[v3,12/19] elf: Ignore LD_PROFILE for setuid binaries
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Commit Message
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
---
elf/Makefile | 3 +++
elf/rtld.c | 8 +++-----
elf/tst-env-setuid.c | 12 +++++++++++-
3 files changed, 17 insertions(+), 6 deletions(-)
Comments
On 2023-11-06 15:25, Adhemerval Zanella wrote:
> 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
> ---
LGTM.
Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
> elf/Makefile | 3 +++
> elf/rtld.c | 8 +++-----
> elf/tst-env-setuid.c | 12 +++++++++++-
> 3 files changed, 17 insertions(+), 6 deletions(-)
>
> diff --git a/elf/Makefile b/elf/Makefile
> index 52981c19d0..08896bb895 100644
> --- a/elf/Makefile
> +++ b/elf/Makefile
> @@ -2983,3 +2983,6 @@ $(objpfx)tst-dlclose-lazy.out: \
> $(objpfx)tst-dlclose-lazy-mod1.so $(objpfx)tst-dlclose-lazy-mod2.so
>
> 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
> diff --git a/elf/rtld.c b/elf/rtld.c
> index 51b6d9f326..a09cf2a9df 100644
> --- a/elf/rtld.c
> +++ b/elf/rtld.c
> @@ -361,6 +361,7 @@ struct rtld_global_ro _rtld_global_ro attribute_relro =
> ._dl_fpu_control = _FPU_DEFAULT,
> ._dl_pagesize = EXEC_PAGESIZE,
> ._dl_inhibit_cache = 0,
> + ._dl_profile_output = "/var/tmp",
>
> /* Function pointers. */
> ._dl_debug_printf = _dl_debug_printf,
> @@ -2534,10 +2535,6 @@ process_envvars (struct dl_main_state *state)
> char *envline;
> 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)
> {
> size_t len = 0;
> @@ -2586,7 +2583,8 @@ process_envvars (struct dl_main_state *state)
> }
>
> /* 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];
> break;
>
> diff --git a/elf/tst-env-setuid.c b/elf/tst-env-setuid.c
> index ba295a6a14..76b8e1fb45 100644
> --- a/elf/tst-env-setuid.c
> +++ b/elf/tst-env-setuid.c
> @@ -34,6 +34,9 @@ static char SETGID_CHILD[] = "setgid-child";
>
> #define FILTERED_VALUE "some-filtered-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
> {
> @@ -50,7 +53,7 @@ static const struct envvar_t filtered_envvars[] =
> { "LD_HWCAP_MASK", FILTERED_VALUE },
> { "LD_LIBRARY_PATH", FILTERED_VALUE },
> { "LD_PRELOAD", FILTERED_VALUE },
> - { "LD_PROFILE", FILTERED_VALUE },
> + { "LD_PROFILE", "tst-sonamemove-runmod2.so" },
> { "MALLOC_ARENA_MAX", FILTERED_VALUE },
> { "MALLOC_PERTURB_", FILTERED_VALUE },
> { "MALLOC_TRACE", FILTERED_VALUE },
> @@ -87,6 +90,13 @@ test_child (void)
> 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;
> }
>
@@ -2983,3 +2983,6 @@ $(objpfx)tst-dlclose-lazy.out: \
$(objpfx)tst-dlclose-lazy-mod1.so $(objpfx)tst-dlclose-lazy-mod2.so
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
@@ -361,6 +361,7 @@ struct rtld_global_ro _rtld_global_ro attribute_relro =
._dl_fpu_control = _FPU_DEFAULT,
._dl_pagesize = EXEC_PAGESIZE,
._dl_inhibit_cache = 0,
+ ._dl_profile_output = "/var/tmp",
/* Function pointers. */
._dl_debug_printf = _dl_debug_printf,
@@ -2534,10 +2535,6 @@ process_envvars (struct dl_main_state *state)
char *envline;
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)
{
size_t len = 0;
@@ -2586,7 +2583,8 @@ process_envvars (struct dl_main_state *state)
}
/* 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];
break;
@@ -34,6 +34,9 @@ static char SETGID_CHILD[] = "setgid-child";
#define FILTERED_VALUE "some-filtered-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
{
@@ -50,7 +53,7 @@ static const struct envvar_t filtered_envvars[] =
{ "LD_HWCAP_MASK", FILTERED_VALUE },
{ "LD_LIBRARY_PATH", FILTERED_VALUE },
{ "LD_PRELOAD", FILTERED_VALUE },
- { "LD_PROFILE", FILTERED_VALUE },
+ { "LD_PROFILE", "tst-sonamemove-runmod2.so" },
{ "MALLOC_ARENA_MAX", FILTERED_VALUE },
{ "MALLOC_PERTURB_", FILTERED_VALUE },
{ "MALLOC_TRACE", FILTERED_VALUE },
@@ -87,6 +90,13 @@ test_child (void)
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;
}