Setting File Permissions on Windows With C

Thu, 30 Nov 2017 11:07:22 +0100

Edit 2018-01-19

In my original article I have naively supposed that the group names are not localized. This is false. Always use the Well Known Security IDs when manipulating permissions on Windows.

I’ve spent good part of my morning trying to find a way how to set permissions to a particular group.

Finally while digging though Stack Overflow I have found this question which lead to another because of deprecation errors.

My final version of the code to add file read and write permissions to the group Users is this:

#include <Windows.h>
#include <AccCtrl.h>
#include <Aclapi.h>

const char* fileName = "C:/path/to/your_file.txt";

DWORD result = 0;

PACL pDACL = NULL;
PACL pOldDACL = NULL;
PSECURITY_DESCRIPTOR pSD = NULL;
EXPLICIT_ACCESS ea;
PSID pUsersSID = NULL;

const auto cleanup = [pDACL, pOldDACL, pSD, pUsersSID](){
  if (pOldDACL) LocalFree(pOldDACL);
  if (pDACL) LocalFree(pDACL);
  if (pSD) LocalFree(pSD);
  if (pUsersSID) FreeSid(pUsersSID);
};

result = GetNamedSecurityInfo(static_cast<LPTSTR>(fileName), SE_FILE_OBJECT, DACL_SECURITY_INFORMATION, NULL, NULL, &pOldDACL, NULL, &pSD);
if (result != ERROR_SUCCESS) {
  std::cerr << "Failed to get the security info [" << result << "]" << std::endl;
  cleanup();
  return EReturnCode_Error;
}

ZeroMemory(&ea, sizeof(EXPLICIT_ACCESS));

SID_IDENTIFIER_AUTHORITY SIDAuthNT = {SECURITY_NT_AUTHORITY};
if (!AllocateAndInitializeSid(&SIDAuthNT, 2, SECURITY_BUILTIN_DOMAIN_RID, DOMAIN_ALIAS_RID_USERS, 0, 0, 0, 0, 0, 0, &pUsersSID)) {
  std::cerr << "Failed to allocate SID" << std::endl;
  cleanup();
  return EReturnCode_Error;
}

ea.grfAccessPermissions = FILE_GENERIC_WRITE | FILE_GENERIC_READ;
ea.grfAccessMode = SET_ACCESS;
ea.grfInheritance = CONTAINER_INHERIT_ACE | OBJECT_INHERIT_ACE;
ea.Trustee.TrusteeForm = TRUSTEE_IS_SID;
ea.Trustee.TrusteeType = TRUSTEE_IS_WELL_KNOWN_GROUP;
ea.Trustee.ptstrName = reinterpret_cast<LPTSTR>(pUsersSID);

result = SetEntriesInAcl(1, &ea, pOldDACL, &pDACL);
if (result != ERROR_SUCCESS) {
  std::cerr << "Failed to set entries in the access control list [" << result << "]" << std::endl;
  cleanup();
  return EReturnCode_Error;
}

result = SetNamedSecurityInfo(static_cast<LPTSTR>(fileName), SE_FILE_OBJECT, DACL_SECURITY_INFORMATION, NULL, NULL, pDACL, NULL);
if (result != ERROR_SUCCESS) {
  std::cerr << "Failed to set the security info [" << result << "]" << std::endl;
  cleanup();
  return EReturnCode_Error;
}

cleanup();

Note: You will also need to link your program with Advapi32.lib.

My original code follows, do not use this:

const char* fileName = "C:/path/to/your_file.txt";
PACL pDACL = NULL;    
PACL pOldDACL = NULL;
PSECURITY_DESCRIPTOR pSD = NULL;
EXPLICIT_ACCESS ea;

GetNamedSecurityInfo(static_cast<LPTSTR>(fileName), SE_FILE_OBJECT, 
                     DACL_SECURITY_INFORMATION, NULL, NULL, 
                     &pOldDACL, NULL, &pSD);

ZeroMemory(&ea, sizeof(EXPLICIT_ACCESS));

char groupUsersName[6] = {"USERS"};
ea.grfAccessPermissions = FILE_GENERIC_WRITE | FILE_GENERIC_READ;
ea.grfAccessMode = SET_ACCESS;
ea.grfInheritance = CONTAINER_INHERIT_ACE | OBJECT_INHERIT_ACE;
ea.Trustee.TrusteeForm = TRUSTEE_IS_NAME;
ea.Trustee.TrusteeType = TRUSTEE_IS_GROUP;
ea.Trustee.ptstrName = groupUsersName;

SetEntriesInAcl(1, &ea, pOldDACL, &pDACL);

SetNamedSecurityInfo(static_cast<LPTSTR>(fileName), SE_FILE_OBJECT, 
                     DACL_SECURITY_INFORMATION, NULL, NULL, pDACL, NULL);

MiKTeX 2.9 and Windows 10 package installation woes

Wed, 02 Aug 2017 15:42:08 +0000

Today my MiKTeX installation stopped installing packages on the fly. After trying to install packages through Package Manager I found out that this did not work either. The error that I have obtained is this:

The executed process did not succeed.
fileName="C:\Program Files (x86)\MiKTeX 2.9\MiKTeX\bin\initexmf.exe", arguments=" --mklinks --mkmaps", exitCode="1"

I googled around and found out that this might be a problem with the installation folder not being accessible and the suggested solution was to install MiKTeX somewhere else (or just for the local user). This was not an option for me as a toolchain that does not depend only on me requires the latex binary to be in the default folder.

My solution was to go to the C:\Program Files (x86)\MiKTeX 2.9 folder properties and changing the Users permissions to Full Control. Not extremely secure but at least now I can build my documentation.

Windows on yozy//NET

Setting File Permissions on Windows With C

MiKTeX 2.9 and Windows 10 package installation woes