rtld: Add glibc.rtld.enable_secure tunable.

Add a tunable for setting __libc_enable_secure to 1.  Do not set
__libc_enable_secure to 0 if the tunable is set to 0.  Ignore all
tunables if glib.rtld.enable_secure is set.  One use-case for this
addition is to enable testing code paths that depend on
__libc_enable_secure being set without the need to use setxid binaries.

Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
This commit is contained in:
Joe Simmons-Talbott 2024-02-29 19:55:58 +00:00 committed by Joe Talbott
parent 9b7091415a
commit 71648e8004
6 changed files with 151 additions and 0 deletions

5
NEWS
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@ -103,6 +103,11 @@ Major new features:
exp, expf, exp10, exp10f, exp2, exp2f, expm1, expm1f, log, logf,
log10, log10f, log1p, log1pf, log2, log2f, sin, sinf, tan, tanf.
* A new tunable, glibc.rtld.enable_secure, used to run a program
as if it were a setuid process. This is currently a testing tool to allow
more extensive verification tests for AT_SECURE programs and not meant to
be a security feature.
Deprecated and removed features, and other changes affecting compatibility:
* The ldconfig program now skips file names containing ';' or ending in

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@ -285,6 +285,7 @@ tests-static-internal := \
tst-tls1-static \
tst-tls1-static-non-pie \
tst-tunables \
tst-tunables-enable_secure \
# tests-static-internal
CRT-tst-tls1-static-non-pie := $(csu-objpfx)crt1.o
@ -2681,6 +2682,7 @@ $(objpfx)tst-glibc-hwcaps-mask.out: \
$(objpfx)tst-glibc-hwcaps-cache.out: $(objpfx)tst-glibc-hwcaps
tst-tunables-ARGS = -- $(host-test-program-cmd)
tst-tunables-enable_secure-ARGS = -- $(host-test-program-cmd)
$(objpfx)list-tunables.out: tst-rtld-list-tunables.sh $(objpfx)ld.so
$(SHELL) $< $(objpfx)ld.so '$(test-wrapper-env)' \

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@ -223,6 +223,17 @@ parse_tunables_string (const char *valstring, struct tunable_toset_t *tunables)
{
tunables[ntunables++] =
(struct tunable_toset_t) { cur, value, p - value };
/* Ignore tunables if enable_secure is set */
if (tunable_is_name ("glibc.rtld.enable_secure", name))
{
tunable_num_t val = (tunable_num_t) _dl_strtoul (value, NULL);
if (val == 1)
{
__libc_enable_secure = 1;
return 0;
}
}
break;
}
}

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@ -136,6 +136,12 @@ glibc {
minval: 0
default: 512
}
enable_secure {
type: INT_32
minval: 0
maxval: 1
default: 0
}
}
mem {

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@ -12,5 +12,6 @@ glibc.malloc.tcache_unsorted_limit: 0x0 (min: 0x0, max: 0x[f]+)
glibc.malloc.top_pad: 0x20000 (min: 0x0, max: 0x[f]+)
glibc.malloc.trim_threshold: 0x0 (min: 0x0, max: 0x[f]+)
glibc.rtld.dynamic_sort: 2 (min: 1, max: 2)
glibc.rtld.enable_secure: 0 (min: 0, max: 1)
glibc.rtld.nns: 0x4 (min: 0x1, max: 0x10)
glibc.rtld.optional_static_tls: 0x200 (min: 0x0, max: 0x[f]+)

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@ -0,0 +1,126 @@
/* Check GLIBC_TUNABLES parsing for enable_secure.
Copyright (C) 2024 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/>. */
#include <array_length.h>
#include <dl-tunables.h>
#include <getopt.h>
#include <intprops.h>
#include <stdint.h>
#include <stdlib.h>
#include <support/capture_subprocess.h>
#include <support/check.h>
#include <sys/auxv.h>
#include <unistd.h>
static int restart;
#define CMDLINE_OPTIONS \
{ "restart", no_argument, &restart, 1 },
static const struct test_t
{
const char *env;
int32_t expected_malloc_check;
int32_t expected_enable_secure;
} tests[] =
{
/* Expected tunable format. */
/* Tunables should be ignored if enable_secure is set. */
{
"glibc.malloc.check=2:glibc.rtld.enable_secure=1",
0,
1,
},
/* Tunables should be ignored if enable_secure is set. */
{
"glibc.rtld.enable_secure=1:glibc.malloc.check=2",
0,
1,
},
/* Tunables should be set if enable_secure is unset. */
{
"glibc.rtld.enable_secure=0:glibc.malloc.check=2",
2,
0,
},
};
static int
handle_restart (int i)
{
if (tests[i].expected_enable_secure == 1)
{
TEST_COMPARE (1, __libc_enable_secure);
}
else
{
TEST_COMPARE (tests[i].expected_malloc_check,
TUNABLE_GET_FULL (glibc, malloc, check, int32_t, NULL));
TEST_COMPARE (tests[i].expected_enable_secure,
TUNABLE_GET_FULL (glibc, rtld, enable_secure, int32_t,
NULL));
}
return 0;
}
static int
do_test (int argc, char *argv[])
{
/* We must have either:
- One or four parameters left if called initially:
+ path to ld.so optional
+ "--library-path" optional
+ the library path optional
+ the application name
+ the test to check */
TEST_VERIFY_EXIT (argc == 2 || argc == 5);
if (restart)
return handle_restart (atoi (argv[1]));
char nteststr[INT_BUFSIZE_BOUND (int)];
char *spargv[10];
{
int i = 0;
for (; i < argc - 1; i++)
spargv[i] = argv[i + 1];
spargv[i++] = (char *) "--direct";
spargv[i++] = (char *) "--restart";
spargv[i++] = nteststr;
spargv[i] = NULL;
}
for (int i = 0; i < array_length (tests); i++)
{
snprintf (nteststr, sizeof nteststr, "%d", i);
printf ("[%d] Spawned test for %s\n", i, tests[i].env);
setenv ("GLIBC_TUNABLES", tests[i].env, 1);
struct support_capture_subprocess result
= support_capture_subprogram (spargv[0], spargv);
support_capture_subprocess_check (&result, "tst-tunables-enable_secure",
0, sc_allow_stderr);
support_capture_subprocess_free (&result);
}
return 0;
}
#define TEST_FUNCTION_ARGV do_test
#include <support/test-driver.c>