[strongSwan] make_before_break and rekeying

[Volodymyr Litovka]

Hi colleagues,

struggling with the following problem: it seems, that make_before_break
do not process, first closing an existing SA and then negotiating new one:

Responder side logs:

charon-systemd[64387]: closing CHILD_SA pskv2-gagarin-child{17} with SPIs c9c1dc8e_i (76 bytes) c18d0c57_o (0 bytes) and TS 0.0.0.0/0 === 0.0.0.0/0
charon-systemd[64387]: looking for a child config for 0.0.0.0/0 === 0.0.0.0/0
charon-systemd[64387]: proposing traffic selectors for us:
charon-systemd[64387]:  0.0.0.0/0
charon-systemd[64387]: proposing traffic selectors for other:
charon-systemd[64387]:  0.0.0.0/0
charon-systemd[64387]:   candidate "pskv2-gagarin-child" with prio 5+5
charon-systemd[64387]: found matching child config "pskv2-gagarin-child" with prio 10
charon-systemd[64387]: selecting proposal:
charon-systemd[64387]:   no acceptable ENCRYPTION_ALGORITHM found
charon-systemd[64387]: selecting proposal:
charon-systemd[64387]:   proposal matches
charon-systemd[64387]: received proposals: ESP:AES_CBC_256/HMAC_SHA2_256_128/MODP_2048/NO_EXT_SEQ
charon-systemd[64387]: configured proposals: ESP:AES_GCM_16_128/AES_GCM_16_192/AES_GCM_16_256/MODP_2048/NO_EXT_SEQ, ESP:AES_CBC_128/AES_CBC_192/AES_CBC_256/HMAC_SHA2_256_128/MODP_2048/NO_EXT_SEQ, ESP:AES_CBC_256/AES_CBC_128/HMAC_SHA1_96/MODP_2048/NO_EXT_SEQ
charon-systemd[64387]: selected proposal: ESP:AES_CBC_256/HMAC_SHA2_256_128/MODP_2048/NO_EXT_SEQ
charon-systemd[64387]: selecting traffic selectors for us:
charon-systemd[64387]:  config: 0.0.0.0/0, received: 0.0.0.0/0 => match: 0.0.0.0/0
charon-systemd[64387]: selecting traffic selectors for other:
charon-systemd[64387]:  config: 0.0.0.0/0, received: 0.0.0.0/0 => match: 0.0.0.0/0
charon-systemd[64387]: CHILD_SA pskv2-gagarin-child{18} established with SPIs cc453b50_i c90dfc6a_o and TS 0.0.0.0/0 === 0.0.0.0/0

Caller side logs:

daemon.info : 13[IKE] closing expired CHILD_SA rc{64} with SPIs ca657ea2_i c31bd2d9_o and TS 0.0.0.0/0 === 0.0.0.0/0
daemon.info : 13[IKE] sending DELETE for ESP CHILD_SA with SPI ca657ea2
daemon.info : 13[IKE] scheduling CHILD_SA recreate after hard expire
daemon.info : 12[IKE] received DELETE for ESP CHILD_SA with SPI c31bd2d9
daemon.info : 12[IKE] CHILD_SA closed
daemon.info : 11[IKE] establishing CHILD_SA rc{65}
daemon.info : 06[IKE] CHILD_SA rc{65} established with SPIs cbe0669e_i c2e841a2_o and TS 0.0.0.0/0 === 0.0.0.0/0

there are two strongSwans which configured in the following way:

Responder (swanctl):

charon.make_before_break = yes

swanctl.conf:

conn-defaults {
         version = 2
         proposals = [ ... ]
         local_addrs = [ ... ]
         encap = yes
         fragmentation = yes
         mobike = no
         send_certreq = yes
         send_cert = always
         rekey_time = 3h
}

child-defaults {
         ah_proposals =
         local_ts = 0.0.0.0/0
         rekey_time = 2h
         mode = tunnel
         dpd_action = clear
         ipcomp = no
         tfc_padding = 256
}

child-cipher-pfs {
         esp_proposals = aes128gcm16-aes192gcm16-aes256gcm16-modp2048, aes128-aes192-aes256-sha256-modp2048
}

pskv2-gagarin: conn-defaults {
         remote_addrs = %any
         unique = never
         local {
                 auth = psk
                 id = fqdn:gagarin
         }
         remote {
                 auth = psk
                 id = fqdn:gagarin
         }
         children {
                 pskv2-gagarin-child: child-defaults, child-cipher-pfs {
                         remote_ts = 0.0.0.0/0
                         if_id_in = 3
                         if_id_out = 3
                         updown = /etc/swanctl/bin/xfrm-updown
                 }
         }
}


Caller (ipsec):

charon.make_before_break = yes

ipsec.conf:

conn rc
         keyexchange = ikev2
         auto = add
         closeaction = restart
         dpdaction = restart
         dpddelay = 15s
         keyingtries = %forever
         compress = no
         forceencaps = yes
         fragmentation = yes
         esp = aes256-sha256-modp2048!
         ike = aes256-sha256-modp2048!
         type = tunnel
         mark = 1
	# 1m just for debugging purposes
	lifetime = 1m
         reauth = no
         # we are
         left = %defaultroute
         leftauth = psk
         leftid = gagarin
         leftsubnet = 0.0.0.0/0
         leftupdown = /etc/ipsec.updown
         # server
         right = [ ... ]
         rightauth = psk
         rightid = gagarin
         rightsubnet = 0.0.0.0/0

Two questions:

- what is wrong with make_before_break, why it (according to logs)
closes and then creates new SA?
- what does it mean "no acceptable ENCRYPTION_ALGORITHM found" on
responder side during SA renegotiation?

Thank you.

--
Volodymyr Litovka
   "Vision without Execution is Hallucination." -- Thomas Edison

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