6 ms·

So the discussed sources of entropy are - interrupts - rdrand - timer/instruction jitter Why don't they throw more sources at the problem? LSBs from

So the discussed sources of entropy are - interrupts - rdrand - timer/instruction jitter Why don't they throw more sources at the problem? LSBs from analog sources such as audio inputs, stray network packets (put the nic in promiscuous mode). Even uninitialized memory might be worth a few bits (not all systems zero it on boot).

bonzini 7y ago
This is happening so early that audio and network (and /var where the persistent seed is stored) aren't up. The kernel doesn't want to be susceptible to hangs unless userspace brings up all entropy sources early enough.
- the8472 7y ago
  The issue was GDM/X11 starting though, that's later into the boot sequence.
- nwallin 7y ago
  This is about GDM, which is the last thing that gets started. Hardware devices are initialized before init is started, so you should still be able to gather entropy from the various input devices. Lack of entropy can't cause the kernel to not boot; it's just userspace (typically services which require encryption) which can have a problem. It would be silly to start a webserver or sshd before the FS is remounted rw.
  - megous 7y ago
    Not if you use modules.
    - loeg 7y ago
      Can you elaborate on what you mean?
      - megous 7y ago
        Init is executed before modules start being loaded.
joemi 7y ago
I'm not sure that analog sources can be relied on to be present in all systems. And I'm not sure that your other suggestions (stray network packets or uninitialized memory) can be relied on to to be sufficiently random in all systems. It seems to me like they're looking for solutions that rely on the processor for the randomness and not on any peripherals.
deleted 7y ago
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loeg 7y ago
More sources don't help; the problem is very early availability. Networking isn't online yet. Uninitialized memory is probably worthless.
buckminster 7y ago
They should display a prompt: "Press any number of keys to continue".
boring_twenties 7y ago
Sorry if I'm missing something, but what would promiscuous mode do in this age, exactly? I personally haven't seen a hub in at least a decade, and on a switched network, is there any difference?
- icedchai 7y ago
  Yes, there's tons of non-unicast traffic: ARP requests, spanning tree, various UDP broadcast packets, etc...
  - teraflop 7y ago
    The NIC would receive broadcast traffic regardless of whether promiscuous mode is enabled, wouldn't it?
  - boring_twenties 7y ago
    Broadcast packets are received in non-promiscuous mode, obviously. Otherwise none of this would work without it.
    - icedchai 7y ago
      Yes, you are correct.. I was more commenting that the "stray" network packets could still be used for timing.

bonzini 7y ago

This is happening so early that audio and network (and /var where the persistent seed is stored) aren't up. The kernel doesn't want to be susceptible to hangs unless userspace brings up all entropy sources early enough.

the8472 7y ago
The issue was GDM/X11 starting though, that's later into the boot sequence.
nwallin 7y ago
This is about GDM, which is the last thing that gets started. Hardware devices are initialized before init is started, so you should still be able to gather entropy from the various input devices. Lack of entropy can't cause the kernel to not boot; it's just userspace (typically services which require encryption) which can have a problem. It would be silly to start a webserver or sshd before the FS is remounted rw.
- megous 7y ago
  Not if you use modules.
  - loeg 7y ago
    Can you elaborate on what you mean?
    - megous 7y ago
      Init is executed before modules start being loaded.

joemi 7y ago

I'm not sure that analog sources can be relied on to be present in all systems. And I'm not sure that your other suggestions (stray network packets or uninitialized memory) can be relied on to to be sufficiently random in all systems. It seems to me like they're looking for solutions that rely on the processor for the randomness and not on any peripherals.

deleted 7y ago

[deleted]

loeg 7y ago

More sources don't help; the problem is very early availability. Networking isn't online yet. Uninitialized memory is probably worthless.

buckminster 7y ago

They should display a prompt: "Press any number of keys to continue".

boring_twenties 7y ago

Sorry if I'm missing something, but what would promiscuous mode do in this age, exactly? I personally haven't seen a hub in at least a decade, and on a switched network, is there any difference?

icedchai 7y ago
Yes, there's tons of non-unicast traffic: ARP requests, spanning tree, various UDP broadcast packets, etc...
- teraflop 7y ago
  The NIC would receive broadcast traffic regardless of whether promiscuous mode is enabled, wouldn't it?
- boring_twenties 7y ago
  Broadcast packets are received in non-promiscuous mode, obviously. Otherwise none of this would work without it.
  - icedchai 7y ago
    Yes, you are correct.. I was more commenting that the "stray" network packets could still be used for timing.