gpg: Allow decryption w/o public key but with correct card inserted.

* agent/command.c (cmd_readkey): Add option --no-data and special
handling for $SIGNKEYID and $AUTHKEYID.
* g10/call-agent.c (agent_scd_getattr): Create shadow keys for KEY-FPR
output.
* g10/skclist.c (enum_secret_keys): Automagically get a missing public
key for the current card.

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

1 files changed, 41 insertions, 0 deletions

diff --git a/g10/skclist.c b/g10/skclist.c
index c9f7d126a..f9647cc1d 100644
--- a/g10/skclist.c
+++ b/g10/skclist.c
@@ -31,6 +31,7 @@
 #include "keydb.h"
 #include "../common/util.h"
 #include "../common/i18n.h"
+#include "keyserver-internal.h"
 #include "call-agent.h"
 
 
@@ -322,11 +323,13 @@ enum_secret_keys (ctrl_t ctrl, void **context, PKT_public_key *sk)
 {
   gpg_error_t err = 0;
   const char *name;
+  int cardkey;
   kbnode_t keyblock;
   struct
   {
     int eof;
     int state;
+    int cardkey_done;
     strlist_t sl;
     keypair_info_t card_keyinfo;
     keypair_info_t card_keyinfo_list;
@@ -381,6 +384,7 @@ enum_secret_keys (ctrl_t ctrl, void **context, PKT_public_key *sk)
           do
             {
               name = NULL;
+              cardkey = 0;
               keyblock = NULL;
               switch (c->state)
                 {
@@ -431,6 +435,7 @@ enum_secret_keys (ctrl_t ctrl, void **context, PKT_public_key *sk)
                         c->fpr2[i] = *s;
                       c->fpr2[i] = 0;
                       name = c->fpr2;
+                      cardkey = 1;
 
                       c->card_keyinfo = c->card_keyinfo->next;
                     }
@@ -482,11 +487,47 @@ enum_secret_keys (ctrl_t ctrl, void **context, PKT_public_key *sk)
               err = getkey_byname (ctrl, NULL, NULL, name, 1, &c->keyblock);
               if (err)
                 {
+                  struct agent_card_info_s cinfo = { 0 };
+
                   /* getkey_byname might return a keyblock even in the
                      error case - I have not checked.  Thus better release
                      it.  */
                   release_kbnode (c->keyblock);
                   c->keyblock = NULL;
+                  /* If this was a card key we might not yet have the
+                   * public key for it.  Thus check whether the card
+                   * can return the fingerprint of the encryption key
+                   * and we can then find the public key via LDAP.  */
+                  if (cardkey && !c->cardkey_done
+                      && gpg_err_code (err) == GPG_ERR_NO_SECKEY
+                      && !agent_scd_getattr ("KEY-FPR", &cinfo)
+                      && cinfo.fpr2len)
+                    {
+                      /* Note that this code does not handle the case
+                       * for two readers having both openpgp
+                       * encryption keys. only one will be tried.  */
+                      c->cardkey_done = 1;
+                      if (opt.debug)
+                        log_debug ("using LDAP to find public key"
+                                   " for current card\n");
+                      if (!keyserver_import_fprint
+                          (ctrl, cinfo.fpr2, cinfo.fpr2len, opt.keyserver,
+                           KEYSERVER_IMPORT_FLAG_LDAP))
+                        {
+                          char fpr_string[MAX_FINGERPRINT_LEN * 2 + 1];
+
+                          bin2hex (cinfo.fpr2, cinfo.fpr2len, fpr_string);
+                          err = getkey_byname (ctrl, NULL, NULL, fpr_string, 1,
+                                               &c->keyblock);
+                          if (err)
+                            {
+                              release_kbnode (c->keyblock);
+                              c->keyblock = NULL;
+                            }
+                          else
+                            c->node = c->keyblock;
+                        }
+                    }
                 }
               else
                 c->node = c->keyblock;