unix,win: add uv_random()

Add an API for obtaining cryptographically strong random data from the
system PRNG.

Co-authored-by: Saúl Ibarra Corretgé <s@saghul.net>
Refs: https://github.com/libuv/libuv/pull/1055
PR-URL: https://github.com/libuv/libuv/pull/2347
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Santiago Gimeno <santiago.gimeno@gmail.com>

1 files changed, 88 insertions, 0 deletions

diff --git a/src/unix/random-getrandom.c b/src/unix/random-getrandom.c
new file mode 100644
index 00000000..bcc94089
--- /dev/null
+++ b/src/unix/random-getrandom.c
@@ -0,0 +1,88 @@
+/* Copyright libuv contributors. All rights reserved.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to
+ * deal in the Software without restriction, including without limitation the
+ * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
+ * sell copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ */
+
+#include "uv.h"
+#include "internal.h"
+
+#ifdef __linux__
+
+#include "linux-syscalls.h"
+
+#define uv__random_getrandom_init() 0
+
+#else  /* !__linux__ */
+
+#include <stddef.h>
+#include <dlfcn.h>
+
+typedef ssize_t (*uv__getrandom_cb)(void *, size_t, unsigned);
+
+static uv__getrandom_cb uv__getrandom;
+static uv_once_t once = UV_ONCE_INIT;
+
+static void uv__random_getrandom_init_once(void) {
+  uv__getrandom = (uv__getrandom_cb) dlsym(RTLD_DEFAULT, "getrandom");
+}
+
+static int uv__random_getrandom_init(void) {
+  uv_once(&once, uv__random_getrandom_init_once);
+
+  if (uv__getrandom == NULL)
+    return UV_ENOSYS;
+
+  return 0;
+}
+
+#endif  /* !__linux__ */
+
+int uv__random_getrandom(void* buf, size_t buflen) {
+  ssize_t n;
+  size_t pos;
+  int rc;
+
+  rc = uv__random_getrandom_init();
+  if (rc != 0)
+    return rc;
+
+  for (pos = 0; pos != buflen; pos += n) {
+    do {
+      n = buflen - pos;
+
+      /* Most getrandom() implementations promise that reads <= 256 bytes
+       * will always succeed and won't be interrupted by signals.
+       * It's therefore useful to split it up in smaller reads because
+       * one big read may, in theory, continuously fail with EINTR.
+       */
+      if (n > 256)
+        n = 256;
+
+      n = uv__getrandom((char *) buf + pos, n, 0);
+    } while (n == -1 && errno == EINTR);
+
+    if (n == -1)
+      return UV__ERR(errno);
+
+    if (n == 0)
+      return UV_EIO;
+  }
+
+  return 0;
+}