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IIS SSL Certificate Renewal Pain


:P
On this page:

I’m in the middle of my annual certificate renewal for the West Wind site and I can honestly say that I hate IIS’s certificate system.  When it works it’s fine, but when it doesn’t man can it be a pain. Because I deal with public certificates on my site merely once a year, and you have to perform the certificate dance just the right way, I seem to run into some sort of trouble every year, thinking that Microsoft surely must have addressed the issues I ran into previously – HA! Not so.

Don’t ever use the Renew Certificate Feature in IIS!

The first rule that I should have never forgotten is that certificate renewals in IIS (7 is what I’m using but I think it’s no different in 7.5 and 8), simply don’t work if you’re submitting to get a public certificate from a certificate authority.

I use DNSimple for my DNS domain management and SSL certificates because they provide ridiculously easy domain management and good prices for SSL certs – especially wildcard certificates, which is what I use on west-wind.com.

Certificates in IIS can be found pegged to the machine root. If you go into the IIS Manager, go to the machine root the tree and then click on certificates and you then get various certificate options:

iiscert1

iiscert2

Both of these options create a new Certificate request (CSR), which is just a text file. But if you’re silly enough like me to click on the Renew button on your old certificate, you’ll find that you end up generating a very long Certificate Request that looks nothing like the original certificate request and the format that’s used for this is not accepted by most certificate authorities. While I’m not sure exactly what the problem is, it simply looks like IIS is respecting none of your original certificate bit size choices and is generating a huge certificate request that is 3 times the size of a ‘normal’ certificate request. The end result is (and I’ve done this at least twice now) is that the certificate processor is likely to fail processing those renewals.

Always create a new Certificate

While it’s a little more work and you have to remember how to fill out the certificate request properly, this is the safe way to make sure your certificate generates properly.

First comes the Distinguished Name Properties dialog:

NewCert

Ah yes you have to love the nomenclature of this stuff. Distinguished name, Common name – WTF is a common name? It doesn’t look common to me!

Make sure this form gets filled out correctly.

Common Name
This is the domain name of the Web site. In my case I’m creating a wildcard certificate so I’m using the * prefix. If you’re purchasing a certificate for a specific domain use www.west-wind.com or store.west-wind.com for example. Make sure this matches the EXACT domain you’re trying to use secure access on because that’s all the certificate is going to work on unless you get a wildcard certificate.

Organization

Is the name of your company or organization. Depending on the kind of certificate you purchase this name will show up on your certificate. Most low end SSL certificates (ie. those that cost under $100 for single domains) don’t list the organization, the higher signature certificates that also require extensive validation by the cert authority do. Regardless you should make sure this matches the right company/organization.

Organizational Unit

This can be anything. Not really sure what this is for, but traditionally I’ve always set this to Web because – well this is a Web thing after all right? I’ve never seen this used anywhere that I can tell other than to internally reference the cert.

State and Country
Pretty obvious. Should reflect the location of the business/organization/person or site.

Next you have to configure the bit size used for the certificate:

newCert2

The default on this dialog is 1024, but I’ve found that most providers these days request a minimum bit length of 2048, as did my DNSimple provider. Again check with the provider when you submit to make sure. Bit length mismatches can cause problems if you use a size that isn’t supported by the provider. I had that happen last year when I submitted my CSR and it got rejected quite a bit later, when the certs usually are issued within an hour or less.

When you’re done here, the certificate is saved to disk as a .txt file and it should look something like this (this is a 2048 bit length CSR):

-----BEGIN NEW CERTIFICATE REQUEST-----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AwQBAjALBglghkgBZQMEAQUwBwYFKw4DAgcwCgYIKoZIhvcNAwcwHQYDVR0OBBYE
FD/yOsTbXE+GVFCFMmldzQvyloz9MA0GCSqGSIb3DQEBBQUAA4IBAQCK6LlsCuIM
1AU0niB6QZ9v0FTsGFxP1dYvVUnJyY6VEKNiGFiQjZac7UCs0p58yScdXWEFOE8V
OsjAYD3xYNc05+ckyD67UHRGEUAVB9RBvbKW23KeR/8kBmEzc8PemD52YOgExxAJ
57xWmAwEHAvbgYzQvhO8AOzH3TGvvHbg5UKM1pYgNmuwZq5DkL/IDoeIJwfk/wrI
wghNTuxxIFgbH4YrgLgv4PRvrS/LaTCRBdboaCgzATMczaOb1nd/DVNR+3fCtMhM
W0psTAjzRbmXF3nJyAQa7jF/52gkY0RfFX2lG5tJnG+XDsVNvKNvh9Qa5Tlmkm06
ILKCm9ciWCKk
-----END NEW CERTIFICATE REQUEST-----

You can take that certificate request and submit that to your certificate provider. Since this is base64 encoded you can typically just paste it into a text box on the submission page, or some providers will ask you to upload the CSR as a file.

What does a Renewal look like?

Note the length of the CSR will vary somewhat with key strength, but compare this to a renewal request that IIS generated from my existing site:

-----BEGIN NEW CERTIFICATE REQUEST-----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lsfovKrx9mHPyrsiMIIFMAYJKwYBBAGCNw0BMYIFITCCBR0wggQFoAMCAQICEQDu
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GQYDVQQIExJHcmVhdGVyIE1hbmNoZXN0ZXIxEDAOBgNVBAcTB1NhbGZvcmQxGjAY
BgNVBAoTEUNPTU9ETyBDQSBMaW1pdGVkMRgwFgYDVQQDEw9Fc3NlbnRpYWxTU0wg
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dTqNHI9ri3ttewdEnT++TKGKKfTjX9SR8Waj
-----END NEW CERTIFICATE REQUEST-----

Clearly there’s something very different between this an my original request! And it didn’t work. IIS creates a custom CSR that is encoded in a format that no certificate authority I’ve ever used uses. If you want the gory details of what’s in there look at this ServerFault question (thanks to Mika in the comments). In the end it doesn’t matter  though – no certificate authority knows what to do with this CSR.

So create a new CSR and skip the renewal. Always!

Use the same Server

Keep in mind that on IIS at least you should always create your certificate on a single server and then when you receive the final certificate from your provider import it on that server. IIS tracks the CSR it created and requires it in order to import the final certificate properly. So if for some reason you try to install the certificate on another server, it won’t work. I’ve also run into trouble trying to install the same certificate twice – this time around I didn’t give my certificate the proper friendly name and IIS failed to allow me to assign the certificate to any of my Web sites. So I removed the certificate and tried to import again, only to find it failed the second time around. There are other ways to fix this, but in my case I had to have the certificate re-issued to work – not what you want to do.

Regardless of what you do though, when you import make sure you do it right the first time by crossing all your t’s and dotting your i's– it’ll save you a lot of grief!

You don’t actually have to use the server that the certificate gets installed on to generate the CSR and first install it, but it is generally a good idea to do so just so you can get the certificate installed into the right place right away. If you have access to the server where you need to install the certificate you might as well use it. But you can use another machine to generated the and install the certificate, then export the certificate and move it to another machine as needed. So you can use your Dev machine to create a certificate then export it and install it on a live server. More on installation and back up/export later.

Installing the Certificate

Once you’ve submitted a CSR request your provider will process the request and eventually issue you a new final certificate that contains another text file with the final key to import into your certificate store.

IIS does this by combining the content in your certificate request with the original CSR.

iiscertfinal

If all goes well your new certificate shows up in the certificate list and you’re ready to assign the certificate to your sites.

Make sure you use a friendly name that matches domain name of your site. So use *.mysite.com or www.mysite.com or store.mysite.com to ensure IIS recognizes the certificate.

I made the mistake of not naming my friendly name this way and found that IIS was unable to link my sites to my wildcard certificate. It needed to have the *. as part of the certificate otherwise the Hostname input field was blanked out.

Changing the Friendly Name

If you by accidentally used an invalid friendly name you can change it later in the Windows certificate store.

  • Bring up a Run Box
  • Type MMC
  • File | Add/Remove Snap In
  • Add Certificates | Computer Account | Local Computer
  • Drill into Certificates | Personal | Certificates
  • Find your Certificate | Right Click | Properties
  • Edit the Friendly Name | Click OK

Backing up your Certificate

The first thing you should do once your certificate is successfully installed is to back it up! In case your server crashes or you otherwise lose your configuration this will ensure you have an easy way to recover and reinstall your certificate either on the same server or a different one. If you’re running a server farm or using a wildcard certificate you also need to get the certificate onto other machines and a PFX file import is the easiest way to do this.

To back up your certificate select your certificate and choose Export from the context or sidebar menu:

CertExport2

The Export Certificate option allows you to export a password protected binary file that you can import in a single step. You can copy the resulting binary PFX file to back up or copy to other machines to install on.

Importing the certificate on another machine is as easy as pointing at the PFX file and specifying the password. IIS handles the rest.

Assigning a new certificate to your Site

Once you have the new certificate installed, all that’s left to do is assign it to your site.

In IIS select your Web site and bring up the Site Bindings from the right sidebar. Add a new binding for https, bind it to port 443, specify your hostname and pick the certificate from the pick list.

SiteBindings

If you’re using a root site make sure to set up your certificate for www.yoursite.com and also for yoursite.com so that both work properly with SSL.

Note that you need to explicitly configure each hostname for a certificate if you plan to use SSL.

Luckily if you update your SSL certificate in the following year, IIS prompts you and asks whether you like to update all other sites that are using the existing cert to the newer cert.

And you’re done.

So what’s the Pain?

So, all of this is old hat and it doesn’t look all that bad right? So what’s the pain here? Well if you follow the instructions and do everything right, then the process is about as straight forward as you would expect it to be. You create a cert request, you import it and assign it to your sites. That’s the basic steps and to be perfectly fair it works well – if nothing goes wrong.

However, renewing tends to be the problem. The first unintuitive issue is that you simply shouldn’t renew but create a new CSR and generate your new certificate from that. Over the years I’ve fallen prey to the belief that Microsoft eventually will fix this so that the renewal creates the same type of CSR as the old cert, but apparently that will just never happen. Booo!

The other problem I ran into is that I accidentally misnamed my imported certificate which in turn set off a chain of events that caused my originally issued certificate to become uninstallable. When I received my completed certificate I installed it and it installed just fine, but the friendly name was wrong. As a result IIS refused to assign the certificate to any of my host headered sites. That’s strike number one. Why the heck should the friendly name have any effect on the ability to attach the certificate???

Next I uninstalled the certificate because I figured that would be the easiest way to make sure I get it right. But I found that I could not reinstall my certificate. I kept getting these stop errors:

"ASN1 bad tag value met"

that would prevent the installation from completion. After searching around for this error and reading countless long messages on forums, I found that this error supposedly does not actually mean the install failed, but the list wouldn’t refresh. Commodo has this to say:

Note: There is a known issue in IIS 7 giving the following error: "Cannot find the certificate request associated with this certificate file. A certificate request must be completed on the computer where it was created." You may also receive a message stating "ASN1 bad tag value met". If this is the same server that you generated the CSR on then, in most cases, the certificate is actually installed. Simply cancel the dialog and press "F5" to refresh the list of server certificates. If the new certificate is now in the list, you can continue with the next step. If it is not in the list, you will need to reissue your certificate using a new CSR (see our CSR creation instructions for IIS 7). After creating a new CSR, login to your Comodo account and click the 'replace' button for your certificate.

Not sure if this issue is fixed in IIS 8 but that’s an insane bug to have crop up.

As it turns out, in my case the refresh didn’t work and the certificate didn’t show up in the IIS list after the reinstall. In fact when looking at the certificate store I could see my certificate was installed in the right place, but the private key is missing which is most likely why IIS is not picking it up. It looks like IIS could not match the final cert to the original CSR generated. But again some sort of message to that affect might be helpful instead of ASN1 bad tag value met.

Recovering the Private Key

So it turns out my original problem was that I received the published key, but when I imported the private key was missing. There’s a relatively easy way to recover from this.

If your certificate doesn’t show up in IIS check in the certificate store for the local machine (see steps above on how to bring this up). If you look at the certificate in Certificates/Personal/Certificates make sure you see the key as shown in the image below:

certiprivatekeyicon

if the key is missing it means that the certificate is missing the private key most likely.

To fix a certificate you can do the following:

  • Double click the certificate
  • Go to the Details Tab
  • Copy down the Serial number

Serialnumber

You can copy the serial number from the area blurred out above. The serial number will be in a format like ‎00 a7 9b a1 a4 9d 91 63 57 d6 9f 26 b8 ee 79 b5 cb and you’ll need to strip out the spaces in order to use it in the next step.

Next open up an Administrative command prompt and issue the following command:

certutil -repairstore my 00a79ba1a49d916357d69f26b8ee79b5cb

You should get a confirmation message that the repair worked. If you now go back to the certificate store you should now see the key icon show up on the certificate. Your certificate is fixed.

Now go back into IIS Manager and refresh the list of certificates and if all goes well you should see all the certificates that showed in the cert store now:

servercerts

Remember – back up the key first then map to your site…

Summary

I deal with a lot of customers who run their own IIS servers, and I can’t tell you how often I hear about botched SSL installations. When I posted some of my issues on Twitter yesterday I got a hell storm of “me too” responses. I’m clearly not the only one, who’s run into this especially with renewals. I feel pretty comfortable with IIS configuration and I do a lot of it for support purposes, but the SSL configuration is one that never seems to go seamlessly.

This blog post is meant as reminder to myself to read next time I do a renewal. So I can dot my i's and dash my t’s before I get caught in the mess I’m dealing with today. Hopefully some of you find this useful as well.

Posted in IIS7  Security  

The Voices of Reason


 

Lex Li
May 08, 2014

# re: IIS SSL Certificate Renewal Pain

I have seen too many similar cases, and I wonder if there is a better way than using IIS Manager. Jexus Manager has been my latest project, to bring the IIS style UI based management to a Linux based ASP.NET web server named Jexus, https://jexus.codeplex.com

For its 2.0 release, I plan to fully support IIS as well. You did provide information on how IIS Manager was used throughout the process (including the CSR), so I might spend some time analyzing if I can do something in Jexus Manager to resolve some of the pains for IIS users. :)

Rick Strahl
May 08, 2014

# re: IIS SSL Certificate Renewal Pain

@Lex - part of the problem is Windows and the crazy certificate management stuff it does. Heck the Windows certificate store makes it super hard to manage certificates through its ui - most simple things can't be done there and you have to fall back to command line tools that have constantly changed through the lifetime of each Windows versions. It's nuts. IIS's UI is actually pretty nice - but it's buggy and that's where the problems come in.

Have to check out your tool - sounds interesting.

Dan McQ
May 09, 2014

# re: IIS SSL Certificate Renewal Pain

Rick, what sort of monitoring strategy to you use for the expiring of your certs?

Rick Strahl
May 09, 2014

# re: IIS SSL Certificate Renewal Pain

@Dan - For my own sites I only rely on the nag emails from the issuer since I only deal with two certs. They'll nag loudly enough that it's hard to miss.

For more complex setups, I would use the DNS/Cert administration tools and make sure to check at least once a month :-) The trick is to have the certs and domains all in one place where you can see when things expire easily.

Grant G.
May 09, 2014

# re: IIS SSL Certificate Renewal Pain

Hey Rick,

Love your blog! You should probably check out just using certreq -new and create a PolicyFileIn (inf). This will save you a ton of time, because using that GUI is painful! Anytime I have to renew or reissue a cert I have a powershell script that creates the new CSR for me.

Mika Kukkonen
May 11, 2014

# re: IIS SSL Certificate Renewal Pain

IIS7 renewal request is explained here:
http://serverfault.com/questions/317086/how-can-i-verify-read-an-iis7-ssl-renewal-csr-with-openssl

Seems that this format was designed for better security, but still, after 6 years since Windows 2008 was released, I haven't seen a single certificate vendor that would support it. It also doesn't help that the IIS7/8 UI doesn't give any option to save the renewal request as a normal PKCS#10 CSR.

Windows 2003/IIS6 did use the PKCS#10 format and the renewal request was actually useful.

john G
May 14, 2014

# re: IIS SSL Certificate Renewal Pain

You might want to think about avoiding the use of wildcard cents. Use Subject Alternate Names instead. If the key pair for a wildcard cert is ever compromised a rouge can set themselves up as a trusted agent on your network undetected. Also, if the key pair is compromised on one server, then all severs using the key pair are also compromised. Using a unique key pair for each server does add to the operations side of the equation; however, consider using KMIP to assist with management. If your a larger shop, think about using tools such as Venafi.

Mike
June 09, 2014

# re: IIS SSL Certificate Renewal Pain

So what does a person do when they have 200+ certificates to manage? Having to manually re-enter everything every time is crazy. I can't imagine organizations larger than mine, that are running IIS and have thousands of certificates to manage, do it this way.

In IIS6 it would at least auto-fill the information for my company (which is the same for all certificates), and only change the CN/SANs. As things are now, I keep an old IIS6 server running just so I can generate certificates at something (slightly less than a snails pace. I just set up a dummy site and use it for nothing but generating certificates.

Rick Strahl
June 09, 2014

# re: IIS SSL Certificate Renewal Pain

@Mike - I think you can automate some of this with command line tooling if you have that many certs to deal with. It's overkill for the once or twice a year renewals I do, but for more complex scenarios yes that's definitely an issue.

It's lame that this is so hard - this is for the most part a UI issue that is probably trivial to fix properly with a few extra options on the renewal dialog but as so many admin things in the Microosoft world the UI is almost always an after thought after lulling you into thinking that this would be easy with a GUI :-)

ShaneF
December 09, 2014

# re: IIS SSL Certificate Renewal Pain

Holy cow you were a life saver here! I'm in the same boat. I only deal with client cert issues once every year or so. This was a life saver! Especially adding the portion on how to link the new cert with the website. Thank you!

Bart Verkoeijen
June 02, 2015

# re: IIS SSL Certificate Renewal Pain

Thanks a ton, Rick! The private key wouldn't show up after importing the CA response. I think it was because I created two CSRs for the same friendly name. This was necessary because we requested two different certificate types (regular and extended validation). The restore command worked perfectly.

Lex Li
September 06, 2015

# re: IIS SSL Certificate Renewal Pain

Have been a year and more, but finally Jexus Manager (for IIS Express) is now capable of handling basic certificate tasks, https://jexus.codeplex.com/releases/view/138373. Advantages over Microsoft's IIS Manager in this area are, 1) non-admin can run it to view Server Certificates in read-only mode, 2) non-admin can perform changes following elevation prompt, 3) renewing a certificate is just like requesting a new one, 4) can generate self-signed certificate with custom CN. Limitations right now are, 1) bit length is not yet honored, 2) no prompt before removing a certificate and netsh http bindings are not validated. This tool is still in Beta phase, and the above issues are expected to be fixed pretty soon.

Paul Litwin
October 30, 2015

# re: IIS SSL Certificate Renewal Pain

Thanks, Rick. Everytime I do this I forget all this. Your post made it very easy and of course I know I can trust you because I know that you really know you stuff.

William
June 13, 2017

# re: IIS SSL Certificate Renewal Pain

Thank you for the tip on the certutil, that was exactly what I needed to do to get my key fixed.


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