text: #include "Python.h"
  #ifdef MS_WINDOWS
  #  include <windows.h>
  /* All sample MSDN wincrypt programs include the header below. It is at least
   * required with Min GW. */
  #  include <wincrypt.h>
  #else
  #  include <fcntl.h>
  #  ifdef HAVE_SYS_STAT_H
  #    include <sys/stat.h>
  #  endif
  #  ifdef HAVE_LINUX_RANDOM_H
  #    include <linux/random.h>
  #  endif
  #  if defined(HAVE_SYS_RANDOM_H) && (defined(HAVE_GETRANDOM) || defined(HAVE_GETENTROPY))
  #    include <sys/random.h>
  #  endif
  #  if !defined(HAVE_GETRANDOM) && defined(HAVE_GETRANDOM_SYSCALL)
  #    include <sys/syscall.h>
  #  endif
  #  ifdef _3DS
  #    include "3ds/result.h"
  #    include "3ds/services/ps.h"
  #    include "3ds/types.h"
  #  endif
  #endif
  
  #ifdef _Py_MEMORY_SANITIZER
  #  include <sanitizer/msan_interface.h>
  #endif
  
  #ifdef Py_DEBUG
  int _Py_HashSecret_Initialized = 0;
  #else
  static int _Py_HashSecret_Initialized = 0;
  #endif
  
  #ifdef MS_WINDOWS
  static HCRYPTPROV hCryptProv = 0;
  
  static int
  win32_urandom_init(int raise)
  {
      /* Acquire context */
      if (!CryptAcquireContext(&hCryptProv, NULL, NULL,
                               PROV_RSA_FULL, CRYPT_VERIFYCONTEXT))
          goto error;
  
      return 0;
  
  error:
      if (raise) {
          PyErr_SetFromWindowsErr(0);
      }
      return -1;
  }
  
  /* Fill buffer with size pseudo-random bytes generated by the Windows CryptoGen
     API. Return 0 on success, or raise an exception and return -1 on error. */
  static int
  win32_urandom(unsigned char *buffer, Py_ssize_t size, int raise)
  {
      Py_ssize_t chunk;
  
      if (hCryptProv == 0)
      {
          if (win32_urandom_init(raise) == -1) {
              return -1;
          }
      }
  
      while (size > 0)
      {
          chunk = size > INT_MAX ? INT_MAX : size;
          if (!CryptGenRandom(hCryptProv, (DWORD)chunk, buffer))
          {
              /* CryptGenRandom() failed */
              if (raise) {
                  PyErr_SetFromWindowsErr(0);
              }
              return -1;
          }
          buffer += chunk;
          size -= chunk;
      }
      return 0;
  }
  
  #else /* !MS_WINDOWS */
  
  #if defined(HAVE_GETRANDOM) || defined(HAVE_GETRANDOM_SYSCALL)
  #define PY_GETRANDOM 1
  
  /* Call getrandom() to get random bytes:
  
     - Return 1 on success
     - Return 0 if getrandom() is not available (failed with ENOSYS or EPERM),
       or if getrandom(GRND_NONBLOCK) failed with EAGAIN (system urandom not
       initialized yet) and raise=0.
     - Raise an exception (if raise is non-zero) and return -1 on error:
       if getrandom() failed with EINTR, raise is non-zero and the Python signal
       handler raised an exception, or if getrandom() failed with a different
       error.
  
     getrandom() is retried if it failed with EINTR: interrupted by a signal. */
  static int
  py_getrandom(void *buffer, Py_ssize_t size, int blocking, int raise)
  {
      /* Is getrandom() supported by the running kernel? Set to 0 if getrandom()
         failed with ENOSYS or EPERM. Need Linux kernel 3.17 or newer, or Solaris
         11.3 or newer */
      static int getrandom_works = 1;
      int flags;
      char *dest;
      long n;
  
      if (!getrandom_works) {
          return 0;
      }
  
      flags = blocking ? 0 : GRND_NONBLOCK;
      dest = buffer;
      while (0 < size) {
  #ifdef sun
          /* Issue #26735: On Solaris, getrandom() is limited to returning up
             to 1024 bytes. Call it multiple times if more bytes are
             requested. */
          n = Py_MIN(size, 1024);
  #else
          n = Py_MIN(size, LONG_MAX);
  #endif
  
          errno = 0;
  #ifdef HAVE_GETRANDOM
          if (raise) {
              Py_BEGIN_ALLOW_THREADS
              n = getrandom(dest, n, flags);
              Py_END_ALLOW_THREADS
          }
          else {
              n = getrandom(dest, n, flags);
          }
  #else
          /* On Linux, use the syscall() function because the GNU libc doesn't
             expose the Linux getrandom() syscall yet. See:
             https://sourceware.org/bugzilla/show_bug.cgi?id=17252 */
          if (raise) {
              Py_BEGIN_ALLOW_THREADS
              n = syscall(SYS_getrandom, dest, n, flags);
              Py_END_ALLOW_THREADS
          }
          else {
              n = syscall(SYS_getrandom, dest, n, flags);
          }
  #  ifdef _Py_MEMORY_SANITIZER
          if (n > 0) {
               __msan_unpoison(dest, n);
          }
  #  endif
  #endif
  
          if (n < 0) {
              /* ENOSYS: the syscall is not supported by the kernel.
                 EPERM: the syscall is blocked by a security policy (ex: SECCOMP)
                 or something else. */
              if (errno == ENOSYS || errno == EPERM) {
                  getrandom_works = 0;
                  return 0;
              }
  
              /* getrandom(GRND_NONBLOCK) fails with EAGAIN if the system urandom
                 is not initialiazed yet. For _PyRandom_Init(), we ignore the
                 error and fall back on reading /dev/urandom which never blocks,
                 even if the system urandom is not initialized yet:
                 see the PEP 524. */
              if (errno == EAGAIN && !raise && !blocking) {
                  return 0;
              }
  
              if (errno == EINTR) {
                  if (raise) {
                      if (PyErr_CheckSignals()) {
                          return -1;
                      }
                  }
  
                  /* retry getrandom() if it was interrupted by a signal */
                  continue;
              }
  
              if (raise) {
                  PyErr_SetFromErrno(PyExc_OSError);
              }
              return -1;
          }
  
          dest += n;
          size -= n;
      }
      return 1;
  }
  
  #elif defined(HAVE_GETENTROPY)
  #define PY_GETENTROPY 1
  
  /* Fill buffer with size pseudo-random bytes generated by getentropy():
  
     - Return 1 on success
     - Return 0 if getentropy() syscall is not available (failed with ENOSYS or
       EPERM).
     - Raise an exception (if raise is non-zero) and return -1 on error:
       if getentropy() failed with EINTR, raise is non-zero and the Python signal
       handler raised an exception, or if getentropy() failed with a different
       error.
  
     getentropy() is retried if it failed with EINTR: interrupted by a signal. */
  static int
  py_getentropy(char *buffer, Py_ssize_t size, int raise)
  {
      /* Is getentropy() supported by the running kernel? Set to 0 if
         getentropy() failed with ENOSYS or EPERM. */
      static int getentropy_works = 1;
  
      if (!getentropy_works) {
          return 0;
      }
  
      while (size > 0) {
          /* getentropy() is limited to returning up to 256 bytes. Call it
             multiple times if more bytes are requested. */
          Py_ssize_t len = Py_MIN(size, 256);
          int res;
  
          if (raise) {
              Py_BEGIN_ALLOW_THREADS
              res = getentropy(buffer, len);
              Py_END_ALLOW_THREADS
          }
          else {
              res = getentropy(buffer, len);
          }
  
          if (res < 0) {
              /* ENOSYS: the syscall is not supported by the running kernel.
                 EPERM: the syscall is blocked by a security policy (ex: SECCOMP)
                 or something else. */
              if (errno == ENOSYS || errno == EPERM) {
                  getentropy_works = 0;
                  return 0;
              }
  
              if (errno == EINTR) {
                  if (raise) {
                      if (PyErr_CheckSignals()) {
                          return -1;
                      }
                  }
  
                  /* retry getentropy() if it was interrupted by a signal */
                  continue;
              }
  
              if (raise) {
                  PyErr_SetFromErrno(PyExc_OSError);
              }
              return -1;
          }
  
          buffer += len;
          size -= len;
      }
      return 1;
  }
  #endif /* defined(HAVE_GETENTROPY) && !defined(sun) */
  
  #ifdef _3DS
  
  static int
  ctru_urandom_init(int raise)
  {
      Result res = 0;
  
      res = psInit();
      if (R_SUCCEEDED(res))
          return 0;
  
      if (raise)
          PyErr_SetString(PyExc_RuntimeError,
                          "3DS: Failed to get pxi:ps9 service handle.");
      else
          Py_FatalError("3DS: Failed to get pxi:ps9 service handle.");
  
      return -1;
  }
  
  static int
  ctru_urandom(unsigned char *buffer, Py_ssize_t size, int raise)
  {
      Result res = 0;
  
      if (!psGetSessionHandle())
          ctru_urandom_init(raise);
      
      res = PS_GenerateRandomBytes(buffer, size);
  
      psExit();
  
      if (R_SUCCEEDED(res))
          return 0;
      
      if (raise)
          PyErr_SetString(PyExc_RuntimeError,
                          "3DS: PS_GenerateRandomBytes failed.");
      else
          Py_FatalError("3DS: PS_GenerateRandomBytes failed.");
      
      return -1;
  }
  
  #endif
  
  
  static struct {
      int fd;
      dev_t st_dev;
      ino_t st_ino;
  } urandom_cache = { -1 };
  
  /* Read random bytes from the /dev/urandom device:
  
     - Return 0 on success
     - Raise an exception (if raise is non-zero) and return -1 on error
  
     Possible causes of errors:
  
     - open() failed with ENOENT, ENXIO, ENODEV, EACCES: the /dev/urandom device
       was not found. For example, it was removed manually or not exposed in a
       chroot or container.
     - open() failed with a different error
     - fstat() failed
     - read() failed or returned 0
  
     read() is retried if it failed with EINTR: interrupted by a signal.
  
     The file descriptor of the device is kept open between calls to avoid using
     many file descriptors when run in parallel from multiple threads:
     see the issue #18756.
  
     st_dev and st_ino fields of the file descriptor (from fstat()) are cached to
     check if the file descriptor was replaced by a different file (which is
     likely a bug in the application): see the issue #21207.
  
     If the file descriptor was closed or replaced, open a new file descriptor
     but don't close the old file descriptor: it probably points to something
     important for some third-party code. */
  static int
  dev_urandom(char *buffer, Py_ssize_t size, int raise)
  {
      int fd;
      Py_ssize_t n;
  
      if (raise) {
          struct _Py_stat_struct st;
          int fstat_result;
  
          if (urandom_cache.fd >= 0) {
              Py_BEGIN_ALLOW_THREADS
              fstat_result = _Py_fstat_noraise(urandom_cache.fd, &st);
              Py_END_ALLOW_THREADS
  
              /* Does the fd point to the same thing as before? (issue #21207) */
              if (fstat_result
                  || st.st_dev != urandom_cache.st_dev
                  || st.st_ino != urandom_cache.st_ino) {
                  /* Something changed: forget the cached fd (but don't close it,
                     since it probably points to something important for some
                     third-party code). */
                  urandom_cache.fd = -1;
              }
          }
          if (urandom_cache.fd >= 0)
              fd = urandom_cache.fd;
          else {
              fd = _Py_open("/dev/urandom", O_RDONLY);
              if (fd < 0) {
                  if (errno == ENOENT || errno == ENXIO ||
                      errno == ENODEV || errno == EACCES) {
                      PyErr_SetString(PyExc_NotImplementedError,
                                      "/dev/urandom (or equivalent) not found");
                  }
                  /* otherwise, keep the OSError exception raised by _Py_open() */
                  return -1;
              }
              if (urandom_cache.fd >= 0) {
                  /* urandom_fd was initialized by another thread while we were
                     not holding the GIL, keep it. */
                  close(fd);
                  fd = urandom_cache.fd;
              }
              else {
                  if (_Py_fstat(fd, &st)) {
                      close(fd);
                      return -1;
                  }
                  else {
                      urandom_cache.fd = fd;
                      urandom_cache.st_dev = st.st_dev;
                      urandom_cache.st_ino = st.st_ino;
                  }
              }
          }
  
          do {
              n = _Py_read(fd, buffer, (size_t)size);
              if (n == -1)
                  return -1;
              if (n == 0) {
                  PyErr_Format(PyExc_RuntimeError,
                          "Failed to read %zi bytes from /dev/urandom",
                          size);
                  return -1;
              }
  
              buffer += n;
              size -= n;
          } while (0 < size);
      }
      else {
          fd = _Py_open_noraise("/dev/urandom", O_RDONLY);
          if (fd < 0) {
              return -1;
          }
  
          while (0 < size)
          {
              do {
                  n = read(fd, buffer, (size_t)size);
              } while (n < 0 && errno == EINTR);
  
              if (n <= 0) {
                  /* stop on error or if read(size) returned 0 */
                  close(fd);
                  return -1;
              }
  
              buffer += n;
              size -= n;
          }
          close(fd);
      }
      return 0;
  }
  
  static void
  dev_urandom_close(void)
  {
      if (urandom_cache.fd >= 0) {
          close(urandom_cache.fd);
          urandom_cache.fd = -1;
      }
  }
  #endif /* !MS_WINDOWS */
  
  
  /* Fill buffer with pseudo-random bytes generated by a linear congruent
     generator (LCG):
  
         x(n+1) = (x(n) * 214013 + 2531011) % 2^32
  
     Use bits 23..16 of x(n) to generate a byte. */
  static void
  lcg_urandom(unsigned int x0, unsigned char *buffer, size_t size)
  {
      size_t index;
      unsigned int x;
  
      x = x0;
      for (index=0; index < size; index++) {
          x *= 214013;
          x += 2531011;
          /* modulo 2 ^ (8 * sizeof(int)) */
          buffer[index] = (x >> 16) & 0xff;
      }
  }
  
  /* Read random bytes:
  
     - Return 0 on success
     - Raise an exception (if raise is non-zero) and return -1 on error
  
     Used sources of entropy ordered by preference, preferred source first:
  
     - CryptGenRandom() on Windows
     - getrandom() function (ex: Linux and Solaris): call py_getrandom()
     - getentropy() function (ex: OpenBSD): call py_getentropy()
     - /dev/urandom device
  
     Read from the /dev/urandom device if getrandom() or getentropy() function
     is not available or does not work.
  
     Prefer getrandom() over getentropy() because getrandom() supports blocking
     and non-blocking mode: see the PEP 524. Python requires non-blocking RNG at
     startup to initialize its hash secret, but os.urandom() must block until the
     system urandom is initialized (at least on Linux 3.17 and newer).
  
     Prefer getrandom() and getentropy() over reading directly /dev/urandom
     because these functions don't need file descriptors and so avoid ENFILE or
     EMFILE errors (too many open files): see the issue #18756.
  
     Only the getrandom() function supports non-blocking mode.
  
     Only use RNG running in the kernel. They are more secure because it is
     harder to get the internal state of a RNG running in the kernel land than a
     RNG running in the user land. The kernel has a direct access to the hardware
     and has access to hardware RNG, they are used as entropy sources.
  
     Note: the OpenSSL RAND_pseudo_bytes() function does not automatically reseed
     its RNG on fork(), two child processes (with the same pid) generate the same
     random numbers: see issue #18747. Kernel RNGs don't have this issue,
     they have access to good quality entropy sources.
  
     If raise is zero:
  
     - Don't raise an exception on error
     - Don't call the Python signal handler (don't call PyErr_CheckSignals()) if
       a function fails with EINTR: retry directly the interrupted function
     - Don't release the GIL to call functions.
  */
  static int
  pyurandom(void *buffer, Py_ssize_t size, int blocking, int raise)
  {
  #if defined(PY_GETRANDOM) || defined(PY_GETENTROPY)
      int res;
  #endif
  
      if (size < 0) {
          if (raise) {
              PyErr_Format(PyExc_ValueError,
                           "negative argument not allowed");
          }
          return -1;
      }
  
      if (size == 0) {
          return 0;
      }
  
  #ifdef MS_WINDOWS
      return win32_urandom((unsigned char *)buffer, size, raise);
  #elif defined(_3DS)
      return ctru_urandom((unsigned char *)buffer, size, raise);
  #else
  
  #if defined(PY_GETRANDOM) || defined(PY_GETENTROPY)
  #ifdef PY_GETRANDOM
      res = py_getrandom(buffer, size, blocking, raise);
  #else
      res = py_getentropy(buffer, size, raise);
  #endif
      if (res < 0) {
          return -1;
      }
      if (res == 1) {
          return 0;
      }
      /* getrandom() or getentropy() function is not available: failed with
         ENOSYS or EPERM. Fall back on reading from /dev/urandom. */
  #endif
  
      return dev_urandom(buffer, size, raise);
  #endif
  }
  
  /* Fill buffer with size pseudo-random bytes from the operating system random
     number generator (RNG). It is suitable for most cryptographic purposes
     except long living private keys for asymmetric encryption.
  
     On Linux 3.17 and newer, the getrandom() syscall is used in blocking mode:
     block until the system urandom entropy pool is initialized (128 bits are
     collected by the kernel).
  
     Return 0 on success. Raise an exception and return -1 on error. */
  int
  _PyOS_URandom(void *buffer, Py_ssize_t size)
  {
      return pyurandom(buffer, size, 1, 1);
  }
  
  /* Fill buffer with size pseudo-random bytes from the operating system random
     number generator (RNG). It is not suitable for cryptographic purpose.
  
     On Linux 3.17 and newer (when getrandom() syscall is used), if the system
     urandom is not initialized yet, the function returns "weak" entropy read
     from /dev/urandom.
  
     Return 0 on success. Raise an exception and return -1 on error. */
  int
  _PyOS_URandomNonblock(void *buffer, Py_ssize_t size)
  {
      return pyurandom(buffer, size, 0, 1);
  }
  
  void
  _PyRandom_Init(void)
  {
      char *env;
      unsigned char *secret = (unsigned char *)&_Py_HashSecret.uc;
      Py_ssize_t secret_size = sizeof(_Py_HashSecret_t);
      Py_BUILD_ASSERT(sizeof(_Py_HashSecret_t) == sizeof(_Py_HashSecret.uc));
  
      if (_Py_HashSecret_Initialized)
          return;
      _Py_HashSecret_Initialized = 1;
  
      /*
        Hash randomization is enabled.  Generate a per-process secret,
        using PYTHONHASHSEED if provided.
      */
  
      env = Py_GETENV("PYTHONHASHSEED");
      if (env && *env != '\0' && strcmp(env, "random") != 0) {
          char *endptr = env;
          unsigned long seed;
          seed = strtoul(env, &endptr, 10);
          if (*endptr != '\0'
              || seed > 4294967295UL
              || (errno == ERANGE && seed == ULONG_MAX))
          {
              Py_FatalError("PYTHONHASHSEED must be \"random\" or an integer "
                            "in range [0; 4294967295]");
          }
          if (seed == 0) {
              /* disable the randomized hash */
              memset(secret, 0, secret_size);
              Py_HashRandomizationFlag = 0;
          }
          else {
              lcg_urandom(seed, secret, secret_size);
              Py_HashRandomizationFlag = 1;
          }
      }
      else {
          int res;
  
          /* _PyRandom_Init() is called very early in the Python initialization
             and so exceptions cannot be used (use raise=0).
  
             _PyRandom_Init() must not block Python initialization: call
             pyurandom() is non-blocking mode (blocking=0): see the PEP 524. */
          res = pyurandom(secret, secret_size, 0, 0);
          if (res < 0) {
              Py_FatalError("failed to get random numbers to initialize Python");
          }
          Py_HashRandomizationFlag = 1;
      }
  }
  
  void
  _PyRandom_Fini(void)
  {
  #ifdef MS_WINDOWS
      if (hCryptProv) {
          CryptReleaseContext(hCryptProv, 0);
          hCryptProv = 0;
      }
  #else
      dev_urandom_close();
  #endif
  }
  