checklibs.py

#!/usr/bin/env python
#
# checklibs.py
#
# Check Mach-O dependencies.
#
# See http://www.entropy.ch/blog/Developer/2011/03/05/2011-Update-to-checklibs-Script-for-dynamic-library-dependencies.html
#
# Written by Marc Liyanage <http://www.entropy.ch>
#
#

import subprocess, sys, re, os.path, optparse, collections
from pprint import pprint


class MachOFile:

    def __init__(self, image_path, arch, parent = None):
        self.image_path = image_path
        self._dependencies = []
        self._cache = dict(paths = {}, order = [])
        self.arch = arch
        self.parent = parent
        self.header_info = {}
        self.load_info()
        self.add_to_cache()
        
    def load_info(self):
        if not self.image_path.exists():
            return
        self.load_header()
        self.load_rpaths()

    def load_header(self):
        # Get the mach-o header info, we're interested in the file type (executable, dylib)
        cmd = 'otool -arch {0} -h "{1}"'
        output = self.shell(cmd, [self.arch, self.image_path.resolved_path], fatal = True)
        if not output:
            print >> sys.stderr, 'Unable to load mach header for {0} ({1}), architecture mismatch? Use --arch option to pick architecture'.format(self.image_path.resolved_path, self.arch)
            exit()
        (keys, values) = output.splitlines()[2:]
        self.header_info = dict(zip(keys.split(), values.split()))

    def load_rpaths(self):
        output = self.shell('otool -arch {0} -l "{1}"', [self.arch, self.image_path.resolved_path], fatal = True)
        load_commands = re.split('Load command (\d+)', output)[1:] # skip file name on first line
        self._rpaths = []
        load_commands = collections.deque(load_commands)
        while load_commands:
            load_commands.popleft() # command index
            command = load_commands.popleft().strip().splitlines()
            if command[0].find('LC_RPATH') == -1:
                continue
            
            path = re.findall('path (.+) \(offset \d+\)$', command[2])[0]
            image_path = self.image_path_for_recorded_path(path)
            image_path.rpath_source = self
            self._rpaths.append(image_path)

    def ancestors(self):
        ancestors = []
        parent = self.parent
        while parent:
            ancestors.append(parent)
            parent = parent.parent
        
        return ancestors

    def self_and_ancestors(self):
        return [self] + self.ancestors()
    
    def rpaths(self):
        return self._rpaths
    
    def all_rpaths(self):
        rpaths = []
        for image in self.self_and_ancestors():
            rpaths.extend(image.rpaths())
        return rpaths
    
    def root(self):
        if not self.parent:
            return self
        return self.ancestors()[-1]
    
    def executable_path(self):
        root = self.root()
        if root.is_executable():
            return root.image_path
        return None

    def filetype(self):
        return long(self.header_info.get('filetype', 0))
        
    def is_dylib(self):
        return self.filetype() == MachOFile.MH_DYLIB

    def is_executable(self):
        return self.filetype() == MachOFile.MH_EXECUTE
        
    def all_dependencies(self):
        self.walk_dependencies()
        return self.cache()['order']
    
    def walk_dependencies(self, known = {}):
        if known.get(self.image_path.resolved_path):
            return
        
        known[self.image_path.resolved_path] = self
        
        for item in self.dependencies():
            item.walk_dependencies(known)
        
    def dependencies(self):
        if not self.image_path.exists():
            return []

        if self._dependencies:
            return self._dependencies

        output = self.shell('otool -arch {0} -L "{1}"', [self.arch, self.image_path.resolved_path], fatal = True)
        output = [line.strip() for line in output.splitlines()]
        del(output[0])
        if self.is_dylib():
            del(output[0]) # In the case of dylibs, the first line is the id line

        self._dependencies = []
        for line in output:
            match = re.match('^(.+)\s+(\(.+)\)$', line)
            if not match:
                continue
            recorded_path = match.group(1)
            image_path = self.image_path_for_recorded_path(recorded_path)
            image = self.lookup_or_make_item(image_path)
            self._dependencies.append(image)
            
        return self._dependencies

    # The root item holds the cache, all lower-level requests bubble up the parent chain
    def cache(self):
        if self.parent:
            return self.parent.cache()
        return self._cache
    
    def add_to_cache(self):
        cache = self.cache()
        cache['paths'][self.image_path.resolved_path] = self
        cache['order'].append(self)
        
    def cached_item_for_path(self, path):
        if not path:
            return None
        return self.cache()['paths'].get(path)
    
    def lookup_or_make_item(self, image_path):
        image = self.cached_item_for_path(image_path.resolved_path)
        if not image: # cache miss
            image = MachOFile(image_path, self.arch, parent = self)
        return image

    def image_path_for_recorded_path(self, recorded_path):
        path = ImagePath(None, recorded_path)

        # handle @executable_path       
        if recorded_path.startswith(ImagePath.EXECUTABLE_PATH_TOKEN):
            executable_image_path = self.executable_path()
            if executable_image_path:
                path.resolved_path = os.path.normpath(recorded_path.replace(ImagePath.EXECUTABLE_PATH_TOKEN, os.path.dirname(executable_image_path.resolved_path)))

        # handle @loader_path
        elif recorded_path.startswith(ImagePath.LOADER_PATH_TOKEN):
            path.resolved_path = os.path.normpath(recorded_path.replace(ImagePath.LOADER_PATH_TOKEN, os.path.dirname(self.image_path.resolved_path)))

        # handle @rpath
        elif recorded_path.startswith(ImagePath.RPATH_TOKEN):
            for rpath in self.all_rpaths():
                resolved_path = os.path.normpath(recorded_path.replace(ImagePath.RPATH_TOKEN, rpath.resolved_path))
                if os.path.exists(resolved_path):
                    path.resolved_path = resolved_path
                    path.rpath_source = rpath.rpath_source
                    break

        # handle absolute path
        elif recorded_path.startswith('/'):
            path.resolved_path = recorded_path

        return path

    def __repr__(self):
        return str(self.image_path)
    
    def dump(self):
        print self.image_path
        for dependency in self.dependencies():
            print '\t{0}'.format(dependency)
    
    @staticmethod
    def shell(cmd_format, args, fatal = False):
        cmd = cmd_format.format(*args)
        popen = subprocess.Popen(cmd, shell = True, stdout = subprocess.PIPE)
        output = popen.communicate()[0]
        if popen.returncode and fatal:
            print >> sys.stderr, 'Nonzero exit status for shell command "{0}"'.format(cmd)
            sys.exit(1)

        return output

    @classmethod
    def architectures_for_image_at_path(cls, path):
        output = cls.shell('file "{}"', [path])
        file_architectures = re.findall(r' executable (\w+)', output)
        ordering = 'x86_64 i386'.split()
        file_architectures = sorted(file_architectures, lambda a, b: cmp(ordering.index(a), ordering.index(b)))
        return file_architectures

    MH_EXECUTE = 0x2
    MH_DYLIB = 0x6
    MH_BUNDLE = 0x8
    

# ANSI terminal coloring sequences
class Color:
    HEADER = '\033[95m'
    BLUE = '\033[94m'
    GREEN = '\033[92m'
    RED = '\033[91m'
    ENDC = '\033[0m'
    
    @staticmethod
    def red(string):
        return Color.wrap(string, Color.RED)
    
    @staticmethod
    def blue(string):
        return Color.wrap(string, Color.BLUE)
    
    @staticmethod
    def wrap(string, color):
        return Color.HEADER + color + string + Color.ENDC


# This class holds path information for a mach-0 image file. It holds the path as it was recorded
# in the loading binary as well as the effective, resolved file system path.
# The former can contain @-replacement tokens.
# In the case where the recorded path contains an @rpath token that was resolved successfully, we also
# capture the path of the binary that supplied the rpath value that was used.
# That path itself can contain replacement tokens such as @loader_path.
class ImagePath:

    def __init__(self, resolved_path, recorded_path = None):
        self.recorded_path = recorded_path
        self.resolved_path = resolved_path
        self.rpath_source = None
        
    def __repr__(self):
        description = None
        
        if self.resolved_equals_recorded() or self.recorded_path == None:
            description = self.resolved_path
        else:
            description = '{0} ({1})'.format(self.resolved_path, self.recorded_path)
        
        if (not self.is_system_location()) and (not self.uses_dyld_token()):
            description = Color.blue(description)
        
        if self.rpath_source:
            description += ' (rpath source: {0})'.format(self.rpath_source.image_path.resolved_path)
        
        if not self.exists():
            description += Color.red(' (missing)')
        
        return description
    
    def exists(self):
        return self.resolved_path and os.path.exists(self.resolved_path)
    
    def resolved_equals_recorded(self):
        return self.resolved_path and self.recorded_path and self.resolved_path == self.recorded_path
    
    def uses_dyld_token(self):
        return self.recorded_path and self.recorded_path.startswith('@')
    
    def is_system_location(self):
        system_prefixes = ['/System/Library', '/usr/lib']
        for prefix in system_prefixes:
            if self.resolved_path and self.resolved_path.startswith(prefix):
                return True

    EXECUTABLE_PATH_TOKEN = '@executable_path'
    LOADER_PATH_TOKEN = '@loader_path'
    RPATH_TOKEN = '@rpath'


# Command line driver
parser = optparse.OptionParser(usage = "Usage: %prog [options] path_to_mach_o_file")
parser.add_option("--arch", dest = "arch", help = "architecture", metavar = "ARCH")
parser.add_option("--all", dest = "include_system_libraries", help = "Include system frameworks and libraries", action="store_true")
(options, args) = parser.parse_args()

if len(args) < 1:
    parser.print_help()
    sys.exit(1)

archs = MachOFile.architectures_for_image_at_path(args[0])
if archs and not options.arch:
    print >> sys.stderr, 'Analyzing architecture {}, override with --arch if needed'.format(archs[0])
    options.arch = archs[0]

toplevel_image = MachOFile(ImagePath(args[0]), options.arch)

for dependency in toplevel_image.all_dependencies():
    if dependency.image_path.exists() and (not options.include_system_libraries) and dependency.image_path.is_system_location():
        continue

    dependency.dump()
    print