Function crypto_random_bytes

src/random.cpp:126–171

		}

		void crypto_random_bytes(span<char> buffer)
		{
#ifdef TORRENT_BUILD_SIMULATOR
			// In the simulator we want deterministic random numbers
			std::generate(buffer.begin(), buffer.end(), [] { return char(random(0xff)); });
#elif TORRENT_USE_CNG
			aux::cng_gen_random(buffer);
#elif TORRENT_USE_CRYPTOAPI
			// windows
			aux::crypt_gen_random(buffer);
#elif defined TORRENT_USE_LIBCRYPTO && !defined TORRENT_USE_WOLFSSL
// wolfSSL uses wc_RNG_GenerateBlock as the internal function for the
// openssl compatibility layer. This function API does not support
// an arbitrary buffer size (openssl does), it is limited by the
// constant RNG_MAX_BLOCK_LEN.
// TODO: improve calling RAND_bytes multiple times, using fallback for now

			// openssl
			int r = RAND_bytes(reinterpret_cast<unsigned char*>(buffer.data())
				, int(buffer.size()));
			if (r != 1) aux::throw_ex<system_error>(errors::no_entropy);
#elif TORRENT_USE_GETRANDOM
			ssize_t const r = ::getrandom(buffer.data(), static_cast<std::size_t>(buffer.size()), 0);
			if (r == ssize_t(buffer.size())) return;
			if (r == -1 && errno != ENOSYS) aux::throw_ex<system_error>(error_code(errno, generic_category()));
			static dev_random dev;
			dev.read(buffer);
#elif TORRENT_USE_DEV_RANDOM
			static dev_random dev;
			dev.read(buffer);
#else

#if TORRENT_BROKEN_RANDOM_DEVICE
			// even pseudo random numbers rely on being able to seed the random
			// generator
#error "no entropy source available"
#else
#ifdef TORRENT_I_WANT_INSECURE_RANDOM_NUMBERS
			std::generate(buffer.begin(), buffer.end(), [] { return char(random(0xff)); });
#else
#error "no secure entropy source available. If you really want insecure random numbers, define TORRENT_I_WANT_INSECURE_RANDOM_NUMBERS"
#endif
#endif

#endif
		}
}

	std::uint32_t random(std::uint32_t const max)