g10: Prefer keys requiring no further user interaction.

* g10/call-agent.c (agent_set_pinentry_mode): New function.
(start_agent): Use new function.
* g10/call-agent.h (agent_set_pinentry_mode): New prototype.
* g10/gpgv.c (agent_set_pinentry_mode): New stub.
* g10/mainproc.c (proc_packets): Try with PINENTRY_MODE_CANCEL first.
(proc_encryption_packets): Likewise.
* g10/test-stubs.c (agent_set_pinentry_mode): New stub.
* tests/openpgp/Makefile.am (TESTS): Add new test.
* tests/openpgp/issue1955.scm: New file.

GnuPG-bug-id: 1955
Signed-off-by: Justus Winter <justus@g10code.com>

g10/call-agent.c

@@ -285,6 +285,44 @@ warn_version_mismatch (assuan_context_t ctx, const char *servername, int mode)
   return err;
 }
 
+int
+agent_set_pinentry_mode (int pinentry_mode, int *old_mode)
+{
+  int rc;
+  char *tmp;
+
+  if (agent_ctx == NULL)
+    {
+      if (old_mode)
+        *old_mode = opt.pinentry_mode;
+
+      opt.pinentry_mode = pinentry_mode;
+      return 0;
+    }
+
+  tmp = xasprintf ("OPTION pinentry-mode=%s",
+                   str_pinentry_mode (pinentry_mode));
+  rc = assuan_transact (agent_ctx, tmp,
+                        NULL, NULL, NULL, NULL, NULL, NULL);
+  xfree (tmp);
+  if (rc)
+    {
+      log_error ("setting pinentry mode '%s' failed: %s\n",
+                 str_pinentry_mode (pinentry_mode),
+                 gpg_strerror (rc));
+      write_status_error ("set_pinentry_mode", rc);
+    }
+  else
+    {
+      if (old_mode)
+        *old_mode = opt.pinentry_mode;
+
+      opt.pinentry_mode = pinentry_mode;
+    }
+
+  return rc;
+}
+
 
 /* Try to connect to the agent via socket or fork it off and work by
    pipes.  Handle the server's initial greeting */
@@ -332,21 +370,7 @@ start_agent (ctrl_t ctrl, int for_card)
                            NULL, NULL, NULL, NULL, NULL, NULL);
           /* Pass on the pinentry mode.  */
           if (opt.pinentry_mode)
-            {
-              char *tmp = xasprintf ("OPTION pinentry-mode=%s",
-                                     str_pinentry_mode (opt.pinentry_mode));
-              rc = assuan_transact (agent_ctx, tmp,
-                               NULL, NULL, NULL, NULL, NULL, NULL);
-              xfree (tmp);
-              if (rc)
-                {
-                  log_error ("setting pinentry mode '%s' failed: %s\n",
-                             str_pinentry_mode (opt.pinentry_mode),
-                             gpg_strerror (rc));
-                  write_status_error ("set_pinentry_mode", rc);
-                }
-            }
-
+            agent_set_pinentry_mode (opt.pinentry_mode, NULL);
           check_hijacking (agent_ctx);
         }
     }

g10/call-agent.h

@@ -123,6 +123,8 @@ int agent_scd_checkpin  (const char *serialno);
 /* Dummy function, only implemented by gpg 1.4. */
 void agent_clear_pin_cache (const char *sn);
 
+/* XXX */
+int agent_set_pinentry_mode (int pinentry_mode, int *old_mode);
 
 /* Send the GET_PASSPHRASE command to the agent.  */
 gpg_error_t agent_get_passphrase (const char *cache_id,

g10/gpgv.c

@@ -697,3 +697,8 @@ void
 tofu_end_batch_update (void)
 {
 }
+
+int
+agent_set_pinentry_mode (int pinentry_mode, int *old_mode)
+{
+}

g10/mainproc.c

@@ -39,6 +39,8 @@
 #include "photoid.h"
 #include "mbox-util.h"
 #include "call-dirmngr.h"
+#include "call-agent.h"
+#include "../common/shareddefs.h"
 
 /* Put an upper limit on nested packets.  The 32 is an arbitrary
    value, a much lower should actually be sufficient.  */
@@ -1174,13 +1176,19 @@ int
 proc_packets (ctrl_t ctrl, void *anchor, iobuf_t a )
 {
   int rc;
+  int old_mode;
   CTX c = xmalloc_clear (sizeof *c);
 
   c->ctrl = ctrl;
   c->anchor = anchor;
-  rc = do_proc_packets (ctrl, c, a);
-  xfree (c);
 
+  agent_set_pinentry_mode (PINENTRY_MODE_CANCEL, &old_mode);
+  rc = do_proc_packets (ctrl, c, a);
+  agent_set_pinentry_mode (old_mode, NULL);
+  if (rc)
+    rc = do_proc_packets (ctrl, c, a);
+
+  xfree (c);
   return rc;
 }
 
@@ -1272,12 +1280,19 @@ int
 proc_encryption_packets (ctrl_t ctrl, void *anchor, iobuf_t a )
 {
   CTX c = xmalloc_clear (sizeof *c);
+  int old_mode;
   int rc;
 
   c->ctrl = ctrl;
   c->anchor = anchor;
   c->encrypt_only = 1;
+
+  agent_set_pinentry_mode (PINENTRY_MODE_CANCEL, &old_mode);
   rc = do_proc_packets (ctrl, c, a);
+  agent_set_pinentry_mode (old_mode, NULL);
+  if (rc)
+    rc = do_proc_packets (ctrl, c, a);
+
   xfree (c);
   return rc;
 }

g10/test-stubs.c

@@ -505,3 +505,8 @@ void
 tofu_end_batch_update (void)
 {
 }
+
+int
+agent_set_pinentry_mode (int pinentry_mode, int *old_mode)
+{
+}

tests/openpgp/Makefile.am

@@ -82,6 +82,7 @@ TESTS = setup.scm \
 	default-key.scm \
 	export.scm \
 	ssh.scm \
+	issue1955.scm \
 	issue2015.scm \
 	finish.scm
 

tests/openpgp/issue1955.scm

@@ -0,0 +1,47 @@
+#!/usr/bin/env gpgscm
+
+;; Copyright (C) 2016 g10 Code GmbH
+;;
+;; This file is part of GnuPG.
+;;
+;; GnuPG is free software; you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation; either version 3 of the License, or
+;; (at your option) any later version.
+;;
+;; GnuPG is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;; GNU General Public License for more details.
+;;
+;; You should have received a copy of the GNU General Public License
+;; along with this program; if not, see <http://www.gnu.org/licenses/>.
+
+(load (with-path "defs.scm"))
+
+(lettmp
+ (logfile)
+
+ (define (dump logfile)
+   (call-with-input-file logfile
+     (lambda (port)
+       (display (read-all port)))))
+
+ (setenv "PINENTRY_USER_DATA"
+	 (string-append "--logfile=" logfile " " usrpass1) #t)
+
+ (echo "Killing gpg-agent...")
+ (call-check `(,(tool 'gpg-connect-agent) --verbose killagent /bye))
+ (echo "Starting gpg-agent...")
+ (call-check `(,(tool 'gpg-connect-agent) --verbose /bye))
+
+ (for-each-p
+  "Checking that keys requiring no interactions are preferred (issue1955)..."
+  (lambda (test)
+    (let ((file (in-srcdir "samplemsgs"
+			   (string-append "issue1955." test ".gpg"))))
+      (assert
+       (string-contains? (call-check `(,@GPG --decrypt ,file)) "geheim"))
+      (if (file-exists? logfile)
+	  (error "GnuPG used the key requiring a passphrase"))))
+  '("one.two" "two.one")))