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, 91 insertions, 0 deletions

diff --git a/src/unix/random-sysctl.c b/src/unix/random-sysctl.c
new file mode 100644
index 00000000..7af2e320
--- /dev/null
+++ b/src/unix/random-sysctl.c
@@ -0,0 +1,91 @@
+/* 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"
+
+#include <errno.h>
+#include <string.h>
+
+#include <syscall.h>
+#include <unistd.h>
+
+
+struct uv__sysctl_args {
+  int* name;
+  int nlen;
+  void* oldval;
+  size_t* oldlenp;
+  void* newval;
+  size_t newlen;
+  unsigned long unused[4];
+};
+
+
+/* TODO(bnoordhuis) Use {CTL_KERN, KERN_ARND} on FreeBSD (and NetBSD?) */
+int uv__random_sysctl(void* buf, size_t buflen) {
+  static int name[] = {1 /*CTL_KERN*/, 40 /*KERN_RANDOM*/, 6 /*RANDOM_UUID*/};
+  struct uv__sysctl_args args;
+  char uuid[16];
+  char* p;
+  char* pe;
+  size_t n;
+
+  p = buf;
+  pe = p + buflen;
+
+  while (p < pe) {
+    memset(&args, 0, sizeof(args));
+
+    args.name = name;
+    args.nlen = ARRAY_SIZE(name);
+    args.oldval = uuid;
+    args.oldlenp = &n;
+    n = sizeof(uuid);
+
+    /* Emits a deprecation warning with some kernels but that seems like
+     * an okay trade-off for the fallback of the fallback: this function is
+     * only called when neither getrandom(2) nor /dev/urandom are available.
+     * Fails with ENOSYS on kernels configured without CONFIG_SYSCTL_SYSCALL.
+     */
+    if (syscall(SYS__sysctl, &args) == -1)
+      return UV__ERR(errno);
+
+    if (n != sizeof(uuid))
+      return UV_EIO;  /* Can't happen. */
+
+    /* uuid[] is now a type 4 UUID. Bytes 6 and 8 (counting from zero) contain
+     * 4 and 5 bits of entropy, respectively. For ease of use, we skip those
+     * and only use 14 of the 16 bytes.
+     */
+    uuid[6] = uuid[14];
+    uuid[8] = uuid[15];
+
+    n = pe - p;
+    if (n > 14)
+      n = 14;
+
+    memcpy(p, uuid, n);
+    p += n;
+  }
+
+  return 0;
+}