How can I convert from a SID to an account name in C#

Question

I have a C# application that scans a directory and gathers some information. I would like to display the account name for each file. I can do this on the local system by g

Answer 1

Get the current domain:

System.DirectoryServices.ActiveDirectory.Domain.GetCurrentDomain();

Get a directory entry from ldap and the domain name:

DirectoryEntry de = new DirectoryEntry(string.Format("LDAP://{0}", domain));

Get the sid from an ActiveDirectoryMembershipProvider ActiveDirectoryMembershipUser:

ActiveDirectoryMembershipUser user = (ActiveDirectoryMembershipUser)Membership.GetUser();
var sid = (SecurityIdentifier)user.ProviderUserKey;

Get the username from the SecurityIdentifier:

(NTAccount)sid.Translate(typeof(NTAccount));

Get directory search done on an activedirectory with the domain directory entry and username:

DirectorySearcher search = new DirectorySearcher(entry);
        search.Filter = string.Format("(SAMAccountName={0})", username);
        search.PropertiesToLoad.Add("Name");
        search.PropertiesToLoad.Add("displayName");
        search.PropertiesToLoad.Add("company");
        search.PropertiesToLoad.Add("homePhone");
        search.PropertiesToLoad.Add("mail");
        search.PropertiesToLoad.Add("givenName");
        search.PropertiesToLoad.Add("lastLogon");
        search.PropertiesToLoad.Add("userPrincipalName");
        search.PropertiesToLoad.Add("st");
        search.PropertiesToLoad.Add("sn");
        search.PropertiesToLoad.Add("telephoneNumber");
        search.PropertiesToLoad.Add("postalCode");
        SearchResult result = search.FindOne();
        if (result != null)
        {
            foreach (string key in result.Properties.PropertyNames)
            {
                // Each property contains a collection of its own
                // that may contain multiple values
                foreach (Object propValue in result.Properties[key])
                {
                    outputString += key + " = " + propValue + ".<br/>";
                }
            }
        }

Depending on the data in your active directory, you will get a varied response in the output.

Here is a site that has all the user properties I needed:

Answer 2

You can also get account name of special accounts like "Everyone" with code like this that will work regardless of user's language settings:

   SecurityIdentifier everyoneSid = new SecurityIdentifier(WellKnownSidType.WorldSid, null);
   string everyone = everyoneSid.Translate(typeof(System.Security.Principal.NTAccount)).ToString();

Answer 3

System.DirectoryServices.AccountManagement.UserPrincipal class (msdn link) has a static function FindByIdentity to convert an SID to a User object. It should be able to work both against the local machine or an LDAP/Active Directory server. I have only used it against active directory.

Here is an example that I have used in IIS:

// Set the search context to a specific domain in active directory
var searchContext = new PrincipalContext(ContextType.Domain, "YOURDOMAIN", "OU=SomeOU,DC=YourCompany,DC=com");
// get the currently logged in user from IIS
MembershipUser aspUser = Membership.GetUser();
// get the SID of the user (stored in the SecurityIdentifier class)
var sid = aspUser.ProviderUserKey as System.Security.Principal.SecurityIdentifier;
// get the ActiveDirectory user object using the SID (sid.Value returns the SID in string form)
var adUser = UserPrincipal.FindByIdentity(searchContext, IdentityType.Sid, sid.Value);
// do stuff to user, look up group membership, etc.

Answer 4

Great. I cribbed some LookupAccountSid() code from here:

http://www.pinvoke.net/default.aspx/advapi32.LookupAccountSid

And that worked, though I had to provide the host name myself. In the case of a UNC path I can just take the first component of it. When it's a mapped drive, I use this code to convert the path to a UNC one:

http://www.wiredprairie.us/blog/index.php/archives/22

It seems to work, so that's how I'll do it, unless someone comes up with a situation in which the first component of a UNC path isn't the host name...

Thank you all for your help.