Update regex to prevent a chance re.match will hang

src/cfnlint/rules/functions/SubNeeded.py

@@ -3,6 +3,7 @@
 SPDX-License-Identifier: MIT-0
 """
 import re
+import six
 from cfnlint.rules import CloudFormationLintRule
 from cfnlint.rules import RuleMatch
 
@@ -73,7 +74,7 @@ def _match_values(self, searchRegex, cfnelem, path):
                 values.extend(self._match_values(searchRegex, item, pathprop))
         else:
             # Leaf node
-            if isinstance(cfnelem, str) and re.match(searchRegex, cfnelem):
+            if isinstance(cfnelem, six.string_types) and re.match(searchRegex, cfnelem):
                 # Get all variables as seperate paths
                 regex = re.compile(r'(\$\{.*?\.?.*?})')
                 for variable in re.findall(regex, cfnelem):
@@ -110,11 +111,10 @@ def match(self, cfn):
         matches = []
 
         # Generic regex to match a string containing at least one ${parameter}
-        parameter_search = re.compile(r'^.*(\$\{.*\}.*(\$\{.*\}.*)*)$')
+        parameter_search = re.compile(r'^.*(\$\{[a-zA-Z0-9:._]*\}.*)*$')
 
         # Get a list of paths to every leaf node string containing at least one ${parameter}
         parameter_string_paths = self.match_values(parameter_search, cfn)
-
         # We want to search all of the paths to check if each one contains an 'Fn::Sub'
         for parameter_string_path in parameter_string_paths:
             if parameter_string_path[0] in ['Parameters']: