scd:piv: Implement PIN cache.

* scd/command.c (pincache_put): Add arg pinlen and change all callers
to provide it.
* scd/app-piv.c (cache_pin): New.
(pin_from_cache): New.
(ask_and_prepare_chv): Add args no_cache and r_unpaddedpinlen.  Take
PIN from the cache.  Return the unpadded length.
(verify_chv): Add arg ctrl.  Cache the PIN.
(do_change_chv): Clear PIN cache.
--

The PIV pins are padded but we want to store the unpadded PIN.  Thus
the changes to the function.

Code has has been tested by commenting the no_cache parameter because
we the current test certificate was created for PIV.9C which requires
a verification for each use.  More testing is required.

GnuPG-bug-id: 4791
Signed-off-by: Werner Koch <wk@gnupg.org>

1 files changed, 3 insertions, 4 deletions

diff --git a/scd/command.c b/scd/command.c
index 5dc0ef6a5..46c879e6b 100644
--- a/scd/command.c
+++ b/scd/command.c
@@ -2333,7 +2333,7 @@ set_key_for_pincache (gcry_cipher_hd_t hd)
  * gpg-agent cache it because it is better suited for this.  */
 void
 pincache_put (ctrl_t ctrl, int slot, const char *appname, const char *pinref,
-              const char *pin)
+              const char *pin, unsigned int pinlen)
 {
   gpg_error_t err;
   assuan_context_t ctx;
@@ -2341,7 +2341,7 @@ pincache_put (ctrl_t ctrl, int slot, const char *appname, const char *pinref,
   gcry_cipher_hd_t cipherhd = NULL;
   char *pinbuf = NULL;
   unsigned char *wrappedkey = NULL;
-  size_t pinlen, pinbuflen, wrappedkeylen;
+  size_t pinbuflen, wrappedkeylen;
 
   if (!ctrl)
     {
@@ -2365,7 +2365,7 @@ pincache_put (ctrl_t ctrl, int slot, const char *appname, const char *pinref,
 
   if (!ctrl || !ctrl->server_local || !(ctx=ctrl->server_local->assuan_ctx))
     return;
-  if (pin && !*pin)
+  if (pin && !pinlen)
     return;  /* Ignore an empty PIN.  */
 
   snprintf (line, sizeof line, "%d/%s/%s ",
@@ -2378,7 +2378,6 @@ pincache_put (ctrl_t ctrl, int slot, const char *appname, const char *pinref,
     {
       /* FIXME: Replace this by OCB mode and use the cache key as
        * additional data.  */
-      pinlen = strlen (pin);
       /* Pad with zeroes (AESWRAP requires multiples of 64 bit but
        * at least 128 bit data).  */
       pinbuflen = pinlen + 8 - (pinlen % 8);