>> Soo... Given we prefer to stay conservative and not change SSSD crypto > > I didn't say that!
I know, I'm not saying that you took a decision on that but I was speaking in plural form as I recognize what you say in the sense that indeed there may be cases which we don't think of that we could break. >> backend fully (to be clear, I would have preferred it to follow >> upstream, not to provide a solution that will change in next LTS no >> matter what, and avoid having "frankensteins", but wasn't a strong >> requirement for me) I've been exploring ways to get only the component >> we care (p11_child) to use p11-kit and openssl. > > This is certainly a valuable angle to look at - thanks! > >> Robie, this would be better SRU approach? > > I think you misunderstand me. I'm not saying that your upload *has* to > be narrow. I've not formed an opinion that yet. What I'm saying is that > whatever size of scope you choose, there must be a regression analysis > that covers that scope. I understood this, reason why I thought that, given we have the chance to make it a narrower scope, then I tried to get that done. > But the analysis is still necessary and must not be skipped. Sure, not trying to do that, I'm just saying that I can't over all the cases myself. > I appreciate that sometimes it's harder or riskier to narrow the scope, > so I'm still open to widening the scope - *if* there is an appropriate > justification *and* full regression analysis of that wider scope > provided. Problem is that I'm quite sure we can't cover all the cases in a such complicated piece of software that may be configured in so many ways. Thus the reason I thought narrowing the scope was a better idea. -- You received this bug notification because you are a member of Ubuntu Touch seeded packages, which is subscribed to ca-certificates in Ubuntu. https://bugs.launchpad.net/bugs/1905790 Title: Make SSSD in 20.04 using OpenSSL and p11-kit (instead of NSS) for p11_child Status in ca-certificates package in Ubuntu: New Status in sssd package in Ubuntu: Fix Released Status in ca-certificates source package in Focal: New Status in sssd source package in Focal: New Bug description: [ Impact ] SSSD supports in 20.04 two security backends: NSS and OpenSSL (speaking in past tense as upstream dropped NSS support completely). Those two backends are used for various generic crypto features (so they are interchangeable), but also for the management of the PKCS#11 modules for smart cards. In this case, the main problem is that by using NSS it also relies on the presence of a "system NSS" database [1] that is something present in Fedora and RHEL, but not in ubuntu or generic Linux distributions. In order to make SSSD to find a smart card module, we would then need to create a such database that mentions a p11kit proxy that will eventually load the p11-kit module and then add the card CA certificate to the same DB (see more details in [2]). And even in such case... It will not work at login phase. This is making support for Smart-card based authentication in 20.04 quite complicated, and hard to implement in professional environments (see bug #1865226). As per this, recompiling SSSD's p11_child to use OpenSSL (as it already happens starting from 20.10) would be enough to make the this tool (the one in charge for smartcard authentications and certificate matching) to be able to get the smartcard devices from p11-kit allowed modules and to check their certificate using CA certificates in the ubuntu system ca certificate files (or other configured file). One more mayor reason to do this, is also that if we fix 20.04 now to use the "proper" method, people who will configure smartcard access there via SSSD (not easily possible right now) won't be affected by future migrations. [ Proposed Implementations ] 1) Use p11-kit and openssl for p11_child, by changing the build/test system (preferred) https://salsa.debian.org/3v1n0-guest/sssd/-/commits/p11-kit-p11_child 2) Build both versions and package things accordingly (hackish) https://salsa.debian.org/3v1n0-guest/sssd/-/commits/p11-kit-p11_child-v1 [ Test case ] With a smartcard reader available (and with a card in its slot) as reported by: $ p11-kit list-modules launch: $ sudo /usr/libexec/sssd/p11_child --pre -d 10 --debug-fd=2 \ --nssdb=/etc/ssl/certs/ca-certificates.crt The tool should find your card: (2020-11-26 21:34:22:020395): [p11_child[100729]] [do_card] (0x4000): Module List: (2020-11-26 21:34:22:020481): [p11_child[100729]] [do_card] (0x4000): common name: [p11-kit-trust]. (2020-11-26 21:34:22:020497): [p11_child[100729]] [do_card] (0x4000): dll name: [/usr/lib/x86_64-linux-gnu/pkcs11/p11-kit-trust.so]. (2020-11-26 21:34:22:020569): [p11_child[100729]] [do_card] (0x4000): Description [/etc/ssl/certs/ca-certificates.crt PKCS#11 Kit ] Manufacturer [PKCS#11 Kit ] flags [1] removable [false] token present [true]. (2020-11-26 21:34:22:020611): [p11_child[100729]] [do_card] (0x4000): common name: [opensc-pkcs11]. (2020-11-26 21:34:22:020646): [p11_child[100729]] [do_card] (0x4000): dll name: [/usr/lib/x86_64-linux-gnu/pkcs11/opensc-pkcs11.so]. (2020-11-26 21:34:22:025443): [p11_child[100729]] [do_card] (0x4000): Description [VMware Virtual USB CCID 00 00 VMware ] Manufacturer [VMware ] flags [7] removable [true] token present [true]. (2020-11-26 21:34:22:025725): [p11_child[100729]] [do_card] (0x4000): Found [MARCO TREVISAN (PIN CNS0)] in slot [VMware Virtual USB CCID 00 00][0] of module [1][/usr/lib/x86_64-linux-gnu/pkcs11/opensc-pkcs11.so]. Then the tool might fail if the card certificate is not added to the ca-certificates.crt, but this is outside the scope of the test case. What it matters is that the card is found. [ Regression potential ] While the change may involve quite different code paths when it comes to security features, I think we trust OpenSSL enough to be an acceptable crypto backend for PKCS#11 operations. And behavior should not change (if not improved), also assuming that upstream dropped NSS support completely in latest release, keeping the same functionalities. The only binary that is really affected in its behavior is p11_child. And I'm confident this will break only those setup (if there are any, given that smartcard access is currently not supported by ubuntu) that have been manually configured using an unsupported system NSS db. In the remote case there are such configurations, though, the fix will be as easy as adding the CA certificates to the new PAM cert DB (by default /etc/sssd/pki/sssd_auth_ca_db.pem), while the p11-kit modules will continue to work as before. It's also technically easy to do a postinst script that will just export all the certificates from the old nss db (/etc/pki/nssdb) into the new file, if we want to avoid any unlikely breakage. [1] https://github.com/SSSD/sssd/blob/sssd-2_3_1/src/responder/pam/pamsrv.c#L53 [2] https://hackmd.io/@3v1n0/ubuntu-smartcard-login#NSS-Database-to-be-deprecated-post-2004 To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/ca-certificates/+bug/1905790/+subscriptions -- Mailing list: https://launchpad.net/~touch-packages Post to : touch-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~touch-packages More help : https://help.launchpad.net/ListHelp
