Module: Arachni::Element::Capabilities::Auditable::RDiff

Included in:
Arachni::Element::Capabilities::Auditable
Defined in:
lib/arachni/element/capabilities/auditable/rdiff.rb

Overview

Performs boolean, fault injection and behavioral analysis (using the rDiff algorithm) in order to determine whether the web application is responding to the injected data and how.

If the behavior can be manipulated by the injected data in ways that it’s not supposed to (like when evaluating injected code) then the element is deemed vulnerable.

Author:

Constant Summary collapse

RDIFF_OPTIONS = 
{
    # append our seeds to the default values
    format:    [Mutable::Format::APPEND],

    # allow duplicate requests
    redundant: true,

    # amount of rdiff iterations
    precision: 2,

    respect_method: true
}

Class Method Summary collapse

Instance Method Summary collapse

Class Method Details

.included(mod) ⇒ Object 



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# File 'lib/arachni/element/capabilities/auditable/rdiff.rb', line 34

def self.included( mod )
    # the rdiff attack performs it own redundancy checks so we need this to
    # keep track of audited elements
    @@rdiff_audited ||= BloomFilter.new
end

Instance Method Details

#rdiff_analysis(opts = {}, &block) ⇒ Object

Performs differential analysis and logs an issue should there be one.

opts = {
    :precision => 3,
    :faults    => [ 'fault injections' ],
    :bools     => [ 'boolean injections' ]
}

element.rdiff_analysis( opts )

Here’s how it goes:

  • let default be the default/original response

  • let fault be the response of the fault injection

  • let bool be the response of the boolean injection

A vulnerability is logged if:

default == bool AND bool.code == 200 AND fault != bool

The “bool” response is also checked in order to determine if it’s a custom 404, if it is it’ll be skipped.

If a block has been provided analysis and logging will be delegated to it.

Parameters:

  • opts (Hash) (defaults to: {}) —

    available options:

    • :format – as seen in Mutable::MUTATION_OPTIONS

    • :precision – amount of rdiff iterations

    • :faults – array of fault injection strings (these are supposed to force erroneous conditions when interpreted)

    • :bools – array of boolean injection strings (these are supposed to not alter the webapp behavior when interpreted)

  • block (Block) —

    block to be used for custom analysis of responses; will be passed the following:

    • injected string

    • audited element

    • default response body

    • boolean response

    • fault injection response body



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# File 'lib/arachni/element/capabilities/auditable/rdiff.rb', line 88

def rdiff_analysis( opts = {}, &block )
    opts = self.class::MUTATION_OPTIONS.merge( RDIFF_OPTIONS.merge( opts ) )

    # don't continue if there's a missing value
    auditable.values.each { |val| return if !val || val.empty? }

    return if rdiff_audited?
    rdiff_audited

    responses = {
        # will hold the original, default, response that results from submitting
        orig: nil,

        # will hold responses of boolean injections
        good: {},

        # will hold responses of fault injections
        bad:  {}
    }

    # submit the element, as is, opts[:precision] amount of times and
    # rdiff the responses in order to arrive to a refined response without
    # any superfluous dynamic content
    opts[:precision].times {
        # get the default responses
        audit( '', opts ) do |res|
            responses[:orig] ||= res.body
            # remove context-irrelevant dynamic content like banners and such
            responses[:orig] = responses[:orig].rdiff( res.body )
        end
    }

    # perform fault injection opts[:precision] amount of times and
    # rdiff the responses in order to arrive to a refined response without
    # any superfluous dynamic content
    opts[:precision].times {
        opts[:faults].each do |str|
            # get mutations of self using the fault seed, which will
            # cause an internal/silent error when evaluated
            mutations( str, opts ).each do |elem|
                print_status elem.status_string

                # submit the mutation and store the response
                elem.submit( opts ) do |res|
                    responses[:bad][elem.altered] ||= res.body.clone
                    # remove context-irrelevant dynamic content like banners and such
                    # from the error page
                    responses[:bad][elem.altered] =
                        responses[:bad][elem.altered].rdiff( res.body.clone )
                end
            end
        end
    }

    # get injection variations that will not affect the outcome of the query
    opts[:bools].each do |str|

        # get mutations of self using the boolean seed, which will not
        # alter the execution flow
        mutations( str, opts ).each do |elem|
            print_status elem.status_string

            # submit the mutation and store the response
            elem.submit( opts ) do |res|
                responses[:good][elem.altered] ||= []
                # save the response and some data for analysis
                responses[:good][elem.altered] << {
                    'str'  => str,
                    'res'  => res,
                    'elem' => elem
                }
            end
        end
    end

    # when this runs the "responses" hash will have been populated and we
    # can continue with analysis
    http.after_run {

        responses[:good].keys.each do |key|
            responses[:good][key].each do |res|

                # if there's a block passed then delegate analysis to it
                if block
                    exception_jail( false ){
                        block.call( res['str'], res['elem'], responses[:orig],
                                    res['res'], responses[:bad][key] )
                    }

                # if default_response_body == bool_response_body AND
                #    bool_response_code == 200 AND
                #    fault_response_body != bool_response_body
                elsif responses[:orig] == res['res'].body &&
                        responses[:bad][key] != res['res'].body &&
                        res['res'].code == 200

                    # check to see if the current boolean response we're analyzing
                    # is a custom 404 page
                    http.custom_404?( res['res'] ) do |bool|
                        # if this is a custom 404 page bail out
                        next if bool

                        # if this isn't a custom 404 page then it means that
                        # the element is vulnerable, so go ahead and log the issue

                        # information for the Metareport report
                        opts = {
                            injected_orig: res['str'],
                            combo:         res['elem'].auditable
                        }

                        @auditor.log({
                                var:      key,
                                opts:     opts,
                                injected: res['str'],
                                id:       res['str'],
                                elem:     res['elem'].type,
                            }, res['res']
                        )
                    end
                end

            end
        end
    }
end