135 lines
3.5 KiB
Ruby
135 lines
3.5 KiB
Ruby
# -*- coding: binary -*-
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module Rex
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module Poly
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require 'rex/poly/register'
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require 'rex/poly/block'
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require 'rex/poly/machine'
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###
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#
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# This class encapsulates the state of a single polymorphic block set
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# generation. It tracks the current set of consumed registers, the linear
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# list of blocks generated, the end-result buffer, and the phase of
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# generation. The fields exposed by the State class are intended for use only
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# by the polymorphic generation subsystem and should not be modified directly.
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#
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###
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class State
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#
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# Initializes the polymorphic generation state.
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#
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def initialize
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@block_list = nil
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reset
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end
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#
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# Resets the generation state to have a plain start by clearing all
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# consumed registers, resetting the polymorphic buffer back to its
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# beginning and destroying any block generation state.
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#
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def reset
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# Reset the generation flag on any blocks in the block list
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@block_list.each { |block|
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block[0].generated = false
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} if (@block_list)
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@regnums = Hash.new
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@buffer = ''
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@block_list = []
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@curr_offset = 0
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@first_phase = true
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@badchars = nil
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end
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#
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# Returns true if the supplied register number is already consumed.
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#
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def consumed_regnum?(regnum)
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@regnums[regnum]
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end
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#
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# Consumes a register number, thus removing it from the pool that can be
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# assigned. The consumed register number is returned to the caller.
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#
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def consume_regnum(regnum)
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raise RuntimeError, "Register #{regnum} is already consumed." if (consumed_regnum?(regnum))
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@regnums[regnum] = true
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regnum
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end
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#
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# Acquires a register number that has not already been consumed from the
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# supplied register number set and consumes it, returning the selected
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# register number to the caller. The register number is selected from the
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# set at random.
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#
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def consume_regnum_from_set(regnum_set)
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# Pick a random starting point within the supplied set.
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idx = rand(regnum_set.length)
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# Try each index in the set.
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regnum_set.length.times { |x|
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regnum = regnum_set[(idx + x) % regnum_set.length]
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next if (consumed_regnum?(regnum))
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return consume_regnum(regnum)
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}
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# If we get through the entire iteration without finding a register,
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# then we are out of registers to assign.
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raise RuntimeError, "No registers are available to consume from the set"
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end
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#
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# Eliminates a register number from the consumed pool so that it can be
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# used in the future. This happens after a block indicates that a register
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# has been clobbered.
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#
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def defecate_regnum(regnum)
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@regnums.delete(regnum)
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end
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#
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# The buffer state for the current polymorphic generation. This stores the
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# end-result of a call to generate on a LogicalBlock.
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#
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attr_accessor :buffer
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#
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# The linear list of blocks that is generated by calling the generate
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# method on a LogicalBlock.
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#
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attr_accessor :block_list
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#
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# The current offset into the polymorphic buffer that is being generated.
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# This is updated as blocks are appended to the block_list.
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#
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attr_accessor :curr_offset
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#
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# A boolean field that is used by the LogicalBlock class to track whether
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# or not it is in the first phase (generating the block list), or in the
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# second phase (generating the polymorphic buffer). This phases are used
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# to indicate whether or not the offset_of and regnum_of methods will
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# return actual results.
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#
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attr_accessor :first_phase
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#
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# Characters to avoid when selecting permutations, if any.
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#
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attr_accessor :badchars
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end
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end
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end
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