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    SubjectRe: [PATCH net-next v2] net: WireGuard secure network tunnel
    Hi Dmitry,

    On Wed, Dec 18, 2019 at 11:13 AM Dmitry Vyukov <dvyukov@google.com> wrote:
    > Does it really do "verbose debug log"? I only see it is used for
    > self-tests and debug checks:

    Yes, it does, via net_dbg and co. People with the Linux "dynamic
    debugging" feature turned also get the log by twiddling with some file
    at runtime.

    > In different contexts one may enable different sets of these.
    > In particular in fuzzing context one absolutely wants additional debug
    > checks, but not self tests and definitely no verbose logging. CI and
    > various manual scenarios will require different sets as well.
    > If this does verbose logging, we won't get debug checks as well during
    > fuzzing, which is unfortunate.
    > Can make sense splitting CONFIG_WIREGUARD_DEBUG into 2 or 3 separate
    > configs (that's what I see frequently). Unfortunately there is no
    > standard conventions for anything of this, so CIs will never find your
    > boot tests and fuzzing won't find the additional checks...

    I agree that it might make sense to split this up at some point, but
    for now I think it might be a bit overkill. Both the self-tests and
    debug tests are *very* light at the moment. Down the road if these
    become heavier, I think it'd probably be a good idea, but for the time
    being it'd mostly be more complexity for nothing.

    Another more interesting point, though, you wrote
    > and definitely no verbose logging.

    Actually with WireGuard, I think that's not the case. The WireGuard
    logging has been written with DoS in mind. You /should/ be able to
    safely run it on a production system exposed to the wild Internet, and
    while there will be some additional things in your dmesg, an attacker
    isn't supposed to be able to totally flood it without ratelimiting or
    inject malicious strings into it (such as ANSI escape sequence). In
    other words, I consider the logging to be fair game attack surface. If
    your fuzzer manages to craft some nasty sequence of packets that
    tricks some rate limiting logic and lets you litter all over dmesg
    totally unbounded, I'd consider that a real security bug worth
    stressing out about. So from the perspective of letting your fuzzers
    loose on WireGuard, I'd actually like to see this option kept on.

    Jason

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