qpdf/libqpdf/InsecureRandomDataProvider.cc

#include <qpdf/InsecureRandomDataProvider.hh>

#include <qpdf/qpdf-config.h>
#include <qpdf/QUtil.hh>
#include <stdlib.h>

InsecureRandomDataProvider::InsecureRandomDataProvider() :
    seeded_random(false)
{
}

InsecureRandomDataProvider::~InsecureRandomDataProvider()
{
}

void
InsecureRandomDataProvider::provideRandomData(unsigned char* data, size_t len)
{
    for (size_t i = 0; i < len; ++i)
    {
        data[i] = static_cast<unsigned char>((this->random() & 0xff0) >> 4);
    }
}

long
InsecureRandomDataProvider::random()
{
    if (! this->seeded_random)
    {
	// Seed the random number generator with something simple, but
	// just to be interesting, don't use the unmodified current
	// time.  It would be better if this were a more secure seed.
        unsigned int seed = static_cast<unsigned int>(
            QUtil::get_current_time() ^ 0xcccc);
#ifdef HAVE_RANDOM
        ::srandom(seed);
#else
        srand(seed);
#endif
	this->seeded_random = true;
    }

#  ifdef HAVE_RANDOM
    return ::random();
#  else
    return rand();
#  endif
}

RandomDataProvider*
InsecureRandomDataProvider::getInstance()
{
    static InsecureRandomDataProvider instance;
    return &instance;
}