Add RandomNumberGenerator::accepts_input

12 files changed, 91 insertions, 17 deletions

diff --git a/src/lib/prov/pkcs11/p11_randomgenerator.h b/src/lib/prov/pkcs11/p11_randomgenerator.h
index cab9b77c4..82b7d9f48 100644
--- a/src/lib/prov/pkcs11/p11_randomgenerator.h
+++ b/src/lib/prov/pkcs11/p11_randomgenerator.h
@@ -57,6 +57,9 @@ class BOTAN_PUBLIC_API(2,0) PKCS11_RNG final : public Hardware_RNG
       /// Calls `C_SeedRandom` to add entropy to the random generation function of the token/middleware
       void add_entropy(const uint8_t in[], std::size_t length) override;
 
+      // C_SeedRandom may suceed
+      bool accepts_input() const override { return true; }
+
    private:
       const std::reference_wrapper<Session> m_session;
    };
diff --git a/src/lib/prov/tpm/tpm.h b/src/lib/prov/tpm/tpm.h
index b6e220935..7eaf2140c 100644
--- a/src/lib/prov/tpm/tpm.h
+++ b/src/lib/prov/tpm/tpm.h
@@ -78,6 +78,8 @@ class BOTAN_PUBLIC_API(2,0) TPM_RNG final : public Hardware_RNG
    public:
       TPM_RNG(TPM_Context& ctx) : m_ctx(ctx) {}
 
+      bool accepts_input() const override { return true; }
+
       void add_entropy(const uint8_t in[], size_t in_len) override
          {
          m_ctx.stir_random(in, in_len);
diff --git a/src/lib/rng/auto_rng/auto_rng.h b/src/lib/rng/auto_rng/auto_rng.h
index 49663cbea..8cb2c4a12 100644
--- a/src/lib/rng/auto_rng/auto_rng.h
+++ b/src/lib/rng/auto_rng/auto_rng.h
@@ -27,6 +27,8 @@ class BOTAN_PUBLIC_API(2,0) AutoSeeded_RNG final : public RandomNumberGenerator
 
       bool is_seeded() const override;
 
+      bool accepts_input() const override { return true; }
+
       /**
       * Mark state as requiring a reseed on next use
       */
diff --git a/src/lib/rng/rdrand_rng/rdrand_rng.h b/src/lib/rng/rdrand_rng/rdrand_rng.h
index 3f6a33b64..181edcd47 100644
--- a/src/lib/rng/rdrand_rng/rdrand_rng.h
+++ b/src/lib/rng/rdrand_rng/rdrand_rng.h
@@ -34,6 +34,8 @@ class BOTAN_PUBLIC_API(2,0) RDRAND_RNG final : public Hardware_RNG
       */
       static bool available();
 
+      bool accepts_input() const override { return false; }
+
       /**
       * Constructor will throw if CPU does not have RDRAND bit set
       */
diff --git a/src/lib/rng/rng.cpp b/src/lib/rng/rng.cpp
index 2cf3b7b81..2947ac629 100644
--- a/src/lib/rng/rng.cpp
+++ b/src/lib/rng/rng.cpp
@@ -17,15 +17,22 @@ namespace Botan {
 
 void RandomNumberGenerator::randomize_with_ts_input(uint8_t output[], size_t output_len)
    {
-   /*
-   Form additional input which is provided to the PRNG implementation
-   to paramaterize the KDF output.
-   */
-   uint8_t additional_input[16] = { 0 };
-   store_le(OS::get_system_timestamp_ns(), additional_input);
-   store_le(OS::get_high_resolution_clock(), additional_input + 8);
+   if(this->accepts_input())
+      {
+      /*
+      Form additional input which is provided to the PRNG implementation
+      to paramaterize the KDF output.
+      */
+      uint8_t additional_input[16] = { 0 };
+      store_le(OS::get_system_timestamp_ns(), additional_input);
+      store_le(OS::get_high_resolution_clock(), additional_input + 8);
 
-   randomize_with_input(output, output_len, additional_input, sizeof(additional_input));
+      this->randomize_with_input(output, output_len, additional_input, sizeof(additional_input));
+      }
+   else
+      {
+      this->randomize(output, output_len);
+      }
    }
 
 void RandomNumberGenerator::randomize_with_input(uint8_t output[], size_t output_len,
@@ -39,14 +46,24 @@ size_t RandomNumberGenerator::reseed(Entropy_Sources& srcs,
                                      size_t poll_bits,
                                      std::chrono::milliseconds poll_timeout)
    {
-   return srcs.poll(*this, poll_bits, poll_timeout);
+   if(this->accepts_input())
+      {
+      return srcs.poll(*this, poll_bits, poll_timeout);
+      }
+   else
+      {
+      return 0;
+      }
    }
 
 void RandomNumberGenerator::reseed_from_rng(RandomNumberGenerator& rng, size_t poll_bits)
    {
-   secure_vector<uint8_t> buf(poll_bits / 8);
-   rng.randomize(buf.data(), buf.size());
-   this->add_entropy(buf.data(), buf.size());
+   if(this->accepts_input())
+      {
+      secure_vector<uint8_t> buf(poll_bits / 8);
+      rng.randomize(buf.data(), buf.size());
+      this->add_entropy(buf.data(), buf.size());
+      }
    }
 
 RandomNumberGenerator* RandomNumberGenerator::make_rng()
diff --git a/src/lib/rng/rng.h b/src/lib/rng/rng.h
index ec8557477..db42c8cf7 100644
--- a/src/lib/rng/rng.h
+++ b/src/lib/rng/rng.h
@@ -42,6 +42,15 @@ class BOTAN_PUBLIC_API(2,0) RandomNumberGenerator
       virtual void randomize(uint8_t output[], size_t length) = 0;
 
       /**
+      * Returns false if it is known that this RNG object is not able to accept
+      * externally provided inputs (via add_entropy, randomize_with_input, etc).
+      * In this case, any such provided inputs are ignored.
+      *
+      * If this function returns true, then inputs may or may not be accepted.
+      */
+      virtual bool accepts_input() const = 0;
+
+      /**
       * Incorporate some additional data into the RNG state. For
       * example adding nonces or timestamps from a peer's protocol
       * message can help hedge against VM state rollback attacks.
@@ -190,6 +199,8 @@ class BOTAN_PUBLIC_API(2,0) Null_RNG final : public RandomNumberGenerator
    public:
       bool is_seeded() const override { return false; }
 
+      bool accepts_input() const override { return false; }
+
       void clear() override {}
 
       void randomize(uint8_t[], size_t) override
@@ -217,6 +228,12 @@ class BOTAN_PUBLIC_API(2,0) Serialized_RNG final : public RandomNumberGenerator
          m_rng->randomize(out, len);
          }
 
+      bool accepts_input() const override
+         {
+         lock_guard_type<mutex_type> lock(m_mutex);
+         return m_rng->accepts_input();
+         }
+
       bool is_seeded() const override
          {
          lock_guard_type<mutex_type> lock(m_mutex);
diff --git a/src/lib/rng/stateful_rng/stateful_rng.h b/src/lib/rng/stateful_rng/stateful_rng.h
index 18697ae23..9bf04327a 100644
--- a/src/lib/rng/stateful_rng/stateful_rng.h
+++ b/src/lib/rng/stateful_rng/stateful_rng.h
@@ -75,6 +75,8 @@ class BOTAN_PUBLIC_API(2,0) Stateful_RNG : public RandomNumberGenerator
 
       bool is_seeded() const override final;
 
+      bool accepts_input() const override final { return true; }
+
       /**
       * Mark state as requiring a reseed on next use
       */
diff --git a/src/lib/rng/system_rng/system_rng.cpp b/src/lib/rng/system_rng/system_rng.cpp
index c3b37ea9c..5a55e0a83 100644
--- a/src/lib/rng/system_rng/system_rng.cpp
+++ b/src/lib/rng/system_rng/system_rng.cpp
@@ -51,6 +51,7 @@ class System_RNG_Impl final : public RandomNumberGenerator
 
       void add_entropy(const uint8_t[], size_t) override { /* ignored */ }
       bool is_seeded() const override { return true; }
+      bool accepts_input() const override { return false; }
       void clear() override { /* not possible */ }
       std::string name() const override { return "RtlGenRandom"; }
    private:
@@ -98,6 +99,7 @@ class System_RNG_Impl final : public RandomNumberGenerator
          }
 
       bool is_seeded() const override { return true; }
+      bool accepts_input() const override { return false; }
       void clear() override { /* not possible */ }
       std::string name() const override { return "crypto_ng"; }
    private:
@@ -116,6 +118,7 @@ class System_RNG_Impl final : public RandomNumberGenerator
          ::arc4random_buf(buf, len);
          }
 
+      bool accepts_input() const override { return false; }
       void add_entropy(const uint8_t[], size_t) override { /* ignored */ }
       bool is_seeded() const override { return true; }
       void clear() override { /* not possible */ }
@@ -137,12 +140,19 @@ class System_RNG_Impl final : public RandomNumberGenerator
 
          m_fd = ::open(BOTAN_SYSTEM_RNG_DEVICE, O_RDWR | O_NOCTTY);
 
-         /*
-         Cannot open in read-write mode. Fall back to read-only,
-         calls to add_entropy will fail, but randomize will work
-         */
-         if(m_fd < 0)
+         if(m_fd >= 0)
+            {
+            m_writable = true;
+            }
+         else
+            {
+            /*
+            Cannot open in read-write mode. Fall back to read-only,
+            calls to add_entropy will fail, but randomize will work
+            */
             m_fd = ::open(BOTAN_SYSTEM_RNG_DEVICE, O_RDONLY | O_NOCTTY);
+            m_writable = false;
+            }
 
          if(m_fd < 0)
             throw Exception("System_RNG failed to open RNG device");
@@ -157,10 +167,12 @@ class System_RNG_Impl final : public RandomNumberGenerator
       void randomize(uint8_t buf[], size_t len) override;
       void add_entropy(const uint8_t in[], size_t length) override;
       bool is_seeded() const override { return true; }
+      bool accepts_input() const override { return m_writable; }
       void clear() override { /* not possible */ }
       std::string name() const override { return BOTAN_SYSTEM_RNG_DEVICE; }
    private:
       int m_fd;
+      bool m_writable;
    };
 
 void System_RNG_Impl::randomize(uint8_t buf[], size_t len)
@@ -185,6 +197,9 @@ void System_RNG_Impl::randomize(uint8_t buf[], size_t len)
 
 void System_RNG_Impl::add_entropy(const uint8_t input[], size_t len)
    {
+   if(!m_writable)
+      return;
+
    while(len)
       {
       ssize_t got = ::write(m_fd, input, len);
diff --git a/src/lib/rng/system_rng/system_rng.h b/src/lib/rng/system_rng/system_rng.h
index 4e3beaf9f..e0f0181ca 100644
--- a/src/lib/rng/system_rng/system_rng.h
+++ b/src/lib/rng/system_rng/system_rng.h
@@ -33,6 +33,8 @@ class BOTAN_PUBLIC_API(2,0) System_RNG final : public RandomNumberGenerator
 
       bool is_seeded() const override { return system_rng().is_seeded(); }
 
+      bool accepts_input() const override { return system_rng().accepts_input(); }
+
       void clear() override { system_rng().clear(); }
    };
 
diff --git a/src/tests/test_newhope.cpp b/src/tests/test_newhope.cpp
index 38e1539ce..be75ebeb7 100644
--- a/src/tests/test_newhope.cpp
+++ b/src/tests/test_newhope.cpp
@@ -71,6 +71,8 @@ class NEWHOPE_RNG final : public Botan::RandomNumberGenerator
          return true;
          }
 
+      bool accepts_input() const override { return false; }
+
       void add_entropy(const uint8_t[], size_t) override
          {
          /* ignored */
diff --git a/src/tests/test_rng.h b/src/tests/test_rng.h
index 9ac93577b..942277050 100644
--- a/src/tests/test_rng.h
+++ b/src/tests/test_rng.h
@@ -29,6 +29,8 @@ class Fixed_Output_RNG : public Botan::RandomNumberGenerator
          return !m_buf.empty();
          }
 
+      bool accepts_input() const override { return true; }
+
       size_t reseed(Botan::Entropy_Sources&,
                     size_t,
                     std::chrono::milliseconds) override
@@ -116,6 +118,8 @@ class Fixed_Output_Position_RNG final : public Fixed_Output_RNG
             }
          }
 
+      bool accepts_input() const override { return false; }
+
       void add_entropy(const uint8_t*, size_t) override
          {
          throw Botan::Exception("add_entropy() not supported by this RNG, test bug?");
@@ -147,6 +151,8 @@ class SeedCapturing_RNG final : public Botan::RandomNumberGenerator
          throw Botan::Exception("SeedCapturing_RNG has no output");
          }
 
+      bool accepts_input() const override { return true; }
+
       void add_entropy(const uint8_t input[], size_t len) override
          {
          m_samples++;
@@ -192,6 +198,8 @@ class Request_Counting_RNG final : public Botan::RandomNumberGenerator
          return m_randomize_count;
          }
 
+      bool accepts_input() const override { return false; }
+
       bool is_seeded() const override
          {
          return true;
diff --git a/src/tests/test_runner.cpp b/src/tests/test_runner.cpp
index f69f55c0d..8d3f9b72c 100644
--- a/src/tests/test_runner.cpp
+++ b/src/tests/test_runner.cpp
@@ -32,6 +32,8 @@ class Testsuite_RNG final : public Botan::RandomNumberGenerator
          m_a = m_b = m_c = m_d = 0;
          }
 
+      bool accepts_input() const override { return true; }
+
       void add_entropy(const uint8_t data[], size_t len) override
          {
          for(size_t i = 0; i != len; ++i)