Issue #27278: Fix os.urandom() implementation using getrandom() on Linux.
Truncate size to INT_MAX and loop until we collected enough random bytes,
instead of casting a directly Py_ssize_t to int.
Issue #26839: On Linux, os.urandom() now calls getrandom() with GRND_NONBLOCK
to fall back on reading /dev/urandom if the urandom entropy pool is not
initialized yet. Patch written by Colm Buckley.
Issue #26735: Fix os.urandom() on Solaris 11.3 and newer when reading more than
1,024 bytes: call getrandom() multiple times with a limit of 1024 bytes per
call.
function instead of the getentropy() function. The getentropy() function is
blocking to generate very good quality entropy, os.urandom() doesn't need such
high-quality entropy.
See the latest version of getrandom() manual page:
http://man7.org/linux/man-pages/man2/getrandom.2.html#NOTES
The behavior when a call to getrandom() that is blocked while reading from
/dev/urandom is interrupted by a signal handler depends on the
initialization state of the entropy buffer and on the request size, buflen.
If the entropy is not yet initialized, then the call will fail with the
EINTR error. If the entropy pool has been initialized and the request size
is large (buflen > 256), the call either succeeds, returning a partially
filled buffer, or fails with the error EINTR. If the entropy pool has been
initialized and the request size is small (buflen <= 256), then getrandom()
will not fail with EINTR. Instead, it will return all of the bytes that
have been requested.
Note: py_getrandom() calls getrandom() with flags=0.
