From 8470058934e89d1876b8e034d1ea818bde62b994 Mon Sep 17 00:00:00 2001
From: James Carter <jwcart2@gmail.com>
Date: Mon, 12 Jul 2021 09:50:38 -0400
Subject: [PATCH] libsepol/cil: Fix handling category sets in an expression

There are two problems that need to be addressed when resolving an
expression with category sets.

1. Only expand anonymous category sets in an expression.

Commit 982ec302b67f3c7f8df667dadb67352b1e4a6d18 (libsepol/cil:
Account for anonymous category sets in an expression) attempted to
properly handle anonymous category sets when resolving category
expressions. Unfortunately, it did not check whether a category set
was actually an anonymous category set and expanded all category
sets in an expression. If a category set refers to itself in the
expression, then everything from the name of the category set to the
end of the expression is ignored.

For example, the rule "(categoryset cs (c0 cs c1 c2))", would be
equivalent to the rule "(categoryset cs (c0))" as everything from
"cs" to the end would be dropped. The secilc-fuzzer found that the
rule "(categoryset cat (not cat))" would cause a segfault since
"(not)" is not a valid expression and it is assumed to be valid
during later evaluation because syntax checking has already been
done.

Instead, check whether or not the category set is anonymous before
expanding it when resolving an expression.

2. Category sets cannot be used in a category range

A category range can be used to specify a large number of categories.
The range "(range c0 c1023)" refers to 1024 categories. Only categories
and category aliases can be used in a range. Determining if an
identifier is a category, an alias, or a set can only be done after
resolving the identifer.

Keep track of the current operator as an expression is being resolved
and if the expression involves categories and a category set is
encountered, then return an error if the expression is a category
range.

Signed-off-by: James Carter <jwcart2@gmail.com>
---
 libsepol/cil/src/cil_resolve_ast.c | 28 +++++++++++++++++++++-------
 1 file changed, 21 insertions(+), 7 deletions(-)

diff --git a/libsepol/cil/src/cil_resolve_ast.c b/libsepol/cil/src/cil_resolve_ast.c
index 145d4e7452dd..180073247617 100644
--- a/libsepol/cil/src/cil_resolve_ast.c
+++ b/libsepol/cil/src/cil_resolve_ast.c
@@ -3228,6 +3228,7 @@ int cil_resolve_expr(enum cil_flavor expr_type, struct cil_list *str_expr, struc
 	struct cil_symtab_datum *res_datum = NULL;
 	enum cil_sym_index sym_index =  CIL_SYM_UNKNOWN;
 	struct cil_list *datum_sub_expr;
+	enum cil_flavor op = CIL_NONE;
 
 	switch (str_expr->flavor) {
 	case CIL_BOOL:
@@ -3263,14 +3264,24 @@ int cil_resolve_expr(enum cil_flavor expr_type, struct cil_list *str_expr, struc
 			}
 			if (sym_index == CIL_SYM_CATS && NODE(res_datum)->flavor == CIL_CATSET) {
 				struct cil_catset *catset = (struct cil_catset *)res_datum;
-				if (!catset->cats->datum_expr) {
-					rc = cil_resolve_expr(expr_type, catset->cats->str_expr, &catset->cats->datum_expr, parent, extra_args);
-					if (rc != SEPOL_OK) {
-						goto exit;
+				if (op == CIL_RANGE) {
+					cil_tree_log(parent, CIL_ERR, "Category set not allowed in category range");
+					rc = SEPOL_ERR;
+					goto exit;
+				}
+				if (!res_datum->name) {
+					/* Anonymous category sets need to be resolved when encountered */
+					if (!catset->cats->datum_expr) {
+						rc = cil_resolve_expr(expr_type, catset->cats->str_expr, &catset->cats->datum_expr, parent, extra_args);
+						if (rc != SEPOL_OK) {
+							goto exit;
+						}
 					}
+					cil_copy_list(catset->cats->datum_expr, &datum_sub_expr);
+					cil_list_append(*datum_expr, CIL_LIST, datum_sub_expr);
+				} else {
+					cil_list_append(*datum_expr, CIL_DATUM, res_datum);
 				}
-				cil_copy_list(catset->cats->datum_expr, &datum_sub_expr);
-				cil_list_append(*datum_expr, CIL_LIST, datum_sub_expr);
 			} else {
 				if (sym_index == CIL_SYM_TYPES && (expr_type == CIL_CONSTRAIN || expr_type == CIL_VALIDATETRANS)) {
 					cil_type_used(res_datum, CIL_ATTR_CONSTRAINT);
@@ -3287,9 +3298,12 @@ int cil_resolve_expr(enum cil_flavor expr_type, struct cil_list *str_expr, struc
 			break;
 		}
 		default:
+			if (curr->flavor == CIL_OP) {
+				op = (enum cil_flavor)(uintptr_t)curr->data;
+			}
 			cil_list_append(*datum_expr, curr->flavor, curr->data);
 			break;
-		}				
+		}
 	}
 	return SEPOL_OK;
 
-- 
2.32.0