[strongSwan] IKE signature scheme RSA_EMSA_PKCS1_SHA1 not acceptable

[Jafar Al-Gharaibeh]

Binarus,

     Obviously the client proposal doesn't match what your server expect 
regardless of what you think has changed or not changed.
   To debug this better increase your logging level bu adding the 
following under your config setup section:

charondebug="ike 3, net 3, mgr 3, esp 3, chd 3, dmn 3, cfg 3"

   That would allow you to see more information about the exchange.

--Jafar




On 08/18/2018 10:26 AM, Binarus wrote:
> Dear all,
>
> I am getting the error message mentioned above when trying to connect to
> a client's site. Of course, I have tried to research if there already
> has been a similar problem, and have found exactly one appropriate thread:
>
> https://lists.strongswan.org/pipermail/users/2018-March/012351.html
>
> Unfortunately, my situation is different; in my case, something else
> seems to cause the problem. Having said this:
>
> - It happened after the upgrade from Debian jessie (Debian 8) to Debian
> stretch (Debian 9), i.e. after the upgrade from StrongSwan 5.2.1 to
> StrongSwan 5.5.1)
>
> - I definitely have copied the whole configuration (including
> certificates and so on) from the old system to the new one (AFTER having
> installed the new StrongSwan version in the new system). I have double
> checked multiple times (applying different methods) that nothing is missing.
>
> - With the old system, I definitely could connect to the client's site
> without any problem with exact that configuration.
>
> If it matters, the VPN Gateway at the client's side is a Lancom router
> (I don't know the exact type, but it is newer one, and I am absolutely
> sure that they didn't any changes to it while I was upgrading my system,
> and to stress it again, the old system / StrongSwan version could
> connect to that device without problems).
>
> This is my /etc/ipsec.conf (sensitive data has been changed, and lines
> which are commented out have been left away):
>
>
> config setup
>
> conn %default
>    mobike=no
>
> conn myclient
>    ikelifetime=10800s
>    keylife=3600s
>    rekeymargin=9m
>    keyingtries=1
>    type=tunnel
>    keyexchange=ikev2
>    mobike=no
>    ike=aes256-sha512-modp4096!
>    esp=aes256-sha512-modp4096!
>    left=xxxxxxxxxxxxxxxx.hopto.org
>    leftauth=rsa-4096-sha512
>    leftid="/CN=xxxxxxxxxxxxxxxx.hopto.org"
>    leftsubnet=192.168.20.0/24
>    leftfirewall=no
>    leftcert=mycompany-client.crt
>    right=yyyyyyyyyyyyyyyy.zapto.org
>    rightauth=rsa-4096-sha512
>    rightid="/CN=yyyyyyyyyyyyyyyy.zapto.org"
>    rightsubnet=192.168.0.0/24
>    auto=add
>
>
> This is the error message (sensitive data changed in the same way as
> with ipsec.conf):
>
> root at charon:/etc# /etc/init.d/ipsec restart
> [ ok ] Restarting ipsec (via systemctl): ipsec.service.
> root at charon:/etc# ipsec up myclient
> initiating IKE_SA myclient[3] to 79.192.42.125
> 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 87.185.83.87[500] to 79.192.42.125[500] (714 bytes)
> received packet: from 79.192.42.125[500] to 87.185.83.87[500] (713 bytes)
> parsed IKE_SA_INIT response 0 [ SA KE No N(NATD_S_IP) N(NATD_D_IP) CERTREQ ]
> received 1 cert requests for an unknown ca
> sending cert request for "CN=ca.clientsite.local"
> authentication of 'CN=xxxxxxxxxxxxxxxx.hopto.org' (myself) with RSA
> signature successful
> sending end entity cert "CN=xxxxxxxxxxxxxxxx.hopto.org"
> establishing CHILD_SA myclient
> generating IKE_AUTH request 1 [ IDi CERT N(INIT_CONTACT) CERTREQ IDr
> AUTH SA TSi TSr N(EAP_ONLY) ]
> sending packet: from 87.185.83.87[500] to 79.192.42.125[500] (2048 bytes)
> received packet: from 79.192.42.125[500] to 87.185.83.87[500] (1984 bytes)
> parsed IKE_AUTH response 1 [ IDr CERT AUTH TSi TSr N(INIT_CONTACT) SA ]
> received end entity cert "CN=yyyyyyyyyyyyyyyy.zapto.org"
>    using certificate "CN=yyyyyyyyyyyyyyyy.zapto.org"
>    using trusted ca certificate "CN=ca.clientsite.local"
> checking certificate status of "CN=yyyyyyyyyyyyyyyy.zapto.org"
> certificate status is not available
>    reached self-signed root ca with a path length of 0
> authentication of 'CN=yyyyyyyyyyyyyyyy.zapto.org' with RSA signature
> successful
> IKE signature scheme RSA_EMSA_PKCS1_SHA1 not acceptable
> selected peer config 'myclient' inacceptable: constraint checking failed
> no alternative config found
> generating INFORMATIONAL request 2 [ N(AUTH_FAILED) ]
> sending packet: from 87.185.83.87[500] to 79.192.42.125[500] (96 bytes)
> establishing connection 'myclient' failed
> root at charon:/etc#
>
>
> Does anybody have an idea?
>
> Thank you very much in advance,
>
> Binarus
>
>