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| KB | 0000335 | |
| Dated | 01/10/10 | |
| Revision | 0.02 | |
Securing Cisco SSL VPN's with Certificates |
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Problem |
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| It's been a while since I wrote a walk though on the Cisco AnyConnect/SSL VPN solution, and usually I secure these with Active Directory or simply using the local user database on the firewall. But what if you wanted to use certificates instead? Perhaps your users are too "technically challenged" to remember their passwords. Or you want to enable two factor authentication with usernames/passwords AND certificates (something you know and something you have). | ||
Solution |
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Step 1: Setup the ASA as a Certificate Authority |
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After version 8 Cisco included a complete CA solution in the firewall with a web front end. to use it we need to a) turn it on, b) give it an email address, c) provide a subject name, and finally d) create a unique pass phrase to generate the root certificate from. Connect to the firewall and carry out the following, |
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PetesASA> % Some server settings cannot be changed after CA certificate generation. Re-enter passphrase: ******** Keypair generation process begin. Please wait... Completed generation of the certificate and keypair... Archiving certificate and keypair to storage... Complete |
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| To do the same via ASDM connect to the ASDM > Navigate to Configuration > Remote Access VPN > Certificate Management > Local Certificate Authority > CA Server > Fill in the details > Apply. | ||
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| To check that the CA Server is up and running issue a "show crypto ca server" command. | ||
PetesASA# show crypto ca server Certificate Server LOCAL-CA-SERVER: Auto-Rollover configured, overlap period 30 days |
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Step 2: Obtain a Client Certificate |
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| If you have a LOT of these you can set them up and send them by email directly, I'm just going to do this one manually, By default your webvpn probably isn't enabled on the "inside" so lets turn that on. | ||
| PetesASA# PetesASA# conf t PetesASA(config)# webvpn PetesASA(config-webvpn)# enable inside INFO: WebVPN and DTLS are enabled on 'inside'. PetesASA(config-webvpn)# exit PetesASA(config)# |
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| To do the same via ASDM connect to the ASDM > Navigate to Configuration > Remote Access VPN > Network (Client) Access > AnyConnect Connection Profiles > Tick both the inside options > Apply. | ||
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| Now I'm going to create a user, and a "One Time Password". | ||
PetesASA(config)# PetesASA(config)# |
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| Via ADSM it's a little more convoluted, you need to add the user then view/re-generate the OTP. | ||
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| Open a web browser and got to https://{ip or name of firewall}/+CSCOCA+/enroll.html log in with the details you created above. | ||
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| When prompted download the certificate and put it on the machine that requires secure access. Simply double click it and import it (it should import into the "Personal Certificates" folder.) - if you are prompted for a password you enter the OTP from above. | ||
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Step 3: Change the VPN authentication to Certificate. |
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| First lets check that enrolment was successfully with a "show ca server user-db" command. | ||
PetesASA(config)# |
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| Change the webvpn authenticate to certificate. Note your SSL tunnel group WILL have different name. | ||
| PetesASA# conf t PetesASA(config)# tunnel-group SSL-VPN-POLICY webvpn-attributes PetesASA(config-tunnel-webvpn)# authentication certificate PetesASA(config-tunnel-webvpn)# exit PetesASA(config)# |
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To use usernames AND certificates use "both" instead of "cert", to Revert back to usernames enter "aaa" |
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Via ASDM |
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| Step 4: Test | ||
| Connect to the VPN portal and you should now be prompted for certificate authentication. | ||
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| References - Credits - Or External Links | ||
| Cisco ASA 5500 - Using a Third Party Digital Certificate (For Identification, AnyConnect, and SSL VPN)
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