1 files changed, 58 insertions, 0 deletions
diff --git a/contrib/libottery/ottery_entropy_rdrand.c b/contrib/libottery/ottery_entropy_rdrand.c
new file mode 100644
index 0000000..4f227d3
--- /dev/null
+++ b/contrib/libottery/ottery_entropy_rdrand.c
@@ -0,0 +1,58 @@
+/* Libottery by Nick Mathewson.
+
+   This software has been dedicated to the public domain under the CC0
+   public domain dedication.
+
+   To the extent possible under law, the person who associated CC0 with
+   libottery has waived all copyright and related or neighboring rights
+   to libottery.
+
+   You should have received a copy of the CC0 legalcode along with this
+   work in doc/cc0.txt.  If not, see
+      <http://creativecommons.org/publicdomain/zero/1.0/>.
+ */
+
+#if defined(i386) || \
+    defined(__i386) || \
+    defined(__x86_64) || \
+    defined(__M_IX86) || \
+    defined(_M_IX86) || \
+    defined(__INTEL_COMPILER)
+
+extern int ottery_valgrind_;
+/** Helper: invoke the RDRAND instruction to get 4 random bytes in the output
+ * value. Return 1 on success, and 0 on failure. */
+#define rdrand32(x) ({ unsigned char err = 0; __asm volatile(".byte 0x0f; .byte 0xc7; .byte 0xf0; setc %1":"=a"(x), "=qm"(err) :"a"(0) :"cc"); err; })
+
+/** Generate bytes using the Intel RDRAND instruction. */
+static int
+ottery_get_entropy_rdrand(const struct ottery_entropy_config *cfg,
+                          struct ottery_entropy_state *state,
+                           uint8_t *out, size_t outlen)
+{
+  uint32_t up;
+  (void) cfg;
+  (void) state;
+  if (! (ottery_get_cpu_capabilities_() & OTTERY_CPUCAP_RAND) || ottery_valgrind_)
+    return OTTERY_ERR_INIT_STRONG_RNG;
+  while (outlen >= 4) {
+    if (rdrand32(up) != 1)
+      return OTTERY_ERR_INIT_STRONG_RNG;
+    memcpy (out, &up, sizeof (up));
+    out += sizeof (up);
+    outlen -= 4;
+  }
+
+  if (outlen) {
+    if (rdrand32(up) != 1)
+      return OTTERY_ERR_INIT_STRONG_RNG;
+    memcpy(out, &up, outlen);
+  }
+  return 0;
+}
+
+#define ENTROPY_SOURCE_RDRAND                                           \
+  { ottery_get_entropy_rdrand,  SRC(RDRAND)|DOM(CPU)|FL(FAST)|FL(STRONG) }
+
+#endif
+