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Android IKEv2 Client Setup

Task:  

Send end-user instructions on how to configure Android IKEv2 VPN clients.  

Solution:

Installation is a two-step process:

Step 1:  Install all three certificates.  The Administrator has sent a separate website link where you can download necessary certificates:  (a) user_device.PFX; (b) vpn_server.CER, and root.CER.  Open each attachment to start the installation.  Include the PFX password.

Step 2:  Configure the Android VPN client:  Android Settings → Connections → More Connection Settings → VPN → Add VPN.


VPN Settings (Figure 1):
N.B., Change the value for “IPSec user certificate” to “user_android”.
Figure 1.  Android IKEv2 VPN Settings.  
Hint:  VPN shortcut apps are available in the Google Play Store.  This provides a quick and easy method to connect.
For example:  https://play.google.com/store/apps/details?id=com.rosaneng.vpnsettings&hl=en


Also note, your device certificate contains a private key for your client certificate.  Anyone that gets a hold of this key can impersonate your account.  Please protect your device with a passcode and encryption.  This script is not intended for rooted devices.  I encourage you to delete this email from your mailbox after you’ve configured your devices. 

That's It!

Install Mobile-Config Script

Task:  

Setup instructions for manual distribution of mobile-config scripts for iPhones and iPads.

Assumptions:

These instructions assume the mobile-config script has already been generated,  These instructions are for situations when mobile device management (MDM) is not available.  It assumes email distribution from a private server.  Use caution whenever distributing certificates and private keys!

Background:

Mobile-device scripts run on any iPhone or iPad –simply open the email attachment to start the process.  It installs certificates and configures the IKEv2 VPN.  This script can configure multiple devices.

Security Considerations

Also note, the script includes the private key for the client certificate.  This provides identity validation, authentication, and authorization.  Anyone that gets a hold of this key can impersonate the account.  It’s critical to use a passcode and enforce encryption.  Do not install these files on jailbroken devices.  Delete the script from your mailbox after all devices are configured.

Brief instructions:

Step 1:  Open mobile-config file to start the profile installation.

· N.B., This script is not signed –that’s OK.
· Click Next.




Step 2:  Enter device passcode.

Step 3:  Consent.

· Brief description for mobile-config.
· Installation requires consent.
· Click Next.




Step 4:  Confirm Install.

· General VPN disclosure.
· Click Install.  Click Done.

Step 5.  Connect to the VPN.

· Open Settings.
· Toggle the VPN button.
· The VPN symbol appears in upper left-hand corner to confirm active VPN sessions.


The VPN is ready for action.  That's It!

Dynamic S2S VPNs


Task:

Create site-to-site (S2S) interfaces for dynamic IKEv2 VPN clients (e.g., iPhones).  Assign different cryptographic algorithms to each S2S interface.

What are dynamic S2S VPNs?

 S2S VPNs usually support static VPN endpoints.  For example, a dedicated (i.e., always-on) VPN that connects a branch office to its HQ office.  However, S2S VPNs can also connect mobile clients for dynamic connections.   This hybrid approach is for special circumstances.

Why use dynamic S2S VPNs?

Most folks should stick with the default RRAS dial-up VPN server.  It provides better management and reporting tools.  However, dynamic S2S VPNs support configuration features that are unavailable with the standard RRAS client VPNs.

For example, dial-up IKEv2 VPNs may authenticate any certificate issued from one of its trusted root certificates.  S2S VPNs can limit authentication to specific client certificates.  The best part, IMHO,  is the ability to apply unique cipher suites per S2S interface.  For example, we can create separate S2S interfaces for each client -including unique cipher suite standards.

How do we implement dynamic S2S VPNs?

PowerShell offers a straight-forward method to implement S2S VPNs.  However, consider using a GUI-Powershell hybrid approach that supports additional client management features.

Dynamic S2S via PowerShell:

The following example creates a new S2S interface with strong security targets:
• Certificate authentication
• IKEv2 Protocol
• Main Mode:   AES128-SHA256-DHGroup14
• Quick Mode:   AES256-SHA256

Add-VpnS2SInterface -name smj@stevenjordan.net -CustomPolicy -CipherTransformConstants AES128 -DHGroup Group14 -EncryptionMethod aes128 -IntegrityCheckMethod SHA256 -Destination 0.0.0.0 -Protocol IKEv2 -AuthenticationMethod MachineCertificates -ResponderAuthenticationMethod MachineCertificates -EncryptionType RequireEncryption

The interface name always matches the authentication certificate's subject name.  Some clients (e.g., iPhone) require a matching subject common name and matching subject alternative name (SAN) DNS name.  This attribute associates the authentication certificate with the S2S interface.  The destination flag is set to accept connection requests from any IP (i.e., it's dynamic).

Don't forget to lock down the VPN server.  Enforcing subject names does not secure the server.  Recall, Windows VPN server leaves its front door wide open -by default.  Windows VPN security requires manual changes:  http://www.stevenjordan.net/2016/10/door-wide-open-on-win-ikev2.html

Managing S2S connections via PowerShell:

Managing client connections is cumbersome compared to traditional RRAS client VPN tools.  For example, RRAS and Remote Access Management provide simple GUI tools to manage dial-up connections (Figure 1).  However, Remote Access Clients does not display S2S connections.  Additionally, RRAS Network Interfaces does display S2S interfaces by deafult.

Figure 1.  RRAS Client Connections.
The RRAS management GUI does not play well with dynamic S2S connections.  The Remote Access Clients tab does not display active connections.  However, the GUI will display active IKEv2 WAN Miniports:

Figure 2.  Active WAN Miniports.  Good enough.
PowerShell provides a better method to view active S2S connections:
PS C:\Users\SMJ> Get-VpnS2SInterface
RoutingDomain Name Destination AdminStatus ConnectionState
------ ------- ----------- ----------- ---------------
XXXXXX-XXXX-SMJ {0.0.0.0} True Connected

Dynamic S2S GUI-Powershell Hybrid

Alternately, create dynamic S2S interfaces with the RRAS GUI.  This approach offers some S2S client management benefits.  Keep in mind, these S2S interfaces use default cryptographic algorithms.  We'll need to modify S2S security targets with PowerShell:

Step 1.  RRAS → VNS server → Right-click Network Inerfaces → New Demand-Dial Interface:

• Interface Name:  Certificate's subject common name.
• Connection Type:  VPN → Next
• VPN Type:  IKEv2 → Next
• Hostname:  None (leave blank) → Next
• Protocols & Security:  Route IP packets on this interface → Next
• Static Routes:  None (or add based on your organization's needs).
• Dial-Out Credentials:  None → Next → Finish.

Step 2:  Edit S2S interface properties → Options tab.
• Connection type:  Persistent connection →  OK.

Step 3:  Edit security targets for S2S interface in PowerShell.
PS C:\Users\SMJ> Set-VpnS2SInterface -name xxxx-xxxx-SMJ -CustomPolicy -CipherTransformConstants AES256 -DHGroup Group14 -EncryptionMethod aes256 -IntegrityCheckMethod SHA256 -EncryptionType RequireEncryption

WARNING: VPN site-to-site adapter xxxx-xxxx-SMJ will be modified and the parameters 
other than IPv4Subnet/IPv6Subnet will be applicable next time the connection is dialed.

Check Hybrid S2S Connection from GUI:

 RRAS → VNS server → Network Interfaces:  Connection Status


Figure 3.  S2S connection status via RRAS GUI.

The RRAS Network Interface GUI now includes a list of S2S interfaces and connection status.  It also provides a simple method to disconnect or disable client connections.

Troubleshoot:

Use PowerShell to check server IPsec crypto-sets:
• Get-NetIPsecMainModeCryptoSet
• Get-NetIPsecQuickModeCryptoSet


Confirm server-client security targets work as intended:
• Get-VPNS2SInterface
• Get-NetIPsecMainModeSA
• Get-NetIPsecQuickModeSA

I also recommend using the Best Practice Analyzer (BPA) to check for any obvious S2S security warnings.
https://technet.microsoft.com/en-us/library/ee922676(v=ws.10).aspx


That's It!

CA Template for VPNs

Task: 

Prepare Windows CA certificate template for end-user enrollment.

Assumptions:  


  • These instructions are for situations that require minimal VPN support.
  • This solution only supports enrollment requests from the Windows certificate snap-in.
  • It enforces administrative approval for end-device enrollment -this is not a completely automated process.
  • Workplace Join is the preferred method for device enrollment.  It provides self-service automation.  It provides secure key management.  This walk-through is not for Workplace Join.

Steps:


  1. Open certificate templates.  From the Windows CA:  Start → MMC → File → Add Snap-In:  Add Certificate Templates.
  2. Step 2:  Duplicate User template:  Certificate Templates → Right-Click on User (Template) →  Duplicate Template.  
  3. Step 3:  Edit Properties of New Template (Table 1):


Table 1:  New Certificate Template Properties.
Field
General
Cryptography
Extensions
Security
Template Display Name
User Device Auth



Validity Period
3 Years



Publish in AD
Un-check



Minimum key size

2048 or 3072


Providers

Microsoft RSA


Applications Policies


Client Authentication

Authenticated Users



Allow Read
Allow Enroll
Note:  3072 key size increases security strength for IKEv2 VPNs.  Choose validity to fit needs of organization.  Use short validity period for automated self-service (e.g., Workplace Join).  Disable certificate exports for automated self-service.   

The template becomes available for user enrollment requests from any Windows certificate snap-in.

Connect iPhone to Windows VPN

Task:  

These steps are necessary to connect an iPhone to a Windows VPN server.  It explains how to
generate Apple iOS mobile-config scripts with Apple Configurator 2.  These mobile configuration scripts configure settings unavailable through the iPhone GUI (e.g., IKEv2 cryptography algorithms),

Requirements:

  •  Apple OSX running Apple Configurator 2
  • Server certificates:  Root_CA.cer and VPN_Server.cer(s).
    N.B., this process does not require the private keys for the Root CA or VPN server.
  • Client Certificate
       (a) Subject CN in username format (e.g., smj@stevenjordan.net).
       (b) Enhanced Key Usage (EKU) uses client authentication (1.3.6.1.5.5.7.3.2).
       (c) Subject Alternative Name with DNS attribute that matches the subject CN
             (e.g., DNS Name=smj@stevenjordan.net)
       (d) IKEv2 requires RSA (2048) SHA256 certificate.  

Administrative Process:

Process consists of three steps: (a) Create, (b) distribute, and (c) import the mobile-config.

Mobile Config

Create the mobile-config using Apple Configurator 2.  N.B., this process requires the Root CA and VPN server certificates (e.g., CER files).  The device certificate and private key is optional (i.e., device.PFX).  Additional PFX considerations:

  • IKEv2 VPN authentication requires PFX installation.  
  • Merging the PFX and the mobile-config provides the best user experience.
  • All PFX installations require special security precautions -regardless of mobile-config.
  • Self-service MDM makes administration easier..

Apple Configurator 2:  

  1. Start the Configurator and create a new profile:  File → New Profile.  Alternetly, edit an existing profile:  File → Open → Shoreland_Mobile_Config.
  2. General Tab:  Name, identifier (default), Organization, etc.
  3. Certificates Tab:  Import root.crt, VPN_server.crt.  Import device.pfx (i.e., client cert and private key (optional).
  4. VPN Tab:

    Table 1.  Apple Configurator 2 IKEv2 VPN Example.

Connection Name
 *
Connection Type
IKEv2
Server
VPN FQDN (public facing)
(e.g., vpn.stevenjordan.net)
Remote Identifier
VPN FQDN (public facing)
Local Identifier
Subject CN from client certificate.
(e.g., smj@stevenjordan.net)
Machine Authentication
Certificate
Identify Certificate (Optional)
Choose User_Device.PFX from pull-down menu.
Certificate Type
RSA
Server Certificate Issuer Common Name
Root CA Issuer (CN). 
(e.g., Jordan_Root_CA)
Server Certificate Common Name
VPN FQDN (e.g., vpn.stevenjordan.net)
IKE SA Params
Encryption Algorithm:  AES-256
Integrity Algorithm:  SHA2-256
Diffie-Hellman Group:  14
Child SA Params
Encryption Algorithm:  AES-256
Integrity Algorithm:  SHA1-96
Diffie-Hellman Group:  14

    5.  Save mobile-config:  
           File → New Profile.  Optionally Sign the profile.  Signing the code is optional and requires a certificate from Apple.  Save to an accessible location (e.g., Documents).

Distribute Mobile-Config

The safest method to distribute these mobile configuration scripts, especially those with private keys, is from a mobile device management (MDM) server.  Apple Configurator works as a secure MDM solution.  The process configures each device via USB. The process is not 100% automated -but it is secure.  http://simplemdm.com/2016/03/14/how-to-enroll-in-mdm-with-apple-configurator-2/

Alternately, organizations can distribute mobile-config scripts via email or web.   For example, use Outlook OWA, upload to a website, or use a corporate OneDrive.  Include the device.pfx if not incorporated in the mobile-config.  

Please consider the security risks associated with these alternative distribution methods. Certificates and private keys are used to validate identity.  We DO NOT want the wrong person to intercept this data.  It will allow them to authenticate to network servers, send email, etc...  Please use common sense.  Always delete private keys after installation is complete.     

Import Mobile-Config

Send the end-user an email with the mobile-config.  The email can include the mobile-config file as an attachment.  The end-user simply needs to open the attachment to start the installation process.  
  • Installation requires the end-user's device PIN.  
  • The end user will receive an alert that the mobile-config file is not signed
  • The end user must install user certificates and private keys (e.g. device.pfx) as required.  PKIs can be incorporated into the mobile-config script.
  • User may receive a warning that the PFX is not signed or trusted.

Additional Information:  

Alternatives to Apple Configurator:  Edit mobile-config XML scripts with Notepad++:  http://www.stevenjordan.net/2016/11/ikev2-mobile-config-script.html

How to add certificates and private keys within mobile-config XML scripts using Notepad++:
http://www.stevenjordan.net/2016/11/add-certs-to-mobile-config-xml.html

http://www.stevenjordan.net/2016/09/harden-rras-ikev2.html

Configure Windows Server IKEv2 VPNS:
http://www.stevenjordan.net/2016/09/secure-ikev2-win-10.html

Edit Certificates in Mobile-Config XML

Task:

Add user device certificates (e.g., PFX and CER) into Apple mobile-config scripts.  

Solution:  

Encode PFX and CER files with Base64.   Merge output with mobile-config script.  Specific solution steps are listed below.

Mobile-Config Background:   

Mobile-config scripts are simple XML documents.  The XML "code" holds any number of Apple iOS configuration settings.    These scripts are user-friendly and run on iPhones and iPads.  Network Administrators use these scripts for mobile device management (MDM).  For example, a mobile-config script can automatically configure VPN settings.

The Apple Configurator 2 is a free application that generates mobile-config files.  It has a user-friendly GUI and is a simple method to manage Apple devices.  Apple Configurator only runs on MacOS.  However, mobile-config scripts can be managed with any XML editor.  Simply copy existing scripts and make changes as needed (e.g., Notepad++).

Certificate Background:  

PKCS12 is an archive file that bundles a X.509 certificates and private key.  PKCS12 succeeds Microsoft's PFX archive.  However, PCKS12 and PFX files are interchangeable formats.  Organizations that use Windows CA work with PFX files.

CER is an extension of SSL and TLS certificates.  These files are simply X.509 certificates -without private keys.

IKEv2 VPN servers authenticate devices with X.509 certificates.  Authentication requires the user certificate and private key (i.e., PFX).  It generally requires the VPN server certificate and trusted root certificate (i.e., CER).   The mobile-config script provides a user-friendly method to configure IKEv2 and import PFX and CER files.

Solution Steps:  

  1. Use Certutil.exe to encode PFX file with Base64.  This process creates a new encoded file (*.enc).C:\source\cert>certutil -encode iphone.pfx user.enc
  2. Encode CER files (e.g., trusted root and VPN server) as needed.
    C:\source\cert>certutil -encode vpnserver.CER VPNServer.enc
  3. Open the encoded file with any XML editor (e.g., Notepad+).  Copy and paste its contents to the appropriate section within the mobile-confg script.  

Alternate Solution Steps:

Use Notepad+ to encode the PFX with Base64.

1. Open the PFX with Notepad++.
2. Select all text (CTL-A)
3. Right-click the highlighted text → Plug-In Commands → Base64 Encode.
4. The encoded text is ready for the mobile-confg script.  Insert this text to the appropriate section within the mobile-config script.

Merge Base64 

Instructions on how to incorporate Base64 PFX into mobile-config:  http://www.stevenjordan.net/2016/11/ikev2-mobile-config-script.html

Risks

Theses scripts are simple text files.  Bad things can happen if they fall into the wrong hands. Take precaution for mobile-config scripts that contain certificates and private keys (i.e., PFX):

  • It's best to distribute scripts via MDM solutions.  
  • These certificates should not be exportable.  
  • Do not install private keys on rooted devices.  
  • IT staff should assist with all manual installations.  
  • Implement a process to ensure safe handling of private keys.  
  • Ensure scripts that contain private keys are deleted when work is complete.  

References:


IKEv2 Mobile-Config Script


Task:  

Manually create and edit a mobile-config script for iPhone IKEv2 VPNs.  

Requirements:  

  • Script with a common XML editor -no need for Apple Configurator.
  • Use secure cryptography algorithms.
  • Include all certificates for mutual authentication:  User certificate and private key, VPN server certificate, and trusted root certificate.

Solution:  

  1. Preparation:  Encode certificates (e.g., PFX and CER) with Base64:
    http://www.stevenjordan.net/2016/11/add-certs-to-mobile-config-xml.html
  2. Copy the mobile-config script (below) to an XML editor -I personally recommend Notepad+
  3. Edit the mobile-config script.  Remove certificate payloads and replace them with output generated from Step 1.
    (a) User certificate and private key:  Lines 24 - 64.
    (b) VPN server certificate:  Lines 165 - 205.
    (c) Private root certificate:  Lines 225 - 245. 
  4. Change addition text fields to match your organization:
    (a) Consent:  Lines 9 - 10.
    (b) PFX Password:  Line 19.
    (c) PFX file name:  Line 21.
    (d) PFX Payload Display Name:  Line 69.
    (e) IKEv2 Local Identifier String:  Line 117.  N.B., This string must be the same as the user certificate's DNS name listed under in its subject alternative name.
    (f) Remote address (i.e., VPN FQDN):  Line 123.
    (g) Remote identifier (i.e., VPN FQDN):  Line 125.
    (h) Server certificate issuer (i.e., CA):  Line 127.
    (i)  User Defined VPN Name (optional):  Line 156.
    (j)  Server payload display name (e.g., VPN FQDN):  Line 210.
    (k) Root certificate file name (i.e., CER):  Line 222.
    (l)  Root CA payload display name:  Line 250.
    (m)  iPhone profile description:  Line 262.
    (n)  iPhone profile payload display name:  Line 264
    (o) iPhone profile payload identifier (change prefix):  266
    (q) iPhone profile organization name:  268
  5. Save file as:  File_Name.mobileconfig
  6. Distribute.
Please note, this mobile-config contains the user certificate and private key.  Ensure document is deleted from all sources after device configuration is complete.