New reseed_with_sources call on RNGs

Provides an easier way for an application to configure a list of
entropy sources they'd like to use, or add a custom entropy source to
their seeding.

Exposes some toggles for the global/default entropy sources to build.h

Adds basic entropy tests which runs the polls and does sanity checking
on the results, including compression tests if available. These are
less useful for the CSPRNG outputs but a good check for the ones
producing plain ASCII like the /proc reader.

1 files changed, 34 insertions, 6 deletions

diff --git a/src/lib/rng/rng.h b/src/lib/rng/rng.h
index a28a676a6..1ce0d5153 100644
--- a/src/lib/rng/rng.h
+++ b/src/lib/rng/rng.h
@@ -8,13 +8,16 @@
 #ifndef BOTAN_RANDOM_NUMBER_GENERATOR_H__
 #define BOTAN_RANDOM_NUMBER_GENERATOR_H__
 
-#include <botan/entropy_src.h>
+#include <botan/secmem.h>
 #include <botan/exceptn.h>
+#include <chrono>
 #include <string>
 #include <mutex>
 
 namespace Botan {
 
+class Entropy_Sources;
+
 /**
 * This class represents a random number (RNG) generator object.
 */
@@ -100,11 +103,29 @@ class BOTAN_DLL RandomNumberGenerator
       virtual std::string name() const = 0;
 
       /**
-      * Seed this RNG using the entropy sources it contains.
+      * Seed this RNG using the global entropy sources and default timeout
+      * @param bits_to_collect is the number of bits of entropy to
+               attempt to gather from the entropy sources
+      */
+      size_t reseed(size_t bits_to_collect);
+
+      /**
+      * Seed this RNG using the global entropy sources
       * @param bits_to_collect is the number of bits of entropy to
                attempt to gather from the entropy sources
+      * @param poll_timeout try not to run longer than this, no matter what
       */
-      virtual void reseed(size_t bits_to_collect) = 0;
+      size_t reseed_with_timeout(size_t bits_to_collect,
+                                 std::chrono::milliseconds poll_timeout);
+
+      /**
+      * Poll provided sources for up to poll_bits bits of entropy
+      * or until the timeout expires. Returns estimate of the number
+      * of bits collected.
+      */
+      virtual size_t reseed_with_sources(Entropy_Sources& srcs,
+                                         size_t poll_bits,
+                                         std::chrono::milliseconds poll_timeout) = 0;
 
       /**
       * Add entropy to this RNG.
@@ -135,7 +156,12 @@ class BOTAN_DLL Null_RNG : public RandomNumberGenerator
 
       std::string name() const override { return "Null_RNG"; }
 
-      void reseed(size_t) override {}
+      size_t reseed_with_sources(Entropy_Sources&, size_t,
+                                 std::chrono::milliseconds) override
+         {
+         return 0;
+         }
+
       bool is_seeded() const override { return false; }
       void add_entropy(const byte[], size_t) override {}
    };
@@ -170,10 +196,12 @@ class BOTAN_DLL Serialized_RNG : public RandomNumberGenerator
          return m_rng->name();
          }
 
-      void reseed(size_t poll_bits) override
+      size_t reseed_with_sources(Entropy_Sources& src,
+                                 size_t bits,
+                                 std::chrono::milliseconds msec) override
          {
          std::lock_guard<std::mutex> lock(m_mutex);
-         m_rng->reseed(poll_bits);
+         return m_rng->reseed_with_sources(src, bits, msec);
          }
 
       void add_entropy(const byte in[], size_t len) override