gpg: Use ephemeral mode for generating card keys.

* g10/call-agent.c (agent_set_ephemeral_mode): New.
* g10/keyedit.c (keyedit_menu) <bkuptocard>: Switch to ephemeral mode.
* g10/keygen.c (do_generate_keypair): Switch to ephemeral mode for
card keys with backup.
--

GnuPG-bug-id: 6944

4 files changed, 104 insertions, 19 deletions

diff --git a/g10/call-agent.c b/g10/call-agent.c
index 744c0fcb8..daf12fae7 100644
--- a/g10/call-agent.c
+++ b/g10/call-agent.c
@@ -3243,6 +3243,45 @@ agent_passwd (ctrl_t ctrl, const char *hexkeygrip, const char *desc, int verify,
 }
 
 
+/* Enable or disable the ephemeral mode.  In ephemeral mode keys are
+ * created,searched and used in a per-session key store and not in the
+ * on-disk file.  Set ENABLE to 1 to enable this mode, to 0 to disable
+ * this mode and to -1 to only query the current mode.  If R_PREVIOUS
+ * is given the previously used state of the ephemeral mode is stored
+ * at that address.  */
+gpg_error_t
+agent_set_ephemeral_mode (ctrl_t ctrl, int enable, int *r_previous)
+{
+  gpg_error_t err;
+
+  err = start_agent (ctrl, 0);
+  if (err)
+    goto leave;
+
+  if (r_previous)
+    {
+      err = assuan_transact (agent_ctx, "GETINFO ephemeral",
+                             NULL, NULL, NULL, NULL, NULL, NULL);
+      if (!err)
+        *r_previous = 1;
+      else if (gpg_err_code (err) == GPG_ERR_FALSE)
+        *r_previous = 0;
+      else
+        goto leave;
+    }
+
+  /* Skip setting if we are only querying or if the mode is already set. */
+  if (enable == -1 || (r_previous && !!*r_previous == !!enable))
+    err = 0;
+  else
+    err = assuan_transact (agent_ctx,
+                           enable? "OPTION ephemeral=1" : "OPTION ephemeral=0",
+                           NULL, NULL, NULL, NULL, NULL, NULL);
+ leave:
+  return err;
+}
+
+
 /* Return the version reported by gpg-agent.  */
 gpg_error_t
 agent_get_version (ctrl_t ctrl, char **r_version)
diff --git a/g10/call-agent.h b/g10/call-agent.h
index 45af95422..1e72dc03f 100644
--- a/g10/call-agent.h
+++ b/g10/call-agent.h
@@ -247,6 +247,10 @@ gpg_error_t agent_delete_key (ctrl_t ctrl, const char *hexkeygrip,
 gpg_error_t agent_passwd (ctrl_t ctrl, const char *hexkeygrip, const char *desc,
                           int verify,
                           char **cache_nonce_addr, char **passwd_nonce_addr);
+
+/* Set or get the ephemeral mode.  */
+gpg_error_t agent_set_ephemeral_mode (ctrl_t ctrl, int enable, int *r_previous);
+
 /* Get the version reported by gpg-agent.  */
 gpg_error_t agent_get_version (ctrl_t ctrl, char **r_version);
 
diff --git a/g10/keyedit.c b/g10/keyedit.c
index a12546f71..cae0f7841 100644
--- a/g10/keyedit.c
+++ b/g10/keyedit.c
@@ -1905,6 +1905,7 @@ keyedit_menu (ctrl_t ctrl, const char *username, strlist_t locusr,
 	    PACKET *pkt;
 	    IOBUF a;
             struct parse_packet_ctx_s parsectx;
+            int lastmode;
 
             if (!*arg_string)
 	      {
@@ -1959,17 +1960,28 @@ keyedit_menu (ctrl_t ctrl, const char *username, strlist_t locusr,
 	    xfree (fname);
 	    node = new_kbnode (pkt);
 
-            /* Transfer it to gpg-agent which handles secret keys.  */
-            err = transfer_secret_keys (ctrl, NULL, node, 1, 1, 0);
-
-            /* Treat the pkt as a public key.  */
-            pkt->pkttype = PKT_PUBLIC_KEY;
-
-            /* Ask gpg-agent to store the secret key to card.  */
-            if (card_store_subkey (node, 0, NULL))
+            err = agent_set_ephemeral_mode (ctrl, 1, &lastmode);
+            if (err)
+              log_error ("error switching to ephemeral mode: %s\n",
+                         gpg_strerror (err));
+            else
               {
-                redisplay = 1;
-                sec_shadowing = 1;
+                /* Transfer it to gpg-agent which handles secret keys.  */
+                err = transfer_secret_keys (ctrl, NULL, node, 1, 1, 0);
+                if (!err)
+                  {
+                    /* Treat the pkt as a public key.  */
+                    pkt->pkttype = PKT_PUBLIC_KEY;
+
+                    /* Ask gpg-agent to store the secret key to card.  */
+                    if (card_store_subkey (node, 0, NULL))
+                      {
+                        redisplay = 1;
+                        sec_shadowing = 1;
+                      }
+                  }
+                if (!lastmode && agent_set_ephemeral_mode (ctrl, 0, NULL))
+                  log_error ("error clearing the ephemeral mode\n");
               }
             release_kbnode (node);
           }
diff --git a/g10/keygen.c b/g10/keygen.c
index 886c3b007..b263a47de 100644
--- a/g10/keygen.c
+++ b/g10/keygen.c
@@ -5754,7 +5754,6 @@ do_generate_keypair (ctrl_t ctrl, struct para_data_s *para,
 
   if (!err && get_parameter (para, pSUBKEYTYPE))
     {
-      const char *cardbackupkey = NULL;
       int subkey_algo = get_parameter_algo (ctrl, para, pSUBKEYTYPE, NULL);
 
       key_from_hexgrip = get_parameter_value (para, pSUBKEYGRIP);
@@ -5769,22 +5768,57 @@ do_generate_keypair (ctrl_t ctrl, struct para_data_s *para,
                                       pub_root, subkeytimestamp,
                                       get_parameter_u32 (para, pSUBKEYEXPIRE),
                                       1, &keygen_flags);
-      else if (!card
-               || (cardbackupkey = get_parameter_value (para, pCARDBACKUPKEY)))
+      else if (get_parameter_value (para, pCARDBACKUPKEY))
         {
+          int lastmode;
           unsigned int mykeygenflags = KEYGEN_FLAG_NO_PROTECTION;
 
+          err = agent_set_ephemeral_mode (ctrl, 1, &lastmode);
+          if (err)
+            log_error ("error switching to ephemeral mode: %s\n",
+                       gpg_strerror (err));
+          else
+            {
+              err = do_create (subkey_algo,
+                               get_parameter_uint (para, pSUBKEYLENGTH),
+                               get_parameter_value (para, pSUBKEYCURVE),
+                               pub_root,
+                               subkeytimestamp,
+                               get_parameter_u32 (para, pSUBKEYEXPIRE), 1,
+                               &mykeygenflags,
+                               get_parameter_passphrase (para),
+                               &cache_nonce, NULL,
+                               NULL, NULL);
+              /* Get the pointer to the generated public subkey packet.  */
+              if (!err)
+                {
+                  kbnode_t node;
+
+                  for (node = pub_root; node; node = node->next)
+                    if (node->pkt->pkttype == PKT_PUBLIC_SUBKEY)
+                      sub_psk = node->pkt->pkt.public_key;
+                  log_assert (sub_psk);
+                  err = card_store_key_with_backup (ctrl,
+                                                    sub_psk, gnupg_homedir ());
+                }
+
+              /* Reset the ephemeral mode as needed.  */
+              if (!lastmode && agent_set_ephemeral_mode (ctrl, 0, NULL))
+                log_error ("error clearing the ephemeral mode\n");
+            }
+        }
+      else if (!card)
+        {
           err = do_create (subkey_algo,
                            get_parameter_uint (para, pSUBKEYLENGTH),
                            get_parameter_value (para, pSUBKEYCURVE),
                            pub_root,
                            subkeytimestamp,
                            get_parameter_u32 (para, pSUBKEYEXPIRE), 1,
-                           cardbackupkey? &mykeygenflags : &keygen_flags,
+                           &keygen_flags,
                            get_parameter_passphrase (para),
                            &cache_nonce, NULL,
                            NULL, NULL);
-          /* Get the pointer to the generated public subkey packet.  */
           if (!err)
             {
               kbnode_t node;
@@ -5793,10 +5827,6 @@ do_generate_keypair (ctrl_t ctrl, struct para_data_s *para,
                 if (node->pkt->pkttype == PKT_PUBLIC_SUBKEY)
                   sub_psk = node->pkt->pkt.public_key;
               log_assert (sub_psk);
-
-              if (cardbackupkey)
-                err = card_store_key_with_backup (ctrl,
-                                                  sub_psk, gnupg_homedir ());
             }
         }
       else