C# Signature:

[DllImport("advapi32.dll", SetLastError=true, PreserveSig=true)]
static extern uint LsaOpenPolicy(
   ref LSA_UNICODE_STRING SystemName,
   ref LSA_OBJECT_ATTRIBUTES ObjectAttributes,
   uint DesiredAccess,
   out IntPtr PolicyHandle
);

VB Signature:

    Declare Unicode Function LsaOpenPolicy Lib "advapi32.dll" ( _
    ByRef SystemName As LSA_UNICODE_STRING, _
    ByRef ObjectAttributes As LSA_OBJECT_ATTRIBUTES, _
    ByVal DesiredAccess As Int32, _
    ByRef PolicyHandle As IntPtr) As Int32

User-Defined Types:

None.

Notes:

From the SDK: The LsaOpenPolicy function opens a handle to the Policy object on a local or remote system.

To administer the local security policy of a local or remote system, you must call the LsaOpenPolicy function to establish a session with that system's LSA subsystem. LsaOpenPolicy connects to the LSA of the target system and returns a handle to the Policy object of that system. You can use this handle in subsequent LSA function calls to administer the local security policy information of the target system.

Tips & Tricks:

When done with the handle, call LsaClose

I used a custom marshaler to live a happier life with the "own super special" string type that LSA uses. It marshals LSA_UNICODE_STRINGS to and from normal .NET strings. See "Alternate Sample Code" way below. However I'm quite new to p/invoke and this is my first custom marshaler ever, so please keep your eyes open for problems and bugs with my code. (A problem I had was CleanUpNativeData for data converted from managed to unmanaged aswell as for data converted from unmanaged to managed. Since I didn't allocate the data myself in the latter case my marshaler uses a hash table to keep track of the native data it allocated itself. Don't know if that's the correct way, however. Feel free to mail me at pi AT removethispart frohwalt removethisaswell DOT de for suggestions/corrections. https://www.pinvoke.net/emoticons/regular_smile.gif ) Oh, by the way this also contains an example for LSARetrievePrivateData in case you want to read out some RunAs passwords from the LSA. (My goal is to ultimateley change them, not to read them https://www.pinvoke.net/emoticons/regular_smile.gif )

Sample Code:

public static uint SetRight( string inAccountName, string inPrivilegeName )
{
    uint aWinErrorCode = 0; //contains the last error

    //pointer an size for the SID
    IntPtr aSid = IntPtr.Zero;
    int aSidSize = 0;

    //StringBuilder and size for the domain name
    StringBuilder aDomainName = new StringBuilder();
    int aNameSize = 0;
    //account-type variable for lookup
    int aAccountType = 0;

    //get required buffer size
    LookupAccountName( String.Empty, inAccountName, aSid, ref aSidSize, aDomainName, ref aNameSize, ref aAccountType );

    //allocate buffers
    aDomainName = new StringBuilder( aNameSize );
    aSid = Marshal.AllocHGlobal( aSidSize );

    //lookup the SID for the account
    bool aResult = LookupAccountName( String.Empty, inAccountName, aSid, ref aSidSize, aDomainName, ref aNameSize, ref aAccountType );

    if ( aResult )
    {
        //initialize an empty unicode-string
        LSA_UNICODE_STRING aSystemName = new LSA_UNICODE_STRING();
        //combine all policies
        uint aAccess = (uint)(
            LSA_AccessPolicy.POLICY_AUDIT_LOG_ADMIN |
            LSA_AccessPolicy.POLICY_CREATE_ACCOUNT |
            LSA_AccessPolicy.POLICY_CREATE_PRIVILEGE |
            LSA_AccessPolicy.POLICY_CREATE_SECRET |
            LSA_AccessPolicy.POLICY_GET_PRIVATE_INFORMATION |
            LSA_AccessPolicy.POLICY_LOOKUP_NAMES |
            LSA_AccessPolicy.POLICY_NOTIFICATION |
            LSA_AccessPolicy.POLICY_SERVER_ADMIN |
            LSA_AccessPolicy.POLICY_SET_AUDIT_REQUIREMENTS |
            LSA_AccessPolicy.POLICY_SET_DEFAULT_QUOTA_LIMITS |
            LSA_AccessPolicy.POLICY_TRUST_ADMIN |
            LSA_AccessPolicy.POLICY_VIEW_AUDIT_INFORMATION |
            LSA_AccessPolicy.POLICY_VIEW_LOCAL_INFORMATION
            );
        //initialize a pointer for the policy handle
        IntPtr aPolicyHandle = IntPtr.Zero;

        //these attributes are not used, but LsaOpenPolicy wants them to exists
        LSA_OBJECT_ATTRIBUTES aObjectAttributes = new LSA_OBJECT_ATTRIBUTES();
        aObjectAttributes.Length = 0;
        aObjectAttributes.RootDirectory = IntPtr.Zero;
        aObjectAttributes.Attributes = 0;
        aObjectAttributes.SecurityDescriptor = IntPtr.Zero;
        aObjectAttributes.SecurityQualityOfService = IntPtr.Zero;            

        //get a policy handle
        uint aOpenPolicyResult = LsaOpenPolicy(ref aSystemName, ref aObjectAttributes, aAccess, out aPolicyHandle);
        aWinErrorCode = LsaNtStatusToWinError( aOpenPolicyResult );

        if( aWinErrorCode == Win32Constants.STATUS_SUCCESS )
        {
            //Now that we have the SID an the policy,
            //we can add rights to the account.
            //initialize an unicode-string for the privilege name
            LSA_UNICODE_STRING[] aUserRightsLSAString = new LSA_UNICODE_STRING[1];
            aUserRightsLSAString[0] = new LSA_UNICODE_STRING();
            aUserRightsLSAString[0].Buffer = Marshal.StringToHGlobalUni( inPrivilegeName );
            aUserRightsLSAString[0].Length = ( UInt16 )( inPrivilegeName.Length * UnicodeEncoding.CharSize );
            aUserRightsLSAString[0].MaximumLength = ( UInt16 )( ( inPrivilegeName.Length + 1 ) * UnicodeEncoding.CharSize );

            //add the right to the account
            uint aLSAResult = LsaAddAccountRights( aPolicyHandle, aSid, aUserRightsLSAString, 1 );
            aWinErrorCode = LsaNtStatusToWinError( aLSAResult );

            LsaClose( aPolicyHandle );
        }
        FreeSid( aSid );

    }
    else
    {
        aWinErrorCode = (uint)GetLastError();
    }

    return aWinErrorCode;
}

Alternate Sample Code:

    // This was started from the sample code above (which I originally found on code project).

    [StructLayout(LayoutKind.Sequential)]
    internal struct LSA_UNICODE_STRING
    {
        public UInt16 Length;
        public UInt16 MaximumLength;
        public IntPtr Buffer;

        public void SetTo(string str)
        {
            Buffer = Marshal.StringToHGlobalUni(str);
            Length = (UInt16) ((str.Length+1)*UnicodeEncoding.CharSize);
            MaximumLength = (UInt16) (Length);
            //Console.WriteLine("SetTo: {2} ({3}) Length: {0} Max: {1}", Length, MaximumLength, str, str.Length);
        }

        public override string ToString()
        {
            string str = Marshal.PtrToStringUni(Buffer);
            //Console.WriteLine("ToString: {2} ({3}) Length: {0} Max: {1}", Length, MaximumLength, str, str.Length);
            return str;
        }

        public void Clean()
        {
            //Console.WriteLine("Clean Length: {0} Max: {1}", Length, MaximumLength);
            if (Buffer != IntPtr.Zero)
                Marshal.FreeHGlobal(Buffer);
            Buffer = IntPtr.Zero;
            Length = 0;
            MaximumLength = 0;

        }
    };

    public class LSAStringMarshaler : ICustomMarshaler
    {
        Hashtable myAllocated = new Hashtable();

        private static LSAStringMarshaler marshaler = new LSAStringMarshaler();
        public static ICustomMarshaler GetInstance(string cookie)
        {
            return marshaler;
        }

        public object MarshalNativeToManaged(System.IntPtr pNativeData)
        {
            if (pNativeData != IntPtr.Zero)
            {
                LSA_UNICODE_STRING lus = (LSA_UNICODE_STRING) Marshal.PtrToStructure(pNativeData, typeof(LSA_UNICODE_STRING));
                return lus.ToString();
            }
            return null;
        }

        private int nativeSize = IntPtr.Size + 2 * 2;

        public System.IntPtr MarshalManagedToNative(object ManagedObj)
        {
            LSA_UNICODE_STRING lus = new LSA_UNICODE_STRING();
            IntPtr memory = Marshal.AllocHGlobal(nativeSize);
            myAllocated[memory] = memory;
            //Console.WriteLine("MarshalManagedToNative");
            lus.SetTo((string)ManagedObj);
            Marshal.StructureToPtr(lus, memory, true);
            return memory;
        }

        public void CleanUpManagedData(object ManagedObj)
        {
            //Console.WriteLine("CCC Cleanup Managed Data");            
        }

        public int GetNativeDataSize()
        {
            return nativeSize;
        }

        public void CleanUpNativeData(System.IntPtr pNativeData)
        {            
            //Console.WriteLine("CCC Cleanup Native Data");            

            if (myAllocated.ContainsKey(pNativeData))
            {
                myAllocated.Remove(pNativeData);
                LSA_UNICODE_STRING lus = (LSA_UNICODE_STRING) Marshal.PtrToStructure(pNativeData, typeof(LSA_UNICODE_STRING));
                lus.Clean();
                Marshal.FreeHGlobal(pNativeData);
            }
        }
    }

    public class LSAPolicy : IDisposable
    {
        private IntPtr policy;

        public enum LSA_AccessPolicy : long
        {
            POLICY_VIEW_LOCAL_INFORMATION = 0x00000001L,
            POLICY_VIEW_AUDIT_INFORMATION = 0x00000002L,
            POLICY_GET_PRIVATE_INFORMATION = 0x00000004L,
            POLICY_TRUST_ADMIN = 0x00000008L,
            POLICY_CREATE_ACCOUNT = 0x00000010L,
            POLICY_CREATE_SECRET = 0x00000020L,
            POLICY_CREATE_PRIVILEGE = 0x00000040L,
            POLICY_SET_DEFAULT_QUOTA_LIMITS = 0x00000080L,
            POLICY_SET_AUDIT_REQUIREMENTS = 0x00000100L,
            POLICY_AUDIT_LOG_ADMIN = 0x00000200L,
            POLICY_SERVER_ADMIN = 0x00000400L,
            POLICY_LOOKUP_NAMES = 0x00000800L,
            POLICY_NOTIFICATION = 0x00001000L
        }

        public LSAPolicy() : this (
            LSA_AccessPolicy.POLICY_AUDIT_LOG_ADMIN |
            LSA_AccessPolicy.POLICY_CREATE_ACCOUNT |
            LSA_AccessPolicy.POLICY_CREATE_PRIVILEGE |
            LSA_AccessPolicy.POLICY_CREATE_SECRET |
            LSA_AccessPolicy.POLICY_GET_PRIVATE_INFORMATION |
            LSA_AccessPolicy.POLICY_LOOKUP_NAMES |
            LSA_AccessPolicy.POLICY_NOTIFICATION |
            LSA_AccessPolicy.POLICY_SERVER_ADMIN |
            LSA_AccessPolicy.POLICY_SET_AUDIT_REQUIREMENTS |
            LSA_AccessPolicy.POLICY_SET_DEFAULT_QUOTA_LIMITS |
            LSA_AccessPolicy.POLICY_TRUST_ADMIN |
            LSA_AccessPolicy.POLICY_VIEW_AUDIT_INFORMATION |
            LSA_AccessPolicy.POLICY_VIEW_LOCAL_INFORMATION
            )
        {}

        public LSAPolicy(LSA_AccessPolicy access)
        {
            //initialize an empty unicode-string
            string systemName = null;

            //these attributes are not used, but LsaOpenPolicy wants them to exist
            // (MSDN: "the structure members are not used, initalize them to NULL or zero")
            LSA_OBJECT_ATTRIBUTES ObjectAttributes = new LSA_OBJECT_ATTRIBUTES();
            ObjectAttributes.Length = 0;
            ObjectAttributes.RootDirectory = IntPtr.Zero;
            ObjectAttributes.Attributes = 0;
            ObjectAttributes.SecurityDescriptor = IntPtr.Zero;
            ObjectAttributes.SecurityQualityOfService = IntPtr.Zero;

            //get a policy handle
            UInt32 resultPolicy = LsaOpenPolicy(ref systemName, ref ObjectAttributes, (int)access, out policy);
            int winErrorCode = LsaNtStatusToWinError(resultPolicy);

            if (winErrorCode != 0)
            {
                throw new Win32Exception(winErrorCode, "OpenPolicy failed: ");
            }

        }

        ~LSAPolicy()
        {
            Dispose(false);
        }

        public void Dispose()
        {
            Dispose(true);
            GC.SuppressFinalize(this);
        }

        public void Dispose(bool disposing)
        {
            if (policy != IntPtr.Zero)
            {
                LsaClose(policy);
                policy = IntPtr.Zero;
            }
        }

        public string RetrievePrivateData(string key)
        {
            string result = null;
            UInt32 ntstatus = LsaRetrievePrivateData(policy, key, ref result);
            long winErrorCode = LsaNtStatusToWinError(ntstatus);
            if (winErrorCode != 0)
            {
                throw new Exception("RetreivePrivateData failed: " + winErrorCode);
            }
            return result;
        }

        [DllImport("advapi32.dll")]
        private static extern UInt32 LsaRetrievePrivateData(
            IntPtr policyHandle,
            [MarshalAs(UnmanagedType.CustomMarshaler,MarshalTypeRef=typeof(LSAStringMarshaler))] string KeyName,
            [MarshalAs(UnmanagedType.CustomMarshaler,MarshalTypeRef=typeof(LSAStringMarshaler))] ref string PrivateData
        );

        [DllImport("advapi32.dll")]
        private static extern long LsaClose(IntPtr ObjectHandle);

        [StructLayout(LayoutKind.Sequential)]
        private struct LSA_OBJECT_ATTRIBUTES
        {
            public int Length;
            public IntPtr RootDirectory;
            public LSA_UNICODE_STRING ObjectName;
            public UInt32 Attributes;
            public IntPtr SecurityDescriptor;
            public IntPtr SecurityQualityOfService;
        }

        [DllImport("advapi32.dll", PreserveSig=true)]
        private static extern UInt32 LsaOpenPolicy(
            [MarshalAs(UnmanagedType.CustomMarshaler,MarshalTypeRef=typeof(LSAStringMarshaler))] ref string SystemName,
            ref LSA_OBJECT_ATTRIBUTES ObjectAttributes,
            Int32 DesiredAccess,
            out IntPtr PolicyHandle
            );

        [DllImport("advapi32.dll")]
        private static extern int LsaNtStatusToWinError(long status);

    }

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