{"id":7425,"date":"2018-09-18T14:59:15","date_gmt":"2018-09-18T18:59:15","guid":{"rendered":"https:\/\/www.thesslstore.com\/blog\/?p=7425"},"modified":"2023-03-31T12:29:57","modified_gmt":"2023-03-31T16:29:57","slug":"what-is-a-rogue-certificate","status":"publish","type":"post","link":"https:\/\/www.thesslstore.com\/blog\/what-is-a-rogue-certificate\/","title":{"rendered":"What is a Rogue Certificate? How do you prevent them?"},"content":{"rendered":"

A rogue certificate can wreak havoc on your company \u2013 here\u2019s how to prevent that.<\/h2>\n

\"whatOne of the most frequent questions we get asked is, \u201cwhat is a rogue certificate?\u201d And unfortunately, the answer isn\u2019t quite as exciting as the name connotes. Still, rogue certificates represent a major threat to Enterprise businesses. Really, any business \u2013 it\u2019s just that Enterprises have the most surface to cover, which means they\u2019re easier to miss.<\/p>\n

To answer the question \u201cwhat is a rogue certificate?\u201d we\u2019re going to have to start with a little bit of background, discuss what it means when a Certificate Authority (CA) goes rogue and we\u2019ll end our discussion with some tips on preventing rogue certificates from affecting your business.<\/p>\n

So, what is a rogue a certificate? Let\u2019s hash it out.<\/span><\/p>\n

What your digital certificate is really authenticating<\/h2>\n

Let\u2019s start by talking about the authentication aspect of Public Key Infrastructure \u2013 specifically in an SSL\/TLS context. When a digital certificate is issued, you send the Certificate Authority your public key and a Certificate Signing Request, complete with all relevant information. The CA validates it and returns a signed digital certificate that contains the validated information.<\/p>\n

\"whatNow, there are higher levels of validation, which authenticate businesses (Organization Validation and Extended Validation), we\u2019re going to ignore those in this discussion and focus on the one authentication that all SSL\/TLS certificates provide: server authentication.<\/p>\n

When the CA performs domain validation it\u2019s attempting to verify that the certificate request came from the domain\u2019s legitimate owner.<\/p>\n

There are a few ways to do this, the CA\/Browser Forum (which determines the baseline requirements that government certificate issuance) actually just strengthened the checks that are made<\/a>.<\/p>\n

But the idea is always the same, the CA needs to verify that you are indeed the owner of the domain that is living on that server.<\/p>\n

Once it\u2019s done this, the CA issues the certificate. This is how it\u2019s supposed to work.<\/p>\n<\/span><\/span>\n

So, what is a rogue certificate?<\/h2>\n

A rogue certificate is a legitimate, trusted certificate that has been issued by a trusted certificate authority but is either compromised<\/a> or was issued to the wrong party. There are a few ways this can happen \u2013 we will get to those in a moment.<\/p>\n

\"whatWe\u2019re not going to go in-depth in discussing the trust model (here\u2019s a full description<\/a>), but let\u2019s at least cover the basic concepts. When a CA issues a certificate, it signs that certificate with one of its private keys<\/a>. This private key was either signed by a trusted root, or was signed by an intermediate root that was signed by the trusted root. Either way, when a browser receives a trusted SSL certificate, it follows the digital signature back to the certificate it\u2019s associated with until it eventually reaches one of the trusted roots in its trust store.<\/p>\n

As long as the certificate\u2019s signature can be chained back to a root the certificate is trusted. A rogue certificate is a trusted certificate that is associated with a site that the certificate\u2019s owner doesn\u2019t actually control.<\/p>\n

Eric Vandenburg, the VP of TCDI (Technology Concepts & Design, Inc.) paints a pretty clear picture of why this is dangerous<\/a>:<\/p>\n

Rogue certificates allow attackers to create illegitimate sites that are indistinguishable from real sites like eBay, Google or PNC because their certificate hierarchy can be validated.\u00a0 Users then will be redirected to such sites through phishing or \u201dman in the middle\u201d attacks where a compromised host in-between the user and a legitimate site sends traffic to an illegitimate site instead.<\/p><\/blockquote>\n

We cover on a regular basis how convincing phishing websites are<\/a>. How prevalent they are<\/a>. How dangerous they are<\/a>. And up until recently, Google\u2019s HTTPS indicator \u2013 which placed a \u201cSecure\u201d badge beside the URL in the address bar<\/a> \u2013 was only making things worse<\/a>.<\/p>\n

But even with all those factors tipping the scales in phishing\u2019s favor, a discerning eye could still spot a fake<\/a>.<\/p>\n

Not with a rogue certificate. A rogue certificate will trick users\u2019 web browsers into trusting the website despite it being a fake.<\/p>\n<\/span>\n

How can a rogue certificate trick a user\u2019s browser?<\/h2>\n

Let\u2019s talk about the way that certificate-based authentication actually works. This isn\u2019t the validation that takes place during issuance, this is the check that a browser does when presented with a certificate upon arrival at a website.<\/p>\n

The checks are:<\/p>\n

    \n
  1. Was the certificate signed by a trusted CA? Does the digital signature chain back to one of the roots in the trust store?<\/li>\n
  2. Is this certificate still valid? When was it issued? When does it expire<\/a>? Are we still in that time frame?<\/li>\n
  3. Has the certificate been revoked? This requires an OCSP<\/a> or CRL<\/a> check.<\/li>\n
  4. Does the key pair match? Is the server in possession of the associated private key?<\/li>\n<\/ol>\n

    Step 4 is sometimes referred to as proof of possession. And I say steps, that\u2019s just for reference \u2013 let\u2019s not get too hung up on the terminology<\/em>. The browser will encrypt<\/a> some piece of throwaway data with the certificate\u2019s public key. Now, the public key is actually derived from the private key, which is why only that private key can decrypt that public key. This is what prevents spoof websites from just copying a legitimate site\u2019s SSL certificate and trying to present its public key as its own. That certificate’s public key wouldn\u2019t work because the server presenting the certificate doesn\u2019t have the private key.<\/p>\n

    \"whatOk, so now let\u2019s mix in a rogue certificate.<\/p>\n

    Remember, a rogue certificate is a valid certificate that has come into the possession of a third-party \u2013 typically a malicious one. That means that the attacker actually has the private key.<\/p>\n

    So when you arrive at a malicious website with a rogue certificate, your browser performs those four checks. It makes sure the certificate was signed by a trusted CA. It was. It makes sure the certificate is valid. It is. It checks if the certificate was revoked. It isn\u2019t.<\/p>\n

    Now it\u2019s going to check proof of possession.<\/p>\n

    It uses the public key associated with certificate to encrypt some data and the attacker, which has the associated private key, decrypts and returns it. As far as your computer system is concerned, this website is who it says it is.<\/p>\n

    A user\u2019s computer never actually authenticates the server itself, it just authenticates the certificate. It\u2019s kind of like when you present a police officer with your driver\u2019s license. He\u2019s going to make sure that the picture on the license matches, that the license is valid, that it hasn\u2019t expired and he\u2019s going to call into the DMV to make sure it hasn\u2019t been revoked. If those all check out, he\u2019s going to accept the license as legitimate. He\u2019s not actually going to check your DNA and blood type to make sure it\u2019s you on a biological level, he\u2019s going off the documentation.<\/p>\n

    PKI works<\/a> the same way. A rogue certificate isn\u2019t all that different from a forged passport or a faked identity in a spy film. It allows an attacker to operate under a false identity.<\/p>\n

    How do rogue certificates get issued?<\/h2>\n

    \"whatHere is the million dollar question, how do rogue certificates happen? Well, there are three primary sources of rogue certificates:<\/p>\n