getentropy.cpp

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/*
* System Call getentropy(2)
* (C) 2017 Alexander Bluhm (genua GmbH)
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
 
#include <botan/internal/getentropy.h>
 
#include <botan/rng.h>
#include <unistd.h>
 
// macOS and Android include it in sys/random.h instead
#if __has_include(<sys/random.h>)
   #include <sys/random.h>
#endif
 
namespace Botan {
 
/**
* Gather 256 bytes entropy from getentropy(2).  Note that maximum
* buffer size is limited to 256 bytes.  On OpenBSD this does neither
* block nor fail.
*/
size_t Getentropy::poll(RandomNumberGenerator& rng) {
   secure_vector<uint8_t> buf(256);
 
   if(::getentropy(buf.data(), buf.size()) == 0) {
      rng.add_entropy(buf.data(), buf.size());
      return buf.size() * 8;
   }
 
   return 0;
}
 
}  // namespace Botan