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    SubjectRe: [PATCH 21/21] MODSIGN: Apply signature checking to modules on module load [ver #3]
    Rusty Russell <> wrote:

    > And adds a great deal of code in a supposedly security-sensitive path to
    > achieve it.
    > How about simply append a signature to the module? That'd be about 20 lines
    > of code to carefully check the bounds of the module to figure out where the
    > signature is. You could even allow multiple signatures, then have one for
    > stripped, and one for non-stripped versions.

    A big chunk of the code is dealing with the cryptographic bits - and you need
    those anyway - and if it's done right it can be shared with other things
    (eCryptfs for example; maybe CIFS from what Steve French said) and auxiliary
    keys can be stored in places other than the kernel (the TPM for example).

    > Sure, you now need to re-append that after stripping, but that's not the
    > kernel's problem.

    You may also have to remove the signature before passing it to any binutils
    tool lest it malfunction on the trailer - and would you also have to modify
    insmod and modprobe? I suspect they parse the ELF to find out about parameters
    and things.

    I've found that rpmbuild and mkinitrd alter the module files at various times,
    so you'd need a bunch of signatures, one for each (may just be two, but I can't
    guarantee that). This means the kernel build process needs to know what
    transformations are going to be applied to a module - something that has
    changed occasionally within the distribution I use and may vary between
    distributions (or even just someone building for themselves).


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