Alternate command tail algo.

[hutch--]

PowerBASIC has a COMMAND$ command that works fine in most instances, here is an alternative algorithm that can be called with either basic dynamic string or as a zero terminated string. Note that neither solve a problem with the API CreateProcess() where the file name and command tail are not parsed correctly. The assembler code was written in MASM and directly ported to PowerBASIC.

Code Select Expand


' ¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤

    #include "\basic\include\win32api.inc"

' ¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤

FUNCTION PBmain as LONG

    LOCAL pCmt as ASCIIZ PTR

'     cmd$ = command$
'
'     If cmd$ = "" Then
'       StdOut "No command tail"
'     Else
'       StdOut cmd$                   ' display basic string
'     End If
'
'     If cmd$ = "" Then
'       StdOut "No command tail"
'     Else
'       StdOut cmd$                   ' display basic string
'     End If

  ' --------------------
  ' BASIC string version
  ' --------------------
    cmd$ = GetCmdTail

    If cmd$ = "" Then
      StdOut "No command tail"
    Else
      StdOut cmd$                   ' display basic string
    End If

  ' ------------------------------
  ' zero terminated string version
  ' ------------------------------
    pCmt = szCmdTail

    If pCmt = 0 Then
      StdOut "No command tail"
    Else
      StdOut @pCmt                  ' display zero terminated string
      GlobalFree pCmt
    End If

End FUNCTION

' ¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤

FUNCTION szCmdTail() as DWORD

  ' -----------------------------------------------------------------------
  ' If command tail is not empty and the memory pointer is returned, it
  ' must be freed in the same scope as the caller with theAPI GlobalFree().
  ' -----------------------------------------------------------------------

    LOCAL lCmd as DWORD
    LOCAL pCmd as DWORD
    LOCAL pBuf as DWORD

    pCmd = GetCommandLine()

    ! push pCmd             ; push cmdline pointer onto stack
    ! call slen             ; call the short lenth function
    ! mov lCmd, eax         ; allocate this much memory

    pBuf = GlobalAlloc(%GMEM_FIXED or %GMEM_ZEROINIT, lCmd+16)

    ! push pBuf
    ! push pCmd
    ! call cmdtail
    ! test eax, eax         ; check if the length is zero
    ! jne bye

    GlobalFree pBuf         ' deallocate the memory
    FUNCTION = 0            ' exit with zero and do
    Exit FUNCTION           ' not allocate memory

  bye:
    FUNCTION = pBuf         ' return the memory address

End FUNCTION

' ¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤

FUNCTION GetCmdTail() as STRING

    LOCAL lCmd as DWORD
    LOCAL pCmd as DWORD
    LOCAL pBuf as DWORD
    LOCAL tLen as DWORD

    pCmd = GetCommandLine()

    ! push pCmd             ; push cmdline pointer onto stack
    ! call slen             ; call the short lenth function
    ! mov lCmd, eax         ; store it in lCmd

    outpt$ = space$(lCmd)
    pBuf = StrPtr(outpt$)

    ! push pBuf
    ! push pCmd
    ! call cmdtail
    ! mov tLen, eax

    FUNCTION = left$(outpt$,tLen)

End FUNCTION

' ¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤

FASTPROC slen

    PREFIX "!"

    mov eax, [esp+4]
    sub eax, 1

  lbl:
    add eax, 1
    cmp BYTE PTR [eax], 0
    jne lbl

    sub eax, [esp+4]

    ret 4

    END PREFIX

END FASTPROC

' ¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤

FASTPROC cmdtail

    PREFIX "!"

  ; ------------------------------------------------------
  ; pCmd is the address of the command line
  ; pBuf is the target address for the command tail
  ; NOTE: The pBuf argument should be allocated to the size
  ;       of the command line returned by GetCommandLine()
  ;       API to ensure that the app can handle exploits
  ;
  ; The return value in EAX is the command tail length,
  ; if the length is 0 there is no command tail
  ; ------------------------------------------------------

  ; ***************************************************************
  ; ANSI quoted and unquoted file name version to get command tail.
  ; ***************************************************************
    mov ecx, [esp+4]
    mov edx, [esp+8]

  tstchar1:                     ; see if its a quote or not
    cmp BYTE PTR [ecx], 34      ; test for double quote character
    jne noquote                 ; if not 34 branch to noquote handler

  ; -------------------------------------------------------------
  ; strip the quoted file name from the start of the command line
  ; -------------------------------------------------------------
  quoted:
    add ecx, 1
    cmp BYTE PTR [ecx], 34      ; test for 2nd double quote character
    jne quoted
    jmp ftrim

  ; ---------------------------------------------------------------
  ; strip the unquoted file name from the start of the command line
  ; ---------------------------------------------------------------
  noquote:
    add ecx, 1
    cmp BYTE PTR [ecx], 32
    jg noquote                  ; if > 32, throw it away
    sub ecx, 1

  ; ------------------------------------------------
  ; trim any leading white space from command tail
  ; ------------------------------------------------
  ftrim:
    add ecx, 1
    cmp BYTE PTR [ecx], 32
    je ftrim
    cmp BYTE PTR [ecx], 9
    je ftrim

  ; ------------------------------------------
  ; copy the command tail to the output buffer
  ; ------------------------------------------
  copytail:
    movzx eax, BYTE PTR [ecx]
    mov [edx], al
    add ecx, 1
    add edx, 1
    test eax, eax
    jnz copytail
    mov BYTE PTR [edx], 0       ; append a terminator
    sub edx, 1

  ; ----------------------------------------------
  ; return value in EAX is the command tail length
  ; ----------------------------------------------
    sub edx, [esp+8]
    mov eax, edx

    ret 8

    END PREFIX

END FASTPROC

' ¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤