Re: [PATCH] libselinux: ignore invalid class name lookup

[James Carter <jwcart2@gmail.com>]

On Mon, Oct 24, 2022 at 5:14 AM Thiébaud Weksteen <tweek@google.com> wrote:
>
> selinux_check_access relies on string_to_security_class to resolve the
> class index from its char* argument. There is no input validation done
> on the string provided. It is possible to supply an argument containing
> trailing backslashes (i.e., "sock_file//////") so that the paths built
> in discover_class get truncated. The processing will then reference the
> same permission file multiple time (e.g., perms/watch_reads will be
> truncated to perms/watch). This will leak the memory allocated when
> strdup'ing the permission name. The discover_class_cache will end up in
> an invalid state (but not corrupted).
>
> Ensure that the class provided does not contain any path separator.
>
> Signed-off-by: Thiébaud Weksteen <tweek@google.com>

Acked-by: James Carter <jwcart2@gmail.com>

> ---
>  libselinux/src/stringrep.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/libselinux/src/stringrep.c b/libselinux/src/stringrep.c
> index 2fe69f43..592410e5 100644
> --- a/libselinux/src/stringrep.c
> +++ b/libselinux/src/stringrep.c
> @@ -63,6 +63,9 @@ static struct discover_class_node * discover_class(const char *s)
>                 return NULL;
>         }
>
> +       if (strchr(s, '/') != NULL)
> +               return NULL;
> +
>         /* allocate a node */
>         node = malloc(sizeof(struct discover_class_node));
>         if (node == NULL)
> --
> 2.38.0.135.g90850a2211-goog
>