Pavel Machek <pavel@private> wrote on 05/23/2005 07:44:54 PM: > > To make this usefull, you need to: > > * have TPM chip TPM chips are becoming broadly available in many new desktop and laptop systems. Drivers are open-source, see tpmdd and TrouSerS projects on sourceforge. > * remove all the buffer overflows. I.e. if grub contains buffer > overflow in parsing menu.conf... that is not a security hole > (as of now) because only administrator can modify menu.conf. > With IMA enabled, it would make your certification useless... Taking your example: Even if you run a buffer-overflow grub, IMA will enable remote parties to differentiate between systems that run the vulnerable grub and systems that don't. IMA in this case actually can put value to running better software. Additionally, you can see whether the operating system implements 'useful' measures against buffer overflows. Information you don't easily get otherwise when communicating with /logging into a remote system. So you can determine if buffer-overflow-vulnerable applications run in operating environments that actually allow attackers to exploit such vulnerabilities. > [probably something more]. > > ...seems to me you need to do quite a lot of work to make this > usefull... Things can be useful even though they don't solve all security problems. Think of IPSEC, SSL, firewalls, tripwire. I find them useful even though they are not offering total security. The experiments are aimed at finding useful trade-offs for different usage pattern (e.g., remote access) that raise the bar for attackers. > [And now, remote-buffer-overrun in inetd probably breaks your > attestation, no? I'll just load my evil code over the network, without > changing any on-disk executables, then install my evil rootkit into > kernel by writing into /dev/kmem. How do you prevent that one?] > Pavel We have IMA kernel configuration options to detect direct writes onto /dev/kmem and some other devices. If /dev/kmem is directly opened for writing, the aggregate in the TPM is invalidated. This system will not be able to deliver a measurement list with a fitting TPM aggregate signature until next reboot and clearing of all state. Thanks Reiner
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