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    SubjectRe: [PATCH v3 3/8] securtiy/brute: Detect a brute force attack
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    On 2/23/21 10:20 AM, John Wood wrote:
    > Hi,
    >
    > On Sun, Feb 21, 2021 at 06:47:16PM -0800, Randy Dunlap wrote:
    >> Hi--
    >>
    >> scripts/kernel-doc does not like these items to be marked
    >> as being in kernel-doc notation. scripts/kernel-doc does not
    >> recognize them as one of: struct, union, enum, typedef, so it
    >> defaults to trying to interpret these as functions, and then
    >> says:
    >>
    >> (I copied these blocks to my test megatest.c source file.)
    >>
    >>
    >> ../src/megatest.c:1214: warning: cannot understand function prototype: 'const u64 BRUTE_EMA_WEIGHT_NUMERATOR = 7; '
    >> ../src/megatest.c:1219: warning: cannot understand function prototype: 'const u64 BRUTE_EMA_WEIGHT_DENOMINATOR = 10; '
    >> ../src/megatest.c:1228: warning: cannot understand function prototype: 'const unsigned char BRUTE_MAX_FAULTS = 200; '
    >> ../src/megatest.c:1239: warning: cannot understand function prototype: 'const unsigned char BRUTE_MIN_FAULTS = 5; '
    >> ../src/megatest.c:1249: warning: cannot understand function prototype: 'const u64 BRUTE_CRASH_PERIOD_THRESHOLD = 30000; '
    >>
    >>
    >> On 2/21/21 7:49 AM, John Wood wrote:
    >>>
    >>> +/**
    >>> + * brute_stats_ptr_lock - Lock to protect the brute_stats structure pointer.
    >>> + */
    >>> +static DEFINE_RWLOCK(brute_stats_ptr_lock);
    >>
    >>> +/**
    >>> + * BRUTE_EMA_WEIGHT_NUMERATOR - Weight's numerator of EMA.
    >>> + */
    >>> +static const u64 BRUTE_EMA_WEIGHT_NUMERATOR = 7;
    >>
    >>> +/**
    >>> + * BRUTE_EMA_WEIGHT_DENOMINATOR - Weight's denominator of EMA.
    >>> + */
    >>> +static const u64 BRUTE_EMA_WEIGHT_DENOMINATOR = 10;
    >>
    >>> +/**
    >>> + * BRUTE_MAX_FAULTS - Maximum number of faults.
    >>> + *
    >>> + * If a brute force attack is running slowly for a long time, the application
    >>> + * crash period's EMA is not suitable for the detection. This type of attack
    >>> + * must be detected using a maximum number of faults.
    >>> + */
    >>> +static const unsigned char BRUTE_MAX_FAULTS = 200;
    >>
    >>> +/**
    >>> + * BRUTE_MIN_FAULTS - Minimum number of faults.
    >>> + *
    >>> + * The application crash period's EMA cannot be used until a minimum number of
    >>> + * data has been applied to it. This constraint allows getting a trend when this
    >>> + * moving average is used. Moreover, it avoids the scenario where an application
    >>> + * fails quickly from execve system call due to reasons unrelated to a real
    >>> + * attack.
    >>> + */
    >>> +static const unsigned char BRUTE_MIN_FAULTS = 5;
    >>
    >>> +/**
    >>> + * BRUTE_CRASH_PERIOD_THRESHOLD - Application crash period threshold.
    >>> + *
    >>> + * The units are expressed in milliseconds.
    >>> + *
    >>> + * A fast brute force attack is detected when the application crash period falls
    >>> + * below this threshold.
    >>> + */
    >>> +static const u64 BRUTE_CRASH_PERIOD_THRESHOLD = 30000;
    >>
    >> Basically we don't support scalars in kernel-doc notation...
    >
    > So, to keep it commented it would be better to use a normal comment block?
    >
    > /*
    > * Documentation here
    > */
    >
    > What do you think?

    Yes, please, just a normal /* comment block.

    thanks.
    --
    ~Randy

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