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Task:

How to manually request and enroll certificates for BYOD devices with Windows CA server.

Background:

Automated mobile device management (MDM)  (e.g., Microsoft Workplace-Join,) provides a secure method for device key management.  However, rolling out the right MDM solution can be a serious undertaking.  It may be overkill for some organizations.

This article covers device key-management for special use situations.  It provides instructions on how to manually generate device (e.g., iPhone) certificates for mutual authentication (e.g., IKEv2 VPNs).

Assumptions:

Solution:

Step 1:  Request the device certificate from from any workstation:

  • Start → MMC → File → Add Snap-In:  Add Certificates - Current User
  • Certificates → Current User →  Personal → Certificates → All Tasks → Request New Certificate


Step 2:  Complete the Certificate Enrollment Wizard:                 

  • Select Policy: No changes.  Click Next.
  • → Request Certificates:  User Device Auth → Click Details →  Click Properties.
  • → Certificate Properties:      

        →  [Subject Tab]
                  Subject Name:
                       Common Name (CN) = user_device@stevenjordan.net;  add.
                       Email = user_email@stevenjordan.net;  add. Given Name:  First and last name; add.
                  Alternative Name:
                        DNS = user_device@stevenjordan.net; add. N.B., DNS must match Full CN.
                        Email = user_email@stevenjordan.net; add.
         → [General Tab]
                   Friendly name:  user_device@stevenjordan.net
         → Click OK.

         → Request Certificates:  Add checkmark for User Device Auth → Click Enroll.
  • Note that status = Pending.
Step 3:   Approve request from Certificate Authority (CA) server.  

  • Open CA Server  MMC:
       → Certification Authority (Local) → Root-CA →  Pending Requests → Issue: 
Step 4:  Export certificate from workstation that initiated request:  
  • Certificates → Current User →  Certificate Enrollment Requests:
    → Certificate Export Wizard
         → Export Private Key:  Yes, export the key.
         → Export File Format:  Check Include all certificates in path.  Next.
         → Select Policy: No changes.  Click Next.
         → Security:  Check Password.  Enter Password.  Next.
                               N.B., Password = choose_password
         → File to Export:  Choose location:  C:\source\cert\user_device.pfx.  Next.
         → Export Root Certificate and VPN server certificate:  Location: \\securefileshare\
  • Repeat similar process to export CA public root certificate (CER).
  • Log onto the VPN server and repeat similar process to export public certificate (CER).
Step 5:  Distribute certificate files to client devices.
  • Distribute the client certificate and private key (e.g., PFX).  
  • Include the public VPN server and root certificates (e.g., CER).

Distribution methods: 

Security Considerations:

Safeguard your client PFX files!!  PFX files include certificates and their private keys.  An attacker can use this information to impersonate identity.  That means, it can be used to connect to the VPN, collect email, etc.  Do not let these PFX files fall into the wrong hands!  Mitigation:
  • Account for all PFX instances -these are security vulnerabilities!
  • Delete/ remove all device certificates generated from workstations.
  • Save client PFX file to secure off-line media. 
  • Consider IT policy that requires face-to-face installation with IT staff.
  • Email attachments can be forwarded -risk!
  • Internal web server on internal Wi-Fi SSID is preferred.  
  • Ad-Hoc Wi-Fi may be preferable to infrastructure mode. 
  • Do not enable the certificate's export flag.
  • Do not install on any rooted or jailbroken device.  
  • Ensure devices use encryption and passcodes.
  • Above all, use common sense!

That's It!

About Unknown

Steven Jordan is an infrastructure and process management specialist. Steven holds a Master of Science degree in ICT from the University of Wisconsin Stout. Steven is also a Cisco Certified Network Professional (CCNP) and Master Gardener.
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