How do I programmatically check modify permissions?
delphi, file-permissions, uac
Solution
I have been using `NT Utilities` for this. Worked very well for me with Win2K/XP/Vista/7
Example from my setup project:
uses unitNTSecurity;
function CheckAccessToFile(DesiredAccess: DWORD; const FileOrDirName: string; ObjectName: string): Boolean;
var
fo: TNTFileObject;
acl: TAccessControlList;
ace: TAccessControlElement;
name: string;
i: integer;
begin
Result := False;
if FileExists(FileOrDirName) or DirectoryExists(FileOrDirName) then
begin
fo := TNTFileObject.Create(FileOrDirName);
acl := TAccessControlList.Create;
try
fo.GetDiscretionaryAccessList(acl);
for i := 0 to acl.ElementCount - 1 do
begin
ace := acl.Element[i];
name := ace.Name; // format is: BUILTIN\Users
if (CompareText(ObjectName, name) = 0) and
(ace.Type_ = aeAccessAllowed) and
(DesiredAccess = ace.Mask) then
begin
Result := True;
Break;
end;
end;
finally
fo.Free;
acl.Free;
end;
end;
end;
Check for `modify`permission:
Result := CheckAccessToFile($001301BF, 'C:\foo', 'BUILTIN\Users');
A note about my answer: The above code answers the OP question:
How do I programmatically check modify permissions
But, if all you need to do, is check that your application is being able to write to a directory, I would not go for this kind of ACL solution, and actually attempt to write a temp file to it, so that I'm 100% sure I can write to it.
I use this code as part of my setup process where I need to grant `modify` permissions for some directories, so this code is used to check if that directory does not already have these permissions - That might be a very different scenario than yours.
There are a few discussions about this issue:
- Get FileSystem Restrictions
- How can I use Delphi to test if a Directory is writeable?
So you need to select your solution according to your actual scenario.
Problem
How do I programmatically check create file permission for folder? Modify file permission? Delete file permission? `GetNamedSecurityInfo` returns that I can write into `C:\Program Files` but UAC says `Access Denied (5)` How can I effective determine access permissions? My code: ``` function GetAccessRights(const FileName: String; ObjectType: SE_OBJECT_TYPE; var Access: Cardinal): Cardinal; var SecDesc: PSECURITY_DESCRIPTOR; pDacl: PACL; Trusteee: TRUSTEE_; begin result := GetNamedSecurityInfo(PChar(FileName), ObjectType, DACL_SECURITY_INFORMATION, nil, nil, @pDacl, nil, SecDesc); if ERROR_SUCCESS = result then begin // the pDacl may be NULL if the object has unrestricted access if pDacl <> nil then begin with Trusteee do begin pMultipleTrustee := nil; MultipleTrusteeOperation := NO_MULTIPLE_TRUSTEE; TrusteeForm := TRUSTEE_IS_NAME; TrusteeType := TRUSTEE_IS_UNKNOWN; ptstrName := 'CURRENT_USER'; end; result := GetEffectiveRightsFromAcl(pDacl^, Trusteee, Access); end else begin Access := $FFFFFFFF; result := ERROR_SUCCESS; end; if SecDesc <> nil then LocalFree(Cardinal(SecDesc)); end; end; ```