gpg-agent: Use "pinentry-basic" as fallback.

* common/homedir.c (get_default_pinentry_name): New.
(gnupg_module_name): Use that for the default pinentry.
(gnupg_module_name_flush_some): New.
* agent/gpg-agent.c (agent_sighup_action): Flush some module names.
* agent/call-pinentry.c (start_pinentry): Do not modify
opt.pinentry_program.
--

The idea with this change is that under Windows we can install a
simple native Windows pinentry as "pinentry-basic" and a full GUI
version may then later install pinentry-gtk etc which would then
automatically be used.

Unfortunately installing another pinentry from a different package
would clobber the GnuPG core directory which is not nice.  To fix that
we would need to agree on standard installation directories for GUIs
to also look there.

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

agent/call-pinentry.c

@@ -205,6 +205,7 @@ static int
 start_pinentry (ctrl_t ctrl)
 {
   int rc = 0;
+  const char *full_pgmname;
   const char *pgmname;
   assuan_context_t ctx;
   const char *argv[5];
@@ -257,11 +258,11 @@ start_pinentry (ctrl_t ctrl)
 #endif
     }
 
-  if (!opt.pinentry_program || !*opt.pinentry_program)
+  full_pgmname = opt.pinentry_program;
-    opt.pinentry_program = gnupg_module_name (GNUPG_MODULE_NAME_PINENTRY);
+  if (!full_pgmname || !*full_pgmname)
-  pgmname = opt.pinentry_program;
+    full_pgmname = gnupg_module_name (GNUPG_MODULE_NAME_PINENTRY);
-  if ( !(pgmname = strrchr (opt.pinentry_program, '/')))
+  if ( !(pgmname = strrchr (full_pgmname, '/')))
-    pgmname = opt.pinentry_program;
+    pgmname = full_pgmname;
   else
     pgmname++;
 
@@ -269,7 +270,7 @@ start_pinentry (ctrl_t ctrl)
      the resource bundle.  For other systems we stick to the usual
      convention of supplying only the name of the program.  */
 #ifdef __APPLE__
-  argv[0] = opt.pinentry_program;
+  argv[0] = full_pgmname;
 #else /*!__APPLE__*/
   argv[0] = pgmname;
 #endif /*__APPLE__*/
@@ -310,13 +311,13 @@ start_pinentry (ctrl_t ctrl)
      that atfork is used to change the environment for pinentry.  We
      start the server in detached mode to suppress the console window
      under Windows.  */
-  rc = assuan_pipe_connect (ctx, opt.pinentry_program, argv,
+  rc = assuan_pipe_connect (ctx, full_pgmname, argv,
 			    no_close_list, atfork_cb, ctrl,
 			    ASSUAN_PIPE_CONNECT_DETACHED);
   if (rc)
     {
       log_error ("can't connect to the PIN entry module '%s': %s\n",
-                 opt.pinentry_program, gpg_strerror (rc));
+                 full_pgmname, gpg_strerror (rc));
       assuan_release (ctx);
       return unlock_pinentry (gpg_error (GPG_ERR_NO_PIN_ENTRY));
     }

agent/gpg-agent.c

@@ -1827,9 +1827,14 @@ agent_sighup_action (void)
 {
   log_info ("SIGHUP received - "
             "re-reading configuration and flushing cache\n");
+
   agent_flush_cache ();
   reread_configuration ();
   agent_reload_trustlist ();
+  /* We flush the module name cache so that after installing a
+     "pinentry" binary that one can be used in case the
+     "pinentry-basic" fallback was in use.  */
+  gnupg_module_name_flush_some ();
 }
 
 

common/homedir.c

@@ -32,6 +32,7 @@
 #include <stdlib.h>
 #include <errno.h>
 #include <fcntl.h>
+#include <unistd.h>
 
 #ifdef HAVE_W32_SYSTEM
 #include <winsock2.h>   /* Due to the stupid mingw64 requirement to
@@ -607,6 +608,41 @@ dirmngr_user_socket_name (void)
 }
 
 
+/* Return the default pinentry name.  If RESET is true the internal
+   cache is first flushed.  */
+static const char *
+get_default_pinentry_name (int reset)
+{
+  static char *name;
+
+  if (reset)
+    {
+      xfree (name);
+      name = NULL;
+    }
+
+  if (!name)
+    {
+      name = xstrconcat (gnupg_bindir (),
+                         DIRSEP_S "pinentry" EXEEXT_S, NULL);
+      if (access (name, F_OK) && errno == ENOENT)
+        {
+          char *name2;
+          name2 = xstrconcat (gnupg_bindir (),
+                              DIRSEP_S "pinentry-basic" EXEEXT_S, NULL);
+          if (access (name2, F_OK))
+            xfree (name2); /* Does not exist.  */
+          else /* Switch to pinentry-basic.  */
+            {
+              xfree (name);
+              name = name2;
+            }
+        }
+    }
+  return name;
+}
+
+
 /* Return the file name of a helper tool.  WHICH is one of the
    GNUPG_MODULE_NAME_foo constants.  */
 const char *
@@ -630,9 +666,9 @@ gnupg_module_name (int which)
 
     case GNUPG_MODULE_NAME_PINENTRY:
 #ifdef GNUPG_DEFAULT_PINENTRY
-      return GNUPG_DEFAULT_PINENTRY;
+      return GNUPG_DEFAULT_PINENTRY;  /* (Set by a configure option) */
 #else
-      X(bindir, "pinentry");
+      return get_default_pinentry_name (0);
 #endif
 
     case GNUPG_MODULE_NAME_SCDAEMON:
@@ -683,3 +719,12 @@ gnupg_module_name (int which)
     }
 #undef X
 }
+
+
+/* Flush some of the cached module names.  This is for example used by
+   gpg-agent to allow configuring a different pinentry.  */
+void
+gnupg_module_name_flush_some (void)
+{
+  (void)get_default_pinentry_name (1);
+}

common/util.h

@@ -254,6 +254,7 @@ const char *dirmngr_user_socket_name (void);
 #define GNUPG_MODULE_NAME_GPGCONF       10
 #define GNUPG_MODULE_NAME_DIRMNGR_LDAP  11
 const char *gnupg_module_name (int which);
+void gnupg_module_name_flush_some (void);
 
 
 

doc/gpg-agent.texi

@@ -445,8 +445,10 @@ This option does nothing yet.
 
 @item --pinentry-program @var{filename}
 @opindex pinentry-program
-Use program @var{filename} as the PIN entry.  The default is installation
+Use program @var{filename} as the PIN entry.  The default is
-dependent.
+installation dependent.  With the default configuration the name of
+the default pinentry is @file{pinentry}; if that file does not exist
+but a @file{pinentry-basic} exist the latter is used.
 
 @item --pinentry-touch-file @var{filename}
 @opindex pinentry-touch-file