Skip to content

davidmagnotti/machofile

BranchesTags
 
 

Repository files navigation

machofile

machofile is a module to parse Mach-O binary files, with a focus on malware analysis and reverse engineering.

Inspired by Ero Carrera's pefile, this module aims to provide a similar capability but for Mach-O binaries instead. Reference material and documentation used to gain the file format knowledge, the basic structures and constant are taken from the resources listed below.

machofile is self-contained. The module has no dependencies; it is endianness independent; and it works on macOS, Windows, and Linux.

While there are other mach-o parsing modules out there, the motivations behind developing this one are:

  • first and foremost, for me this was a great way to deep dive and learn more about the Mach-O format and structures
  • to provide a simple way to parse Mach-O files for analysis
  • to not depend on external modules (e.g. lief, macholib, macho, etc.), since everything is directly extracted from the file and is all in pure python.

Let me know if you try it or find bugs but also... be gentle ;) code will be optimized and more features will be added.

Current Features:

  • Parse Mach-O Header
  • Parse Load Commands
  • Parse File Segments
  • Parse Dylib Commands
  • Parse Dylib List
  • Extract imported function
  • Extract Exported Symbols
  • Hashes: dylib hash, import hash, export hash, symhash
  • Segment entropy calculation
  • Extract Entry point
  • Extract UUID
  • Extract Version Information
  • Parse basic Code Signature information
  • Support for FAT (Universal) Binaries
  • JSON output support (both human-readable and raw formats)

Note: as of now, this has initially been tested against x86, x86_64, arm64, and arm64e Mach-O samples.

Next features to be implemented (in random order):

  • Embedded strings
  • File Attributes
  • flag for suspicious libraries
  • Packer detection
  • ...

Credits

Those are the people that I would like to thank for being the inspiration that led me to write this module:

Usage and example

You can either use it from command line or import it as a module in your python code, and call each function individually to parse only the structures you are interested in. You can install it directly via pip and use it programmatically or from command line, or use it as standalone script

pip install machofile

Module version

It expects to be supplied with either a file path or a data buffer to parse.

import machofile
macho = machofile.UniversalMachO(file_path='/path/to/machobinary')
macho.parse()

If the data buffer is already available, it can be supplied directly with:

import machofile
with open(file_path, 'rb') as f:
    data = f.read()
macho = machofile.UniversalMachO(data=data)
macho.parse()

For detailed usage of the API, check the dedicated API documentation page.

Command Line version

You can use machofile.py also directly as a CLI tool. All CLI features are available from the same file you import as a module.

% python3 machofile.py -h
usage: machofile.py [-h] -f FILE [-j] [--raw] [-a] [-d] [-e] [-ep] [-g] 
                    [-hdr] [-i] [-l] [-seg] [-sig] [-sim] [-u] [-v] [--arch ARCH]

Parse Mach-O file structures.

options:
  -h, --help          show this help message and exit

required arguments:
  -f, --file FILE     Path to the file to be parsed

output format options:
  -j, --json          Output data in JSON format
  --raw               Output raw values in JSON format (use with -j/--json)

data extraction options:
  -a, --all           Print all info about the file
  -d, --dylib         Print Dylib Command Table and Dylib list
  -e, --exports       Print exported symbols
  -ep, --entry-point  Print entry point information
  -g, --general_info  Print general info about the file
  -hdr, --header      Print Mach-O header info
  -i, --imports       Print imported symbols
  -l, --load_cmd_t    Print Load Command Table and Command list
  -seg, --segments    Print File Segments info
  -sig, --signature   Print code signature and entitlements information
  -sim, --similarity  Print similarity hashes
  -u, --uuid          Print UUID
  -v, --version       Print version information

filter options:
  --arch ARCH         Show info for specific architecture only (for Universal binaries)

Example output:

% python3 machofile.py -a -f b4f68a58658ceceb368520dafc35b270272ac27b8890d5b3ff0b968170471e2b

[General File Info]
        Filename:    b4f68a58658ceceb368520dafc35b270272ac27b8890d5b3ff0b968170471e2b
        Filesize:    54240
        MD5:         20ffe440e4f557b9e03855b5da2b3c9c
        SHA1:        1bf61ecad8568a774f9fba726a254a9603d09f33
        SHA256:      b4f68a58658ceceb368520dafc35b270272ac27b8890d5b3ff0b968170471e2b

[Mach-O Header]
        magic:       MH_MAGIC (32-bit), 0xFEEDFACE
        cputype:     Intel i386
        cpusubtype:  X86_ALL
        filetype:    EXECUTE
        ncmds:       13
        sizeofcmds:  1180
        flags:       NOUNDEFS, DYLDLINK, TWOLEVEL

[Load Cmd table]
        {'cmd': 'LC_SEGMENT', 'cmdsize': 56}
        {'cmd': 'LC_SEGMENT', 'cmdsize': 192}
        {'cmd': 'LC_SEGMENT', 'cmdsize': 328}
        {'cmd': 'LC_SEGMENT', 'cmdsize': 192}
        {'cmd': 'LC_SEGMENT', 'cmdsize': 56}
        {'cmd': 'LC_SYMTAB', 'cmdsize': 24}
        {'cmd': 'LC_DYSYMTAB', 'cmdsize': 80}
        {'cmd': 'LC_LOAD_DYLINKER', 'cmdsize': 28}
        {'cmd': 'LC_UUID', 'cmdsize': 24}
        {'cmd': 'LC_UNIXTHREAD', 'cmdsize': 80}
        {'cmd': 'LC_LOAD_DYLIB', 'cmdsize': 52}
        {'cmd': 'LC_LOAD_DYLIB', 'cmdsize': 52}
        {'cmd': 'LC_CODE_SIGNATURE', 'cmdsize': 16}

[Load Commands]
        LC_CODE_SIGNATURE
        LC_DYSYMTAB
        LC_LOAD_DYLIB
        LC_LOAD_DYLINKER
        LC_SEGMENT
        LC_SYMTAB
        LC_UNIXTHREAD
        LC_UUID

[File Segments]
        SEGNAME    VADDR VSIZE OFFSET SIZE  MAX_VM_PROTECTION INITIAL_VM_PROTECTION NSECTS FLAGS ENTROPY            
        ------------------------------------------------------------------------------------------------------------
        __PAGEZERO 0     4096  0      0     0                 0                     0      0     0.0                
        __TEXT     4096  28672 0      28672 7                 5                     2      0     5.080680410706916  
        __DATA     32768 4096  28672  4096  7                 3                     4      0     0.1261649636134924 
        __IMPORT   36864 4096  32768  4096  7                 7                     2      0     0.21493796627555234
        __LINKEDIT 40960 20480 36864  17376 7                 1                     0      0     6.637864516225949  

[Dylib Commands]
        DYLIB_NAME_OFFSET DYLIB_TIMESTAMP DYLIB_CURRENT_VERSION DYLIB_COMPAT_VERSION DYLIB_NAME                   
        ----------------------------------------------------------------------------------------------------------
        24                2               65536                 65536                b'/usr/lib/libgcc_s.1.dylib' 
        24                2               7274759               65536                b'/usr/lib/libSystem.B.dylib'

[Dylib Names]
        b'/usr/lib/libgcc_s.1.dylib'
        b'/usr/lib/libSystem.B.dylib'

[UUID]
        d691c242-da49-1081-50d5-4f8991924b06

[Entry Point]
        type:        LC_UNIXTHREAD
        entry_address:9200
        thread_data_size:72

[Version Information]
        No version information found

[Code Signature]
        signed:      True
        signing_status:Apple signed
        certificates_info:
            count:       3
            certificates:
              index:       0
              size:        4815
              subject:     Contains: Developer ID Certification Authority
              issuer:      Unable to parse
              is_apple_cert:True
              type:        Developer ID Certification Authority

              index:       1
              size:        1215
              subject:     Contains: Apple Root CA
              issuer:      Unable to parse
              is_apple_cert:True
              type:        Apple Root CA

              index:       2
              size:        1385
              subject:     Contains: Developer ID Application:
              issuer:      Unable to parse
              is_apple_cert:False
              type:        Developer ID Application Certificate
        entitlements_info:
            count:       0
            entitlements:
        code_directory:
            version:     131328
            flags:       0
            hash_offset: 144
            identifier_offset:48
            special_slots:3
            signing_flags:
                None
            code_slots:  11
            hash_size:   44640
            hash_type:   335609868
            hash_algorithm:Unknown (335609868)
            identifier:  onmac.unspecified.installer

[Imported Functions]
        /usr/lib/libSystem.B.dylib:
                __NSGetExecutablePath
                ___stderrp
                _dlerror
                _dlopen
                _dlsym
                _exit
                _fclose
                _fopen
                _fprintf
                _fputs$UNIX2003
                _free
                _fwrite$UNIX2003
                _getenv
                _getpid
                _getpwnam
                _lstat
                _mbstowcs
                _memcpy
                _memset
                _setenv$UNIX2003
                _setlocale
                _snprintf
                _stat
                _strchr
                _strdup
                _strlen
                _unsetenv$UNIX2003

[Exported Symbols]
        <unknown>:
                _NXArgc
                _NXArgv
                ___progname
                _environ
                _main
                start

[Similarity Hashes]
        dylib_hash:  0556bed5dc31bddaee73f3234b3c577b
        import_hash: 0bae89995ad3900987c49c0bea1d17fe
        export_hash: 824e359e3d0ad7283d0982bd5da2e8fd
        symhash:     15e6c1aeba01be1404901f7152213779

JSON Output

machofile supports JSON output for programmatic consumption of the parsed data. The JSON output comes in two formats:

Human-Readable JSON (Default)

The default JSON output provides human-readable values with proper formatting applied:

% python3 machofile.py -j -hdr -f dec750b9d596b14aeab1ed6f6d6d370022443ceceb127e7d2468b903c2d9477a 
{
  "header": {
    "x86_64": {
      "magic": "MH_MAGIC_64 (64-bit), 0xFEEDFACF",
      "cputype": "x86_64",
      "cpusubtype": "x86_ALL",
      "filetype": "EXECUTE",
      "ncmds": 41,
      "sizeofcmds": 5024,
      "flags": "NOUNDEFS, DYLDLINK, TWOLEVEL, BINDS_TO_WEAK, PIE"
    },
    "arm64": {
      "magic": "MH_MAGIC_64 (64-bit), 0xFEEDFACF",
      "cputype": "ARM 64-bit",
      "cpusubtype": "ARM_ALL",
      "filetype": "EXECUTE",
      "ncmds": 41,
      "sizeofcmds": 5104,
      "flags": "NOUNDEFS, DYLDLINK, TWOLEVEL, BINDS_TO_WEAK, PIE"
    }
  },
  "architectures": [
    "x86_64",
    "arm64"
  ]
}

Raw JSON Output

For applications that need to process raw numeric values, use the --raw flag:

% python3 machofile.py -j --raw -hdr -f dec750b9d596b14aeab1ed6f6d6d370022443ceceb127e7d2468b903c2d9477a
{
  "header": {
    "x86_64": {
      "magic": 4277009103,
      "cputype": 16777223,
      "cpusubtype": 3,
      "filetype": 2,
      "ncmds": 41,
      "sizeofcmds": 5024,
      "flags": 2162821
    },
    "arm64": {
      "magic": 4277009103,
      "cputype": 16777228,
      "cpusubtype": 0,
      "filetype": 2,
      "ncmds": 41,
      "sizeofcmds": 5104,
      "flags": 2162821
    }
  },
  "architectures": [
    "x86_64",
    "arm64"
  ]
}

JSON Output Options

  • -j, --json: Output data in JSON format (human-readable by default)
  • --raw: Output raw numeric values instead of formatted strings (must be used with -j)

JSON output supports all the same analysis options as the standard output (-a, -hd, -l, -sg, etc.) and works with both single-architecture and Universal (FAT) binaries.

Reference/Documentation links:

About

machofile is a module to parse Mach-O binary files

threatresearch.ch

Resources

Readme

License

MIT license
Activity

Stars

0 stars

Watchers

0 watching

Forks

0 forks
Report repository

Releases

No releases published

Packages

No packages published

Languages

  • Python 100.0%