On Thu, 2009-07-30 at 15:01 -0500, Serge E. Hallyn wrote: > Quoting Stephen Smalley (sds@xxxxxxxxxxxxx): > > On Thu, 2009-07-30 at 13:50 -0400, Eric Paris wrote: > > > On Thu, 2009-07-30 at 11:58 -0400, Stephen Smalley wrote: > > > > On Thu, 2009-07-30 at 10:54 -0500, Serge E. Hallyn wrote: > > > > > Quoting Eric Paris (eparis@xxxxxxxxxx): > > > > > > On Thu, 2009-07-30 at 00:14 -0500, Serge E. Hallyn wrote: > > > > > > > Quoting Eric Paris (eparis@xxxxxxxxxx): > > > > > > > > Currently we duplicate the mmap_min_addr test in cap_file_mmap and in > > > > > > > > security_file_mmap if !CONFIG_SECURITY. This patch moves cap_file_mmap > > > > > > > > into commoncap.c and then calls that function directly from > > > > > > > > security_file_mmap ifndef CONFIG_SECURITY like all of the other capability > > > > > > > > checks are done. > > > > > > > > > > > > > > It also > > > > > > > > > > > > > > 1. changes the return value in error case from -EACCES to > > > > > > > -EPERM > > > > > > > 2. no onger sets PF_SUPERPRIV in t->flags if the capability > > > > > > > is used. > > > > > > > > > > > > > > Do we care about these? > > > > > > > > > > > > Personally, not really, but I'll gladly put them back if you care. #2 > > > > > > seems more interesting to me than number 1. I actually kinda like > > > > > > getting EPERM from caps rather than EACCES since them I know if I was > > > > > > denied by selinux or by caps..... > > > > > > > > > > > > -Eric > > > > > > > > > > Yup, I asked bc I didn't particularly care myself. > > > > > > > > > > I think I agree with you about -EPERM being better anyway. However I > > > > > (now) think in this case PF_SUPERPRIV definately should be set, as this > > > > > is a clear use of a capability to do something that couldn't have been > > > > > done without it. > > > > > > > > On a related but different note, we should consider all current uses of > > > > cap_capable(), as they represent capability checks that will not be > > > > subject to a further restrictive check by other security modules. In > > > > this case and in the vm_enough_memory case, that is intentional, but not > > > > so clear for other uses in commoncap.c. > > > > > > Most of commoncap.c is called either as a secondary hook from the active > > > lsm (aka selinux calls the commoncap.c functions) or in the ! > > > CONFIG_SECURITY case. > > > > > > I'll audit this afternoon to see which of them might not fit these > > > rules.... > > > > That isn't what I meant. Most of the commoncap functions call capable() > > rather than directly calling cap_capable(), thereby causing: > > - PF_SUPERPRIV to be set, and > > - The primary security module (e.g. SELinux) to apply its own > > restrictive check. > > > > That is useful as it allows SELinux or AppArmor or TOMOYO to veto e.g. > > CAP_SYS_PTRACE without replicating the same logic within its own hook. > > > > The current exceptions are: > > cap_inh_is_capped() called from cap_capset(), > > cap_task_prctl() in the PR_SET_SECUREBITS case, > > cap_vm_enough_memory(), > > cap_file_mmap() after your patch. > > > > The latter two are indeed cases where we made a conscious choice that > > SELinux would not apply its capability check against policy. But the > > first two are unclear to me. > > cap_inh_is_capped: > > I'm not sure why it's cap_capable() instead of capable(). However, if we > switch to using capable(), then we should switch the conditions in the caller > around, since at the moment just because the capable() check returned true > doesn't mean that we actually end up needing it. > > (CC:ing Andrew Morgan as I believe he wrote this and may have had a reason) > > cap_task_prctl: I don't see any reason why that shouldn't be capable(). > > cap_vm_enough_memory(): I seem to recall we explicitly decided that we > did not want PF_SUPERPRIV set in this case. Yes - that one was intentional, as it gets applied to all tasks that allocate mappings. For the same reason, we don't audit that check in SELinux. > cap_file_mmap(): well now that you mention it, it does seem like SELinux > would want a say in whether the task gets CAP_SYS_RAWIO here, so maybe > it should be capable() after all? No, we apply our own specific permission check for it. -- Stephen Smalley National Security Agency -- This message was distributed to subscribers of the selinux mailing list. If you no longer wish to subscribe, send mail to majordomo@xxxxxxxxxxxxx with the words "unsubscribe selinux" without quotes as the message.
