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Fix x86 analysis based on ELF PLT

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This commit is contained in:
Katy Coe
2019-10-26 15:18:55 +02:00
parent 3a66e59447
commit 9ee2e7567c
2 changed files with 59 additions and 45 deletions
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94
Il2CppInspector/Il2CppBinaryX86.cs
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@@ -15,73 +15,79 @@ namespace Il2CppInspector
protected override (ulong, ulong) ConsiderCode(IFileFormatReader image, uint loc) {
ulong metadata, code;
long funcPtr;
ushort opcode;
// Variant 1
long pCgr;
// x86
// Assembly bytes to search for at start of each function
var bytes = new byte[] {0x6A, 0x00, 0x6A, 0x00, 0x68};
image.Position = loc;
var buff = image.ReadBytes(5);
if (bytes.SequenceEqual(buff)) {
// Next 4 bytes are the function pointer being pushed onto the stack
funcPtr = image.ReadUInt32();
pCgr = image.ReadUInt32();
// Start of next instruction
if (image.ReadByte() != 0xB9)
return (0, 0);
// Jump to Il2CppCodegenRegistration
image.Position = image.MapVATR((ulong) funcPtr + 6);
image.Position = image.MapVATR((ulong) pCgr + 6);
metadata = image.ReadUInt32();
image.Position = image.MapVATR((ulong) funcPtr + 11);
image.Position = image.MapVATR((ulong) pCgr + 11);
code = image.ReadUInt32();
return (code, metadata);
}
// Variant 2
bytes = new byte[]
{0x55, 0x89, 0xE5, 0x53, 0x83, 0xE4, 0xF0, 0x83, 0xEC, 0x20, 0xE8, 0x00, 0x00, 0x00, 0x00, 0x5B};
image.Position = loc;
buff = image.ReadBytes(16);
if (!bytes.SequenceEqual(buff))
return (0, 0);
// x86 based on ELF PLT
if (image is IElfReader elf) {
var plt = elf.GetPLTAddress();
image.Position += 8;
funcPtr = image.MapVATR(image.ReadUInt32() + image.GlobalOffset);
if (funcPtr > image.Length)
return (0, 0);
// push ebp; mov ebp, esp; push ebx; and esp, 0FFFFFFF0h; sub esp, 20h; call $+5; pop ebx
bytes = new byte[]
{0x55, 0x89, 0xE5, 0x53, 0x83, 0xE4, 0xF0, 0x83, 0xEC, 0x20, 0xE8, 0x00, 0x00, 0x00, 0x00, 0x5B};
image.Position = loc;
buff = image.ReadBytes(16);
if (!bytes.SequenceEqual(buff))
return (0, 0);
// Extract Metadata pointer
// An 0x838D opcode indicates LEA (no indirection)
image.Position = funcPtr + 0x20;
opcode = image.ReadUInt16();
metadata = image.ReadUInt32() + image.GlobalOffset;
// lea eax, (pCgr - offset)[ebx] (Position + 6 is the opcode lea eax; Position + 8 is the operand)
image.Position += 8;
pCgr = image.MapVATR(image.ReadUInt32() + plt);
if (pCgr > image.Length)
return (0, 0);
// An 8x838B opcode indicates MOV (pointer indirection)
if (opcode == 0x838B) {
image.Position = image.MapVATR(metadata);
metadata = image.ReadUInt32();
// Extract Metadata pointer
// An 0x838D opcode indicates LEA (no indirection)
image.Position = pCgr + 0x20;
var opcode = image.ReadUInt16();
metadata = image.ReadUInt32() + plt;
// An 8x838B opcode indicates MOV (pointer indirection)
if (opcode == 0x838B) {
image.Position = image.MapVATR(metadata);
metadata = image.ReadUInt32();
}
if (opcode != 0x838B && opcode != 0x838D)
return (0, 0);
// Repeat the same logic for extracting the Code pointer
image.Position = pCgr + 0x2A;
opcode = image.ReadUInt16();
code = image.ReadUInt32() + plt;
if (opcode == 0x838B) {
image.Position = image.MapVATR(code);
code = image.ReadUInt32();
}
if (opcode != 0x838B && opcode != 0x838D)
return (0, 0);
return (code, metadata);
}
if (opcode != 0x838B && opcode != 0x838D)
return (0, 0);
// Repeat the same logic for extracting the Code pointer
image.Position = funcPtr + 0x2A;
opcode = image.ReadUInt16();
code = image.ReadUInt32() + image.GlobalOffset;
if (opcode == 0x838B) {
image.Position = image.MapVATR(code);
code = image.ReadUInt32();
}
if (opcode != 0x838B && opcode != 0x838D)
return (0, 0);
return (code, metadata);
return (0, 0);
}
}
}