On Wed, Nov 1, 2023 at 12:38 PM Christian Göttsche
<cgzones@xxxxxxxxxxxxxx> wrote:
>
> Ensure constraint expressions are complete and do not exceed the
> supported depth limit.
>
> Signed-off-by: Christian Göttsche <cgzones@xxxxxxxxxxxxxx>
Acked-by: James Carter <jwcart2@xxxxxxxxx>
> ---
> libsepol/src/policydb_validate.c | 20 ++++++++++++++++++++
> 1 file changed, 20 insertions(+)
>
> diff --git a/libsepol/src/policydb_validate.c b/libsepol/src/policydb_validate.c
> index d214bf09..c6a66fb3 100644
> --- a/libsepol/src/policydb_validate.c
> +++ b/libsepol/src/policydb_validate.c
> @@ -228,6 +228,7 @@ bad:
> static int validate_constraint_nodes(sepol_handle_t *handle, unsigned int nperms, const constraint_node_t *cons, validate_t flavors[])
> {
> const constraint_expr_t *cexp;
> + int depth;
>
> for (; cons; cons = cons->next) {
> if (nperms == 0 && cons->permissions != 0)
> @@ -240,8 +241,14 @@ static int validate_constraint_nodes(sepol_handle_t *handle, unsigned int nperms
> if (!cons->expr)
> goto bad;
>
> + depth = -1;
> +
> for (cexp = cons->expr; cexp; cexp = cexp->next) {
> if (cexp->expr_type == CEXPR_NAMES) {
> + if (depth >= (CEXPR_MAXDEPTH - 1))
> + goto bad;
> + depth++;
> +
> if (cexp->attr & CEXPR_XTARGET && nperms != 0)
> goto bad;
> if (!(cexp->attr & CEXPR_TYPE)) {
> @@ -282,6 +289,10 @@ static int validate_constraint_nodes(sepol_handle_t *handle, unsigned int nperms
> goto bad;
> }
> } else if (cexp->expr_type == CEXPR_ATTR) {
> + if (depth >= (CEXPR_MAXDEPTH - 1))
> + goto bad;
> + depth++;
> +
> if (!ebitmap_is_empty(&cexp->names))
> goto bad;
> if (validate_empty_type_set(cexp->type_names))
> @@ -318,8 +329,14 @@ static int validate_constraint_nodes(sepol_handle_t *handle, unsigned int nperms
> } else {
> switch (cexp->expr_type) {
> case CEXPR_NOT:
> + if (depth < 0)
> + goto bad;
> + break;
> case CEXPR_AND:
> case CEXPR_OR:
> + if (depth < 1)
> + goto bad;
> + depth--;
> break;
> default:
> goto bad;
> @@ -335,6 +352,9 @@ static int validate_constraint_nodes(sepol_handle_t *handle, unsigned int nperms
> goto bad;
> }
> }
> +
> + if (depth != 0)
> + goto bad;
> }
>
> return 0;
> --
> 2.42.0
>
