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RFC - Remote access via Open VPN - Routing issues


hachiman
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Hi there, 

I am currently trying to get my OpenVPN demo up and running, making it possible to remotely connect to the network the turtle is connected to. 

Baseline is the setup as described by Darren: 

Access Internal Networks with Reverse VPN connections - Hak5 1921

I have my OpenVPN server, I have created a user for the turtle, one for the laptop, all good. Both can connect to the OpenVPN and I can even connect back to the turtle and SSH in to it. 

But I am not able to go any further from that into the internal network the connected to the RJ45 port at the turtle. 

 

When I use the OpenVPN to ssh into the turtle, I can ping the resource in question. 

Apparently I make some mistakes with the routing config on the OpenVPN?

Sorry but I cant upload images anymore, so I have to describe what I did. 

The OpenVPN turtle user is configured as VPN Gateway, with the following subnets 172.16.0.0/16 & 192.168.0.0/16. 

This is the turtle output:

root@turtle:~# route
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
default         172.27.224.1    128.0.0.0       UG    0      0        0 tun0
default         172.16.7.254    0.0.0.0         UG    20     0        0 eth1
default         172.16.84.84    0.0.0.0         UG    30     0        0 eth0
128.0.0.0       172.27.224.1    128.0.0.0       UG    0      0        0 tun0
167.99.128.12   172.16.7.254    255.255.255.255 UGH   0      0        0 eth1
172.16.0.0      *               255.255.0.0     U     20     0        0 eth1
172.16.84.0     *               255.255.255.0   U     30     0        0 eth0
172.27.224.0    *               255.255.248.0   U     0      0        0 tun0
root@turtle:~# ifconfig
eth0      Link encap:Ethernet  HWaddr 00:13:37:A6:xx:xx
          inet addr:172.16.84.1  Bcast:172.16.84.255  Mask:255.255.255.0
          inet6 addr: fe80::213:37ff:xxxx:xxxx/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:16 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:0 (0.0 B)  TX bytes:1960 (1.9 KiB)
          Interrupt:4 

eth1      Link encap:Ethernet  HWaddr 00:13:37:A6:xx:xx  
          inet addr:172.16.15.161  Bcast:172.16.255.255  Mask:255.255.0.0
          inet6 addr: fe80::213:37ff:::/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:118553 errors:0 dropped:1583 overruns:0 frame:0
          TX packets:4310 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:12094247 (11.5 MiB)  TX bytes:566197 (552.9 KiB)
          Interrupt:5 

lo        Link encap:Local Loopback  
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:65536  Metric:1
          RX packets:2488 errors:0 dropped:0 overruns:0 frame:0
          TX packets:2488 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:168094 (164.1 KiB)  TX bytes:168094 (164.1 KiB)

tun0      Link encap:UNSPEC  HWaddr 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00  
          inet addr:172.27.224.11  P-t-P:172.27.224.11  Mask:255.255.248.0
          inet6 addr: fe80::e208:91c9:::/64 Scope:Link
          UP POINTOPOINT RUNNING NOARP MULTICAST  MTU:1500  Metric:1
          RX packets:346 errors:0 dropped:0 overruns:0 frame:0
          TX packets:531 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:100 
          RX bytes:26292 (25.6 KiB)  TX bytes:118753 (115.9 KiB)

This is the client output

└──╼ $ifconfig 
eth0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 10.0.2.15  netmask 255.255.255.0  broadcast 10.0.2.255
        inet6 fe80::67ce:549b:::  prefixlen 64  scopeid 0x20<link>
        ether 08:00:27:b3:d8:99  txqueuelen 1000  (Ethernet)
        RX packets 9360  bytes 9749835 (9.2 MiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 6679  bytes 801398 (782.6 KiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

lo: flags=73<UP,LOOPBACK,RUNNING>  mtu 65536
        inet 127.0.0.1  netmask 255.0.0.0
        inet6 ::1  prefixlen 128  scopeid 0x10<host>
        loop  txqueuelen 1000  (Local Loopback)
        RX packets 700  bytes 52508 (51.2 KiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 700  bytes 52508 (51.2 KiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

tun0: flags=4305<UP,POINTOPOINT,RUNNING,NOARP,MULTICAST>  mtu 1500
        inet 172.27.232.11  netmask 255.255.248.0  destination 172.27.232.11
        inet6 fe80::3ade:e4c::  prefixlen 64  scopeid 0x20<link>
        unspec 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00  txqueuelen 500  (UNSPEC)
        RX packets 693  bytes 313538 (306.1 KiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 811  bytes 80166 (78.2 KiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

┌─[hackerman@parrot]─[~/Downloads]
└──╼ $route
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         172.27.232.1    128.0.0.0       UG    0      0        0 tun0
default         10.0.2.2        0.0.0.0         UG    100    0        0 eth0
10.0.2.0        0.0.0.0         255.255.255.0   U     100    0        0 eth0
128.0.0.0       172.27.232.1    128.0.0.0       UG    0      0        0 tun0
167.99.128.12   10.0.2.2        255.255.255.255 UGH   0      0        0 eth0
172.27.232.0    0.0.0.0         255.255.248.0   U     0      0        0 tun0
 
When I establish the VPN connection on the client, I dont see any route adds for the specific network of 172.16.0.0/16, as I configured it in the OpenVPN GUI.
2021-08-30 11:26:00 ROUTE_GATEWAY 10.0.2.2/255.255.255.0 IFACE=eth0 HWADDR=08:00:27:b3:d8:99
2021-08-30 11:26:00 TUN/TAP device tun0 opened
2021-08-30 11:26:00 net_iface_mtu_set: mtu 1500 for tun0
2021-08-30 11:26:00 net_iface_up: set tun0 up
2021-08-30 11:26:00 net_addr_v4_add: 172.27.232.13/21 dev tun0
2021-08-30 11:26:05 ROUTE remote_host is NOT LOCAL
2021-08-30 11:26:05 net_route_v4_add: 1.199.128.12/32 via 10.0.2.2 dev [NULL] table 0 metric -1
2021-08-30 11:26:05 net_route_v4_add: 0.0.0.0/1 via 172.27.232.1 dev [NULL] table 0 metric -1
2021-08-30 11:26:05 net_route_v4_add: 128.0.0.0/1 via 172.27.232.1 dev [NULL] table 0 metric -1
2021-08-30 11:26:05 Initialization Sequence Completed

 

Anyone any idea why? What am I missing in terms of routing?

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