CVE-2020-36620: Protect against DOS attacks made possible by parsing random invalid e… · Brondahl/EnumStringValues@c0fc780

@@ -269,15 +269,12 @@ private static List<StringValueAttribute> GetStringValuesWithPreferences_Uncache

{

var enumTypeObject = typeof(TEnumType);

var typeAppropriateDictionary = parsedEnumStringsDictionaryByType.GetOrAdd(enumTypeObject, (x) => new ConcurrentDictionary<string, Enum>());

var typeAppropriateDictionary = parsedEnumStringsDictionaryByType.GetOrAdd(

enumTypeObject,

(x) => BuildCacheDictionaryForParseStringValue<TEnumType>()

);

var cachedValue = typeAppropriateDictionary.GetOrAdd(lowerStringValue, (str) =>

{

var parseSucceededForDictionary = TryParseStringValueToEnum_Uncached<TEnumType>(lowerStringValue, out var parsedValueForDictionary);

return parseSucceededForDictionary ? (Enum) parsedValueForDictionary : null;

});

if (cachedValue != null)

if (typeAppropriateDictionary.TryGetValue(lowerStringValue, out var cachedValue))

{

parsedValue = (TEnumType)cachedValue;

return true;

@@ -292,6 +289,25 @@ private static List<StringValueAttribute> GetStringValuesWithPreferences_Uncache

/// <summary> Cache for <see cref="TryParseStringValueToEnum{TEnumType}"/> </summary>

private static ConcurrentDictionary<Type, ConcurrentDictionary<string, Enum>> parsedEnumStringsDictionaryByType;

private static ConcurrentDictionary<string, Enum> BuildCacheDictionaryForParseStringValue<TEnumType>() where TEnumType : System.Enum

{

var dict = new ConcurrentDictionary<string, Enum>();

foreach (var enumValue in EnumerateValues<TEnumType>())

{

foreach (var enumString in GetStringValues<TEnumType>(enumValue))

{

// Add to the dictionary, just overwriting if the string is already present.

// This overwrite is legitimate, because we’ve declared parsing a duplicate string definition to be `undefined behaviour`.

dict.AddOrUpdate(enumString.ToLower(), enumValue, ((repeatedString, previousEnumValue) => enumValue));

}

}

return dict;

}

private static bool TryParseStringValueToEnum_Uncached<TEnumType>(this string lowerStringValue, out TEnumType parsedValue) where TEnumType : System.Enum

{

foreach (var enumValue in EnumerateValues<TEnumType>())