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Could you elaborate on why wildcard certs are a bad idea? I've heard this from several sources, but I haven't read a breakdown of why people think this. If I'm

by nrook 10y ago

Could you elaborate on why wildcard certs are a bad idea? I've heard this from several sources, but I haven't read a breakdown of why people think this. If I'm running a web application, and want to provide an interface where separate teams sign up and access their version of the app at team-name.your-app.com, what's the alternative? Or is it that this is considered unwise, and I should just put team-name in the URL path instead?

zeta0134 10y ago
The primary issue with wildcard certificates is that it encourages certificate reuse between server environments. Even the act of transferring keys around carries a certain degree of risk. With a wildcard certificate though, say you have a very secure shopping site, and a user run forum: - https://checkout.example.com/ - https://forums.example.com/ Your wildcard certificate for * .example.com covers both domains, and can be shared between both servers. Nice! You've saved a bundle of money on certificates. But there's now a security risk: Say an attacker manages to compromise forums.example.com through some vulnerability in the forum software, and steals the private key for * .example.com. They can now set up their own server hosting checkout.example.com, successfully execute a Man in the Middle attack, and steal sensitive customer data without the end user being any the wiser. Issuing separate certificates prevents this scenario by enforcing a separation of responsibilities. If each server has its own set of keys, then a security compromise on forums.example.com does not spill over to checkout.example.com, because the key used on one server is useless to impersonate the other. Obviously a key compromise at all is a bad situation, but you want to architecture your environment so that a compromise has the least potential to do damage, and that's the basic argument against wildcard certificates.
- sk5t 10y ago
  Good writeup. In addition, using discrete certificates makes managing them easier, whether for renewal, squashing SHA-1 and the like, or revocation. It can be a big headache to track down all the places a wildcard cert worms its way into at large, penny-pinching orgs.
sk5t 10y ago
FYI, it is possible to run multiple certificates on one IP+port if your SSL clients support SNI. Nowadays that's not too crazy an assumption, and creating on-demand certs is doable; integrating this with your service and managing renewal might be a pretty advanced task though. In other words, a web app with custom subdomains is probably a reasonable use case for wildcart certs, for now.

by nrook 10y ago

zeta0134 10y ago

The primary issue with wildcard certificates is that it encourages certificate reuse between server environments. Even the act of transferring keys around carries a certain degree of risk. With a wildcard certificate though, say you have a very secure shopping site, and a user run forum: - https://checkout.example.com/ - https://forums.example.com/ Your wildcard certificate for * .example.com covers both domains, and can be shared between both servers. Nice! You've saved a bundle of money on certificates. But there's now a security risk: Say an attacker manages to compromise forums.example.com through some vulnerability in the forum software, and steals the private key for * .example.com. They can now set up their own server hosting checkout.example.com, successfully execute a Man in the Middle attack, and steal sensitive customer data without the end user being any the wiser. Issuing separate certificates prevents this scenario by enforcing a separation of responsibilities. If each server has its own set of keys, then a security compromise on forums.example.com does not spill over to checkout.example.com, because the key used on one server is useless to impersonate the other. Obviously a key compromise at all is a bad situation, but you want to architecture your environment so that a compromise has the least potential to do damage, and that's the basic argument against wildcard certificates.

sk5t 10y ago
Good writeup. In addition, using discrete certificates makes managing them easier, whether for renewal, squashing SHA-1 and the like, or revocation. It can be a big headache to track down all the places a wildcard cert worms its way into at large, penny-pinching orgs.

sk5t 10y ago

FYI, it is possible to run multiple certificates on one IP+port if your SSL clients support SNI. Nowadays that's not too crazy an assumption, and creating on-demand certs is doable; integrating this with your service and managing renewal might be a pretty advanced task though. In other words, a web app with custom subdomains is probably a reasonable use case for wildcart certs, for now.