How to Configure IPSec Host to Site tunnel with RSA Keys

How to Configure IPSec Host to Site tunnel with RSA Keys

Version 0.1 (02 May 2018) 

Overview

Host to Site configurations are very similar to Host to Host configurations, especially the authentication methods are the same. Added changes to the configurations are the values for rightsourceip and rightsubnets. These values will expose the listed subnets to the IPSec tunnel and will allows clients in these subnets to communicate with the host (west) node and will allow the west node to allow to communicate with clients in the listed subnets.

In case rightsourceip is used the communication between the 2 nodes will not be encrypted only communication between the west node and the subnet would be encrypted. If a value is defined, then all communication between the East and the west host will use the defined IP Address.


Figure 12: Host to Site Configuration Example Details

Host to Site with RSA Key

  1. Prepare both nodes (see: How to Prepare a Nodegrid Node for IPSec )
  2. On both nodes create an RSA Key (see: Prepare RSA keys )
  3. Create connection configuration file in /etc/ipsec/ipsec.d/ directory as root user
  4. Fields
    Values
    Comments
    Connection name
    <String>
     
    leftid
    @West
    Identifier for the west/left site.
    Values can be:
    %left  - uses left as value
    @<STRING> - uses the string

    The leftid values is used to identify the PSK
    left
    <IP or FQDN> of the West/Left host
    Additional to an actual IP address can the following values be used. These are resolved when the service starts.
    %defaultgateway
    %eth0
    leftrsasigkey
    Public RSA Key
     
    rightid
    @East
    Identifier for the East/right site.
    Values can be:
    %right - uses left as value
    @<STRING> - uses the string The rightid values is used to identify the PSK
    right
    <IP or FQDN> of the East/Right host
    Additional to an actual IP address can the following values be used. These are resolved when the service starts.
    %defaultgateway
    %eth0
    rightsourceip
    <INTERNAL IP TO BE USED>
    IP address if the east node which should be used for the tunnel communication. This IP should belong the rightsubnet.
    rightsubnets
    <LIST OF SUBNETS>
    One or multiple subnet can be defined, for each subnet a individual tunnel will be created
    rightrsasigkey
    Public RSA Key
     
    authby
    rsasig
     
    auto
    start
    The setting regulates when the IPSec tunnel will be established. Following values are accepted: add (manual start), start (starts with the service), ondemand (will be established if traffic exists), ignore (connection will be ignored and not used)
    connaddrfamily
    ipv4
    Possiable values are ipv4 or ipv6

    Format:

    conn 
    connaddrfamily=ipv4
    auto=
    authby=secret
    leftid=
    left=FQDN>
    leftrsasigkey=
    rightid=
    right=FQDN>
    rightsourceip=
    rightsubnet={MASK> MASK>}
    rightrsasigkey=
          

    Example /etc/ipsec/ipsec.d/host-to-site-rsa.conf

    conn host-to-site-rsa
    connaddrfamily=ipv4
    auto=start
    authby=rsasig
    leftid=@West
    left=192.168.50.4
    leftrsasigkey=0sAQO1Gr2MY41qhG…………….bbtc7lkT+TxtPBE7sSBWkHr1C5aalkYLwL9kfgK0i7w==
    rightid=@East
    right=192.168.58.4
    rightsourceip=192.168.60.4
    rightsubnets={192.168.60.0/24 192.168.61.0/24}
    rightrsasigkey=0Vaixy810IkQzUU+SmxA6O………..WORl0i3K43tZx9aakmMyvanRg7Bwz4R+ssDe4+MwsGP0= 
             
          
  5. Copy the configuration file only to the other node. The Secret File does not need to be copied in this case
  6. Restart IPSec service on both nodes
  7. root@ng-west:~# ipsec restart
    Redirecting to: /etc/init.d/ipsec stop
    Shutting down pluto IKE daemon
    002 shutting down
    Redirecting to: /etc/init.d/ipsec start
    Starting pluto IKE daemon for IPsec: .
    root@ng-west:~#
             
          
  8. Confirm that the tunnel was established
    1. Short Information
    2. More Detailed Information
    3. root@ng-west:~# ipsec whack --status |grep host-to-site-rsa
      ……………. 
      000 #4: "host-to-site-rsa":500 STATE_QUICK_R2 (IPsec SA established); EVENT_SA_REPLACE in 28035s; isakmp#3; idle; import:not set
      000 #4: "host-to- site -rsa" esp.51e306d2@192.168.58.4 esp.7bdcb6d9@192.168.50.4 tun.0@192.168.58.4 tun.0@192.168.50.4 ref=0 refhim=0 Traffic: ESPin=0B ESPout=0B! ESPmax=4194303B
      000 #3: "host-to- site -rsa":500 STATE_MAIN_R3 (sent MR3, ISAKMP SA established); EVENT_SA_REPLACE in 2835s; lastdpd=-1s(seq in:0 out:0); idle; import:not set
      000 #5: "host-to- site -rsa":500 STATE_QUICK_I2 (sent QI2, IPsec SA established); EVENT_SA_REPLACE in 27555s; newest IPSEC; eroute owner; isakmp#2; idle; import:admin initiate
      000 #5: "host-to- site -rsa" esp.acd469a4@192.168.58.4 esp.6b948bad@192.168.50.4 tun.0@192.168.58.4 tun.0@192.168.50.4 ref=0 refhim=0 Traffic: ESPin=0B ESPout=0B! ESPmax=4194303B
      000 #2: "host-to- site -rsa":500 STATE_MAIN_I4 (ISAKMP SA established); EVENT_SA_REPLACE in 2114s; newest ISAKMP; lastdpd=-1s(seq in:0 out:0); idle; import:admin initiate 
                  
               

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