From 8e1736c48032d6a4d884cc28be3b3b71a440f472 Mon Sep 17 00:00:00 2001
From: fincs <fincs.alt1@gmail.com>
Date: Wed, 17 Oct 2018 17:17:05 +0200
Subject: [PATCH] Add RandomSeed (14) homebrew ABI key and related handling

---
 nx/include/switch/runtime/env.h | 14 ++++++++++++--
 nx/source/kernel/random.c       | 11 +++++++++++
 nx/source/runtime/env.c         | 17 +++++++++++++++++
 3 files changed, 40 insertions(+), 2 deletions(-)

diff --git a/nx/include/switch/runtime/env.h b/nx/include/switch/runtime/env.h
index 8a409be6..ac311e17 100644
--- a/nx/include/switch/runtime/env.h
+++ b/nx/include/switch/runtime/env.h
@@ -30,9 +30,10 @@ enum {
     EntryType_SyscallAvailableHint=6, ///< Provides syscall availability hints.
     EntryType_AppletType=7,           ///< Provides APT applet type.
     EntryType_AppletWorkaround=8,     ///< Indicates that APT is broken and should not be used.
-    EntryType_StdioSockets=9,         ///< Provides socket-based standard stream redirection information.
+    EntryType_Reserved9=9,            ///< Unused/reserved entry type, formerly used by StdioSockets.
     EntryType_ProcessHandle=10,       ///< Provides the process handle.
-    EntryType_LastLoadResult=11       ///< Provides the last load result.
+    EntryType_LastLoadResult=11,      ///< Provides the last load result.
+    EntryType_RandomSeed=14,          ///< Provides random data used to seed the pseudo-random number generator.
 };
 
 enum {
@@ -95,3 +96,12 @@ bool envHasNextLoad(void);
 
 /// Returns the Result from the last NRO.
 Result envGetLastLoadResult(void);
+
+/// Returns true if the environment provides a random seed.
+bool envHasRandomSeed(void);
+
+/**
+ * @brief Retrieves the random seed provided by the environment.
+ * @param out Pointer to a u64[2] buffer which will contain the random seed on return.
+ */
+void envGetRandomSeed(u64 out[2]);
diff --git a/nx/source/kernel/random.c b/nx/source/kernel/random.c
index af8393c6..ba773178 100644
--- a/nx/source/kernel/random.c
+++ b/nx/source/kernel/random.c
@@ -13,6 +13,7 @@
 #include "kernel/mutex.h"
 #include "kernel/svc.h"
 #include "kernel/random.h"
+#include "runtime/env.h"
 
 #define ROTL32(x, n) (((x) << (n)) | ((x) >> (32-(n))))
 
@@ -139,6 +140,16 @@ static void _randomInit(void)
             fatalSimple(MAKERESULT(Module_Libnx, LibnxError_BadGetInfo_Rng));
     }
 
+    if (envHasRandomSeed())
+    {
+        u64 other_seed[2];
+        envGetRandomSeed(other_seed);
+        seed[0] ^= other_seed[1];
+        seed[1] ^= seed[0];
+        seed[2] ^= other_seed[0];
+        seed[3] ^= seed[2];
+    }
+
     u8 iv[8];
     memset(iv, 0, sizeof iv);
 
diff --git a/nx/source/runtime/env.c b/nx/source/runtime/env.c
index 0300beb9..7fe4fdfa 100644
--- a/nx/source/runtime/env.c
+++ b/nx/source/runtime/env.c
@@ -18,6 +18,8 @@ static Handle g_processHandle = INVALID_HANDLE;
 static char*  g_nextLoadPath = NULL;
 static char*  g_nextLoadArgv = NULL;
 static Result g_lastLoadResult = 0;
+static bool   g_hasRandomSeed = false;
+static u64    g_randomSeed[2] = { 0, 0 };
 
 extern __attribute__((weak)) u32 __nx_applet_type;
 
@@ -91,6 +93,12 @@ void envSetup(void* ctx, Handle main_thread, LoaderReturnFn saved_lr)
             g_lastLoadResult = ent->Value[0];
             break;
 
+        case EntryType_RandomSeed:
+            g_hasRandomSeed = true;
+            g_randomSeed[0] = ent->Value[0];
+            g_randomSeed[1] = ent->Value[1];
+            break;
+
         default:
             if (ent->Flags & EntryFlag_IsMandatory)
             {
@@ -179,3 +187,12 @@ bool envHasNextLoad(void) {
 Result envGetLastLoadResult(void) {
     return g_lastLoadResult;
 }
+
+bool envHasRandomSeed(void) {
+    return g_hasRandomSeed;
+}
+
+void envGetRandomSeed(u64 out[2]) {
+    out[0] = g_randomSeed[0];
+    out[1] = g_randomSeed[1];
+}