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I have LibreSwan Setup on AWS EC2 CentOS7 instance, IPsec tunnel is established with the peer (Cisco ASA). The Tunnel is up, but I no traffic. I cannot ping the nodes at the side of the peer. Here is my setup. on AWS EC2 instance

EC2 instance - running CentOS7 
Public IP: A.B.C.D
Private IP: E.F.G.H

[toor@ip-E-F-G-H ~]# lsb_release -a
LSB Version:    :core-4.1-amd64:core-4.1-noarch
Distributor ID: CentOS
Description:    CentOS Linux release 7.5.1804 (Core)
Release:    7.5.1804
Codename:   Core

[toor@ip-E-F-G-H ~]# ipsec version
Linux Libreswan 3.23 (netkey) on 3.10.0-862.3.2.el7.x86_64

[toor@ip-E-F-G-H ~]# ipsec version
Verifying installed system and configuration files

Version check and ipsec on-path                     [OK]
Libreswan 3.23 (netkey) on 3.10.0-862.3.2.el7.x86_64
Checking for IPsec support in kernel                [OK]
 NETKEY: Testing XFRM related proc values
         ICMP default/send_redirects                [OK]
         ICMP default/accept_redirects              [OK]
         XFRM larval drop                           [OK]
Pluto ipsec.conf syntax                             [OK]
Two or more interfaces found, checking IP forwarding    [OK]
Checking rp_filter                                  [OK]
Checking that pluto is running                      [OK]
 Pluto listening for IKE on udp 500                 [OK]
 Pluto listening for IKE/NAT-T on udp 4500          [OK]
 Pluto ipsec.secret syntax                          [OK]
Checking 'ip' command                               [OK]
Checking 'iptables' command                         [OK]
Checking 'prelink' command does not interfere with FIPS [OK]
Checking for obsolete ipsec.conf options            [OK]

Here is my ipsec.conf

config setup
        logfile=/var/log/pluto.log
        virtual_private=%v4:M.N.O.P/32,%v4:Q.R.S.T/32 #are encryption Domain of my peer
        protostack=netkey

conn MyConnection
       authby=secret
       auto=start
       type=tunnel
       ## phase1 ##
      ike=aes256-sha1;modp2048
      keyexchange=ike
      ## phase2 ##
      phase2=esp
      phase2alg=aes256-sha1;modp2048
      compress=no
      pfs=yes
      left=%defaultroute
      leftid=A.B.C.D #MyPublic Ip on AWS EC2
      leftsourceip=E.F.G.H . #My private ip of my ec2 centos7 instance
      leftsubnet=E.F.G.H/32
      leftnexthop=%defaultroute
      ## MyPeer ##
      right=I.J.K.L #Public ip of the peer - cisco asa device
      rightsubnets={M.N.O.P/32,Q.R.S.T/32}
      ikelifetime=28800s
      salifetime=3600s
      aggrmode=no

my ipsec.secrets
A.B.C.D I.J.K.L: PSK "*&^%$3434"

here is ipsec status

[toor@ip-E-F-G-H ~]# ipsec auto --status

000 "MyConnection/0x2": IKE algorithms: AES_CBC_256-HMAC_SHA1-MODP1536
000 "MyConnection/0x2": IKE algorithm newest: AES_CBC_256-HMAC_SHA1-MODP1536
000 "MyConnection/0x2": ESP algorithms: AES_CBC_256-HMAC_SHA1_96-MODP1536
000 "MyConnection/0x2": ESP algorithm newest: AES_CBC_256-HMAC_SHA1_96; pfsgroup=MODP1536
000
000 Total IPsec connections: loaded 2, active 2
000
000 State Information: DDoS cookies not required, Accepting new IKE connections
000 IKE SAs: total(1), half-open(0), open(0), authenticated(1), anonymous(0)
000 IPsec SAs: total(2), authenticated(2), anonymous(0)
000
000 #2: "MyConnection/0x1":4500 STATE_QUICK_I2 (sent QI2, IPsec SA established); EVENT_SA_REPLACE in 734s; newest IPSEC; eroute owner; isakmp#1; idle; import:admin initiate
000 #2: "MyConnection/0x1" esp.bd6f5d5@I.J.K.L esp.e6e75a6@A.B.C.D tun.0@I.J.K.L tun.0@A.B.C.D ref=0 refhim=0 Traffic: ESPin=0B ESPout=4KB! ESPmax=4194303B
000 #1: "MyConnection/0x2":4500 STATE_MAIN_I4 (ISAKMP SA established); EVENT_SA_REPLACE in 25692s; newest ISAKMP; lastdpd=0s(seq in:0 out:0); idle; import:admin initiate
000 #3: "MyConnection/0x2":4500 STATE_QUICK_I2 (sent QI2, IPsec SA established); EVENT_SA_REPLACE in 524s; newest IPSEC; eroute owner; isakmp#1; idle; import:admin initiate
000 #3: "MyConnection/0x2" esp.be78561f@I.J.K.L esp.21e1d536@A.B.C.D tun.0@I.J.K.L tun.0@A.B.C.D ref=0 refhim=0 Traffic: ESPin=0B ESPout=1KB! ESPmax=4194303B
000
000 Bare Shunt list:
000

here is my route -n cmd and cannot ping those nodes in the encryption domain of my peer

[toor@ip-E-F-G-H ~]# route -n
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
0.0.0.0 E.F.0.1 0.0.0.0 UG 0 0 0 eth0
M.N.O.P E.F.0.1 255.255.255.255 UGH 0 0 0 eth0
Q.R.S.T E.F.0.1 255.255.255.255 UGH 0 0 0 eth0
E.F.0.0 0.0.0.0 255.255.240.0 U 0 0 0 eth0

[root@ip-E-F-G-H ~]#ping M.N.O.P
no reply

[root@ip-E-F-G-H ~]#ping Q.R.S.T
no reply

here is my iptables -L, no POSTROUTING

[root@ip-E-F-G-H ~]#iptables -L
Chain INPUT (policy ACCEPT)
target     prot opt source               destination
ACCEPT     udp  --  anywhere             anywhere             udp dpt:isakmp
ACCEPT     tcp  --  anywhere             anywhere             tcp dpt:ipsec-nat-t
ACCEPT     udp  --  anywhere             anywhere             udp dpt:ipsec-nat-t
ACCEPT     esp  --  anywhere             anywhere
ACCEPT     ah   --  anywhere             anywhere

Chain FORWARD (policy ACCEPT)
target     prot opt source               destination
ACCEPT     all  --  anywhere             anywhere
ACCEPT     all  --  anywhere             anywhere

Chain OUTPUT (policy ACCEPT)
target     prot opt source               destination

[root@ip-E-F-G-H ~]#iptables -t nat -L -v -n
Chain PREROUTING (policy ACCEPT 19 packets, 1024 bytes)
 pkts bytes target     prot opt in     out     source               destination

Chain INPUT (policy ACCEPT 19 packets, 1024 bytes)
 pkts bytes target     prot opt in     out     source               destination

Chain OUTPUT (policy ACCEPT 305 packets, 127K bytes)
 pkts bytes target     prot opt in     out     source               destination

Chain POSTROUTING (policy ACCEPT 305 packets, 127K bytes)
 pkts bytes target     prot opt in     out     source               destination

On AWS EC2 instance, I have disbled Source/dest check. On AWS EC2 instance security group, added these on inbound

Type               Protocol    Port Range   Source           Description
All traffic        All         All          M.N.O.P/32
All traffic        All         All          Q.R.S.T/32
SSH                TCP         22           0.0.0.0/0
Custom Protocol    AH (51)     All          0.0.0.0/0
Custom Protocol    ESP (50)    All          0.0.0.0/0
Custom UDP Rule    UDP         4500         0.0.0.0/0
Custom UDP Rule    UDP         500          0.0.0.0/0
All ICMP - IPv4    All         N/A          0.0.0.0/0

On AWS EC2 instance security group, added these on outbound

Type               Protocol    Port Range   Source           Description
All traffic        All         All          0.0.0.0/0
All traffic        All         All          M.N.O.P/32
All traffic        All         All          Q.R.S.T/32

Under VPC section, region for my ec2 instance.. Added this on the routing table

Destination      Target              Status     Propagated
E.F.0.0/16       local               Active     No
0.0.0.0/0        igw-747d3673hsd     Active     No
M.N.O.P/32       eni-0fec2be5-on-ec2 Active     No
Q.R.S.T/32       eni-0fec2be5-on-ec2 Active     No

Also Add some Network ACLs - inbound

Rule #   Type        Protocol   Port Range   Source     Allow / Deny
100      ALL Traffic ALL        ALL          0.0.0.0/0  ALLOW
200      ALL Traffic ALL        ALL          M.N.O.P/32 ALLOW
300      ALL Traffic ALL        ALL          Q.R.S.T/32 ALLOW
*        ALL Traffic ALL        ALL          0.0.0.0/0  DENY

Also Add some Network ACLs - Outbound

Rule #   Type        Protocol   Port Range   Source     Allow / Deny
100      ALL Traffic ALL        ALL          0.0.0.0/0  ALLOW
200      ALL Traffic ALL        ALL          M.N.O.P/32 ALLOW
300      ALL Traffic ALL        ALL          Q.R.S.T/32 ALLOW
*        ALL Traffic ALL        ALL          0.0.0.0/0  DENY

That's ALL - The tunnel is up, aws ec2 centos7 with Libreswan to Cisco ASA. But No Traffic, i cannot ping or trace the nodes behind the cisco asa firewall. Any pointers with on the aws side is highly appreciated. thanks


I have got the cisco Admin to show me his side

here is the sh crypto ipsec sa peer A.B.C.D output

sh crypto ipsec sa peer A.B.C.D
peer address: A.B.C.D
    Crypto map tag: TELCOCryptoMap, seq num: 690, local addr: I.J.K.L

      access-list CRYPTO-NETXCELL-VPN extended permit ip host M.N.O.P host E.F.G.H 
      local ident (addr/mask/prot/port): (M.N.O.P/255.255.255.255/0/0)
      remote ident (addr/mask/prot/port): (E.F.G.H/255.255.255.255/0/0)
      current_peer: A.B.C.D


      #pkts encaps: 0, #pkts encrypt: 0, #pkts digest: 0
      #pkts decaps: 0, #pkts decrypt: 0, #pkts verify: 0
      #pkts compressed: 0, #pkts decompressed: 0
      #pkts not compressed: 0, #pkts comp failed: 0, #pkts decomp failed: 0
      #pre-frag successes: 0, #pre-frag failures: 0, #fragments created: 0
      #PMTUs sent: 0, #PMTUs rcvd: 0, #decapsulated frgs needing reassembly: 0
      #TFC rcvd: 0, #TFC sent: 0
      #Valid ICMP Errors rcvd: 0, #Invalid ICMP Errors rcvd: 0
      #send errors: 0, #recv errors: 0

      local crypto endpt.: I.J.K.L/4500, remote crypto endpt.: A.B.C.D/4500
      path mtu 1500, ipsec overhead 82(52), media mtu 1500
      PMTU time remaining (sec): 0, DF policy: copy-df
      ICMP error validation: disabled, TFC packets: disabled
      current outbound spi: 3F59926A
      current inbound spi : D8CD619E

    inbound esp sas:
      spi: 0xD8CD619E (3637338526)
         SA State: active
         transform: esp-aes-256 esp-sha-hmac no compression 
         in use settings ={L2L, Tunnel,  NAT-T-Encaps, PFS Group 5, IKEv1, }
         slot: 0, conn_id: 266432512, crypto-map: TELCOCryptoMap
         sa timing: remaining key lifetime (kB/sec): (4374000/3438)
         IV size: 16 bytes
         replay detection support: Y
         Anti replay bitmap: 
          0x00000000 0x00000001
    outbound esp sas:
      spi: 0x3F59926A (1062834794)
         SA State: active
         transform: esp-aes-256 esp-sha-hmac no compression 
         in use settings ={L2L, Tunnel,  NAT-T-Encaps, PFS Group 5, IKEv1, }
         slot: 0, conn_id: 266432512, crypto-map: TELCOCryptoMap
         sa timing: remaining key lifetime (kB/sec): (4374000/3438)
         IV size: 16 bytes
         replay detection support: Y
         Anti replay bitmap: 
          0x00000000 0x00000001

    Crypto map tag: TELCOCryptoMap, seq num: 690, local addr: I.J.K.L

      access-list CRYPTO-NETXCELL-VPN extended permit ip host Q.R.S.T host E.F.G.H 
      local ident (addr/mask/prot/port): (Q.R.S.T/255.255.255.255/0/0)
      remote ident (addr/mask/prot/port): (E.F.G.H/255.255.255.255/0/0)
      current_peer: A.B.C.D


      #pkts encaps: 0, #pkts encrypt: 0, #pkts digest: 0
      #pkts decaps: 0, #pkts decrypt: 0, #pkts verify: 0
      #pkts compressed: 0, #pkts decompressed: 0
      #pkts not compressed: 0, #pkts comp failed: 0, #pkts decomp failed: 0
      #pre-frag successes: 0, #pre-frag failures: 0, #fragments created: 0
      #PMTUs sent: 0, #PMTUs rcvd: 0, #decapsulated frgs needing reassembly: 0
      #TFC rcvd: 0, #TFC sent: 0
      #Valid ICMP Errors rcvd: 0, #Invalid ICMP Errors rcvd: 0
      #send errors: 0, #recv errors: 0

      local crypto endpt.: I.J.K.L/4500, remote crypto endpt.: A.B.C.D/4500
      path mtu 1500, ipsec overhead 82(52), media mtu 1500
      PMTU time remaining (sec): 0, DF policy: copy-df
      ICMP error validation: disabled, TFC packets: disabled
      current outbound spi: 01DCEC29
      current inbound spi : D9735EB5

    inbound esp sas:
      spi: 0xD9735EB5 (3648216757)
         SA State: active
         transform: esp-aes-256 esp-sha-hmac no compression 
         in use settings ={L2L, Tunnel,  NAT-T-Encaps, PFS Group 5, IKEv1, }
         slot: 0, conn_id: 266432512, crypto-map: TELCOCryptoMap
         sa timing: remaining key lifetime (kB/sec): (4374000/3438)
         IV size: 16 bytes
         replay detection support: Y
         Anti replay bitmap: 
          0x00000000 0x00000001
    outbound esp sas:
      spi: 0x01DCEC29 (31255593)
         SA State: active
         transform: esp-aes-256 esp-sha-hmac no compression 
         in use settings ={L2L, Tunnel,  NAT-T-Encaps, PFS Group 5, IKEv1, }
         slot: 0, conn_id: 266432512, crypto-map: TELCOCryptoMap
         sa timing: remaining key lifetime (kB/sec): (4374000/3438)
         IV size: 16 bytes
         replay detection support: Y
         Anti replay bitmap: 
          0x00000000 0x00000001

With this, the cisco device doesnt seem to have any incoming esp packets. Any pointers, as i believe it might be somewhere at the aws level.. thanks

here is the tcpdump

[toor@ip-E-F-G-H ~]# tcpdump esp
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth0, link-type EN10MB (Ethernet), capture size 262144 bytes
^C
0 packets captured
0 packets received by filter
0 packets dropped by kernel

[toor@ip-E-F-G-H ~]# tcpdump port 4500
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth0, link-type EN10MB (Ethernet), capture size 262144 bytes
13:39:28.382551 IP ip-E-F-G-H.us-east-2.compute.internal.ipsec-nat-t > I.J.K.L.ipsec-nat-t: isakmp-nat-keep-alive
13:39:28.382575 IP ip-E-F-G-H.us-east-2.compute.internal.ipsec-nat-t > I.J.K.L.ipsec-nat-t: isakmp-nat-keep-alive
13:39:28.382580 IP ip-E-F-G-H.us-east-2.compute.internal.ipsec-nat-t > I.J.K.L.ipsec-nat-t: isakmp-nat-keep-alive
13:39:29.222092 IP I.J.K.L.ipsec-nat-t > ip-E-F-G-H.us-east-2.compute.internal.ipsec-nat-t: NONESP-encap: isakmp: phase 2/others ? inf[E]
13:39:29.222277 IP ip-E-F-G-H.us-east-2.compute.internal.ipsec-nat-t > I.J.K.L.ipsec-nat-t: NONESP-encap: isakmp: phase 2/others ? inf[E]
^C
5 packets captured
5 packets received by filter
0 packets dropped by kernel

[toor@ip-E-F-G-H ~]# tcpdump port 500
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth0, link-type EN10MB (Ethernet), capture size 262144 bytes
^C
0 packets captured
0 packets received by filter
0 packets dropped by kernel

here ip xfrm state

[toor@ip-E-F-G-H ~]# ip xfrm state
src I.J.K.L dst E.F.G.H
    proto esp spi 0xe603c44c reqid 16389 mode tunnel
    replay-window 32 flag af-unspec
    auth-trunc hmac(sha1) 0x53c09c699e580292be07d7159ec6b7bee6767310 96
    enc cbc(aes) 0x1e6fdc95ab9e02d1cbb690f89cca6528ff73e65696528b9615a5b09cd310cd2a
    encap type espinudp sport 4500 dport 4500 addr 0.0.0.0
    anti-replay context: seq 0x0, oseq 0x0, bitmap 0x00000000
src E.F.G.H dst I.J.K.L
    proto esp spi 0x386e8731 reqid 16389 mode tunnel
    replay-window 32 flag af-unspec
    auth-trunc hmac(sha1) 0xec8ed07c653732ffba1d9b63929ac6211005dbee 96
    enc cbc(aes) 0xe046bd204feb33e44b24bf1c1476a7425c8ef3318ab705feb2761ae471823d5a
    encap type espinudp sport 4500 dport 4500 addr 0.0.0.0
    anti-replay context: seq 0x0, oseq 0x3, bitmap 0x00000000
src I.J.K.L dst E.F.G.H
    proto esp spi 0x17676d9a reqid 16393 mode tunnel
    replay-window 32 flag af-unspec
    auth-trunc hmac(sha1) 0x79ab780421c9e079c122006499f9d034ba4ef961 96
    enc cbc(aes) 0xde3c9b22338e09c885d9dae4bc93c99fc650a41aa3a7cc8a6ac07affe72f5bd3
    encap type espinudp sport 4500 dport 4500 addr 0.0.0.0
    anti-replay context: seq 0x0, oseq 0x0, bitmap 0x00000000
src E.F.G.H dst I.J.K.L
    proto esp spi 0x3cfbd571 reqid 16393 mode tunnel
    replay-window 32 flag af-unspec
    auth-trunc hmac(sha1) 0x4163513e0f66ac3656dd18569be72b51b60a3b9e 96
    enc cbc(aes) 0xf4c5b790d4d509daef59c7ab50b6620230113c7d21eeaaff48e5a589733636ea
    encap type espinudp sport 4500 dport 4500 addr 0.0.0.0
    anti-replay context: seq 0x0, oseq 0x5, bitmap 0x00000000

here is ip xfrm policy

[toor@ip-E-F-G-H ~]# ip xfrm policy
src E.F.0.0/20 dst M.N.O.P/32
    dir out priority 2464 ptype main
    tmpl src E.F.G.H dst I.J.K.L
        proto esp reqid 16389 mode tunnel
src M.N.O.P/32 dst E.F.0.0/20
    dir fwd priority 2464 ptype main
    tmpl src I.J.K.L dst E.F.G.H
        proto esp reqid 16389 mode tunnel
--- omitted output -- but u get the gist --
  • Why do you think the problem is on the AWS side? – Michael Hampton Oct 30 '18 at 13:53
  • @MichaelHampton because when i try to ping these nodes M.N.O.P and Q.R.S.T i have no reply and when i do a trace, i don't even reach my ec2 gateway E.F.0.1 is there anything i need to add under AWS VPC section in VPN Connections.. im just tinkering with those many aws guis, thus i think its on the aws side.. – sekayasin Oct 31 '18 at 5:24
  • Looks like you’re doing NAT-Traversal which implies your instance is in a private subnet behind a NAT. Any chance you can move it to a public subnet in your VPC with a public IP and no NAT? That may be easier to set up... – MLu Oct 31 '18 at 18:53
  • @MLu the instance has a public ip, from the configs up A.B.C.D is the public ip of my instance and E.F.G.H is its private ip.. from the routing table of the ec2 E.F.0.1 the gateway of my instance is private, and the subnet E.F.0.0/20 is private.. the NAT-T on Libreswan /openswan is enabled by default.. i pointers on how i can move it to a public subnet.. thanks – sekayasin Oct 31 '18 at 20:13
  • confirmed ec2 is in public subnet.. it has an igw - internet gateway.. any pointers this is taking weeks.. – sekayasin Oct 31 '18 at 20:45
0
  • You can check AWS VPC Flow Logs to verify if there is any blocked inbound traffic. But the SG and NACL listings you posted seem to be open enough for this to work.
  • When you try to ping the other end from your side do you see the outbound ESP packets? You can verify either through the Flow Logs or use tcpdump on your EC2 instance.
  • Does the Cisco see your ESP packets coming in?
  • Can the other side initiate connection to your end?

You will probably need to work with the administrator of the Cisco device to track down what really happens.

  • thanks @MLu will work on that and keep you posted for any help.. any suggestion, under the VPC section on the VPN Connection, do i need to add anything.. Just asking. – sekayasin Oct 31 '18 at 5:29
  • check up, did tcpdump, no esp packets.. any idea where i start.. thanks – sekayasin Oct 31 '18 at 14:04

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