1. 01 4月, 2022 1 次提交
  2. 25 3月, 2022 1 次提交
  3. 23 3月, 2022 1 次提交
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  9. 13 3月, 2022 1 次提交
    • J
      virt: vmgenid: notify RNG of VM fork and supply generation ID · af6b54e2
      Jason A. Donenfeld 提交于
      VM Generation ID is a feature from Microsoft, described at
      <https://go.microsoft.com/fwlink/?LinkId=260709>, and supported by
      Hyper-V and QEMU. Its usage is described in Microsoft's RNG whitepaper,
      <https://aka.ms/win10rng>, as:
      
          If the OS is running in a VM, there is a problem that most
          hypervisors can snapshot the state of the machine and later rewind
          the VM state to the saved state. This results in the machine running
          a second time with the exact same RNG state, which leads to serious
          security problems.  To reduce the window of vulnerability, Windows
          10 on a Hyper-V VM will detect when the VM state is reset, retrieve
          a unique (not random) value from the hypervisor, and reseed the root
          RNG with that unique value.  This does not eliminate the
          vulnerability, but it greatly reduces the time during which the RNG
          system will produce the same outputs as it did during a previous
          instantiation of the same VM state.
      
      Linux has the same issue, and given that vmgenid is supported already by
      multiple hypervisors, we can implement more or less the same solution.
      So this commit wires up the vmgenid ACPI notification to the RNG's newly
      added add_vmfork_randomness() function.
      
      It can be used from qemu via the `-device vmgenid,guid=auto` parameter.
      After setting that, use `savevm` in the monitor to save the VM state,
      then quit QEMU, start it again, and use `loadvm`. That will trigger this
      driver's notify function, which hands the new UUID to the RNG. This is
      described in <https://git.qemu.org/?p=qemu.git;a=blob;f=docs/specs/vmgenid.txt>.
      And there are hooks for this in libvirt as well, described in
      <https://libvirt.org/formatdomain.html#general-metadata>.
      
      Note, however, that the treatment of this as a UUID is considered to be
      an accidental QEMU nuance, per
      <https://github.com/libguestfs/virt-v2v/blob/master/docs/vm-generation-id-across-hypervisors.txt>,
      so this driver simply treats these bytes as an opaque 128-bit binary
      blob, as per the spec. This doesn't really make a difference anyway,
      considering that's how it ends up when handed to the RNG in the end.
      
      Cc: Alexander Graf <graf@amazon.com>
      Cc: Adrian Catangiu <adrian@parity.io>
      Cc: Daniel P. Berrangé <berrange@redhat.com>
      Cc: Dominik Brodowski <linux@dominikbrodowski.net>
      Cc: Wei Yongjun <weiyongjun1@huawei.com>
      Tested-by: Souradeep Chakrabarti <souradch.linux@gmail.com> # With Hyper-V's virtual hardware
      Reviewed-by: NArd Biesheuvel <ardb@kernel.org>
      Reviewed-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
      Reviewed-by: NLaszlo Ersek <lersek@redhat.com>
      Signed-off-by: NJason A. Donenfeld <Jason@zx2c4.com>
      af6b54e2
  10. 12 3月, 2022 1 次提交
  11. 11 3月, 2022 1 次提交