netbsd: use KERN_ARND sysctl to get entropy

PR-URL: https://github.com/libuv/libuv/pull/2528
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Saúl Ibarra Corretgé <s@saghul.net>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Santiago Gimeno <santiago.gimeno@gmail.com>

docs/src/misc.rst

@@ -679,6 +679,7 @@ API
       :man:`sysctl(2)`.
     - FreeBSD: `getrandom(2) <https://www.freebsd.org/cgi/man.cgi?query=getrandom&sektion=2>_`,
       or `/dev/urandom` after reading from `/dev/random` once.
+    - NetBSD: `KERN_ARND` `sysctl(3) <https://netbsd.gw.com/cgi-bin/man-cgi?sysctl+3+NetBSD-current>_`
     - macOS, OpenBSD: `getentropy(2) <https://man.openbsd.org/getentropy.2>_`
       if available, or `/dev/urandom` after reading from `/dev/random` once.
     - AIX: `/dev/random`.

src/random.c

@@ -40,6 +40,8 @@ static int uv__random(void* buf, size_t buflen) {
   rc = uv__random_getentropy(buf, buflen);
   if (rc == UV_ENOSYS)
     rc = uv__random_devurandom(buf, buflen);
+#elif defined(__NetBSD__)
+  rc = uv__random_sysctl(buf, buflen);
 #elif defined(__FreeBSD__) || defined(__linux__)
   rc = uv__random_getrandom(buf, buflen);
   if (rc == UV_ENOSYS)

src/unix/netbsd.c

@@ -234,3 +234,26 @@ int uv_cpu_info(uv_cpu_info_t** cpu_infos, int* count) {
   uv__free(cp_times);
   return 0;
 }
+
+int uv__random_sysctl(void* buf, size_t len) {
+  static int name[] = {CTL_KERN, KERN_ARND};
+  size_t count, req;
+  unsigned char* p;
+
+  p = buf;
+  while (len) {
+    req = len < 32 ? len : 32;
+    count = req;
+
+    if (sysctl(name, ARRAY_SIZE(name), p, &count, NULL, 0) == -1)
+      return UV__ERR(errno);
+
+    if (count != req)
+      return UV_EIO;  /* Can't happen. */
+
+    p += count;
+    len -= count;
+  }
+
+  return 0;
+}

src/unix/random-devurandom.c

@@ -74,10 +74,10 @@ int uv__random_readpath(const char* path, void* buf, size_t buflen) {
 static void uv__random_devurandom_init(void) {
   char c;
 
-  /* Linux's and NetBSD's random(4) man page suggests applications should read
-   * at least once from /dev/random before switching to /dev/urandom in order
-   * to seed the system RNG. Reads from /dev/random can of course block
-   * indefinitely until entropy is available but that's the point.
+  /* Linux's random(4) man page suggests applications should read at least
+   * once from /dev/random before switching to /dev/urandom in order to seed
+   * the system RNG. Reads from /dev/random can of course block indefinitely
+   * until entropy is available but that's the point.
    */
   status = uv__random_readpath("/dev/random", &c, 1);
 }

src/unix/random-sysctl-linux.c

@@ -40,7 +40,6 @@ struct uv__sysctl_args {
 };
 
 
-/* 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;