share.c

#include <windows.h>
#include <AccCtrl.h>
#include <Aclapi.h>
#include <WinNt.h>
#include <stdio.h>

#define SafeRelease(x) if (x != NULL) { LocalFree((HLOCAL)x); x = NULL; }

DWORD AddAceToObjectsSecurityDescriptor (
    LPTSTR pszObjName,          // name of object
    SE_OBJECT_TYPE ObjectType,  // type of object
    LPTSTR pszTrustee,          // trustee for new ACE
    TRUSTEE_FORM TrusteeForm,   // format of trustee structure
    DWORD dwAccessRights,       // access mask for new ACE
    ACCESS_MODE AccessMode,     // type of ACE
    DWORD dwInheritance         // inheritance flags for new ACE
) 
{
    DWORD dwRes = 0;
    PACL pOldDACL = NULL, pNewDACL = NULL;
    PSECURITY_DESCRIPTOR pSD = NULL;
    EXPLICIT_ACCESS ea;
    BOOL success;

    if (NULL == pszObjName)  {
        return ERROR_INVALID_PARAMETER;
    }

    // Get a pointer to the existing DACL.

    dwRes = GetNamedSecurityInfo(pszObjName, ObjectType, 
          DACL_SECURITY_INFORMATION,
          NULL, NULL, &pOldDACL, NULL, &pSD);
    if (ERROR_SUCCESS != dwRes) {
        printf( "GetNamedSecurityInfo Error %u\n", dwRes );
        goto Cleanup; 
    }  

    // Initialize an EXPLICIT_ACCESS structure for the new ACE. 

    ZeroMemory(&ea, sizeof(EXPLICIT_ACCESS));
    ea.grfAccessPermissions = dwAccessRights;
    ea.grfAccessMode = AccessMode;
    ea.grfInheritance= dwInheritance;
    ea.Trustee.TrusteeForm = TrusteeForm;
    ea.Trustee.ptstrName = pszTrustee;

    // Create a new ACL that merges the new ACE
    // into the existing DACL.

    dwRes = SetEntriesInAcl(1, &ea, pOldDACL, &pNewDACL);
    if (ERROR_SUCCESS != dwRes)  {
        printf( "SetEntriesInAcl Error %u\n", dwRes );
        goto Cleanup; 
    }  

    // Convert the security descriptor to absolute format

    VOID    *pAbsoluteSD = NULL; 
    DWORD   AbsoluteSDSize = 0;
    VOID    *pDacl = NULL;
    DWORD   DaclSize = 0;
    VOID    *pSacl = NULL;
    DWORD   SaclSize = 0;
    VOID    *pOwner = NULL;
    DWORD   OwnerSize = 0;
    VOID    *pGroup = NULL;
    DWORD   GroupSize = 0;
    MakeAbsoluteSD(
      pSD,
      (PSECURITY_DESCRIPTOR)pAbsoluteSD,
      &AbsoluteSDSize,
      (PACL)pDacl,
      &DaclSize,
      (PACL)pSacl,
      &SaclSize,
      (PSID)pOwner,
      &OwnerSize,
      (PSID)pGroup,
      &GroupSize
    ); // will return false which is ok, we just want the sizes

    pAbsoluteSD = (PSECURITY_DESCRIPTOR)LocalAlloc(0,AbsoluteSDSize);
    if(!pAbsoluteSD) {
      dwRes = GetLastError();
      printf("LocalAlloc Error %u\n", dwRes);
      goto Cleanup;
    }
    pDacl = (PACL)LocalAlloc(0,DaclSize);
    if(!pDacl) {
      dwRes = GetLastError();
      printf("LocalAlloc Error %u\n", dwRes);
      goto Cleanup;
    }
    pSacl = (PACL)LocalAlloc(0,SaclSize);
    if(!pSacl) {
      dwRes = GetLastError();
      printf("LocalAlloc Error %u\n", dwRes);
      goto Cleanup;
    }
    pOwner = (PSID)LocalAlloc(0,OwnerSize);
    if(!pOwner) {
      dwRes = GetLastError();
      printf("LocalAlloc Error %u\n", dwRes);
      goto Cleanup;
    }
    pGroup = (PSID)LocalAlloc(0,GroupSize);
    if(!pGroup) {
      dwRes = GetLastError();
      printf("LocalAlloc Error %u\n", dwRes);
      goto Cleanup;
    }

    success = MakeAbsoluteSD(
      pSD,
      (PSECURITY_DESCRIPTOR)pAbsoluteSD,
      &AbsoluteSDSize,
      (PACL)pDacl,
      &DaclSize,
      (PACL)pSacl,
      &SaclSize,
      (PSID)pOwner,
      &OwnerSize,
      (PSID)pGroup,
      &GroupSize
    ); // will return false which is ok, we just want the sizes
    if (!success) {
        dwRes = GetLastError();
        printf( "MakeAbsoluteSD Error %u\n", dwRes );
        goto Cleanup; 
    }

    // Attach the new ACL as the object's DACL.

    // dwRes = SetNamedSecurityInfo(pszObjName, ObjectType, 
    //       DACL_SECURITY_INFORMATION,
    //        NULL, NULL, pNewDACL, NULL);
    // if (ERROR_SUCCESS != dwRes)  {
    //     printf( "SetNamedSecurityInfo Error %u\n", dwRes );
    //     goto Cleanup; 
    // }  

    success = SetSecurityDescriptorDacl((PSECURITY_DESCRIPTOR)pAbsoluteSD, TRUE /* specifying dacl */, pNewDACL, FALSE /* not defaulted */);
    if (!success)  {
        dwRes = GetLastError();
        printf( "SetSecurityDescriptorDacl Error %u\n", dwRes );
        goto Cleanup; 
    }  

    success = SetFileSecurity(pszObjName, DACL_SECURITY_INFORMATION, (PSECURITY_DESCRIPTOR)pAbsoluteSD);
    if (!success)  {
        dwRes = GetLastError();
        printf( "SetFileSecurity Error: %u\n", dwRes);
        goto Cleanup; 
    }  

    Cleanup:

        SafeRelease(pSD);
        SafeRelease(pNewDACL);

        return dwRes;
}

int main () {
  fprintf(stderr, "Hi there\n");

  /////////////////////////////////////
  // Sharing
  /////////////////////////////////////

  // DWORD dwRes = AddAceToObjectsSecurityDescriptor(
  //   "C:\\Users\\amos\\.electron", // pszObjName
  //   SE_FILE_OBJECT, // ObjectType
  //   "itch-player-59922ff6", // pszTrustee
  //   TRUSTEE_IS_NAME,
  //   GENERIC_READ,
  //   GRANT_ACCESS,
  //   0
  // );

  /////////////////////////////////////
  // Unsharing
  /////////////////////////////////////

  DWORD dwRes = AddAceToObjectsSecurityDescriptor(
    "C:\\Users\\amos\\.electron", // pszObjName
    SE_FILE_OBJECT, // ObjectType
    "itch-player-59922ff6", // pszTrustee
    TRUSTEE_IS_NAME,
    GENERIC_READ,
    REVOKE_ACCESS,
    0
  );
  if (ERROR_SUCCESS != dwRes)  {
      printf( "AddAceToObjectsSecurityDescriptor Error %u\n", dwRes );
      return 1; 
  }  

  return 0;
}