libs: add ongoing work to facilitate hactool rewrite

libraries/libstratosphere/source/crypto/crypto_csrng.os.generic.cpp

@@ -0,0 +1,59 @@
+/*
+ * Copyright (c) Atmosphère-NX
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+#include <stratosphere.hpp>
+#include "../spl/impl/spl_ctr_drbg.hpp"
+#include <sys/random.h>
+
+namespace ams::crypto {
+
+    namespace {
+
+        using Drbg = ::ams::spl::impl::CtrDrbg<crypto::AesEncryptor128, crypto::AesEncryptor128::KeySize, false>;
+
+        constinit util::TypedStorage<Drbg> g_drbg = {};
+
+        bool InitializeCsrng() {
+            u8 seed[Drbg::SeedSize];
+            AMS_ABORT_UNLESS(::getentropy(seed, sizeof(seed)) == 0);
+
+            util::ConstructAt(g_drbg);
+            util::GetReference(g_drbg).Initialize(seed, sizeof(seed), nullptr, 0, nullptr, 0);
+
+            return true;
+        }
+
+    }
+
+    void GenerateCryptographicallyRandomBytes(void *dst, size_t dst_size) {
+        AMS_FUNCTION_LOCAL_STATIC(bool, s_initialized, InitializeCsrng());
+        AMS_ABORT_UNLESS(s_initialized);
+
+        AMS_ASSERT(dst_size <= Drbg::RequestSizeMax);
+
+        if (!util::GetReference(g_drbg).Generate(dst, dst_size, nullptr, 0)) {
+            /* Reseed, if needed. */
+            {
+                u8 seed[Drbg::SeedSize];
+                AMS_ABORT_UNLESS(::getentropy(seed, sizeof(seed)) == 0);
+
+                util::GetReference(g_drbg).Reseed(seed, sizeof(seed), nullptr, 0);
+            }
+
+            util::GetReference(g_drbg).Generate(dst, dst_size, nullptr, 0);
+        }
+    }
+
+}