3 ms·

> Lastly, with asking consumers to install a CA certificate, I ask for a significantly more powerful permission than if I could just have them trust my certific

by est31 6y ago

> Lastly, with asking consumers to install a CA certificate, I ask for a significantly more powerful permission than if I could just have them trust my certificate. CA certificates can be constrained. https://tools.ietf.org/html/rfc5280#section-4.2.1.10 https://tools.ietf.org/html/rfc5280#section-4.2.1.10

toast0 6y ago
Are common certificate validation libraries honoring these constraints? When I tried to use this many moons ago, most things ignored the constraints; although I could mark the extension critical, and then some (but not all, yay) of the things that didn't understand would refuse the CA.
- namibj 6y ago
  Can you name and shame those that ignored the critical extension? Sounds CVE-worthy. A date to guess the versions you used would also help.
  - toast0 6y ago
    No, it was on the order of 5 years ago; everybody was garbage back then. But, if this had become usable, I would expect to have seen articles about using it since then.
- est31 6y ago
  IDK NSS seems to have code to verify it: https://searchfox.org/mozilla-central/source/security/nss/lib/mozpkix/lib/pkixnames.cpp#285 https://searchfox.org/mozilla-central/source/security/nss/li... As does webpki: https://github.com/briansmith/webpki/blob/482627c40dad2148da8b9bf64c2c781ea30a7e4d/src/name.rs#L158 https://github.com/briansmith/webpki/blob/482627c40dad2148da... But haven't tested it (or checked other libraries).
  - est31 6y ago
    Update: tested it with openssl and webpki. both claim to have support but it only works with openssl. For webpki I had to file two bugs: https://github.com/briansmith/webpki/issues/134 https://github.com/briansmith/webpki/issues/134 https://github.com/briansmith/webpki/issues/135 https://github.com/briansmith/webpki/issues/135
loeg 6y ago
How do you actually generate a constrained CA certificate? I have tried to do this for a long time but openssl is inscrutable.
- est31 6y ago
  There seems to be a guide for openssl here [0] but it seems kinda complicated. This discussion inspired me to add name constraints support to rcgen [2]. If you aren't afraid to write Rust, you should give using it a try. [0] https://www.marcanoonline.com/post/2016/09/restrict-certificate-authority-to-a-domain/ https://www.marcanoonline.com/post/2016/09/restrict-certific... [1] https://tools.ietf.org/html/rfc5280#page-41 https://tools.ietf.org/html/rfc5280#page-41 [2] https://github.com/est31/rcgen/commit/059cc19fcd1b8bb57feed5524dce8dd7f47d53db https://github.com/est31/rcgen/commit/059cc19fcd1b8bb57feed5...
  - loeg 6y ago
    Thanks!

by est31 6y ago

toast0 6y ago

Are common certificate validation libraries honoring these constraints? When I tried to use this many moons ago, most things ignored the constraints; although I could mark the extension critical, and then some (but not all, yay) of the things that didn't understand would refuse the CA.

namibj 6y ago
Can you name and shame those that ignored the critical extension? Sounds CVE-worthy. A date to guess the versions you used would also help.
- toast0 6y ago
  No, it was on the order of 5 years ago; everybody was garbage back then. But, if this had become usable, I would expect to have seen articles about using it since then.
est31 6y ago
IDK NSS seems to have code to verify it: https://searchfox.org/mozilla-central/source/security/nss/lib/mozpkix/lib/pkixnames.cpp#285 https://searchfox.org/mozilla-central/source/security/nss/li... As does webpki: https://github.com/briansmith/webpki/blob/482627c40dad2148da8b9bf64c2c781ea30a7e4d/src/name.rs#L158 https://github.com/briansmith/webpki/blob/482627c40dad2148da... But haven't tested it (or checked other libraries).
- est31 6y ago
  Update: tested it with openssl and webpki. both claim to have support but it only works with openssl. For webpki I had to file two bugs: https://github.com/briansmith/webpki/issues/134 https://github.com/briansmith/webpki/issues/134 https://github.com/briansmith/webpki/issues/135 https://github.com/briansmith/webpki/issues/135

loeg 6y ago

How do you actually generate a constrained CA certificate? I have tried to do this for a long time but openssl is inscrutable.

est31 6y ago
There seems to be a guide for openssl here [0] but it seems kinda complicated. This discussion inspired me to add name constraints support to rcgen [2]. If you aren't afraid to write Rust, you should give using it a try. [0] https://www.marcanoonline.com/post/2016/09/restrict-certificate-authority-to-a-domain/ https://www.marcanoonline.com/post/2016/09/restrict-certific... [1] https://tools.ietf.org/html/rfc5280#page-41 https://tools.ietf.org/html/rfc5280#page-41 [2] https://github.com/est31/rcgen/commit/059cc19fcd1b8bb57feed5524dce8dd7f47d53db https://github.com/est31/rcgen/commit/059cc19fcd1b8bb57feed5...
- loeg 6y ago
  Thanks!