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This is necessary to place the libio vtables into the RELRO segment. New tests elf/tst-relro-ldso and elf/tst-relro-libc are added to verify that this is what actually happens. The new tests fail on ia64 due to lack of (default) RELRO support inbutils, so they are XFAILed there.nsz/bug23293
Florian Weimer
4 years ago
7 changed files with 190 additions and 118 deletions
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#!/usr/bin/python3 |
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# Verify that certain symbols are covered by RELRO. |
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# Copyright (C) 2022 Free Software Foundation, Inc. |
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# This file is part of the GNU C Library. |
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# |
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# The GNU C Library is free software; you can redistribute it and/or |
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# modify it under the terms of the GNU Lesser General Public |
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# License as published by the Free Software Foundation; either |
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# version 2.1 of the License, or (at your option) any later version. |
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# |
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# The GNU C Library is distributed in the hope that it will be useful, |
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# but WITHOUT ANY WARRANTY; without even the implied warranty of |
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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# Lesser General Public License for more details. |
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# |
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# You should have received a copy of the GNU Lesser General Public |
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# License along with the GNU C Library; if not, see |
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# <https://www.gnu.org/licenses/>. |
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|
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"""Analyze a (shared) object to verify that certain symbols are |
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present and covered by the PT_GNU_RELRO segment. |
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""" |
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import argparse |
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import os.path |
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import sys |
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# Make available glibc Python modules. |
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sys.path.append(os.path.join( |
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os.path.dirname(os.path.realpath(__file__)), os.path.pardir, 'scripts')) |
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import glibcelf |
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def find_relro(path: str, img: glibcelf.Image) -> (int, int): |
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"""Discover the address range of the PT_GNU_RELRO segment.""" |
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for phdr in img.phdrs(): |
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if phdr.p_type == glibcelf.Pt.PT_GNU_RELRO: |
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# The computation is not entirely accurate because |
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# _dl_protect_relro in elf/dl-reloc.c rounds both the |
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# start end and downwards using the run-time page size. |
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return phdr.p_vaddr, phdr.p_vaddr + phdr.p_memsz |
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sys.stdout.write('{}: error: no PT_GNU_RELRO segment\n'.format(path)) |
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sys.exit(1) |
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def check_in_relro(kind, relro_begin, relro_end, name, start, size, error): |
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"""Check if a section or symbol falls within in the RELRO segment.""" |
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end = start + size - 1 |
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if not (relro_begin <= start < end < relro_end): |
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error( |
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'{} {!r} of size {} at 0x{:x} is not in RELRO range [0x{:x}, 0x{:x})'.format( |
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kind, name.decode('UTF-8'), start, size, |
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relro_begin, relro_end)) |
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|
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def get_parser(): |
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"""Return an argument parser for this script.""" |
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parser = argparse.ArgumentParser(description=__doc__) |
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parser.add_argument('object', help='path to object file to check') |
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parser.add_argument('--required', metavar='NAME', default=(), |
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help='required symbol names', nargs='*') |
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parser.add_argument('--optional', metavar='NAME', default=(), |
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help='required symbol names', nargs='*') |
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return parser |
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def main(argv): |
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"""The main entry point.""" |
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parser = get_parser() |
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opts = parser.parse_args(argv) |
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img = glibcelf.Image.readfile(opts.object) |
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required_symbols = frozenset([sym.encode('UTF-8') |
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for sym in opts.required]) |
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optional_symbols = frozenset([sym.encode('UTF-8') |
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for sym in opts.optional]) |
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check_symbols = required_symbols | optional_symbols |
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# Tracks the symbols in check_symbols that have been found. |
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symbols_found = set() |
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# Discover the extent of the RELRO segment. |
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relro_begin, relro_end = find_relro(opts.object, img) |
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symbol_table_found = False |
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errors = False |
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def error(msg: str) -> None: |
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"""Record an error condition and write a message to standard output.""" |
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nonlocal errors |
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errors = True |
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sys.stdout.write('{}: error: {}\n'.format(opts.object, msg)) |
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# Iterate over section headers to find the symbol table. |
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for shdr in img.shdrs(): |
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if shdr.sh_type == glibcelf.Sht.SHT_SYMTAB: |
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symbol_table_found = True |
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for sym in img.syms(shdr): |
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if sym.st_name in check_symbols: |
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symbols_found.add(sym.st_name) |
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# Validate symbol type, section, and size. |
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if sym.st_info.type != glibcelf.Stt.STT_OBJECT: |
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error('symbol {!r} has wrong type {}'.format( |
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sym.st_name.decode('UTF-8'), sym.st_info.type)) |
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if sym.st_shndx in glibcelf.Shn: |
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error('symbol {!r} has reserved section {}'.format( |
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sym.st_name.decode('UTF-8'), sym.st_shndx)) |
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continue |
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if sym.st_size == 0: |
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error('symbol {!r} has size zero'.format( |
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sym.st_name.decode('UTF-8'))) |
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continue |
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check_in_relro('symbol', relro_begin, relro_end, |
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sym.st_name, sym.st_value, sym.st_size, |
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error) |
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continue # SHT_SYMTAB |
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if shdr.sh_name == b'.data.rel.ro' \ |
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or shdr.sh_name.startswith(b'.data.rel.ro.'): |
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check_in_relro('section', relro_begin, relro_end, |
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shdr.sh_name, shdr.sh_addr, shdr.sh_size, |
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error) |
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continue |
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if required_symbols - symbols_found: |
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for sym in sorted(required_symbols - symbols_found): |
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error('symbol {!r} not found'.format(sym.decode('UTF-8'))) |
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if errors: |
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sys.exit(1) |
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if not symbol_table_found: |
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sys.stdout.write( |
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'{}: warning: no symbol table found (stripped object)\n'.format( |
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opts.object)) |
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sys.exit(77) |
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if __name__ == '__main__': |
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main(sys.argv[1:]) |
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