Is there a .NET class that can parse CN= strings o

Question

I've got a string that I'm fetching from LDAP for Active Directory group membership and I need to parse it to check if the user is a member of the AD group. Is there a class that can parse this for me?

Example:

CN=Foo Group Name,DC=mydomain,DC=com

Answer 1

I came here to see if we can parse "LDAP://ldap.company.com:389/ou=people,o=company" to protocol, port, baseDN and server FQDN. I tried System.Uri class it worked as excepted.

Answer 2

To answer the parsing question, use PInvoke with DsGetRdnW. For code, see my answer to another question: https://stackoverflow.com/a/11091804/628981.

But it sounds like you're doing it wrong. First, get the SID for your target group:

string targetGroupName = //target group name;
DirectorySearcher dsTargetGroup = new DirectorySearcher();
dsTargetGroup.Filter = string.Format("(sAMAccountName={0})", targetGroupName);
SearchResult srTargetGroup = dsTargetGroup.FindOne();
DirectoryEntry deTargetGroup = srTargetGroup.GetDirectoryEntry();
byte[] byteSid = (byte[])deTargetGroup.Properties["objectSid"].Value;
SecurityIdentifier targetGroupSid = new SecurityIdentifier(byteSid, 0);

Then, it depends on what you have. If the user is running your app (or authenticated to your website/service), then enumerate the SIDs in the token. For example, in desktop apps use WindowsIdentity.GetCurrent().Groups. Otherwise, you'll need to get a DirectoryEntry for the user and then get the tokenAttributes attribute like spoulson suggested:

DirectoryEntry deTargetUser = //target user;
DirectorySearcher dsTargetUser = new DirectorySearcher(deTargetUser);
dsTargetUser.SearchScope = SearchScope.Base; //tokenGroups is a constructed attribute, so have to ask for it while performing a search
dsTargetUser.Filter = "(objectClass=*)"; //this is closest thing I can find to an always true filter
dsTargetUser.PropertiesToLoad.Add("tokenGroups");
SearchResult srTargetUser = dsTargetUser.FindOne();
foreach(byte[] byteGroupSid in srTargetUser.Properties["tokenGroups"])
{
    SecurityIdentifier groupSid = new SecurityIdentifier(byteGroupSid, 0);
    if(groupSid == targetGroupSid)
    {
        //success
    }
}

Just in case you need to get a DirectoryEntry from a SID, you can get the search string by:

public static string GetSIDSearchFilter(SecurityIdentifier sid)
{
    byte[] byteSid = new byte[sid.BinaryLength];
    sid.GetBinaryForm(byteSid, 0);
    return string.Format("(objectSid={0})", BuildFilterOctetString(byteSid));
}

public static string BuildFilterOctetString(byte[] bytes)
{
    StringBuilder sb = new StringBuilder();
    for (int i = 0; i < bytes.Length; i++)
    {
        sb.AppendFormat("\\{0}", bytes[i].ToString("X2"));
    }
    return sb.ToString();
}

Answer 3

Besides, if you query the AD for a group members, you'll be able to compare all of the members' distinguishedName's directly without parsing code through the DirectoryEntry class of the System.DirectoryServices namespace.

Otherwise, I just don't know of such a class somewhere. =)

Hope this helps anyway somehow !

EDIT #1

Here's a link from which I have learned a lot working with the AD and the System.DirectoryServices namespace: Howto: (Almost) Everything In Active Directory via C#

I shall provide you with a sample code in a few days, if you still require it, where I will use the System.DirectoryServices.DirectorySearcher object class to retrieve the members of a group.

I hope this link will help you as it did for me! =)

EDIT #2

Here's the code sample I told you about. This should make it more efficient to query against the AD without having to work bakc and forth the AD.

public IList<string> GetMembers(string groupName) {
    if (string.IsNullOrEmpty(groupName))
        throw new ArgumentNullException("groupName");

    IList<string> members = new List<string>();

    DirectoryEntry root = new DirectoryEntry(@"LDAP://my.domain.com");
    DirectorySearcher searcher = new DirectorySearcher();
    searcher.SearchRoot = root;
    searcher.SearchScope = SearchScope.Subtree;
    searcher.PropertiesToLoad.Add("member");

    searcher.Filter = string.Format("(&(objectClass=group)(sAMAccountName={0}))", groupName);

    SearchResult result = searcher.FindOne();
    DirectoryEntry groupFound = result.GetDirectoryEntry();
    for (int index = 0; index < ((object[])groupFound.Properties["member"].Value).Length; ++index)
        members.Add((string)((object[])groupFound.Properties["member"].Value)[index]);

    return members;

}

Disclaimer : This code is provided as-is. I tested it on my local machine and it works perfectly fine. But since I had to retype it here because I couldn't just copy-paste it, I have perhaps made some mistakes while typing, which I wish didn't occur.

Answer 4

To parse the DistinquishedName you have to pay attention to the escape characters. Here's a method that will parse the string correctly and return a list of key value pairs.

    public static List<KeyValuePair<string, string>> ParseDistinguishedName(string input)
    {
        int i = 0;
        int a = 0;
        int v = 0;
        var attribute = new char[50];
        var value = new char[200];
        var inAttribute = true;
        string attributeString, valueString;
        var names = new List<KeyValuePair<string, string>>();

        while (i < input.Length)
        {
            char ch = input[i++];
            switch(ch)
            {
                case '\\':
                    value[v++] = ch;
                    value[v++] = input[i++];
                    break;
                case '=':
                    inAttribute = false;
                    break;
                case ',':
                    inAttribute = true;
                    attributeString = new string(attribute).Substring(0, a);
                    valueString = new string(value).Substring(0, v);
                    names.Add(new KeyValuePair<string, string>(attributeString, valueString));
                    a = v = 0;
                    break;
                default:
                    if (inAttribute)
                    {
                        attribute[a++] = ch;
                    }
                    else
                    {
                        value[v++] = ch;
                    }
                    break;
            }
        }

        attributeString = new string(attribute).Substring(0, a);
        valueString = new string(value).Substring(0, v);
        names.Add(new KeyValuePair<string, string>(attributeString, valueString));
        return names;
    }

    static void Main(string[] args)
    {
        const string TestString = "CN=BY2STRAKRJOB2,OU=MSNStorage,OU=RESOURCE,OU=PRODUCTION,DC=phx,DC=gbl,STREET=street address,L=locality Name,C=Country Name,UID=user id,STUFF=\\,\\.\\+\"<>;\\=\\0A";

        var names = ParseDistinguishedName(TestString);
        foreach (var pair in names)
        {
            Console.WriteLine("{0} = {1}", pair.Key, pair.Value);
        }
    }

Answer 5

If you don't want to add additional dependencies and just want to parse the string..

This type of string can easily be parsed just using string.Split. To get the CN values, would be something like..

string[] split = "CN=Foo Group Name,DC=mydomain,DC=com".Split(',');
List<string> cnValues = new List<string>();
foreach(string pair in split){
    string[] keyValue=pair.Split('=');
    if(keyValue[0]=="CN")
       cnValues.Add(keyValue[1]);
}

Answer 6

These are called distinguished names.

CodeProject has a parser project that appears to do what you need: http://www.codeproject.com/KB/IP/dnparser.aspx