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    SubjectRe: [PATCH v5 1/1] use crc32 instead of md5 for hibernation e820 integrity check
    On Thu, Apr 8, 2021 at 5:26 PM Eric Biggers <ebiggers@kernel.org> wrote:
    >
    > On Thu, Apr 08, 2021 at 03:32:38PM +0200, Rafael J. Wysocki wrote:
    > > On Thu, Apr 8, 2021 at 3:15 PM Chris von Recklinghausen
    > > <crecklin@redhat.com> wrote:
    > > >
    > > > Suspend fails on a system in fips mode because md5 is used for the e820
    > > > integrity check and is not available. Use crc32 instead.
    > > >
    > > > This patch changes the integrity check algorithm from md5 to
    > > > crc32. This integrity check is used only to verify accidental
    > > > corruption of the hybernation data
    > >
    > > It isn't used for that.
    > >
    > > In fact, it is used to detect differences between the memory map used
    > > before hibernation and the one made available by the BIOS during the
    > > subsequent resume. And the check is there, because it is generally
    > > unsafe to load the hibernation image into memory if the current memory
    > > map doesn't match the one used when the image was created.
    >
    > So what types of "differences" are you trying to detect? If you need to detect
    > differences caused by someone who maliciously made changes ("malicious" implies
    > they may try to avoid detection), then you need to use a cryptographic hash
    > function (or a cryptographic MAC if the hash value isn't stored separately). If
    > you only need to detect non-malicious changes (normally these would be called
    > "accidental" changes, but sure, it could be changes that are "intentionally"
    > made provided that the other side can be trusted to not try to avoid
    > detection...)

    That's the case here.

    > then a non-cryptographic checksum would be sufficient.

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