veggerbyAbuse of FormsAuthentication.HashPasswordForStoringInConfigFile() method?
Posted: July 6, 2008 Filed under: .NET General, ASP.NET | Tags: ASP.NET, formsauthentication, hash, md5 3 Comments »I can’t help but get a annoyingly creepy feeling whenever I see people using FormsAuthentication.HashPasswordForStoringInConfigFile() to generate a hash cipher for a given value (for example here). On the other hand I can’t really decide wether I think it is the method which has a bad name/should be "located" somewhere else or it is the "abuse" of it as it is today.
If we look at the actual implementation of HashPasswordForStoringInConfigFile using Reflector:
{
HashAlgorithm algorithm;
if (password == null)
{
throw new ArgumentNullException("password");
}
if (passwordFormat == null)
{
throw new ArgumentNullException("passwordFormat");
}
if (StringUtil.EqualsIgnoreCase(passwordFormat, "sha1"))
{
algorithm = SHA1.Create();
}
else
{
if (!StringUtil.EqualsIgnoreCase(passwordFormat, "md5"))
{
throw new ArgumentException(SR.GetString("InvalidArgumentValue", new object[] { "passwordFormat" }));
}
algorithm = MD5.Create();
}
return MachineKeySection.ByteArrayToHexString(algorithm.ComputeHash(Encoding.UTF8.GetBytes(password)), 0);
}
The net result of this of course is that you do get the MD5/SHA1 hash of the password or value.
However the method name is HashPasswordForStoringInConfigFile, i.e. the name suggests it is for hashing passwords and further more it is a method of a class called FormsAuthentication… see a pattern!? The name does not suggest it is a generic MD5 method (although the implementation shows it is that).
IMHO using HashPasswordForStoringInConfigFile as a generic MD5 calculation method does nothing but make code less readable and hence harder to maintain. The very, very least a developer can do is to comment the code, but we all know when that’ll happen…
Look at the alternative:
{
MD5 algorithm = MD5.Create();
byte[] data = algorithm.ComputeHash(Encoding.UTF8.GetBytes(value));
string md5 = "";
for (int i = 0; i < data.Length; i++)
{
md5 += data[i].ToString("x2").ToLowerInvariant();
}
return md5;
}
The ONLY problem with not doing this stuff yourself is the conversion from a string and back to a string…
Yes, this might be a little slower due to the string stuff, but you can always "inherit" 
the MachineKeySection.ByteArrayToHexString method.
The point is that using FormsAuthentication.HashPasswordForStoringInConfigFile to calculate all MD5/SHA-1 hash values just because the implementation happens to support this seems wrong. Writing this I think I actually blame Microsoft the most for not providing this method somewhere else and named more appropriately.
That was just a little rant…
agreed!
[...] "response" to my own previous post: two little extension methods that does exactly what "we" need: public static string [...]
[...] it’s a very nice quick and dirty way to hash a password in ASP.NET, although some might criticize its use. If you would like to at a SALT to your password, read this article at [...]