Alan Baugher

Using Wireshark to decrypt Active Directory traffic from the CA Identity Suite

Discussion created by Alan Baugher Employee on Dec 30, 2016
Latest reply on Feb 2, 2017 by Alan Baugher

Team,

 

Recently a customer asked for help with acquiring an Active Directory server for the CA Identity Manager (CA Identity Suite).  The customer already had one (1) ADS domain acquired, and wished to acquire a 2nd ADS domain (Company had merged with another).

 

This is usually a straight forward process.    

 

Minimal information needed is

-  hostname of DC server,

-  service ID & password  (if not Administrator, then a delegated service account with CrUD permissions),

-  the public root CA certificate from that AD server or AD domain (which had signed a server cert).

 

I typically have customer use a 3rd party ldap client tool, e.g Jxplorer or SoftTerra LDAP browser tool to confirm they have the correct service ID/password & public root CA cert.     Other tool is the IMPS\bin\adsldapdiag.exe  to validate serviceID/password.

 

If there are issues with the SSL/TLS security, I will have the customer navigate to the IMPS\bin folder  (or IAMCS\ccs\bin) and use the openssl.exe binary.

 

1)  Save the public CA certificate (and any intermediate CA) as a PEM format (base64 - that you can open in notepad to see BEGIN  END statements).   [May also do pks format]

2)  Execute  openssl  s_client   -connnect  hostname:636  -showcerts  -CAfile  c:\temp\ads-ca-file.pem

 

If the above returns success, then we know we have the complete TLS chain.  

 

However, for this one customer, they were successful with all the above, but their remote Active Directory domain, still reports that "confidential required" error message.      We ensured that the public CA and the customer intermediate CA were being referenced correctly.

 

 

To isolate this issue, we reviewed the customers'

 

1) Server Certs

   -  One delta was use of SANS and no CN

        -  Validate in my own lab this is not an issue

       -   Had to install MS CertSrv to generate the correct SANs with a <null> CN, then used openssl to sign it.

       - No issues for openssl, 3rd party ldap client tools, nor Identity Manager/Suite via IAMCS to CCS.

 

2)  ADS Group Policies - CIS harden

-      Customer used various CIS recommended hardening policies

   -   Had customer export their GPO and I used the MS tool SCM v4.0 to load them into my lab.

  -  validate they had no impact on the issue.

 -   note:  MS SCM is a great tool to compare GPO instead of doing this manually via eye-ball 1.0.

 

 

 

I needed to dive deeper; and the debug logs of IAMCS, CCS and Active Directory were not enough to isolate this issue.

 

 

######   The use of Wireshark to monitor all traffic #####

 

 

I have used the CA Identity Suite vApp (Virtual Appliance/IDVA) as my new base lab solution; deploying the IAMCS/CCS service twice; updating the IAMCS configuration file to use the remote CCS service (to allow use of Wireshark); enable the debug logs; changed the default Cipher Suite for Active Directory.

 

Below image of lab:

 

 

 

Wireshark was able to capture when a NEW ADS endpoint is acquired for the 1st time.    I wanted to see WHEN the CCS service validated the SSL/TLS certificate and how that was viewed.

 

There are four (4) TLS transaction between the CCS service and the ADS endpoint.

1) Initial Client Hello   -   Listing all the available Cipher protocols that CCS has access to.

    -  No decryption at this stage yet.

2) Initial Server Hello   -  Selects the highest (or order) Cipher protocol provided, that it shares with the client.

     -  Shares the server certificate, that will display "server authentication" use, and the SANS value for the DNS entry 

    - No decryption at this stage yet.

3)  Certificate Key Exchange - Able to view the successful negotiation.

    -  Able to view de-crypted data with server private key.

4)   Change Cipher Spec -   Appears to be the final step;  little value

-   All other communication is now seen as "LDAP" over TCP 636 and can be viewed as decrypted data.

 

 

 

Note:  By default, Active Directory Cipher Suite uses the Diffie-Hellman key exchange process.    Diffie-Hellman key exchanges can NOT be decrypted with the RSA private server key, as the session key is built in memory between the client and server.

 

 

Example of RSA Cipher Used for Active Directory:

 

 

Example of Server Certificate with <null> CN and use of SANS DNS entry

 

 

A view with using OpenSSL to check Cipher Suite.   Below is an example with Diffie-Hellman Cipher Suite, that is not possible to use Wireshark with.     When Cipher Suite order is changed, the MS Windows Server must be rebooted (or schannel service restarted).

 

 

After a reboot of the server, and re-validation with openssl

 

 

 

Where to change the ADS Server Cipher Suite order:

 

I kept the following SSL Ciphers Suites to allow Wireshark to use the server's private ssl key.  Note that both are RSA cipher suites.

 

TLS_RSA_WITH_AES_256_CBC_SHA256,TLS_RSA_WITH_AES_128_CBC_SHA256

 

How to read a SSL Cipher Suite?   Cipher Suites in TLS/SSL (Schannel SSP) (Windows) 

 

 

 

 

A view of all Active Directory (2012) SSL Cipher Suite protocols:

 

 

What to enable within Wireshark, to monitor ADS over TLS?

 

 

How to export your Active Directory server key w/private key?  See below using MS tool "certlm.msc"

 

 

Save as PFX files and add to Wireshark as is, with the password.

 

Or convert from PFX to PEM (with openssl), and add as PEM files to Wireshark with no password

 

 

 

Note:   If the ADS Cipher Suite has NOT been updated, then you will receive this error message in the Wireshark logs

 

 

 

How to export your de-crypted ADS traffic to a text file?  Use the below Wireshark Export process, select the following check boxes.

 

 

 

 

 

 

Hopefully, you will find some value of this process and research.

 

 

I am enclosing attachments of an ADS endpoint acquired for the first time (over TCP 636), in various Wireshark export formats.   You will likely find value within the TXT format.

 

 

 

 

Cheers,

 

Alan

 

 

Edit:  3/5/2018.   Move to CA Security community.

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