pkcs12 import and other improvements

[Werner Koch]

Hi!

I have just commited a few changes to NewPG which allows to import a
private key from a PKCS-12 [1] file.  It is just a very basic import:

  There is some limited support to import a private key from a PCKS-12
  file.  Note, that this does only import the private key and not any
  certificates available in that file.  Assume that gpgsm has been
  installed in the defualt location, you should do this.
  
   /usr/local/lib/newpg/protect-tool --p12-import --store <file.p12>
  
  This require that the gpg-agent is running, alternative you may give
  the passphrase on the commandline using the option "-P <passphrase>"
  - however this is in general not a good idea.  If that key already
  exists, the protect-tool refuses to store it unless you use the
  option "--force".

Note that this is no in the recently released tarball.  I also fixed
some errors with the pinentry invocation.

As a side-effect you can use of the files agent/simple-pwquery.[ch] to
implement access to the pinentry via a running gpg-agent from your own
programs.  These files are more or less self-contained and
configurable in the header file.

Next to come: Passphrase changing and export of private keys in
PKCS-12 format.


Shalom-Salam,

   Werner


[1] You might want to read Peter Gutmanm's description of the sucked
PKCS-12 format at http://www.cs.auckland.ac.nz/~pgut001/pubs/pfx.html