On Tue, 2021-02-09 at 10:23 -0800, Tushar Sugandhi wrote: > > On Mon, 2021-02-08 at 15:22 -0500, Mimi Zohar wrote: > >> On Fri, 2021-01-29 at 16:45 -0800, Tushar Sugandhi wrote: > >>> IMA does not measure duplicate buffer data since TPM extend is a very > >>> expensive operation. However, in some cases for integrity critical > >>> data, the measurement of duplicate data is necessary to accurately > >>> determine the current state of the system. Eg, SELinux state changing > >>> from 'audit', to 'enforcing', and back to 'audit' again. In this > >>> example, currently, IMA will not measure the last state change to > >>> 'audit'. This limits the ability of attestation services to accurately > >>> determine the current state of the integrity critical data on the > >>> system. > >>> > >>> This series addresses this gap by providing the ability to measure > >>> duplicate entries for integrity critical data, driven by policy. > >> > >> The same reason for re-measuring buffer data is equally applicable to > >> files. In both cases, the file or the buffer isn't re-measured if it > >> already exists in the htable. Please don't limit this patch set to > >> just buffer data. > > > Agreed. I wasn't sure if you wanted the support for files, or other > buffer measurement scenarios, except critical data. So I started the > implementation with supporting just critical data. Happy to extend it > to files and other buffer measurement scenarios as you suggested. > > > Instead of making the change on a per measurement rule basis, disabling > > "htable" would be the simplest way of forcing re-measurements. All > > that would be needed is a new Kconfig (e.g. CONFIG_IMA_DISABLE_HTABLE) > > and the associated test in ima_add_template_entry(). > > > Agreed. Earlier I wasn't sure if you wanted allow_dup support for all > the scenarios. Now that it is clear, I will implement it as you > suggested. Thank you so much for the pointers. Appreciate it. There are two different solutions - per measurement rule, disabling htable - being discussed. Disabling htable requires miminumal changes. Which version are you thinking of implementing? thanks, Mimi
