Merge pull request #6565 from WinterSolstice8/rng_updates

RNG seeding updates, update default RNG to MT64
LandSandBoat · Dec 21, 2024 · e41fa00 · e41fa00
2 parents de2f341 + e54188e
commit e41fa00
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Showing 7 changed files with 105 additions and 72 deletions.
diff --git a/src/common/CMakeLists.txt b/src/common/CMakeLists.txt
@@ -37,6 +37,7 @@ set(COMMON_SOURCES
     ${CMAKE_CURRENT_SOURCE_DIR}/timer.cpp
     ${CMAKE_CURRENT_SOURCE_DIR}/timer.h
     ${CMAKE_CURRENT_SOURCE_DIR}/xirand.h
+    ${CMAKE_CURRENT_SOURCE_DIR}/xirand.cpp
     ${CMAKE_CURRENT_SOURCE_DIR}/utils.cpp
     ${CMAKE_CURRENT_SOURCE_DIR}/utils.h
     ${CMAKE_CURRENT_SOURCE_DIR}/uuid.h

diff --git a/src/common/rng/mersennetwister.h b/src/common/rng/mersennetwister.h
@@ -25,6 +25,9 @@
 #include <array>
 #include <random>
 
+// Forward declare sysrandom which is built in the xirand.h/cpp compilation unit
+extern size_t sysrandom(void* dst, size_t dstlen);
+
 class xirand
 {
 public:
@@ -38,27 +41,10 @@ class xirand
     {
         ShowInfo("Seeding Mersenne Twister 32 bit RNG");
 
-        std::array<uint32_t, std::mt19937::state_size> seed_data;
-
-        // Certain systems were noted to have bad seeding via only std::random_device,
-        // the following indicated how we could mix in std::random_device with other seed sources
-        // https://stackoverflow.com/a/68382489
-        for (auto it = seed_data.begin(); it != seed_data.end(); ++it)
-        {
-            // start with a C++ equivalent of time(nullptr) - UNIX time in seconds
-            *it = std::chrono::duration_cast<std::chrono::seconds>(
-                      std::chrono::system_clock::now().time_since_epoch())
-                      .count();
-
-            // mix with a high precision time in microseconds
-            *it ^= std::chrono::duration_cast<std::chrono::microseconds>(
-                       std::chrono::high_resolution_clock::now().time_since_epoch())
-                       .count();
-
-            // *it ^= more_external_random_stuff;
-        }
-        std::seed_seq seq(seed_data.cbegin(), seed_data.cend());
-        rng().seed(seq);
+        uint32_t seed;
+        sysrandom(&seed, sizeof(seed));
+
+        rng().seed(seed);
     }
 
     /*

diff --git a/src/common/rng/mersennetwister64.h b/src/common/rng/mersennetwister64.h
@@ -25,6 +25,9 @@
 #include <array>
 #include <random>
 
+// Forward declare sysrandom which is built in the xirand.h/cpp compilation unit
+extern size_t sysrandom(void* dst, size_t dstlen);
+
 class xirand
 {
 public:
@@ -38,27 +41,10 @@ class xirand
     {
         ShowInfo("Seeding Mersenne Twister 64 bit RNG");
 
-        std::array<uint64_t, std::mt19937_64::state_size> seed_data;
-
-        // Certain systems were noted to have bad seeding via only std::random_device,
-        // the following indicated how we could mix in std::random_device with other seed sources
-        // https://stackoverflow.com/a/68382489
-        for (auto it = seed_data.begin(); it != seed_data.end(); ++it)
-        {
-            // start with a C++ equivalent of time(nullptr) - UNIX time in seconds
-            *it = std::chrono::duration_cast<std::chrono::seconds>(
-                      std::chrono::system_clock::now().time_since_epoch())
-                      .count();
-
-            // mix with a high precision time in microseconds
-            *it ^= std::chrono::duration_cast<std::chrono::microseconds>(
-                       std::chrono::high_resolution_clock::now().time_since_epoch())
-                       .count();
-
-            // *it ^= more_external_random_stuff;
-        }
-        std::seed_seq seq(seed_data.cbegin(), seed_data.cend());
-        rng().seed(seq);
+        uint64_t seed;
+        sysrandom(&seed, sizeof(seed));
+
+        rng().seed(seed);
     }
 
     /*

diff --git a/src/common/rng/pcg.h b/src/common/rng/pcg.h
@@ -28,6 +28,9 @@
 #include <array>
 #include <random>
 
+// Forward declare sysrandom which is built in the xirand.h/cpp compilation unit
+extern size_t sysrandom(void* dst, size_t dstlen);
+
 class xirand
 {
 public:
@@ -41,25 +44,17 @@ class xirand
     {
         ShowInfo("Seeding PCG32 RNG");
 
-        std::array<uint32_t, sizeof(pcg32::state_type) / 4> seed_data; // get enough data to seed an N byte state with sets of 32 bit ints
+        std::array<pcg32::state_type, 2> seed_data; // PCG states seem to be bit size * 2 * 2, here 64 bit numbers * 2
+
+        pcg32::state_type seed;
 
-        // Certain systems were noted to have bad seeding via only std::random_device,
-        // the following indicated how we could mix in std::random_device with other seed sources
-        // https://stackoverflow.com/a/68382489
         for (auto it = seed_data.begin(); it != seed_data.end(); ++it)
         {
-            // start with a C++ equivalent of time(nullptr) - UNIX time in seconds
-            *it = std::chrono::duration_cast<std::chrono::seconds>(
-                      std::chrono::system_clock::now().time_since_epoch())
-                      .count();
+            sysrandom(&seed, sizeof(seed));
 
-            // mix with a high precision time in microseconds
-            *it ^= std::chrono::duration_cast<std::chrono::microseconds>(
-                       std::chrono::high_resolution_clock::now().time_since_epoch())
-                       .count();
-
-            // *it ^= more_external_random_stuff;
+            *it = seed;
         }
+
         std::seed_seq seq(seed_data.cbegin(), seed_data.cend());
         rng().seed(seq);
     }

diff --git a/src/common/rng/pcg64.h b/src/common/rng/pcg64.h
@@ -28,6 +28,9 @@
 #include <array>
 #include <random>
 
+// Forward declare sysrandom which is built in the xirand.h/cpp compilation unit
+extern size_t sysrandom(void* dst, size_t dstlen);
+
 class xirand
 {
 public:
@@ -41,25 +44,17 @@ class xirand
     {
         ShowInfo("Seeding PCG64 RNG");
 
-        std::array<uint32_t, sizeof(pcg64::state_type) / 4> seed_data; // get enough data to seed an N byte state with sets of 32 bit ints
+        std::array<pcg64::state_type, 2> seed_data;
+
+        pcg64::state_type seed;
 
-        // Certain systems were noted to have bad seeding via only std::random_device,
-        // the following indicated how we could mix in std::random_device with other seed sources
-        // https://stackoverflow.com/a/68382489
         for (auto it = seed_data.begin(); it != seed_data.end(); ++it)
         {
-            // start with a C++ equivalent of time(nullptr) - UNIX time in seconds
-            *it = std::chrono::duration_cast<std::chrono::seconds>(
-                      std::chrono::system_clock::now().time_since_epoch())
-                      .count();
+            sysrandom(&seed, sizeof(seed));
 
-            // mix with a high precision time in microseconds
-            *it ^= std::chrono::duration_cast<std::chrono::microseconds>(
-                       std::chrono::high_resolution_clock::now().time_since_epoch())
-                       .count();
-
-            // *it ^= more_external_random_stuff;
+            *it = seed;
         }
+
         std::seed_seq seq(seed_data.cbegin(), seed_data.cend());
         rng().seed(seq);
     }

diff --git a/src/common/xirand.cpp b/src/common/xirand.cpp
@@ -0,0 +1,67 @@
+#include <fstream>
+#include <stddef.h>
+
+// https://stackoverflow.com/a/45069417
+#ifdef _WIN32
+
+#include <windows.h>
+
+#include <wincrypt.h>
+
+bool acquire_context(HCRYPTPROV* ctx)
+{
+    if (!CryptAcquireContext(ctx, nullptr, nullptr, PROV_RSA_FULL, 0))
+    {
+        return CryptAcquireContext(ctx, nullptr, nullptr, PROV_RSA_FULL, CRYPT_NEWKEYSET);
+    }
+
+    return true;
+}
+
+size_t sysrandom(void* dst, size_t dstlen)
+{
+    HCRYPTPROV ctx;
+    if (!acquire_context(&ctx))
+    {
+        throw std::runtime_error("Unable to initialize Win32 crypt library.");
+    }
+
+    BYTE* buffer = reinterpret_cast<BYTE*>(dst);
+    if (!CryptGenRandom(ctx, static_cast<DWORD>(dstlen), buffer))
+    {
+        throw std::runtime_error("Unable to generate random bytes.");
+    }
+
+    if (!CryptReleaseContext(ctx, 0))
+    {
+        throw std::runtime_error("Unable to release Win32 crypt library.");
+    }
+
+    return dstlen;
+}
+#elif defined(__linux__) || defined(linux) || defined(__linux)
+
+#include <linux/random.h>
+#include <sys/syscall.h>
+#include <unistd.h>
+
+size_t sysrandom(void* dst, size_t dstlen)
+{
+    int bytes = syscall(SYS_getrandom, dst, dstlen, 0);
+    if (bytes != dstlen)
+    {
+        throw std::runtime_error("Unable to read N bytes from CSPRNG.");
+    }
+
+    return dstlen;
+}
+#else // OSX
+size_t sysrandom(void* dst, size_t dstlen)
+{
+    char*         buffer = reinterpret_cast<char*>(dst);
+    std::ifstream stream("/dev/urandom", std::ios_base::binary | std::ios_base::in);
+    stream.read(buffer, dstlen);
+
+    return dstlen;
+}
+#endif
diff --git a/src/common/xirand.h b/src/common/xirand.h
@@ -24,8 +24,8 @@
 #define _XIRAND_H_
 
 // You can choose an RNG by commenting/uncommenting this line. The default is Mersenne Twister in 32 bit.
-#include "rng/mersennetwister.h"
-// #include "rng/mersennetwister64.h"
+// #include "rng/mersennetwister.h"
+#include "rng/mersennetwister64.h"
 // #include "rng/pcg.h"
 // #include "rng/pcg64.h"
 
@@ -138,4 +138,7 @@ inline T xirand::GetRandomElement(std::initializer_list<T> list)
     return GetRandomElement(container);
 }
 
+// Get secure random numbers
+size_t sysrandom(void* dst, size_t dstlen);
+
 #endif // _XIRAND_H_