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Don't use getentropy() on Linux

Issue #29188: Support glibc 2.24 on Linux: don't use getentropy() function but
read from /dev/urandom to get random bytes, for example in os.urandom().  On
Linux, getentropy() is implemented which getrandom() is blocking mode, whereas
os.urandom() should not block.
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vstinner committed Jan 9, 2017
1 parent 98b1c82 commit 01bdbad3e951014c58581635b94b22868537901c
Showing with 14 additions and 2 deletions.
  1. +5 −0 Misc/NEWS
  2. +9 −2 Python/random.c
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@@ -23,6 +23,11 @@ Extension Modules
Library
-------
- Issue #29188: Support glibc 2.24 on Linux: don't use getentropy() function
but read from /dev/urandom to get random bytes, for example in os.urandom().
On Linux, getentropy() is implemented which getrandom() is blocking mode,
whereas os.urandom() should not block.
- Issue #29142: In urllib, suffixes in no_proxy environment variable with
leading dots could match related hostnames again (e.g. .b.c matches a.b.c).
Patch by Milan Oberkirch.
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@@ -97,8 +97,15 @@ win32_urandom(unsigned char *buffer, Py_ssize_t size, int raise)
}
/* Issue #25003: Don't use getentropy() on Solaris (available since
* Solaris 11.3), it is blocking whereas os.urandom() should not block. */
#elif defined(HAVE_GETENTROPY) && !defined(sun)
Solaris 11.3), it is blocking whereas os.urandom() should not block.
Issue #29188: Don't use getentropy() on Linux since the glibc 2.24
implements it with the getrandom() syscall which can fail with ENOSYS,
and this error is not supported in py_getentropy() and getrandom() is called
with flags=0 which blocks until system urandom is initialized, which is not
the desired behaviour to seed the Python hash secret nor for os.urandom():
see the PEP 524 which was only implemented in Python 3.6. */
#elif defined(HAVE_GETENTROPY) && !defined(sun) && !defined(linux)
#define PY_GETENTROPY 1
/* Fill buffer with size pseudo-random bytes generated by getentropy().

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