1 files changed, 118 insertions, 0 deletions
diff --git a/src/lib/rng/stateful_rng/stateful_rng.h b/src/lib/rng/stateful_rng/stateful_rng.h
new file mode 100644
index 000000000..11f0c7e3d
--- /dev/null
+++ b/src/lib/rng/stateful_rng/stateful_rng.h
@@ -0,0 +1,118 @@
+/*
+* (C) 2016 Jack Lloyd
+*
+* Botan is released under the Simplified BSD License (see license.txt)
+*/
+
+#ifndef BOTAN_STATEFUL_RNG_H__
+#define BOTAN_STATEFUL_RNG_H__
+
+#include <botan/rng.h>
+
+namespace Botan {
+
+/**
+* Inherited by RNGs which maintain in-process state, like HMAC_DRBG.
+* On Unix these RNGs are vulnerable to problems with fork, where the
+* RNG state is duplicated, and the parent and child process RNGs will
+* produce identical output until one of them reseeds. Stateful_RNG
+* reseeds itself whenever a fork is detected, or after a set number of
+* bytes have been output.
+*
+* Not implemented by RNGs which access an external RNG, such as the
+* system PRNG or a hardware RNG.
+*/
+class BOTAN_DLL Stateful_RNG : public RandomNumberGenerator
+   {
+   public:
+      Stateful_RNG(RandomNumberGenerator& rng,
+                   Entropy_Sources& entropy_sources,
+                   size_t reseed_interval) :
+         m_underlying_rng(&rng),
+         m_entropy_sources(&entropy_sources),
+         m_reseed_interval(reseed_interval)
+         {}
+
+      Stateful_RNG(RandomNumberGenerator& rng, size_t reseed_interval) :
+         m_underlying_rng(&rng),
+         m_reseed_interval(reseed_interval)
+         {}
+
+      Stateful_RNG(Entropy_Sources& entropy_sources, size_t reseed_interval) :
+         m_entropy_sources(&entropy_sources),
+         m_reseed_interval(reseed_interval)
+         {}
+
+      /**
+      * In this case, automatic reseeding is impossible
+      */
+      Stateful_RNG() : m_reseed_interval(0) {}
+
+      /**
+      * Consume this input and mark the RNG as initialized regardless
+      * of the length of the input or the current seeded state of
+      * the RNG.
+      */
+      void initialize_with(const byte input[], size_t length);
+
+      bool is_seeded() const override final;
+
+      /**
+      * Mark state as requiring a reseed on next use
+      */
+      void force_reseed();
+
+      void reseed_from_rng(RandomNumberGenerator& rng,
+                           size_t poll_bits = BOTAN_RNG_RESEED_POLL_BITS) override final;
+
+      /**
+      * Overrides default implementation and also includes the current
+      * process ID and the reseed counter.
+      */
+      void randomize_with_ts_input(byte output[], size_t output_len) override final;
+
+      /**
+      * Poll provided sources for up to poll_bits bits of entropy
+      * or until the timeout expires. Returns estimate of the number
+      * of bits collected.
+      */
+      size_t reseed(Entropy_Sources& srcs,
+                    size_t poll_bits = BOTAN_RNG_RESEED_POLL_BITS,
+                    std::chrono::milliseconds poll_timeout = BOTAN_RNG_RESEED_DEFAULT_TIMEOUT) override;
+
+      /**
+      * Return intended security level of this DRBG
+      */
+      virtual size_t security_level() const = 0;
+
+      void clear() override;
+
+   protected:
+      /**
+      * Called with lock held
+      */
+      void reseed_check();
+
+      uint32_t last_pid() const { return m_last_pid; }
+
+   private:
+      // A non-owned and possibly null pointer to shared RNG
+      RandomNumberGenerator* m_underlying_rng = nullptr;
+
+      // A non-owned and possibly null pointer to a shared Entropy_Source
+      Entropy_Sources* m_entropy_sources = nullptr;
+
+      const size_t m_reseed_interval;
+
+      /*
+      * Set to 1 after a sucessful seeding, then incremented.  Reset
+      * to 0 by clear() or a fork. This logic is used even if
+      * automatic reseeding is disabled (via m_reseed_interval = 0)
+      */
+      size_t m_reseed_counter = 0;
+      uint32_t m_last_pid = 0;
+   };
+
+}
+
+#endif