Let the entropy module be optional

It was previously required by the rng module, but this isn't really
necessary, especially for anyone who is just using the system RNG.
(And/or NIST DRBGs seeded with the system RNG.)

src/cli/cli_rng.cpp

@@ -5,11 +5,15 @@
 */
 
 #include "cli.h"
-#include <botan/entropy_src.h>
+
 #include <botan/hex.h>
 #include <botan/rng.h>
 #include <botan/internal/parsing.h>
 
+#if defined(BOTAN_HAS_ENTROPY_SOURCE)
+   #include <botan/entropy_src.h>
+#endif
+
 #if defined(BOTAN_HAS_AUTO_SEEDING_RNG)
    #include <botan/auto_rng.h>
 #endif
@@ -56,7 +60,11 @@ std::shared_ptr<Botan::RandomNumberGenerator> cli_make_rng(const std::string& rn
       std::shared_ptr<Botan::RandomNumberGenerator> rng;
 
       if(rng_type == "entropy") {
+   #if defined(BOTAN_HAS_ENTROPY_SOURCE)
          rng = std::make_shared<Botan::AutoSeeded_RNG>(Botan::Entropy_Sources::global_sources());
+   #else
+         throw CLI_Error_Unsupported("Entropy sources not included in this build");
+   #endif
       } else {
          rng = std::make_shared<Botan::AutoSeeded_RNG>();
       }

src/cli/entropy.cpp

@@ -7,14 +7,18 @@
 #include "../tests/test_rng.h"  // FIXME
 #include "cli.h"
 
-#include <botan/entropy_src.h>
+#if defined(BOTAN_HAS_ENTROPY_SOURCE)
+   #include <botan/entropy_src.h>
+#endif
 
 #if defined(BOTAN_HAS_COMPRESSION)
    #include <botan/compression.h>
 #endif
 
 namespace Botan_CLI {
 
+#if defined(BOTAN_HAS_ENTROPY_SOURCE)
+
 class Entropy final : public Command {
    public:
       Entropy() : Command("entropy --truncate-at=128 source") {}
@@ -50,7 +54,7 @@ class Entropy final : public Command {
             output() << "Polling " << source << " gathered " << sample.size() << " bytes in " << rng.samples()
                      << " outputs with estimated entropy " << entropy_estimate << "\n";
 
-#if defined(BOTAN_HAS_COMPRESSION)
+   #if defined(BOTAN_HAS_COMPRESSION)
             if(!sample.empty()) {
                auto comp = Botan::Compression_Algorithm::create("zlib");
                if(comp) {
@@ -69,7 +73,7 @@ class Entropy final : public Command {
                   }
                }
             }
-#endif
+   #endif
 
             if(sample.size() <= truncate_sample) {
                output() << Botan::hex_encode(sample) << "\n";
@@ -82,4 +86,6 @@ class Entropy final : public Command {
 
 BOTAN_REGISTER_COMMAND("entropy", Entropy);
 
+#endif
+
 }  // namespace Botan_CLI

src/lib/prov/pkcs11/p11_randomgenerator.h

@@ -9,7 +9,6 @@
 #ifndef BOTAN_P11_RNG_H_
 #define BOTAN_P11_RNG_H_
 
-#include <botan/entropy_src.h>
 #include <botan/p11_types.h>
 #include <botan/rng.h>
 

src/lib/rng/auto_rng/auto_rng.cpp

@@ -6,11 +6,12 @@
 
 #include <botan/auto_rng.h>
 
-#include <botan/entropy_src.h>
 #include <botan/hmac_drbg.h>
 #include <botan/internal/loadstor.h>
 
-#include <array>
+#if defined(BOTAN_HAS_ENTROPY_SOURCE)
+   #include <botan/entropy_src.h>
+#endif
 
 #if defined(BOTAN_HAS_SYSTEM_RNG)
    #include <botan/system_rng.h>
@@ -27,7 +28,7 @@ std::unique_ptr<MessageAuthenticationCode> auto_rng_hmac() {
    };
 
    for(const auto& hmac : possible_auto_rng_hmacs) {
-      if(auto mac = MessageAuthenticationCode::create_or_throw(hmac)) {
+      if(auto mac = MessageAuthenticationCode::create(hmac)) {
          return mac;
       }
    }
@@ -60,13 +61,17 @@ AutoSeeded_RNG::AutoSeeded_RNG(RandomNumberGenerator& underlying_rng,
    force_reseed();
 }
 
-AutoSeeded_RNG::AutoSeeded_RNG(size_t reseed_interval) :
+AutoSeeded_RNG::AutoSeeded_RNG(size_t reseed_interval) {
 #if defined(BOTAN_HAS_SYSTEM_RNG)
-      AutoSeeded_RNG(system_rng(), reseed_interval)
+   m_rng = std::make_unique<HMAC_DRBG>(auto_rng_hmac(), system_rng(), reseed_interval);
+#elif defined(BOTAN_HAS_ENTROPY_SOURCE)
+   m_rng = std::make_unique<HMAC_DRBG>(auto_rng_hmac(), Entropy_Sources::global_sources(), reseed_interval);
 #else
-      AutoSeeded_RNG(Entropy_Sources::global_sources(), reseed_interval)
+   BOTAN_UNUSED(reseed_interval);
+   throw Not_Implemented("AutoSeeded_RNG default constructor not available due to no RNG or entropy sources");
 #endif
-{
+
+   force_reseed();
 }
 
 void AutoSeeded_RNG::force_reseed() {

src/lib/rng/info.txt

@@ -1,7 +1,3 @@
-<requires>
-entropy
-</requires>
-
 <module_info>
 name -> "Random Number Generators"
 brief -> "Implementations of Random Number Generators"

src/lib/rng/rng.cpp

@@ -6,9 +6,12 @@
 
 #include <botan/rng.h>
 
-#include <botan/entropy_src.h>
 #include <botan/internal/loadstor.h>
 
+#if defined(BOTAN_HAS_ENTROPY_SOURCE)
+   #include <botan/entropy_src.h>
+#endif
+
 #if defined(BOTAN_HAS_SYSTEM_RNG)
    #include <botan/system_rng.h>
 #endif
@@ -47,10 +50,14 @@ void RandomNumberGenerator::randomize_with_ts_input(std::span<uint8_t> output) {
 
 size_t RandomNumberGenerator::reseed(Entropy_Sources& srcs, size_t poll_bits, std::chrono::milliseconds poll_timeout) {
    if(this->accepts_input()) {
+#if defined(BOTAN_HAS_ENTROPY_SOURCE)
       return srcs.poll(*this, poll_bits, poll_timeout);
-   } else {
-      return 0;
+#else
+      BOTAN_UNUSED(srcs, poll_bits, poll_timeout);
+#endif
    }
+
+   return 0;
 }
 
 void RandomNumberGenerator::reseed_from_rng(RandomNumberGenerator& rng, size_t poll_bits) {

src/tests/test_entropy.cpp

@@ -6,14 +6,19 @@
 
 #include "test_rng.h"
 #include "tests.h"
-#include <botan/entropy_src.h>
+
+#if defined(BOTAN_HAS_ENTROPY_SOURCE)
+   #include <botan/entropy_src.h>
+#endif
 
 #if defined(BOTAN_HAS_COMPRESSION)
    #include <botan/compression.h>
 #endif
 
 namespace Botan_Tests {
 
+#if defined(BOTAN_HAS_ENTROPY_SOURCE)
+
 namespace {
 
 class Entropy_Source_Tests final : public Test {
@@ -44,7 +49,7 @@ class Entropy_Source_Tests final : public Test {
 
                result.test_note("poll result", rng.seed_material());
 
-#if defined(BOTAN_HAS_COMPRESSION)
+   #if defined(BOTAN_HAS_COMPRESSION)
                if(!rng.seed_material().empty()) {
                   /*
                   * Skip bzip2 both due to OS X problem (GH #394) and because bzip2's
@@ -102,7 +107,7 @@ class Entropy_Source_Tests final : public Test {
                      }
                   }
                }
-#endif
+   #endif
             } catch(std::exception& e) {
                result.test_failure("during entropy collection test", e.what());
             }
@@ -119,4 +124,6 @@ BOTAN_REGISTER_TEST("rng", "entropy", Entropy_Source_Tests);
 
 }  // namespace
 
+#endif
+
 }  // namespace Botan_Tests

src/tests/test_pkcs11_high_level.cpp

@@ -26,6 +26,10 @@
    #include <botan/der_enc.h>
 #endif
 
+#if defined(BOTAN_HAS_ENTROPY_SOURCE)
+   #include <botan/entropy_src.h>
+#endif
+
 #if defined(BOTAN_HAS_PUBLIC_KEY_CRYPTO)
    #include <botan/pubkey.h>
 #endif
@@ -1404,9 +1408,11 @@ Test::Result test_rng_add_entropy() {
    p11_rng.clear();
    result.confirm("RNG ignores call to clear", p11_rng.is_seeded());
 
+   #if defined(BOTAN_HAS_ENTROPY_SOURCE)
    result.test_eq("RNG ignores calls to reseed",
                   p11_rng.reseed(Botan::Entropy_Sources::global_sources(), 256, std::chrono::milliseconds(300)),
                   0);
+   #endif
 
    auto rng = Test::new_rng(__func__);
    auto random = rng->random_vec(20);

src/tests/test_rng_behavior.cpp

@@ -146,6 +146,7 @@ class Stateful_RNG_Tests : public Test {
       Test::Result test_broken_entropy_input() {
          Test::Result result(rng_name() + " Broken Entropy Input");
 
+   #if defined(BOTAN_HAS_ENTROPY_SOURCE)
          class Broken_Entropy_Source final : public Botan::Entropy_Source {
             public:
                std::string name() const override { return "Broken Entropy Source"; }
@@ -161,6 +162,7 @@ class Stateful_RNG_Tests : public Test {
 
                size_t poll(Botan::RandomNumberGenerator& /*rng*/) override { return 0; }
          };
+   #endif
 
          // make sure no output is generated when the entropy input source is broken
 
@@ -171,6 +173,8 @@ class Stateful_RNG_Tests : public Test {
 
          result.test_throws("broken underlying rng", [&rng_with_broken_rng]() { rng_with_broken_rng->random_vec(16); });
 
+   #if defined(BOTAN_HAS_ENTROPY_SOURCE)
+
          // entropy_sources throw exception
          auto broken_entropy_source_1 = std::make_unique<Broken_Entropy_Source>();
          auto broken_entropy_source_2 = std::make_unique<Broken_Entropy_Source>();
@@ -209,6 +213,7 @@ class Stateful_RNG_Tests : public Test {
          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);
          });
+   #endif
 
          return result;
       }
@@ -678,29 +683,32 @@ class AutoSeeded_RNG_Tests final : public Test {
       static 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");
+            Botan::AutoSeeded_RNG rng(null_rng);
          } catch(Botan::PRNG_Unseeded&) {
-            result.test_success("AutoSeeded_RNG rejected empty entropy source");
+            result.test_success("AutoSeeded_RNG rejected useless RNG");
          }
 
+   #if defined(BOTAN_HAS_ENTROPY_SOURCE)
+         Botan::Entropy_Sources no_entropy_for_you;
+
          try {
-            Botan::AutoSeeded_RNG rng(null_rng);
+            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 useless RNG");
+            result.test_success("AutoSeeded_RNG rejected empty entropy source");
          }
 
          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");
          }
+   #endif
 
          Botan::AutoSeeded_RNG rng;
 
@@ -720,9 +728,11 @@ class AutoSeeded_RNG_Tests final : public Test {
          rng.clear();
          result.test_eq("AutoSeeded_RNG unseeded after calling clear", rng.is_seeded(), false);
 
+   #if defined(BOTAN_HAS_ENTROPY_SOURCE)
          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);
+   #endif
 
          rng.random_vec(16);  // generate and discard output
          result.confirm("AutoSeeded_RNG can be reseeded", rng.is_seeded());
@@ -767,7 +777,9 @@ class System_RNG_Tests final : public Test {
          rng.clear();  // clear is a noop for system rng
          result.confirm("System RNG always seeded", rng.is_seeded());
 
+   #if defined(BOTAN_HAS_ENTROPY_SOURCE)
          rng.reseed(Botan::Entropy_Sources::global_sources(), 256, std::chrono::milliseconds(100));
+   #endif
 
          for(size_t i = 0; i != 128; ++i) {
             std::vector<uint8_t> out_buf(i);
@@ -813,8 +825,10 @@ class Processor_RNG_Tests final : public Test {
             rng.clear();  // clear is a noop for rdrand
             result.confirm("CPU RNG always seeded", rng.is_seeded());
 
+   #if defined(BOTAN_HAS_ENTROPY_SOURCE)
             size_t reseed_bits = rng.reseed(Botan::Entropy_Sources::global_sources(), 256, std::chrono::seconds(1));
             result.test_eq("CPU RNG cannot consume inputs", reseed_bits, size_t(0));
+   #endif
 
             /*
             Processor_RNG ignores add_entropy calls - confirm this by passing