LWN: Comments on "Making attacks a little harder"

0400 /proc/kallsyms not in 2.6.37

kevinm — Wed, 08 Dec 2010 12:27:49 +0000

Anyone who wants the effect can simply add:

chmod 400 /proc/kallsyms

to their /etc/rc.local or similar.

Pointer values

epa — Mon, 22 Nov 2010 10:35:18 +0000

On second thoughts I realize that even if you knew the secret value you wouldn't be able to reverse the hash function to get the original pointers back. So if you wanted to hide the pointer values you'd need to encrypt them, with a much longer secret key than a mere 64 bits.

0400 /proc/kallsyms not in 2.6.37

spender — Sat, 20 Nov 2010 00:56:27 +0000

FYI, the patch has been reverted:
http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-...

-Brad

Pointer values

Cyberax — Thu, 18 Nov 2010 19:47:28 +0000

Make an IOCTL and stop inventing lame interfaces?

Pointer values

andfarm — Thu, 18 Nov 2010 18:40:54 +0000

Make it a truncated SHA1 hash, then? Same idea.

Pointer values

Cyberax — Thu, 18 Nov 2010 15:50:22 +0000

And code to decrypt this XOR number will be published in 20 seconds after kernel release.

Pointer values

epa — Thu, 18 Nov 2010 13:12:17 +0000

Generate a 64-bit random value at boot time, then XOR each pointer value with it and hash the result with SHA or similar. These pointers can be recorded in the log file safely; so an unprivileged user can see when two pointers are equal but no other information. The root user can ask the kernel for the secret random value and so decode the log file.