def getSemantics(self, value):
if( isinstance( value, Expr)):
return self.semantics.get(value)
else:
# Try to translate into a reg
if( isinstance(value, int)):
num = value
elif( value in Arch.regNameToNum ):
num = Arch.n2r(value)
else:
return []
# Return corresponding if present
if( num in self.graph.lastMod ):
reg = SSAReg(num, self.graph.lastMod[num])
return self.semantics.get(reg)
# Or return the same
else:
return [SPair(SSAExpr(num, 0), CTrue())]
def __init__(self, addr_list, raw):
"""
addr_list = list of addresses of the gadget (if duplicate gadgets)
raw = raw string of gadget asm
"""
# Check the type of the gadget
# Check for 'int 0x80' gadgets
if( raw == '\xcd\x80' and Arch.currentIsIntel()):
self.type = GadgetType.INT80
self.asmStr = 'int 0x80'
self.hexStr = '\\xcd\\x80'
self.addrList = addr_list
self.nbInstr = self.nbInstrREIL = 1
self.semantics = Semantics()
return
# Check for 'syscall' gadgets
elif( raw == '\x0f\x05' and Arch.currentIsIntel()):
self.type = GadgetType.SYSCALL
self.asmStr = 'syscall'
self.hexStr = '\\x0f\\x05'
self.addrList = addr_list
self.nbInstr = self.nbInstrREIL = 1
self.semantics = Semantics()
return
# Translate raw assembly into REIL
# Then compute the Graph and its semantics
try:
(irsb, ins) = Arch.currentArch.asmToREIL(raw)
except Arch.ArchException as e:
raise GadgetException(str(e))
try:
self.graph = REILtoGraph(irsb)
self.semantics = self.graph.getSemantics()
except GraphException as e:
raise GadgetException("(In {}) - ".format('; '.join(str(i) for i in ins)) + str(e))
self.type = GadgetType.REGULAR
# Possible addresses
self.addrList = addr_list
# String representations
self.asmStr = '; '.join(str(i) for i in ins)
self.hexStr = '\\x' + '\\x'.join("{:02x}".format(ord(c)) for c in raw)
# Length of the gadget
self.nbInstr = len(ins)
self.nbInstrREIL = len(irsb)
# List of modified registers
# And of memory-read accesses
self._modifiedRegs = []
self._memoryReads = []
for reg_num in list(set([reg.num for reg in self.semantics.registers.keys()])):
# Check if there is an empty semantics
if( not self.getSemantics(reg_num)):
#self.semantics.registers.pop(reg)
log("Gadget ({}) : empty semantics for {}"\
.format(self.asmStr, Arch.r2n(reg_num)))
self._modifiedRegs.append(reg_num)
continue
# Get modified reg
if ((SSAExpr(reg_num,0) != self.getSemantics(reg_num)[0].expr) ):
self._modifiedRegs.append(reg_num)
# Get memory reads
for pair in self.getSemantics(reg_num):
self._memoryReads += [m[0] for m in pair.expr.getMemAcc()]
self._modifiedRegs = list(set(self._modifiedRegs))
# SP Increment
if( self.type != GadgetType.REGULAR ):
self.spInc = None
else:
sp_num = Arch.spNum()
if( not sp_num in self.graph.lastMod ):
self.spInc = 0
else:
sp = SSAReg(sp_num, self.graph.lastMod[sp_num])
if( len(self.semantics.get(sp)) == 1 ):
(isInc, inc) = self.semantics.get(sp)[0].expr.isRegIncrement(sp_num)
if( isInc ):
self.spInc = inc
else:
self.spInc = None
else:
self.spInc = None
# Return type
self.retType = RetType.UNKNOWN
self.retValue = None
if( self.type == GadgetType.REGULAR ):
ip_num = Arch.n2r(Arch.currentArch.ip)
ip = SSAReg(ip_num, self.graph.lastMod[ip_num])
sp_num = Arch.n2r(Arch.currentArch.sp)
if( self.spInc != None ):
for p in self.semantics.get(ip):
if( p.cond.isTrue()):
if( isinstance(p.expr, MEMExpr)):
addr = p.expr.addr
(isInc, inc) = addr.isRegIncrement(sp_num)
# Normal ret if the final value of the IP is value that was in memory before the last modification of SP ( i.e final_IP = MEM[final_sp - size_of_a_register )
if( isInc and inc == (self.spInc - (Arch.currentArch.octets)) ):
self.retType = RetType.RET
self.retValue = p.expr
elif( isinstance(p.expr, SSAExpr )):
self.retValue = p.expr
# Try to detect gadgets ending by 'call'
if( ins[-1]._mnemonic[:4] == "call"):
self.retType = RetType.CALL
else:
self.retType = RetType.JMP