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authorFlorian Weimer <fweimer@redhat.com>2022-04-11 11:30:31 +0200
committerFlorian Weimer <fweimer@redhat.com>2022-04-22 10:59:03 +0200
commit198abcbb94618730dae1b3f4393efaa49e0ec8c7 (patch)
tree80c663ec8c907fe0c25d83e3fac5362bc4424ecb /elf
parent30035d67728a846fa39749cd162afd278ac654c4 (diff)
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Default to --with-default-link=no (bug 25812)
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.
Diffstat (limited to 'elf')
-rw-r--r--elf/Makefile33
-rw-r--r--elf/tst-relro-symbols.py137
2 files changed, 170 insertions, 0 deletions
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:])