What is required to use a function from the c runtime lib that is not declared in masm32's msvcrt.inc?
Specifically, I would like to use rand_s (because it returns 32 bits rather than 31 bits like nrandom and rand).
Or if anyone can recommend a full 32 bit random number generator, that would work also. Thanks.
Hi Jim,
The version of msvcrt.dll shipped with Windows 7 exports rand_s :
G:\PellesC\Bin>podump.exe /exports C:\Windows\System32\msvcrt.dll | findstr "rand"
496 495 000007FF756A1980 rand
497 496 000007FF756E5D74 rand_s
4AB 4AA 000007FF756A40BC srand
Creating a new msvcrt.lib :
G:\PellesC\Bin>polib.exe /OUT:msvcrt.lib /MACHINE:x86 C:\Windows\System32\msvcrt.dll
rand_s PROTO C :DWORD
Thanks for that. I was hoping it was just a matter of definition in masm32's msvcrt.inc to use the one in msvcrt.lib. Guess I have to make a new msvcrt.lib for masm32?
Hi Jim,
You can use polib.exe to create a new copy of msvcrt.lib :
\masm32\bin\polib.exe /OUT:msvcrt.lib /MACHINE:x86 C:\Windows\System32\msvcrt.dll
Pelle's librarian polib comes also with the Pelles C installation.
LoadLibrary and GetProcAddress are your friends, too.
Well... I wouldn't call them my friends, but we can get along with a little effort.
Quote from: jimg on April 12, 2020, 01:26:09 AM
Or if anyone can recommend a full 32 bit random number generator, that would work also. Thanks.
I was looking to this, maybe can be usefull to you:
https://www.agner.org/random/
Quoterand_s depends on the RtlGenRandom API, which is only available in Windows XP and later.
https://docs.microsoft.com/en-us/previous-versions/sxtz2fa8(v%3Dvs.140)
About the RtlGenRandom function :
QuoteNote This function has no associated import library. This function is available as a resource named SystemFunction036 in Advapi32.dll. You must use the LoadLibrary and GetProcAddress functions to dynamically link to Advapi32.dll.
https://docs.microsoft.com/en-us/windows/win32/api/ntsecapi/nf-ntsecapi-rtlgenrandom?redirectedfrom=MSDN
Here is a quick RtlGenRandom test :
include \masm32\include\masm32rt.inc
include invoke.inc
.data
kernel32 db 'kernel32.dll',0
advapi32 db 'advapi32.dll',0
SystemFn036 db 'SystemFunction036',0
RtlSecZeroMem db 'RtlSecureZeroMemory',0
crlf db 13,10,0
s1 db 'Random Byte = %u',13,10,0
s2 db 'Random Dword = %u',13,10,0
.code
start:
call main
invoke ExitProcess,0
main PROC USES esi ebx
LOCAL hDll:DWORD
LOCAL RtlGenRandom:DWORD
LOCAL buffer[12]:BYTE
lea esi,buffer
invoke LoadLibrary,ADDR advapi32
mov hDll,eax
invoke GetProcAddress,eax,\
ADDR SystemFn036
mov RtlGenRandom,eax
push esi
_invoke RtlGenRandom,esi,12
; Print 12 random BYTE values
mov ebx,12
@@:
movzx eax,BYTE PTR [esi]
invoke crt_printf,ADDR s1,eax
inc esi
dec ebx
jnz @b
pop esi
_invoke RtlGenRandom,esi,12
; Print 3 random DWORD values
invoke crt_printf,ADDR crlf
mov ebx,12/4
@@:
invoke crt_printf,ADDR s2,\
DWORD PTR [esi]
add esi,4
dec ebx
jnz @b
invoke FreeLibrary,hDll
ret
main ENDP
END start
deleted
Excellent, Thanks Vortex :)