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8899 :: Problem with winapi in nim

• elo (orginal) [2022-02-12T00:50:42+01:00] view original

  Hello, so i want to port a library that I wrote in go and that uses winapi to nim. However, I encountered a problem that I didn't have in go, the same calls in go return expected results but in nim i always get access denied. I can't figure out why this is happening, for example in go this function will return the process name:

  hNDL, err := windows.OpenProcess(windows.PROCESS_QUERY_INFORMATION, false, PID)
          defer windows.CloseHandle(hNDL)
          if err != nil {
                  fmt.Println(err)
          }
          
          var pName uint16
          
          err = windows.GetModuleBaseName(hNDL, 0, &pName, 260)
          if err != nil {
                  fmt.Println(err)
          }
          
          ppName := windows.UTF16PtrToString(&pName)
          
          fmt.Println(ppName)
  
  
  Run

  While in nim the same call will give access denied:

  proc test() =
    var hNDL = OpenProcess(cast[DWORD](PROCESS_QUERY_INFORMATION), FALSE, cast[DWORD](PID))
    defer: CloseHandle(hNDL)
    
    var pName: wstring
    
    if GetModuleBaseNameW(hNDL, 0, pName, 260) == 0:
     echo GetLastError()
    else:
     echo pName
  
  when isMainModule:
    test()
  Run

  I'm running as administrator, additionally I've disabled antivirus (defender) and also tried giving additional permissions (with succes):

  proc test() =
    
    var hToken: HANDLE
    var ldbg: LUID
    var token: TOKEN_PRIVILEGES
    
    var pTknPrev: PTOKEN_PRIVILEGES
    
    if OpenProcessToken(GetCurrentProcess(), cast[DWORD](TOKEN_ADJUST_PRIVILEGES or TOKEN_QUERY), hToken.addr) != 0:
     
     if LookupPrivilegeValue("", SE_DEBUG_NAME, ldbg.addr) != 0:
       echo ldbg
       token.PrivilegeCount = 1
       token.Privileges[0].Luid = ldbg
       token.Privileges[0].Attributes = SE_PRIVILEGE_ENABLED
       if AdjustTokenPrivileges(hToken, FALSE, token.addr, cast[DWORD](sizeof(token)), pTknPrev, cast[PDWORD](0)) != 0:
         echo "ok"
       else:
         echo "fail"
         echo GetLastError()
    else:
        echo GetLastError()
    
    defer: CloseHandle(hToken)
    
    
    var hNDL = OpenProcess(cast[DWORD](PROCESS_QUERY_INFORMATION), FALSE, cast[DWORD](PID))
    defer: CloseHandle(hNDL)
    
    var pName: wstring
    
    if GetModuleBaseNameW(hNDL, 0, pName, 260) == 0:
     echo GetLastError()
    else:
     echo pName
  
  when isMainModule:
    test()
  Run

  And each time I get access denied. I am not trying to read sys process, but for example notepad. Could someone familiar with winapi please direct me what else I should do?

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• Araq (orginal) [2022-02-12T01:12:57+01:00] view original

  Why would

  var pName: wstring
    
    if GetModuleBaseNameW(hNDL, 0, pName, 260) == 0:
  
  Run

  work? Maybe there is no storage associated with pName, I don't know the wstring type.

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• JPLRouge (orginal) [2022-02-12T06:47:24+01:00] view original

  Hello wstring travaille comme string, mais supporte UTF8 etc... C++20 introduces the char8_t portable character type (UTF-8 encoded 8-bit Unicode). In C++20, u8 literal prefixes specify characters or strings of char8_t instead of char

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• Araq (orginal) [2022-02-12T08:06:55+01:00] view original

  Nanu, das ist ja fast schon ein richtiger Satz. Hilft mir aber nicht weiter.

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• guibar (orginal) [2022-02-12T12:10:00+01:00] view original

  According to the docs, GetModuleBaseNameW needs the rights PROCESS_QUERY_INFORMATION and PROCESS_VM_READ. Plus, as @araq mentionned, you should preallocate the string.

  Assuming you use winim, this code should work (works on my machine™)

  ̀

  proc test() =
    var hNDL = OpenProcess(cast[DWORD](PROCESS_QUERY_INFORMATION or PROCESS_VM_READ), FALSE, cast[DWORD](PID))
    defer: CloseHandle(hNDL)
    
    var pName = newWString(260)
    
    if GetModuleBaseNameW(hNDL, 0, pName, 260) == 0:
      echo GetLastError()
    else:
      echo pName
  
  when isMainModule:
    test()
  Run

  How the go version works (in particular the var pName uint16 followed by &pname bit) eludes me completely.

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