#!/usr/bin/env python3
# Wireshark - Network traffic analyzer
# By Gerald Combs <gerald@wireshark.org>
# Copyright 1998 Gerald Combs
#
# SPDX-License-Identifier: GPL-2.0-or-later

import os
import re
import subprocess
import argparse
import signal

# Look for dissector symbols that could/should be static.
# This will not run on Windows, unless/until we check the platform
# and use (I think) dumpbin.exe
#
# N.B. Will report false positives if symbols are extern'd rather than
# declared in a header file.

# Try to exit soon after Ctrl-C is pressed.
should_exit = False

def signal_handler(sig, frame):
    global should_exit
    should_exit = True
    print('You pressed Ctrl+C - exiting')

signal.signal(signal.SIGINT, signal_handler)

# Allow this as a default build folder name...
build_folder = os.getcwd() + '-build'


# Record which symbols are referred to (by a set of files).
class CalledSymbols:
    def __init__(self):
        self.referred = set()

    def addCalls(self, file):
        if should_exit:
            exit(1)

        # Make sure that file is built.
        last_dir = os.path.split(os.path.dirname(file))[-1]
        if file.find('ui/cli') != -1:
            # A tshark target-only file
            object_file = os.path.join(build_folder, 'CMakeFiles', ('tshark' + '.dir'), file + '.o')
        elif file.find('ui/qt') != -1:
            object_file = os.path.join(build_folder, os.path.dirname(file), 'CMakeFiles', ('qtui' + '.dir'), os.path.basename(file) + '.o')
        else:
            if file.endswith('dissectors.c'):
                object_file = os.path.join(build_folder, os.path.dirname(file), 'CMakeFiles', 'dissector-registration' + '.dir', os.path.basename(file) + '.o')
            else:
                object_file = os.path.join(build_folder, os.path.dirname(file), 'CMakeFiles', last_dir + '.dir', os.path.basename(file) + '.o')
        if not os.path.exists(object_file):
            # Not built for whatever reason..
            #print('Warning -', object_file, 'does not exist')
            return

        # Run command to check symbols.
        command = ['nm', object_file]
        for f in subprocess.check_output(command).splitlines():
            line = str(f)[2:-1]
            # Lines might, or might not, have an address before letter and symbol.
            p1 = re.compile(r'[0-9a-f]* ([a-zA-Z]) (.*)')
            p2 = re.compile(r'[ ]* ([a-zA-Z]) (.*)')

            m = p1.match(line)
            if not m:
                m = p2.match(line)
            if m:
                letter = m.group(1)
                function_name = m.group(2)

                # Only interested in undefined/external references to symbols.
                if letter == 'U':
                    self.referred.add(function_name)



# Record which symbols are defined in a single dissector file.
class DefinedSymbols:
    def __init__(self, file):
        self.filename = file
        self.global_symbols = {}       # map from defined symbol -> whole output-line
        self.header_file_contents = None
        self.from_generated_file = isGeneratedFile(file)

        # Make sure that file is built.
        if self.filename.startswith('epan'):
            object_file = os.path.join(build_folder, 'epan', 'dissectors', 'CMakeFiles', 'dissectors.dir', os.path.basename(file) + '.o')
        elif self.filename.startswith('plugins'):
            plugin_base_dir = os.path.dirname(file)
            plugin_base_name = os.path.basename(plugin_base_dir)
            object_file = os.path.join(build_folder, plugin_base_dir, 'CMakeFiles', plugin_base_name + '.dir', os.path.basename(file) + '.o')
        else:
            #print("Warning - can't determine object file for ", self.filename)
            return
        if not os.path.exists(object_file):
            #print('Warning -', object_file, 'does not exist')
            return

        # Get header file contents if available
        header_file= file.replace('.c', '.h')
        try:
            f = open(header_file, 'r')
            self.header_file_contents = f.read()
        except IOError:
            pass

        # Run command to see which symbols are defined
        command = ['nm', object_file]
        for f in subprocess.check_output(command).splitlines():
            # Line consists of whitespace, [address], letter, symbolName
            line = str(f)[2:-1]
            p = re.compile(r'[0-9a-f]* ([a-zA-Z]) (.*)')
            m = p.match(line)
            if m:
                letter = m.group(1)
                function_name = m.group(2)
                # Globally-defined symbols. Would be 't' or 'd' if already static..
                if letter in 'TD':
                    self.addDefinedSymbol(function_name, line)

    def addDefinedSymbol(self, symbol, line):
        self.global_symbols[symbol] = line

    def isSymbolInContents(self, contents, symbol):
        if not contents:
            return False
        # Check that string appears
        idx = contents.find(symbol)
        if idx == -1:
            return False
        else:
            # Look for in context.  In particular don't want to match if there is
            # longer symbol with symbol as a prefix..
            p = re.compile(r'[\s\*\()]' + symbol + r'[\(\s\[;]+', re.MULTILINE)
            m = p.search(contents, re.MULTILINE)
            return m is not None

    # Check if a given symbol is mentioned in headers
    def mentionedInHeaders(self, symbol):
        if self.isSymbolInContents(self.header_file_contents, symbol):
            return True

        # Also check some of the 'common' header files that don't match the dissector file name.
        # TODO: could cache the contents of these files?
        common_mismatched_headers = [ os.path.join('epan', 'dissectors', 'packet-ncp-int.h'),
                                      os.path.join('epan', 'dissectors', 'packet-mq.h'),
                                      os.path.join('epan', 'dissectors', 'packet-ip.h'),
                                      os.path.join('epan', 'dissectors', 'packet-gsm_a_common.h'),
                                      os.path.join('epan', 'dissectors', 'packet-epl.h'),
                                      os.path.join('epan', 'dissectors', 'packet-bluetooth.h'),
                                      os.path.join('epan', 'dissectors', 'packet-dcerpc.h'),
                                      os.path.join('epan', 'ip_opts.h'),
                                      os.path.join('epan', 'eap.h')]
        for hf in common_mismatched_headers:
            try:
                f = open(hf)
                contents = f.read()
                if self.isSymbolInContents(contents, symbol):
                    return True
            except EnvironmentError:
                pass

        return False

    def checkIfSymbolsAreCalled(self, called_symbols):
        global issues_found
        for f in self.global_symbols:
            if f not in called_symbols:
                mentioned_in_header = self.mentionedInHeaders(f)
                fun = self.global_symbols[f]
                print(self.filename, '' if not self.from_generated_file else '(GENERATED)',
                      '(' + fun + ')',
                      'is not referred to so could be static?', '(declared in header but not referred to)' if mentioned_in_header else '')
                issues_found += 1



# Helper functions.

def isDissectorFile(filename):
    # Ignoring usb.c & errno.c
    p = re.compile(r'(packet|file)-.*\.c')
    return p.match(filename)

# Test for whether the given dissector file was automatically generated.
def isGeneratedFile(filename):
    # Check file exists - e.g. may have been deleted in a recent commit.
    if not os.path.exists(filename):
        return False

    if not filename.endswith('.c'):
        return False

    # Open file
    f_read = open(os.path.join(filename), 'r')
    lines_tested = 0
    for line in f_read:
        # The comment to say that its generated is near the top, so give up once
        # get a few lines down.
        if lines_tested > 10:
            f_read.close()
            return False
        if (line.find('Generated automatically') != -1 or
            line.find('Autogenerated from') != -1 or
            line.find('is autogenerated') != -1 or
            line.find('automatically generated by Pidl') != -1 or
            line.find('Created by: The Qt Meta Object Compiler') != -1 or
            line.find('This file was generated') != -1 or
            line.find('This filter was automatically generated') != -1):

            f_read.close()
            return True
        lines_tested = lines_tested + 1

    # OK, looks like a hand-written file!
    f_read.close()
    return False


def findDissectorFilesInFolder(folder, include_generated):
    # Look at files in sorted order, to give some idea of how far through is.
    tmp_files = []

    for f in sorted(os.listdir(folder)):
        if should_exit:
            return
        if isDissectorFile(f):
            if include_generated or not isGeneratedFile(os.path.join('epan', 'dissectors', f)):
                filename = os.path.join(folder, f)
                tmp_files.append(filename)
    return tmp_files

def findFilesInFolder(folder):
    # Look at files in sorted order, to give some idea of how far through is.
    tmp_files = []

    for f in sorted(os.listdir(folder)):
        if should_exit:
            return
        if f.endswith('.c') or f.endswith('.cpp'):
            filename = os.path.join(folder, f)
            tmp_files.append(filename)
    return tmp_files


def is_dissector_file(filename):
    p = re.compile(r'.*(packet|file)-.*\.c')
    return p.match(filename)




#################################################################
# Main logic.

# command-line args.  Controls which dissector files should be checked.
# If no args given, will just scan epan/dissectors folder.
parser = argparse.ArgumentParser(description='Check calls in dissectors')
parser.add_argument('--build-folder', action='store', default='',
                    help='build folder', required=False)
parser.add_argument('--file', action='append',
                    help='specify individual dissector file to test')
parser.add_argument('--commits', action='store',
                    help='last N commits to check')
parser.add_argument('--open', action='store_true',
                    help='check open files')

args = parser.parse_args()

issues_found = 0

# Get files from wherever command-line args indicate.
files = []

if args.build_folder:
    build_folder = args.build_folder

if args.file:
    # Add specified file(s)
    for f in args.file:
        if not os.path.isfile(f) and not f.startswith('epan'):
            f = os.path.join('epan', 'dissectors', f)
        if not os.path.isfile(f):
            print('Chosen file', f, 'does not exist.')
            exit(1)
        else:
            files.append(f)
elif args.commits:
    # Get files affected by specified number of commits.
    command = ['git', 'diff', '--name-only', 'HEAD~' + args.commits]
    files = [f.decode('utf-8')
             for f in subprocess.check_output(command).splitlines()]
    # Will examine dissector files only
    files = list(filter(lambda f : is_dissector_file(f), files))
elif args.open:
    # Unstaged changes.
    command = ['git', 'diff', '--name-only']
    files = [f.decode('utf-8')
             for f in subprocess.check_output(command).splitlines()]
    # Only interested in dissector files.
    files = list(filter(lambda f : is_dissector_file(f), files))
    # Staged changes.
    command = ['git', 'diff', '--staged', '--name-only']
    files_staged = [f.decode('utf-8')
                    for f in subprocess.check_output(command).splitlines()]
    # Only interested in dissector files.
    files_staged = list(filter(lambda f : is_dissector_file(f), files_staged))
    for f in files:
        files.append(f)
    for f in files_staged:
        if f not in files:
            files.append(f)
else:
    # Find all dissector files from folder.
    files = findDissectorFilesInFolder(os.path.join('epan', 'dissectors'),
                                       include_generated=True)


# If scanning a subset of files, list them here.
print('Examining:')
if args.file or args.commits or args.open:
    if files:
        print(' '.join(files), '\n')
    else:
        print('No files to check.\n')
else:
    print('All dissector modules\n')


if not os.path.isdir(build_folder):
    print('Build directory not valid', build_folder, '- please set with --build-folder')
    exit(1)


# Get the set of called functions and referred-to data.
called = CalledSymbols()
for d in findDissectorFilesInFolder(os.path.join('epan', 'dissectors'), include_generated=True):
    called.addCalls(d)
called.addCalls(os.path.join('epan', 'dissectors', 'dissectors.c'))
# Also check calls from GUI code
for d in findFilesInFolder('ui'):
    called.addCalls(d)
for d in findFilesInFolder(os.path.join('ui', 'qt')):
    called.addCalls(d)
# These are from tshark..
for d in findFilesInFolder(os.path.join('ui', 'cli')):
    called.addCalls(d)


# Now check identified dissector files.
for f in files:
    if should_exit:
        exit(1)
    # Are these symbols called - or could they be deleted or static????
    DefinedSymbols(f).checkIfSymbolsAreCalled(called.referred)

# Show summary.
print(issues_found, 'issues found')