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elf: Ignore LD_PROFILE for setuid binaries 

Loader does not ignore LD_PROFILE in secure-execution mode (different
than man-page states [1]), rather it uses a different path
(/var/profile) and ignore LD_PROFILE_OUTPUT.

Allowing secure-execution profiling is already a non good security
boundary, since it enables different code paths and extra OS access by
the process.  But by ignoring LD_PROFILE_OUTPUT, the resulting profile
file might also be acceded in a racy manner since the file name does not
use any process-specific information (such as pid, timing, etc.).

Another side-effect is it forces lazy binding even on libraries that
might be with DF_BIND_NOW.

[1] https://man7.org/linux/man-pages/man8/ld.so.8.html
Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
This commit is contained in:
Adhemerval Zanella 2023-11-06 17:25:45 -03:00
parent 1c87f71a36
commit 4a133885a7
3 changed files with 17 additions and 6 deletions
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3
elf/Makefile
View File

@ -3002,3 +3002,6 @@ $(objpfx)tst-non-directory-path.out: tst-non-directory-path.sh \
$(evaluate-test) $(evaluate-test)
tst-env-setuid-ARGS = -- $(host-test-program-cmd) tst-env-setuid-ARGS = -- $(host-test-program-cmd)
# Reuse a module with a SONAME, to specific as the LD_PROFILE.
$(objpfx)tst-env-setuid: $(objpfx)tst-sonamemove-runmod2.so

8
elf/rtld.c
View File

@ -361,6 +361,7 @@ struct rtld_global_ro _rtld_global_ro attribute_relro =
._dl_fpu_control = _FPU_DEFAULT, ._dl_fpu_control = _FPU_DEFAULT,
._dl_pagesize = EXEC_PAGESIZE, ._dl_pagesize = EXEC_PAGESIZE,
._dl_inhibit_cache = 0, ._dl_inhibit_cache = 0,
._dl_profile_output = "/var/tmp",
/* Function pointers. */ /* Function pointers. */
._dl_debug_printf = _dl_debug_printf, ._dl_debug_printf = _dl_debug_printf,
@ -2534,10 +2535,6 @@ process_envvars (struct dl_main_state *state)
char *envline; char *envline;
char *debug_output = NULL; char *debug_output = NULL;
/* This is the default place for profiling data file. */
GLRO(dl_profile_output)
= &"/var/tmp\0/var/profile"[__libc_enable_secure ? 9 : 0];
while ((envline = _dl_next_ld_env_entry (&runp)) != NULL) while ((envline = _dl_next_ld_env_entry (&runp)) != NULL)
{ {
size_t len = 0; size_t len = 0;
@ -2586,7 +2583,8 @@ process_envvars (struct dl_main_state *state)
} }
/* Which shared object shall be profiled. */ /* Which shared object shall be profiled. */
if (memcmp (envline, "PROFILE", 7) == 0 && envline[8] != '\0') if (!__libc_enable_secure
&& memcmp (envline, "PROFILE", 7) == 0 && envline[8] != '\0')
GLRO(dl_profile) = &envline[8]; GLRO(dl_profile) = &envline[8];
break; break;

12
elf/tst-env-setuid.c
View File

@ -34,6 +34,9 @@ static char SETGID_CHILD[] = "setgid-child";
#define FILTERED_VALUE "some-filtered-value" #define FILTERED_VALUE "some-filtered-value"
#define UNFILTERED_VALUE "some-unfiltered-value" #define UNFILTERED_VALUE "some-unfiltered-value"
/* It assumes no other programs is being profile with a library with same
SONAME using the default folder. */
#define PROFILE_LIB "tst-sonamemove-runmod2.so"
struct envvar_t struct envvar_t
{ {
@ -50,7 +53,7 @@ static const struct envvar_t filtered_envvars[] =
{ "LD_HWCAP_MASK", FILTERED_VALUE }, { "LD_HWCAP_MASK", FILTERED_VALUE },
{ "LD_LIBRARY_PATH", FILTERED_VALUE }, { "LD_LIBRARY_PATH", FILTERED_VALUE },
{ "LD_PRELOAD", FILTERED_VALUE }, { "LD_PRELOAD", FILTERED_VALUE },
{ "LD_PROFILE", FILTERED_VALUE }, { "LD_PROFILE", "tst-sonamemove-runmod2.so" },
{ "MALLOC_ARENA_MAX", FILTERED_VALUE }, { "MALLOC_ARENA_MAX", FILTERED_VALUE },
{ "MALLOC_PERTURB_", FILTERED_VALUE }, { "MALLOC_PERTURB_", FILTERED_VALUE },
{ "MALLOC_TRACE", FILTERED_VALUE }, { "MALLOC_TRACE", FILTERED_VALUE },
@ -87,6 +90,13 @@ test_child (void)
ret |= !(env != NULL && strcmp (env, e->value) == 0); ret |= !(env != NULL && strcmp (env, e->value) == 0);
} }
/* Also check if no profile file was created. */
{
char *profilepath = xasprintf ("/var/tmp/%s.profile", PROFILE_LIB);
ret |= !access (profilepath, R_OK);
free (profilepath);
}
return ret; return ret;
} }