[issue26839] Python 3.5 running on Linux kernel 3.17+ can block at startup or on importing the random module on getrandom()

[Christian Heimes]

Christian Heimes added the comment:

On 2016-06-07 19:36, Donald Stufft wrote:
> 
> Donald Stufft added the comment:
> 
>> Possible resolutions:
>>  * accept possible low-entropy initialization of the hash secret; using the patches supplied here by myself and Victor.
>>  * add a command-line flag to disable "strong" initialization of the hash secret (or revive the old -R flag).
>>  * simply require user-space workarounds like setting PYTHONHASHSEED
> 
> I think either the first or second here are good solutions, the third is kind of crummy on it's own because it's not always possible to pass in an environment variable. Pairing the third with a CLI flag option might work out nice though, perhaps a -XPYTHONHASHSEED=(random/int()) or something. Then folks who are in early boot can easily just hardcode a hash seed, removing the need to hit the entropy pools while still maintaining strong random for everyone else.
> 
> So I guess I would lean towards adding a CLI flag, but just allowing SipHash to fall back to possibly bad randomness for it's initialization is OK.

I don't like the fact that applications can fall back to insecure RNG
without user involvement or warning.

Therefore I'm in favor of a command line argument that allows pyhash.c
to fall back to a less secure RNG. System scripts must use the -I option
(isolated mode without user-site dir and PY* env vars) anyway. The new
option would enable less secure RNG as fallback and -I.

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<http://bugs.python.org/issue26839>
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