Add getentropy, getrandom, <sys/random.h> [BZ #17252]

1 files changed, 245 insertions, 0 deletions

diff --git a/stdlib/tst-getrandom.c b/stdlib/tst-getrandom.c
new file mode 100644
index 0000000000..a76cd1868b
--- /dev/null
+++ b/stdlib/tst-getrandom.c
@@ -0,0 +1,245 @@
+/* Tests for the getentropy, getrandom functions.
+   Copyright (C) 2016 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <errno.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <string.h>
+#include <sys/random.h>
+
+/* Set to true if any errors are encountered.  */
+static bool errors;
+
+/* Test getrandom with a single buffer length.  NB: The passed-in
+   buffer must have room for four extra bytes after the specified
+   length, which are used to test that getrandom leaves those bytes
+   unchanged.  */
+static void
+test_length (char *buffer, size_t length, unsigned int flags)
+{
+  memset (buffer, 0, length);
+  strcpy (buffer + length, "123");
+  ssize_t ret = getrandom (buffer, length, flags);
+  if (ret < 0)
+    {
+      /* EAGAIN is an expected error with GRND_RANDOM and
+         GRND_NONBLOCK.  */
+      if ((flags & GRND_RANDOM)
+          && (flags & GRND_NONBLOCK)
+          && errno == EAGAIN)
+        return;
+      printf ("error: getrandom (%zu, 0x%x): %m\n", length, flags);
+      errors = true;
+      return;
+    }
+ if (ret != length)
+    {
+      if (flags & GRND_RANDOM)
+        {
+          if (ret == 0 || ret > length)
+            {
+              printf ("error: getrandom (%zu, 0x%x) returned %zd\n",
+                      length, flags, ret);
+              errors = true;
+            }
+        }
+      else
+        {
+          printf ("error: getrandom (%zu, 0x%x) returned %zd\n",
+                  length, flags, ret);
+          errors = true;
+        }
+    }
+  if (length >= 7)
+    {
+      /* One spurious test failure in 2**56 is sufficiently
+         unlikely.  */
+      int non_null = 0;
+      for (int i = 0; i < length; ++i)
+        non_null += buffer[i] != 0;
+      if (non_null == 0)
+        {
+          printf ("error: getrandom (%zu, 0x%x) returned all-zero bytes\n",
+                  length, flags);
+          errors = true;
+        }
+    }
+  if (memcmp (buffer + length, "123", 4) != 0)
+    {
+      printf ("error: getrandom (%zu, 0x%x) wrote spurious bytes\n",
+              length, flags);
+      errors = true;
+    }
+}
+
+/* Call getrandom repeatedly to fill the buffer.  */
+static bool
+getrandom_full (char *buffer, size_t length, unsigned int flags)
+{
+  char *end = buffer + length;
+  while (buffer < end)
+    {
+      ssize_t ret = getrandom (buffer, end - buffer, flags);
+      if (ret < 0)
+        {
+          printf ("error: getrandom (%zu, 0x%x): %m\n", length, flags);
+          errors = true;
+          return false;
+        }
+      buffer += ret;
+    }
+
+  return true;
+}
+
+static void
+test_flags (unsigned int flags)
+{
+  /* Test various lengths, but only for !GRND_RANDOM, to conserve
+     entropy.  */
+  {
+    enum { max_length = 300 };
+    char buffer[max_length + 4];
+    if (flags & GRND_RANDOM)
+      test_length (buffer, 0, flags);
+    else
+      {
+        for (int length = 0; length <= 9; ++length)
+          test_length (buffer, length, flags);
+        test_length (buffer, 16, flags);
+        test_length (buffer, max_length, flags);
+      }
+  }
+
+  /* Test that getrandom returns different data.  */
+  if (!(flags & GRND_NONBLOCK))
+    {
+      char buffer1[8];
+      memset (buffer1, 0, sizeof (buffer1));
+
+      char buffer2[8];
+      memset (buffer2, 0, sizeof (buffer2));
+
+      if (getrandom_full (buffer1, sizeof (buffer1), flags)
+          && getrandom_full (buffer2, sizeof (buffer2), flags))
+        {
+          /* The probability that these two 8-byte buffers are equal
+             is very small (assuming that two subsequent calls to
+             getrandom result are independent, uniformly distributed
+             random variables).  */
+          if (memcmp (buffer1, buffer2, sizeof (buffer1)) == 0)
+            {
+              printf ("error: getrandom returns constant value\n");
+              errors = true;
+            }
+        }
+    }
+}
+
+static void
+test_getentropy (void)
+{
+  char buf[16];
+  memset (buf, '@', sizeof (buf));
+  if (getentropy (buf, 0) != 0)
+    {
+      printf ("error: getentropy zero length: %m\n");
+      errors = true;
+      return;
+    }
+  for (size_t i = 0; i < sizeof (buf); ++i)
+    if (buf[i] != '@')
+      {
+        printf ("error: getentropy modified zero-length buffer\n");
+        errors = true;
+        return;
+      }
+
+  if (getentropy (buf, sizeof (buf)) != 0)
+    {
+      printf ("error: getentropy buf: %m\n");
+      errors = true;
+      return;
+    }
+
+  char buf2[256];
+  _Static_assert (sizeof (buf) < sizeof (buf2), "buf and buf2 compatible");
+  memset (buf2, '@', sizeof (buf2));
+  if (getentropy (buf2, sizeof (buf)) != 0)
+    {
+      printf ("error: getentropy buf2: %m\n");
+      errors = true;
+      return;
+    }
+
+  /* The probability that these two buffers are equal is very
+     small. */
+  if (memcmp (buf, buf2, sizeof (buf) == 0))
+    {
+      printf ("error: getentropy appears to return constant bytes\n");
+      errors = true;
+      return;
+    }
+
+  for (size_t i = sizeof (buf); i < sizeof (buf2); ++i)
+    if (buf2[i] != '@')
+      {
+        printf ("error: getentropy wrote beyond the end of the buffer\n");
+        errors = true;
+        return;
+      }
+
+  char buf3[257];
+  if (getentropy (buf3, sizeof (buf3)) == 0)
+    {
+      printf ("error: getentropy successful for 257 byte buffer\n");
+      errors = true;
+      return;
+    }
+  if (errno != EIO)
+    {
+      printf ("error: getentropy wrong error for 257 byte buffer: %m\n");
+      errors = true;
+      return;
+    }
+}
+
+static int
+do_test (void)
+{
+  /* Check if getrandom is not supported by this system.  */
+  if (getrandom (NULL, 0, 0) == -1 && errno == ENOSYS)
+    return 77;
+
+  for (int use_random = 0; use_random < 2; ++use_random)
+    for (int use_nonblock = 0; use_nonblock < 2; ++use_nonblock)
+      {
+        unsigned int flags = 0;
+        if (use_random)
+          flags |= GRND_RANDOM;
+        if (use_nonblock)
+          flags |= GRND_NONBLOCK;
+        test_flags (flags);
+      }
+
+  test_getentropy ();
+
+  return errors;
+}
+
+#include <support/test-driver.c>