On 12/5/2017 11:54 AM, Richard Gray wrote:
>>> On Fri, 17 Nov 2017, Daniel Stenberg wrote:
>>>
>>>> Nowadays though. Is anything or anyone using this feature (disabling
>>>> CURL_GLOBAL_SSL) for a good purpose and if so, can you please
>>>> elaborate on
>>>> why and how? (I don't think "I won't use any TLS protocols" is a good
>>>> reason.)
>
> Just to belatedly chime in, I think the usage case where TLS is not
> wanted would be a LOCAL area network where an application is talking
> to a bunch of dumb devices.  Perhaps some sort of lab with a bunch of
> sensors with embedded controllers being polled by a smarter host of
> some sort.  It might even be reporting across a wide area network and
> want SSL for that, so it would have a secure/insecure mix.  I don't
> see this as being too much of a problem for a libcurl-using app as
> long as it is not being repeatedly.  If the program is being
> respawned, or is invoking the curl utility, then there might be some
> significant overhead due to the repeated re-initializations of the
> crypto.
>
> This is the only 'burn' usage scenario I can think of.  It is not my
> current scenario, but as one who formerly did embedded things, I still
> tend to think small.  The unpreventable overhead of initializing an
> unneeded library seems non-trivial.   Maybe with current processors
> the overhead is negligible.   I'm not sure what the low end might look
> like these days.
>
> Otherwise, this is a completely reasonable thing to do.

Thanks for your perspective. libcurl may rely on the SSL library for
things that don't have to do with SSL such as random number generation.
Prior to 7.57 if libcurl built was built with SSL but the SSL library
wasn't initialized (ie no CURL_GLOBAL_SSL) that could cause a crash or
bad random number generation. One of our shared concerns is a developer
would see the CURL_GLOBAL_SSL flag and use it to shut off SSL thinking
exactly that they're not using HTTPS so they don't need SSL initialized,
when that may not be true.

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Received on 2017-12-05