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parsecpython
Asked: 2018-03-23 05:29:17 +0800 CST

Strongswan to Cisco ASA with multiple right subnet

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I've got an ikev2 tunnel up, initiated on the left from an ubuntu box with strongswan going to a cisco asa. Using ASA to ASA multiple networks work but I can not get it with strongswan.

#config setup
    # strictcrlpolicy=yes
    # uniqueids = no
config setup
    charondebug="all"
    uniqueids=yes
    strictcrlpolicy=yes
# Add connections here.
conn host2
    left=8.8.8.8 #Changed from real for this example
    leftsubnet=172.27.1.0/20
    right=8.8.4.4 # changed
    rightsubnet=192.168.1.0/24,192.168.2.0/24
    ike=aes256-sha512-modp2048s256
    esp=aes256-sha512
    keyingtries=0
    ikelifetime=1h
    lifetime=8h
    dpddelay=30
    dpdtimeout=120
    dpdaction=restart
    authby=secret
    auto=add
    keyexchange=ikev2
    type=tunnel

after connecting: ip xfm policy

src 192.168.1.0/24 dst 8.8.8.8/32
    dir fwd priority 185664
    tmpl src 4.4.4.4 dst 8.8.8.8
        proto esp reqid 1 mode tunnel
src 192.168.1.0/24 dst 8.8.8.8/32
    dir in priority 185664
    tmpl src 4.4.4.4 dst 8.8.8.8
        proto esp reqid 1 mode tunnel
src 8.8.8.8/32 dst 192.168.1.0/24
    dir out priority 185664
    tmpl src 8.8.8.8 dst 4.4.4.4
        proto esp reqid 1 mode tunnel
src 0.0.0.0/0 dst 0.0.0.0/0
    socket in priority 0
src 0.0.0.0/0 dst 0.0.0.0/0
    socket out priority 0
src 0.0.0.0/0 dst 0.0.0.0/0
    socket in priority 0
src 0.0.0.0/0 dst 0.0.0.0/0
    socket out priority 0
src ::/0 dst ::/0
    socket in priority 0
src ::/0 dst ::/0
    socket out priority 0
src ::/0 dst ::/0
    socket in priority 0
src ::/0 dst ::/0
    socket out priority 0


$ipsec statusall
Status of IKE charon daemon (strongSwan 5.5.1, Linux 4.13.0-37-generic, x86_64):
  uptime: 119 seconds, since Mar 23 09:08:33 2018
  malloc: sbrk 2297856, mmap 532480, used 1224384, free 1073472
  worker threads: 11 of 16 idle, 5/0/0/0 working, job queue: 0/0/0/0, scheduled: 2
  loaded plugins: charon test-vectors unbound ldap pkcs11 aes rc2 sha2 sha1 md4 md5 mgf1 rdrand random nonce x509 revocation constraints acert pubkey pkcs1 pkcs7 pkcs8 pkcs12 pgp dnskey sshkey dnscert ipseckey pem gcrypt af-alg fips-prf gmp chapoly xcbc cmac hmac ctr ccm ntru bliss curl soup mysql sqlite attr kernel-netlink resolve socket-default farp stroke updown eap-identity eap-sim eap-sim-pcsc eap-aka eap-aka-3gpp2 eap-simaka-pseudonym eap-simaka-reauth eap-md5 eap-gtc eap-dynamic eap-radius eap-tls eap-ttls eap-peap eap-tnc xauth-eap xauth-pam xauth-noauth tnc-tnccs tnccs-20 tnccs-11 tnccs-dynamic dhcp whitelist lookip error-notify certexpire led radattr addrblock unity
Listening IP addresses:
  8.8.8.8
  172.27.1.3
Connections:
       host2:  8.8.8.8...4.4.4.4  IKEv2
       host2:   local:  [8.8.8.8] uses pre-shared key authentication
       host2:   remote: [4.4.4.4] uses pre-shared key authentication
       host2:   child:  8.8.8.8/32 === 192.168.1.0/24 192.168.2.0/24 
TUNNEL
Security Associations (1 up, 0 connecting):
       host2[1]: ESTABLISHED 115 seconds ago, 8.8.8.8[8.8.8.8]...4.4.4.4[4.4.4.4]
   host2[1]: IKEv2 SPIs: 1f4ce050e3e482ac_i* 35d68fd4c114ef25_r, pre-shared key reauthentication in 2 hours
   host2[1]: IKE proposal: AES_CBC_256/HMAC_SHA2_512_256/PRF_HMAC_SHA2_512/MODP_2048_256
   host2{1}:  INSTALLED, TUNNEL, reqid 1, ESP SPIs: ca77e9b9_i a6993362_o
   host2{1}:  AES_CBC_256/HMAC_SHA1_96, 0 bytes_i, 0 bytes_o, rekeying in 40 minutes
   host2{1}:   8.8.8.8/32 === 192.168.2.0/24

The ASA after successful connection:

asa-fw1# show crypto ipsec sa peer 8.8.4.4 | include ident
  local ident (addr/mask/prot/port): (192.168.2.0/255.255.255.0/0/0)
  remote ident (addr/mask/prot/port): (172.27.1.0/255.255.240.0/0/0)

And a different tunnel between 2 ASAs:

      local ident (addr/mask/prot/port): (10.1.2.0/255.255.255.252/0/0)
      remote ident (addr/mask/prot/port) : (192.168.10.2/255.255.255.255/0/0)
      local ident (addr/mask/prot/port): (192.168.1.0/255.255.255.0/0/0)
      remote ident (addr/mask/prot/port): (192.168.10.2/255.255.255.255/0/0)
      local ident (addr/mask/prot/port): (192.168.2.0/255.255.255.0/0/0)
      remote ident (addr/mask/prot/port): (192.168.10.2/255.255.255.255/0/0)
      local ident (addr/mask/prot/port): (192.168.4.0/255.255.255.0/0/0)
      remote ident (addr/mask/prot/port): (192.168.10.2/255.255.255.255/0/0)

I have also tried putting additional right subnets on their own, such as follows:

conn host2
    left=8.8.8.8 #Changed from real for this example
    leftsubnet=172.27.1.0/20
    right=4.4.4.4 # changed
    rightsubnet=192.168.1.0/24
    ike=aes256-sha512-modp2048s256
    esp=aes256-sha512
    keyingtries=0
    ikelifetime=1h
    lifetime=8h
    dpddelay=30
    dpdtimeout=120
    dpdaction=restart
    authby=secret
    auto=add
    keyexchange=ikev2
    type=tunnel

conn host2-2
    also=host2
    rightsubnet=192.168.2.0/24

after connection:

$ipsec statusall
Status of IKE charon daemon (strongSwan 5.5.1, Linux 4.13.0-37-generic, x86_64):
  uptime: 52 seconds, since Mar 23 09:02:22 2018
  malloc: sbrk 2293760, mmap 532480, used 1203936, free 1089824
  worker threads: 11 of 16 idle, 5/0/0/0 working, job queue: 0/0/0/0, 
scheduled: 2
  loaded plugins: charon test-vectors unbound ldap pkcs11 aes rc2 sha2 sha1 md4 md5 mgf1 rdrand random nonce x509 revocation constraints acert pubkey pkcs1 pkcs7 pkcs8 pkcs12 pgp dnskey sshkey dnscert ipseckey pem gcrypt af-alg fips-prf gmp chapoly xcbc cmac hmac ctr ccm ntru bliss curl soup mysql sqlite attr kernel-netlink resolve socket-default farp stroke updown eap-identity eap-sim eap-sim-pcsc eap-aka eap-aka-3gpp2 eap-simaka-pseudonym eap-simaka-reauth eap-md5 eap-gtc eap-dynamic eap-radius eap-tls eap-ttls eap-peap eap-tnc xauth-eap xauth-pam xauth-noauth tnc-tnccs tnccs-20 tnccs-11 tnccs-dynamic dhcp whitelist lookip error-notify certexpire led radattr addrblock unity
Listening IP addresses:
  8.8.8.8
  172.27.1.3
Connections:
       host2:  8.8.8.8...4.4.4.4  IKEv2
       host2:   local:  [8.8.8.8] uses pre-shared key authentication
       host2:   remote: [4.4.4.4] uses pre-shared key authentication
       host2:   child:  8.8.8.8/32 === 192.168.1.0/24 TUNNEL
      host2-2:   child:  8.8.8.8/32 === 192.168.2.0/24 TUNNEL
Security Associations (1 up, 0 connecting):
       host2[1]: ESTABLISHED 50 seconds ago, 
8.8.8.8[8.8.8.8]...4.4.4.4[4.4.4.4]
   host2[1]: IKEv2 SPIs: 98cf15596219b433_i* 8177dc2c8f0605d8_r, pre-shared key reauthentication in 2 hours
   host2[1]: IKE proposal: AES_CBC_256/HMAC_SHA2_512_256/PRF_HMAC_SHA2_512/MODP_2048_256
  host2-2{1}:  INSTALLED, TUNNEL, reqid 1, ESP SPIs: ccc8bf25_i 1cec9278_o
  host2-2{1}:  AES_CBC_256/HMAC_SHA1_96, 336 bytes_i (4 pkts, 40s ago), 336 bytes_o (4 pkts, 40s ago), rekeying in 41 minutes
  host2-2{1}:   8.8.8.8/32 === 192.168.2.0/24

and the ip xfrm policy:

src 192.168.2.0/24 dst 8.8.8.8/32
    dir fwd priority 185664 
    tmpl src 4.4.4.4 dst 8.8.8.8
        proto esp reqid 1 mode tunnel
src 192.168.2.0/24 dst 8.8.8.8/32
    dir in priority 185664
    tmpl src 4.4.4.4 dst 8.8.8.8
        proto esp reqid 1 mode tunnel
 src 8.8.8.8/32 dst 192.168.2.0/24
    dir out priority 185664
    tmpl src 8.8.8.8 dst 4.4.4.4
        proto esp reqid 1 mode tunnel
src 0.0.0.0/0 dst 0.0.0.0/0
    socket in priority 0
src 0.0.0.0/0 dst 0.0.0.0/0
    socket out priority 0
src 0.0.0.0/0 dst 0.0.0.0/0
    socket in priority 0
src 0.0.0.0/0 dst 0.0.0.0/0
    socket out priority 0 
src ::/0 dst ::/0
    socket in priority 0
src ::/0 dst ::/0
    socket out priority 0
src ::/0 dst ::/0
    socket in priority 0
 src ::/0 dst ::/0
    socket out priority 0

When using the above method, I can access 192.168.2.0 but no longer 192.168.1.0
Regardless, the xfrm policy is the same, and i can only access 192.168.2.0/24

I've tried generating traffic to the subnets without success. Can anyone help determine why I can only access ONE remote subnet on the right side?

cisco-asa

1 Answers

  1. The answer is simple, Cisco ASAs don't support multiple traffic selectors per CHILD_SA. So you have to negotiate individual CHILD_SAs for each combination of local and remote subnet you want to tunnel. That is, something like:

    conn host2
    ...
    rightsubnet=192.168.1.0/24
    ...

conn host2-2
    also=host2
    rightsubnet=192.168.2.0/24

conn host2-3
    also=host2
    rightsubnet=192.168.3.0/24
    • 1