Hello, i'm working with dll and i'm trying to recode this c++ to masm:
typedef struct test {
int a;
int b;
int c;
int d;
int e;
char* string;
} hello_struct;
extern "C" DllExport BOOL _cdecl myHelloAPI(hello_struct *hello) {
sprintf_s(hello->string, 12, "Hello World");
return 0;
}
i did my include to msvcrt, and did something like this:
.data
dataString db "Hello World", 0
bufferSize equ 12
hello_struct STRUCT
a1 dd ?
b2 dd ?
c3 dd ?
d4 dd ?
e5 dd ?
stringhw db bufferSize DUP(?)
hello_struct ENDS
.code
myHelloAPI PROC, dataz:PTR hello_struct
;mov eax, [ebp+dataz]
;push offset dataString ;
;push bufferSize
;push dword ptr [eax+14h] ; Buffer
;call sprintf_s
;add esp, 0Ch
mov eax,0
ret
myHelloAPI ENDP
I couldn't progress much beside that, forget the code inside the myHelloAPI proc, those are desperate broken attempts with copilot ai, cody ai, and chatgpt. it drive me crazy wasting time on this that looks simple.. .if anyone know how can i reproduce that using sprintf_s or an equivalent.
Is myHelloAPI a function that you want to export in a dll?
Could you post the full source of what you have already done?
Include your definition file (xxx.def) as well if that is the case. And batch file to create the dll.
Zip your project and attach it.
One thing wrong: in the original structure definition,
char* string;
is a pointer to a character string, not a string itself as you coded.
You should have this for that member instead:
stringPtr dd ?
Hi ewok!
I'm not sure sprintf_s function is in Masm32 SDK libraries, but at list will work the more simple "crt_sprintf".
; ¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤
include \masm32\include\masm32rt.inc
; ¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤
comment * -----------------------------------------------------
Build this console app with
"MAKEIT.BAT" on the PROJECT menu.
----------------------------------------------------- *
.data
format1 db " There are %i things", 0
.code
start:
; ¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤
call main
inkey
exit
; ¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤
main proc
local buffer[248]:byte
cls
invoke crt_sprintf, addr buffer, addr format1, 15
print addr buffer, 13,10
ret
main endp
; ¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤
end start
Regards, HSE
>Is myHelloAPI a function that you want to export in a dll?
Yes!
i couldn't find where to attach a zip so here is it hosted on workupload https://workupload.com/file/G7PsKrNHudD (https://workupload.com/file/G7PsKrNHudD)
Thanks HSE, if i remember i tried also to implement crt_sprintf but it wasn't good.
Quote from: ewok on May 01, 2024, 03:07:30 AMi couldn't find where to attach a zip
If you don't see "
Click or drag files here to attach them." at the bottom of your post when you're writing it, click "Preview" and it shall magically appear.
Quote from: ewok on May 01, 2024, 03:07:30 AMi couldn't find where to attach a zip so here is it hosted on workupload
I have attached it to my post here. attachment no longer needed here.
At the bottom of the edit window (when making a post) you should see "Click or drag files here to attach them"
Your source code is below... see my comment there...
Also msvcrt.inc should be before msvcrt.lib, I changed it in the source below
The include (.inc) file should always be before the library (.lib) file
.486
option casemap :none ; case sensitive
include \masm32\include\masm32rt.inc
include \masm32\include\windows.inc
include \masm32\include\msvcrt.inc ; Include the C runtime library
includelib msvcrt.lib ; Include the C runtime library
_DllMainCRTStartup PROTO :DWORD,:DWORD,:DWORD
myHelloAPI PROTO :DWORD,:DWORD
.data
dataString db "Hello World", 0
bufferSize equ 12
hello_struct STRUCT
a1 dd ?
b2 dd ?
c3 dd ?
d4 dd ?
e5 dd ?
stringhw db bufferSize DUP(?) ;;; should be a pointer to the string, as NoCforme mentioned above
hello_struct ENDS
.code
_DllMainCRTStartup proc instance:DWORD,reason:DWORD,unused:DWORD
mov eax,1
ret
_DllMainCRTStartup endp
myHelloAPI proc q:DWORD,w:DWORD
;mov eax, [ebp+dataz]
;push offset dataString ;
;push bufferSize
;push dword ptr [eax+14h] ; Buffer
;call sprintf_s
;add esp, 0Ch
mov eax,0
ret
myHelloAPI endp
endYour definition file looks ok.
What are the arguments "q:DWORD,w:DWORD" for?
At any rate, the dll builds with the batch file in the zip archive. Fix the structure member and put the .inc declaration before the .lib declaration for msvcrt to see if those are the only issues that you have.
Quote from: HSE on May 01, 2024, 03:02:38 AMI'm not sure sprintf_s function is in Masm32 SDK libraries
Definitely not... sprintf_s (https://learn.microsoft.com/en-us/cpp/c-runtime-library/reference/sprintf-s-sprintf-s-l-swprintf-s-swprintf-s-l?view=msvc-170) :cool:
main.asm(38) : error A2006: undefined symbol : sprintf_sseems that sprintf_s is not in msvcrt.dll, at least on Windows 7. There are other alternatives as HSE mentioned above.
Quote from: sudoku on May 01, 2024, 04:01:56 AMDefinitely not... sprintf_s (https://learn.microsoft.com/en-us/cpp/c-runtime-library/reference/sprintf-s-sprintf-s-l-swprintf-s-swprintf-s-l?view=msvc-170) :cool:
Is working here with:
externdef _imp__sprintf_s:PTR c_msvcrt
crt_sprintf_s equ <_imp__sprintf>
but I think the linker load that function from a newer msvcrt.lib (version 12), but that have to work in Win7
Quote from: HSE on May 01, 2024, 04:20:29 AMIs working here with:
externdef _imp__sprintf_s:PTR c_msvcrt
crt_sprintf_s equ <_imp__sprintf>
Okay, it does work here with that, on Windows 7. .
My mistake. It does
not run in Windows 7 even with the exterdef, I was still using "printf" in the test code, forgot to change it back to sprintf_s. :rolleyes:
So apparently sprintf_s is only on later versions of msvcrt than what is in Windows 7.
What version of Windows are
you running, ewok?
Hey, here's an idea: forget about sprintf(). Just use wsprintf() instead, which is a standard Win32 function, that (probably) does what you need it to do (i.e, format a string to a memory buffer).
Documentation here (https://learn.microsoft.com/en-us/windows/win32/api/winuser/nf-winuser-wsprintfa?redirectedfrom=MSDN).
Hello,
sprintf_s works on Windows 7. Attached is a quick example. The problem is that the import library msvcrt.lib built by the Masm32 package does not export this function :
\PellesC\bin\podump.exe /SYMBOLS G:\masm32\lib\msvcrt.lib | findstr sprintf
0003 00000000 SECT1 notype () external | _sprintf
0006 00000000 SECT2 notype external | __imp__sprintf
0003 00000000 SECT1 notype () external | _vsprintf
0006 00000000 SECT2 notype external | __imp__vsprintf
An easy solution is to rebuild the library.
.386
.model flat, stdcall
option casemap :none
include \masm32\include\windows.inc
include \masm32\include\user32.inc
include \masm32\include\kernel32.inc
include \masm32\include\masm32.inc
includelib \masm32\lib\user32.lib
includelib \masm32\lib\kernel32.lib
includelib \masm32\lib\masm32.lib
includelib msvcrt.lib
sprintf_s PROTO C :DWORD,:VARARG
SIZE_OF_BUFFER equ 64
.data
a1 db 'This is',0
a2 db 'a test.',0
a3 db '%s %s',0
.data?
buffer db SIZE_OF_BUFFER dup(?)
.code
start:
invoke sprintf_s,ADDR buffer,\
SIZE_OF_BUFFER,\
ADDR a3,ADDR a1,ADDR a2
invoke StdOut,ADDR buffer
invoke ExitProcess,0
END start
Oh, Vortex. :thumbsup:
I was correct in my initial assumption that hutch missed that one in the include file for msvcrt. Bravo.
I had not thought about rebuilding the library, leading me to believe it did not exist in Windows 7 msvcrt.dll.
Under the hood, msvcrt calls "vsprintf_s" in case anyone is interested
(https://i.postimg.cc/wRM7NH3p/untitled.png) (https://postimg.cc/wRM7NH3p)
Works like a charm on Windows 10:
include \masm32\MasmBasic\MasmBasic.inc
.DATA?
buffer db 10 dup(?)
Init
Dll "msvcrt"
Declare sprintf_s, C:?
Print Str$("%i characters copied", sprintf_s(addr buffer, sizeof buffer, "%i", 123456789))
MsgBox 0, offset buffer, "Result:", MB_OK
EndOfCode
Quote from: sudoku on May 01, 2024, 03:15:47 AMWhat are the arguments "q:DWORD,w:DWORD" for?
That was part of desperate coding, at a point i started doing non-sense code/test
Quote from: NoCforMe on May 01, 2024, 02:40:26 AMOne thing wrong: in the original structure definition,
char* string;
is a pointer to a character string, not a string itself as you coded.
You should have this for that member instead:
stringPtr dd ?
I thought of a struct was like an array, so it's just pointers inside a struct? i'll have to fix that.
Quote from: sudoku on May 01, 2024, 04:27:19 AMWhat version of Windows are you running, ewok?
win 10
Quote from: Vortex on May 01, 2024, 05:25:52 AMThe problem is that the import library msvcrt.lib built by the Masm32 package does not export this function
If one day there would be a new release of masm that could be a good addition!
Thanks also for your custom lib. I'm gonna fix my struct and try that lib
Quote from: ewok on May 02, 2024, 01:31:47 AMQuote from: NoCforMe on May 01, 2024, 02:40:26 AMOne thing wrong: in the original structure definition,
char* string;
is a pointer to a character string, not a string itself as you coded.
You should have this for that member instead:
stringPtr dd ?
I thought of a struct was like an array, so it's just pointers inside a struct? i'll have to fix that.
A structure (C or assembly language, doesn't matter) is a
collection which can contain anything (including other structures).
That field
could be an actual string, as you had originally coded it, but in this case it's a pointer to a string instead (because the C definition was
char *string). You can have strings--otherwise known as arrays of characters--in a structure; in fact, several Win32 structures, like
LOGFONT (https://learn.microsoft.com/en-us/windows/win32/api/Wingdi/ns-wingdi-logfonta), have them.
If the C definition had been
char string[some_size], then you'd want to put a string (array) there instead.
Quote from: sudoku on May 01, 2024, 05:28:39 AMUnder the hood, msvcrt calls "vsprintf_s" in case anyone is interested
Hi sudoku,
msvcrt.inc from the Masm32 package defines only this version :
externdef _imp__vsprintf:PTR c_msvcrt
crt_vsprintf equ <_imp__vsprintf>
I have rebuilt my msvcrt.lib here, after adjusting the include file. Thanks for that advice.
From that quote in your post, it should have been
QuoteUnder the hood, msvcrt calls "vsprintf_s" when the user calls "sprintf_s" in case anyone is interested
as illustrated by the image in that post. I thought it was obvious in the context of the thread, so I felt no need to elaborate. :smiley:
sounds like sprintf_s is for sanitizing db/characters/strings..
https://pastebin.com/m54wj4QL (https://pastebin.com/m54wj4QL)
replace the ' in the last line with ; to assemble and link...
you don't need to specify the size of the data/string/character to be processed.
and this is good for dynamic data/string/character processing. like you have a fixed buffer of zeroes in your code and you can just use that with the sprintf_s sanitizer and it will cut on the first ,0 that it encounters, whatever size is that provided that it won't exceed the buffer size..
Quote from: alCoPaUL on May 16, 2024, 05:45:13 PMyou don't need to specify the size of the data/string/character to be processed.
and this is good for dynamic data/string/character processing. like you have a fixed buffer of zeroes in your code and you can just use that with the sprintf_s sanitizer and it will cut on the first ,0 that it encounters, whatever size is that provided that it won't exceed the buffer size..
Now suppose you have a case where the string is NOT zero terminated??? It would be good to specify the string size in that instance, no? Else as you say 'it will cut on the first ",0" that it encounters' ( the quotes inferred by your post but not explicitly stated there). Where would that be (the first ",0"), in the case of a string that is not zero terminated?? I see a possible buffer overflow (and program crash) in that case.
Quote from: sudoku on May 17, 2024, 02:40:01 AMQuote from: alCoPaUL on May 16, 2024, 05:45:13 PMyou don't need to specify the size of the data/string/character to be processed.
and this is good for dynamic data/string/character processing. like you have a fixed buffer of zeroes in your code and you can just use that with the sprintf_s sanitizer and it will cut on the first ,0 that it encounters, whatever size is that provided that it won't exceed the buffer size..
Now suppose you have a case where the string is NOT zero terminated??? It would be good to specify the string size in that instance, no? Else as you say 'it will cut on the first ",0" that it encounters' ( the quotes inferred by your post but not explicitly stated there). Where would that be (the first ",0"), in the case of a string that is not zero terminated?? I see a possible buffer overflow (and program crash) in that case.
but my example has a 999426 zeroes as a buffer..
you put 76 bytes on a 999426 zeroes as a buffer, printf will just take the 76 bytes and the first zero (thanks to sprintf_s processing the buffer as "%s")
and say your code still have to process 6675 bytes before printing it, printf will just take 6675 bytes and the first zero, again thanks to sprintf_s.
dynamic data processing will be stifled by doing strlen() everytime you pass a buffer..
and it's allowed, as you can see (if you can assemble and link my source)..
Quote from: alCoPaUL on May 17, 2024, 03:32:17 AMand it's allowed, as you can see (if you can assemble and link my source)..
b db 999426 DUP(0)Nah, I'll pass. One megabyte-ish in .data ??
If you have a smaller example, I will
consider it.
You can post your source
here, did you know? It would make it much easier if anyone is interested in it, rather than having to copy and paste your pastebin link (its not clickable - btw) and go to a third party site to obtain your code.
Quote from: sudoku on May 17, 2024, 03:47:23 AMQuote from: alCoPaUL on May 17, 2024, 03:32:17 AMand it's allowed, as you can see (if you can assemble and link my source)..
b db 999426 DUP(0)Nah, I'll pass. One megabyte-ish in .data ??
If you have a smaller example, I will consider it.
You can post your source here, did you know? It would make it much easier if anyone is interested in it, rather than having to copy and paste your link (its not clickable - btw) and go to a third party site to obtain your code.
it's the era of datasscience..
i was supposed to post that on this forum the time i finished that but the forum was down..
again, sprintf_s formats that to %s and cuts the rest of the zeroes and finally you pass the buffer (the string data and ,0) to printf, printing that to %s.
so what's happening is double sanitization to %s..
clear from meme buffer overflow..
and when the code is using the 999426 zeroes as a buffer and your code is manipulating data to information and the maxed string that it manipulates is 9999 bytes, it's always underflowing...
but when it assembles the final string by combining 9999 and 9999 and 9999, it still underflowing the buffer coz that's only 29997 bytes inside a 999426 zero buffer...
and sprintf_s only takes the 29997 bytes & ,0 from that humongous buffer to pass to printf....
Quote from: alCoPaUL on May 17, 2024, 04:19:03 AMi was supposed to post that on this forum the time i finished that but the forum was down..
Ah, okay.
source code & essential files in the zip..
masm32 version
; sprintf_s + printf
; by alCoPaUL [GIMO]
; 5/16/2024 NYC
;
; ml.exe printf_s32.asm /link /subsystem:console /defaultlib:32msvcrt.lib /entry:start [or /entry:main (will assemble and link with warning)]
;
.686
.model flat,stdcall
extern printf:proc
extern sprintf_s:proc
.code
start:
main proc
enter 0,0
push offset x
push offset i
push f
push offset b
call sprintf_s
push eax
push offset b
push offset i
call printf
leave
ret
main endp
.data
f equ 10 ; Scale This Length
x db 'Thereupon',0 ; Manually Or Use StrLen()
b db 999426 DUP(0) ; As Usual, Humongous Buffer
i db 25h,73h,0
end start
Tried to run your executable
(https://i.postimg.cc/63YS30B5/untitled.png)
I am quite sure that the "32msvcrt.lib" that you are using is not for msvcrt.dll, but rather a dll from the vcruntime dll shown in the message box. A non-starter for me.
Quote from: sudoku on May 17, 2024, 12:19:08 PMTried to run your executable
(https://i.postimg.cc/63YS30B5/untitled.png)
the library (.lib) is from visual studio 2010, needs the appropriate redistributable runtimes..
Dll hell in the 21st Century, isn't it lovely?
C:\Windows\System32\msvcrt.dll
C:\Windows\System32\msvcr100_clr0400.dll
C:\Windows\System32\msvcr120_clr0400.dll
C:\Windows\System32\msvcrt20.dll
C:\Windows\System32\msvcrt40.dll
C:\Windows\System32\msvcr71.dll
C:\Windows\System32\msvcr80.dll
C:\Windows\System32\msvcr100.dll
There is a simple solution:
- find out what's the latest msvcr*.dll
- use LoadLibrary and GetProcAddress
Quote from: jj2007 on May 17, 2024, 03:09:59 PMDll hell in the 21st Century, isn't it lovely?
C:\Windows\System32\msvcrt.dll
C:\Windows\System32\msvcr100_clr0400.dll
C:\Windows\System32\msvcr120_clr0400.dll
C:\Windows\System32\msvcrt20.dll
C:\Windows\System32\msvcrt40.dll
C:\Windows\System32\msvcr71.dll
C:\Windows\System32\msvcr80.dll
C:\Windows\System32\msvcr100.dll
There is a simple solution:
- find out what's the latest msvcr*.dll
- use LoadLibrary and GetProcAddress
m$ tactics - either for the $$ or from old school m$ guises who don't want all the os versions to be swiped by malware so they grouped the default development software for the os via different redistributable runtime files..
anyway, attached is similar code that i previously posted with 3 C Standard lib functions but it's written in another assembler. you can easily format this to masm32 assembly src file using the previous code that i shared as template..
splitted the zip (file size restrictions) so just rename faxx.jpg to faxx.z01...
StrLen() must be sanitized by checking if it's FFFFFFFEh to get the Maxed Capacity.
But the Primacy of the 999426 DUP(0) buffer is upheld so StrLen(data), by practice, is wayyy smaller than the function's Maxed Capacity.
And since I posted the 64-bit version, now it's clear why the size of the buffer in 64-bit sprintf_s can be ommited coz the maxed capacity of StrLen(data), to suffice the length of the inputted data to sprintf_s, Ideally, is effing FFFFFFFFFFFFFFFEh bytes.