Add support for Fuchsia in crypto/rand.

This change adds the OS-specific routines to get random bytes when using
BoringSSL on Fuchsia.  Fuchsia uses the Magenta kernel, which provides
random bytes via a syscall rather than via a file or library function.

Change-Id: I32f858246425309d643d142214c7b8de0c62250a
Reviewed-on: https://boringssl-review.googlesource.com/13140
Reviewed-by: David Benjamin <davidben@google.com>
Commit-Queue: David Benjamin <davidben@google.com>
CQ-Verified: CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org>

crypto/rand/CMakeLists.txt

@@ -14,6 +14,7 @@ add_library(
   OBJECT
 
   deterministic.c
+  fuchsia.c
   rand.c
   urandom.c
   windows.c

crypto/rand/fuchsia.c

@@ -0,0 +1,43 @@
+/* Copyright (c) 2017, Google Inc.
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
+ * SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
+ * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
+ * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */
+
+#include <openssl/rand.h>
+
+#if defined(OPENSSL_FUCHSIA) && !defined(BORINGSSL_UNSAFE_DETERMINISTIC_MODE)
+
+#include <limits.h>
+#include <stdlib.h>
+
+#include <magenta/syscalls.h>
+
+#include "internal.h"
+
+void CRYPTO_sysrand(uint8_t *out, size_t requested) {
+  while (requested > 0) {
+    size_t output_bytes_this_pass = MX_CPRNG_DRAW_MAX_LEN;
+    if (requested < output_bytes_this_pass) {
+      output_bytes_this_pass = requested;
+    }
+    size_t bytes_drawn;
+    mx_status_t status =
+        mx_cprng_draw(out, output_bytes_this_pass, &bytes_drawn);
+    if (status != NO_ERROR) {
+      abort();
+    }
+    requested -= bytes_drawn;
+    out += bytes_drawn;
+  }
+}
+
+#endif /* OPENSSL_FUCHSIA && !BORINGSSL_UNSAFE_DETERMINISTIC_MODE */

include/openssl/base.h

@@ -118,6 +118,10 @@ extern "C" {
 #define OPENSSL_LINUX
 #endif
 
+#if defined(__Fuchsia__)
+#define OPENSSL_FUCHSIA
+#endif
+
 #if defined(TRUSTY)
 #define OPENSSL_TRUSTY
 #define OPENSSL_NO_THREADS