// Calculate line size
std::string strData(ptrOut);
size_t lineLen = strData.find("\n");
if(lineLen == (size_t) MPSStringType::npos)

is a verry dangerous thing which will probably crash under a lot of circumstances. So it is a lot safer to just input the line len into the function.It can differ between 64 = PEM newline padding,and 72 for some other standard i cant recall right now X). Although there are some type mißmatches i forgot to clean out.
The input types i used where:
typedef std::string MPSStringType and
typedef char MPSCharType

Have fun ;)

However here is some code i wrote that does the job. Feel free to use it ..

size_t MPSCalculateBase64Size(size_t inLen,int iLineSize)
{
double dInLen = inLen;
double dLineSize = iLineSize;
double dAdd = 0.0;
double dLen = 0.0;
size_t iResult = 0;

double dModIn = fmod( dInLen,3.0);

if( dModIn )
dLen = ( ((( dInLen + 3.0 ) – fmod( dInLen, 3.0 )) / 3.0 ) * 4.0 );
else
dLen = ( ( dInLen / 3.0 ) * 4.0 ) ;

dAdd = dLen;

// If line size is != 0 the we must add the newlines to our resulting
// data length
if( iLineSize != 0)
{
// Add the newlines required after the pem/base64 standard
// (after 64 chars)
dAdd += ( dLen / dLineSize );

// Check for incomplete line which is although terminated with a
// \n (PEM Base64).
double dModLine = fmod(dLen,dLineSize);
if( dModLine )
{
dAdd += 1.0;
}
}

iResult = (size_t) dAdd;
return iResult;
}

int MPSBase64EncodeStr(const MPSCharType* ptrDataIn,size_t inLen,MPSStringType& strResult,size_t& stResultSize)
{
if(! ptrDataIn)
return MPS_ERR_PARAM;

BIO *bio = NULL;
BIO *b64 = NULL;

b64 = BIO_new(BIO_f_base64());
bio = BIO_new( BIO_s_mem() );
bio = BIO_push(b64, bio);

size_t rLen = BIO_write(bio, ptrDataIn, (int) inLen);
BIO_flush(bio);

char* ptrOut = NULL;
BIO_get_mem_data(bio, &ptrOut);

if(ptrOut)
{
// Calculate line size
std::string strData(ptrOut);
size_t lineLen = strData.find("\n");
if(lineLen == (size_t) MPSStringType::npos)
{
lineLen = 0;
}

int size = (int) MPSCalculateBase64Size( inLen, (int)lineLen ) ;

strResult.insert(0,ptrOut,size);
stResultSize = size;
}

BIO_free_all(bio);

return MPS_OK;
}

int MPSBase64DecodeStr(const MPSCharType* ptrDataIn,size_t inLen,MPSStringType& strResult,size_t& stResultSize)
{
if(! ptrDataIn)
return MPS_ERR_PARAM;

BIO* b64 = NULL;
BIO* bmem = NULL;
char *buffer = (char *) malloc(inLen);
if(buffer)
{
memset(buffer, 0, inLen);
b64 = BIO_new(BIO_f_base64());
bmem = BIO_new_mem_buf((void*) ptrDataIn, (int) inLen);
bmem = BIO_push(b64, bmem);

size_t rLen = BIO_read(bmem, buffer,(int) inLen);

strResult.insert(0, (const char*) buffer, rLen);
stResultSize = rLen;

BIO_free_all(bmem);
delete [] buffer,buffer = NULL;

return MPS_OK;
}
return MPS_ERR;

}

and this will work.

Can you provide more information? I've tested to make sure it works with the latest version of OpenSSL.

bmem = BIO_push(b64, bmem);

to

BIO_push(b64, bmem);

Could you please share some code, on how to decode base64 encode DER format to X509.

Any help will be great.

Thanks,
Saleem