On 01/14/14 at 04:17pm, Vivek Goyal wrote:
On Wed, Dec 25, 2013 at 06:07:39PM +0800, WANG Chao wrote:
[..]
if is_ssh_dump_target; then
dracut_install /var/lib/random-seed || exit $?
dracut_install -o /var/lib/random-seed || exit $?dracut_install -o /var/lib/systemd/random-seed || exit $?below is better?
dracut_install /var/lib/random-seed || dracut_install -o /var/lib/systemd/random-seed || exit $?
Using dracut_install will error out w/o -o option. I think random-seed is not essential for ssh dump, we can omit it safely. What do you think for below:
dracut_install -o /var/lib/random-seed dracut_install -o /var/lib/systemd/random-seed
I am not sure if random seed is optional. I think things will still work but enough randomness might not be there and it might make for weaker crypto and might make it little less secure in kdump environemnt.
Yes, it's right. Without sufficient entropy, the random could be theoretically vulnerable. That makes kdump environment less secure like you said.
But kdump can't force user to maintain such random seed file /var/lib/systemd/random-seed or /var/lib/random-seed. For whatever reason, this seed file could be deleted or relocated some other place.
Given the fact that entropy may be not sufficient and we must feed /dev/urandom in 2nd kernel. What makes sense to me is that we generate our own seed when creating kdump initramfs and feed this one to /dev/urandom in 2nd kernel.
It's rather simple to implement it. [inspired from man:random(4)]
In module-setup.sh, save random seed:
dd if=/dev/urandom of=${initdir}/$RANDOM_SEED \ bs=`cat /proc/sys/kernel/random/poolsize` count=1
In kdump.sh, feed /dev/urandom with our preserved randome seed:
cat $RANDOM_SEED > /dev/urandom
So neither we have to fail when kdump can't find the system-wide random seed file nor we have worry about where the seed is located.
What do you think?
Before this change, we used dracut install without -o option. That means random seem was must. So why change behavior now.
Actually it's I didn't understand why random-seed is a must.
Thanks WANG Chao
How about using following.
if [ -f /var/lib/random-seed ] dracut_install /var/lib/random-seed || exit $? elif [ -f /var/lib/systemd/random-seed ] dracut_install /var/lib/random-seed || exit $? else error
Thanks Vivek