IPSec with Sophos as remote peer

| Time until a new IKE CHILD SA is negotiated.
Corresponds to the value 1 hour of key lifetime in the General tab of phase 2 in UTM ?}} }}

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Configuring an IPSec VPN connection with a Sophos firewall as the remote peer

New article: 01.2023

notempty

This article refers to a Resellerpreview

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Preliminary note

• This best practice uses the software versions
  • Securepoint UTM: v12.2.3.1
    Version 12.2.5.1 or higher should be used
      
  • Sophos: SFOS v19.0.0 GA-Build317
• Setting options may change, be renamed or moved in future software versions.

This should not restrict the basic functionality

• Supported VPN types:
  • IPSec with IKEv1
  • IPSec with IKEv2

• SSL / OpenVPN is not supported:
  • Sophos uses proprietary configuration files (.apc instead of .ovpn)
  • There are only a few configuration options

The following network situations were tested:

• Sophos (Public, fixed IP) <-> UTM (Public, fixed IP)
• Sophos (Public, fixed IP) <-> UTM (NAT without port forwarding)
• Sophos (Public, fixed IP) <-> UTM (NAT with port forwarding)
• Sophos (NAT without port forwarding) <-> UTM (Public, fixed IP)
• Sophos (NAT with port forwarding) <-> UTM (NAT without port forwarding)

Additional routers

If the Securepoint UTM or Sophos Firewall is also behind another router (e.g. a Fritzbox that provides Internet access), the following ports must be forwarded there:

• No NAT on either side: Port 500/UDP (ISAKMP)
• NAT on one side: Port 500/UDP + 4500/UDP (NAT-T)

Configuration on the Securepoint UTM

The connection setup on the UTM is done as described in the Wiki article IPSec Site-to-Site.
The following parameters must be considered:

Assistant Securepoint UTM IPSec assistant: → VPN →IPSecTab Connections Button Add IPSec connection Step 2
Log view	Recommended setting
IKE protocol:	IKEv2 (For unsolvable problems, use IKEv1)
Phase 1 Tab General
Start behavior: Outgoing / Incoming	Incoming, on the side where the device is most "directly" connected to the Internet. Ranking: Public, fixed IP Public, dynamic IP Private IP behind NAT router (Fritzbox) Sophos startup behavior in IKEv1 mode cannot be adjusted It tries to establish the connection itself, but also accepts connections
DPD	On Active
Encryption:	Recommended values: AES256 (strongest encryption) AES192 or AES128 The length of the encryption key affects the performance of the connection
Authentication:	Recommended values: SHA2_512 SHA2_384 SHA2_256
Diffie-Hellman Group:	ecp521, ecp384, ecp256, modp8192, modp6144, modp4096 We recommend ecp521
Strict	On Active
IKE Lifetime:	Child_SA Lifetime ≦ IKE_SA Lifetime < 8 Hours Reason: On Sophos, the Child_SA Lifetime must be less than or equal to the IKE_SA Lifetime
Rekeying	unlimited
Phase 2
Encryption:	AES256, AES198, AES128
Authentication:	SHA2_512, SHA2_384, SHA2_512
Diffie-Hellman Group:	ecp512, ecp384, ecp256, modp8192, modp6144, modp4096 We recommend ecp521
IKE_SA Lifetime:	Child_SA Lifetime ≦ IKE_SA Lifetime < 8 Hours Reason: On Sophos, the Child_SA Lifetime must be less than or equal to the IKE_SA Lifetime
Reboot after abort:	If necessary: On Active (Only on the outgoing side)
Group subnet combinations:	Option is not supported by Sophos or is not available If this option is enabled on the Securepoint UTM, only for the first subnet combination an SA is created and as a result a connection is established

Configuration on the Sophos Firewall

Creating an IPsec profile Create an IPsec profile: Login to the Sophos administration interface (Port 4444). Menu: Configure / Site-to-Site VPN IPsec tab Submenu (link): IPsec profiles The profile is used to determine the IKE protocol version (IKEv2/IKEv1), the DPD settings, and mainly to define encryption algorithms.	Fig.1	Fig.2
In the IPsec profiles tab, create a profile with the Add	Fig.3

General settings
Name Securepoint IKEv2	Meaningful name under which the IPsec profile is stored Entry required	Fig.4
Description	Can be optionally specified for each IPsec profile
Key exchange IKEv2	IKE protocol version (Sophos startup behavior cannot be adjusted for IKEv1.)
Authentication method Main mode	The Securepoint UTM supports as authentication method (also exchange mode) for security reasons exclusively the main mode / Main-Mode and not the Aggressive Mode.
Key negotiation attempts 0	Maximum number of attempts to establish the connection. The value 0 allows an unlimited number of attempts at negotiation.
Phase 1
Key lifetime 3600	Time in seconds until a new IKE SA is negotiated. Corresponds to the value 1 hour of IKE Lifetime in the IKE tab of Phase 1 in the UTM. The Sophos default value must be adjusted
DH group (key group) ecp521, ecp384, ecp256, modp8192, modp6144, modp4096	Defining the IKE Diffie-Hellman Group for IKEv2 Phase 1
Encryption AES256	Setting the encryption standard for IKEv2 Phase 1
Authentication SHA2_256	Setting the authentication standard for IKEv2 Phase 1
Phase 2
PFS group (DH group) Same as phase 1	Defining the IKE Diffie-Hellman Group for IKEv2 Phase 2 The Sophos default value must be adjusted
Key lifetime 3600	Zeit, bis eine neue IKE CHILD SA ausgehandelt wird. Entspricht dem Wert 1 Stunde der Schlüssel-Lebensdauer im Reiter Allgemein der Phase 2 in der UTM ?
Encryption AES256	Setting the encryption standard for IKEv2 Phase 2
Authentication SHA2_256	Setting the authentication standard for IKEv2 Phase 2
Dead Peer Detection (DPD) Checks at a set interval whether the tunnel still exists. If the tunnel was terminated unexpectedly, it will be re-initiated.
Peer check all 30	Time in seconds until next check
Wait for response up to 120	Time until the IPSec tunnel is treated as unreachable after an incorrect check
If peer unreachable Reinitiate	Disconnect when the Securepoint UTM initiates the connection. Reinitiate when the Sophos Firewall initiates the connection. The Sophos default value may need to be adjusted
Clicking on the button labeled this way the IPSec profile Saves
Creating the IPsec connection
Menu: Configure / Site-to-Site VPN IPsec tab Section IPsec connections Button Add	Fig.5
General settings
Name Securepoint_UTM_Main_Office	Name under which the IPsec connection is stored Entry required	Fig.6
Description	Can optionally be specified for each IPsec connection
IP version IPv4 / IPv6 / Dual	IP version over which the tunnel is to be established (IPv4/Ipv6).
Connection type Site-to-site	Site-to-site connection
Gateway type Reply only	Responses only (≙ Incoming): Sophos Firewall waits for an SPSec connection and does not initiate the tunnel connection Establish connection (≙ Outgoing): The Sophos Firewall initiates the tunnel connection The Sophos default value may need to be adjusted
Enable when saving	Starts the connection according to Gateway type when saving The Sophos default value should be adjusted
Create firewall rule	Automatic creation of required port filter rules
Encryption
Profile Securepoint IKEv2	Select the previously created IPsec profile The Sophos default value must be adjusted
Authentication method Distributed key	Possible options: Distributed key (=Pre Shared Key, PSK). Digital certificate RSA key
Gateway settings Local gateway
Listening interface	Interface via which the tunnel is to be established Entry required	Fig.7
Local ID type Select local ID	Freely selectable (can be a DNS name, an IP address or an email address).
Local ID	Freely selectable This value must be entered on the Securepoint UTM in the IPSec assistant in Step 4 - Remote Gateway as Remote Gateway ID
Local subnet Add new element	Local network on the Sophos firewall to be included in the tunnel. If the network element does not exist in the list, it can be created in this step
Remote gateway
Gateway address *	Address of the remote gateway (≙Securepoint UTM) The value * should be set if the Sophos Firewall does not initiate the connection and the UTM does not have a fixed IP address with which to make the requests.
Remote ID type Select remote ID	Freely selectable (can be a DNS name, an IP address or an email address).
Remote ID	This value must be entered on the Securepoint UTM in the IPSec assistant in Step 3 - Local as Local Gateway ID
Remote subnet Add new element	Remote network on the Securepoint UTM that is to be accessible via the tunnel. If the network element does not exist in the list, it can be created in this step
Extended
User authentication None	Leave default unchanged at None
Disconnect in idle mode	Do not activate
Create connection with the button Save
Create network elements
For this purpose, a new element can be created using the Add option in the Local subnet and Remote subnet dialogs while creating the IPSec connection.		Fig.8 - after clicking in the respective field
Create remote network element
The values for the Remote subnet (i.e. the network of the Securepoint UTM which should be reachable via the tunnel)
Name Enter hostname	Name of the network element	Fig.9
IP version IPv4 IPv6	Type of IP addresses (IPv4/IPv6) in the remote network (here: the network of the Securepoint UTM).
Type Network	The type network must be selected.
IP address	Network address of the remote UTM network
Subnet /24 (255.255.255.0)	Subnet mask of the remote UTM network
Save network element by clicking on the Save

Troubleshooting

IPsec Log

Fig.10

Viewable under the Control Center menu item in the Monitor & Analyze section, link Log view at the top right of the Sophos Admin Panel.

Fig.11

• After selecting this option a popup window opens
• Select the log category Firewall in the dropdown menu here.

Fig.12

• Now it is possible to select the log category VPN in the drop-down menu.

Tcpdump

TCPdump, access via SSH is required. Enable on the Sophos Firewall: Menu Administration / Appliance Access / Access Control List (ZSL) for local services Enable the Admin Services / SSH column for LAN or WAN SSH on WAN should only be enabled temporarily when needed. Apply the setting with the so called button	Fig.13
Connect to the Sophos Firewall via SSH (port 22) using the Sophos admin credentials. In the Main Menu select option 5. Device Management In the Device Managment menu, select 3. Advanced Shell option.	Fig.15	Fig.14
Commands like tcpdump, ping or ip can now be executed	Fig.16