Zoltan Magyar <[EMAIL PROTECTED]> writes:
>Hi,
>
>I'm working on a binary encryption library for perl. The library receives a
>few parameters, does the encryption and returns the encrypted data. Before
>the encryption takes place the required buffer size for the encrypted data
>is calculated (calling EncryptData with NULL output pointer). When this
>value (nOutDataLen) is calculated sv_setpvn is used to allocate the buffer
>for the result. This call seems to be failing somehow. The context is
>
>unsigned int
>EncryptData(pRemoteKey,pLightData,nLightDataLen,pHeavyData,nHeavyDataLen)
> char* pRemoteKey
> unsigned char* pLightData
> int nLightDataLen
> unsigned char* pHeavyData
> int nHeavyDataLen
> PPCODE:
> unsigned int nOutDataLen = 0;
> SV* svOutData = newSVsv(&sv_undef);
> unsigned char* pOutData = NULL;
> unsigned int bRet = 0;
>
> /* make an initial call with a NULL buffer to get the output length */
> bRet = EncryptData(pRemoteKey,
> pLightData,
> nLightDataLen,
> pHeavyData,
> nHeavyDataLen,
> NULL,
> &nOutDataLen);
>
> /* calling with a NULL output buffer should always fail */
> if(bRet == 0)
> {
> /* set up our output buffer */
> sv_setpvn(svOutData, "", nOutDataLen);
That is going to try and copy nOutDataLen bytes starting at wherever
C compiler has allocated the "" constant string.
I think you want:
/* make it a string - calling sv_upgrade() would be slightly more efficent */
sv_setpvn(svOutData, "", 0);
/* Grow buffer and get the pointer to the buffer */
pOutData = (unsigned char*) SvGROW(svOutData, nOutDataLen+1);
/* tell perl number of valid bytes */
SvCUR_set(svOutData, nOutDataLen);
>
> /* now try and create the blob */
> bRet = EncryptData(pRemoteKey,
> pLightData,
> nLightDataLen,
> pHeavyData,
> nHeavyDataLen,
> pOutData,
> &nOutDataLen);
> }
> /* push the return values onto the stack */
>.
>..
>... etc
An alternative might be to allocate SV with a buffer:
svOutData = newSV(nOutDataLen);
SvCUR_set(svOutData, nOutDataLen);
>
>
>This code worked fine so far but it turned out recently that if the
>calculated result length is too long the code is failing. I did some sanity
>check and found that if nOutDataLen >= 7361 then the library crashes but
>working fine if nOutDatalength <= 7360. According to the debug session
>sv_setpvn is failing.
Weird size is just distance from "" to end of allocated virtual memory segment.
>
>Interestingly the code is working fine when the compiler optimisations (used
>/O1) are turned off.
Which probably allocates more strings or something making the fail point
further away.
>
>I have used Win32 for the investigation and debugging but the library has
>similar problems on Linux (I'm not sure the problem is exactly the same on
>Linux as I haven't debugged it, but the symptoms are the same).
>
>I did quite long search on the net about this issue but I haven't found any
>similar (but found this list :-).
>
>Any thoughts?
>
>TIA
>
>Zoltan Magyar
--
Nick Ing-Simmons
http://www.ni-s.u-net.com/
