3 ms·

Not necessarily, there are plenty of applications that use their own trusted root CAs and thus technically the app is validating it. Most popular example being

by dastx 7y ago

Not necessarily, there are plenty of applications that use their own trusted root CAs and thus technically the app is validating it. Most popular example being Firefox. Often libraries have options to specify trusted root CAs as well as options to disable validation per host and/or globally. I've never come across any library that would have any of these options enabled by default. With that said, apps like banks should still not be putting trust into the OS or anything else. Certificate pinning is a good and should be utilised, especially for sensitive systems such as banks' apps.

tialaramex 7y ago
Historically it was very common to default disable or entirely omit essential checks. CWE-297 https://cwe.mitre.org/data/definitions/297.html https://cwe.mitre.org/data/definitions/297.html is about this common mistake. The happy path is invariably well tested and doesn't show this, unhappy paths often use garbage self-signed certs which fail non-host based checks and so those behave as expected too. Testing usually misses the host mismatch check. OpenSSL for years only provided some fairly hairy code if you actually wanted to do dnsName matching, which you absolutely should do. What that means is, lots of software was written (say, 10+ years ago) in which OpenSSL is checking that your peer has a "real" certificate but it doesn't care which one. A certificate for we-are.literally-thieves.example ? Cool, that's issued by a trusted CA and so it's fine. Oh you thought you were connecting to my-real-bank.example? You didn't ask me to check the name on the certificate and I don't bother providing a sensible API to do so anyway. Here's their actual documentation: > Versions prior to 1.0.2 did not perform hostname validation. Version 1.0.2 and up contain support for hostname validation, but they still require the user to call a few functions to set it up. Modern (1.1 onward) releases of OpenSSL provide a sane API which checks names you give it, so if you tell OpenSSL to connect to my-real-bank.example it realises you don't think certificates for other names are OK. But the old ones didn't do that and the ones 10+ years ago expected you to grok PKIX (the Internet's agreed way of coercing the X.509 standard intended for the X.500 series Directory into a way to certify things on the Internet) or else give up.

by dastx 7y ago

tialaramex 7y ago

Historically it was very common to default disable or entirely omit essential checks. CWE-297 https://cwe.mitre.org/data/definitions/297.html https://cwe.mitre.org/data/definitions/297.html is about this common mistake. The happy path is invariably well tested and doesn't show this, unhappy paths often use garbage self-signed certs which fail non-host based checks and so those behave as expected too. Testing usually misses the host mismatch check. OpenSSL for years only provided some fairly hairy code if you actually wanted to do dnsName matching, which you absolutely should do. What that means is, lots of software was written (say, 10+ years ago) in which OpenSSL is checking that your peer has a "real" certificate but it doesn't care which one. A certificate for we-are.literally-thieves.example ? Cool, that's issued by a trusted CA and so it's fine. Oh you thought you were connecting to my-real-bank.example? You didn't ask me to check the name on the certificate and I don't bother providing a sensible API to do so anyway. Here's their actual documentation: > Versions prior to 1.0.2 did not perform hostname validation. Version 1.0.2 and up contain support for hostname validation, but they still require the user to call a few functions to set it up. Modern (1.1 onward) releases of OpenSSL provide a sane API which checks names you give it, so if you tell OpenSSL to connect to my-real-bank.example it realises you don't think certificates for other names are OK. But the old ones didn't do that and the ones 10+ years ago expected you to grok PKIX (the Internet's agreed way of coercing the X.509 standard intended for the X.500 series Directory into a way to certify things on the Internet) or else give up.