From ab552e4a252b66ca02c04724a1773edbefec6837 Mon Sep 17 00:00:00 2001
From: Zach Hilman <zachhilman@gmail.com>
Date: Tue, 13 Nov 2018 12:25:43 -0500
Subject: svc: Use proper random entropy generation algorithm

---
 src/core/hle/kernel/process.cpp |  6 ++++++
 src/core/hle/kernel/process.h   | 11 +++++++++++
 src/core/hle/kernel/svc.cpp     | 11 ++++++++++-
 src/core/settings.h             |  2 +-
 4 files changed, 28 insertions(+), 2 deletions(-)

(limited to 'src/core')

diff --git a/src/core/hle/kernel/process.cpp b/src/core/hle/kernel/process.cpp
index 420218d59..6e5b36d6f 100644
--- a/src/core/hle/kernel/process.cpp
+++ b/src/core/hle/kernel/process.cpp
@@ -17,6 +17,7 @@
 #include "core/hle/kernel/thread.h"
 #include "core/hle/kernel/vm_manager.h"
 #include "core/memory.h"
+#include "core/settings.h"
 
 namespace Kernel {
 
@@ -35,6 +36,11 @@ SharedPtr<Process> Process::Create(KernelCore& kernel, std::string&& name) {
     process->process_id = kernel.CreateNewProcessID();
     process->svc_access_mask.set();
 
+    std::mt19937 rng(Settings::values.rng_seed.value_or(0));
+    std::uniform_int_distribution<u64> distribution;
+    std::generate(process->random_entropy.begin(), process->random_entropy.end(),
+                  [&] { return distribution(rng); });
+
     kernel.AppendNewProcess(process);
     return process;
 }
diff --git a/src/core/hle/kernel/process.h b/src/core/hle/kernel/process.h
index 8d2616c79..95aa63ea1 100644
--- a/src/core/hle/kernel/process.h
+++ b/src/core/hle/kernel/process.h
@@ -8,6 +8,7 @@
 #include <bitset>
 #include <cstddef>
 #include <memory>
+#include <random>
 #include <string>
 #include <vector>
 #include <boost/container/static_vector.hpp>
@@ -119,6 +120,8 @@ struct CodeSet final {
 
 class Process final : public Object {
 public:
+    static constexpr std::size_t RANDOM_ENTROPY_SIZE = 4;
+
     static SharedPtr<Process> Create(KernelCore& kernel, std::string&& name);
 
     std::string GetTypeName() const override {
@@ -212,6 +215,11 @@ public:
         total_process_running_time_ticks += ticks;
     }
 
+    /// Gets 8 bytes of random data for svcGetInfo RandomEntropy
+    u64 GetRandomEntropy(std::size_t index) const {
+        return random_entropy.at(index);
+    }
+
     /**
      * Loads process-specifics configuration info with metadata provided
      * by an executable.
@@ -321,6 +329,9 @@ private:
     /// Per-process handle table for storing created object handles in.
     HandleTable handle_table;
 
+    /// Random values for svcGetInfo RandomEntropy
+    std::array<u64, RANDOM_ENTROPY_SIZE> random_entropy;
+
     std::string name;
 };
 
diff --git a/src/core/hle/kernel/svc.cpp b/src/core/hle/kernel/svc.cpp
index 0bfe1e3be..b0b6508d9 100644
--- a/src/core/hle/kernel/svc.cpp
+++ b/src/core/hle/kernel/svc.cpp
@@ -559,7 +559,16 @@ static ResultCode GetInfo(u64* result, u64 info_id, u64 handle, u64 info_sub_id)
         *result = 0;
         break;
     case GetInfoType::RandomEntropy:
-        *result = Settings::values.rng_seed.value_or(0);
+        if (handle != 0) {
+            return ERR_INVALID_HANDLE;
+        }
+
+        if (info_sub_id >= Process::RANDOM_ENTROPY_SIZE) {
+            return ERR_INVALID_COMBINATION_KERNEL;
+        }
+
+        *result = current_process->GetRandomEntropy(info_sub_id);
+        return RESULT_SUCCESS;
         break;
     case GetInfoType::ASLRRegionBaseAddr:
         *result = vm_manager.GetASLRRegionBaseAddress();
diff --git a/src/core/settings.h b/src/core/settings.h
index 83a1a7069..84dc5050b 100644
--- a/src/core/settings.h
+++ b/src/core/settings.h
@@ -115,7 +115,7 @@ struct Values {
     // System
     bool use_docked_mode;
     bool enable_nfc;
-    std::optional<u64> rng_seed;
+    std::optional<u32> rng_seed;
     s32 current_user;
     s32 language_index;
 
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