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>

CMakeLists.txt

@@ -14,6 +14,7 @@ set(uv_sources
     src/fs-poll.c
     src/idna.c
     src/inet.c
+    src/random.c
     src/strscpy.c
     src/threadpool.c
     src/timer.c
@@ -108,6 +109,7 @@ set(uv_test_sources
     test/test-process-title-threadsafe.c
     test/test-process-title.c
     test/test-queue-foreach-delete.c
+    test/test-random.c
     test/test-ref.c
     test/test-run-nowait.c
     test/test-run-once.c
@@ -236,6 +238,7 @@ else()
        src/unix/pipe.c
        src/unix/poll.c
        src/unix/process.c
+       src/unix/random-devurandom.c
        src/unix/signal.c
        src/unix/stream.c
        src/unix/tcp.c
@@ -284,6 +287,14 @@ if(APPLE OR CMAKE_SYSTEM_NAME MATCHES "DragonFly|FreeBSD|NetBSD|OpenBSD")
   list(APPEND uv_sources src/unix/bsd-ifaddrs.c src/unix/kqueue.c)
 endif()
 
+if(CMAKE_SYSTEM_NAME MATCHES "FreeBSD")
+  list(APPEND uv_sources src/unix/random-getrandom.c)
+endif()
+
+if(APPLE OR CMAKE_SYSTEM_NAME STREQUAL "OpenBSD")
+  list(APPEND uv_sources src/unix/random-getentropy.c)
+endif()
+
 if(APPLE)
   list(APPEND uv_defines _DARWIN_UNLIMITED_SELECT=1 _DARWIN_USE_64_BIT_INODE=1)
   list(APPEND uv_sources
@@ -300,6 +311,8 @@ if(CMAKE_SYSTEM_NAME STREQUAL "Linux")
        src/unix/linux-inotify.c
        src/unix/linux-syscalls.c
        src/unix/procfs-exepath.c
+       src/unix/random-getrandom.c
+       src/unix/random-sysctl.c
        src/unix/sysinfo-loadavg.c)
 endif()
 

Makefile.am

@@ -35,6 +35,7 @@ libuv_la_SOURCES = src/fs-poll.c \
                    src/idna.h \
                    src/inet.c \
                    src/queue.h \
+                   src/random.c \
                    src/strscpy.c \
                    src/strscpy.h \
                    src/threadpool.c \
@@ -105,6 +106,7 @@ libuv_la_SOURCES += src/unix/async.c \
                    src/unix/pipe.c \
                    src/unix/poll.c \
                    src/unix/process.c \
+                   src/unix/random-devurandom.c \
                    src/unix/signal.c \
                    src/unix/spinlock.h \
                    src/unix/stream.c \
@@ -240,6 +242,7 @@ test_run_tests_SOURCES = test/blackhole-server.c \
                          test/test-process-title.c \
                          test/test-process-title-threadsafe.c \
                          test/test-queue-foreach-delete.c \
+                         test/test-random.c \
                          test/test-ref.c \
                          test/test-run-nowait.c \
                          test/test-run-once.c \
@@ -414,7 +417,8 @@ libuv_la_SOURCES += src/unix/bsd-ifaddrs.c \
                     src/unix/darwin-proctitle.c \
                     src/unix/fsevents.c \
                     src/unix/kqueue.c \
-                    src/unix/proctitle.c
+                    src/unix/proctitle.c \
+                    src/unix/random-getentropy.c
 test_run_tests_LDFLAGS += -lutil
 endif
 
@@ -434,7 +438,8 @@ libuv_la_SOURCES += src/unix/bsd-ifaddrs.c \
                     src/unix/bsd-proctitle.c \
                     src/unix/freebsd.c \
                     src/unix/kqueue.c \
-                    src/unix/posix-hrtime.c
+                    src/unix/posix-hrtime.c \
+                    src/unix/random-getrandom.c
 test_run_tests_LDFLAGS += -lutil
 endif
 
@@ -465,6 +470,8 @@ libuv_la_SOURCES += src/unix/linux-core.c \
                     src/unix/linux-syscalls.h \
                     src/unix/procfs-exepath.c \
                     src/unix/proctitle.c \
+                    src/unix/random-getrandom.c \
+                    src/unix/random-sysctl.c \
                     src/unix/sysinfo-loadavg.c
 test_run_tests_LDFLAGS += -lutil
 endif
@@ -498,7 +505,8 @@ libuv_la_SOURCES += src/unix/bsd-ifaddrs.c \
                     src/unix/bsd-proctitle.c \
                     src/unix/kqueue.c \
                     src/unix/openbsd.c \
-                    src/unix/posix-hrtime.c
+                    src/unix/posix-hrtime.c \
+                    src/unix/random-getentropy.c
 test_run_tests_LDFLAGS += -lutil
 endif
 

docs/src/misc.rst

@@ -46,6 +46,12 @@ Data types
         Replacement function for :man:`free(3)`.
         See :c:func:`uv_replace_allocator`.
 
+.. c:type::  void (*uv_random_cb)(uv_random_t* req, int status, void* buf, size_t buflen)
+
+    Callback passed to :c:func:`uv_random`. `status` is non-zero in case of
+    error. The `buf` pointer is the same pointer that was passed to
+    :c:func:`uv_random`.
+
 .. c:type:: uv_file
 
     Cross platform representation of a file handle.
@@ -191,6 +197,9 @@ Data types
         char* value;
     } uv_env_item_t;
 
+.. c:type:: uv_random_t
+
+    Random data request type.
 
 API
 ---
@@ -648,3 +657,39 @@ API
     argument to `gettimeofday()` is not supported, as it is considered obsolete.
 
     .. versionadded:: 1.28.0
+
+.. c:function:: int uv_random(uv_loop_t* loop, uv_random_t* req, void* buf, size_t buflen, unsigned int flags, uv_random_cb cb)
+
+    Fill `buf` with exactly `buflen` cryptographically strong random bytes
+    acquired from the system CSPRNG. `flags` is reserved for future extension
+    and must currently be 0.
+
+    Short reads are not possible. When less than `buflen` random bytes are
+    available, a non-zero error value is returned or passed to the callback.
+
+    The synchronous version may block indefinitely when not enough entropy
+    is available. The asynchronous version may not ever finish when the system
+    is low on entropy.
+
+    Sources of entropy:
+
+    - Windows: `RtlGenRandom <https://docs.microsoft.com/en-us/windows/desktop/api/ntsecapi/nf-ntsecapi-rtlgenrandom>_`.
+    - Linux, Android: :man:`getrandom(2)` if available, or :man:`urandom(4)`
+      after reading from `/dev/random` once, or the `KERN_RANDOM`
+      :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.
+    - macOS, OpenBSD: `getentropy(2) <https://man.openbsd.org/getentropy.2>_`
+      if available, or `/dev/urandom` after reading from `/dev/random` once.
+    - AIX: `/dev/random`.
+    - IBM i: `/dev/urandom`.
+    - Other UNIX: `/dev/urandom` after reading from `/dev/random` once.
+
+    :returns: 0 on success, or an error code < 0 on failure. The contents of
+    `buf` is undefined after an error.
+
+    .. note::
+        When using the synchronous version, both `loop` and `req` parameters
+        are not used and can be set to `NULL`.
+
+    .. versionadded:: 1.33.0

include/uv.h

@@ -177,6 +177,7 @@ extern "C" {
   XX(WORK, work)                                                              \
   XX(GETADDRINFO, getaddrinfo)                                                \
   XX(GETNAMEINFO, getnameinfo)                                                \
+  XX(RANDOM, random)                                                          \
 
 typedef enum {
 #define XX(code, _) UV_ ## code = UV__ ## code,
@@ -234,6 +235,7 @@ typedef struct uv_connect_s uv_connect_t;
 typedef struct uv_udp_send_s uv_udp_send_t;
 typedef struct uv_fs_s uv_fs_t;
 typedef struct uv_work_s uv_work_t;
+typedef struct uv_random_s uv_random_t;
 
 /* None of the above. */
 typedef struct uv_env_item_s uv_env_item_t;
@@ -330,6 +332,10 @@ typedef void (*uv_getnameinfo_cb)(uv_getnameinfo_t* req,
                                   int status,
                                   const char* hostname,
                                   const char* service);
+typedef void (*uv_random_cb)(uv_random_t* req,
+                             int status,
+                             void* buf,
+                             size_t buflen);
 
 typedef struct {
   long tv_sec;
@@ -1574,6 +1580,26 @@ UV_EXTERN int uv_ip6_name(const struct sockaddr_in6* src, char* dst, size_t size
 UV_EXTERN int uv_inet_ntop(int af, const void* src, char* dst, size_t size);
 UV_EXTERN int uv_inet_pton(int af, const char* src, void* dst);
 
+
+struct uv_random_s {
+  UV_REQ_FIELDS
+  /* read-only */
+  uv_loop_t* loop;
+  /* private */
+  int status;
+  void* buf;
+  size_t buflen;
+  uv_random_cb cb;
+  struct uv__work work_req;
+};
+
+UV_EXTERN int uv_random(uv_loop_t* loop,
+                        uv_random_t* req,
+                        void *buf,
+                        size_t buflen,
+                        unsigned flags,  /* For future extension; must be 0. */
+                        uv_random_cb cb);
+
 #if defined(IF_NAMESIZE)
 # define UV_IF_NAMESIZE (IF_NAMESIZE + 1)
 #elif defined(IFNAMSIZ)

src/random.c

@@ -0,0 +1,120 @@
+/* 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 "uv-common.h"
+
+#ifdef _WIN32
+#  include "win/internal.h"
+#else
+#  include "unix/internal.h"
+#endif
+
+static int uv__random(void* buf, size_t buflen) {
+  int rc;
+
+#if defined(__PASE__)
+  rc = uv__random_readpath("/dev/urandom", buf, buflen);
+#elif defined(_AIX)
+  rc = uv__random_readpath("/dev/random", buf, buflen);
+#elif defined(__APPLE__) || defined(__OpenBSD__)
+  rc = uv__random_getentropy(buf, buflen);
+  if (rc == UV_ENOSYS)
+    rc = uv__random_devurandom(buf, buflen);
+#elif defined(__FreeBSD__) || defined(__linux__)
+  rc = uv__random_getrandom(buf, buflen);
+  if (rc == UV_ENOSYS)
+    rc = uv__random_devurandom(buf, buflen);
+# if defined(__linux__)
+  switch (rc) {
+    case UV_EACCES:
+    case UV_EIO:
+    case UV_ELOOP:
+    case UV_EMFILE:
+    case UV_ENFILE:
+    case UV_ENOENT:
+    case UV_EPERM:
+      rc = uv__random_sysctl(buf, buflen);
+      break;
+  }
+# endif
+#elif defined(_WIN32)
+  uv__once_init();
+  rc = uv__random_rtlgenrandom(buf, buflen);
+#else
+  rc = uv__random_devurandom(buf, buflen);
+#endif
+
+  return rc;
+}
+
+
+static void uv__random_work(struct uv__work* w) {
+  uv_random_t* req;
+
+  req = container_of(w, uv_random_t, work_req);
+  req->status = uv__random(req->buf, req->buflen);
+}
+
+
+static void uv__random_done(struct uv__work* w, int status) {
+  uv_random_t* req;
+
+  req = container_of(w, uv_random_t, work_req);
+  uv__req_unregister(req->loop, req);
+
+  if (status == 0)
+    status = req->status;
+
+  req->cb(req, status, req->buf, req->buflen);
+}
+
+
+int uv_random(uv_loop_t* loop,
+              uv_random_t* req,
+              void *buf,
+              size_t buflen,
+              unsigned flags,
+              uv_random_cb cb) {
+  if (buflen > 0x7FFFFFFFu)
+    return UV_E2BIG;
+
+  if (flags != 0)
+    return UV_EINVAL;
+
+  if (cb == NULL)
+    return uv__random(buf, buflen);
+
+  uv__req_init(loop, req, UV_RANDOM);
+  req->loop = loop;
+  req->status = 0;
+  req->cb = cb;
+  req->buf = buf;
+  req->buflen = buflen;
+
+  uv__work_submit(loop,
+                  &req->work_req,
+                  UV__WORK_CPU,
+                  uv__random_work,
+                  uv__random_done);
+
+  return 0;
+}

src/threadpool.c

@@ -372,6 +372,10 @@ int uv_cancel(uv_req_t* req) {
     loop = ((uv_getnameinfo_t*) req)->loop;
     wreq = &((uv_getnameinfo_t*) req)->work_req;
     break;
+  case UV_RANDOM:
+    loop = ((uv_random_t*) req)->loop;
+    wreq = &((uv_random_t*) req)->work_req;
+    break;
   case UV_WORK:
     loop =  ((uv_work_t*) req)->loop;
     wreq = &((uv_work_t*) req)->work_req;

src/unix/internal.h

@@ -270,6 +270,12 @@ uv_handle_type uv__handle_type(int fd);
 FILE* uv__open_file(const char* path);
 int uv__getpwuid_r(uv_passwd_t* pwd);
 
+/* random */
+int uv__random_devurandom(void* buf, size_t buflen);
+int uv__random_getrandom(void* buf, size_t buflen);
+int uv__random_getentropy(void* buf, size_t buflen);
+int uv__random_readpath(const char* path, void* buf, size_t buflen);
+int uv__random_sysctl(void* buf, size_t buflen);
 
 #if defined(__APPLE__)
 int uv___stream_fd(const uv_stream_t* handle);

src/unix/linux-syscalls.c

@@ -203,6 +203,22 @@
 # endif
 #endif /* __NR_statx */
 
+#ifndef __NR_getrandom
+# if defined(__x86_64__)
+#  define __NR_getrandom 318
+# elif defined(__i386__)
+#  define __NR_getrandom 355
+# elif defined(__aarch64__)
+#  define __NR_getrandom 384
+# elif defined(__arm__)
+#  define __NR_getrandom (UV_SYSCALL_BASE + 384)
+# elif defined(__ppc__)
+#  define __NR_getrandom 359
+# elif defined(__s390__)
+#  define __NR_getrandom 349
+# endif
+#endif /* __NR_getrandom */
+
 int uv__accept4(int fd, struct sockaddr* addr, socklen_t* addrlen, int flags) {
 #if defined(__i386__)
   unsigned long args[4];
@@ -367,3 +383,12 @@ int uv__statx(int dirfd,
   return errno = ENOSYS, -1;
 #endif
 }
+
+
+ssize_t uv__getrandom(void* buf, size_t buflen, unsigned flags) {
+#if defined(__NR_getrandom)
+  return syscall(__NR_getrandom, buf, buflen, flags);
+#else
+  return errno = ENOSYS, -1;
+#endif
+}

src/unix/linux-syscalls.h

@@ -148,5 +148,6 @@ int uv__statx(int dirfd,
               int flags,
               unsigned int mask,
               struct uv__statx* statxbuf);
+ssize_t uv__getrandom(void* buf, size_t buflen, unsigned flags);
 
 #endif /* UV_LINUX_SYSCALL_H_ */

src/unix/random-devurandom.c

@@ -0,0 +1,93 @@
+/* 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 <sys/stat.h>
+#include <unistd.h>
+
+static uv_once_t once = UV_ONCE_INIT;
+static int status;
+
+
+int uv__random_readpath(const char* path, void* buf, size_t buflen) {
+  struct stat s;
+  size_t pos;
+  ssize_t n;
+  int fd;
+
+  fd = uv__open_cloexec(path, O_RDONLY);
+
+  if (fd == -1)
+    return UV__ERR(errno);
+
+  if (fstat(fd, &s)) {
+    uv__close(fd);
+    return UV__ERR(errno);
+  }
+
+  if (!S_ISCHR(s.st_mode)) {
+    uv__close(fd);
+    return UV_EIO;
+  }
+
+  for (pos = 0; pos != buflen; pos += n) {
+    do
+      n = read(fd, (char*) buf + pos, buflen - pos);
+    while (n == -1 && errno == EINTR);
+
+    if (n == -1) {
+      uv__close(fd);
+      return UV__ERR(errno);
+    }
+
+    if (n == 0) {
+      uv__close(fd);
+      return UV_EIO;
+    }
+  }
+
+  uv__close(fd);
+  return 0;
+}
+
+
+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.
+   */
+  status = uv__random_readpath("/dev/random", &c, 1);
+}
+
+
+int uv__random_devurandom(void* buf, size_t buflen) {
+  uv_once(&once, uv__random_devurandom_init);
+
+  if (status != 0)
+    return status;
+
+  return uv__random_readpath("/dev/urandom", buf, buflen);
+}

src/unix/random-getentropy.c

@@ -0,0 +1,57 @@
+/* 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 <stddef.h>
+#include <dlfcn.h>
+
+typedef int (*uv__getentropy_cb)(void *, size_t);
+
+static uv__getentropy_cb uv__getentropy;
+static uv_once_t once = UV_ONCE_INIT;
+
+
+static void uv__random_getentropy_init(void) {
+  uv__getentropy = (uv__getentropy_cb) dlsym(RTLD_DEFAULT, "getentropy");
+}
+
+
+int uv__random_getentropy(void* buf, size_t buflen) {
+  size_t pos;
+  size_t stride;
+
+  uv_once(&once, uv__random_getentropy_init);
+
+  if (uv__getentropy == NULL)
+    return UV_ENOSYS;
+
+  /* getentropy() returns an error for requests > 256 bytes. */
+  for (pos = 0, stride = 256; pos + stride < buflen; pos += stride)
+    if (uv__getentropy((char *) buf + pos, stride))
+      return UV__ERR(errno);
+
+  if (uv__getentropy((char *) buf + pos, buflen - pos))
+    return UV__ERR(errno);
+
+  return 0;
+}

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;
+}

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;
+}

src/win/internal.h

@@ -280,6 +280,8 @@ int uv__getsockpeername(const uv_handle_t* handle,
                         int* namelen,
                         int delayed_error);
 
+int uv__random_rtlgenrandom(void* buf, size_t buflen);
+
 
 /*
  * Process stdio handles.

src/win/util.c

@@ -1860,3 +1860,16 @@ int uv_gettimeofday(uv_timeval64_t* tv) {
   tv->tv_usec = (int32_t) (((ularge.QuadPart - epoch) % 10000000L) / 10);
   return 0;
 }
+
+int uv__random_rtlgenrandom(void* buf, size_t buflen) {
+  if (pRtlGenRandom == NULL)
+    return UV_ENOSYS;
+
+  if (buflen == 0)
+    return 0;
+
+  if (pRtlGenRandom(buf, buflen) == FALSE)
+    return UV_EIO;
+
+  return 0;
+}

src/win/winapi.c

@@ -36,6 +36,9 @@ sNtQueryDirectoryFile pNtQueryDirectoryFile;
 sNtQuerySystemInformation pNtQuerySystemInformation;
 sNtQueryInformationProcess pNtQueryInformationProcess;
 
+/* Advapi32 function pointers */
+sRtlGenRandom pRtlGenRandom;
+
 /* Kernel32 function pointers */
 sGetQueuedCompletionStatusEx pGetQueuedCompletionStatusEx;
 
@@ -51,6 +54,7 @@ void uv_winapi_init(void) {
   HMODULE powrprof_module;
   HMODULE user32_module;
   HMODULE kernel32_module;
+  HMODULE advapi32_module;
 
   ntdll_module = GetModuleHandleA("ntdll.dll");
   if (ntdll_module == NULL) {
@@ -135,4 +139,11 @@ void uv_winapi_init(void) {
       GetProcAddress(user32_module, "SetWinEventHook");
   }
 
+  advapi32_module = GetModuleHandleA("advapi32.dll");
+  if (advapi32_module == NULL) {
+    uv_fatal_error(GetLastError(), "GetModuleHandleA");
+  }
+
+  pRtlGenRandom =
+      (sRtlGenRandom) GetProcAddress(advapi32_module, "SystemFunction036");
 }

src/win/winapi.h

@@ -4589,6 +4589,11 @@ typedef NTSTATUS (NTAPI *sNtQueryInformationProcess)
                   ULONG Length,
                   PULONG ReturnLength);
 
+/*
+ * Advapi32 headers
+ */
+typedef BOOLEAN (WINAPI *sRtlGenRandom)(PVOID Buffer, ULONG BufferLength);
+
 /*
  * Kernel32 headers
  */
@@ -4731,6 +4736,9 @@ extern sNtQueryDirectoryFile pNtQueryDirectoryFile;
 extern sNtQuerySystemInformation pNtQuerySystemInformation;
 extern sNtQueryInformationProcess pNtQueryInformationProcess;
 
+/* Advapi32 function pointers */
+extern sRtlGenRandom pRtlGenRandom;
+
 /* Kernel32 function pointers */
 extern sGetQueuedCompletionStatusEx pGetQueuedCompletionStatusEx;
 

test/test-list.h

@@ -395,6 +395,7 @@ TEST_DECLARE   (threadpool_queue_work_einval)
 TEST_DECLARE   (threadpool_multiple_event_loops)
 TEST_DECLARE   (threadpool_cancel_getaddrinfo)
 TEST_DECLARE   (threadpool_cancel_getnameinfo)
+TEST_DECLARE   (threadpool_cancel_random)
 TEST_DECLARE   (threadpool_cancel_work)
 TEST_DECLARE   (threadpool_cancel_fs)
 TEST_DECLARE   (threadpool_cancel_single)
@@ -464,6 +465,9 @@ HELPER_DECLARE (pipe_echo_server)
 
 TEST_DECLARE   (queue_foreach_delete)
 
+TEST_DECLARE   (random_async)
+TEST_DECLARE   (random_sync)
+
 TEST_DECLARE   (handle_type_name)
 TEST_DECLARE   (req_type_name)
 TEST_DECLARE   (getters_setters)
@@ -1000,6 +1004,7 @@ TASK_LIST_START
   TEST_ENTRY_CUSTOM (threadpool_multiple_event_loops, 0, 0, 60000)
   TEST_ENTRY  (threadpool_cancel_getaddrinfo)
   TEST_ENTRY  (threadpool_cancel_getnameinfo)
+  TEST_ENTRY  (threadpool_cancel_random)
   TEST_ENTRY  (threadpool_cancel_work)
   TEST_ENTRY  (threadpool_cancel_fs)
   TEST_ENTRY  (threadpool_cancel_single)
@@ -1018,6 +1023,9 @@ TASK_LIST_START
 
   TEST_ENTRY  (queue_foreach_delete)
 
+  TEST_ENTRY  (random_async)
+  TEST_ENTRY  (random_sync)
+
   TEST_ENTRY  (handle_type_name)
   TEST_ENTRY  (req_type_name)
   TEST_ENTRY  (getters_setters)

test/test-random.c

@@ -0,0 +1,94 @@
+/* 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 "task.h"
+
+#include <string.h>
+
+static char scratch[256];
+static int random_cb_called;
+
+
+static void random_cb(uv_random_t* req, int status, void* buf, size_t buflen) {
+  char zero[sizeof(scratch)];
+
+  memset(zero, 0, sizeof(zero));
+
+  ASSERT(0 == status);
+  ASSERT(buf == (void*) scratch);
+
+  if (random_cb_called == 0) {
+    ASSERT(buflen == 0);
+    ASSERT(0 == memcmp(scratch, zero, sizeof(zero)));
+  } else {
+    ASSERT(buflen == sizeof(scratch));
+    /* Buy a lottery ticket if you manage to trip this assertion. */
+    ASSERT(0 != memcmp(scratch, zero, sizeof(zero)));
+  }
+
+  random_cb_called++;
+}
+
+
+TEST_IMPL(random_async) {
+  uv_random_t req;
+  uv_loop_t* loop;
+
+  loop = uv_default_loop();
+  ASSERT(UV_EINVAL == uv_random(loop, &req, scratch, sizeof(scratch), -1,
+                                random_cb));
+  ASSERT(UV_E2BIG == uv_random(loop, &req, scratch, -1, -1, random_cb));
+
+  ASSERT(0 == uv_random(loop, &req, scratch, 0, 0, random_cb));
+  ASSERT(0 == random_cb_called);
+
+  ASSERT(0 == uv_run(loop, UV_RUN_DEFAULT));
+  ASSERT(1 == random_cb_called);
+
+  ASSERT(0 == uv_random(loop, &req, scratch, sizeof(scratch), 0, random_cb));
+  ASSERT(1 == random_cb_called);
+
+  ASSERT(0 == uv_run(loop, UV_RUN_DEFAULT));
+  ASSERT(2 == random_cb_called);
+
+  MAKE_VALGRIND_HAPPY();
+  return 0;
+}
+
+
+TEST_IMPL(random_sync) {
+  char zero[256];
+  char buf[256];
+
+  ASSERT(UV_EINVAL == uv_random(NULL, NULL, buf, sizeof(buf), -1, NULL));
+  ASSERT(UV_E2BIG == uv_random(NULL, NULL, buf, -1, -1, NULL));
+
+  memset(buf, 0, sizeof(buf));
+  ASSERT(0 == uv_random(NULL, NULL, buf, sizeof(buf), 0, NULL));
+
+  /* Buy a lottery ticket if you manage to trip this assertion. */
+  memset(zero, 0, sizeof(zero));
+  ASSERT(0 != memcmp(buf, zero, sizeof(zero)));
+
+  MAKE_VALGRIND_HAPPY();
+  return 0;
+}

test/test-threadpool-cancel.c

@@ -37,6 +37,11 @@ struct cancel_info {
   uv_timer_t timer_handle;
 };
 
+struct random_info {
+  uv_random_t random_req;
+  char buf[1];
+};
+
 static unsigned fs_cb_called;
 static unsigned done_cb_called;
 static unsigned done2_cb_called;
@@ -143,6 +148,19 @@ static void nop_done_cb(uv_work_t* req, int status) {
 }
 
 
+static void nop_random_cb(uv_random_t* req, int status, void* buf, size_t len) {
+  struct random_info* ri;
+
+  ri = container_of(req, struct random_info, random_req);
+
+  ASSERT(status == UV_ECANCELED);
+  ASSERT(buf == (void*) ri->buf);
+  ASSERT(len == sizeof(ri->buf));
+
+  done_cb_called++;
+}
+
+
 TEST_IMPL(threadpool_cancel_getaddrinfo) {
   uv_getaddrinfo_t reqs[4];
   struct cancel_info ci;
@@ -212,6 +230,29 @@ TEST_IMPL(threadpool_cancel_getnameinfo) {
 }
 
 
+TEST_IMPL(threadpool_cancel_random) {
+  struct random_info req;
+  uv_loop_t* loop;
+
+  saturate_threadpool();
+  loop = uv_default_loop();
+  ASSERT(0 == uv_random(loop,
+                        &req.random_req,
+                        &req.buf,
+                        sizeof(req.buf),
+                        0,
+                        nop_random_cb));
+  ASSERT(0 == uv_cancel((uv_req_t*) &req));
+  ASSERT(0 == done_cb_called);
+  unblock_threadpool();
+  ASSERT(0 == uv_run(loop, UV_RUN_DEFAULT));
+  ASSERT(1 == done_cb_called);
+
+  MAKE_VALGRIND_HAPPY();
+  return 0;
+}
+
+
 TEST_IMPL(threadpool_cancel_work) {
   struct cancel_info ci;
   uv_work_t reqs[16];

test/test.gyp

@@ -90,6 +90,7 @@
         'test-process-title.c',
         'test-process-title-threadsafe.c',
         'test-queue-foreach-delete.c',
+        'test-random.c',
         'test-ref.c',
         'test-run-nowait.c',
         'test-run-once.c',

uv.gyp

@@ -75,6 +75,7 @@
         'src/idna.h',
         'src/inet.c',
         'src/queue.h',
+        'src/random.c',
         'src/strscpy.c',
         'src/strscpy.h',
         'src/threadpool.c',
@@ -167,6 +168,7 @@
             'src/unix/pipe.c',
             'src/unix/poll.c',
             'src/unix/process.c',
+            'src/unix/random-devurandom.c',
             'src/unix/signal.c',
             'src/unix/spinlock.h',
             'src/unix/stream.c',
@@ -226,7 +228,8 @@
           'sources': [
             'src/unix/darwin.c',
             'src/unix/fsevents.c',
-            'src/unix/darwin-proctitle.c'
+            'src/unix/darwin-proctitle.c',
+            'src/unix/random-getentropy.c',
           ],
           'defines': [
             '_DARWIN_USE_64_BIT_INODE=1',
@@ -241,6 +244,8 @@
             'src/unix/linux-syscalls.c',
             'src/unix/linux-syscalls.h',
             'src/unix/procfs-exepath.c',
+            'src/unix/random-getrandom.c',
+            'src/unix/random-sysctl.c',
             'src/unix/sysinfo-loadavg.c',
           ],
           'link_settings': {
@@ -320,8 +325,14 @@
         [ 'OS=="freebsd" or OS=="dragonflybsd"', {
           'sources': [ 'src/unix/freebsd.c' ],
         }],
+        [ 'OS=="freebsd"', {
+          'sources': [ 'src/unix/random-getrandom.c' ],
+        }],
         [ 'OS=="openbsd"', {
-          'sources': [ 'src/unix/openbsd.c' ],
+          'sources': [
+            'src/unix/openbsd.c',
+            'src/unix/random-getentropy.c',
+          ],
         }],
         [ 'OS=="netbsd"', {
           'link_settings': {