Hasain Alshakarti

Yet another day of troubleshooting DirectAccess, this time it was my colleague and friend Mikael Nystrom asking about expired IPHTTPS and NLS certificates. He already knew about my other post about changing the IPHTTPS certificate.

So he did delete the old binding by using the [netsh http del sslcert] command for both external addresses, and did replace the binding by using the [netsh http add sslcert] and/or the IIS management console.

Now the DirectAccess server is restored in functional state again but Mikael realized another error, the DirectAccess Management Console started showing an error about not being able to read the XML config file due to errors in certificate hashes for the IpHttpsCertHash and NidCertHash?

Now my advice was to manually edit the %WINDIR%\DirectAccess\DirectAccessConfig.xml file and replace the certificate thumbprints in the file with the new ones from the renewed certificates. But the console was still complaining about the hashes! After some thinking and when comparing the old and the new config files we realized that the console needed the certificate hash values in CAPITAL letters!!!!

Yes, the certificate hash/thumbprint is a hex representation, and according to W3C XML Schema Part 2: Datatypes Second Edition http://www.w3.org/TR/xmlschema-2/#hexBinary:

hexBinary has a lexical representation where each binary octet is encoded as a character tuple, consisting of two hexadecimal digits ([0-9a-fA-F]) representing the octet code. For example, “0FB7” is a hex encoding for the 16-bit integer 4023 (whose binary representation is 111110110111).

Reading the above carefully, any developer can simply realize that the expression “digits ([0-9a-fA-F])” means not case sensitive, but this does apparently not apply to whom ever developed the DirectAccess Management Console in Windows Server 2008 R2

To change any of the IPHTTPS or NLS (if NLS is running on the DA server) certificate and keep the DA Management Console happy:

• Redo the certificate bindings either using the netsh http del/add sslcert command or the IIS console
• Change the IpHttpsCertHash and NidCertHash in the DirectAccessConfig.xml file and make sure the hash value is in CAPITAL letters

If you happen to know the person responsible for this at Micrososft, please give him/her the link to W3C 😉

Yet another day of troubleshooting DirectAccess, this time it was about a broken IPHTTPS tunnel. During the troubleshooting we recognized that the client is not able to establish a connection the the IPHTTPS url https://da.domain.com/IPHTTPS, using a network sniffer we could very clear see the server sending a reset packet after the Client Hello message. This indicates that the SSL server is not able to continue communicating using SSL. Knowing that there was a certificate change just a few days before this error occurred we found that the old certificate was still used for the SSL binding at the DA server even though the configuration was reapplied using the DA management console after the certificate change.

When changing the certificate used for the IPHTTPS tunnel it is very important to clear the old SSL certificate binding before adding the new one.

If you configured your DirectAccess using the DA management console follow the steps below to change the IPHTTPS certificate:

·         Run the command: netsh http show sslcert
This will show the current sslcert binding with details about ip, port and the certificate

·         Delete the old bindning using the command: netsh http del sslcert

·         Using the DA management console, select the new IPHTTPS certificate, save an apply the new configuration

If you configured your DirectAccess using scripts or netsh commands to define all setting follow the steps below to change the IPHTTPS certificate:

·         Run the command: netsh http show sslcert
This will show the current sslcert binding with details about ip, port and the certificate

·         Delete the old bindning using the command: netsh http del sslcert

·         Add the new sslcert binding using the command: netsh http add sslcert

/Hasain