From 3679f63daba2b58abcbe22df9f60a722e3db8cab Mon Sep 17 00:00:00 2001
From: Sebastian Pipping <sebastian@pipping.org>
Date: Sun, 22 Sep 2024 01:29:14 +0200
Subject: [PATCH] tests: Cover internalEntityProcessor reentering being finite

The new test asserts that internalEntityProcessor does not loop forever while
processing entities where external entity content references back to internal
entities from the parent document (see &e3; and &e4; below).
We ensure that progress is made after moving the parser from recursive
invocation to a state based processing within function callProcessor.

A version of this test case (originally external-to-Expat, "make run-xmltest")
failed earlier, so we wanted to have a variant of this test (that proved
itself relevant) included within the core test suite ("make check").
---
 expat/tests/misc_tests.c | 43 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 43 insertions(+)

diff --git a/expat/tests/misc_tests.c b/expat/tests/misc_tests.c
index a3823a64..8b8fce5e 100644
--- a/expat/tests/misc_tests.c
+++ b/expat/tests/misc_tests.c
@@ -59,6 +59,9 @@
 #include "handlers.h"
 #include "misc_tests.h"
 
+void XMLCALL accumulate_characters_ext_handler(void *userData,
+                                               const XML_Char *s, int len);
+
 /* Test that a failure to allocate the parser structure fails gracefully */
 START_TEST(test_misc_alloc_create_parser) {
   XML_Memory_Handling_Suite memsuite = {duff_allocator, realloc, free};
@@ -576,6 +579,45 @@ START_TEST(test_misc_stopparser_rejects_unstarted_parser) {
 }
 END_TEST
 
+/* Adaptation of accumulate_characters that takes ExtHdlrData input to work with
+ * test_renter_loop_finite_content below */
+void XMLCALL
+accumulate_characters_ext_handler(void *userData, const XML_Char *s, int len) {
+  ExtHdlrData *const test_data = (ExtHdlrData *)userData;
+  CharData_AppendXMLChars(test_data->storage, s, len);
+}
+
+/* Test that internalEntityProcessor does not re-enter forever;
+ * based on files tests/xmlconf/xmltest/valid/ext-sa/012.{xml,ent} */
+START_TEST(test_renter_loop_finite_content) {
+  CharData storage;
+  CharData_Init(&storage);
+  const char *const text = "<!DOCTYPE doc [\n"
+                           "<!ENTITY e1 '&e2;'>\n"
+                           "<!ENTITY e2 '&e3;'>\n"
+                           "<!ENTITY e3 SYSTEM '012.ent'>\n"
+                           "<!ENTITY e4 '&e5;'>\n"
+                           "<!ENTITY e5 '(e5)'>\n"
+                           "<!ELEMENT doc (#PCDATA)>\n"
+                           "]>\n"
+                           "<doc>&e1;</doc>\n";
+  ExtHdlrData test_data = {"&e4;\n", external_entity_null_loader, &storage};
+  const XML_Char *const expected = XCS("(e5)\n");
+
+  XML_Parser parser = XML_ParserCreate(NULL);
+  assert_true(parser != NULL);
+  XML_SetUserData(parser, &test_data);
+  XML_SetExternalEntityRefHandler(parser, external_entity_oneshot_loader);
+  XML_SetCharacterDataHandler(parser, accumulate_characters_ext_handler);
+  if (_XML_Parse_SINGLE_BYTES(parser, text, (int)strlen(text), XML_TRUE)
+      == XML_STATUS_ERROR)
+    xml_failure(parser);
+
+  CharData_CheckXMLChars(&storage, expected);
+  XML_ParserFree(parser);
+}
+END_TEST
+
 void
 make_miscellaneous_test_case(Suite *s) {
   TCase *tc_misc = tcase_create("miscellaneous tests");
@@ -602,4 +644,5 @@ make_miscellaneous_test_case(Suite *s) {
   tcase_add_test(tc_misc, test_misc_char_handler_stop_without_leak);
   tcase_add_test(tc_misc, test_misc_resumeparser_not_crashing);
   tcase_add_test(tc_misc, test_misc_stopparser_rejects_unstarted_parser);
+  tcase_add_test__if_xml_ge(tc_misc, test_renter_loop_finite_content);
 }