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, 8 insertions, 2 deletions

diff --git a/src/lib/rng/hmac_drbg/hmac_drbg.cpp b/src/lib/rng/hmac_drbg/hmac_drbg.cpp
index ad731b6b3..67325ee1b 100644
--- a/src/lib/rng/hmac_drbg/hmac_drbg.cpp
+++ b/src/lib/rng/hmac_drbg/hmac_drbg.cpp
@@ -78,11 +78,13 @@ void HMAC_DRBG::update(const byte input[], size_t input_len)
       }
    }
 
-void HMAC_DRBG::reseed(size_t poll_bits)
+size_t HMAC_DRBG::reseed_with_sources(Entropy_Sources& srcs,
+                                      size_t poll_bits,
+                                      std::chrono::milliseconds poll_timeout)
    {
    if(m_prng)
       {
-      m_prng->reseed(poll_bits);
+      size_t bits = m_prng->reseed_with_sources(srcs, poll_bits, poll_timeout);
 
       if(m_prng->is_seeded())
          {
@@ -90,7 +92,11 @@ void HMAC_DRBG::reseed(size_t poll_bits)
          update(input.data(), input.size());
          m_reseed_counter = 1;
          }
+
+      return bits;
       }
+
+   return 0;
    }
 
 void HMAC_DRBG::add_entropy(const byte input[], size_t length)