#!/usr/bin/python3

"""

Check debug symbols are present in shared object and can identify

code.

It starts scanning from a directory and recursively scans all ELF

files found in it for various symbols to ensure all debuginfo is

present and nothing has been stripped.

Usage:

./check-debug-symbols /path/of/dir/to/scan/

Example:

./check-debug-symbols /usr/lib64

"""

# This technique was explained to me by Mark Wielaard (mjw).

import collections

import os

import re

import subprocess

import sys

ScanResult = collections.namedtuple('ScanResult',

                                    'file_name debug_info debug_abbrev file_symbols gnu_debuglink')

def scan_file(file):

    "Scan the provided file and return a ScanResult containing results of the scan."

    # Test for .debug_* sections in the shared object. This is the  main test.

    # Stripped objects will not contain these.

    readelf_S_result = subprocess.run(['eu-readelf', '-S', file],

                                      stdout=subprocess.PIPE, encoding='utf-8', check=True)

    has_debug_info = any(line for line in readelf_S_result.stdout.split('\n') if '] .debug_info' in line)

    has_debug_abbrev = any(line for line in readelf_S_result.stdout.split('\n') if '] .debug_abbrev' in line)

    # Test FILE symbols. These will most likely be removed by anyting that

    # manipulates symbol tables because it's generally useless. So a nice test

    # that nothing has messed with symbols.

    def contains_file_symbols(line):

        parts = line.split()

        if len(parts) < 8:

            return False

        return \

            parts[2] == '0' and parts[3] == 'FILE' and parts[4] == 'LOCAL' and parts[5] == 'DEFAULT' and \

            parts[6] == 'ABS' and re.match(r'((.*/)?[-_a-zA-Z0-9]+\.(c|cc|cpp|cxx))?', parts[7])

    readelf_s_result = subprocess.run(["eu-readelf", '-s', file],

                                      stdout=subprocess.PIPE, encoding='utf-8', check=True)

    has_file_symbols = any(line for line in readelf_s_result.stdout.split('\n') if contains_file_symbols(line))

    # Test that there are no .gnu_debuglink sections pointing to another

    # debuginfo file. There shouldn't be any debuginfo files, so the link makes

    # no sense either.

    has_gnu_debuglink = any(line for line in readelf_s_result.stdout.split('\n') if '] .gnu_debuglink' in line)

    return ScanResult(file, has_debug_info, has_debug_abbrev, has_file_symbols, has_gnu_debuglink)

def is_elf(file):

    result = subprocess.run(['file', file], stdout=subprocess.PIPE, encoding='utf-8', check=True)

    return re.search('ELF 64-bit LSB (?:executable|shared object)', result.stdout)

def scan_file_if_sensible(file):

    if is_elf(file):

        # print(file)

        return scan_file(file)

    return None

def scan_dir(dir):

    results = []

    for root, _, files in os.walk(dir):

        for name in files:

            result = scan_file_if_sensible(os.path.join(root, name))

            if result:

                results.append(result)

    return results

def scan(file):

    file = os.path.abspath(file)

    if os.path.isdir(file):

        return scan_dir(file)

    elif os.path.isfile(file):

        return [scan_file_if_sensible(file)]

def is_bad_result(result):

    return not result.debug_info or not result.debug_abbrev or not result.file_symbols or result.gnu_debuglink

def print_scan_results(results, verbose):

    # print(results)

    for result in results:

        file_name = result.file_name

        found_issue = False

        if not result.debug_info:

            found_issue = True

            print('error: missing .debug_info section in', file_name)

        if not result.debug_abbrev:

            found_issue = True

            print('error: missing .debug_abbrev section in', file_name)

        if not result.file_symbols:

            found_issue = True

            print('error: missing FILE symbols in', file_name)

        if result.gnu_debuglink:

            found_issue = True

            print('error: unexpected .gnu_debuglink section in', file_name)

        if verbose and not found_issue:

            print('OK: ', file_name)

def main(args):

    verbose = False

    files = []

    for arg in args:

        if arg == '--verbose' or arg == '-v':

            verbose = True

        else:

            files.append(arg)

    results = []

    for file in files:

        results.extend(scan(file))

    print_scan_results(results, verbose)

    if any(is_bad_result(result) for result in results):

        return 1

    return 0

if __name__ == '__main__':

    sys.exit(main(sys.argv[1:]))