strongarm is a full-featured, cross-platform ARM64 Mach-O analysis library.
strongarm is production-ready and is used throughout DataTheorem's iOS static analyzer stack.
This repo contains multiple tools to explore strongarm and the API. In the scripts folder,
several popular Mach-O analysis tools have been reimplemented in strongarm, to demonstrate real API usage.
As strongarm is cross-platform, all of these tools are as well:
strongarm-cli: Static analysis REPL (try me!)class-dump: Dump the Objective-C class information from a Mach-O with Objective-C declaration syntaxinsert_dylib: Add a load command to a Mach-Odsc_symbolicate: Given a dyld_shared_cache, generate a symbol map from the embedded system imagesnm: List the symbol table of a Mach-Olipo: Thin or fatten Mach-O files and sliceshexdump: Output the hex content of a byte range in a filestrings: Output the C-strings in a Mach-Odump_entitlements: Print the code-signing informationbitcode_retriever: Extract the XAR archive containing LLVM bitcode from a Mach-O
strongarm is supported on macOS and Linux.
pip install strongarm-ios
To setup a local environment:
git clone ...
cd strongarm
python -m venv .venv
source .venv/bin/activate
pip install -U pip setuptools wheel 'pip-tools<7.0.0'
pip-sync requirements.txt requirements-dev.txt
If you modify requirements.in or requirements-dev.in:
pip-compile requirements.in
pip-compile requirements-dev.in
pip-sync requirements.txt requirements-dev.txt
git add requirements-dev.in requirements-dev.txt
- Access and cross-reference Mach-O info via an API
- Dataflow analysis
- Function-boundary detection
- Metadata (architecture, endianness, etc)
- Load commands
- Symbol tables
- String tables
- Code signature
- Dyld info
- Objective-C info (classes, categories, protocols, methods, ivars, etc)
- Cross-references (xrefs) of code and strings
- Function boundary detection & disassembly
- Track constant data movement in assembly
- Dyld bound symbols & implementation stubs
- Parse constant NSStrings and C strings
- Basic block analysis
- Load command insertion
- Write Mach-O structures
- Byte-edit binaries
Pass an input file to MachoParser, which will read a Mach-O or FAT and provide access to individual MachoBinary slices.
import pathlib
from strongarm.macho import MachoParser, MachoBinary
# Load an input file
parser = MachoParser(pathlib.Path("~/Documents/MyApp.app/MyApp"))
# Read the ARM64 slice and perform some operations
binary: MachoBinary = parser.get_arm64_slice()
print(binary.get_entitlements().decode())
print(hex(binary.section_with_name("__text", "__TEXT").address))Some APIs which require more memory or cross-referencing are available through MachoAnalyzer
from pathlib import Path
from strongarm.macho import MachoParser, MachoBinary, MachoAnalyzer
macho_parser = MachoParser(Path("~/Documents/MyApp.app/MyApp"))
binary: MachoBinary = macho_parser.get_arm64_slice()
# A MachoAnalyzer wraps a binary and allows deeper analysis
analyzer = MachoAnalyzer.get_analyzer(binary)
# Find all calls to -[UIAlertView init] in the binary
print(analyzer.objc_calls_to(["_OBJC_CLASS_$_UIAlertView"], ["init"], requires_class_and_sel_found=False))
# Print some interesting info
print(analyzer.imported_symbol_names_to_pointers) # All the dynamically linked symbols which will be bound at runtime
print(analyzer.exported_symbol_names_to_pointers) # All the symbols which this binary defines and exports
print(analyzer.get_functions()) # Entry-point list of the binary. Each of these can be wrapped in an ObjcFunctionAnalyzer
print(analyzer.strings()) # __cstring segment
print(analyzer.get_imps_for_sel("viewDidLoad")) # Convenience accessor for an ObjcFunctionAnalyzer
# Print the Objective-C class information
for objc_cls in analyzer.objc_classes():
print(objc_cls.name)
for objc_ivar in objc_cls.ivars:
print(f"\tivar: {objc_ivar.name}")
for objc_sel in objc_cls.selectors:
print(f"\tmethod: {objc_sel.name} @ {hex(objc_sel.implementation)}")Once you have a handle to a FunctionAnalyzer, representing a source code function, you can analyze the code:
from pathlib import Path
from strongarm.macho import MachoParser, MachoBinary, MachoAnalyzer
from strongarm.objc import ObjcFunctionAnalyzer
macho_parser = MachoParser(Path("~/Documents/MyApp.app/MyApp"))
binary: MachoBinary = macho_parser.get_arm64_slice()
analyzer = MachoAnalyzer.get_analyzer(binary)
function_analyzer = ObjcFunctionAnalyzer.get_function_analyzer_for_signature(binary, "ViewController", "viewDidLoad")
print(function_analyzer.basic_blocks) # Find the basic block boundaries
# Print some interesting info about Objective-C method calls in the function
for instr in function_analyzer.instructions:
if not instr.is_msgSend_call:
continue
# In an Objective-C message send, x0 stores the receiver and x1 stores the selector being messaged.
classref = function_analyzer.get_register_contents_at_instruction("x0", instr)
selref = function_analyzer.get_register_contents_at_instruction("x1", instr)
class_name = analyzer.class_name_for_class_pointer(classref.value)
selector = analyzer.selector_for_selref(selref.value).name
# Prints "0x100000000: _objc_msgSend(_OBJC_CLASS_$_UIView, @selector(alloc));"
print(f"{hex(instr.address)}: {instr.symbol}({class_name}, @selector({selector}));")You can also modify Mach-O's by overwriting structures or inserting load commands:
from pathlib import Path
from strongarm.macho import MachoParser, MachoBinary
from strongarm.macho.macho_definitions import MachoSymtabCommand
macho_parser = MachoParser(Path("~/Documents/MyApp.app/MyApp"))
# Overwrite a structure
binary: MachoBinary = macho_parser.get_arm64_slice()
new_symbol_table = MachoSymtabCommand()
new_symbol_table.nsyms = 0
modified_binary = binary.write_struct(new_symbol_table, binary.symtab.address, virtual=True)
# Add a load command
modified_binary = modified_binary.insert_load_dylib_cmd("/System/Frameworks/UIKit.framework/UIKit")
# Write the modified binary to a file
MachoBinary.write_binary(Path(__file__).parent / "modified_binary")MachoBinary provides several functions to faciliate binary modifications.
As modifying a MachoBinary may invalidate its public attributes, these APIs return a new MachoBinary object,
which is re-parsed with the edits.
# Write raw bytes or Mach-O structures to a binary
MachoBinary.write_bytes(self, data: bytes, address: int, virtual=False) -> MachoBinary
MachoBinary.write_struct(self, struct: Structure, address: int, virtual=False) -> MachoBinary
# Insert a load command
MachoBinary.insert_load_dylib_cmd(dylib_path: str) -> MachoBinary
# Flush a modified slice to a thin Mach-O file, or a list of slices to a FAT Mach-O file:
MachoBinary.write_binary(self, path: pathlib.Path) -> None
@staticmethod
MachoBinary.write_fat(slices: List[MachoBinary], path: pathlib.Path) -> NoneTo make several modifications to a MachoBinary while triggering only one extra parse, use a MachoBinaryWriter:
from pathlib import Path
from strongarm.macho import MachoParser, MachoBinary
from ctypes import c_uint64, sizeof
from strongarm.macho.macho_binary_writer import MachoBinaryWriter
macho_parser = MachoParser(Path("~/Documents/MyApp.app/MyApp"))
binary: MachoBinary = macho_parser.get_arm64_slice()
# Initialise a batch binary writer
writer = MachoBinaryWriter(binary)
# Make a series of changes to the binary
with writer:
for i in range(5):
writer.write_word(word=c_uint64(0xdeadbeef), address=0x1000 + (i * sizeof(c_uint64)), virtual=False)
# `writer.modified_binary` contains the re-parsed binary containing the provided changes
# Persist the modified binary to disk
writer.modified_binary.write_binary(Path(__file__) / "modified_binary")AGPL license
React
Typescript
Django
Laravel
Facebook
Microsoft
Google
Alibaba
D3
Tencent