path: root/src/tests/test_rng.cpp

/*
* (C) 2014,2015,2017 Jack Lloyd
* (C) 2016 René Korthaus, Rohde & Schwarz Cybersecurity
*
* Botan is released under the Simplified BSD License (see license.txt)
*/

#include "tests.h"
#include "test_rng.h"

#if defined(BOTAN_HAS_STATEFUL_RNG)
   #include <botan/stateful_rng.h>
#endif

#if defined(BOTAN_HAS_HMAC_DRBG)
   #include <botan/hmac_drbg.h>
#endif

#if defined(BOTAN_HAS_AUTO_RNG)
   #include <botan/auto_rng.h>
#endif

#if defined(BOTAN_HAS_CHACHA_RNG)
   #include <botan/chacha_rng.h>
#endif

#if defined(BOTAN_HAS_SYSTEM_RNG)
   #include <botan/system_rng.h>
#endif

#if defined(BOTAN_HAS_RDRAND_RNG)
   #include <botan/rdrand_rng.h>
#endif

#if defined(BOTAN_HAS_ENTROPY_SOURCE)
   #include <botan/entropy_src.h>
#endif

#if defined(BOTAN_TARGET_OS_HAS_POSIX1)
   #include <unistd.h>
   #include <sys/wait.h>
#endif

namespace Botan_Tests {

namespace {

#if defined(BOTAN_HAS_STATEFUL_RNG)

class Stateful_RNG_Tests : public Test
   {
   public:
      std::vector<Test::Result> run() override
         {
         std::vector<Test::Result> results;
         results.push_back(test_reseed_kat());
         results.push_back(test_reseed());
         results.push_back(test_max_number_of_bytes_per_request());
         results.push_back(test_broken_entropy_input());
         results.push_back(test_check_nonce());
         results.push_back(test_prediction_resistance());
         results.push_back(test_randomize_with_ts_input());
         results.push_back(test_security_level());

         /*
         * This test uses the library in both parent and child processes. But
         * this causes a race with other threads, where if any other test thread
         * is holding the mlock pool mutex, it is killed after the fork. Then,
         * in the child, any attempt to allocate or free memory will cause a
         * deadlock.
         */
         if(Test::options().test_threads() == 1)
            results.push_back(test_fork_safety());

         return results;
         }

   protected:
      virtual std::string rng_name() const = 0;

      virtual std::unique_ptr<Botan::Stateful_RNG> create_rng(
         Botan::RandomNumberGenerator* underlying_rng,
         Botan::Entropy_Sources* underlying_es,
         size_t reseed_interval) = 0;

      std::unique_ptr<Botan::Stateful_RNG> make_rng(Botan::RandomNumberGenerator& underlying_rng,
                                                    size_t reseed_interval = 1024)
         {
         return create_rng(&underlying_rng, nullptr, reseed_interval);
         }

      std::unique_ptr<Botan::Stateful_RNG> make_rng(Botan::Entropy_Sources& underlying_srcs,
                                                    size_t reseed_interval = 1024)
         {
         return create_rng(nullptr, &underlying_srcs, reseed_interval);
         }

      std::unique_ptr<Botan::Stateful_RNG> make_rng(Botan::RandomNumberGenerator& underlying_rng,
                                                    Botan::Entropy_Sources& underlying_srcs,
                                                    size_t reseed_interval = 1024)
         {
         return create_rng(&underlying_rng, &underlying_srcs, reseed_interval);
         }

      virtual Test::Result test_reseed_kat() = 0;

      virtual Test::Result test_security_level() = 0;

      virtual Test::Result test_max_number_of_bytes_per_request() = 0;
   private:
      Test::Result test_reseed()
         {
         Test::Result result(rng_name() + " Reseed");

         // test reseed_interval is enforced
         Request_Counting_RNG counting_rng;

         std::unique_ptr<Botan::Stateful_RNG> rng = make_rng(counting_rng, 2);

         rng->random_vec(7);
         result.test_eq("initial seeding", counting_rng.randomize_count(), 1);
         rng->random_vec(9);
         result.test_eq("still initial seed", counting_rng.randomize_count(), 1);

         rng->random_vec(1);
         result.test_eq("first reseed", counting_rng.randomize_count(), 2);
         rng->random_vec(15);
         result.test_eq("still first reseed", counting_rng.randomize_count(), 2);

         rng->random_vec(15);
         result.test_eq("second reseed", counting_rng.randomize_count(), 3);
         rng->random_vec(1);
         result.test_eq("still second reseed", counting_rng.randomize_count(), 3);

         if(rng->max_number_of_bytes_per_request() > 0)
            {
            // request > max_number_of_bytes_per_request, do reseeds occur?
            rng->random_vec(64 * 1024 + 1);
            result.test_eq("request exceeds output limit", counting_rng.randomize_count(), 4);

            rng->random_vec(9 * 64 * 1024 + 1);
            result.test_eq("request exceeds output limit", counting_rng.randomize_count(), 9);
            }

         return result;
         }

      Test::Result test_broken_entropy_input()
         {
         Test::Result result(rng_name() + " Broken Entropy Input");

         class Broken_Entropy_Source final : public Botan::Entropy_Source
            {
            public:
               std::string name() const override
                  {
                  return "Broken Entropy Source";
                  }

               size_t poll(Botan::RandomNumberGenerator&) override
                  {
                  throw Botan::Not_Implemented("polling not available");
                  }
            };

         class Insufficient_Entropy_Source final : public Botan::Entropy_Source
            {
            public:
               std::string name() const override
                  {
                  return "Insufficient Entropy Source";
                  }

               size_t poll(Botan::RandomNumberGenerator&) override
                  {
                  return 0;
                  }
            };

         // make sure no output is generated when the entropy input source is broken

         // underlying_rng throws exception
         Botan::Null_RNG broken_entropy_input_rng;
         result.test_eq("Null_RNG not seeded", broken_entropy_input_rng.is_seeded(), false);
         std::unique_ptr<Botan::Stateful_RNG> rng_with_broken_rng = make_rng(broken_entropy_input_rng);

         result.test_throws("broken underlying rng", [&rng_with_broken_rng]() { rng_with_broken_rng->random_vec(16); });

         // entropy_sources throw exception
         std::unique_ptr<Broken_Entropy_Source> broken_entropy_source_1(new Broken_Entropy_Source());
         std::unique_ptr<Broken_Entropy_Source> broken_entropy_source_2(new Broken_Entropy_Source());

         Botan::Entropy_Sources broken_entropy_sources;
         broken_entropy_sources.add_source(std::move(broken_entropy_source_1));
         broken_entropy_sources.add_source(std::move(broken_entropy_source_2));

         std::unique_ptr<Botan::Stateful_RNG> rng_with_broken_es = make_rng(broken_entropy_sources);
         result.test_throws("broken entropy sources", [&rng_with_broken_es]() { rng_with_broken_es->random_vec(16); });

         // entropy source returns insufficient entropy
         Botan::Entropy_Sources insufficient_entropy_sources;
         std::unique_ptr<Insufficient_Entropy_Source> insufficient_entropy_source(new Insufficient_Entropy_Source());
         insufficient_entropy_sources.add_source(std::move(insufficient_entropy_source));

         std::unique_ptr<Botan::Stateful_RNG> rng_with_insufficient_es = make_rng(insufficient_entropy_sources);
         result.test_throws("insufficient entropy source", [&rng_with_insufficient_es]() { rng_with_insufficient_es->random_vec(16); });

         // one of or both underlying_rng and entropy_sources throw exception

         std::unique_ptr<Botan::Stateful_RNG> rng_with_broken_rng_and_good_es =
            make_rng(broken_entropy_input_rng, Botan::Entropy_Sources::global_sources());

         result.test_throws("broken underlying rng but good entropy sources", [&rng_with_broken_rng_and_good_es]()
            { rng_with_broken_rng_and_good_es->random_vec(16); });

         std::unique_ptr<Botan::Stateful_RNG> rng_with_good_rng_and_broken_es =
            make_rng(Test::rng(), broken_entropy_sources);

         result.test_throws("good underlying rng but broken entropy sources", [&rng_with_good_rng_and_broken_es]()
            { rng_with_good_rng_and_broken_es->random_vec(16); });

         std::unique_ptr<Botan::Stateful_RNG> rng_with_broken_rng_and_broken_es =
            make_rng(broken_entropy_input_rng, broken_entropy_sources);

         result.test_throws("underlying rng and entropy sources broken", [&rng_with_broken_rng_and_broken_es]()
            { rng_with_broken_rng_and_broken_es->random_vec(16); });

         return result;
         }

      Test::Result test_check_nonce()
         {
         Test::Result result(rng_name() + " Nonce Check");

         // make sure the nonce has at least security_strength bits
         std::unique_ptr<Botan::Stateful_RNG> rng = create_rng(nullptr, nullptr, 0);

         for(size_t nonce_size : { 0, 4, 8, 16, 31, 32, 34, 64 })
            {
            rng->clear();
            result.test_eq("not seeded", rng->is_seeded(), false);

            const std::vector<uint8_t> nonce(nonce_size);
            rng->initialize_with(nonce.data(), nonce.size());

            if(nonce_size < rng->security_level() / 8)
               {
               result.test_eq("not seeded", rng->is_seeded(), false);
               result.test_throws("invalid nonce size", [&rng]() { rng->random_vec(32); });
               }
            else
               {
               result.test_eq("is seeded", rng->is_seeded(), true);
               rng->random_vec(32);
               }
            }

         return result;
         }

      Test::Result test_prediction_resistance()
         {
         Test::Result result(rng_name() + " Prediction Resistance");

         // set reseed_interval = 1, forcing a reseed for every RNG request
         Request_Counting_RNG counting_rng;
         std::unique_ptr<Botan::Stateful_RNG> rng = make_rng(counting_rng, 1);

         rng->random_vec(16);
         result.test_eq("first request", counting_rng.randomize_count(), size_t(1));

         rng->random_vec(16);
         result.test_eq("second request", counting_rng.randomize_count(), size_t(2));

         rng->random_vec(16);
         result.test_eq("third request", counting_rng.randomize_count(), size_t(3));

         return result;
         }

      Test::Result test_fork_safety()
         {
         Test::Result result(rng_name() + " Fork Safety");

#if defined(BOTAN_TARGET_OS_HAS_POSIX1)
         const size_t reseed_interval = 1024;

         // make sure rng is reseeded after every fork
         Request_Counting_RNG counting_rng;
         std::unique_ptr<Botan::Stateful_RNG> rng = make_rng(counting_rng, reseed_interval);

         rng->random_vec(16);
         result.test_eq("first request", counting_rng.randomize_count(), size_t(1));

         // fork and request from parent and child, both should output different sequences
         size_t count = counting_rng.randomize_count();
         Botan::secure_vector<uint8_t> parent_bytes(16), child_bytes(16);
         int fd[2];
         int rc = ::pipe(fd);
         if(rc != 0)
            {
            result.test_failure("failed to create pipe");
            }

         pid_t pid = ::fork();
         if(pid == -1)
            {
#if defined(BOTAN_TARGET_OS_IS_EMSCRIPTEN)
            result.test_note("failed to fork process");
#else
            result.test_failure("failed to fork process");
#endif
            return result;
            }
         else if(pid != 0)
            {
            // parent process, wait for randomize_count from child's rng
            ::close(fd[1]); // close write end in parent
            ssize_t got = ::read(fd[0], &count, sizeof(count));

            if(got > 0)
               {
               result.test_eq("expected bytes from child", got, sizeof(count));
               result.test_eq("parent not reseeded",  counting_rng.randomize_count(), 1);
               result.test_eq("child reseed occurred", count, 2);
               }
            else
               {
               result.test_failure("Failed to read count size from child process");
               }

            parent_bytes = rng->random_vec(16);
            got = ::read(fd[0], &child_bytes[0], child_bytes.size());

            if(got > 0)
               {
               result.test_eq("expected bytes from child", got, child_bytes.size());
               result.test_ne("parent and child output sequences differ", parent_bytes, child_bytes);
               }
            else
               {
               result.test_failure("Failed to read RNG bytes from child process");
               }
            ::close(fd[0]); // close read end in parent

            // wait for the child to exit
            int status = 0;
            ::waitpid(pid, &status, 0);
            }
         else
            {
            // child process, send randomize_count and first output sequence back to parent
            ::close(fd[0]); // close read end in child
            rng->randomize(&child_bytes[0], child_bytes.size());
            count = counting_rng.randomize_count();
            ssize_t written = ::write(fd[1], &count, sizeof(count));
            try
               {
               rng->randomize(&child_bytes[0], child_bytes.size());
               }
            catch(std::exception& e)
               {
               fprintf(stderr, "%s", e.what());
               }
            written = ::write(fd[1], &child_bytes[0], child_bytes.size());
            BOTAN_UNUSED(written);
            ::close(fd[1]); // close write end in child

            /*
            * We can't call exit because it causes the mlock pool to be freed (#602)
            * We can't call _exit because it makes valgrind think we leaked memory.
            * So instead we execute something that will return 0 for us.
            */
            ::execl("/bin/true", "true", NULL);
            ::_exit(0); // just in case /bin/true isn't available (sandbox?)
            }
#endif
         return result;
         }

      Test::Result test_randomize_with_ts_input()
         {
         Test::Result result(rng_name() + " Randomize With Timestamp Input");

         const size_t request_bytes = 64;
         const std::vector<uint8_t> seed(128);

         // check that randomize_with_ts_input() creates different output based on a timestamp
         // and possibly additional data, such as process id even with identical seeds
         Fixed_Output_RNG fixed_output_rng1(seed);
         Fixed_Output_RNG fixed_output_rng2(seed);

         std::unique_ptr<Botan::Stateful_RNG> rng1 = make_rng(fixed_output_rng1);
         std::unique_ptr<Botan::Stateful_RNG> rng2 = make_rng(fixed_output_rng2);

         Botan::secure_vector<uint8_t> output1(request_bytes);
         Botan::secure_vector<uint8_t> output2(request_bytes);

         rng1->randomize(output1.data(), output1.size());
         rng2->randomize(output2.data(), output2.size());

         result.test_eq("equal output due to same seed", output1, output2);

         rng1->randomize_with_ts_input(output1.data(), output1.size());
         rng2->randomize_with_ts_input(output2.data(), output2.size());

         result.test_ne("output differs due to different timestamp", output1, output2);

         return result;
         }

   };

#endif

#if defined(BOTAN_HAS_HMAC_DRBG) && defined(BOTAN_HAS_SHA2_32)

class HMAC_DRBG_Unit_Tests final : public Stateful_RNG_Tests
   {
   public:
      std::string rng_name() const override { return "HMAC_DRBG"; }

      std::unique_ptr<Botan::Stateful_RNG> create_rng(Botan::RandomNumberGenerator* underlying_rng,
                                                      Botan::Entropy_Sources* underlying_es,
                                                      size_t reseed_interval) override
         {
         std::unique_ptr<Botan::MessageAuthenticationCode> mac =
            Botan::MessageAuthenticationCode::create("HMAC(SHA-256)");

         if(underlying_rng && underlying_es)
            return std::unique_ptr<Botan::Stateful_RNG>(new Botan::HMAC_DRBG(std::move(mac), *underlying_rng, *underlying_es, reseed_interval));
         else if(underlying_rng)
            return std::unique_ptr<Botan::Stateful_RNG>(new Botan::HMAC_DRBG(std::move(mac), *underlying_rng, reseed_interval));
         else if(underlying_es)
            return std::unique_ptr<Botan::Stateful_RNG>(new Botan::HMAC_DRBG(std::move(mac), *underlying_es, reseed_interval));
         else if(reseed_interval == 0)
            return std::unique_ptr<Botan::Stateful_RNG>(new Botan::HMAC_DRBG(std::move(mac)));
         else
            throw Test_Error("Invalid reseed interval in HMAC_DRBG unit test");
         }

      Test::Result test_max_number_of_bytes_per_request() override
         {
         Test::Result result("HMAC_DRBG max_number_of_bytes_per_request");

         const std::string mac_string = "HMAC(SHA-256)";

         Request_Counting_RNG counting_rng;

         result.test_throws("HMAC_DRBG does not accept 0 for max_number_of_bytes_per_request",
                            [&mac_string, &counting_rng]()
            {
            Botan::HMAC_DRBG failing_rng(Botan::MessageAuthenticationCode::create(mac_string), counting_rng, 2, 0);
            });

         result.test_throws("HMAC_DRBG does not accept values higher than 64KB for max_number_of_bytes_per_request",
                            [&mac_string, &counting_rng]()
            {
            Botan::HMAC_DRBG failing_rng(Botan::MessageAuthenticationCode::create(mac_string), counting_rng, 2, 64 * 1024 + 1);
            });

         // set reseed_interval to 1 so we can test that a long request is split
         // into multiple, max_number_of_bytes_per_request long requests
         // for each smaller request, reseed_check() calls counting_rng::randomize(),
         // which we can compare with
         Botan::HMAC_DRBG rng(Botan::MessageAuthenticationCode::create(mac_string), counting_rng, 1, 64);

         rng.random_vec(63);
         result.test_eq("one request", counting_rng.randomize_count(), 1);

         rng.clear();
         counting_rng.clear();

         rng.random_vec(64);
         result.test_eq("one request", counting_rng.randomize_count(), 1);

         rng.clear();
         counting_rng.clear();

         rng.random_vec(65);
         result.test_eq("two requests", counting_rng.randomize_count(), 2);

         rng.clear();
         counting_rng.clear();

         rng.random_vec(1025);
         result.test_eq("17 requests", counting_rng.randomize_count(), 17);

         return result;
         }

      Test::Result test_security_level() override
         {
         Test::Result result("HMAC_DRBG Security Level");

         std::vector<std::string> approved_hash_fns { "SHA-160", "SHA-224", "SHA-256", "SHA-512/256", "SHA-384", "SHA-512" };
         std::vector<uint32_t> security_strengths { 128, 192, 256, 256, 256, 256 };

         for(size_t i = 0; i < approved_hash_fns.size(); ++i)
            {
            std::string hash_fn = approved_hash_fns[i];
            std::string mac_name = "HMAC(" + hash_fn + ")";
            auto mac = Botan::MessageAuthenticationCode::create(mac_name);
            if(!mac)
               {
               result.note_missing(mac_name);
               continue;
               }

            Botan::HMAC_DRBG rng(std::move(mac));
            result.test_eq(hash_fn + " security level", rng.security_level(), security_strengths[i]);
            }

         return result;
         }

      Test::Result test_reseed_kat() override
         {
         Test::Result result("HMAC_DRBG Reseed KAT");

         Request_Counting_RNG counting_rng;
         std::unique_ptr<Botan::Stateful_RNG> rng = make_rng(counting_rng, 2);

         const Botan::secure_vector<uint8_t> seed_input(
            {
            0x00, 0x11, 0x22, 0x33, 0x44, 0x55, 0x66, 0x77, 0x88, 0x99, 0xAA, 0xBB, 0xCC, 0xDD, 0xEE, 0xFF,
            0x00, 0x11, 0x22, 0x33, 0x44, 0x55, 0x66, 0x77, 0x88, 0x99, 0xAA, 0xBB, 0xCC, 0xDD, 0xEE, 0xFF
            });

         result.test_eq("is_seeded", rng->is_seeded(), false);

         rng->initialize_with(seed_input.data(), seed_input.size());

         Botan::secure_vector<uint8_t> out(32);

         rng->randomize(out.data(), out.size());
         result.test_eq("underlying RNG calls", counting_rng.randomize_count(), size_t(0));
         result.test_eq("out before reseed", out, "48D3B45AAB65EF92CCFCB9427EF20C90297065ECC1B8A525BFE4DC6FF36D0E38");

         // reseed must happen here
         rng->randomize(out.data(), out.size());
         result.test_eq("underlying RNG calls", counting_rng.randomize_count(), size_t(1));
         result.test_eq("out after reseed", out, "2F8FCA696832C984781123FD64F4B20C7379A25C87AB29A21C9BF468B0081CE2");

         return result;
         }

   };

BOTAN_REGISTER_TEST("hmac_drbg_unit", HMAC_DRBG_Unit_Tests);

#endif

#if defined(BOTAN_HAS_CHACHA_RNG)

class ChaCha_RNG_Unit_Tests final : public Stateful_RNG_Tests
   {
   public:

      std::string rng_name() const override { return "ChaCha_RNG"; }

      std::unique_ptr<Botan::Stateful_RNG> create_rng(Botan::RandomNumberGenerator* underlying_rng,
                                                      Botan::Entropy_Sources* underlying_es,
                                                      size_t reseed_interval) override
         {
         if(underlying_rng && underlying_es)
            return std::unique_ptr<Botan::Stateful_RNG>(new Botan::ChaCha_RNG(*underlying_rng, *underlying_es, reseed_interval));
         else if(underlying_rng)
            return std::unique_ptr<Botan::Stateful_RNG>(new Botan::ChaCha_RNG(*underlying_rng, reseed_interval));
         else if(underlying_es)
            return std::unique_ptr<Botan::Stateful_RNG>(new Botan::ChaCha_RNG(*underlying_es, reseed_interval));
         else if(reseed_interval == 0)
            return std::unique_ptr<Botan::Stateful_RNG>(new Botan::ChaCha_RNG());
         else
            throw Test_Error("Invalid reseed interval in ChaCha_RNG unit test");
         }

      Test::Result test_security_level() override
         {
         Test::Result result("ChaCha_RNG Security Level");
         Botan::ChaCha_RNG rng;
         result.test_eq("Expected security level", rng.security_level(), size_t(256));
         return result;
         }

      Test::Result test_max_number_of_bytes_per_request() override
         {
         Test::Result result("ChaCha_RNG max_number_of_bytes_per_request");
         // ChaCha_RNG doesn't have this notion
         return result;
         }

      Test::Result test_reseed_kat() override
         {
         Test::Result result("ChaCha_RNG Reseed KAT");

         Request_Counting_RNG counting_rng;
         std::unique_ptr<Botan::Stateful_RNG> rng = make_rng(counting_rng, 2);

         const Botan::secure_vector<uint8_t> seed_input(32);

         result.test_eq("is_seeded", rng->is_seeded(), false);

         rng->initialize_with(seed_input.data(), seed_input.size());

         Botan::secure_vector<uint8_t> out(32);

         rng->randomize(out.data(), out.size());
         result.test_eq("underlying RNG calls", counting_rng.randomize_count(), size_t(0));
         result.test_eq("out before reseed", out, "1F0E6F13429D5073B59C057C37CBE9587740A0A894D247E2596C393CE91DDC6F");

         // reseed must happen here
         rng->randomize(out.data(), out.size());
         result.test_eq("underlying RNG calls", counting_rng.randomize_count(), size_t(1));
         result.test_eq("out after reseed", out, "F2CAE73F22684D5D773290B48FDCDA0E6C0661EBA0A854AFEC922832BDBB9C49");

         return result;
         }

   };

BOTAN_REGISTER_TEST("chacha_rng_unit", ChaCha_RNG_Unit_Tests);

#endif

#if defined(BOTAN_HAS_AUTO_RNG)

class AutoSeeded_RNG_Tests final : public Test
   {
   private:
      Test::Result auto_rng_tests()
         {
         Test::Result result("AutoSeeded_RNG");

         Botan::Entropy_Sources no_entropy_for_you;
         Botan::Null_RNG null_rng;

         result.test_eq("Null_RNG is null", null_rng.is_seeded(), false);

         try
            {
            Botan::AutoSeeded_RNG rng(no_entropy_for_you);
            result.test_failure("AutoSeeded_RNG should have rejected useless entropy source");
            }
         catch(Botan::PRNG_Unseeded&)
            {
            result.test_success("AutoSeeded_RNG rejected empty entropy source");
            }

         try
            {
            Botan::AutoSeeded_RNG rng(null_rng);
            }
         catch(Botan::PRNG_Unseeded&)
            {
            result.test_success("AutoSeeded_RNG rejected useless RNG");
            }

         try
            {
            Botan::AutoSeeded_RNG rng(null_rng,
                                      no_entropy_for_you);
            }
         catch(Botan::PRNG_Unseeded&)
            {
            result.test_success("AutoSeeded_RNG rejected useless RNG+entropy sources");
            }

         Botan::AutoSeeded_RNG rng;

         result.test_eq("AutoSeeded_RNG::name", rng.name(),
                        std::string("HMAC_DRBG(") + BOTAN_AUTO_RNG_HMAC + ")");

         result.confirm("AutoSeeded_RNG starts seeded", rng.is_seeded());
         rng.random_vec(16); // generate and discard output
         rng.clear();
         result.test_eq("AutoSeeded_RNG unseeded after calling clear", rng.is_seeded(), false);

         // AutoSeeded_RNG automatically reseeds as required:
         rng.random_vec(16);
         result.confirm("AutoSeeded_RNG can be reseeded", rng.is_seeded());

         result.confirm("AutoSeeded_RNG ", rng.is_seeded());
         rng.random_vec(16); // generate and discard output
         rng.clear();
         result.test_eq("AutoSeeded_RNG unseeded after calling clear", rng.is_seeded(), false);

         const size_t no_entropy_bits = rng.reseed(no_entropy_for_you, 256, std::chrono::milliseconds(300));
         result.test_eq("AutoSeeded_RNG can't reseed from nothing", no_entropy_bits, 0);
         result.test_eq("AutoSeeded_RNG still unseeded", rng.is_seeded(), false);

         rng.random_vec(16); // generate and discard output
         result.confirm("AutoSeeded_RNG can be reseeded", rng.is_seeded());

         rng.clear();

         return result;
         }

   public:
      std::vector<Test::Result> run() override
         {
         std::vector<Test::Result> results;
         results.push_back(auto_rng_tests());
         return results;
         }
   };

BOTAN_REGISTER_TEST("auto_rng_unit", AutoSeeded_RNG_Tests);

#endif

#if defined(BOTAN_HAS_SYSTEM_RNG)

class System_RNG_Tests final : public Test
   {
   public:
      std::vector<Test::Result> run() override
         {
         Test::Result result("System_RNG");

         Botan::System_RNG rng;

         result.test_gte("Some non-empty name is returned", rng.name().size(), 1);

         result.confirm("System RNG always seeded", rng.is_seeded());
         rng.clear(); // clear is a noop for system rng
         result.confirm("System RNG always seeded", rng.is_seeded());

         rng.reseed(Botan::Entropy_Sources::global_sources(),
                    256,
                    std::chrono::milliseconds(100));

         for(size_t i = 0; i != 128; ++i)
            {
            std::vector<uint8_t> out_buf(i);
            rng.randomize(out_buf.data(), out_buf.size());
            rng.add_entropy(out_buf.data(), out_buf.size());
            }

         return std::vector<Test::Result>{result};
         }
   };

BOTAN_REGISTER_TEST("system_rng", System_RNG_Tests);

#endif

#if defined(BOTAN_HAS_RDRAND_RNG)

class RDRAND_RNG_Tests final : public Test
   {
   public:
      std::vector<Test::Result> run() override
         {
         Test::Result result("RDRAND_RNG");

         if(Botan::RDRAND_RNG::available())
            {
            Botan::RDRAND_RNG rng;

            result.test_eq("Expected name", rng.name(), "RDRAND");
            result.confirm("RDRAND always seeded", rng.is_seeded());
            rng.clear(); // clear is a noop for rdrand
            result.confirm("RDRAND always seeded", rng.is_seeded());

            size_t reseed_bits = rng.reseed(Botan::Entropy_Sources::global_sources(),
                                            256,
                                            std::chrono::seconds(1));
            result.test_eq("RDRAND cannot consume inputs", reseed_bits, size_t(0));

            /*
            RDRAND_RNG ignores add_entropy calls - confirm this by passing
            an invalid ptr/length field to add_entropy. If it examined its
            arguments, it would crash...
            */
            const uint8_t* invalid_ptr = reinterpret_cast<const uint8_t*>(static_cast<uintptr_t>(0xDEADC0DE));
            const size_t invalid_ptr_len = 64*1024;
            rng.add_entropy(invalid_ptr, invalid_ptr_len);

            for(size_t i = 0; i != 128; ++i)
               {
               std::vector<uint8_t> out_buf(i);
               rng.randomize(out_buf.data(), out_buf.size());
               }
            }
         else
            {
            result.test_throws("RDRAND_RNG throws if instruction not available",
                               []() { Botan::RDRAND_RNG rng; });
            }


         return std::vector<Test::Result>{result};
         }
   };

BOTAN_REGISTER_TEST("rdrand_rng", RDRAND_RNG_Tests);

#endif

}

}