> -----Original Message----- > From: Mikhail Kurinnoi [mailto:viewizard@xxxxxxxxx] On Behalf Of Mikhail > Kurinnoi > Sent: segunda-feira, 6 de novembro de 2017 18:05 > To: Magalhaes, Guilherme (Brazil R&D-CL) <guilherme.magalhaes@xxxxxxx> > Cc: linux-integrity@xxxxxxxxxxxxxxx > Subject: Re: IMA skips some file measurements > > 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? That's correct. Check the use of ima_htable.queue in ima_lookup_digest_entry(). It prevents ima_add_template_entry() from actually measuring the changed file if the 'new' hash is already present in that hash table. -- Guilherme > > > > -- > Best regards, > Mikhail Kurinnoi
