[Pkg-gnupg-maint] Bug#739424: Bug#739424: gnupg dies with "gpg: out of secure memory [...]" since 1.4.16-1

[Werner Koch]

On Thu,  2 Oct 2014 19:24, dkg at fifthhorseman.net said:

> public key operations with this sort of material.  So the concern is
> just for people who hold large RSA secret keys.

That would be easy because those can easily use a configure option etc
to adjust things for them.

> If i understand it correctly, i think what changed in 1.4.16 was RSA
> blinding and resistance against the acoustic attacks.  Presumably this

Right, that is probably the reason.  We should have the same problem
with 2.x depending on the Libgcrypt versions.  gpg 2.x also reserves 32k
memory (gpgsm even only 16k).  However some details are different.

> The first variant adds a compile-time flag: ./configure
> --enable-large-rsa-keys, which defaults to off.  If it is present, then
> we allocate double the secmem (64KiB instead of 32KiB) and permit up to
> 8Kib RSA keys when doing --gen-key --batch (the upper limit on
> interactive key generation remains at 4Kib).

I am 100% fine with the first part of it.  The second part puts new
firewood up to the we-need-larger-keys campfire, thus I like to ask not
to do that.  Marc et al may still create larger keys if they really want
that.  I am pretty sure they know how to change it.

> The second variant adds a runtime flag: gpg --enable-large-rsa , which
> defaults to off.  If the flag is present at runtime, then the secmem is

I considered such an option several times in the past but it is tricky
as you noted: We can't allow to put it into the conf file because that
would but too much code at the risk of being run under elevated
privileges (for those systems which still require that for mlock).
Although I won't like it, setting a flag to allow large key generation
would be okay here.

We need this for gpg 2 as well.  However, it might be a better idea to
implement that via a global Libgcrypt configuration file.  gpg could
then take that secure memory value from that file (Libgcrypt 1.7).


Shalom-Salam,

   Werner

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