Add option for scdaemon to prompt user to ack card.

This is useful, e.g., for Yubikeys configured with fixed touch
policy.

Author: joel-u410

scd/app-openpgp.c

@@ -5327,6 +5327,9 @@ do_sign (app_t app, ctrl_t ctrl, const char *keyidstr, int hashalgo,
       wipe_and_free (pinvalue, pinlen);
     }
 
+  // Prompt to touch/ack the card.
+  if (opt.ack_prompt)
+    pincb (pincb_arg, _("--ack"), NULL);
 
   if (app->app_local->cardcap.ext_lc_le
       && app->app_local->keyattr[0].key_type == KEY_TYPE_RSA
@@ -5350,6 +5353,10 @@ do_sign (app_t app, ctrl_t ctrl, const char *keyidstr, int hashalgo,
       cache_pin (app, ctrl, 1, NULL);
     }
 
+  // Dismiss prompt after signing (or timing out)
+  if (opt.ack_prompt)
+    pincb (pincb_arg, NULL, NULL);
+
   return rc;
 }
 
@@ -5422,9 +5429,19 @@ do_auth (app_t app, ctrl_t ctrl, const char *keyidstr,
           exmode = 0;
           le_value = 0;
         }
+
+      // Prompt to touch/ack the card.
+      if (opt.ack_prompt)
+        pincb (pincb_arg, _("--ack"), NULL);
+
       rc = iso7816_internal_authenticate (app_get_slot (app), exmode,
                                           indata, indatalen, le_value,
                                           outdata, outdatalen);
+
+      // Dismiss prompt after authenticating (or timing out)
+      if (opt.ack_prompt)
+        pincb (pincb_arg, NULL, NULL);
+
       if (gpg_err_code (rc) == GPG_ERR_TIMEOUT)
         clear_chv_status (app, ctrl, 1);
     }
@@ -5617,10 +5634,19 @@ do_decipher (app_t app, ctrl_t ctrl, const char *keyidstr,
   else
     exmode = le_value = 0;
 
+  // Prompt to touch/ack the card.
+  if (opt.ack_prompt)
+    pincb (pincb_arg, _("--ack"), NULL);
+
   rc = iso7816_decipher (app_get_slot (app), exmode,
                          indata, indatalen, le_value, padind,
                          outdata, outdatalen);
   xfree (fixbuf);
+
+  // Dismiss prompt after deciphering (or timing out)
+  if (opt.ack_prompt)
+    pincb (pincb_arg, NULL, NULL);
+
   if (!rc && app->app_local->keyattr[1].key_type == KEY_TYPE_ECC)
     {
       unsigned char prefix = 0;

scd/scdaemon.c

@@ -102,6 +102,7 @@ enum cmd_and_opt_values
   oDenyAdmin,
   oDisableApplication,
   oApplicationPriority,
+  oAckPrompt,
   oEnablePinpadVarlen,
   oListenBacklog
 };
@@ -170,6 +171,7 @@ static gpgrt_opt_t opts[] = {
   ARGPARSE_s_s (oDisableApplication, "disable-application", "@"),
   ARGPARSE_s_s (oApplicationPriority, "application-priority",
                 N_("|LIST|change the application priority to LIST")),
+  ARGPARSE_s_n (oAckPrompt, "ack-prompt", N_("display ACK prompt while waiting for card")),
   ARGPARSE_s_i (oListenBacklog, "listen-backlog", "@"),
 
 
@@ -610,6 +612,8 @@ main (int argc, char **argv )
 
         case oDisablePinpad: opt.disable_pinpad = 1; break;
 
+        case oAckPrompt: opt.ack_prompt = 1; break;
+
         case oAllowAdmin: /* Dummy because allow is now the default.  */
           break;
         case oDenyAdmin: opt.allow_admin = 0; break;

scd/scdaemon.h

@@ -60,6 +60,7 @@ struct
   int disable_ccid;    /* Disable the use of the internal CCID driver. */
   int disable_pinpad;  /* Do not use a pinpad. */
   int enable_pinpad_varlen;  /* Use variable length input for pinpad. */
+  int ack_prompt;      /* Display ACK prompt to user when waiting for card. */
   int allow_admin;     /* Allow the use of admin commands for certain
                           cards. */
   int pcsc_shared;     /* Use shared PC/SC access.  */