Esempio n. 1
0
        protected override (ulong, ulong) ConsiderCode(IFileFormatStream image, uint loc)
        {
            // Setup
            var buffSize  = 0x76; // minimum number of bytes to process the longest expected function
            var leaSize   = 7;    // the length of an LEA instruction with a 64-bit register operand and a 32-bit memory operand
            var xor64Size = 3;    // the length of a XOR instruction of two 64-bit registers
            var xor32Size = 2;    // the length of a XOR instruction of two 32-bit registers
            var pushSize  = 2;    // the length of a PUSH instruction with a 64-bit register
            var offset    = 0;

            int RAX = 0, RBX = 3, RCX = 1, RDX = 2, RSI = 6, RDI = 7; // R8 = 8

            ulong pCgr = 0;                                           // the point to the code registration function

            image.Position = loc;
            var buff = image.ReadBytes(buffSize);

            // We have seen two versions of the initializer:
            // 1. Regular version
            // 2. Inlined version with il2cpp::utils::RegisterRuntimeInitializeAndCleanup(CallbackFunction, CallbackFunction, order)

            // Version 1 passes "this" in rcx and the arguments in rdx (our wanted pointer), r8d (always zero) and r9d (always zero)
            //           or "this" in rdi, and the arguments in rsi (our wanted pointer), edx (always zero) and ecx (always zero)
            // Version 2 has a standard prologue and loads the wanted pointer into rax or rbp (lea rax/rbp)

            (int reg, uint operand)? lea;

            // Check for regular version
            // Generalize it as follows:
            // - each instruction must be lea r64, imm32 or xor r32, r32
            // - xors must always have the same register for both operands
            // - lea that can't be mapped into the file is the pointer to 'this', otherwise it's the pointer to the init function
            // - the last instruction should always be jmp (not currently enforced)
            // - function length should not be longer than 5 instructions (two leas, two xors and one jmp)

            offset = 0;
            for (var instructions = 0; instructions < 4; instructions++)
            {
                // All allowed instruction types
                var xor32 = getXorR32R32(buff, offset);
                var xor64 = getXorR64R64(buff, offset);
                lea = getLea(buff, offset);

                if (xor32 != null && xor32.Value.reg_op1 == xor32.Value.reg_op2)
                {
                    offset += xor32Size;
                }
                else if (xor64 != null && xor64.Value.reg_op1 == xor64.Value.reg_op2)
                {
                    offset += xor64Size;
                }
                else if (lea != null)
                {
                    offset += leaSize;

                    if (pCgr == 0)
                    {
                        try {
                            // We may have found Il2CppCodegenRegistration(void)
                            pCgr = image.GlobalOffset + loc + (ulong)offset + lea.Value.operand;
                            var newLoc = image.MapVATR(pCgr);
                        }
                        catch (InvalidOperationException) {
                            // this pointer
                            pCgr = 0;
                        }
                    }
                }
                else
                {
                    // not lea or xor
                    pCgr = 0;
                    break;
                }
            }

            // Check for inlined version
            if (pCgr == 0)
            {
                // Check for prologue
                // - A sequence of 0 or more mov [rsp+argX], rXX followed by 1 or more push rXX
                offset = 0;
                while (isMovRM64R64(buff, offset))
                {
                    offset += 5;
                }

                if (isPushR64(buff, offset))
                {
                    // Linear sweep for LEA
                    var leaInlined = findLea(buff, pushSize, buffSize - pushSize);
                    if (leaInlined != null)
                    {
                        pCgr = image.GlobalOffset + loc + (uint)leaInlined.Value.foundOffset + (uint)leaSize + leaInlined.Value.operand;
                    }
                }
            }

            // Assume we've found the pointer to Il2CppCodegenRegistration(void) and jump there
            if (pCgr != 0)
            {
                try {
                    Image.Position = Image.MapVATR(pCgr);
                }

                // Couldn't map virtual address to data in file, so it's not this function
                catch (InvalidOperationException) {
                    pCgr = 0;
                }
            }

            // Find the first 2 LEAs which we'll hope contain pointers to CodeRegistration and MetadataRegistration

            // There are two options here:
            // 1. il2cpp::vm::MetadataCache::Register is called directly with arguments in rcx, rdx, r8 or rdi, rsi, rdx (lea, lea, lea, jmp)
            // 2. The two functions being inlined. The arguments are loaded sequentially into rax after the prologue

            if (pCgr != 0)
            {
                var buff2Size = 0x50;
                var buff2     = image.ReadBytes(buffSize);
                offset = 0;

                var leas = new Dictionary <(int index, ulong address), int>();

                // Find the first three LEAs in the function
                while (offset + leaSize < buff2Size && leas.Count < 3)
                {
                    var nextLea = findLea(buff2, offset, buff2Size - (offset + leaSize));

                    // Use the original pointer found, not the file location + GlobalOffset because the data may be in a different section
                    if (nextLea != null)
                    {
                        leas.Add((leas.Count, pCgr + (uint)nextLea.Value.foundOffset + (uint)leaSize + nextLea.Value.operand), nextLea.Value.reg);
                    }

                    offset = nextLea?.foundOffset + leaSize ?? buff2Size;
                }

                if ((image.Version < 21 && leas.Count == 2) || (image.Version >= 21 && leas.Count == 3))
                {
                    // Register-based argument passing?
                    var leaRSI = leas.FirstOrDefault(l => l.Value == RSI).Key.address;
                    var leaRDI = leas.FirstOrDefault(l => l.Value == RDI).Key.address;

                    if (leaRSI != 0 && leaRDI != 0)
                    {
                        return(leaRDI, leaRSI);
                    }

                    var leaRCX = leas.FirstOrDefault(l => l.Value == RCX).Key.address;
                    var leaRDX = leas.FirstOrDefault(l => l.Value == RDX).Key.address;

                    if (leaRCX != 0 && leaRDX != 0)
                    {
                        return(leaRCX, leaRDX);
                    }

                    // RAX sequential loading? If so, take the first two arguments
                    var leasRAX = leas.Where(l => l.Value == RAX).OrderBy(l => l.Key.index).Select(l => l.Key.address).ToArray();
                    if (leasRAX.Length > 1)
                    {
                        return(leasRAX[0], leasRAX[1]);
                    }
                }
            }

            // If no initializer is found, we may be looking at a DT_INIT function which calls its own function table manually
            // In the sample we have seen (PlayStation 4), this function runs through two function tables:
            // 1. Start address of table loaded into rbx, pointer past end of table in r12 (lea rbx; lea r12)
            // 2. Pointer to final address of 2nd table loaded into rbx (lea rbx), runs backwards (8 bytes per entry) until finding 0xFFFFFFFF_FFFFFFFF
            // The strategy: find these LEAs, acquire and merge the two function tables, then call ourselves in a loop to check each function address

            // Expect function prologue and at least 3 64-bit register pushes (there are probably more)
            if (!isPrologue(buff) || !isPushR64(buff, 4) || !isPushR64(buff, 6) || !isPushR64(buff, 8))
            {
                return(0, 0);
            }

            // Find the start and end addresses of the first function table
            var leaOfStart = findLea(buff, 10, buffSize - 10);

            if (leaOfStart == null || leaOfStart.Value.reg != RBX) // Most be lea rbx
            {
                return(0, 0);
            }

            var leaOfEnd = findLea(buff, leaOfStart.Value.foundOffset + leaSize, buffSize - (leaOfStart.Value.foundOffset + leaSize));

            if (leaOfEnd == null || leaOfEnd.Value.reg == RBX) // Must be lea with any register besides rbx
            {
                return(0, 0);
            }

            var ptrStart1 = leaOfStart.Value.foundOffset + leaSize + leaOfStart.Value.operand;
            var ptrEnd1   = leaOfEnd.Value.foundOffset + leaSize + leaOfEnd.Value.operand;

            // Find the address of the last item in the second function table
            var leaOfLastItem = findLea(buff, leaOfEnd.Value.foundOffset + leaSize, buffSize - (leaOfEnd.Value.foundOffset + leaSize));

            if (leaOfLastItem == null || leaOfLastItem.Value.reg != 0b11) // Must be lea rbx
            {
                return(0, 0);
            }

            var entrySize = 8; // 64-bit array entries
            var ptrEnd2   = leaOfLastItem.Value.foundOffset + leaSize + leaOfLastItem.Value.operand + entrySize;

            // Work backwards to find the address of the first item in the second function table
            var ptrStart2 = ptrEnd2;

            while (image.ReadUInt64(image.MapVATR((ulong)ptrStart2)) != 0xFFFF_FFFF_FFFF_FFFF)
            {
                ptrStart2 -= entrySize;
            }
            ptrStart2 += entrySize;

            // Acquire both function tables
            var funcs1 = image.ReadMappedWordArray((ulong)ptrStart1, (int)(ptrEnd1 - ptrStart1) / entrySize);
            var funcs2 = image.ReadMappedWordArray((ulong)ptrStart2, (int)(ptrEnd2 - ptrStart2) / entrySize);

            // Check every function
            var funcs = funcs1.Concat(funcs2);

            foreach (var pFunc in funcs)
            {
                var result = ConsiderCode(image, image.MapVATR((ulong)pFunc));
                if (result != (0, 0))
                {
                    return(result);
                }
            }
            return(0, 0);
        }
Esempio n. 2
0
        private Dictionary <uint, ulong> sweepForAddressLoads(List <uint> func, ulong baseAddress, IFileFormatStream image)
        {
            // List of registers and addresses loaded into them
            var regs = new Dictionary <uint, ulong>();

            // Iterate each instruction
            var pc = baseAddress;

            foreach (var inst in func)
            {
                // Is it an ADRP Xn, #page?
                if (getAdrp(inst, pc) is (uint reg, ulong page))
                {
                    // If we've had an earlier ADRP for the same register, we'll discard the previous load
                    if (regs.ContainsKey(reg))
                    {
                        regs[reg] = page;
                    }
                    else
                    {
                        regs.Add(reg, page);
                    }
                }

                if (getAdr(inst, pc) is (uint reg_adr, ulong addr))
                {
                    if (regs.ContainsKey(reg_adr))
                    {
                        regs[reg_adr] = addr;
                    }
                    else
                    {
                        regs.Add(reg_adr, addr);
                    }
                }

                // Is it an ADD Xm, Xn, #offset?
                if (getAdd64(inst) is (uint reg_n, uint reg_d, uint imm))
                {
                    // We are only interested in registers that have already had an ADRP, and the ADD must be to itself
                    if (reg_n == reg_d && regs.ContainsKey(reg_d))
                    {
                        regs[reg_d] += imm;
                    }
                }

                // Is it an LDR Xm, [Xn, #offset]?
                if (getLdr64ImmOffset(inst) is (uint reg_t, uint reg_ldr_n, uint simm))
                {
                    // We are only interested in registers that have already had an ADRP, and the LDR must be to itself
                    if (reg_t == reg_ldr_n && regs.ContainsKey(reg_ldr_n))
                    {
                        regs[reg_ldr_n] += simm * 8; // simm is a byte offset in a multiple of 8

                        // Now we have a pointer address, dereference it
                        regs[reg_ldr_n] = image.ReadUInt64(image.MapVATR(regs[reg_ldr_n]));
                    }
                }

                // Advance program counter which we need to calculate ADRP pages correctly
                pc += 4;
            }
            return(regs);
        }