Saturday, August 15, 2015

Policy Based IPSec VPN Configuration Between SRX Firewalls

Juniper SRX support both Route-based and Policy-based VPN, which can be used in different scenarios based on your environments and requirements. 


Difference between them (KB15745)

With policy-based VPN tunnels, a tunnel is treated as an object that together with source, destination, application, and action, comprises a tunnel policy that permits VPN traffic. In a policy-based VPN configuration, a tunnel policy specifically references a VPN tunnel by name.

With route-based VPNs, a policy does not specifically reference a VPN tunnel. Instead, the policy references a destination address. When the security device does a route lookup to find the interface through which it must send traffic to reach that address, it finds a route via a secure tunnel (ST) interface, which is bound to a specific VPN tunnel.

Thus, with a policy-based VPN tunnel, you can consider a tunnel as an element in the construction of a policy. With a route-based VPN tunnel, you can consider a tunnel as a means for delivering traffic, and the policy as a method for either permitting or denying the delivery of that traffic.


Scenarios to use them:  

The following are reasons why you implement route-based VPN:
  • Source or destination NAT (NAT-src or NAT-dst) needs to occur as traffic travels through the VPN.
  • There are overlapping subnets or IP addresses between the two LANs.
  • Hub-and-spoke VPN topology is used in the network.
  • Primary and backup VPN are required.
  • A dynamic routing protocol (for example, OSPF, RIP, or BGP) is running across the VPN.
  • Multiple subnets or networks at the remote site across the VPN need to be accessed.
The following are reasons why you implement policy-based VPN:
  • The remote VPN device is a non-Juniper device.
  • Only one subnet or one network at the remote site across the VPN needs to be accessed.

Route-Based VPN Configuration Procedures

My previous posts (Using PKI Build Route-Based IPSec VPN between Juniper SRX) have shown the configuration Route-Based VPN between two SRX firewalls. This Post will present the procedures how to use policy-based VPN.

Topology:


Two Juniper SRX Firewalls.
FW1:
External Interface Reth0.0 = 192.168.9.18
Internal Interface Reth1.0 = 10.94.138.18

FW2:
External Interface Reth0.0 = 10.99.132.18
Internal Interface Reth1.0 = 10.99.136.18

VPN will be built between FW1 and FW2. Firewall Policy will use VPN tunnel for traffic between 10.94.138.0/24 and 10.99.136.0/24

We will generate traffic between two machines 10.94.138.21 and 10.99.136.16 to test this vpn configuration on FW1 and FW2.

Step 1: routing between 10.94.132.18 and 192.168.9.18

@FW1:
[email protected]> show configuration routing-options
static {
    route 0.0.0.0/0 next-hop 10.94.12.1;   /* this is fxp0.0 mgmt interface*/
    route 10.99.132.0/24 next-hop 192.168.9.1;   /* this route added to reach vpn peer gateway*/
}

@FW2
[email protected]> show configuration routing-options 
static {
    route 0.0.0.0/0 next-hop 10.99.12.1;
    route 192.168.9.0/24 next-hop 10.99.132.1;
}

Step 2: Phase 1 IKE configuration

@FW1:

ike {

    proposal ike-p1-proposal {
        authentication-method pre-shared-keys;
        dh-group group2;
        authentication-algorithm sha1;
        encryption-algorithm aes-128-cbc;
    }
    policy ike-p1-policy {
        mode main;
        proposals ike-p1-proposal;
        pre-shared-key ascii-text "$9$O/-1REyXxdsgJSds2gJZn/9p1RylK"; ## SECRET-DATA
    }
    gateway gw-montreal-pin {        
        ike-policy ike-p1-policy;
        address 10.99.132.18;
        external-interface reth0.0;
    }
}
@FW2

ike {

    proposal ike-p1-proposal {
        authentication-method pre-shared-keys;
        dh-group group2;
        authentication-algorithm sha1;
        encryption-algorithm aes-128-cbc;
    }
    policy ike-p1-policy {
        mode main;
        proposals ike-p1-proposal;
        pre-shared-key ascii-text "$9$MkgXxdaJDmT7-Dk.mTQEcSe8Xdbs"; ## SECRET-DATA
    }
    gateway gw-k-pin {          
        ike-policy ike-p1-policy;
        address 192.168.9.18;
        external-interface reth0.0;
    }
}

Step 3: Phase 2 IPSec configuration

@FW1:

ipsec {

    proposal ipsec-p1-proposal {
        protocol esp;
        authentication-algorithm hmac-sha-256-128;
        encryption-algorithm aes-128-cbc;
        lifetime-seconds 3600;
    }
    policy ipsec-p2-policy {
        perfect-forward-secrecy {
            keys group2;
        }
        proposals ipsec-p1-proposal;
    }
    vpn ike-vpn-m {
        ike {
            gateway gw-m-pin;
            ipsec-policy ipsec-p2-policy;
        }
    }
}

@FW2

ipsec {

    proposal ipsec-p1-proposal {
        protocol esp;
        authentication-algorithm hmac-sha-256-128;
        encryption-algorithm aes-128-cbc;
    }
    policy ipsec-p2-policy {
        perfect-forward-secrecy {
            keys group2;
        }
        proposals ipsec-p1-proposal;
    }
    vpn ike-vpn-k {
        ike {
            gateway gw-k-pin;
            ipsec-policy ipsec-p2-policy;
        }
    }
}

Step 4: Policy Configuration

@FW1:
    from-zone T to-zone D {
        policy p-vpn-1 {
            match {
                source-address n_10.94.138.0-24;
                destination-address n_10.99.136.0-24;
                application any;
            }
            then {
                permit {
                    tunnel {
                        ipsec-vpn ike-vpn-m;
                        pair-policy p-vpn-2;
                    }
                    application-services {
                        idp;
                    }
                }
                log {
                    session-close;
                }
            }
        }
        policy 7 {
            match {
                source-address any;
                destination-address any;
                application any;
            }
            then {
                deny;
            }
        }
    }
    from-zone D to-zone T {
        policy p-vpn-2 {
            match {
                source-address n_10.99.136.0-24;
                destination-address n_10.94.138.0-24;
                application any;
            }
            then {
                permit {
                    tunnel {
                        ipsec-vpn ike-vpn-m;
                        pair-policy p-vpn-1;
                    }
                    application-services {
                        idp;
                    }
                }
                log {
                    session-close;
                }
            }
        }
        policy 9 {
            match {
                source-address any;
                destination-address any;
                application any;
            }
            then {
                deny;
            }
        }
    }
}

@FW2

from-zone D to-zone P {
    policy p-vpn-1 {
        match {
            source-address n_10.94.138.0-24;
            destination-address n_10.99.136.0-24;
            application any;
        }
        then {
            permit {
                tunnel {
                    ipsec-vpn ike-vpn-markham;
                    pair-policy p-vpn-2;
                }
            }
        }
    }
    policy 3 {
        match {
            source-address any;
            destination-address any;
            application any;
        }
        then {
            deny;
        }
    }
}
from-zone P to-zone D {
    policy p-vpn-2 {
        match {
            source-address n_10.99.136.0-24;
            destination-address n_10.94.138.0-24;
            application any;
        }
        then {
            permit {
                tunnel {
                    ipsec-vpn ike-vpn-markham;
                    pair-policy p-vpn-1;
                }
            }
        }
    }
    policy 4 {
        match {
            source-address any;
            destination-address any;
            application any;
        }
        then {
            deny;
        }
    }
}

Verification:

Ping between 10.99.136.16 and 10.94.138.21 is not working. That means unfortunately with those above configuration, the vpn tunnel is still not able up.

Troubleshooting:

[email protected]# show | compare    
[edit security]
+   flow {
+       traceoptions {
+           file J1;
+           flag basic-datapath;
+           packet-filter Match-Traffic {
+               source-prefix 10.99.136.9/32;
+               destination-prefix 10.94.138.21/32;
+           }
+       }
+   }

[email protected]# run show log J1
Aug 14 21:37:46 21:37:46.231681:CID-1:RT:filter 1 name Match-Traffic2 is set
Aug 14 21:37:46 21:37:46.231068:CID-1:CTRL:flow1: Rate limit changed to 0
Aug 14 21:37:46 21:37:46.231561:CID-1:CTRL:flow11: Destination ID set to 2
Aug 14 21:37:55 21:37:55.341589:CID-2:RT:<10.99.136.9/1->10.94.138.21/50019;1> matched filter Match-Traffic:
Aug 14 21:37:55 21:37:55.341589:CID-2:RT:packet [72] ipid = 50020, @0x436a041cAug 14 21:37:55 21:37:55.341589:CID-2:RT:---- flow_process_pkt: (thd 3): flow_ctxt type 15, common flag 0x0, mbuf 0x436a0200, rtbl_idx = 0Aug 14 21:37:55 21:37:55.341589:CID-2:RT: flow process pak fast ifl 68 in_ifp reth1.0
Aug 14 21:37:55 21:37:55.341589:CID-2:RT:  reth1.0:10.99.136.9->10.94.138.21, icmp, (8/0)
Aug 14 21:37:55 21:37:55.341589:CID-2:RT: find flow: table 0x59b36da8, hash 34415(0xffff), sa 10.99.136.9, da 10.94.138.21, sp 1, dp 50019, proto 1, tok 7
Aug 14 21:37:55 21:37:55.341589:CID-2:RT:  no session found, start first path. in_tunnel - 0x0, from_cp_flag - 0
Aug 14 21:37:55 21:37:55.341589:CID-2:RT:  flow_first_create_session
Aug 14 21:37:55 21:37:55.341589:CID-2:RT:  flow_first_in_dst_nat: in <reth1.0>, out <N/A> dst_adr 10.94.138.21, sp 1, dp 50019                      
Aug 14 21:37:55 21:37:55.341589:CID-2:RT:  chose interface reth1.0 as incoming nat if.
Aug 14 21:37:55 21:37:55.341589:CID-2:RT:flow_first_rule_dst_xlate: DST no-xlate: 0.0.0.0(0) to 10.94.138.21(50019)
Aug 14 21:37:55 21:37:55.341589:CID-2:RT:flow_first_routing: vr_id 0, call flow_route_lookup(): src_ip 10.99.136.9, x_dst_ip 10.94.138.21, in ifp reth1.0, out ifp N/A sp 1, dp 50019, ip_proto 1, tos 0
Aug 14 21:37:55 21:37:55.341890:CID-2:RT:Doing DESTINATION addr route-lookup
                                     
Aug 14 21:37:55 21:37:55.341916:CID-2:RT:  routed (x_dst_ip 10.94.138.21) from P (reth1.0 in 1) to fxp0.0, Next-hop: 10.99.12.1
                                     
Aug 14 21:37:55 21:37:55.341916:CID-2:RT:  packet dropped, out_ifp is null or in null-zone               
Aug 14 21:37:55 21:37:55.341961:CID-2:RT:Out-ifp fxp0.0 is null or in null zone
Aug 14 21:37:55 21:37:55.341961:CID-2:RT:  flow find session returns error.
Aug 14 21:37:55 21:37:55.341961:CID-2:RT: ----- flow_process_pkt rc 0x7 (fp rc -1)
Aug 14 21:37:55 21:37:55.814250:CID-2:RT:jsf sess close notify                          
Aug 14 21:37:55 21:37:55.814302:CID-2:RT:flow_ipv4_del_flow: sess 69453, in hash 32
Aug 14 21:37:55 21:37:55.814315:CID-2:RT:ha_ifp: fxp0.0
Aug 14 21:38:04 21:38:04.521249:CID-2:RT:<10.99.136.9/0->10.94.138.21/1024;1> matched filter Match-Traffic:
Aug 14 21:38:04 21:38:04.521249:CID-2:RT:packet [84] ipid = 9853, @0x4368eb9c

It obviously the packets went out through fxp0.0. Basic my previous post How Firewalls (Security Gateways) Handle the Packets? (Traffic Flow) , for Juniper SRX firewall Routing Lookup happens before policy.
In this case, before vpn policy is able to get packets into vpn tunnel , the packets went out firewall fxp0.0 interface by default route.

[email protected]# run show route
inet.0: 9 destinations, 10 routes (9 active, 0 holddown, 0 hidden)
+ = Active Route, - = Last Active, * = Both

0.0.0.0/0          *[Static/5] 1d 06:08:38
                    > to 10.99.12.1 via fxp0.0
10.99.12.0/24      *[Direct/0] 1d 06:08:38
                    > via fxp0.0
                    [Direct/0] 1d 06:08:38
                    > via fxp0.0
10.99.12.10/32     *[Local/0] 1d 06:08:38
                      Local via fxp0.0
10.99.12.15/32     *[Local/0] 1d 06:08:38
                      Local via fxp0.0
10.99.132.0/24     *[Direct/0] 1d 06:08:38
                    > via reth0.0
10.99.132.18/32    *[Local/0] 1d 06:08:38
                      Local via reth0.0
10.99.136.0/24     *[Direct/0] 1d 06:08:38
                    > via reth1.0
10.99.136.18/32    *[Local/0] 1d 06:08:38
                      Local via reth1.0
192.168.9.0/24     *[Static/5] 06:31:41
                    > to 10.99.132.1 via reth0.0

Solutions:

At this moment, firewall only has one specific route for peer gateway. Another specific static route will be added to route interesting  traffic through external interface.

[email protected]# show
static {
    route 0.0.0.0/0 next-hop 10.99.12.1;
    route 192.168.9.0/24 next-hop 10.99.132.1;
}

[email protected]# set static route 10.94.138.0/24 next-hop 10.99.132.1

After added this route, tunnel is up right away when testing with interesting traffic.

{primary:node1}
[email protected]> show security ike security-associations
node1:
--------------------------------------------------------------------------
Index   State  Initiator cookie  Responder cookie  Mode           Remote Address
11102161 UP    5184a7627510f777  bba6d0242cb15a30  Main           192.168.9.18  

[email protected]> show security ipsec security-associations
node1:
--------------------------------------------------------------------------
  Total active tunnels: 1
  ID    Algorithm       SPI      Life:sec/kb  Mon lsys Port  Gateway
  <2    ESP:aes-128/sha256 1cca52a5 3567/ unlim -  root 500   192.168.9.18  
  >2    ESP:aes-128/sha256 30b03088 3567/ unlim -  root 500   192.168.9.18  

Reference:

1. Using PKI Build Route-Based IPSec VPN between Juniper SRX
2. Configuration Examples: Policy-based VPN


2 comments:

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