[PATCH v2] libsepol: cil: Add ability to redeclare types[attributes]

[Daniel Cashman <dcashman@android.com>]

From: Dan Cashman <dcashman@android.com>

Modify cil_gen_node() to check to see if the cil_db supports multiple
declarations, and if so, to check whether or not the
repeated symbol is eligible to share the existing, already-stored datum. The
only types considered so far are CIL_TYPE and CIL_TYPEATTRIBUTE, both of
which intall empty datums during AST building, so they automatically return
true.

Test: Build policy with multilpe type and attribute declarations, and
without. Policies are binary-identical.

Signed-off-by: Dan Cashman <dcashman@android.com>
---
 libsepol/cil/include/cil/cil.h   |  1 +
 libsepol/cil/src/cil.c           |  5 +++++
 libsepol/cil/src/cil_build_ast.c | 48 ++++++++++++++++++++++++++++++++++------
 libsepol/cil/src/cil_internal.h  |  1 +
 libsepol/src/libsepol.map.in     |  5 +++++
 secilc/secilc.c                  |  9 +++++++-
 6 files changed, 61 insertions(+), 8 deletions(-)

diff --git a/libsepol/cil/include/cil/cil.h b/libsepol/cil/include/cil/cil.h
index 86117f24..f8cfc3be 100644
--- a/libsepol/cil/include/cil/cil.h
+++ b/libsepol/cil/include/cil/cil.h
@@ -50,6 +50,7 @@ extern int cil_userprefixes_to_string(cil_db_t *db, char **out, size_t *size);
 extern int cil_selinuxusers_to_string(cil_db_t *db, char **out, size_t *size);
 extern int cil_filecons_to_string(cil_db_t *db, char **out, size_t *size);
 extern void cil_set_disable_dontaudit(cil_db_t *db, int disable_dontaudit);
+extern void cil_set_multiple_decls(cil_db_t *db, int multiple_decls);
 extern void cil_set_disable_neverallow(cil_db_t *db, int disable_neverallow);
 extern void cil_set_preserve_tunables(cil_db_t *db, int preserve_tunables);
 extern int cil_set_handle_unknown(cil_db_t *db, int handle_unknown);
diff --git a/libsepol/cil/src/cil.c b/libsepol/cil/src/cil.c
index c02a41a5..3fe68af8 100644
--- a/libsepol/cil/src/cil.c
+++ b/libsepol/cil/src/cil.c
@@ -1691,6 +1691,11 @@ void cil_set_mls(struct cil_db *db, int mls)
 	db->mls = mls;
 }
 
+void cil_set_multiple_decls(struct cil_db *db, int multiple_decls)
+{
+	db->multiple_decls = multiple_decls;
+}
+
 void cil_set_target_platform(struct cil_db *db, int target_platform)
 {
 	db->target_platform = target_platform;
diff --git a/libsepol/cil/src/cil_build_ast.c b/libsepol/cil/src/cil_build_ast.c
index 04492e52..9fc8ab87 100644
--- a/libsepol/cil/src/cil_build_ast.c
+++ b/libsepol/cil/src/cil_build_ast.c
@@ -82,10 +82,33 @@ exit:
 	return rc;
 }
 
+/*
+ * Determine whether or not multiple declarations of the same key can share a
+ * datum, given the new datum and the one already present in a given symtab.
+ */
+int cil_is_datum_multiple_decl(__attribute__((unused)) struct cil_symtab_datum *cur,
+                               __attribute__((unused)) struct cil_symtab_datum *old,
+                               enum cil_flavor f)
+{
+	int rc = CIL_FALSE;
+
+	switch (f) {
+	case CIL_TYPE:
+	case CIL_TYPEATTRIBUTE:
+		/* type and typeattribute statements insert empty datums, ret true */
+		rc = CIL_TRUE;
+		break;
+	default:
+		break;
+	}
+	return rc;
+}
+
 int cil_gen_node(__attribute__((unused)) struct cil_db *db, struct cil_tree_node *ast_node, struct cil_symtab_datum *datum, hashtab_key_t key, enum cil_sym_index sflavor, enum cil_flavor nflavor)
 {
 	int rc = SEPOL_ERR;
 	symtab_t *symtab = NULL;
+	struct cil_symtab_datum *prev;
 
 	rc = __cil_verify_name((const char*)key);
 	if (rc != SEPOL_OK) {
@@ -103,15 +126,26 @@ int cil_gen_node(__attribute__((unused)) struct cil_db *db, struct cil_tree_node
 	if (symtab != NULL) {
 		rc = cil_symtab_insert(symtab, (hashtab_key_t)key, datum, ast_node);
 		if (rc == SEPOL_EEXIST) {
-			cil_log(CIL_ERR, "Re-declaration of %s %s\n", 
-				cil_node_to_string(ast_node), key);
-			if (cil_symtab_get_datum(symtab, key, &datum) == SEPOL_OK) {
-				if (sflavor == CIL_SYM_BLOCKS) {
-					struct cil_tree_node *node = datum->nodes->head->data;
-					cil_tree_log(node, CIL_ERR, "Previous declaration");
+			if (!db->multiple_decls ||
+			    cil_symtab_get_datum(symtab, (hashtab_key_t)key, &prev) != SEPOL_OK ||
+			    !cil_is_datum_multiple_decl(datum, prev, nflavor)) {
+
+				/* multiple_decls not ok, ret error */
+				cil_log(CIL_ERR, "Re-declaration of %s %s\n",
+					cil_node_to_string(ast_node), key);
+				if (cil_symtab_get_datum(symtab, key, &datum) == SEPOL_OK) {
+					if (sflavor == CIL_SYM_BLOCKS) {
+						struct cil_tree_node *node = datum->nodes->head->data;
+						cil_tree_log(node, CIL_ERR, "Previous declaration");
+					}
 				}
+				goto exit;
 			}
-			goto exit;
+			/* multiple_decls is enabled and works for this datum type, add node */
+			cil_list_append(prev->nodes, CIL_NODE, ast_node);
+			ast_node->data = prev;
+			cil_symtab_datum_destroy(datum);
+			free(datum);
 		}
 	}
 
diff --git a/libsepol/cil/src/cil_internal.h b/libsepol/cil/src/cil_internal.h
index 6d6a7d90..136a0049 100644
--- a/libsepol/cil/src/cil_internal.h
+++ b/libsepol/cil/src/cil_internal.h
@@ -316,6 +316,7 @@ struct cil_db {
 	int preserve_tunables;
 	int handle_unknown;
 	int mls;
+	int multiple_decls;
 	int target_platform;
 	int policy_version;
 };
diff --git a/libsepol/src/libsepol.map.in b/libsepol/src/libsepol.map.in
index dd1fec21..aace91a2 100644
--- a/libsepol/src/libsepol.map.in
+++ b/libsepol/src/libsepol.map.in
@@ -56,3 +56,8 @@ LIBSEPOL_1.1 {
 	sepol_kernel_policydb_to_cil;
 	sepol_kernel_policydb_to_conf;
 } LIBSEPOL_1.0;
+
+LIBSEPOL_1.2 {
+  global:
+	cil_set_multiple_decls;
+} LIBSEPOL_1.1;
diff --git a/secilc/secilc.c b/secilc/secilc.c
index f2232e72..0be6975b 100644
--- a/secilc/secilc.c
+++ b/secilc/secilc.c
@@ -63,6 +63,7 @@ static __attribute__((__noreturn__)) void usage(const char *prog)
 	printf("                                 statement if present in the policy\n");
 	printf("  -D, --disable-dontaudit        do not add dontaudit rules to the binary policy\n");
 	printf("  -P, --preserve-tunables        treat tunables as booleans\n");
+	printf("  -m, --multiple-decls           allow some statements to be re-declared\n");
 	printf("  -N, --disable-neverallow       do not check neverallow rules\n");
 	printf("  -G, --expand-generated         Expand and remove auto-generated attributes\n");
 	printf("  -X, --expand-size <SIZE>       Expand type attributes with fewer than <SIZE>\n");
@@ -89,6 +90,7 @@ int main(int argc, char *argv[])
 	int target = SEPOL_TARGET_SELINUX;
 	int mls = -1;
 	int disable_dontaudit = 0;
+	int multiple_decls = 0;
 	int disable_neverallow = 0;
 	int preserve_tunables = 0;
 	int handle_unknown = -1;
@@ -108,6 +110,7 @@ int main(int argc, char *argv[])
 		{"policyversion", required_argument, 0, 'c'},
 		{"handle-unknown", required_argument, 0, 'U'},
 		{"disable-dontaudit", no_argument, 0, 'D'},
+		{"multiple-decls", no_argument, 0, 'm'},
 		{"disable-neverallow", no_argument, 0, 'N'},
 		{"preserve-tunables", no_argument, 0, 'P'},
 		{"output", required_argument, 0, 'o'},
@@ -119,7 +122,7 @@ int main(int argc, char *argv[])
 	int i;
 
 	while (1) {
-		opt_char = getopt_long(argc, argv, "o:f:U:hvt:M:PDNc:GX:", long_opts, &opt_index);
+		opt_char = getopt_long(argc, argv, "o:f:U:hvt:M:PDmNc:GX:", long_opts, &opt_index);
 		if (opt_char == -1) {
 			break;
 		}
@@ -175,6 +178,9 @@ int main(int argc, char *argv[])
 			case 'D':
 				disable_dontaudit = 1;
 				break;
+			case 'm':
+				multiple_decls = 1;
+				break;
 			case 'N':
 				disable_neverallow = 1;
 				break;
@@ -223,6 +229,7 @@ int main(int argc, char *argv[])
 
 	cil_db_init(&db);
 	cil_set_disable_dontaudit(db, disable_dontaudit);
+	cil_set_multiple_decls(db, multiple_decls);
 	cil_set_disable_neverallow(db, disable_neverallow);
 	cil_set_preserve_tunables(db, preserve_tunables);
 	if (handle_unknown != -1) {
-- 
2.14.1.342.g6490525c54-goog