When trying to add a new certificate template to a profile template in FIM CM 2010R2, the product tries to enumerate all existing certificate templates in the configuration partition of Active Directory. When an organization has a large number of complex templates (with large ACLs, etc.) FIM CM times out while trying to enumerate them.
This is both an undocumented issue and a rare occurrence. I could (partly) reproduce this, by adding around 400 certificate templates in a FIM CM lab. The result was that the FIM CM certificate templates web page appeared after around 60-90 seconds, instead of the 5 seconds that the page takes to appear using the default templates loaded by AD CS.
There is a workaround that solves the problem – add an explicit Deny Read ACL for the CLMAuthagent account (or, even better, a security group that contains this account) to all templates that are not going to be used by FIM CM. This in effect makes the product unable to read them and thus prevents the timeout while doing it.
Having fun with Virtual Smart Cards for S/MIME usage (part 2)
After a long time of inactivity, we are back with the second part of this mini-series of the virtual smart card deployment guide.
Configuring Outlook
Luckily (or, should we say, by careful design?) there are very few things to configure in the Outlook client. The certificate(s) that we are going to issue, either encryption or digital signature ones (or both), are going to be immediately recognized by Outlook. Subsequently, they are going to be placed in the correct containers, which can be seen by taking a look at File -> Options -> Trust Center -> Trust Center Settings -> Email Security -> Settings. There, we can find the relevant text box which will indicate the encryption and the signing certificates. If we create two different certificate templates for the relevant purposes, Outlook will automatically understand the purpose of each certificate and place each one in the correct container. If we create one certificate for both purposes, which is not recommended due to the sensitive nature of the signing operations, Outlook will use this one for both operations and you will see it both text fields in that window.
One more thing to note about Outlook is that the sign and encrypt buttons will appear in the Outlook’s “New Email” window only after the first encryption or signing takes place. This is a bit awkward for users. One way to circumvent this behavior, and thus “instruct” Outlook to always show the buttons, is to push a specific registry to Outlook clients. This key can be found at HKEY_CURRENT_USER\Software\Microsoft\Office\15.0\Outlook\Preferences. The new entry should be SecurityAlwaysShowButtons (as a DWORD) with value 1. This example refers to an Outlook 2013 client, so for previous versions of Outlook, we need to replace 15.0 with the specific version (for example, 14.0 for Outlook 2010 etc.)
Creating the virtual smart card
We create a virtual smart card in the user’s PC by opening an administrative command prompt and running the following command: tpmvscmgr.exe create /name VSC /pin prompt /adminkey random /generate. Let’s explain what this command’s parameters mean (more information can be found in the Understanding and Evaluating Smart Cards document):
- name refers to the name that we give to the virtual smart card – it could be anything we choose.
- Pin is, of course, the PIN that protects the VSC – in this case, prompt prompts the user to enter one of his/her liking. It is highly advisable that, at this point, the PIN should be entered by the user and be known only to him/her. The documentation has small error at this point.
- Adminkey is the administrator key that can be used to administratively access the VSC and reset it, if locked
- Generate is needed if we are not using FIM CM for the creation of the VSC (which, by the way, is highly recommended for most demanding deployments)
The process of TPM virtual smart card creation will take some time (usually around 2-3 minutes, depending on the hardware). You have to wait until the final confirmation by the system is displayed. The Instance ID of the virtual smart card reader should appear as ROOT\SMARTCARDREADER000 by default. We can also verify the creation be checking the Device Manager, where we will find the newly created reader with the name that was entered at the creation command.
In the next post, we will share some final details on VSC creation and Outlook.
VSC in Device Manager
Process of virtual smart card creation
Having fun with Virtual Smart Cards for S/MIME usage (part 1)
Recently, at one of our larger Premier customers, we designed and implemented (initially in a lab environment) a Certification Authority, mostly for SMIME usage. During initial discussions, we considered virtual smart cards (VSCs) for his Windows 8 computers. The experience was interesting enough to guarantee at least two blog posts 🙂
In this first part, we are going to describe the prerequisites and prepare everything for a successful virtual smart card rollout.
Starting from the clients – TPM chips
We are not going to get into details about TPM architecture, as there is abundant information in the internet. We will just mention the details which are important for VSC implementations.
First off, we have to make sure that the computers which are going to be part of the implementation actually contain a TPM chip. I was not planning to mention that at all – however, I found out that there are computer (and/or motherboard) manufacturers who claim to support TPM instead of supplying TPM chips within the systems. This is especially true in desktop computers, some of which might have a TPM slot, but no TPM module inside. So, you have to make sure that your systems do actually contain the module before rolling out the VSCs.
After that, make sure to enable TPM support in the BIOS’ settings. This is the most common mistake, as many people fail to understand that even if a computer has a TPM chip, most probably it is not enabled by default in the BIOS. Finally, after initializing TPM on Windows (http://technet.microsoft.com/en-us/library/cc753140.aspx), we are ready to set up our Certification Authority (CA).
Back to the CA – Virtual Smart Card Certificate template
We are not going to describe how to setup a CA, since it is out of the scope of this blog post. However, it is essential that we get into details about how to properly create the needed certificate template for VSC issuance.
Since VSCs are not that much different from a regular smart card (at least from a CA perspective), the steps that we have to perform in order to configure the VSC template are pretty much the same as the ones for a real, hardware smart card deployment. The certificate template that has to be duplicated is, as expected, the Smartcard Logon one and the fields that have to change are in the following tabs:
a) In the General tab, we just have to label the duplicated template
b) In the Request Handling tab we have to change the Purpose to Signature and smartcard logon. If not already selected, we should select Prompt the user during enrollment. Finally, we should click Requests must use one of the following providers and select Microsoft Base Smart Card Crypto Provider.
d) Since we are going to use the resulting virtual smart(s) for S/MIME operations, we should also make sure that the fields in the Subject Name tab include e-mail name in subject name and E-mail name are also checked.
- Virtual smart card settings for SMIME
Now we are ready to delve into the wonderful world of virtual smart card deployment. In the next blog post, we are going to visit the client once again, prepare it for VSC issuance, issue the VSC and configure it for Outlook/Exchange S/MIME operations.
Strong key protection for Windows client’s private key encryption operations
During customer visits, I am often asked what is the most secure way to store and handle private key material. As we probably all know, two-factor authentication methods are the ones that are usually described when private key protection is of the utmost importance. So, in case of storing the private key of an Offline or Issuing Certification Authority, a Hardware Security Module (HSM) would be proposed, and for digitally signing emails or documents, a smart card would be ideal to store the key pair. Some companies, however, are reluctant to introduce hardware devices to their environment for two reasons: a) they believe they will add complexity to an already complex IT environment and that would degrade the end-user experience and b) they are not prepared to bear the added cost. In case of smart cards, that would amount to a pretty cheap device (around $20-40 or more, depending on quantity and software used). In both situations, the companies’ IT (or Security) departments do have a point, but they usually still need to have an extra layer of security for their end users. So, is there any “poor man’s added security” for private key usage?
Strong key protection while enrolling a certificate
Strong key protection password window during enrollment
Well, in the client-side of the Windows PKI world, the folks that designed CryptoAPI added an extra security feature called strong key protection. In essence, what strong key protection does, is to force the user to enter a user-defined password which protects the private key whenever (almost, as we are going to see later on) this is going to be used for a cryptographic operation. When such an operation (for example, digitally signing an email) is performed, the user will have to provide this password and only then the underlying client (Outlook, in this case) will be able to have access to they key.
The prerequisites to enable and use this feature are to select the relevant option in the Request Handling tab of the certificate template, and then have the user enter a password during user certificate enrollment. There are two caveats here that are hard to spot: a) there is now way to force a user to select the High security option and b) once you enter the password in Outlook, for example for signing or decrypting, the system will not ask for it again except if you close and re-open the application. Moreover, the password entered by the user if the certificate is generated by a Windows XP client will not conform to the domain policy’s complexity requirements – Windows Vista and later clients, though, will conform to it.
Partly due to the previously mentioned problems, but mainly due to the fact that strong key protection is not an actual two-factor authentication, I do not recommend it as a viable security solution for handling private key material. However, there are organizations where security is not a top priority, and it’s good to have choices 🙂
- Certificate template settings for strong key protection
Troubleshooting certificate autoenrollment
Troubleshooting one of the most important and versatile parts of the Windows PKI world is a fairly complex process, since it involves a plethora of prerequisites in order for it to work correctly. Most of the times, consultants and administrators create a lab before a PKI deployment where autoenrollment usually works relatively easy – especially if the lab does not resemble the true production environment in anything other than the domain names.
In a very recent Windows PKI lab deployment for a major customer, we had a fairly lengthy autoenrollment troubleshooting session. The lab setup was a close-match replica of the production environment, as the Active Directory has been recreated using a backup of an actual production domain controller, as well as restored Exchange servers. The case was interesting: as it always seems to happen, everything was in place for autoenrollment to work, yet the process would not fire up at all.
To make a long story short, and after finding that no firewall, virtualization or general networking issues were involved, we finally tracked the autoenrollment failure down to two issues: the one is frequently seen in large organizations and has to do with GPO (Group Policy Object) precedence and settings’ overlapping. In our case, a GPO with no autoenrollment configured would prevail in the OU that the auto-enrolled users would reside and thus would not push the relevant settings to the clients. The second issue, however, was much more complex to target: as the environment has been set up many years ago, many administrators and third-party software packages have made a lot of changes in the production. One of the changes we found out that created problems, was the membership of two built-in groups: the Users and the Certificate Service DCOM access group. In the first one, the default membership should consist of Authenticated Users, Domain Users and Interactive (it did not, as you can imagine). In the second one, the Authenticated Users group should exist as a member (again, it was not – the list was empty).
We should say that in cases of autoenrollment failures, one should focus on:
- Certificate template security – make sure your users/computers have Read, Enroll and Autoenroll permissions and that the Authenticated Users group has not been deleted (it should be there with Read-only permissions).
- GPO precedence – make sure that you create a separate, enforced GPO to enable autoenrollment or, at least, that the GPOs applied to your users/computers finally lead to an enabled state for autoenrollment (RSOP is a great client-side tool to discover such issues).
- Group membership – the Issuing CA’s computer account should be a member of the Cert Publishers group in the intended enrollment domain; also, the Users and the Certificate Service DCOM Access built-in groups should have the membership detailed previously in this post.
- Server-side certificate issuance errors – a poorly configured certificate template (for example, one that requires an e-mail address in order for certificates to be issued when some user accounts may not have an e-mail address in AD) could lead to a certificate issuance request that is left in a pending or failed status, as seen in the Certification Authority console. Do check this by manually initiating a certificate request through an MMC console or a Web enrollment page (if configured) and make sure that the manual enrollment method actually succeeds in creating the intended certificate.
- Networking issues – blocked ports (RPC, HTTPS etc.) as well as problematic networking software or hardware (drivers etc.) could lead to problems in autoenrollment, Again, check if a manual request can succeed.
Update for CTLs in disconnected environments
In June 2013, Microsoft issued an update that makes the update of CTLs (Certificate Trust Lists) easier in disconnected environments. For the purposes of automatic updating, Microsoft considers any environment that does not have access to the Windows Update site as “disconnected.”
The new update enables Windows PKI administrators to:
- change the update location from the predefined Windows Update URL to an intra-organizational shared folder that is reachable from disconnected clients
- selectively disable/enable updating of either trusted or untrusted CTLs
- create a custom set of trusted root certificates and distribute it via Group Policy.
The relevant knowledge base article can be found here, and its supporting documentation here. It is worth noting that the update is included in Windows Server 2012R2 and Windows 8.1, and does not apply to Windows XP and/or Windows Server 2003.
Microsoft advisory and update on MD5 deprecation
On August 13th, Microsoft released a security advisory update (2862973 – Update for Deprecation of MD5 Hashing Algorithm for Microsoft Root Certificate Program), applicable to Windows Vista/2008 and later client and server operating systems. According to the associated TechNet article (Protecting Against Weak Cryptographic Algorithms) the functionality is already built into Windows Server 2012R2 and Windows 8.1 preview editions and should be included when the final bits of 2012R2 and 8.1 ship. Essentially, this update gives administrators control on logging and/or blocking weak algorithm-based certificates that are known to be vulnerable to multiple attacks. More detailed information can be found on the link above.
Credential roaming: is it worth the hassle? (Part 2)
In this second part of our discussion on Credential Roaming, we are going to discuss about its relation to key archival as well as offer some practical alternatives to credential portability.
As we saw in the previous blog post, the capability of “transporting” private keys in Active Directory is one of the basic pillars of the process’s ability to roam credentials. However, this should in no way be seen as a good way of backing them up for future restores. The procedure that should be used for key backup is the Windows PKI process of Key Archival and there is no way of replacing this with credential roaming’s private key “upload” process. In fact, even though private keys do reside inside the AD database, there is no known or supported way of extracting them in any form, in case of disaster recovery procedures. Moreover, if the user deletes his certificate along with his private key from one of his profiles, this deletion will propagate into all other profiles where the certificate has roamed to.
Even though it has already been mentioned in the previous blog post, it is worth noting that an easy and quick workaround for credential roaming is the use of roaming user profiles, which (of course) involves a lot more administrative costs and changes in relation to the activation of credential roaming in ΡΚΙ. In accordance to this, the concurrent use of user profile roaming and credential roaming is not supported.
Another workaround (although not as automated as Credential Roaming) is the storage of certificates and private keys in a smart card. This solution does make the user’s credentials available in every PC that he logs on to, however it assumes smart card hardware availability (this can also be a USB-based token) and also assumes a planned or existing smart card infrastructure, which does come with high deployment and administrative costs. However, a carefully planned and executed smart card deployment can furthermore be used for other applications, like VPN remote access, local computer and RDP user login etc. In general, and independently of the fact that a smart card deployment is a good alternative to credential roaming, the use of smart cards is recommended in all medium- & high-security PKI deployments, as many security officers are not happy with the storage of private leys inside an operating system (inside non-dedicated devices, in general).
Credential roaming: is it worth the hassle? (Part 1)
Credential roaming is the ability of a Windows Server PKI infrastructure to support roaming certificates from a Windows computer to another Windows computer, according to where a user is logged on. The way it works is as follows: when a user requests a certificate, its local operating system generates a private and public key and, using a secure channel between the computer and the CA, it uploads the private key and the signed request to the CA. The private key is securely stored in Active Directory and can later be downloaded to any PC that a domain user logs on to.
All this is fine and dandy and, based on specs, it is the perfect solution for users that tend to use a multitude of computers for their business use. However, setting up the infrastructure to support it is not as easy as one would have thought. In this post, we will take a look at some of the disadvantages and difficulties of credential roaming. In the post to follow, we will make some more general observations as well as offer some alternatives to credential roaming. So, to cut a long story short, credential roaming:
- Demands a complicate (but not very time-consuming) procedure of installation and use, as well as many scenarios to be tested to make sure it works as expected.
- Extends the physical size of the Active Directory database, according to the issued certificates to be roamed. If the service is extended to a few hundred or thousands of certificates, we may have an AD database which will grow to a few hundred MBs larger. Accordingly, the AD backup/restore time will be bigger, the AD database will become more fragmented etc. Microsoft Support has been involved in many support cases where a sudden increase of the Active Directory database has been attributed to the activation of credential roaming.
- Demands Windows XP SP3 or Windows XP SP2 with a specific update, Windows Vista , 7 or 8. It does not support other operating systems (for example, mobile OSs).
- Needs difficult and time-consuming troubleshooting techniques for Windows XP (Vista/7 use CAPI2 logging, so it’s easier there).
- Increases the organization’s attack vector. In case we don’t use enhanced security measures at the PCs that will use private key actions (i.e., lock workstation, Bitlocker protection, users’ security training etc.), using multiple points where certificates are accessible and used, we multiply the possibility of someone extracting the private key(s).
- Poses problems in network EFS encryption. Under normal circumstances, credential roaming does not work as expected, due to the nature of the logon that it supports (credential roaming: local logon, network shares: network logon). The specific limitation is described in KB907247 (in Credential roaming will not be used when using EFS to encrypt files on a file server). EFS (and EFS using credential roaming) has not been designed to work with network shares, but only for local encryption. Some workarounds exist, such as using Roaming profiles instead of credential roaming (KB837359), use Offline Files and local encryption of the cache, use of web folders (in Remote EFS Operations on File Shares and Web Folders).
Issuing certificates for iOS devices using Windows PKI’s SCEP implementation (NDES)
A successful request for a certificate from a mobile device always depends on its operating system. Currently, all mobile devices (notebooks, tablets etc.) that rely on the Windows operating system can request certificates using the well-known MMC or web enrollment ways. Moreover, non-domain-joined clients can also request certificates using the CEP/CES services of Windows 2008R2 and above CAs.
Windows RT tablets, based on version 8.1, can also request certificates as we have already mentioned the inclusion of a SCEP client in Windows 81. at a previous blog post. However, certificate issuance for devices that depend on other, mobile-only operating systems such as iOS and Android, depend on the vendor. In this blog post, we will limit our scope to iOS 5.x devices. These devices support the SCEP protocol, which allows for certificate requests directly from the mobile OS. Microsoft supports SCEP via the NDES service of the Certificate Services role.
For this reason, we need to install the NDES feature of Windows CAs. We will also create a specific service account which will run NDES. The service itself will be installed on the existing Enterprise Issuing CA. Moreover, we will need to:
- run the following command for IIS:
%systemroot%\system32\inetsrv\appcmd.exe set config /section:system.webServer/security/requestFiltering /requestLimits.maxQueryString:”3072″ /commit:apphost - install post-Windows 2008R2 hotfix KB2483564 that is needed for correct parsing of iOS HTTP SCEP requests.
- install, in a test machine, the software needed to create profiles for iOS to request certificates (iPhone configuration utility)
- test certificate issuance using an iPhone
This is how we request certificates for SCEP-compliant devices (in this example, iOS devices):
First, we visit the URL http://issuingca/CertSrv/MSCEP_Admin/ where we receive the password (challenge) needed to complete the certificate issuance
Retrieving the challenge string from the NDES server
After we receive the challenge string, we start the iOS configuration software, move to the configuration profiles section and create the profile needed for the certificate request. We finally select SCEP and fill in all the required values of the form. A sample request form has been captured in the following screenshot as a reference.
SCEP selection from the iPhone configuration utility
The completed form of the iPhone configuration utility
Everything PKI - YAPB (Yet Another PKI Blog) 