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Check directory for write access by current user

Posted on 2008-10-01
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Last Modified: 2013-11-20
How do use MFC to check if the current user has write access to a directory?
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Question by:steenpat
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4 Comments
 
LVL 86

Accepted Solution

by:
jkr earned 250 total points
ID: 22618586
You can use the following code:
#include <windows.h>
#include <svrapi.h>
#include <stdio.h>
 
BOOL IsAccessPermitted(LPCTSTR pszFolder) {
 
          HANDLE hToken;
	  // AccessCheck() variables
	  DWORD           dwAccessDesired;
	  PRIVILEGE_SET   PrivilegeSet;
	  DWORD           dwPrivSetSize;
	  DWORD           dwAccessGranted;
	  BOOL            fAccessGranted = FALSE;
	  GENERIC_MAPPING GenericMapping;
 
          SECURITY_INFORMATION si = (SECURITY_INFORMATION)( OWNER_SECURITY_INFORMATION
            | GROUP_SECURITY_INFORMATION
            | DACL_SECURITY_INFORMATION);
 
 
	  PSECURITY_DESCRIPTOR psdSD = NULL;
	  DWORD dwNeeded;
 
	  GetFileSecurity(pszFolder,si,NULL,0,&dwNeeded);
 
 
	  psdSD = (PSECURITY_DESCRIPTOR) new BYTE[dwNeeded];
 
	  if (!GetFileSecurity(pszFolder,si,psdSD,dwNeeded,&dwNeeded)) {
 
              printf("GetFileSecurity\n");
          }
 
      // AccessCheck() requires an impersonation token.
      ImpersonateSelf(SecurityImpersonation);
 
      OpenThreadToken(GetCurrentThread(), TOKEN_ALL_ACCESS, TRUE, 
            &hToken);
 
      // Using AccessCheck(), there are two different things we could do:
      // 
      // 1. See if we have Read/Write access to the object.
      // 
      dwAccessDesired = ACCESS_READ;
 
      // Initialize generic mapping structure to map all.
      memset(&GenericMapping, 0xff, sizeof(GENERIC_MAPPING));
      GenericMapping.GenericRead = ACCESS_READ;
      GenericMapping.GenericWrite = ACCESS_WRITE;
      GenericMapping.GenericExecute = 0;
      GenericMapping.GenericAll = ACCESS_READ | ACCESS_WRITE;
 
      // This only does something if we want to use generic access
      // rights, like GENERIC_ALL, in our call to AccessCheck().
      MapGenericMask(&dwAccessDesired, &GenericMapping);
 
      dwPrivSetSize = sizeof(PRIVILEGE_SET);
 
      printf("calling 'AccessCheck()'...\n");
 
      // Make the AccessCheck() call.
      if (!AccessCheck(psdSD, hToken, dwAccessDesired, &GenericMapping,
            &PrivilegeSet, &dwPrivSetSize, &dwAccessGranted, 
            &fAccessGranted)){
 
              printf("AccessCheck: %d\n",GetLastError());
          }
 
      printf("... 'AccessCheck()' succeeded\n");
      delete [] psdSD;
 
  return fAccessGranted;
}
 
void main () {
 
    BOOL bRes = IsAccessPermitted("c:\\Windows\\notepad.exe");
 
    printf("permitted: %s\n", bRes ? "Yes" :  "No");
 
}

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LVL 14

Assisted Solution

by:wayside
wayside earned 250 total points
ID: 22618636
Quick and dirty method would be to just create a file in the directory. If it succeeds, you have write access; if not, you don't.

CString mydir = "c:/windows/system32";

CString tempName = mydir + "/mytemp.foo";
CFile tempFile;

BOOL bOpenOK = tempFile.Open(tempName, CFile::modeCreate | CFile::modeWrite);
if (bOpenOK == TRUE) {
  // success! clean up.
  tempFile.Close();
  CFile::Remove(tempName);
}

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LVL 17

Expert Comment

by:CSecurity
ID: 22623330
try to create a directory using CreateDirectory of try to create a file using CreateFile API function.
if one of above functions failed, check error reason using GetLastError() API to get error code.
if(GetLastError() == ERROR_ACCESS_DENIED) // or if(GetLastError() == 5)
//means that access denied
as "Wayside"s comment: quick and dirty way ;)
Regards
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Author Comment

by:steenpat
ID: 22996449
I would like to comment that RevertToSelf is necessary at the bottom of this function otherwise it keeps running in the context of the client and this is undesirable. It caused issues with my application until I figured this out. I called RevertToSelf, and then CloseHandle(hToken) and this resolved issues.
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