On Fri, 2017-05-05 at 14:49 +0200, Vit Mojzis wrote:
> access() uses real UID instead of effective UID which causes false
> negative checks in setuid programs.
> Replace access(,F_OK) (i.e. tests for file existence) by stat().
>
> Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1186431
>
> Signed-off-by: Vit Mojzis <[email protected]>
> ---
> libsemanage/src/direct_api.c | 36 +++++++++++++++++++++-------------
> --
> 1 file changed, 21 insertions(+), 15 deletions(-)
>
> diff --git a/libsemanage/src/direct_api.c
> b/libsemanage/src/direct_api.c
> index 508277d..35ca1b0 100644
> --- a/libsemanage/src/direct_api.c
> +++ b/libsemanage/src/direct_api.c
> @@ -272,7 +272,9 @@ int semanage_direct_connect(semanage_handle_t *
> sh)
>
> /* set the disable dontaudit value */
> path = semanage_path(SEMANAGE_ACTIVE,
> SEMANAGE_DISABLE_DONTAUDIT);
> - if (access(path, F_OK) == 0)
> +
> + struct stat sb;
> + if (stat(path, &sb) == 0)
Need to check errno as well to ensure that it is just ENOENT when
stat() returns non-zero; anything else is an error.
stat() can produce a SELinux getattr denial, whereas access(F_OK)
doesn't perform any SELinux check beyond directory search access.
> sepol_set_disable_dontaudit(sh->sepolh, 1);
> else
> sepol_set_disable_dontaudit(sh->sepolh, 0);
> @@ -1101,8 +1103,9 @@ static int
> semanage_compile_hll_modules(semanage_handle_t *sh,
> goto cleanup;
> }
>
> + struct stat sb;
> if (semanage_get_ignore_module_cache(sh) == 0 &&
> - access(cil_path, F_OK) == 0) {
> + stat(cil_path, &sb) == 0) {
> continue;
> }
>
> @@ -1165,7 +1168,8 @@ static int
> semanage_direct_commit(semanage_handle_t * sh)
>
> /* Create or remove the disable_dontaudit flag file. */
> path = semanage_path(SEMANAGE_TMP,
> SEMANAGE_DISABLE_DONTAUDIT);
> - if (access(path, F_OK) == 0)
> + struct stat sb;
> + if (stat(path, &sb) == 0)
> do_rebuild |= !(sepol_get_disable_dontaudit(sh-
> >sepolh) == 1);
> else
> do_rebuild |= (sepol_get_disable_dontaudit(sh-
> >sepolh) == 1);
> @@ -1190,7 +1194,7 @@ static int
> semanage_direct_commit(semanage_handle_t * sh)
>
> /* Create or remove the preserve_tunables flag file. */
> path = semanage_path(SEMANAGE_TMP,
> SEMANAGE_PRESERVE_TUNABLES);
> - if (access(path, F_OK) == 0)
> + if (stat(path, &sb) == 0)
> do_rebuild |= !(sepol_get_preserve_tunables(sh-
> >sepolh) == 1);
> else
> do_rebuild |= (sepol_get_preserve_tunables(sh-
> >sepolh) == 1);
> @@ -1231,37 +1235,37 @@ static int
> semanage_direct_commit(semanage_handle_t * sh)
> */
> if (!do_rebuild) {
> path = semanage_path(SEMANAGE_TMP,
> SEMANAGE_STORE_KERNEL);
> - if (access(path, F_OK) != 0) {
> + if (stat(path, &sb) != 0) {
> do_rebuild = 1;
> goto rebuild;
> }
>
> path = semanage_path(SEMANAGE_TMP,
> SEMANAGE_STORE_FC);
> - if (access(path, F_OK) != 0) {
> + if (stat(path, &sb) != 0) {
> do_rebuild = 1;
> goto rebuild;
> }
>
> path = semanage_path(SEMANAGE_TMP,
> SEMANAGE_STORE_SEUSERS);
> - if (access(path, F_OK) != 0) {
> + if (stat(path, &sb) != 0) {
> do_rebuild = 1;
> goto rebuild;
> }
>
> path = semanage_path(SEMANAGE_TMP, SEMANAGE_LINKED);
> - if (access(path, F_OK) != 0) {
> + if (stat(path, &sb) != 0) {
> do_rebuild = 1;
> goto rebuild;
> }
>
> path = semanage_path(SEMANAGE_TMP,
> SEMANAGE_SEUSERS_LINKED);
> - if (access(path, F_OK) != 0) {
> + if (stat(path, &sb) != 0) {
> do_rebuild = 1;
> goto rebuild;
> }
>
> path = semanage_path(SEMANAGE_TMP,
> SEMANAGE_USERS_EXTRA_LINKED);
> - if (access(path, F_OK) != 0) {
> + if (stat(path, &sb) != 0) {
> do_rebuild = 1;
> goto rebuild;
> }
> @@ -1395,7 +1399,7 @@ rebuild:
> goto cleanup;
>
> path = semanage_path(SEMANAGE_TMP,
> SEMANAGE_SEUSERS_LINKED);
> - if (access(path, F_OK) == 0) {
> + if (stat(path, &sb) == 0) {
> retval = semanage_copy_file(path,
> semanage_path(SE
> MANAGE_TMP,
> SE
> MANAGE_STORE_SEUSERS),
> @@ -1408,7 +1412,7 @@ rebuild:
> }
>
> path = semanage_path(SEMANAGE_TMP,
> SEMANAGE_USERS_EXTRA_LINKED);
> - if (access(path, F_OK) == 0) {
> + if (stat(path, &sb) == 0) {
> retval = semanage_copy_file(path,
> semanage_path(SE
> MANAGE_TMP,
> SE
> MANAGE_USERS_EXTRA),
> @@ -1732,7 +1736,8 @@ static int
> semanage_direct_extract(semanage_handle_t * sh,
> goto cleanup;
> }
>
> - if (access(module_path, F_OK) != 0) {
> + struct stat sb;
> + if (stat(module_path, &sb) != 0) {
> ERR(sh, "Module does not exist: %s", module_path);
> rc = -1;
> goto cleanup;
> @@ -1762,7 +1767,7 @@ static int
> semanage_direct_extract(semanage_handle_t * sh,
> goto cleanup;
> }
>
> - if (extract_cil == 1 && strcmp(_modinfo->lang_ext, "cil") &&
> access(input_file, F_OK) != 0) {
> + if (extract_cil == 1 && strcmp(_modinfo->lang_ext, "cil") &&
> stat(input_file, &sb) != 0) {
> rc = semanage_compile_module(sh, _modinfo);
> if (rc < 0) {
> goto cleanup;
> @@ -2737,7 +2742,8 @@ static int
> semanage_direct_install_info(semanage_handle_t *sh,
> goto cleanup;
> }
>
> - if (access(path, F_OK) == 0) {
> + struct stat sb;
> + if (stat(path, &sb) == 0) {
> ret = unlink(path);
> if (ret != 0) {
> ERR(sh, "Error while removing cached
> CIL file %s: %s", path, strerror(errno));
