories...
>> May  7 12:46:21 vpn-p1 systemd-tmpfiles[7016]: [/usr/lib/tmpfiles.d/var.conf:14] Duplicate line for path "/var/log", ignoring.
>> May  7 12:46:21 vpn-p1 systemd[1]: Started Cleanup of Temporary Directories.
>> May  7 13:00:13 vpn-p1 systemd[1]: Starting Certbot...
>> May  7 13:00:13 vpn-p1 systemd[1]: Started Certbot.
>> May  7 13:08:20 vpn-p1 systemd[1]: Started Session 36 of user root.
>> May  7 13:11:27 vpn-p1 charon: 12[NET] received packet: from 91.98.xxx.xxx[500] to xxx.x.xx.92[500] (624 bytes)
>> May  7 13:11:27 vpn-p1 charon: 12[ENC] parsed IKE_SA_INIT request 0 [ SA KE No N(NATD_S_IP) N(NATD_D_IP) V V V V ]
>> May  7 13:11:27 vpn-p1 charon: 12[IKE] received MS NT5 ISAKMPOAKLEY v9 vendor ID
>> May  7 13:11:27 vpn-p1 charon: 12[IKE] received MS-Negotiation Discovery Capable vendor ID
>> May  7 13:11:27 vpn-p1 charon: 12[IKE] received Vid-Initial-Contact vendor ID
>> May  7 13:11:27 vpn-p1 charon: 12[ENC] received unknown vendor ID: 01:52:8b:bb:c0:06:96:12:18:49:ab:9a:1c:5b:2a:51:00:00:00:02
>> May  7 13:11:27 vpn-p1 charon: 12[IKE] 91.98.xxx.xxx is initiating an IKE_SA
>> May  7 13:11:27 vpn-p1 charon: 12[CFG] received proposals: IKE:AES_CBC_256/HMAC_SHA1_96/PRF_HMAC_SHA1/MODP_2048, IKE:AES_CBC_256/HMAC_SHA2_256_128/PRF_HMAC_SHA2_256/MODP_2048, IKE:AES_CBC_256/HMAC_SHA2_384_192/PRF_HMAC_SHA2_384/MODP_2048
>> May  7 13:11:27 vpn-p1 charon: 12[CFG] configured proposals: IKE:AES_GCM_16_256/HMAC_SHA2_256_128/PRF_HMAC_SHA2_256/ECP_521, IKE:AES_CBC_256/HMAC_SHA2_256_128/PRF_HMAC_SHA2_256/ECP_384, IKE:AES_CBC_256/3DES_CBC/HMAC_SHA1_96/PRF_HMAC_SHA1/MODP_1024
>> May  7 13:11:27 vpn-p1 charon: 12[IKE] remote host is behind NAT
>> May  7 13:11:27 vpn-p1 charon: 12[IKE] received proposals inacceptable
>> May  7 13:11:27 vpn-p1 charon: 12[ENC] generating IKE_SA_INIT response 0 [ N(NO_PROP) ]
>> May  7 13:11:27 vpn-p1 charon: 12[NET] sending packet: from xxx.x.xx.92[500] to 91.98.xxx.xxx[500] (36 bytes)
>> May  7 13:11:28 vpn-p1 charon: 16[NET] received packet: from 91.98.xxx.xxx[500] to xxx.x.xx.92[500] (624 bytes)
>> May  7 13:11:28 vpn-p1 charon: 16[ENC] parsed IKE_SA_INIT request 0 [ SA KE No N(NATD_S_IP) N(NATD_D_IP) V V V V ]
>> May  7 13:11:28 vpn-p1 charon: 16[IKE] received MS NT5 ISAKMPOAKLEY v9 vendor ID
>> May  7 13:11:28 vpn-p1 charon: 16[IKE] received MS-Negotiation Discovery Capable vendor ID
>> May  7 13:11:28 vpn-p1 charon: 16[IKE] received Vid-Initial-Contact vendor ID
>> May  7 13:11:28 vpn-p1 charon: 16[ENC] received unknown vendor ID: 01:52:8b:bb:c0:06:96:12:18:49:ab:9a:1c:5b:2a:51:00:00:00:02
>> May  7 13:11:28 vpn-p1 charon: 16[IKE] 91.98.xxx.xxx is initiating an IKE_SA
>> May  7 13:11:28 vpn-p1 charon: 16[CFG] received proposals: IKE:AES_CBC_256/HMAC_SHA1_96/PRF_HMAC_SHA1/MODP_2048, IKE:AES_CBC_256/HMAC_SHA2_256_128/PRF_HMAC_SHA2_256/MODP_2048, IKE:AES_CBC_256/HMAC_SHA2_384_192/PRF_HMAC_SHA2_384/MODP_2048
>> May  7 13:11:28 vpn-p1 charon: 16[CFG] configured proposals: IKE:AES_GCM_16_256/HMAC_SHA2_256_128/PRF_HMAC_SHA2_256/ECP_521, IKE:AES_CBC_256/HMAC_SHA2_256_128/PRF_HMAC_SHA2_256/ECP_384, IKE:AES_CBC_256/3DES_CBC/HMAC_SHA1_96/PRF_HMAC_SHA1/MODP_1024
>> May  7 13:11:28 vpn-p1 charon: 16[IKE] remote host is behind NAT
>> May  7 13:11:28 vpn-p1 charon: 16[IKE] received proposals inacceptable
>> May  7 13:11:28 vpn-p1 charon: 16[ENC] generating IKE_SA_INIT response 0 [ N(NO_PROP) ]
>> May  7 13:11:28 vpn-p1 charon: 16[NET] sending packet: from xxx.x.xx.92[500] to 91.98.xxx.xxx[500] (36 bytes)
>> 
>> The Server's ipsec.conf is:
>> 
>> config setup
>>   strictcrlpolicy=yes
>>   uniqueids=never
>> conn roadwarrior
>>   auto=add
>>   compress=no
>>   type=tunnel
>>   keyexchange=ikev2
>>   fragmentation=yes
>>   forceencaps=yes
>>   ike=aes256gcm16-sha256-ecp521,aes256-sha256-ecp384,aes256-3des-sha1-modp1024!
>>   esp=aes256gcm16-sha256,aes256-3des-sha256-sha1!
>>   dpdaction=clear
>>   dpddelay=180s
>>   rekey=no
>>   left=%any
>>   leftid=@${VPNHOST}
>>   leftcert=cert.pem
>>   leftsendcert=always
>>   leftsubnet=0.0.0.0/0 <http://0.0.0.0/0>
>>   right=%any
>>   rightid=%any
>>   rightauth=eap-radius
>>   eap_identity=%any
>>   rightdns=208.67.222.222,208.67.220.220
>>   rightsourceip=${VPNIPPOOL}
>>   rightsendcert=never
>> 
>> Have the supported ike/esp proposals somehow been changed recently after a recent Windows 10 update?
>> 
>> I have made these changes on the Windows 10, after googling for a solution:
>> 
>> - The firewall on Windows 10 is currently disabled.  
>> - I have set NegotiateDH2048_AES256 = 1 in Regedit
>> - AssumeUDPEncapsulationContextOnSendRule = 2 in Regedit
>> 
>> I can't think of anything else I could do on the Windows 10 client.
>> 
>> According to my notes, these are the proposed protocols for Windows 10:
>> 
>> # these ike and esp settings are tested on Mac 10.12, iOS 10 and Windows 10
>> # iOS/Mac with appropriate configuration profiles use AES_GCM_16_256/PRF_HMAC_SHA2_256/ECP_521
>> # Windows 10 uses AES_CBC_256/HMAC_SHA2_256_128/PRF_HMAC_SHA2_256/ECP_384
>> 
>> Is there a website that translates AES_CBC_256/HMAC_SHA2_256_128/PRF_HMAC_SHA2_256/ECP_384 into the right naming for ipsec.conf so that I enter them under ike and esp respectively? I can't quite make out if I have these settings there or not.
>> 
>> If you have any other advice, please help me.
>> 
>> Many Thanks,
>> 
>> 
>> 
>> 
> 

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