Fix pre event check only checking start of flag (#283)

src/plugins/flag/plaintext.py

@@ -13,7 +13,7 @@ def self_check(self):
             return ["property 'flag' must be set!"]
 
         set_flag = self.challenge.flag_metadata["flag"]
-        if not set_flag.startswith(config.get("flag_prefix")):
+        if not set_flag.startswith(config.get("flag_prefix")) or not set_flag.endswith("}"):
             return ["flag does not conform to event flag format!"]
 
         return []

src/plugins/tests.py

@@ -127,6 +127,26 @@ def test_valid_flag(self):
     def test_invalid_flag(self):
         self.assertFalse(self.plugin.check("ractf{b}"))
 
+    def test_self_check_valid_flag(self):
+        self.challenge.flag_metadata["flag"] = "ractf{a}"
+        PlaintextFlagPlugin(self.challenge)
+        self.assertEqual(len(self.plugin.self_check()), 0)
+
+    def test_self_check_no_flag(self):
+        self.challenge.flag_metadata["flag"] = ""
+        PlaintextFlagPlugin(self.challenge)
+        self.assertEqual(len(self.plugin.self_check()), 1)
+
+    def test_self_check_no_flag_prefix(self):
+        self.challenge.flag_metadata["flag"] = "a}"
+        PlaintextFlagPlugin(self.challenge)
+        self.assertEqual(len(self.plugin.self_check()), 1)
+
+    def test_self_check_no_flag_suffix(self):
+        self.challenge.flag_metadata["flag"] = "ractf{a"
+        PlaintextFlagPlugin(self.challenge)
+        self.assertEqual(len(self.plugin.self_check()), 1)
+
 
 class RegexFlagPluginTestCase(APITestCase):
     def setUp(self):