Add back support for Windows Phone RNG, undeprecate UWP

See #1586. Reverts part of #1494

2 files changed, 49 insertions, 0 deletions

diff --git a/src/lib/rng/system_rng/info.txt b/src/lib/rng/system_rng/info.txt
index 4dc5be758..da4fce4e3 100644
--- a/src/lib/rng/system_rng/info.txt
+++ b/src/lib/rng/system_rng/info.txt
@@ -6,8 +6,13 @@ SYSTEM_RNG -> 20141202
 dev_random,posix1
 arc4random
 rtlgenrandom
+crypto_ng
 </os_features>
 
+<libs>
+uwp -> bcrypt.lib
+</libs>
+
 <requires>
 rtlgenrandom?dyn_load
 </requires>
diff --git a/src/lib/rng/system_rng/system_rng.cpp b/src/lib/rng/system_rng/system_rng.cpp
index 3c2e98661..c3b37ea9c 100644
--- a/src/lib/rng/system_rng/system_rng.cpp
+++ b/src/lib/rng/system_rng/system_rng.cpp
@@ -13,6 +13,9 @@
   #define _WINSOCKAPI_ // stop windows.h including winsock.h
   #include <windows.h>
 
+#elif defined(BOTAN_TARGET_OS_HAS_CRYPTO_NG)
+   #include <bcrypt.h>
+
 #elif defined(BOTAN_TARGET_OS_HAS_ARC4RANDOM)
    #include <stdlib.h>
 
@@ -60,6 +63,47 @@ class System_RNG_Impl final : public RandomNumberGenerator
       RtlGenRandom_fptr m_rtlgenrandom;
    };
 
+#elif defined(BOTAN_TARGET_OS_HAS_CRYPTO_NG)
+
+class System_RNG_Impl final : public RandomNumberGenerator
+   {
+   public:
+      System_RNG_Impl()
+         {
+         NTSTATUS ret = ::BCryptOpenAlgorithmProvider(&m_prov,
+                                                      BCRYPT_RNG_ALGORITHM,
+                                                      MS_PRIMITIVE_PROVIDER, 0);
+         if(ret != STATUS_SUCCESS)
+            throw Exception("System_RNG failed to acquire crypto provider");
+         }
+
+      ~System_RNG_Impl()
+         {
+         ::BCryptCloseAlgorithmProvider(m_prov, 0);
+         }
+
+      void randomize(uint8_t buf[], size_t len) override
+         {
+         NTSTATUS ret = ::BCryptGenRandom(m_prov, static_cast<PUCHAR>(buf), static_cast<ULONG>(len), 0);
+         if(ret != STATUS_SUCCESS)
+            throw Exception("System_RNG call to BCryptGenRandom failed");
+         }
+
+      void add_entropy(const uint8_t in[], size_t length) override
+         {
+         /*
+         There is a flag BCRYPT_RNG_USE_ENTROPY_IN_BUFFER to provide
+         entropy inputs, but it is ignored in Windows 8 and later.
+         */
+         }
+
+      bool is_seeded() const override { return true; }
+      void clear() override { /* not possible */ }
+      std::string name() const override { return "crypto_ng"; }
+   private:
+      BCRYPT_ALG_HANDLE m_handle;
+   };
+
 #elif defined(BOTAN_TARGET_OS_HAS_ARC4RANDOM)
 
 class System_RNG_Impl final : public RandomNumberGenerator