On 9/14/2018 1:05 PM, Kees Cook wrote: > On Fri, Sep 14, 2018 at 8:57 AM, Casey Schaufler <casey@xxxxxxxxxxxxxxxx> wrote: >> On 9/13/2018 5:19 PM, Kees Cook wrote: >>> We already have the minor LSMs that cannot change order. >> Are you saying that we don't have a mechanism to change >> the order, or that they wouldn't work right in a different >> order? Well, there's the capability module that has to be >> first. > I just meant their order is explicit in security.c. > >>> They aren't >>> part of security= parsing either. >> True, but there's no reason now that we couldn't change that. >> Except for capability. Hmm. > Right, we have at least one that MUST be first (and must not be disabled). > >>> Should "blob-sharing" LSMs be like major LSMs or minor LSMs? >> I like the idea of changing the minor modules to do the full >> registration process. That would make them all the same. >> Except for capability. In any case, the "blob-sharing" LSMs >> need to do the full registration process to account for their >> blobs sizes, and that brings the "major" behavior along with it. > I agree. I'm working on some clean-ups that I'll send out soon, though > I'm worried about some of the various boot-time options... Looking forward to seeing them. >>> If someone is booting with "security=selinux,tomoyo" and then SARA >>> lands upstream, does that person have to explicitly add "sara" to >>> their boot args, since they're doing a non-default list of LSMs? >> Yes. security= is explicit. >> >>> (I actually prefer the answer being "yes" here, FWIW, I just want to >>> nail down the expectations.) >> For now let's leave the minor (capability, yama, loadpin) as they are, >> and require all new modules of any flavor to use full registration. > I would even be fine to convert yama and loadpin. That shouldn't be difficult. >> We could consider something like >> >> security=$lsm # Stack with $lsm at priority 2 - Existing behavior >> $lsm.stacked=N # Add $lsm to the stack at priority N. Delete if N == 0 >> >> It's OK to specify "selinux.stacked=2" and "sara.stacked=2". Which gets >> called first is left up to the system to decide. Whatever the behavior is >> gets documented. Capability will always be first and have priority 1. >> It's OK to specify "smack.stacked=1". > I'm less excited about this kind of stacking priority, but, whatever > the case, I think my cleanups may help with whatever we decide. OK >> The default stack is determined by CONFIG_SECURITY_$lsm_STACKED at >> build time. CONFIG_SECURITY_$lsm_STACKED changes from a boolean to >> an integer value to establish the default hook order. >> >> /sys/kernel/security/lsm reports the modules in hook call order. > Didn't I send a patch to new-line terminate this list? I always get > annoyed when I "cat" it. ;) SELinux set the precedence on that one. Not my fault! >> /sys/kernel/security/lsm-stack reports the list with the hook call priority >> >> capability:1,yama:1,selinux:1,sara:5,landlack:17 >> >> If stacking is not configured $lsm.stacked=0 is treated as security=none. >> For other values of N $lsm.stacked=N is treated as security=$lsm. > I feel like "order" is bad enough. Can we avoid adding "priority"? Sorry. I changed terminology (order and priority) halfway through the message. Yes, I like order better. We should stick with that.
