Messages in this thread | | | Subject | Re: [PATCH v5 0/7] IMA: Infrastructure for measurement of critical kernel data | From | Tushar Sugandhi <> | Date | Thu, 12 Nov 2020 14:18:53 -0800 |
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On 2020-11-04 4:31 p.m., Mimi Zohar wrote: > Hi Tushar, > > Measuring "critical kernel data" is not a new infrastructure, simply a > new IMA hook. Please update the above Subject line to "support for > measuring critical kernel data". > Thanks a lot. Will update. > On Sun, 2020-11-01 at 14:26 -0800, Tushar Sugandhi wrote: >> There are several kernel subsystems that contain critical data which if >> accidentally or maliciously altered, can compromise the integrity of the >> system. Examples of such subsystems would include LSMs like SELinux, or >> AppArmor; or device-mapper targets like dm-crypt, dm-verity etc. >> "critical data" in this context is kernel subsystem specific information >> that is stored in kernel memory. Examples of critical data could be >> kernel in-memory r/o structures, hash of the memory structures, or >> data that represents a linux kernel subsystem state. > > This is a bit better, but needs to be much clearer. Please define > "critical data", not by example, but by describing "what" critical > kernel data is. "There are several kernel subsystems ...." is an > example of "how" it would be used, not a definition. Without a clear > definition it will become a dumping ground for measuring anything > anyone wants to measure. As a result, it may be abused. > Good point. I will come up with a better definition. >> >> This patch set defines a new IMA hook namely CRITICAL_DATA, and a >> function ima_measure_critical_data() - to measure the critical data. > > The name of the IMA hook is ima_measure_critical_data. This is similar > to the LSM hooks, which are prefixed with "security_". (For a full > list of LSM hooks, refer to lsm_hook_defs.h.) > Thanks for the clarification. I will update this description. >> Kernel subsystems can use this functionality, to take advantage of IMA's >> measuring and quoting abilities - thus ultimately enabling remote >> attestation for the subsystem specific information stored in the kernel >> memory. >> >> The functionality is generic enough to measure the data of any kernel >> subsystem at run-time. To ensure that only data from supported sources >> are measured, the kernel subsystem needs to be added to a compile-time >> list of supported sources (an "allowed list of components"). IMA >> validates the source passed to ima_measure_critical_data() against this >> allowed list at run-time. > > Yes, this new feature is generic, but one of the main goals of IMA is > to measure and attest to the integrity of the system, not to measure > and attest to random things. > Ok. I will update the above paragraph accordingly. >> >> System administrators may want to pick and choose which kernel >> subsystem information they would want to enable for measurements, >> quoting, and remote attestation. To enable that, a new IMA policy is >> introduced. > > ^may want to limit the critical data being measured, quoted and > attested. > ^ a new IMA policy condition is defined. > Sounds good. Will update. >> >> This patch set also addresses the need for the kernel subsystems to >> measure their data before a custom IMA policy is loaded - by providing >> a builtin IMA policy. > > ^for measuring kernel critical data early, before a custom IMA policy > ... > Sounds good. Will update. >> >> And lastly, the use of the overall functionality is demonstrated by >> measuring the kernel in-memory data for one such subsystem - SeLinux. > > The purpose isn't to demonstrate the "overall functionality", but to > provide an initial caller of the new IMA hook. > Fair point. Will change the description accordingly. ~Tushar
> thanks, > > Mimi >
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