AnyConnect Certificate Based Authentication.

[Marvin Ruiz]

The information in this document is based on these software and hardware versions:

    ASA 5510 that runs software version 8.2(2) and ASDM version 6.4(9)

    Anyconnect client  software version 3.0 (It will work the same for versions prior to 8.3)

    Microsoft Windows 2003 server as the CA server for the scenario.

Since the ASA version in use is 8.2.x we can enable per tunnel-group certificate authentication.

(Feature in the ASA 8.2.x release, using pre-8.2.x ASA code it will require to globally enabling the certificate authentication with the command

  "ssl certificate-authentication interface <interface> port <portnum>").

In order to acomplish the AnyConnect authentication using certificates the AnyConnect client should get a valid certificate from the CA server, at the

same time the ASA should have the CA Root certificate in order to properly validate the certificate of the connecting client.

1-) Make sure you have an AnyConnect image applied in the ASA firewall:

Configuration > Remote Access VPN > Network (Client) Access > AnyConnect Client Software

Click the Add button, and browse the flash for the proper image (optionally you can upload the client from the local PC).

2-) Enable anyconnect in the outside interface:

Configuration > Remote Access VPN > Network (Client) Access > AnyConnect Connection Profiles

Check the box "Enable Cisco AnyConnect VPN Client or legacy SSL Client"

Then select the interface where the AnyConnect clients will be connecting to (in this example the outside interface).

The " Allow user to select connection profile" check option will allow the AnyConnect user to select the group they will be connecting to.

3-) Create a new AnyConnect connection profile:

Configuration > Remote Access VPN > Network (Client) Access > AnyConnect Connection Profiles

Click the Add button, the "AnyConnect connection profile" window will open.

Give the connection profile a name and optionally a group alias.

Click the "Select" button next to the "Client Address Pools" option.

The " Select Address Pools" window will appear.

Click the "Add" button in order to create a new pool of addresses.

4-) Create a Group-policy:

Configuration > Remote Access VPN > Network (Client) Access > AnyConnect Connection Profiles

Click the "Manage" button  next to the "Group Policy" option in the connection profile.

Click the "Add" button in order to create the new policy.

Give the policy a name (In this example "AnyConnect-Policy") and check the "Clientless SSL VPN" and "SSL VPN Client" boxes, then click the "ok" button.

The AnyConnect group have been created at this point.

5-) Install the CA certificate in the ASA:

The CA certificate must be downloaded from the CA server and installed in the ASA.

Complete these steps in order to download the CA certificate from the CA server.

Perform the web login into the CA server CA-server with the help of the credentials supplied to the VPN server.

Click Download a CA certificate, certificate chain or CRL in order to open the window,

as shown. Click the Base 64 radio button as the encoding method, and click Download CA certificate.

Save the CA certificate with the certnew.cer name on your computer.

Go to Configuration > Remote Access VPN > Certificate Management > CA Certificates in the ASA firewall.

Click on the "Add" button, the "Install Certificate" window will open.

Click the "Browse" button next to the "Install from a file" option.

Browse to the location where you saved the CA certificate, highlight the CA certificate and click on the "Install" button.

At this point the CA certificate will be installed in the ASA fiwall and it willl be able to validate the connecting users, which user's certificate was created from the same CA server.

6-) Go back to the AnyConnect connection profiles and change the profile to use certificate authentication:

Configuration > Remote Access VPN > Network (Client) Access > AnyConnect Connection Profiles

Highlight the "AnyConnect-group" profile and click the "Edit" button.

The "Edit AnyConnect Connection Profile" will open, then you will be able to select the authentication method to be "Certificate"

Click the "OK" button and then click "Apply"

(Remember to save the configuration performed)

7-) The next step would be to install the certificate in the AnyConnect client PC:

The user will need to log in into the CA server with his credentials.

Once in the CA server, the user will need to click in the "Request a certificate" option.

The user will want to select the "User Certificate" option.

At this point the CA sever will provide the user certificate to be installed.

Once the certificate is installed the user will be able to connect the AnyConnect client authenticating with the previously installed certificate

(No username and password required)

Below you will find how the configuration should look like in the CLI interface:

ip local pool AnyConnect 10.10.10.1-10.10.10.254 mask 255.255.255.0

      group-policy AnyConect-policy internal

      group-policy AnyConect-policy attributes

        vpn-tunnel-protocol svc webvpn

      tunnel-group AnyConnect-group type remote-access

      tunnel-group AnyConnect-group general-attributes

        address-pool AnyConnect

        default-group-policy AnyConect-policy

      tunnel-group AnyConnect-group webvpn-attributes

        authentication certificate

        group-alias AnyConnect enable

         webvpn

          enable outside

          svc image disk0:/anyconnect-dart-win-2.5.6005-k9.pkg 1

          svc enable

          tunnel-group-list enable

crypto ca trustpoint ASDM_TrustPoint0

        revocation-check none

        no id-usage

        enrollment terminal

      crypto ca authenticate ASDM_TrustPoint0

        MIIEtDCCA5ygAwIBAgIQcNSMRXs696JMHFgTc+OKPjANBgkqhkiG9w0BAQUFADBV

        MRMwEQYKCZImiZPyLGQBGRYDY29tMRUwEwYKCZImiZPyLGQBGRYFY3J0YWMxFjAU

        BgoJkiaJk/IsZAEZFgZ2cG5sYWIxDzANBgNVBAMTBnZwbmxhYjAeFw0xMjA2MDUy

        MDAyNThaFw0xNzA2MDUyMDExNTdaMFUxEzARBgoJkiaJk/IsZAEZFgNjb20xFTAT

        BgoJkiaJk/IsZAEZFgVjcnRhYzEWMBQGCgmSJomT8ixkARkWBnZwbmxhYjEPMA0G

        A1UEAxMGdnBubGFiMIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEA2Wo7

        iCHElRUbgGAJgsf52AxlQLmeyMTSgS2I6/hTCOmra5BkP4cUieSeWqnOAPYgGTj/

        it3qGVLBjkjf2sHBUBHfIUm8nnQF2UNjTbJZVIfCAyrHoRXNDFNV6qlKFoMmi7VG

        2CudXsbuC86LsFDTMkk2Y2UB/T1xUpf5TBX+uQDb7w4jIZs1DkpQBmE946lH8vyA

        GHU6RdainLr/44Sa0iPjzngMdssq0QlE/8gYWr6HsAOvmKhf8RcokjqXEQ36JyAF

        +N/6sqoDTYl6jXg72PuoLO/zcmu8qbY+aRQGu5tlKXVemb9FyEKOuLe/Q4PirCz1

        TUHw8urOHcHCquo5PwIDAQABo4IBfjCCAXowEwYJKwYBBAGCNxQCBAYeBABDAEEw

        CwYDVR0PBAQDAgGGMA8GA1UdEwEB/wQFMAMBAf8wHQYDVR0OBBYEFNI2q3uAQNAg

        nR+BfjqEcGUZaHoNMIIBEgYDVR0fBIIBCTCCAQUwggEBoIH+oIH7hoG7bGRhcDov

        Ly9DTj12cG5sYWIsQ049dnBuLXNlcnZlci0wMSxDTj1DRFAsQ049UHVibGljJTIw

        S2V5JTIwU2VydmljZXMsQ049U2VydmljZXMsQ049Q29uZmlndXJhdGlvbixEQz12

        cG5sYWIsREM9Y3J0YWMsREM9Y29tP2NlcnRpZmljYXRlUmV2b2NhdGlvbkxpc3Q/

        YmFzZT9vYmplY3RDbGFzcz1jUkxEaXN0cmlidXRpb25Qb2ludIY7aHR0cDovL3Zw

        bi1zZXJ2ZXItMDEudnBubGFiLmNydGFjLmNvbS9DZXJ0RW5yb2xsL3ZwbmxhYi5j

        cmwwEAYJKwYBBAGCNxUBBAMCAQAwDQYJKoZIhvcNAQEFBQADggEBAEHyvayVbKqT

        0rwZNFBC3GAnUCDCK3kJxyjvir+T2pcCVS5KLukhTcDtr5VBOrSGsFA+zJvqB7qS

        dwAvh9tKjpdb6rQKM5bo7NKii7mU71WxK8/wSupLMlNEZemvZcnaLKB2P5TGwJ0K

        9LTp/rT89pvO9QbEMnRMPi0dPHQbu90sDLLBksxUfXII8qNyjjqNnVq2GDHX56Gz

        DzltLTLnrL4Gb/1M9ulwO2bzNV9J7uVg6iELJDbzkHFaCNXTvQJyDsN41xETg54Y

        uv6hViCXnu0SaaWi2rjVqx8pUXD7O3jrH9jnBC71cUqzv+MBvJI3th9iMMA80Gno

        Rl0Ipuf7dYk=

        quit

I hope this information can be helpful for you..

[luisram2]

Really useful. thanks

[mattbiggs]

Thank you for great post.

I've been looking to implement this solution.  One question I have is, instead of using a separate Microsoft Windows CA Server, can't you use the built-in ASA CA?

Thanks,

Matt

[Marvin Ruiz]

Hello Matt,

Thank you very much for your comments.

In answer to your question, yes It is totally possible to use the built-in CA server feature of the ASA in order to

Issue certificates to your SSL clients and perform certificate based authentication.

This would be the process:

1-) Create the Certificate Authority as shown below:

Follow the path below:

Configuration > Remote Access VPN > Certificate Management > Local Certificate Authority > CA Server

Check off the "Enable Certificate Authority Server" option and enter a passphrase.

Optionally you could configure a SMTP e-mail server in with the ASA could send the certificate information to your users, but in this example

We will work with the HTTP connection.

2-) You will need to add a user in the CA’s user database:

Configuration > Remote Access VPN > Certificate Management > Local Certificate Authority > Manage User Database

Select “Add” to add the “vpnuser”,

Enter the username and optionally the e-mail id.

You can also add specific values of the certificate subject name by using the “Select” button next to the “DN String” option.

Once the user is created it will have a status of allowed but no yet enrolled.

At this point you will want to generate the OTP in order to provide it to the SSL user.

Either connecting with the AnyConnect client or through the web vpn portal you will get the option to “Get Certificate” (If the group where the user is connecting to is configured for certificate authentication).

By clicking in the “Get Certificate” button you will be ask for the username and OTP

After you enter the correct username and OTP you will be provided with the user certificate for the install (depending on the OS you could be prompted with the option to save the certificate before installing it, if that is the case it could ask you for a passphrase for the installation, and it would be the same OTP that you entered to request the certificate).

After the certificate has been installed in the PC, the AnyConnect client will be able to establish the connection.

Below you can find how the commands will look like using the CLI:

crypto ca server

smtp from-address 10.10.10.10

       database path flash:/

       no shutdown passphrase cisco123

crypto ca server user-db add vpnuser

crypto ca server user-db allow vpnuser display-otp

I hope this can be useful for you.

[Julio Carvajal]

Hello Marvin,

What a great post!

Thank you very much for this information

[Gustavo Medina]

Very nice Marvin!

Adding my two cents to Matt's question; if you are using 3.0.08057 or later which you propably are since we don't recommend using earlier versions due to Security Vulnerabilities:

http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20120620-ac

You will need to also use cetificate matching on the XML profile, this is because starting in 3.0.08057 the client certificate MUST have the Client Authentication EKU however the certificates the ASA generates do not have a EKU, they just have the following Key-Usages:

Digital Signature, Non-Repudiation, Key Encipherment, Data Encipherment (f0)

From those Key Usages the AC client only needs Digital Signature and Key Encipherment, we opened an Enhancement Request to have the ASA add the necessary EKU to the certs is issuing.

http://tools.cisco.com/Support/BugToolKit/search/getBugDetails.do?method=fetchBugDetails&bugId=CSCua89091

--Gustavo

[Marvin Ruiz]

Hello Gustavo,

Thank you very much for the additional info, I was not even aware of it.

It is really helpful, I will keep it in mind.

Regards,

[mbstrauss]

Thanks Marvin,

Is possible to use ASA's built-in CA server when they are in failover mode?

Regards,

[Gustavo Medina]

Hello,

No, unfortunately is not possible...there is an enhancemet request for that though CSCsm17487 so you might want to contact your account team for more information about roadmap and stuff...It's not even supported on load balancing "oficially".

HTH

--Gustavo

[necamach]

What a nice document!

Thank you all!

[sal.mobin]

Hi Marvin,

Such a great document, I hope you will answer my questions... Is it possible to use both Certificate based authetication and RSA token based authentication using different profiles....currently my organization is using webvpn, anyconnect client, but I have a new requirement that some users want certificate based authentication so I am curious If I can follow these instructions and start certificate base authetications, Is it going to effect the existing ssl webvpn functionality.

Basically I want to run both Certificate based authenticationa and RSA token so I can provide users access accordingly.

Do I also need this image svc image disk0:/anyconnect-dart-win-2.5.6005-k9.pkg 1

currently I have following images in flash:

svc image disk0:/anyconnect-win-2.3.0254-k9.pkg 1

svc image disk0:/anyconnect-macosx-i386-3.1.00495-k9.pkg 3 regex "Intel Mac OS X"

svc image disk0:/anyconnect-linux-2.3.0254-k9.pkg 4

Thanks,

Sal

[elialope]

Sal,

Provided that you create a separate connection profile for the certificate authentication you can keep using both. You will need to have a group url and/or group alias for each one. I hope this helps you resolve your issue.

Elias

[Marvin Ruiz]

Hello Sal,

As Elias previously mentioned if you are about to create 2 separate groups in the ASA, one for certificate authentication and the other one for RSA authentication they should not interfere with each other.

However, as you can check in the information at the top of the post, the ASA firewall should be running an OS version of 8.2.x or later.

With 8.2.x we can enable per tunnel-group certificate authentication.

Feature in the ASA 8.2.x release, using pre-8.2.x ASA code it will require to globally enabling the certificate authentication with the command:

  "ssl certificate-authentication interface <interface> port <portnum>"

And the above command will affect the connections to all groups in the firewall, and also ASDM connections.

Regarding you question about the AnyConnect image installed in you ASA

It would be suggested that you upgrade to the AnyConnect version 2.5.6005 (Which is the one available in the Cisco web page) Since Cisco has remove the previous client versions from the public access due to vulnerabilities in the software:

http://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20120620-ac

I hope this information can be helpful for you.

Warm regards,

[sal.mobin]

Thank you Marvin and Elias. Currently I have 5510 ASA ver 8.2(5) and ASDM 6.4(7) running. I can see all the options that are posted above. The only ssl command that is configured in my ASA is "ssl trust-point ASDM_TrustPoint1 outside"

and this ASDM_TrustPoint1 is configured for third-party 2048 bit certificate so when user login through webvpn they see this certificate at the right corner of a browser. This certificate is also been used for IPSec VPN tunnel with vendors.

I am confused about the 2048 bit certificate currently installed it's been used for different purposes and the one that I will going to be using with the Annyconnect certificate based authentication....How are they differ from each other or want to make sure that the exsisting 2048 bit certificate will stay as it is when configuring the Internal CA certificate.

I do not understant "ssl certificate-authentication interface <interface> port <portnum>" command, is this command is necassary to configure as part of certificate based authentication procedure mentioned above or not....

Where can I find the group url and/or group alias option.... and ane last confusion is it possible to use the existing IP pool, or need a new ip pool  existing pool 192.168.104.150 - 192.168.104.200 /24

Thanks,

Sal

[burhanahmed]

Marvin can you kindly explain how i can enable anyconnect for smartphones (android) i have already enabled anyconnect but its not working for smartphones

Regards

Burhan

[Marvin Ruiz]

Hello Sal,

In answer to your questions,

What you need to upload to the ASA for certificate authentication is the server CA certificate, then it is not going to have any sort of conflict with the 3^rd party certificate already installed in the ASA.

The command "ssl certificate-authentication interface <interface> port <portnum>" is required just for version prior to 8.2.x, since your ASA is running 8.2.5 you will not need to use this command.

Also, you can use the same IP local pool configured in the ASA for the new connection profile.

In the above configuration example I am adding a group alias to the connection profile.

Please check the above configuration example; it contains all that you require for your set up.

Best regards,