Implement CSRNG services

nx/include/switch.h

@@ -41,6 +41,7 @@ extern "C" {
 #include "switch/services/applet.h"
 #include "switch/services/audin.h"
 #include "switch/services/audout.h"
+#include "switch/services/csrng.h"
 //#include "switch/services/bsd.h" Use switch/runtime/devices/socket.h instead
 #include "switch/services/fatal.h"
 #include "switch/services/time.h"

nx/include/switch/services/csrng.h

@@ -0,0 +1,13 @@
+/**
+ * @file csrng.h
+ * @brief Cryptographically-Secure Random Number Generation (csrng) service IPC wrapper.
+ * @author SciresM
+ * @copyright libnx Authors
+ */
+#pragma once
+#include "../types.h"
+
+Result csrngInitialize(void);
+void csrngExit(void);
+
+Result csrngGetRandomBytes(void *out, size_t out_size);

nx/source/services/csrng.c

@@ -0,0 +1,59 @@
+// Copyright 2018 SciresM
+#include <string.h>
+#include "types.h"
+#include "result.h"
+#include "arm/atomics.h"
+#include "kernel/ipc.h"
+#include "kernel/detect.h"
+#include "services/sm.h"
+#include "services/spl.h"
+
+static Service g_csrngSrv;
+static u64 g_csrngRefCnt;
+
+Result csrngInitialize(void) {
+    atomicIncrement64(&g_csrngRefCnt);
+    
+    if (serviceIsActive(&g_csrngSrv))
+        return 0;
+    
+    return smGetService(&g_csrngSrv, "csrng");
+}
+
+void csrngExit(void) {
+    if (atomicDecrement64(&g_csrngRefCnt) == 0)
+        serviceClose(&g_csrngSrv);
+}
+
+Result csrngGetRandomBytes(void *out, size_t out_size) {
+    IpcCommand c;
+    ipcInitialize(&c);
+    
+    ipcAddRecvBuffer(&c, out, out_size, BufferType_Normal);
+
+    struct {
+        u64 magic;
+        u64 cmd_id;
+    } *raw;
+
+    raw = ipcPrepareHeader(&c, sizeof(*raw));
+
+    raw->magic = SFCI_MAGIC;
+    raw->cmd_id = 0;
+
+    Result rc = serviceIpcDispatch(&g_csrngSrv);
+
+    if (R_SUCCEEDED(rc)) {
+        IpcParsedCommand r;
+        ipcParse(&r);
+
+        struct {
+            u64 magic;
+            u64 result;
+        } *resp = r.Raw;
+
+        rc = resp->result;
+    }
+
+    return rc;
+}