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When connecting to the Wi-Fi of my university, which authenticates clients via “EAP-PEAP (MSCHAPv2)”, I got the following prompt:

Example Server Certificate

I had no choice but to trust this certificate, because otherwise I won’t have Internet access in the school library. However, out of fear, I unchecked the Always trust “Example Server Certificate” option before clicking Continue.

Is there a security vulnerability in my university’s Wi-Fi authentication system? I suppose even another one creates a certificate with the name “Example Server Certificate”, the digital signature would be different, so I’m probably safe, but trusting a certificate with such a weird name still makes me sweat.

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    They didn't create their own certificate but used the default. It's possible this certificate is the same as every other system by the equipment vendor. So, yes, a risk.
    – schroeder
    Dec 1, 2017 at 12:00
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    Note that if it is an individually created certificate (not some default where the private key is publicly known) it is more secure to check the Always trust “Example Server Certificate” option, because then you will be notified if the certificate changes.
    – Josef
    Dec 1, 2017 at 14:21
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    I'm seeing this late, but while a default certificate it isn't the same as any other system, contrary to what @schroeder fears. freeradius - which your university is using - provides a script to create a basic CA for testing. Obviously it's still bad as it should be used for testing only, but it could have been worse.
    – Nico
    Feb 27, 2018 at 8:28

1 Answer 1

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Is there a security vulnerability in my university’s Wi-Fi authentication system?

There are multiple problems:

  • It looks like they just assumed that the users will just accept any certificate. The correct way is to either use a certificate with a useful subject which was signed by an already trusted CA or teach users how to distinguish a valid certificate from a fake (like checking the fingerprint).
  • As @schroeder has already pointed out: this looks like the default certificate which might also be used in other installations and where the private key is probably known.

Because of this it will be easy for some attacker to create its own access point which looks the same and mount a man in the middle attack to sniff and modify any connections which are not encrypted (i.e. HTTPS is usually fine, plain HTTP is not).

Of course, it might also be that the university did everything correctly but that you are connected to an access point created by some attacker who hoped for gullible users.

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  • In my case, clients are also required to supply a student ID and password during authentication, and it’s quite common to let the client device to remember the credential. Then would the credentials be provided to the fake APs set up by an attacker?
    – nalzok
    Dec 1, 2017 at 12:31
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    @SunQingyao: yes, in this case the credentials would be sent to the fake AP. But since MS-CHAPv2 is used the attacker will probably not get easily to the password (can still break it). Dec 1, 2017 at 12:54

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