gpg: Check gpg-agent version before 2.1 migration.

* g10/call-agent.c, g10/call-agent.h (agent_get_version): New.
* g10/migrate.c (migrate_secring): Abort migration if
agent_get_version returns not at least 2.1.0

--
GnuPG-bug-id: 1718

On the first installation of GnuPG 2.1 it is likely that an
old gpg-agent is still running in the environment. In that
case the migration would fail.

Signed-off-by: Andre Heinecke <aheinecke@intevation.de>

1 files changed, 30 insertions, 0 deletions

diff --git a/g10/call-agent.c b/g10/call-agent.c
index 58f4a92c5..080df1867 100644
--- a/g10/call-agent.c
+++ b/g10/call-agent.c
@@ -2277,3 +2277,33 @@ agent_passwd (ctrl_t ctrl, const char *hexkeygrip, const char *desc,
                          cache_nonce_status_cb, &cn_parm);
   return err;
 }
+
+/* Return the version reported by gpg-agent.  */
+gpg_error_t
+agent_get_version (ctrl_t ctrl, char **r_version)
+{
+  gpg_error_t err;
+  membuf_t data;
+
+  err = start_agent (ctrl, 0);
+  if (err)
+    return err;
+
+  init_membuf (&data, 64);
+  err = assuan_transact (agent_ctx, "GETINFO version",
+                        membuf_data_cb, &data,
+                        NULL, NULL, NULL, NULL);
+  if (err)
+    {
+      xfree (get_membuf (&data, NULL));
+      *r_version = NULL;
+    }
+  else
+    {
+      put_membuf (&data, "", 1);
+      *r_version = get_membuf (&data, NULL);
+      if (!*r_version)
+        err = gpg_error_from_syserror ();
+    }
+  return err;
+}