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193

It is already done: It is the FPKI root CA, under explicit and full control of the US government. Windows already trusts it by default. Before you flip out and begin to delete root CA certificates, burn your computer's motherboard, or drink a gallon of vodka, think about what it means. It means that the US government could technically emit a fake ...


144

Serious certification authorities use heavy procedures. At the core, the CA key will be stored in a Hardware Security Module; but that's only part of the thing. The CA itself must be physically protected, which includes proactive and retrospective measures. Proactive measures are about preventing attacks from succeeding. For instance, the CA will be stored ...


75

When a certificate is expired, its revocation status is no longer published. That is, the certificate might have been revoked long ago, but it will no longer be included in the CRL. Certificate expiration date is the cut-off date for CRL inclusion. That's the official reason why certificates expire: to keep CRL size bounded. (The unofficial reason is to ...


64

It sounds like your issue is that this vulnerability is bigger than you know what to do with. The rules of responsible disclosure, as decribed here, say that you should contact the vendor and negotiate a period of time - between 1 week and 6 months, depending on the depth of the changes required - in which they can implement a patch, revoke and re-issue ...


61

A good question. The simplest answer is that having an expiration date ensures that you have an "audit" every so often. If there were no expiration date, and someone stopped using a certificate (and protecting the private key), no one would ever know. However, by having an expiration date you ensure that the user goes back to the company that sold them the ...


59

For the purposes of this discussion there are only a couple differences between web signing certificates: Extended vs standard validation (green bar). Number of bits in a certificate request (1024/2048/4096). Certificate chain. It is easier to set up certificates with a shorter trust chain but there are inexpensive certs out there with a direct or ...


59

In essence, these certificates are necessary and required for backward compatibility with XP and Server 2003. If anything was signed with these certificates, even if they're expired now, your server needs the cert trusted in order to trust the thing that the cert signed. Source: http://support.microsoft.com/kb/293781 Some certificates that are listed in ...


51

Disclaimer: This answer comes directly from the eHow article. No infringement intended. Domain Validation SSL Certificates Domain validated SSL certificates are used to establish a baseline level of trust with a website and prove that you are visiting the website you think you are visiting. These certificates are issued after the SSL issuer confirms ...


43

You are right assuming the certificate is useless without the private key, so sending it in the mail is no big security risk and is common practice actually. The certificate is supposed to be public, connecting to your website would also provide me with your certificate, so no need to hack your email there. edit When starting the connection the server ...


42

Update 5 The root problem (heh) with the CA model is that in general practice, any CA can issue certs for any domain, so you're vulnerable to the weakest link. As to who you can trust, I doubt that the list is very long at all, since the stakes are high and security is hard. I recommend Christopher Soghoian's post on the subject, which clarifies the ...


34

It is ultimately the responsibility of the client's user to check the validity of the certificate. As a service provider, apart from educating the user if you can, there is not much you can do on your side: you don't control which certificates are trusted by the user's browser and you can't know whether the users have verified they using SSL/TLS properly and ...


34

I like using StartCom for a free certificate. It's recognized in most major browsers and is better than using a self-signed certificate (No error prompts for users).


34

The NSA could and probably already has gone -- using a USA PATRIOT Act demand letter, or other similar legislative tool -- to all the major CAs in the United States (e.g. VeriSign, GeoTrust, etc.) and demanded that they remit their private root keys to "No Such Agency", "for purposes of 'national security'". Of course, all such requests must (per PATRIOT ...


33

Such a claim is generally quite serious. While reaching out to the vendor in question is a responsible matter, you should certainly consider notifying the relevant root store security teams, since they are responsible for designing, evaluating, and applying the security controls to prevent this, and will likely need to directly work with the CA to ascertain ...


32

The purpose of the warning is that by using HTTPS, there is an expectation of proper security, but a self-signed or expired certificate has vulnerabilities that the user needs to be aware of. The "risk" is that one thinks they are properly secured, but they are not fully secured, as opposed to HTTP, where one knows there is no encryption at all. There ...


31

Note: This is a (very very long) compendium of various recommendations and actions that Microsoft, NIST, and other well respected PKI and cryptography experts have said. If you see something that requires even the slightest revision, do let me know. Before I get into configuring the CA and its subs, it's good to know that even though MSFT's CryptoAPI ...


31

Update: It seems like a Finnish man was able to demonstrate this "attack" by issuing a certificate for the domain live.fi by having the address hostmaster@live.fi. Last year, I made a bet with a friend that I can get a browser-trusted certificate with his domain name in order to launch a successful MiTM attack on his login form to steal his password. Long ...


29

At the byte level, X.509 is X.509 and there is no reason why the free SSL certificates would be any better or worse than the non-free -- the price is not written in the certificate. Any certificate provider can fumble the certificate generation, regardless of whether he gets paid for it or not. The hard part of a certificate is outside of it: it is in the ...


29

Yes, what you are getting in the zip file is exactly what every visitor to your site would get every time they start a TLS session - the public keys with certifying information. The private key is the only thing that should be kept hidden from unauthorized access.


28

On the physical side they first keep the root CA completely offline. Typically what happens is that they set up the root CA, make subordinates, then take the root CA completely offline and take the hard drives and HSMs (sometimes even the whole server) and essentially lock them in a safe. Next, they segment the network to keep those subordinate/issuing ...


27

Mostly yes, any CA in your trusted root, (or subordinates) can issue a cert for any DNS name. Name constraints and Enhanced Key Usage can be used to mitigate this, but they aren't enforced everywhere. DANE, Certificate Pinning, and Certificate transparency are a few projects that help protect from this risk.


26

As Matt Blaze once wrote, CAs protect you from anyone who they are unwilling to take money from. That should tell you something about where the CA's incentives lie, and some potential risks in the arrangement.


25

Solved. The problem was indeed triggered by installing Apple Mavericks/ML Security Update 2015-004. As mentioned in this Apple release note, it included updates to the certificate trust policy. There was a duplicate certificate installed (with a wrong serial no.), removing it fixed the problem. The serial number for the cert as published by Apple matched ...


24

The fingerprint, as displayed in the Fingerprints section when looking at a certificate with Firefox or the thumbprint in IE is the hash of the entire certificate in DER form. If your certificate is in PEM format, convert it to DER with OpenSSL: openssl x509 -in cert.crt -outform DER -out cert.cer Then, perform a SHA-1 hash on it (e.g. with sha1sum1): ...


24

You can add, for example the -sha256 flag to the OpenSSL command line when generating the CSR. I don't believe any CA will change how they sign your CSR based on this, and it certainly won't affect the certificate chain. They're not resigning the cert chain for each key, the only signature operation they do is on your CSR itself. Any intermediate/root CAs ...


23

On a theoretical basis, an expired certificate is a certificate which must not be used any longer. This is made explicit in the the Internet X.509 Profile in the certificate validation algorithm (section 6.1.3, item a.2). In practice, this has two consequences: The key owner (the server) must keep its private key, well, private. Anybody who gets a copy of ...


23

Certificates are signed and the cryptographic signature is verified; if the signature matches then the certificate contents are exactly as they were when the certificate was signed. This, of course, does not solve the problem, it merely moves it around. The complete structure is called a PKI. The certificates which are preinstalled in your computer (came ...


23

Congratulations! Sounds like a major find. First, generate some proof. The github.com SSL certificate sounds like a great start. Make sure you keep all the network traces you need to show exactly what happened. You need to determine if you broke any laws or T&Cs while doing this. If the CA does not have a bug bounty, you almost certainly did. In that ...


22

"Alternatives" depend on whether you want something which may work in the future, or something which works right now, with existing browsers. Right now, Web browsers expect that servers send X.509 certificates, and then they validate them against the set of root CA integrated in the browser (or operating system). This means that if you want something that ...



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