diff options
| -rw-r--r-- | INSTALL | 6 | ||||
| -rwxr-xr-x | configure | 65 | ||||
| -rw-r--r-- | configure.ac | 55 | ||||
| -rw-r--r-- | elf/Makefile | 33 | ||||
| -rw-r--r-- | elf/tst-relro-symbols.py | 137 | ||||
| -rw-r--r-- | manual/install.texi | 6 | ||||
| -rw-r--r-- | sysdeps/unix/sysv/linux/ia64/Makefile | 6 |
7 files changed, 190 insertions, 118 deletions
diff --git a/INSTALL b/INSTALL index 63c022d6b9..b68884ccd6 100644 --- a/INSTALL +++ b/INSTALL @@ -90,6 +90,12 @@ if 'CFLAGS' is specified it must enable optimization. For example: library will still be usable, but functionality may be lost--for example, you can't build a shared libc with old binutils. +'--with-default-link=FLAG' + With '--with-default-link=yes', the build system does not use a + custom linker script for linking shared objects. The default for + FLAG is the opposite, 'no', because the custom linker script is + needed for full RELRO protection. + '--with-nonshared-cflags=CFLAGS' Use additional compiler flags CFLAGS to build the parts of the library which are always statically linked into applications and diff --git a/configure b/configure index d2f413d05d..650bfd982c 100755 --- a/configure +++ b/configure @@ -3375,7 +3375,7 @@ fi if test "${with_default_link+set}" = set; then : withval=$with_default_link; use_default_link=$withval else - use_default_link=default + use_default_link=no fi @@ -6184,69 +6184,6 @@ fi $as_echo "$libc_cv_hashstyle" >&6; } -# The linker's default -shared behavior is good enough if it -# does these things that our custom linker scripts ensure that -# all allocated NOTE sections come first. -if test "$use_default_link" = default; then - { $as_echo "$as_me:${as_lineno-$LINENO}: checking for sufficient default -shared layout" >&5 -$as_echo_n "checking for sufficient default -shared layout... " >&6; } -if ${libc_cv_use_default_link+:} false; then : - $as_echo_n "(cached) " >&6 -else - libc_cv_use_default_link=no - cat > conftest.s <<\EOF - .section .note.a,"a",%note - .balign 4 - .long 4,4,9 - .string "GNU" - .string "foo" - .section .note.b,"a",%note - .balign 4 - .long 4,4,9 - .string "GNU" - .string "bar" -EOF - if { ac_try=' ${CC-cc} $ASFLAGS -shared -o conftest.so conftest.s 1>&5' - { { eval echo "\"\$as_me\":${as_lineno-$LINENO}: \"$ac_try\""; } >&5 - (eval $ac_try) 2>&5 - ac_status=$? - $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5 - test $ac_status = 0; }; } && - ac_try=`$READELF -S conftest.so | sed -n \ - '${x;p;} - s/^ *\[ *[1-9][0-9]*\] *\([^ ][^ ]*\) *\([^ ][^ ]*\) .*$/\2 \1/ - t a - b - : a - H'` - then - libc_seen_a=no libc_seen_b=no - set -- $ac_try - while test $# -ge 2 -a "$1" = NOTE; do - case "$2" in - .note.a) libc_seen_a=yes ;; - .note.b) libc_seen_b=yes ;; - esac - shift 2 - done - case "$libc_seen_a$libc_seen_b" in - yesyes) - libc_cv_use_default_link=yes - ;; - *) - echo >&5 "\ -$libc_seen_a$libc_seen_b from: -$ac_try" - ;; - esac - fi - rm -f conftest* -fi -{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $libc_cv_use_default_link" >&5 -$as_echo "$libc_cv_use_default_link" >&6; } - use_default_link=$libc_cv_use_default_link -fi - { $as_echo "$as_me:${as_lineno-$LINENO}: checking for GLOB_DAT reloc" >&5 $as_echo_n "checking for GLOB_DAT reloc... " >&6; } if ${libc_cv_has_glob_dat+:} false; then : diff --git a/configure.ac b/configure.ac index b6a747dece..605efd549d 100644 --- a/configure.ac +++ b/configure.ac @@ -153,7 +153,7 @@ AC_ARG_WITH([default-link], AS_HELP_STRING([--with-default-link], [do not use explicit linker scripts]), [use_default_link=$withval], - [use_default_link=default]) + [use_default_link=no]) dnl Additional build flags injection. AC_ARG_WITH([nonshared-cflags], @@ -1371,59 +1371,6 @@ fi rm -f conftest*]) AC_SUBST(libc_cv_hashstyle) -# The linker's default -shared behavior is good enough if it -# does these things that our custom linker scripts ensure that -# all allocated NOTE sections come first. -if test "$use_default_link" = default; then - AC_CACHE_CHECK([for sufficient default -shared layout], - libc_cv_use_default_link, [dnl - libc_cv_use_default_link=no - cat > conftest.s <<\EOF - .section .note.a,"a",%note - .balign 4 - .long 4,4,9 - .string "GNU" - .string "foo" - .section .note.b,"a",%note - .balign 4 - .long 4,4,9 - .string "GNU" - .string "bar" -EOF - if AC_TRY_COMMAND([dnl - ${CC-cc} $ASFLAGS -shared -o conftest.so conftest.s 1>&AS_MESSAGE_LOG_FD]) && - ac_try=`$READELF -S conftest.so | sed -n \ - ['${x;p;} - s/^ *\[ *[1-9][0-9]*\] *\([^ ][^ ]*\) *\([^ ][^ ]*\) .*$/\2 \1/ - t a - b - : a - H']` - then - libc_seen_a=no libc_seen_b=no - set -- $ac_try - while test $# -ge 2 -a "$1" = NOTE; do - case "$2" in - .note.a) libc_seen_a=yes ;; - .note.b) libc_seen_b=yes ;; - esac - shift 2 - done - case "$libc_seen_a$libc_seen_b" in - yesyes) - libc_cv_use_default_link=yes - ;; - *) - echo >&AS_MESSAGE_LOG_FD "\ -$libc_seen_a$libc_seen_b from: -$ac_try" - ;; - esac - fi - rm -f conftest*]) - use_default_link=$libc_cv_use_default_link -fi - AC_CACHE_CHECK(for GLOB_DAT reloc, libc_cv_has_glob_dat, [dnl cat > conftest.c <<EOF diff --git a/elf/Makefile b/elf/Makefile index 3d79f40879..8ed6c3b0b1 100644 --- a/elf/Makefile +++ b/elf/Makefile @@ -543,6 +543,39 @@ endif endif endif +tests-special += $(objpfx)tst-relro-ldso.out $(objpfx)tst-relro-libc.out +$(objpfx)tst-relro-ldso.out: tst-relro-symbols.py $(..)/scripts/glibcelf.py \ + $(objpfx)ld.so + $(PYTHON) tst-relro-symbols.py $(objpfx)ld.so \ + --required=_rtld_global_ro \ + > $@ 2>&1; $(evaluate-test) +# The optional symbols are present in libc only if the architecture has +# the GLIBC_2.0 symbol set in libc. +$(objpfx)tst-relro-libc.out: tst-relro-symbols.py $(..)/scripts/glibcelf.py \ + $(common-objpfx)libc.so + $(PYTHON) tst-relro-symbols.py $(common-objpfx)libc.so \ + --required=_IO_cookie_jumps \ + --required=_IO_file_jumps \ + --required=_IO_file_jumps_maybe_mmap \ + --required=_IO_file_jumps_mmap \ + --required=_IO_helper_jumps \ + --required=_IO_mem_jumps \ + --required=_IO_obstack_jumps \ + --required=_IO_proc_jumps \ + --required=_IO_str_chk_jumps \ + --required=_IO_str_jumps \ + --required=_IO_strn_jumps \ + --required=_IO_wfile_jumps \ + --required=_IO_wfile_jumps_maybe_mmap \ + --required=_IO_wfile_jumps_mmap \ + --required=_IO_wmem_jumps \ + --required=_IO_wstr_jumps \ + --required=_IO_wstrn_jumps \ + --optional=_IO_old_cookie_jumps \ + --optional=_IO_old_file_jumps \ + --optional=_IO_old_proc_jumps \ + > $@ 2>&1; $(evaluate-test) + ifeq ($(run-built-tests),yes) tests-special += $(objpfx)tst-valgrind-smoke.out endif diff --git a/elf/tst-relro-symbols.py b/elf/tst-relro-symbols.py new file mode 100644 index 0000000000..368ea3349f --- /dev/null +++ b/elf/tst-relro-symbols.py @@ -0,0 +1,137 @@ +#!/usr/bin/python3 +# Verify that certain symbols are covered by RELRO. +# Copyright (C) 2022 Free Software Foundation, Inc. +# This file is part of the GNU C Library. +# +# The GNU C Library is free software; you can redistribute it and/or +# modify it under the terms of the GNU Lesser General Public +# License as published by the Free Software Foundation; either +# version 2.1 of the License, or (at your option) any later version. +# +# The GNU C Library is distributed in the hope that it will be useful, +# but WITHOUT ANY WARRANTY; without even the implied warranty of +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU +# Lesser General Public License for more details. +# +# You should have received a copy of the GNU Lesser General Public +# License along with the GNU C Library; if not, see +# <https://www.gnu.org/licenses/>. + +"""Analyze a (shared) object to verify that certain symbols are +present and covered by the PT_GNU_RELRO segment. + +""" + +import argparse +import os.path +import sys + +# Make available glibc Python modules. +sys.path.append(os.path.join( + os.path.dirname(os.path.realpath(__file__)), os.path.pardir, 'scripts')) + +import glibcelf + +def find_relro(path: str, img: glibcelf.Image) -> (int, int): + """Discover the address range of the PT_GNU_RELRO segment.""" + for phdr in img.phdrs(): + if phdr.p_type == glibcelf.Pt.PT_GNU_RELRO: + # The computation is not entirely accurate because + # _dl_protect_relro in elf/dl-reloc.c rounds both the + # start end and downwards using the run-time page size. + return phdr.p_vaddr, phdr.p_vaddr + phdr.p_memsz + sys.stdout.write('{}: error: no PT_GNU_RELRO segment\n'.format(path)) + sys.exit(1) + +def check_in_relro(kind, relro_begin, relro_end, name, start, size, error): + """Check if a section or symbol falls within in the RELRO segment.""" + end = start + size - 1 + if not (relro_begin <= start < end < relro_end): + error( + '{} {!r} of size {} at 0x{:x} is not in RELRO range [0x{:x}, 0x{:x})'.format( + kind, name.decode('UTF-8'), start, size, + relro_begin, relro_end)) + +def get_parser(): + """Return an argument parser for this script.""" + parser = argparse.ArgumentParser(description=__doc__) + parser.add_argument('object', help='path to object file to check') + parser.add_argument('--required', metavar='NAME', default=(), + help='required symbol names', nargs='*') + parser.add_argument('--optional', metavar='NAME', default=(), + help='required symbol names', nargs='*') + return parser + +def main(argv): + """The main entry point.""" + parser = get_parser() + opts = parser.parse_args(argv) + img = glibcelf.Image.readfile(opts.object) + + required_symbols = frozenset([sym.encode('UTF-8') + for sym in opts.required]) + optional_symbols = frozenset([sym.encode('UTF-8') + for sym in opts.optional]) + check_symbols = required_symbols | optional_symbols + + # Tracks the symbols in check_symbols that have been found. + symbols_found = set() + + # Discover the extent of the RELRO segment. + relro_begin, relro_end = find_relro(opts.object, img) + symbol_table_found = False + + errors = False + def error(msg: str) -> None: + """Record an error condition and write a message to standard output.""" + nonlocal errors + errors = True + sys.stdout.write('{}: error: {}\n'.format(opts.object, msg)) + + # Iterate over section headers to find the symbol table. + for shdr in img.shdrs(): + if shdr.sh_type == glibcelf.Sht.SHT_SYMTAB: + symbol_table_found = True + for sym in img.syms(shdr): + if sym.st_name in check_symbols: + symbols_found.add(sym.st_name) + + # Validate symbol type, section, and size. + if sym.st_info.type != glibcelf.Stt.STT_OBJECT: + error('symbol {!r} has wrong type {}'.format( + sym.st_name.decode('UTF-8'), sym.st_info.type)) + if sym.st_shndx in glibcelf.Shn: + error('symbol {!r} has reserved section {}'.format( + sym.st_name.decode('UTF-8'), sym.st_shndx)) + continue + if sym.st_size == 0: + error('symbol {!r} has size zero'.format( + sym.st_name.decode('UTF-8'))) + continue + + check_in_relro('symbol', relro_begin, relro_end, + sym.st_name, sym.st_value, sym.st_size, + error) + continue # SHT_SYMTAB + if shdr.sh_name == b'.data.rel.ro' \ + or shdr.sh_name.startswith(b'.data.rel.ro.'): + check_in_relro('section', relro_begin, relro_end, + shdr.sh_name, shdr.sh_addr, shdr.sh_size, + error) + continue + + if required_symbols - symbols_found: + for sym in sorted(required_symbols - symbols_found): + error('symbol {!r} not found'.format(sym.decode('UTF-8'))) + + if errors: + sys.exit(1) + + if not symbol_table_found: + sys.stdout.write( + '{}: warning: no symbol table found (stripped object)\n'.format( + opts.object)) + sys.exit(77) + +if __name__ == '__main__': + main(sys.argv[1:]) diff --git a/manual/install.texi b/manual/install.texi index 29c52f2927..fcfb6901e4 100644 --- a/manual/install.texi +++ b/manual/install.texi @@ -117,6 +117,12 @@ problem and suppress these constructs, so that the library will still be usable, but functionality may be lost---for example, you can't build a shared libc with old binutils. +@item --with-default-link=@var{FLAG} +With @code{--with-default-link=yes}, the build system does not use a +custom linker script for linking shared objects. The default for +@var{FLAG} is the opposite, @samp{no}, because the custom linker script +is needed for full RELRO protection. + @item --with-nonshared-cflags=@var{cflags} Use additional compiler flags @var{cflags} to build the parts of the library which are always statically linked into applications and diff --git a/sysdeps/unix/sysv/linux/ia64/Makefile b/sysdeps/unix/sysv/linux/ia64/Makefile index da85ba43e2..c5cc41b367 100644 --- a/sysdeps/unix/sysv/linux/ia64/Makefile +++ b/sysdeps/unix/sysv/linux/ia64/Makefile @@ -1,3 +1,9 @@ +ifeq ($(subdir),elf) +# ia64 does not support PT_GNU_RELRO. +test-xfail-tst-relro-ldso = yes +test-xfail-tst-relro-libc = yes +endif + ifeq ($(subdir),misc) sysdep_headers += sys/rse.h endif |