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Posted 23 Feb 2000

Low-level Security Classes

, 1 Mar 2000
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A set of classes to encapsulate the Win32 Security APIs
  • Download demo project - 17 Kb
  • Download source files - 4 Kb
  • If you have ever tried to do something simple like set a security descriptor for a Registry key you know what a pain the Win32 Security APIs can be. The process of initializing the various structures, allocating and deallocating memory and testing for error conditions is tedious and you end up with at least a page and a half of code which is difficult to read and doesn't lend itself to being reused next time you want to do the same thing. There had to be a better way, I thought. So I wrote a set of classes which take care of much of the donkey-work for you.

    All of the classes correspond to the structures used by the low-level Security APIs - ACEs, ACLs, SIDs, TRUSTEEs, Security Descriptors. Their member functions are in most cases the same as the calls you would use when working with the API. The crucial differences are:

    1. Often, a single constructor call is all that is needed to allocate and initialize an object
    2. The classes which need to allocate memory will release it safely when the object goes out of scope.

    Other than that, they are just thin wrappers. You can still get at the underlying objects if you need to, and you can also pass them to any of the API functions expecting a security object.

    The best documentation I can give you is some sample code, so here is an example of how to create a secure Registry key which can be read by any user but only changed by administrators. To compare this with code which does the same thing using only API calls, see Setting a Security Descriptor for a new object in the MSDN library. Notice how much longer it is.

    // Create a Registry key, granting KEY_READ access to everyone and 
    // full control to the Administrators group.
    // Initialize 2 EXPLICIT_ACCESS structures: 1 for Everyone,
    // 1 for Administrators. 
    CSid sidEveryone(CSid::WST_EVERYONE);
    CSid sidAdmins(CSid::WST_LOCALADMINS);
    CTrustee trEveryone(TRUSTEE_IS_WELL_KNOWN_GROUP, sidEveryone);
    CTrustee trAdmins(TRUSTEE_IS_GROUP, sidAdmins);
    ea[0] = CExplicitAccess(KEY_READ, SET_ACCESS, NO_INHERITANCE, trEveryone);
    ea[1] = CExplicitAccess(KEY_ALL_ACCESS, SET_ACCESS, NO_INHERITANCE, trAdmins);		

    Note the constructor for CSid which allows you to create a SID for any of the well-known groups such as Administrators, ordinary users, etc.

    // Create a new ACL and set the EA entries in it
    CAcl acl;
    if(acl.SetEntriesInAcl(2, ea) == ERROR_SUCCESS)
    	// Initialize a security descriptor and add our ACL to it  
    	CSecurityDescriptor sd;
    		TRUE,     // fDaclPresent flag   
    		FALSE))   // not a default DACL 
    		// Initialize a security attributes structure.
    		CSecurityAttributes sa(sd, FALSE);
    		// Use the security attributes to set the security descriptor 
    		// when you create a key.
    		DWORD	dwDisposition;
    		HKEY	hKey;
    		RegCreateKeyEx(HKEY_CURRENT_USER, "mykey1", 0, "", 0, 
    			KEY_READ | KEY_WRITE, sa, &hKey, &dwDisposition); 

    That's it! If you have any suggestions or problems to report, post them here. There are plenty of ways this idea could be extended if you are of an inclination to do so.


    This article has no explicit license attached to it but may contain usage terms in the article text or the download files themselves. If in doubt please contact the author via the discussion board below.

    A list of licenses authors might use can be found here


    About the Author

    Peter Kenyon
    Web Developer
    New Zealand New Zealand
    No Biography provided

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    Comments and Discussions

    QuestionHow can I create a new windows user? Pin
    pengok7-Dec-04 14:17
    memberpengok7-Dec-04 14:17 
    Generaldoes not work :-( Pin
    emmi18-Jul-04 20:44
    memberemmi18-Jul-04 20:44 
    GeneralRe: Please see response of the first message on this board! Pin
    Behzad Ebrahimi24-Jul-04 0:00
    memberBehzad Ebrahimi24-Jul-04 0:00 
    GeneralWrite access right Pin
    Jianping Yan15-May-04 12:36
    memberJianping Yan15-May-04 12:36 
    GeneralWorks fine on NT 4.0, too. Pin
    Anonymous1-Aug-03 10:12
    sussAnonymous1-Aug-03 10:12 
    Generalone Question Pin
    osirix15-Jul-03 6:23
    memberosirix15-Jul-03 6:23 
    Generalchange permissions of an existing key Pin
    M.Pester6-Mar-03 2:07
    sussM.Pester6-Mar-03 2:07 
    Does anyone know how to programatically change permissions of an existing registry key?

    The return code of RegCreateKeyEx(HKEY_LOCAL_MACHINE, sKey, 0, "", 0, KEY_ALL_ACCESS, sa, &hKey, &dwDisposition) is 0, but nothing was changed in the registry.

    The value of dwDisposition says me that I have opened an existing key (==REG_OPENED_EXISTING_KEY).
    If I then try to change the key with RegSetKeySecurity I get return code 87.

    What could be wrong ???

    GeneralRe: change permissions of an existing key Pin
    lesashwad25-Jan-06 10:36
    memberlesashwad25-Jan-06 10:36 
    GeneralRe: change permissions of an existing key Pin
    Atlence31-Jan-06 2:59
    memberAtlence31-Jan-06 2:59 
    Generalregistry security templates Pin
    travisowenjones22-Jan-03 9:57
    susstravisowenjones22-Jan-03 9:57 
    GeneralSlight syntax fix Pin
    John P. Curtis16-Dec-02 17:07
    memberJohn P. Curtis16-Dec-02 17:07 
    Generaluserlist Pin
    Haresh15-May-02 1:36
    memberHaresh15-May-02 1:36 
    GeneralRe: userlist Pin
    Peter_K16-May-02 12:43
    memberPeter_K16-May-02 12:43 
    GeneralRe: userlist Pin
    Haresh16-May-02 19:13
    memberHaresh16-May-02 19:13 
    GeneralIntercepting user lockout Pin
    Ahaz21-Nov-01 6:20
    memberAhaz21-Nov-01 6:20 
    GeneralChanging a directory's security options in Win2000 Pin
    Reza Hemmati11-Jul-01 1:50
    memberReza Hemmati11-Jul-01 1:50 
    GeneralChanging a directory's security options in Win2000 Pin
    Reza Hemmati11-Jul-01 1:50
    memberReza Hemmati11-Jul-01 1:50 
    QuestionHow to validate a username and password? Pin
    Alvaro Mendez12-Jan-01 8:51
    memberAlvaro Mendez12-Jan-01 8:51 
    AnswerRe: How to validate a username and password? Pin
    Todd Jeffreys12-Jan-01 11:02
    memberTodd Jeffreys12-Jan-01 11:02 
    GeneralRe: How to validate a username and password? Pin
    Alvaro Mendez12-Jan-01 12:09
    memberAlvaro Mendez12-Jan-01 12:09 
    GeneralRe: How to validate a username and password? Pin
    Anonymous27-Apr-01 4:30
    memberAnonymous27-Apr-01 4:30 
    GeneralRe: How to validate a username and password? Pin
    the link to codeguru12-Nov-01 2:18
    memberthe link to codeguru12-Nov-01 2:18 
    GeneralInvalid SID error when creating ACL Pin
    Jeff Mcaffee28-Sep-00 11:14
    sussJeff Mcaffee28-Sep-00 11:14 
    GeneralRe: Invalid SID error when creating ACL Pin
    Peter Kenyon28-Sep-00 12:09
    sussPeter Kenyon28-Sep-00 12:09 
    GeneralRe: Invalid SID error when creating ACL Pin
    Anonymous28-Dec-00 12:45
    memberAnonymous28-Dec-00 12:45 

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