Use rdrand as entropy source on supported platforms

sipa · Warrows · commit b8bbb9c68d99 · 2019-07-31T11:52:16.000+02:00
diff --git a/src/init.cpp b/src/init.cpp
@@ -1026,6 +1026,7 @@ bool AppInit2()
     // ********************************************************* Step 4: application initialization: dir lock, daemonize, pidfile, debug log
 
     // Initialize elliptic curve code
+    RandomInit();
     ECC_Start();
     globalVerifyHandle.reset(new ECCVerifyHandle());
 
diff --git a/src/random.cpp b/src/random.cpp
@@ -65,6 +65,64 @@ static inline int64_t GetPerformanceCounter()
 #endif
 }
 
+
+#if defined(__x86_64__) || defined(__amd64__) || defined(__i386__)
+static std::atomic<bool> hwrand_initialized{false};
+static bool rdrand_supported = false;
+static constexpr uint32_t CPUID_F1_ECX_RDRAND = 0x40000000;
+static void RDRandInit()
+{
+    //! When calling cpuid function #1, ecx register will have this set if RDRAND is available.
+    // Avoid clobbering ebx, as that is used for PIC on x86.
+    uint32_t eax, tmp, ecx, edx;
+    __asm__ ("mov %%ebx, %1; cpuid; mov %1, %%ebx": "=a"(eax), "=g"(tmp), "=c"(ecx), "=d"(edx) : "a"(1));
+    if (ecx & CPUID_F1_ECX_RDRAND) {
+        LogPrintf("Using RdRand as entropy source\n");
+        rdrand_supported = true;
+    }
+    hwrand_initialized.store(true);
+}
+#else
+static void RDRandInit() {}
+#endif
+
+static bool GetHWRand(unsigned char* ent32) {
+#if defined(__x86_64__) || defined(__amd64__) || defined(__i386__)
+    assert(hwrand_initialized.load(std::memory_order_relaxed));
+    if (rdrand_supported) {
+        uint8_t ok;
+        // Not all assemblers support the rdrand instruction, write it in hex.
+#ifdef __i386__
+        for (int iter = 0; iter < 4; ++iter) {
+            uint32_t r1, r2;
+            __asm__ volatile (".byte 0x0f, 0xc7, 0xf0;" // rdrand %eax
+                              ".byte 0x0f, 0xc7, 0xf2;" // rdrand %edx
+                              "setc %2" :
+                              "=a"(r1), "=d"(r2), "=q"(ok) :: "cc");
+            if (!ok) return false;
+            WriteLE32(ent32 + 8 * iter, r1);
+            WriteLE32(ent32 + 8 * iter + 4, r2);
+        }
+#else
+        uint64_t r1, r2, r3, r4;
+        __asm__ volatile (".byte 0x48, 0x0f, 0xc7, 0xf0, " // rdrand %rax
+                                "0x48, 0x0f, 0xc7, 0xf3, " // rdrand %rbx
+                                "0x48, 0x0f, 0xc7, 0xf1, " // rdrand %rcx
+                                "0x48, 0x0f, 0xc7, 0xf2; " // rdrand %rdx
+                          "setc %4" :
+                          "=a"(r1), "=b"(r2), "=c"(r3), "=d"(r4), "=q"(ok) :: "cc");
+        if (!ok) return false;
+        WriteLE64(ent32, r1);
+        WriteLE64(ent32 + 8, r2);
+        WriteLE64(ent32 + 16, r3);
+        WriteLE64(ent32 + 24, r4);
+#endif
+        return true;
+    }
+#endif
+    return false;
+}
+
 void RandAddSeed()
 {
     // Seed with CPU performance counter
@@ -257,6 +315,11 @@ void GetStrongRandBytes(unsigned char* out, int num)
     GetOSRand(buf);
     hasher.Write(buf, 32);
 
+    // Third source: HW RNG, if available.
+    if (GetHWRand(buf)) {
+        hasher.Write(buf, 32);
+    }
+
     // Combine with and update state
     {
         std::unique_lock<std::mutex> lock(cs_rng_state);
@@ -383,3 +446,8 @@ FastRandomContext::FastRandomContext(bool fDeterministic) : requires_seed(!fDete
     uint256 seed;
     rng.SetKey(seed.begin(), 32);
 }
+
+void RandomInit()
+{
+    RDRandInit();
+}
diff --git a/src/random.h b/src/random.h
@@ -140,4 +140,7 @@ void GetOSRand(unsigned char *ent32);
  */
 bool Random_SanityCheck();
 
+/** Initialize the RNG. */
+void RandomInit();
+
 #endif // BITCOIN_RANDOM_H
diff --git a/src/test/test_pivx.cpp b/src/test/test_pivx.cpp
@@ -30,6 +30,7 @@ extern void noui_connect();
 
 BasicTestingSetup::BasicTestingSetup()
 {
+        RandomInit();
         ECC_Start();
         SetupEnvironment();
         fPrintToDebugLog = false; // don't want to write to debug.log file

Original file line number	Diff line number	Diff line change
`@@ -30,6 +30,7 @@ extern void noui_connect();`
`30`	`30`
`31`	`31`	`BasicTestingSetup::BasicTestingSetup()`
`32`	`32`	`{`
	`33`	`+ RandomInit();`
`33`	`34`	`ECC_Start();`
`34`	`35`	`SetupEnvironment();`
`35`	`36`	`fPrintToDebugLog = false; // don't want to write to debug.log file`