ws2_32::ntohs returns mistake after WIN10 1709

[philin]

Greeting everybody,
In my installer, I need to check port if listen or not, so I use the code "Ports.nsh" in NSIS wiki.

http://nsis.sourceforge.net/Check_open_ports

It works perfect until I update Windows 10 Fall Creators Update (ver 1709)

Tracking code and debug for a while, I found the error reason is ws2_32::ntohs returns mistake value.

For example, in this code

code:
System::Call ws2_32::ntohs(ir4)i.r4

If input ir4 is 14357(0x3815), ws2_32::ntohs should return 5432(0x1538) to i.r4, but in error case, $4 is 3675448(0x381538).

I have no idea why ws2_32::ntohs retruns mistake value, so I modify my script to avoid ws2_32::ntohs.

code:


IntOp $3 $R0 >> 8

IntOp $4 $R0 & 0xFF

IntOp $4 $4 << 8

IntOp $4 $4 & 0xFF00

IntOp $R0 $4 | $3  

just reverse high-low byte of port value.

Full code will post below, wish it can help someone.

code:


# Usage:

#   Push "Tcp" or "Udp"

#   Push "port_number"

#   Call IsPortOpen

#   Pop $0 ; "open" or "closed" or anything else for error

#

# Or with the LogicLib

#   ${If} ${TCPPortOpen} 80

#   ${EndIf}

#   ${If} ${UDPPortOpen} 137

#   ${EndIf}

#

Function IsPortOpen

 

  Exch $R0 # port to check

  Exch

  Exch $R1

  Push $0

  Push $1

  Push $2

 

  System::Call 'iphlpapi::Get$R1Table(*i.r0, *i .r1, i 1) i .r2'

  ${If} $2 != 122 # ERROR_INSUFFICIENT_BUFFER

    StrCpy $R0 ""

    Pop $2

    Pop $1

    Pop $0

    Exch $R1

    Exch

    Exch $R0

    Return

  ${EndIf}

 

  System::Alloc $1

  Pop $0

 

  System::Call 'iphlpapi::Get$R1Table(ir0, *i r1, i 1) i .r2'

  ${If} $2 != 0 # NO_ERROR

    System::Free $0

    StrCpy $R0 ""

    Pop $2

    Pop $1

    Pop $0

    Exch $R1

    Exch

    Exch $R0

    Return

  ${EndIf}

 

  Push $3

  Push $4

  Push $5

    

  #reverse high-low byte of port to check

  IntOp $3 $R0 >> 8

  IntOp $4 $R0 & 0xFF

  IntOp $4 $4 << 8

  IntOp $4 $4 & 0xFF00

  IntOp $R0 $4 | $3  

 

  System::Call *$0(i.r2)

  IntOp $2 $2 - 1

  ${For} $3 0 $2

    IntOp $4 $0 + 4  # skip dwNumEntries

    ${If} $R1 == "Tcp"

      IntOp $5 $3 * 20 # sizeof(MIB_TCPROW)

      IntOp $4 $4 + $5 # skip to entry

      System::Call *$4(i.r1,i,i.r4,i,i)

      ${If} $1 <> 2  # $1 = dwState, 2 = MIB_TCP_STATE_LISTEN

        ${Continue}

      ${EndIf}

    ${Else}

      IntOp $5 $3 * 8 # sizeof(MIB_UDPROW)

      IntOp $4 $4 + $5 # skip to entry

      System::Call *$4(i,i.r4)

    ${EndIf}

    #System::Call ws2_32::ntohs(ir4)i.r4

 

    ${If} $4 = $R0

      StrCpy $R0 "open"

      ${Break}

    ${EndIf}

  ${Next}

 

  ${If} $R0 != "open"

    StrCpy $R0 "closed"

  ${EndIf}

 

  System::Free $0

 

  Pop $5

  Pop $4

  Pop $3

  Pop $2

  Pop $1

  Pop $0

  Exch $R1

  Exch

  Exch $R0

 

FunctionEnd

 

# LogicLib macros for IsPortOpen

 

!include LogicLib.nsh

 

!macro _PortOpen _a _b _t _f

  !insertmacro _LOGICLIB_TEMP

  Push `${_a}`

  Push `${_b}`

  Call IsPortOpen

  Pop $_LOGICLIB_TEMP

  !insertmacro _== $_LOGICLIB_TEMP "open" `${_t}` `${_f}`

!macroend

!define PortOpen `PortOpen`

 

!macro _TCPPortOpen _a _b _t _f

  !insertmacro _PortOpen Tcp `${_b}` `${_t}` `${_f}`

!macroend

!define TCPPortOpen `"" TCPPortOpen`

 

!macro _UDPPortOpen _a _b _t _f

  !insertmacro _PortOpen Udp `${_b}` `${_t}` `${_f}`

!macroend

!define UDPPortOpen `"" UDPPortOpen`

[Anders]

This is not a bug in Windows, the function is documented as returning a 16-bit value and the upper part of EAX should be ignored. Unfortunately the System plug-in does not have a 16-bit return type but you can use this workaround:

System::Call ws2_32::ntohs(ir4)i.r4
IntOp $4 $4 & 0xffff

This seems to affect others as well so it might get "fixed" in the next Windows release.

[Anders]

Win 10 FCU left shifts the 16-bit parameter (in ECX) and ORs it with EAX (the bottom right shifted bits) at the end.

Win 8 has the registers swapped and EAX is ANDed with 0xff before it is left shifted.

The source code has probably not changed, the compiler has swapped things around and removed one 10 byte instruction.