How to create WindowsIdentity/WindowsPrincipal from username in DOMAIN\user format

Question

The WindowsIdentity(string) constructor requires the username to be in [email protected] format. But in my case I get the usernames from a DB in the old DOMAIN\user format (and then have to check their Windows role membership).

What is the best way of creating WindowsPrincipal from the old style (sAMAccountName) username?

Answer 1

It does seem that there is no way of converting the username format without involving a query to Active Directory. Since that is the case there is no need to create WindowsPrincipal for checking the group membership since that would probably need yet another connection to AD.

By using the System.DirectoryServices.AccountManagement namespace you can both get the UPN of the user and check the group membership.

string accountName = @"DOMAIN\user";
var groupNames = new[] { "DOMAIN\Domain Users", "DOMAIN\Group2" }; // the groups that we need to verify if the user is member of

// cannot create WindowsIdentity because it requires username in form [email protected] but the passed value will be DOMAIN\user.
using (var pc = new PrincipalContext(System.DirectoryServices.AccountManagement.ContextType.Domain, Environment.UserDomainName))
{
    using (var p = UserPrincipal.FindByIdentity(pc, accountName))
    {
        // if the account does not exist or is not an user account
        if (p == null)
            return new string[0];

        // if you need just the UPN of the user, you can use this
        ////return p.UserPrincipalName;

        // find all groups the user is member of (the check is recursive).
        // Guid != null check is intended to remove all built-in objects that are not really AD gorups.
        // the Sid.Translate method gets the DOMAIN\Group name format.
        var userIsMemberOf = p.GetAuthorizationGroups().Where(o => o.Guid != null).Select(o => o.Sid.Translate(typeof(NTAccount)).ToString());

        // use a HashSet to find the group the user is member of.
        var groups = new HashSet<string>(userIsMemberOf, StringComparer.OrdinalIgnoreCase);
        groups.IntersectWith(groupNames);

        return groups;
    }
}

Answer 2

I tooked the DsCrackNames on example pinvoke.net and modified it to convert from nt4 name to UPN. Its kinda sloppy and you might want to clean up. For this it has to hit the DS too. They have the DS_NAME_FLAG_SYNTACTICAL_ONLY flag which can be used to not hit the directory but I dont think that will work here.

class Entry
{

    const uint NO_ERROR = 0;
    [DllImport("ntdsapi.dll", CharSet = CharSet.Auto)]
    static public extern uint DsCrackNames(
      IntPtr hDS,
      DS_NAME_FLAGS flags,
      DS_NAME_FORMAT formatOffered,
      DS_NAME_FORMAT formatDesired,
      uint cNames,
      string[] rpNames,
      out IntPtr ppResult  // PDS_NAME_RESULT
      );

    [DllImport("ntdsapi.dll", CharSet = CharSet.Auto)]
    static public extern void DsFreeNameResult(IntPtr pResult /* DS_NAME_RESULT* */);

    public enum DS_NAME_ERROR
    {
        DS_NAME_NO_ERROR = 0,

        // Generic processing error.
        DS_NAME_ERROR_RESOLVING = 1,

        // Couldn't find the name at all - or perhaps caller doesn't have
        // rights to see it.
        DS_NAME_ERROR_NOT_FOUND = 2,

        // Input name mapped to more than one output name.
        DS_NAME_ERROR_NOT_UNIQUE = 3,

        // Input name found, but not the associated output format.
        // Can happen if object doesn't have all the required attributes.
        DS_NAME_ERROR_NO_MAPPING = 4,

        // Unable to resolve entire name, but was able to determine which
        // domain object resides in.  Thus DS_NAME_RESULT_ITEM?.pDomain
        // is valid on return.
        DS_NAME_ERROR_DOMAIN_ONLY = 5,

        // Unable to perform a purely syntactical mapping at the client
        // without going out on the wire.
        DS_NAME_ERROR_NO_SYNTACTICAL_MAPPING = 6,

        // The name is from an external trusted forest.
        DS_NAME_ERROR_TRUST_REFERRAL = 7

    }

    [Flags]
    public enum DS_NAME_FLAGS
    {
        DS_NAME_NO_FLAGS = 0x0,

        // Perform a syntactical mapping at the client (if possible) without
        // going out on the wire.  Returns DS_NAME_ERROR_NO_SYNTACTICAL_MAPPING
        // if a purely syntactical mapping is not possible.
        DS_NAME_FLAG_SYNTACTICAL_ONLY = 0x1,

        // Force a trip to the DC for evaluation, even if this could be
        // locally cracked syntactically.
        DS_NAME_FLAG_EVAL_AT_DC = 0x2,

        // The call fails if the DC is not a GC
        DS_NAME_FLAG_GCVERIFY = 0x4,

        // Enable cross forest trust referral
        DS_NAME_FLAG_TRUST_REFERRAL = 0x8

    }

    public enum DS_NAME_FORMAT
    {
        // unknown name type
        DS_UNKNOWN_NAME = 0,

        // eg: CN=User Name,OU=Users,DC=Example,DC=Microsoft,DC=Com
        DS_FQDN_1779_NAME = 1,

        // eg: Example\UserN
        // Domain-only version includes trailing '\\'.
        DS_NT4_ACCOUNT_NAME = 2,

        // Probably "User Name" but could be something else.  I.e. The
        // display name is not necessarily the defining RDN.
        DS_DISPLAY_NAME = 3,

        // obsolete - see #define later
        // DS_DOMAIN_SIMPLE_NAME = 4,

        // obsolete - see #define later
        // DS_ENTERPRISE_SIMPLE_NAME = 5,

        // String-ized GUID as returned by IIDFromString().
        // eg: {4fa050f0-f561-11cf-bdd9-00aa003a77b6}
        DS_UNIQUE_ID_NAME = 6,

        // eg: example.microsoft.com/software/user name
        // Domain-only version includes trailing '/'.
        DS_CANONICAL_NAME = 7,

        // eg: [email protected]
        DS_USER_PRINCIPAL_NAME = 8,

        // Same as DS_CANONICAL_NAME except that rightmost '/' is
        // replaced with '\n' - even in domain-only case.
        // eg: example.microsoft.com/software\nuser name
        DS_CANONICAL_NAME_EX = 9,

        // eg: www/[email protected] - generalized service principal
        // names.
        DS_SERVICE_PRINCIPAL_NAME = 10,

        // This is the string representation of a SID.  Invalid for formatDesired.
        // See sddl.h for SID binary <--> text conversion routines.
        // eg: S-1-5-21-397955417-626881126-188441444-501
        DS_SID_OR_SID_HISTORY_NAME = 11,

        // Pseudo-name format so GetUserNameEx can return the DNS domain name to
        // a caller.  This level is not supported by the DS APIs.
        DS_DNS_DOMAIN_NAME = 12
    }

    [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Auto)]
    public struct DS_NAME_RESULT_ITEM
    {
        public DS_NAME_ERROR status;
        public string pDomain;
        public string pName;
    }

    [DllImport("ntdsapi.dll", CharSet = CharSet.Auto)]
    static public extern uint DsBind(
      string DomainControllerName,      // in, optional
      string DnsDomainName,         // in, optional
      out IntPtr phDS);

    [DllImport("ntdsapi.dll", CharSet = CharSet.Auto)]
    static public extern uint DsUnBind(ref IntPtr phDS);

    [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Auto)]
    public struct DS_NAME_RESULT
    {
        public uint cItems;
        public IntPtr rItems; // PDS_NAME_RESULT_ITEM
    }

    [STAThread]
    static void Main(string[] args)
    {
        // Bind to default global catalog
        IntPtr hDS;
        uint err = DsBind(null, null, out hDS);
        if (err != NO_ERROR)
        {
            Console.WriteLine("Error on DsBind : {0}", err);
            return;
        }
        // Crack the currently logged on name
        try
        {
            string[] names = new string[] { System.Security.Principal.WindowsIdentity.GetCurrent().Name };
            DS_NAME_RESULT_ITEM[] results =
              HandleDsCrackNames(hDS, DS_NAME_FLAGS.DS_NAME_NO_FLAGS, DS_NAME_FORMAT.DS_NT4_ACCOUNT_NAME, DS_NAME_FORMAT.DS_USER_PRINCIPAL_NAME, names);
            foreach (DS_NAME_RESULT_ITEM result in results)
            {
                Console.WriteLine("Result : {0}\r\nDomain : {1}\r\nName : {2}", result.status, result.pDomain, result.pName);
            }
        }
        finally
        {
            DsUnBind(ref hDS);
        }
    }

    /// <summary>
    /// A wrapper function for the DsCrackNames OS call
    /// </summary>
    /// <param name="hDS">DsBind handle</param>
    /// <param name="flags">Flags controlling the process</param>
    /// <param name="formatOffered">Format of the names</param>
    /// <param name="formatDesired">Desired format for the names</param>
    /// <param name="names">The names to crack</param>
    /// <returns>The crack result</returns>
    public static DS_NAME_RESULT_ITEM[] HandleDsCrackNames(IntPtr hDS, DS_NAME_FLAGS flags, DS_NAME_FORMAT formatOffered, DS_NAME_FORMAT formatDesired, string[] names)
    {
        IntPtr pResult;
        DS_NAME_RESULT_ITEM[] ResultArray;
        uint err = DsCrackNames(
      hDS,
      flags,
      formatOffered,
      formatDesired,
      (uint)((names == null) ? 0 : names.Length),
      names,
      out pResult);
        if (err != NO_ERROR)
            throw new System.ComponentModel.Win32Exception((int)err);
        try
        {
            // Next convert the returned structure to managed environment
            DS_NAME_RESULT Result = new DS_NAME_RESULT();
            Result.cItems = (uint)Marshal.ReadInt32(pResult);
            Result.rItems = Marshal.ReadIntPtr(pResult, Marshal.OffsetOf(typeof(DS_NAME_RESULT), "rItems").ToInt32());
            IntPtr curptr = Result.rItems;
            ResultArray = new DS_NAME_RESULT_ITEM[Result.cItems];
            for (int index = 0; index < (int)Result.cItems; index++)
            {
                ResultArray[index] = (DS_NAME_RESULT_ITEM)Marshal.PtrToStructure(curptr, typeof(DS_NAME_RESULT_ITEM));
                curptr = (IntPtr)((int)curptr + Marshal.SizeOf(ResultArray[index]));
            }
        }
        finally
        {
            DsFreeNameResult(pResult);
        }
        return ResultArray;
    }

}

Answer 3

This works fine but involves a query to active directory/SAM store (depending on the context)...

private WindowsIdentity GetWindowsIdentity(
  string userName)
{
  using (var user =
    UserPrincipal.FindByIdentity(
      UserPrincipal.Current.Context,
      IdentityType.SamAccountName,
      userName
      ) ??
    UserPrincipal.FindByIdentity(
      UserPrincipal.Current.Context,
      IdentityType.UserPrincipalName,
      userName
      ))
  {
    return user == null
      ? null
      : new WindowsIdentity(user.UserPrincipalName);
  }
}