test/bad_chars: ensure our tests could fail

Signed-off-by: Douglas Bagnall <douglas.bagnall@catalyst.net.nz>
Reviewed-by: Ralph Boehme <slow@samba.org>

2 files changed, 36 insertions, 0 deletions

diff --git a/python/samba/tests/source_chars.py b/python/samba/tests/source_chars.py
index 5d107e09574..bfaf6f34ee1 100644
--- a/python/samba/tests/source_chars.py
+++ b/python/samba/tests/source_chars.py
@@ -63,6 +63,7 @@ IGNORED_FILES = {
     'source3/selftest/ktest-krb5_ccache-2',
     'source3/selftest/ktest-krb5_ccache-3',
     'third_party/pep8/testsuite/latin-1.py',
+    'testdata/source-chars-bad.c',
 }
 
 IGNORED_EXTENSIONS = {
@@ -205,6 +206,18 @@ class CharacterTests(TestCase):
                 if is_bad_char(c):
                     self.fail(f"{name} has potentially bad format characters!")
 
+    def test_unexpected_format_chars_do_fail(self):
+        """Test the test"""
+        for name, n_bad in [
+                ('testdata/source-chars-bad.c', 3)
+        ]:
+            fullname = os.path.join(ROOT, name)
+            with open(fullname) as f:
+                s = f.read()
+            chars = set(s)
+            bad_chars = [c for c in chars if is_bad_char(c)]
+            self.assertEqual(len(bad_chars), n_bad)
+
 
 def check_file_text():
     """If called directly as a script, count the found characters."""
diff --git a/testdata/source-chars-bad.c b/testdata/source-chars-bad.c
new file mode 100644
index 00000000000..9b435722e13
--- /dev/null
+++ b/testdata/source-chars-bad.c
@@ -0,0 +1,23 @@
+/*
+ * "Trojan Source"  CVE-2021-42574 test.
+ *
+ * Based on an example from https://lwn.net/Articles/874951/
+ */
+#include <stdio.h>
+
+int main(int argc, char *argv[])
+{
+	int isAdmin = 0;
+
+#if 0
+	/* This is what is really there. */
+
+	/*«RLO» } «LRI»if (isAdmin)«PDI» «LRI» begin admins only */
+	puts("hello admin");
+	/* end admin only «RLO» { «LRI»*/
+#else
+	/*‮ } ⁦if (isAdmin)⁩ ⁦ begin admins only */
+	puts("hello admin");
+	/* end admin only ‮ { ⁦*/
+#endif
+}