[RFC PATCH] enable configurable SECMEM_BUFFER_SIZE

[Shah, Amul]

From: Werner Koch [mailto:wk at gnupg.org] Sent: Friday, November 24, 2017 11:00 AM
>
>On Thu, 23 Nov 2017 10:43, Amul.Shah at fisglobal.com said:
>
>> but xmalloc allocations can use the overflow pool(s). This means that
>> every xmalloc allocation consumes the limited main pool. Once the
>> mainpool is exhausted, xmalloc allocations continue, but secure mallocs stop.
>
>To clarify: that is xmalloc_secure.  I meanwhile implemented a Libgcrypt
>feature to allow expanding the secmem pool.  It is also possible to advice
>Libcgrypt on the size of the newly allocated pools.  The latter can be
>important because all calls to free need to check whether that free is affects
>the secmem pool - this is done by comparing the tagnges of all secmem pools -
>many pools obviously take a little bit longer.
>
>gpg-agent has a new option --auto-expand-secmem to enable this features.
>This is currently in the 2.2 branch but will soon be merged into master.

[amul:3] Awesome! And thanks for the explanation.

>ENOMEM does not mean it is not possible to allocate more memory.  It should
>always been viewed as a temporary error code.  Right a different error code
>would be useful but has the disadvantgae that all ENOMEM handling code needs
>to be adjusted.  With the auto-expand-secmem feature any ENOMEM will anyway be
>a "real" ENOMEM.

[amul:3] I never considered ENOMEM as a transient error. Something new to think about.


>> [amul:2] I updated the bug with the test script that I used to expose the problem.
>
>Thanks.  All as been pushed and a Libgcrypt 1.8.2 release can be done soonish.
>GnuPG 2.2.4 needs to wait a few weeks.

[amul:3] DKG, What does one need to do to back-port these changes to stable?
File a bug, attach patches that apply cleanly to the target sources and request
the maintainer to add them?
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