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    SubjectRe: [linux-security] Malicious Linux modules (fwd)
    Date
    Olaf Titz <olaf@bigred.inka.de> wrote:
    >> Loading modules lets potentially untrustworthy code into your trusted
    >> environment so the modules need checked first. A possible approach is
    >> to use code signing so the kernel can check that the code really was
    >> compiled by you.
    >
    >Modules operate on _the same_ trust level as the kernel itself. If a
    >hacker can install a malicious module, he can as well install a
    >malicious kernel. (I.e. this attack is neither new nor a special Linux
    >risk, it just makes patching the kernel easier.)
    >
    >So it is futile for the kernel to check module integrity - you need a
    >_higher_ trust level. "Higher trust level than the kernel" implies
    >media the kernel couldn't physically write to after the attack. I.e.
    >boot from a floppy and re-install everything from trusted media (CD,
    >backup tapes), check file signatures against separately stored media,
    >etc.

    I think RPM is usefull here, RPM is able to verify installed files against
    their origial checksum/signature. One of the basics of security is
    "provability". To improve security these checks on signature could be
    done at regular intervals. All added software should be packed in RPM's
    too. A complete security check can be quite time consuming. The test:
    "check for all files if
    they belong to a trusted package" cane be done
    with RPM too, but maybe it is easier to create a sepearte test for
    this one. A medium without modification possibilities (like ROM or CD-Rom)
    or a trusted server should be used to store the signatures or a master
    signature over the files containing the signatures.

    Chel

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