Mailing List Archive: GnuPG: gcrypt

gcrypt initialization

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dkg at fifthhorseman

Oct 26, 2009, 3:14 PM

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gcrypt initialization

hey gcrypt folks--

I'm trying to understand the various phases of gcrypt initialization.

I've read the docs, but in some places they appear to be
self-contradictory about what calls are specifically allowed when.

As i understand it, the required order is:

A) gcry_control(GCRYCTL_SET_THREAD_CBS or GCRYCTL_FORCE_FIPS_MODE)

B) gcry_check_version()

C) gcry_control(<other commands>,...)

D) gcry_control(GCRYCTL_INITIALIZATION_FINISHED)

E) <actual use of the library>

When a gcry_control command says that it can "only be used during
initialization time" (e.g. GCRYCTL_ENABLE_M_GUARD), i believe that
means that it must be invoked during phase C, but other gcry_control
invocations can be invoked at any time (including after the library has
actually been used).

Is this correct? What am i missing?

Regards,

--dkg

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wk at gnupg

Oct 28, 2009, 6:35 AM

Post #2 of 3 (504 views)
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Re: gcrypt initialization [In reply to]

On Mon, 26 Oct 2009 23:14, dkg [at] fifthhorseman said:

> A) gcry_control(GCRYCTL_SET_THREAD_CBS or GCRYCTL_FORCE_FIPS_MODE)

The first is merely a handmade constructor and as such pretty special.

The second is:

@item GCRYCTL_FORCE_FIPS_MODE; Arguments: none
Running this command puts the library into FIPS mode. If the library is
already in FIPS mode, a self-test is triggered and thus the library will
be put into operational state. This command may be used before a call
to gcry_check_version and that is actually the recommended way to let an
[...]

and states that it may be used before gcry_check_version (between A and
B) to force gcrypt into fips mode.

> When a gcry_control command says that it can "only be used during
> initialization time" (e.g. GCRYCTL_ENABLE_M_GUARD), i believe that

Okay, the docs are not clear. I changed it to say "before
gcry_check_version".

Let me know if you find other unclear documentation.

Shalom-Salam,

Werner

--
Die Gedanken sind frei. Ausnahmen regelt ein Bundesgesetz.

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dkg at fifthhorseman

Oct 28, 2009, 7:59 AM

Post #3 of 3 (502 views)
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Re: gcrypt initialization [In reply to]

On 10/28/2009 09:35 AM, Werner Koch wrote:
> Okay, the docs are not clear. I changed it to say "before
> gcry_check_version".

Thanks, Werner.

> Let me know if you find other unclear documentation.

line 523 of gcrypt.texi appears to claim that the full set of
functionality allowed before gcry_check_version is
GCRYCTL_SET_THREAD_CBS. Maybe it should mention GCRYCTL_FORCE_FIPS_MODE
and GCRYCTL_ENABLE_M_GUARD and GCRYCTL_ANY_INITIALIZATION_P (and others?)

Alternately, if there really are valid phases of initialization, maybe
it'd be useful to define them (with more semantically-meaningful names
than my earlier "A,B,C"), and indicate which commands belong to which phase?

Another thing that might be useful to document is what the relationship
is between the other gcry_control() calls and
GCRYCTL_INITIALIZATION_FINISHED -- at the moment, it's unclear what the
consequences of GCRYCTL_INITIALIZATION_FINISHED are, other than
GCRYCTL_INITIALIZATION_FINISHED_P returning a different value, and the
library appears to work without that call. So why should a user bother
to issue GCRYCTL_INITIALIZATION_FINISHED?

Regards,

--dkg

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