В Mon, 6 Nov 2017 19:22:55 +0000 "Magalhaes, Guilherme (Brazil R&D-CL)" <guilherme.magalhaes@xxxxxxx> пишет: > We are trying to understand why some file measurements are skipped > by IMA. In some circumstances, it seems that this could lead to an > incorrect assessment of the integrity of the host. Consider the > following, example in which we begin with a vulnerable bash binary > (e.g. Shellshock) and patch it. > > 1. Load vulnerable bash (measured by IMA) > 2. Patch the bash file > 3. Load good bash (measured by IMA) > 4. Change back to vulnerable bash > 5. Load vulnerable bash (not measured by IMA) > > After step 5, the IMA logs appear to tell you that the system is > using a good binary, but a vulnerable binary is installed and being > used. > > We identified that 'ima_htable.queue' prevented the measurement at > step 5 since the same vulnerable bash was loaded on step 1 and 5 and > then its respective hash was already present in 'ima_htable.queue'. > > So in this scenario the last/current file state is not identified > using the IMA log. Is it not important to identify through the IMA > log whether or not the last known file state is good? > > Does anybody know why 'ima_htable.queue' is preventing already > logged file hashes from being re-measured? > > -- > Guilherme > As I understood, you have FS mounted with i_version option, after step 2 IMA hash was updated in file IMA xattr (plus, in ima_check_last_writer() iint->measured_pcrs was set to 0 in order to measure changed file next time again), but in step 5 file not measured by IMA? Right? -- Best regards, Mikhail Kurinnoi
