I was able to validate credentials using the System.DirectoryServices.Protocols
namespace, thanks to a co-worker. Here’s the code:
// See http://support.microsoft.com/kb/218185 for full list of LDAP error codes
const int ldapErrorInvalidCredentials = 0x31;
const string server = "sd.example.com:636";
const string domain = "sd.example.com";
try
{
using (var ldapConnection = new LdapConnection(server))
{
var networkCredential = new NetworkCredential(_username, _password, domain);
ldapConnection.SessionOptions.SecureSocketLayer = true;
ldapConnection.AuthType = AuthType.Negotiate;
ldapConnection.Bind(networkCredential);
}
// If the bind succeeds, the credentials are valid
return true;
}
catch (LdapException ldapException)
{
// Invalid credentials throw an exception with a specific error code
if (ldapException.ErrorCode.Equals(ldapErrorInvalidCredentials))
{
return false;
}
throw;
}
I’m not thrilled with using a try/catch block to control decisioning logic, but it’s what works. :/