From 0e420cc6f6debc2050229ea537b592c963b81a7c Mon Sep 17 00:00:00 2001 From: James Carter Date: Tue, 30 Mar 2021 13:39:18 -0400 Subject: [PATCH] libsepol/cil: Check for statements not allowed in optional blocks While there are some checks for invalid statements in an optional block when resolving the AST, there are no checks when building the AST. OSS-Fuzz found the following policy which caused a null dereference in cil_tree_get_next_path(). (blockinherit b3) (sid SID) (sidorder(SID)) (optional o (ibpkeycon :(1 0)s) (block b3 (filecon""block()) (filecon""block()))) The problem is that the blockinherit copies block b3 before the optional block is disabled. When the optional is disabled, block b3 is deleted along with everything else in the optional. Later, when filecon statements with the same path are found an error message is produced and in trying to find out where the block was copied from, the reference to the deleted block is used. The error handling code assumes (rightly) that if something was copied from a block then that block should still exist. It is clear that in-statements, blocks, and macros cannot be in an optional, because that allows nodes to be copied from the optional block to somewhere outside even though the optional could be disabled later. When optionals are disabled the AST is reset and the resolution is restarted at the point of resolving macro calls, so anything resolved before macro calls will never be re-resolved. This includes tunableifs, in-statements, blockinherits, blockabstracts, and macro definitions. Tunable declarations also cannot be in an optional block because they are needed to resolve tunableifs. It should be fine to allow blockinherit statements in an optional, because that is copying nodes from outside the optional to the optional and if the optional is later disabled, everything will be deleted anyway. Check and quit with an error if a tunable declaration, in-statement, block, blockabstract, or macro definition is found within an optional when either building or resolving the AST. Signed-off-by: James Carter --- libsepol/cil/src/cil_build_ast.c | 32 ++++++++++++++++++++++++++++++ libsepol/cil/src/cil_resolve_ast.c | 4 +++- 2 files changed, 35 insertions(+), 1 deletion(-) diff --git a/libsepol/cil/src/cil_build_ast.c b/libsepol/cil/src/cil_build_ast.c index 3a91be03..4f72884c 100644 --- a/libsepol/cil/src/cil_build_ast.c +++ b/libsepol/cil/src/cil_build_ast.c @@ -52,6 +52,7 @@ struct cil_args_build { struct cil_tree_node *tunif; struct cil_tree_node *in; struct cil_tree_node *macro; + struct cil_tree_node *optional; struct cil_tree_node *boolif; }; @@ -6077,6 +6078,7 @@ int __cil_build_ast_node_helper(struct cil_tree_node *parse_current, uint32_t *f struct cil_tree_node *tunif = args->tunif; struct cil_tree_node *in = args->in; struct cil_tree_node *macro = args->macro; + struct cil_tree_node *optional = args->optional; struct cil_tree_node *boolif = args->boolif; struct cil_tree_node *ast_node = NULL; int rc = SEPOL_ERR; @@ -6127,6 +6129,18 @@ int __cil_build_ast_node_helper(struct cil_tree_node *parse_current, uint32_t *f } } + if (optional != NULL) { + if (parse_current->data == CIL_KEY_TUNABLE || + parse_current->data == CIL_KEY_IN || + parse_current->data == CIL_KEY_BLOCK || + parse_current->data == CIL_KEY_BLOCKABSTRACT || + parse_current->data == CIL_KEY_MACRO) { + rc = SEPOL_ERR; + cil_tree_log(parse_current, CIL_ERR, "%s is not allowed in optionals", (char *)parse_current->data); + goto exit; + } + } + if (boolif != NULL) { if (parse_current->data != CIL_KEY_TUNABLEIF && parse_current->data != CIL_KEY_CALL && @@ -6468,6 +6482,10 @@ int __cil_build_ast_first_child_helper(__attribute__((unused)) struct cil_tree_n args->macro = ast; } + if (ast->flavor == CIL_OPTIONAL) { + args->optional = ast; + } + if (ast->flavor == CIL_BOOLEANIF) { args->boolif = ast; } @@ -6498,6 +6516,19 @@ int __cil_build_ast_last_child_helper(struct cil_tree_node *parse_current, void args->macro = NULL; } + if (ast->flavor == CIL_OPTIONAL) { + struct cil_tree_node *n = ast->parent; + args->optional = NULL; + /* Optionals can be nested */ + while (n && n->flavor != CIL_ROOT) { + if (n->flavor == CIL_OPTIONAL) { + args->optional = n; + break; + } + n = n->parent; + } + } + if (ast->flavor == CIL_BOOLEANIF) { args->boolif = NULL; } @@ -6526,6 +6557,7 @@ int cil_build_ast(struct cil_db *db, struct cil_tree_node *parse_tree, struct ci extra_args.tunif = NULL; extra_args.in = NULL; extra_args.macro = NULL; + extra_args.optional = NULL; extra_args.boolif = NULL; rc = cil_tree_walk(parse_tree, __cil_build_ast_node_helper, __cil_build_ast_first_child_helper, __cil_build_ast_last_child_helper, &extra_args); diff --git a/libsepol/cil/src/cil_resolve_ast.c b/libsepol/cil/src/cil_resolve_ast.c index 06b6ab48..8ffab438 100644 --- a/libsepol/cil/src/cil_resolve_ast.c +++ b/libsepol/cil/src/cil_resolve_ast.c @@ -3723,8 +3723,10 @@ int __cil_resolve_ast_node_helper(struct cil_tree_node *node, uint32_t *finished if (optional != NULL) { if (node->flavor == CIL_TUNABLE || + node->flavor == CIL_IN || + node->flavor == CIL_BLOCK || + node->flavor == CIL_BLOCKABSTRACT || node->flavor == CIL_MACRO) { - /* tuanbles and macros are not allowed in optionals*/ cil_tree_log(node, CIL_ERR, "%s statement is not allowed in optionals", cil_node_to_string(node)); rc = SEPOL_ERR; goto exit; -- 2.30.2