scd:p15: Support signing with CardOS 5 cards.

* scd/app-help.c (app_help_get_keygrip_string_pk): Add optional arg
r_pkey and change all callers.
(app_help_get_keygrip_string): Ditto.
* scd/app-p15.c (struct cdf_object_s): Use bit flags
(struct aodf_object_s): Ditto.  Add field 'fid'.
(struct prkdf_object_s): Ditto.  Add fields keygrip, keyalgo, and
keynbits.
(parse_certid): Allow a keygrip instead of a certid aka keyref.
(read_ef_aodf): Store the FID.
(keygripstr_from_prkdf): Rename to ...
(keygrip_from_prkdf): this.  Remove arg r_gripstr and implement cache.
Change callers to directly use the values from the object.  Also store
the algo and length of the key ion the object.
(keyref_from_keyinfo): New. Factored out code.
(do_sign): Support SHA-256 and >2048 bit RSA keys.
common/scd:p15: Support signing with CardOS 5 cards.
* common/util.h (KEYGRIP_LEN): New.
--

This has been tested with a D-Trust card featuring 3072 bit keys.
Note that non-repudiation key for a qualified signature does not yet
work because we do not yet support rsaPSS padding.  Thus a gpgsm
--learn shows a couple of Bad Signature errors for this key.

Signed-off-by: Werner Koch <wk@gnupg.org>

Back ported from master:
- Removed do_with_keygrip
- Added KEYGRIP_LEN
- app_help_get_keygrip_string_pk actually added.
- Move keygrip_from_prkdf in do_sign before the verification.
  It used to work in master only because there it is implictly
  called prior to signing by do_with_keygrip

Signed-off-by: Werner Koch <wk@gnupg.org>

common/util.h

@@ -66,6 +66,11 @@
 /* Hash function used with libksba. */
 #define HASH_FNC ((void (*)(void *, const void*,size_t))gcry_md_write)
 
+/* The length of the keygrip.  This is a SHA-1 hash of the key
+ * parameters as generated by gcry_pk_get_keygrip.  */
+#define KEYGRIP_LEN 20
+
+
 /* Get all the stuff from jnlib. */
 #include "../common/logging.h"
 #include "../common/argparse.h"