On Tue, 29 Oct 2013 at 13:09:08 +0100, Milan Kral wrote > The problem is that in /etc/rcS.d the scripts S07cryptdisks-early, > S09cryptdisks are run before S13urandom. We are trying to read from > /dev/urandom before the Linux random number generator is properly > seeded. This can lead to predictable encryption key for the swap > partition.
That's problematic, indeed. For the record, the situation doesn't seem
to be better with systemd:
Sep 16 18:35:40 debian kernel: random: udevadm: uninitialized urandom read
(16 bytes read, 1 bits of entropy available)
Sep 16 18:35:40 debian kernel: random: udevadm: uninitialized urandom read
(16 bytes read, 1 bits of entropy available)
Sep 16 18:35:40 debian kernel: random: udevadm: uninitialized urandom read
(16 bytes read, 1 bits of entropy available)
Sep 16 18:35:40 debian kernel: random: udevadm: uninitialized urandom read
(16 bytes read, 1 bits of entropy available)
Sep 16 18:35:40 debian kernel: random: udevadm: uninitialized urandom read
(16 bytes read, 1 bits of entropy available)
Sep 16 18:35:40 debian kernel: random: udevadm: uninitialized urandom read
(16 bytes read, 1 bits of entropy available)
Sep 16 18:35:40 debian kernel: random: udevadm: uninitialized urandom read
(16 bytes read, 1 bits of entropy available)
Sep 16 18:35:40 debian kernel: random: udevadm: uninitialized urandom read
(16 bytes read, 1 bits of entropy available)
Sep 16 18:35:40 debian kernel: random: udevadm: uninitialized urandom read
(16 bytes read, 1 bits of entropy available)
Sep 16 18:35:40 debian kernel: random: udevadm: uninitialized urandom read
(16 bytes read, 1 bits of entropy available)
[…]
Sep 16 18:35:40 debian systemd[1]: Found device /dev/vda1.
Sep 16 18:35:40 debian systemd[1]: Starting Cryptography Setup for swap...
Sep 16 18:35:41 debian kernel: device-mapper: uevent: version 1.0.3
Sep 16 18:35:41 debian systemd-cryptsetup[518]: Set cipher aes, mode
xts-plain64, key size 256 bits for device /dev/vda1.
Sep 16 18:35:41 debian mkswap[576]: Setting up swapspace version 1, size =
64 MiB (67072000 bytes)
Sep 16 18:35:41 debian mkswap[576]: no label,
UUID=eca1d0f8-e1da-4ed6-867c-86c4bfca92f5
Sep 16 18:35:41 debian systemd[1]: Started Cryptography Setup for swap.
Sep 16 18:35:41 debian systemd[1]: Reached target Encrypted Volumes.
Sep 16 18:35:41 debian systemd[1]: Found device /dev/mapper/swap.
Sep 16 18:35:41 debian systemd[1]: Activating swap /dev/mapper/swap...
Sep 16 18:35:41 debian systemd[1]: Activated swap /dev/mapper/swap.
Sep 16 18:35:41 debian systemd[1]: Reached target Swap.
Sep 16 18:35:41 debian kernel: Adding 65500k swap on /dev/mapper/swap.
Priority:-1 extents:1 across:65500k FS
[…]
Sep 16 18:35:44 debian login[662]: ROOT LOGIN on '/dev/tty1'
Sep 16 18:35:48 debian kernel: random: nonblocking pool is initialized
(Note the “random: nonblocking pool is initialized” at the very end,
long after initializing swap, even after login.)
--
Guilhem.
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