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Index > Windows > Cannot set environment variable!

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EaxRax



Joined: 20 Jul 2013
Posts: 15
EaxRax 18 Aug 2013, 15:19
Wrote a small program to set the environment variable, but it does not install it. Why can't I set an environment variable? What am I doing wrong?
Code:
include 'C:\Program Files\FASM\INCLUDE\win32a.inc'

format PE Console 4.0
entry  Start

section '.text' code readable executable

Start:


        nop

        invoke  SetEnvironmentVariableA, _data.EnvironmentName, _data.EnvironmentContents

      ; check for an error.
        test   eax, eax
        jz     Exit

        invoke  GetEnvironmentStrings

        nop


Exit:
  invoke  ExitProcess, 0

section '.data' data readable writeable

  _data.EnvironmentName:      db  'Path', 0
  _data.EnvironmentContents:   db  'C:\Program Files\ENVAR', 0

section '.idata' import data readable

  library kernel, 'KERNEL32.DLL'

  import kernel,\
    SetEnvironmentVariableA, 'SetEnvironmentVariableA',\
    GetEnvironmentStrings, 'GetEnvironmentStrings',\
    ExitProcess, 'ExitProcess'    
It may be necessary to prescribe something in the registry?


Description: Application source.
Download
Filename: ENVAR.7z
Filesize: 604 Bytes
Downloaded: 449 Time(s)

Post 18 Aug 2013, 15:19
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AsmGuru62



Joined: 28 Jan 2004
Posts: 1678
Location: Toronto, Canada
AsmGuru62 18 Aug 2013, 15:35
How did you see that it does not work?
Maybe need GetEnvironmentStringsA?
Post 18 Aug 2013, 15:35
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EaxRax



Joined: 20 Jul 2013
Posts: 15
EaxRax 18 Aug 2013, 16:36
AsmGuru62 wrote:
How did you see that it does not work?
See screen shot, below!
AsmGuru62 wrote:
Maybe need GetEnvironmentStringsA?
It is possible and so, but it will change nothing.


Description:
Filesize: 135.77 KB
Viewed: 5695 Time(s)

Envar_screenshot.png


Post 18 Aug 2013, 16:36
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AsmGuru62



Joined: 28 Jan 2004
Posts: 1678
Location: Toronto, Canada
AsmGuru62 18 Aug 2013, 17:09
I see... you were hoping to change the OS environment variables.
Please read this:
http://msdn.microsoft.com/en-us/library/windows/desktop/ms682653(v=vs.85).aspx

It describes where in the registry the environment is located.
So, basically, yes, you need to write into Registry.
Post 18 Aug 2013, 17:09
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EaxRax



Joined: 20 Jul 2013
Posts: 15
EaxRax 18 Aug 2013, 17:18
Thanks, now I will read!
Post 18 Aug 2013, 17:18
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EaxRax



Joined: 20 Jul 2013
Posts: 15
EaxRax 19 Aug 2013, 17:29
I read article. Written, need to make changes to a registry key "HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\Session Manager\ Environment". Has looked for functions working with the registry on MSDN. Has found these functions, but so it is a lot of them, that eyes run up. And i do not know, what function should use.

Can anyone knows which function to change an environment variable in the registry?

Prompt me, please!
Post 19 Aug 2013, 17:29
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AsmGuru62



Joined: 28 Jan 2004
Posts: 1678
Location: Toronto, Canada
AsmGuru62 19 Aug 2013, 18:42
This tested (and worked) on XP SP3.
I am not checking any of return codes - just ran it in OLLYDBG and looked
into Environment. New variable appeared OK.
Code:
    lpSubKey  db 'System\CurrentControlSet\Control\Session Manager\Environment',0
    lpValue   db 'MyFreshVar32',0
    bufData   db 'THIS VARIABLE HAS BEEN ADDED BY FASM!',0
    HKey      dd 0

...

    invoke    RegOpenKeyExA, HKEY_LOCAL_MACHINE, lpSubKey, 0, KEY_SET_VALUE, HKey
    mov       ebx, [HKey]
    mov       esi, bufData

    invoke    lstrlenA, esi
    inc       eax

    invoke    RegSetValueExA, ebx, lpValue, 0, REG_SZ, esi, eax
    invoke    RegCloseKey, ebx

...

; ---------------------------------------------------------------------------
section '.idata' import data readable writeable

    library kernel32,'KERNEL32.DLL',user32,'USER32.DLL',gdi32,'GDI32.DLL',advapi32,'ADVAPI32.DLL'

    include 'API\Kernel32.Inc'
    include 'API\User32.Inc'
    include 'API\Gdi32.Inc'
    include 'API\AdvApi32.Inc'      ; <-- this one needed to work with Registry

    
Post 19 Aug 2013, 18:42
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EaxRax



Joined: 20 Jul 2013
Posts: 15
EaxRax 19 Aug 2013, 20:18
AsmGuru62 That's it! Very Happy Code works perfectly! Very Happy Thank you very much! Rolling Eyes Very Happy

P.S. Questions on this topic no more!
Post 19 Aug 2013, 20:18
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