The objective of this tutorial is to give an overview of the LIEF’s API to parse and manipulate formats
By Romain Thomas - @rh0main
We start by the ELF format. To create an ELF.Binary from a file we just have to give its path to the lief.parse() or lief.ELF.parse() functions
Note
With the Python API, these functions have the same behaviour but in C++, LIEF::Parser::parse() will return a pointer to a LIEF::Binary object whereas LIEF::ELF::Parser::parse() will return a LIEF::ELF::Binary object
import lief
binary = lief.parse("/bin/ls")
Once the ELF file has been parsed, we can access to its Header:
header = binary.header
Change the entry point and the target architecture (ARCH)
header.entrypoint = 0x123
header.machine_type = lief.ELF.ARCH.AARCH64
and then rebuild it:
binary.write("ls.modified")
We can also iterate over binary Sections as follows:
for section in binary.sections:
print(section.name) # section's name
print(section.size) # section's size
print(len(section.content)) # Should match the previous print
To modify the content of the .text section:
text = binary.get_section(".text")
text.content = bytes([0x33] * text.size)
As for the ELF part, we can use the lief.parse() or lief.PE.parse() functions to create a PE.Binary
import lief
binary = lief.parse("C:\\Windows\\explorer.exe")
To access to the different PE headers (DosHeader, Header and OptionalHeader):
print(binary.dos_header)
print(binary.header)
print(binary.optional_header)
One can also access to the imported functions using two methods. The abstract one which will the use the LIEF abstract layer:
for func in binary.imported_functions:
print(func)
To have a better granularity on the location of the imported function in libraries or to access to other fields of the PE imports:
for imported_library in binary.imports:
print("Library name: " + imported_library.name)
for func in imported_library.entries:
if not func.is_ordinal:
print(func.name)
print(func.iat_address)
LIEF enables to modify all the properties of the Import and ImportEntry but to take account of the modification, the Builder must be configured as follow:
builder = lief.PE.Builder(binary)
builder.build_imports(True)
builder.patch_imports(True)
builder.build()
builder.write("result.exe")