mono/utils/mono-rand-windows.c

   1 /**
   2  * \file
   3  * Windows rand support for Mono.
   4  *
   5  * Copyright 2016 Microsoft
   6  * Licensed under the MIT license. See LICENSE file in the project root for full license information.
   7 */
   8 #include <config.h>
   9 #include <glib.h>
  10 #ifdef HOST_WIN32
  11 #include "mono-error.h"
  12 #include "mono-error-internals.h"
  13 #include "mono-rand.h"
  14 #include <windows.h>
  15 #include <bcrypt.h>
  16 #include <limits.h>
  17
  18 // This implementation requires Windows 7 or newer.
  19
  20 #define BCRYPT_USE_SYSTEM_PREFERRED_RNG 0x00000002
  21 const static char mono_rand_provider [ ] = "BCryptGenRandom";
  22
  23 /**
  24  * mono_rand_open:
  25  *
  26  * Returns: True if random source is global, false if mono_rand_init can be called repeatedly to get randomness instances.
  27  *
  28  * Initializes entire RNG system. Must be called once per process before calling mono_rand_init.
  29  */
  30 gboolean
  31 mono_rand_open (void)
  32 {
  33         return TRUE;
  34 }
  35
  36 /**
  37  * mono_rand_init:
  38  * \param seed A string containing seed data
  39  * \param seed_size Length of seed string
  40  * Initializes an RNG client.
  41  * \returns On success, a non-NULL handle which can be used to fetch random data from \c mono_rand_try_get_bytes. On failure, NULL.
  42  */
  43 gpointer
  44 mono_rand_init (const guchar *seed, gssize seed_size)
  45 {
  46         // NULL will be interpreted as failure; return arbitrary nonzero pointer
  47         return (gpointer)mono_rand_provider;
  48 }
  49
  50 /**
  51  * mono_rand_try_get_bytes:
  52  * \param handle A pointer to an RNG handle. Handle is set to NULL on failure.
  53  * \param buffer A buffer into which to write random data.
  54  * \param buffer_size Number of bytes to write into buffer.
  55  * \param error Set on error.
  56  * Extracts bytes from an RNG handle.
  57  * \returns FALSE on failure and sets \p error, TRUE on success.
  58  */
  59 gboolean
  60 mono_rand_try_get_bytes (gpointer *handle, guchar *buffer, gssize buffer_size, MonoError *error)
  61 {
  62         g_assert (buffer || !buffer_size);
  63         error_init (error);
  64         g_assert (handle);
  65         gpointer const handle_value = *handle;
  66         g_assert (handle_value == 0 || handle_value == mono_rand_provider);
  67         if (!handle_value)
  68                 return FALSE;
  69         while (buffer_size > 0) {
  70                 ULONG const size = (ULONG)MIN (buffer_size, ULONG_MAX);
  71                 NTSTATUS const status = BCryptGenRandom (0, buffer, size, BCRYPT_USE_SYSTEM_PREFERRED_RNG);
  72                 if (!BCRYPT_SUCCESS (status)) {
  73                         mono_error_set_execution_engine (error, "Failed to gen random bytes (%ld)", status);
  74                         // failure, clear provider for future attempts
  75                         *handle = 0;
  76                         return FALSE;
  77                 }
  78                 buffer += size;
  79                 buffer_size -= size;
  80         }
  81         return TRUE;
  82 }
  83
  84 /**
  85  * mono_rand_close:
  86  * \param handle An RNG handle.
  87  * Releases an RNG handle.
  88  */
  89 void
  90 mono_rand_close (gpointer handle)
  91 {
  92         g_assert (handle == 0 || handle == mono_rand_provider);
  93 }
  94 #endif /* HOST_WIN32 */