350 lines
8.0 KiB
Ruby
350 lines
8.0 KiB
Ruby
#!/usr/bin/env ruby
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module Rex
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module Arch
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#
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# everything here is mostly stole from vlad's perl x86 stuff
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#
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module X86
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#
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# Register number constants
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#
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EAX = AL = AX = ES = 0
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ECX = CL = CX = CS = 1
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EDX = DL = DX = SS = 2
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EBX = BL = BX = DS = 3
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ESP = AH = SP = FS = 4
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EBP = CH = BP = GS = 5
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ESI = DH = SI = 6
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EDI = BH = DI = 7
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REG_NAMES32 = [ 'eax', 'ecx', 'edx', 'ebx',
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'esp', 'ebp', 'esi', 'edi' ] # :nodoc:
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# Jump tp a specific register
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def self.jmp_reg(str)
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reg = reg_number(str)
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_check_reg(reg)
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"\xFF" + [224 + reg].pack('C')
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end
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# This method returns the opcodes that compose a jump instruction to the
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# supplied relative offset.
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def self.jmp(addr)
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"\xe9" + pack_dword(rel_number(addr))
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end
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#
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# This method adds/subs a packed long integer
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#
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def self.dword_adjust(dword, amount=0)
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[dword.unpack('V')[0] + amount].pack('V')
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end
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#
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# This method returns the opcodes that compose a tag-based search routine
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#
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def self.searcher(tag)
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"\xbe" + dword_adjust(tag,-1)+ # mov esi, Tag - 1
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"\x46" + # inc esi
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"\x47" + # inc edi (end_search:)
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"\x39\x37" + # cmp [edi],esi
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"\x75\xfb" + # jnz 0xa (end_search)
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"\x46" + # inc esi
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"\x4f" + # dec edi (start_search:)
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"\x39\x77\xfc" + # cmp [edi-0x4],esi
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"\x75\xfa" + # jnz 0x10 (start_search)
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jmp_reg('edi') # jmp edi
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end
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#
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# This method returns the opcodes that compose a short jump instruction to
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# the supplied relative offset.
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#
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def self.jmp_short(addr)
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"\xeb" + pack_lsb(rel_number(addr, -2))
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end
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#
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# This method returns the opcodes that compose a relative call instruction
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# to the address specified.
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#
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def self.call(addr)
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"\xe8" + pack_dword(rel_number(addr, -5))
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end
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#
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# This method returns a number offset to the supplied string.
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#
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def self.rel_number(num, delta = 0)
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s = num.to_s
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case s[0, 2]
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when '$+'
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num = s[2 .. -1].to_i
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when '$-'
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num = -1 * s[2 .. -1].to_i
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when '0x'
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num = s.hex
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else
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delta = 0
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end
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return num + delta
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end
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#
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# This method returns the number associated with a named register.
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#
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def self.reg_number(str)
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return self.const_get(str.upcase)
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end
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#
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# This method returns the register named associated with a given register
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# number.
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#
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def self.reg_name32(num)
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_check_reg(num)
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return REG_NAMES32[num].dup
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end
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#
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# This method generates the encoded effective value for a register.
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#
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def self.encode_effective(shift, dst)
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return (0xc0 | (shift << 3) | dst)
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end
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#
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# This method generates the mod r/m character for a source and destination
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# register.
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#
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def self.encode_modrm(dst, src)
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_check_reg(dst, src)
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return (0xc0 | src | dst << 3).chr
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end
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#
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# This method generates a push byte instruction.
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#
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def self.push_byte(byte)
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# push byte will sign extend...
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if byte < 128 && byte >= -128
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return "\x6a" + (byte & 0xff).chr
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end
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raise ::ArgumentError, "Can only take signed byte values!", caller()
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end
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#
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# This method generates a push dword instruction.
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#
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def self.push_dword(val)
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return "\x68" + [ val ].pack('V')
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end
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#
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# This method generates a pop dword instruction into a register.
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#
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def self.pop_dword(dst)
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_check_reg(dst)
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return (0x58 | dst).chr
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end
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#
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# This method generates an instruction that clears the supplied register in
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# a manner that attempts to avoid bad characters, if supplied.
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#
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def self.clear(reg, badchars = '')
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_check_reg(reg)
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return set(reg, 0, badchars)
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end
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#
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# This method generates the opcodes that set the low byte of a given
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# register to the supplied value.
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#
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def self.mov_byte(reg, val)
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_check_reg(reg)
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# chr will raise RangeError if val not between 0 .. 255
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return (0xb0 | reg).chr + val.chr
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end
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#
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# This method generates the opcodes that set the low word of a given
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# register to the supplied value.
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#
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def self.mov_word(reg, val)
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_check_reg(reg)
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if val < 0 || val > 0xffff
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raise RangeError, "Can only take unsigned word values!", caller()
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end
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return "\x66" + (0xb8 | reg).chr + [ val ].pack('v')
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end
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#
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# This method generates the opcodes that set the a register to the
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# supplied value.
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#
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def self.mov_dword(reg, val)
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_check_reg(reg)
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return (0xb8 | reg).chr + [ val ].pack('V')
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end
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#
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# This method is a general way of setting a register to a value. Depending
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# on the value supplied, different sets of instructions may be used.
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#
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# TODO: Make this moderatly intelligent so it chain instructions by itself
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# (ie. xor eax, eax + mov al, 4 + xchg ah, al)
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def self.set(dst, val, badchars = '')
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_check_reg(dst)
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# If the value is 0 try xor/sub dst, dst (2 bytes)
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if(val == 0)
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opcodes = Rex::Text.remove_badchars("\x29\x2b\x31\x33", badchars)
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if !opcodes.empty?
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return opcodes[rand(opcodes.length)].chr + encode_modrm(dst, dst)
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end
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# TODO: SHL/SHR
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# TODO: AND
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end
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# try push BYTE val; pop dst (3 bytes)
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begin
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return _check_badchars(push_byte(val) + pop_dword(dst), badchars)
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rescue ::ArgumentError, RuntimeError, RangeError
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end
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# try clear dst, mov BYTE dst (4 bytes)
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begin
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break if val == 0
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return _check_badchars(clear(dst, badchars) + mov_byte(dst, val), badchars)
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rescue ::ArgumentError, RuntimeError, RangeError
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end
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# try mov DWORD dst (5 bytes)
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begin
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return _check_badchars(mov_dword(dst, val), badchars)
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rescue ::ArgumentError, RuntimeError, RangeError
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end
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# try push DWORD, pop dst (6 bytes)
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begin
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return _check_badchars(push_dword(val) + pop_dword(dst), badchars)
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rescue ::ArgumentError, RuntimeError, RangeError
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end
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# try clear dst, mov WORD dst (6 bytes)
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begin
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break if val == 0
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return _check_badchars(clear(dst, badchars) + mov_word(dst, val), badchars)
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rescue ::ArgumentError, RuntimeError, RangeError
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end
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raise RuntimeError, "No valid set instruction could be created!", caller()
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end
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#
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# Builds a subtraction instruction using the supplied operand
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# and register.
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#
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def self.sub(val, reg, badchars = '', add = false, adjust = false, bits = 0)
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opcodes = []
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shift = (add == true) ? 0 : 5
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if (bits <= 8 and val >= -0x7f and val <= 0x7f)
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opcodes <<
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((adjust) ? '' : clear(reg, badchars)) +
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"\x83" +
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[ encode_effective(shift, reg) ].pack('C') +
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[ val.to_i ].pack('C')
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end
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if (bits <= 16 and val >= -0xffff and val <= 0)
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opcodes <<
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((adjust) ? '' : clear(reg, badchars)) +
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"\x66\x81" +
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[ encode_effective(shift, reg) ].pack('C') +
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[ val.to_i ].pack('v')
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end
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opcodes <<
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((adjust) ? '' : clear(reg, badchars)) +
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"\x81" +
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[ encode_effective(shift, reg) ].pack('C') +
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[ val.to_i ].pack('V')
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# Search for a compatible opcode
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opcodes.each { |op|
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begin
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_check_badchars(op, badchars)
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rescue
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next
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end
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return op
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}
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if opcodes.empty?
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raise RuntimeError, "Could not find a usable opcode", caller()
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end
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end
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#
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# This method generates the opcodes equivalent to subtracting with a
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# negative value from a given register.
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#
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def self.add(val, reg, badchars = '', adjust = false, bits = 0)
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sub(val, reg, badchars, true, adjust, bits)
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end
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#
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# This method wrappers packing an integer as a little-endian buffer.
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#
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def self.pack_dword(num)
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[num].pack('V')
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end
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#
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# This method returns the least significant byte of a packed dword.
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#
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def self.pack_lsb(num)
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pack_dword(num)[0,1]
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end
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#
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# This method adjusts the value of the ESP register by a given amount.
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#
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def self.adjust_reg(reg, adjustment)
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if (adjustment > 0)
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sub(adjustment, reg, '', false, false, 32)
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else
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add(adjustment, reg, '', true, 32)
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end
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end
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def self._check_reg(*regs) # :nodoc:
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regs.each { |reg|
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if reg > 7 || reg < 0
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raise ArgumentError, "Invalid register #{reg}", caller()
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end
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}
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return nil
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end
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def self._check_badchars(data, badchars) # :nodoc:
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idx = Rex::Text.badchar_index(data, badchars)
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if idx
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raise RuntimeError, "Bad character at #{idx}", caller()
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end
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return data
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end
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end
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end end
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