Access Control

#include <Aclapi.h>

int main()
{
    // Create file with multiple flags.
    HANDLE file = CreateFile("d:\\",
                             STANDARD_RIGHTS_WRITE | WRITE_DAC,
                             FILE_SHARE_READ | FILE_SHARE_WRITE,
                             NULL,
                             OPEN_EXISTING,
                             FILE_FLAG_BACKUP_SEMANTICS,                // This flag must be set.
                             NULL);

    // Save old DACL.
    PSECURITY_DESCRIPTOR pSd = NULL;
    PACL pOldDacl = NULL, pNewDacl = NULL;
    GetSecurityInfo(file, SE_FILE_OBJECT, DACL_SECURITY_INFORMATION, NULL, NULL, &pOldDacl, NULL, &pSd);

    // Create new ACE.
    EXPLICIT_ACCESS ea = {};
    ea.grfAccessMode = SET_ACCESS;                                        // Reset or grant or deny, etc.
    ea.grfAccessPermissions = GENERIC_ALL;                                // GENERIC_READ | GENERIC_WRITE | GENERIC_EXECUTE.
    ea.grfInheritance = SUB_CONTAINERS_AND_OBJECTS_INHERIT;               // Whether take effect on sub containers.
    ea.Trustee.TrusteeForm = TRUSTEE_IS_NAME;                             // 'ptstrName' is a name field.
    ea.Trustee.TrusteeType = TRUSTEE_IS_USER;                             // 'ptstrName' is a user name field.
    ea.Trustee.ptstrName = "EveryOne";                                    // User name.
    SetEntriesInAcl(1, &ea, pOldDacl, &pNewDacl);                         // Combine old ACEs and new ACE.

    // Set new DACL.(containing old ACEs)
    SetSecurityInfo(file, SE_FILE_OBJECT, DACL_SECURITY_INFORMATION, NULL, NULL, pNewDacl, NULL);

    // Release resource.
    LocalFree(pNewDacl);
    LocalFree(pSd);
    CloseHandle(file);
    return 0;
}