path: root/scd/command.c

/* command.c - SCdaemon command handler
 * Copyright (C) 2001, 2002, 2003, 2004, 2005 Free Software Foundation, Inc.
 *
 * 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 2 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, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
 * USA.
 */

#include <config.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <unistd.h>
#include <signal.h>
#ifdef USE_GNU_PTH
# include <pth.h>
#endif

#include <assuan.h>

#include "scdaemon.h"
#include <ksba.h>
#include "app-common.h"
#include "apdu.h" /* Required for apdu_*_reader (). */
#include "exechelp.h"

/* Maximum length allowed as a PIN; used for INQUIRE NEEDPIN */
#define MAXLEN_PIN 100

/* Maximum allowed size of key data as used in inquiries. */
#define MAXLEN_KEYDATA 4096


#define set_error(e,t) assuan_set_error (ctx, gpg_error (e), (t))


/* Macro to flag a removed card.  */
#define TEST_CARD_REMOVAL(c,r)                              \
       do {                                                 \
          int _r = (r);                                     \
          if (gpg_err_code (_r) == GPG_ERR_CARD_NOT_PRESENT \
              || gpg_err_code (_r) == GPG_ERR_CARD_REMOVED) \
            update_card_removed ((c)->reader_slot, 1);      \
       } while (0)

#define IS_LOCKED(c)                                                     \
     (locked_session && locked_session != (c)->server_local              \
      && (c)->reader_slot != -1 && locked_session->ctrl_backlink         \
      && (c)->reader_slot == locked_session->ctrl_backlink->reader_slot)


/* This structure is used to keep track of open readers (slots). */
struct slot_status_s 
{
  int valid;  /* True if the other objects are valid. */
  int slot;   /* Slot number of the reader or -1 if not open. */

  int reset_failed; /* A reset failed. */

  int any;    /* Flag indicating whether any status check has been
                 done.  This is set once to indicate that the status
                 tracking for the slot has been initialized.  */
  unsigned int status;  /* Last status of the slot. */
  unsigned int changed; /* Last change counter of teh slot. */
};


/* Data used to associate an Assuan context with local server data.
   This object describes the local properties of one session.  */
struct server_local_s 
{
  /* We keep a list of all active sessions with the anchor at
     SESSION_LIST (see below).  This field is used for linking. */
  struct server_local_s *next_session; 

  /* This object is usually assigned to a CTRL object (which is
     globally visible).  While enumerating all sessions we sometimes
     need to access data of the CTRL object; thus we keep a
     backpointer here. */
  ctrl_t ctrl_backlink;

  /* The Assuan context used by this session/server. */
  assuan_context_t assuan_ctx;

  int event_signal;        /* Or 0 if not used. */

  /* True if the card has been removed and a reset is required to
     continue operation. */
  int card_removed;        
};


/* The table with information on all used slots.  FIXME: This is a
   different slot number than the one used by the APDU layer, and
   should be renamed.  */
static struct slot_status_s slot_table[10];


/* To keep track of all running sessions, we link all active server
   contexts and the anchor in this variable.  */
static struct server_local_s *session_list;

/* If a session has been locked we store a link to its server object
   in this variable. */
static struct server_local_s *locked_session;

/* While doing a reset we need to make sure that the ticker does not
   call scd_update_reader_status_file while we are using it. */
static pth_mutex_t status_file_update_lock = PTH_MUTEX_INIT;


/*-- Local prototypes --*/
static void update_reader_status_file (void);



/* Update the CARD_REMOVED element of all sessions using the reader
   given by SLOT to VALUE  */
static void
update_card_removed (int slot, int value)
{
  struct server_local_s *sl;

  for (sl=session_list; sl; sl = sl->next_session)
    if (sl->ctrl_backlink
        && sl->ctrl_backlink->reader_slot == slot)
      {
        sl->card_removed = value;
      }
  if (value)
    application_notify_card_removed (slot);
}



/* Check whether the option NAME appears in LINE */
static int
has_option (const char *line, const char *name)
{
  const char *s;
  int n = strlen (name);

  s = strstr (line, name);
  return (s && (s == line || spacep (s-1)) && (!s[n] || spacep (s+n)));
}


/* Convert the STRING into a newly allocated buffer while translating
   the hex numbers.  Stops at the first invalid character.  Blanks and
   colons are allowed to separate the hex digits.  Returns NULL on
   error or a newly malloced buffer and its length in LENGTH.  */
static unsigned char *
hex_to_buffer (const char *string, size_t *r_length)
{
  unsigned char *buffer;
  const char *s;
  size_t n;

  buffer = xtrymalloc (strlen (string)+1);
  if (!buffer)
    return NULL;
  for (s=string, n=0; *s; s++)
    {
      if (spacep (s) || *s == ':') 
        continue;
      if (hexdigitp (s) && hexdigitp (s+1))
        {
          buffer[n++] = xtoi_2 (s);
          s++;
        }
      else
        break;
    }
  *r_length = n;
  return buffer;
}



/* Reset the card and free the application context.  With SEND_RESET
   set to true actually send a RESET to the reader. */
static void
do_reset (ctrl_t ctrl, int send_reset)
{
  int slot = ctrl->reader_slot;

  if (!(slot == -1 || (slot >= 0 && slot < DIM(slot_table))))
    BUG ();

  if (ctrl->app_ctx)
    {
      release_application (ctrl->app_ctx);
      ctrl->app_ctx = NULL;
    }

  if (slot != -1 && send_reset && !IS_LOCKED (ctrl) )
    {
      if (apdu_reset (slot)) 
        {
          slot_table[slot].reset_failed = 1;
        }
    }

  /* If we hold a lock, unlock now. */
  if (locked_session && ctrl->server_local == locked_session)
    {
      locked_session = NULL;
      log_info ("implicitly unlocking due to RESET\n");
    }

  /* Reset card removed flag for the current reader.  We need to take
     the lock here so that the ticker thread won't concurrently try to
     update the file.  Note that the update function will set the card
     removed flag and we will later reset it - not a particualar nice
     way of implementing it but it works. */
  if (!pth_mutex_acquire (&status_file_update_lock, 0, NULL))
    {
      log_error ("failed to acquire status_fle_update lock\n");
      ctrl->reader_slot = -1;
      return;
    }
  update_reader_status_file ();
  update_card_removed (slot, 0);
  if (!pth_mutex_release (&status_file_update_lock))
    log_error ("failed to release status_file_update lock\n");

  /* Do this last, so that update_card_removed does its job.  */
  ctrl->reader_slot = -1;
}


static void
reset_notify (assuan_context_t ctx)
{
  ctrl_t ctrl = assuan_get_pointer (ctx); 

  do_reset (ctrl, 1);
}


static int
option_handler (assuan_context_t ctx, const char *key, const char *value)
{
  ctrl_t ctrl = assuan_get_pointer (ctx);

  if (!strcmp (key, "event-signal"))
    {
      /* A value of 0 is allowed to reset the event signal. */
      int i = *value? atoi (value) : -1;
      if (i < 0)
        return gpg_error (GPG_ERR_ASS_PARAMETER);
      ctrl->server_local->event_signal = i;
    }

 return 0;
}


/* Return the slot of the current reader or open the reader if no
   other sessions are using a reader.  Note, that we currently support
   only one reader but most of the code (except for this function)
   should be able to cope with several readers.  */
static int
get_reader_slot (void)
{
  struct slot_status_s *ss;

  ss = &slot_table[0]; /* One reader for now. */

  /* Initialize the item if needed. */
  if (!ss->valid)
    {
      ss->slot = -1;
      ss->valid = 1;
    }

  /* Try to open the reader. */
  if (ss->slot == -1)
    ss->slot = apdu_open_reader (opt.reader_port);

  /* Return the slot_table index.  */
  return 0;
}

/* If the card has not yet been opened, do it.  Note that this
   function returns an Assuan error, so don't map the error a second
   time.  */
static assuan_error_t
open_card (ctrl_t ctrl, const char *apptype)
{
  gpg_error_t err;
  int slot;

  /* If we ever got a card not present error code, return that.  Only
     the SERIALNO command and a reset are able to clear from that
     state. */
  if (ctrl->server_local->card_removed)
    return gpg_error (GPG_ERR_CARD_REMOVED);

  if ( IS_LOCKED (ctrl) )
    return gpg_error (GPG_ERR_LOCKED);

  if (ctrl->app_ctx)
    {
      /* Already initialized for one specific application.  Need to
         check that the client didn't requested a specific application
         different from the one in use. */
      return check_application_conflict (ctrl, apptype);
    }

  if (ctrl->reader_slot != -1)
    slot = ctrl->reader_slot;
  else
    slot = get_reader_slot ();
  ctrl->reader_slot = slot;
  if (slot == -1)
    err = gpg_error (GPG_ERR_CARD);
  else
    err = select_application (ctrl, slot, apptype, &ctrl->app_ctx);

  TEST_CARD_REMOVAL (ctrl, err);
  return err;
}


/* Do the percent and plus/space unescaping in place and return the
   length of the valid buffer. */
static size_t
percent_plus_unescape (unsigned char *string)
{
  unsigned char *p = string;
  size_t n = 0;

  while (*string)
    {
      if (*string == '%' && string[1] && string[2])
        { 
          string++;
          *p++ = xtoi_2 (string);
          n++;
          string+= 2;
        }
      else if (*string == '+')
        {
          *p++ = ' ';
          n++;
          string++;
        }
      else
        {
          *p++ = *string++;
          n++;
        }
    }

  return n;
}



/* SERIALNO [APPTYPE] 

   Return the serial number of the card using a status reponse.  This
   functon should be used to check for the presence of a card.

   If APPTYPE is given, an application of that type is selected and an
   error is returned if the application is not supported or available.
   The default is to auto-select the application using a hardwired
   preference system.  Note, that a future extension to this function
   may allow to specify a list and order of applications to try.

   This function is special in that it can be used to reset the card.
   Most other functions will return an error when a card change has
   been detected and the use of this function is therefore required.

   Background: We want to keep the client clear of handling card
   changes between operations; i.e. the client can assume that all
   operations are done on the same card unless he calls this function.
 */
static int
cmd_serialno (assuan_context_t ctx, char *line)
{
  ctrl_t ctrl = assuan_get_pointer (ctx);
  int rc = 0;
  char *serial_and_stamp;
  char *serial;
  time_t stamp;

  /* Clear the remove flag so that the open_card is able to reread it.  */
  if (ctrl->server_local->card_removed)
    {
      if ( IS_LOCKED (ctrl) )
        return gpg_error (GPG_ERR_LOCKED);
      do_reset (ctrl, 1);
    }

  if ((rc = open_card (ctrl, *line? line:NULL)))
    return rc;

  rc = app_get_serial_and_stamp (ctrl->app_ctx, &serial, &stamp);
  if (rc)
    return rc;

  rc = asprintf (&serial_and_stamp, "%s %lu", serial, (unsigned long)stamp);
  xfree (serial);
  if (rc < 0)
    return out_of_core ();
  rc = 0;
  assuan_write_status (ctx, "SERIALNO", serial_and_stamp);
  free (serial_and_stamp);
  return 0;
}




/* LEARN [--force]

   Learn all useful information of the currently inserted card.  When
   used without the force options, the command might do an INQUIRE
   like this:

      INQUIRE KNOWNCARDP <hexstring_with_serialNumber> <timestamp>

   The client should just send an "END" if the processing should go on
   or a "CANCEL" to force the function to terminate with a Cancel
   error message.  The response of this command is a list of status
   lines formatted as this:

     S APPTYPE <apptype>

   This returns the type of the application, currently the strings:

       P15     = PKCS-15 structure used
       DINSIG  = DIN SIG
       OPENPGP = OpenPGP card
 
   are implemented.  These strings are aliases for the AID

     S KEYPAIRINFO <hexstring_with_keygrip> <hexstring_with_id>

   If there is no certificate yet stored on the card a single "X" is
   returned as the keygrip.  In addition to the keypair info, information
   about all certificates stored on the card is also returned:

     S CERTINFO <certtype> <hexstring_with_id>

   Where CERTTYPE is a number indicating the type of certificate:
      0   := Unknown
      100 := Regular X.509 cert
      101 := Trusted X.509 cert
      102 := Useful X.509 cert
      110 := Root CA cert (DINSIG)

   For certain cards, more information will be returned:

     S KEY-FPR <no> <hexstring>

   For OpenPGP cards this returns the stored fingerprints of the
   keys. This can be used check whether a key is available on the
   card.  NO may be 1, 2 or 3.

     S CA-FPR <no> <hexstring>

   Similar to above, these are the fingerprints of keys assumed to be
   ultimately trusted.

     S DISP-NAME <name_of_card_holder>

   The name of the card holder as stored on the card; percent
   escaping takes place, spaces are encoded as '+'

     S PUBKEY-URL <url>

   The URL to be used for locating the entire public key.
     
   Note, that this function may be even be used on a locked card.
*/
static int
cmd_learn (assuan_context_t ctx, char *line)
{
  ctrl_t ctrl = assuan_get_pointer (ctx);
  int rc = 0;

  if ((rc = open_card (ctrl, NULL)))
    return rc;

  /* Unless the force option is used we try a shortcut by identifying
     the card using a serial number and inquiring the client with
     that. The client may choose to cancel the operation if he already
     knows about this card */
  {
    char *serial_and_stamp;
    char *serial;
    time_t stamp;

    rc = app_get_serial_and_stamp (ctrl->app_ctx, &serial, &stamp);
    if (rc)
      return rc;
    rc = asprintf (&serial_and_stamp, "%s %lu", serial, (unsigned long)stamp);
    xfree (serial);
    if (rc < 0)
      return out_of_core ();
    rc = 0;
    assuan_write_status (ctx, "SERIALNO", serial_and_stamp);

    if (!has_option (line, "--force"))
      {
        char *command;

        rc = asprintf (&command, "KNOWNCARDP %s", serial_and_stamp);
        if (rc < 0)
          {
            free (serial_and_stamp);
            return out_of_core ();
          }
        rc = 0;
        rc = assuan_inquire (ctx, command, NULL, NULL, 0); 
        free (command);  /* (must use standard free here) */
        if (rc)
          {
            if (gpg_err_code (rc) != GPG_ERR_ASS_CANCELED)
              log_error ("inquire KNOWNCARDP failed: %s\n",
                         gpg_strerror (rc));
            free (serial_and_stamp);
            return rc; 
          }
        /* not canceled, so we have to proceeed */
      }
    free (serial_and_stamp);
  }

  /* Let the application print out its collection of useful status
     information. */
  if (!rc)
    rc = app_write_learn_status (ctrl->app_ctx, ctrl);

  TEST_CARD_REMOVAL (ctrl, rc);
  return rc;
}



/* READCERT <hexified_certid>

   Note, that this function may even be used on a locked card.
 */
static int
cmd_readcert (assuan_context_t ctx, char *line)
{
  ctrl_t ctrl = assuan_get_pointer (ctx);
  int rc;
  unsigned char *cert;
  size_t ncert;

  if ((rc = open_card (ctrl, NULL)))
    return rc;

  line = xstrdup (line); /* Need a copy of the line. */
  rc = app_readcert (ctrl->app_ctx, line, &cert, &ncert);
  if (rc)
    log_error ("app_readcert failed: %s\n", gpg_strerror (rc));
  xfree (line);
  line = NULL;
  if (!rc)
    {
      rc = assuan_send_data (ctx, cert, ncert);
      xfree (cert);
      if (rc)
        return rc;
    }

  TEST_CARD_REMOVAL (ctrl, rc);
  return rc;
}


/* READKEY <keyid>

   Return the public key for the given cert or key ID as an standard
   S-Expression.

   Note, that this function may even be used on a locked card.
  */
static int
cmd_readkey (assuan_context_t ctx, char *line)
{
  ctrl_t ctrl = assuan_get_pointer (ctx);
  int rc;
  unsigned char *cert = NULL;
  size_t ncert, n;
  ksba_cert_t kc = NULL;
  ksba_sexp_t p;
  unsigned char *pk;
  size_t pklen;

  if ((rc = open_card (ctrl, NULL)))
    return rc;

  line = xstrdup (line); /* Need a copy of the line. */
  /* If the application supports the READKEY function we use that.
     Otherwise we use the old way by extracting it from the
     certificate.  */
  rc = app_readkey (ctrl->app_ctx, line, &pk, &pklen);
  if (!rc)
    { /* Yeah, got that key - send it back.  */
      rc = assuan_send_data (ctx, pk, pklen);
      xfree (pk);
      xfree (line);
      line = NULL;
      goto leave;
    }

  if (gpg_err_code (rc) != GPG_ERR_UNSUPPORTED_OPERATION)
    log_error ("app_readkey failed: %s\n", gpg_strerror (rc));
  else  
    {
      rc = app_readcert (ctrl->app_ctx, line, &cert, &ncert);
      if (rc)
        log_error ("app_readcert failed: %s\n", gpg_strerror (rc));
    }
  xfree (line);
  line = NULL;
  if (rc)
    goto leave;
      
  rc = ksba_cert_new (&kc);
  if (rc)
    {
      xfree (cert);
      goto leave;
    }
  rc = ksba_cert_init_from_mem (kc, cert, ncert);
  if (rc)
    {
      log_error ("failed to parse the certificate: %s\n", gpg_strerror (rc));
      goto leave;
    }

  p = ksba_cert_get_public_key (kc);
  if (!p)
    {
      rc = gpg_error (GPG_ERR_NO_PUBKEY);
      goto leave;
    }

  n = gcry_sexp_canon_len (p, 0, NULL, NULL);
  rc = assuan_send_data (ctx, p, n);
  xfree (p);


 leave:
  ksba_cert_release (kc);
  xfree (cert);
  TEST_CARD_REMOVAL (ctrl, rc);
  return rc;
}




/* SETDATA <hexstring> 

   The client should use this command to tell us the data he want to
   sign.  */
static int
cmd_setdata (assuan_context_t ctx, char *line)
{
  ctrl_t ctrl = assuan_get_pointer (ctx);
  int n;
  char *p;
  unsigned char *buf;

  if (locked_session && locked_session != ctrl->server_local)
    return gpg_error (GPG_ERR_LOCKED);

  /* Parse the hexstring. */
  for (p=line,n=0; hexdigitp (p); p++, n++)
    ;
  if (*p)
    return set_error (GPG_ERR_ASS_PARAMETER, "invalid hexstring");
  if (!n)
    return set_error (GPG_ERR_ASS_PARAMETER, "no data given");
  if ((n&1))
    return set_error (GPG_ERR_ASS_PARAMETER, "odd number of digits");
  n /= 2;
  buf = xtrymalloc (n);
  if (!buf)
    return out_of_core ();

  ctrl->in_data.value = buf;
  ctrl->in_data.valuelen = n;
  for (p=line, n=0; n < ctrl->in_data.valuelen; p += 2, n++)
    buf[n] = xtoi_2 (p);
  return 0;
}



static gpg_error_t 
pin_cb (void *opaque, const char *info, char **retstr)
{
  assuan_context_t ctx = opaque;
  char *command;
  int rc;
  unsigned char *value;
  size_t valuelen;

  if (!retstr)
    {
      /* We prompt for keypad entry.  To make sure that the popup has
         been show we use an inquire and not just a status message.
         We ignore any value returned.  */
      if (info)
        {
          log_debug ("prompting for keypad entry '%s'\n", info);
          rc = asprintf (&command, "POPUPKEYPADPROMPT %s", info);
          if (rc < 0)
            return gpg_error (gpg_err_code_from_errno (errno));
          rc = assuan_inquire (ctx, command, &value, &valuelen, MAXLEN_PIN); 
          free (command);  
        }
      else
        {
          log_debug ("dismiss keypad entry prompt\n");
          rc = assuan_inquire (ctx, "DISMISSKEYPADPROMPT",
                               &value, &valuelen, MAXLEN_PIN); 
        }
      if (!rc)
        xfree (value);
      return rc;
    }

  *retstr = NULL;
  log_debug ("asking for PIN '%s'\n", info);

  rc = asprintf (&command, "NEEDPIN %s", info);
  if (rc < 0)
    return gpg_error (gpg_err_code_from_errno (errno));

  /* Fixme: Write an inquire function which returns the result in
     secure memory and check all further handling of the PIN. */
  rc = assuan_inquire (ctx, command, &value, &valuelen, MAXLEN_PIN); 
  free (command);  
  if (rc)
    return rc;

  if (!valuelen || value[valuelen-1])
    {
      /* We require that the returned value is an UTF-8 string */
      xfree (value);
      return gpg_error (GPG_ERR_INV_RESPONSE);
    }
  *retstr = (char*)value;
  return 0;
}


/* PKSIGN [--hash=[rmd160|sha1|md5]] <hexified_id>

   The --hash option is optional; the default is SHA1.

 */
static int
cmd_pksign (assuan_context_t ctx, char *line)
{
  ctrl_t ctrl = assuan_get_pointer (ctx);
  int rc;
  unsigned char *outdata;
  size_t outdatalen;
  char *keyidstr;
  int hash_algo;

  if (has_option (line, "--hash=rmd160"))
    hash_algo = GCRY_MD_RMD160;
  else if (has_option (line, "--hash=sha1"))
    hash_algo = GCRY_MD_SHA1;
  else if (has_option (line, "--hash=md5"))
    hash_algo = GCRY_MD_MD5;
  else if (!strstr (line, "--"))
    hash_algo = GCRY_MD_SHA1; 
  else
    return set_error (GPG_ERR_ASS_PARAMETER, "invalid hash algorithm");
  /* Skip over options. */
  while ( *line == '-' && line[1] == '-' )
    {
      while (*line && !spacep (line))
        line++;
      while (spacep (line))
        line++;
    }

  if ( IS_LOCKED (ctrl) )
    return gpg_error (GPG_ERR_LOCKED);

  if ((rc = open_card (ctrl, NULL)))
    return rc;

  /* We have to use a copy of the key ID because the function may use
     the pin_cb which in turn uses the assuan line buffer and thus
     overwriting the original line with the keyid */
  keyidstr = xtrystrdup (line);
  if (!keyidstr)
    return out_of_core ();
  
  rc = app_sign (ctrl->app_ctx,
                 keyidstr, hash_algo,
                 pin_cb, ctx,
                 ctrl->in_data.value, ctrl->in_data.valuelen,
                 &outdata, &outdatalen);

  xfree (keyidstr);
  if (rc)
    {
      log_error ("card_sign failed: %s\n", gpg_strerror (rc));
    }
  else
    {
      rc = assuan_send_data (ctx, outdata, outdatalen);
      xfree (outdata);
      if (rc)
        return rc; /* that is already an assuan error code */
    }

  TEST_CARD_REMOVAL (ctrl, rc);
  return rc;
}

/* PKAUTH <hexified_id>

 */
static int
cmd_pkauth (assuan_context_t ctx, char *line)
{
  ctrl_t ctrl = assuan_get_pointer (ctx);
  int rc;
  unsigned char *outdata;
  size_t outdatalen;
  char *keyidstr;

  if ( IS_LOCKED (ctrl) )
    return gpg_error (GPG_ERR_LOCKED);

  if ((rc = open_card (ctrl, NULL)))
    return rc;

  if (!ctrl->app_ctx)
    return gpg_error (GPG_ERR_UNSUPPORTED_OPERATION);

 /* We have to use a copy of the key ID because the function may use
     the pin_cb which in turn uses the assuan line buffer and thus
     overwriting the original line with the keyid */
  keyidstr = xtrystrdup (line);
  if (!keyidstr)
    return out_of_core ();
  
  rc = app_auth (ctrl->app_ctx,
                 keyidstr,
                 pin_cb, ctx,
                 ctrl->in_data.value, ctrl->in_data.valuelen,
                 &outdata, &outdatalen);
  xfree (keyidstr);
  if (rc)
    {
      log_error ("app_auth_sign failed: %s\n", gpg_strerror (rc));
    }
  else
    {
      rc = assuan_send_data (ctx, outdata, outdatalen);
      xfree (outdata);
      if (rc)
        return rc; /* that is already an assuan error code */
    }

  TEST_CARD_REMOVAL (ctrl, rc);
  return rc;
}

/* PKDECRYPT <hexified_id>

 */
static int
cmd_pkdecrypt (assuan_context_t ctx, char *line)
{
  ctrl_t ctrl = assuan_get_pointer (ctx);
  int rc;
  unsigned char *outdata;
  size_t outdatalen;
  char *keyidstr;

  if ( IS_LOCKED (ctrl) )
    return gpg_error (GPG_ERR_LOCKED);

  if ((rc = open_card (ctrl, NULL)))
    return rc;

  keyidstr = xtrystrdup (line);
  if (!keyidstr)
    return out_of_core ();
  rc = app_decipher (ctrl->app_ctx,
                     keyidstr, 
                     pin_cb, ctx,
                     ctrl->in_data.value, ctrl->in_data.valuelen,
                     &outdata, &outdatalen);

  xfree (keyidstr);
  if (rc)
    {
      log_error ("card_create_signature failed: %s\n", gpg_strerror (rc));
    }
  else
    {
      rc = assuan_send_data (ctx, outdata, outdatalen);
      xfree (outdata);
      if (rc)
        return rc; /* that is already an assuan error code */
    }

  TEST_CARD_REMOVAL (ctrl, rc);
  return rc;
}


/* GETATTR <name>

   This command is used to retrieve data from a smartcard.  The
   allowed names depend on the currently selected smartcard
   application.  NAME must be percent and '+' escaped.  The value is
   returned through status message, see the LEARN command for details.

   However, the current implementation assumes that Name is not escaped;
   this works as long as noone uses arbitrary escaping. 
 
   Note, that this function may even be used on a locked card.
*/
static int
cmd_getattr (assuan_context_t ctx, char *line)
{
  ctrl_t ctrl = assuan_get_pointer (ctx);
  int rc;
  const char *keyword;

  if ((rc = open_card (ctrl, NULL)))
    return rc;

  keyword = line;
  for (; *line && !spacep (line); line++)
    ;
  if (*line)
      *line++ = 0;

  /* (We ignore any garbage for now.) */

  /* FIXME: Applications should not return sensitive data if the card
     is locked.  */
  rc = app_getattr (ctrl->app_ctx, ctrl, keyword);

  TEST_CARD_REMOVAL (ctrl, rc);
  return rc;
}


/* SETATTR <name> <value> 

   This command is used to store data on a a smartcard.  The allowed
   names and values are depend on the currently selected smartcard
   application.  NAME and VALUE must be percent and '+' escaped.

   However, the curent implementation assumes that Name is not escaped;
   this works as long as noone uses arbitrary escaping. 
 
   A PIN will be requested for most NAMEs.  See the corresponding
   setattr function of the actually used application (app-*.c) for
   details.  */
static int
cmd_setattr (assuan_context_t ctx, char *orig_line)
{
  ctrl_t ctrl = assuan_get_pointer (ctx);
  int rc;
  char *keyword;
  int keywordlen;
  size_t nbytes;
  char *line, *linebuf;

  if ( IS_LOCKED (ctrl) )
    return gpg_error (GPG_ERR_LOCKED);

  if ((rc = open_card (ctrl, NULL)))
    return rc;

  /* We need to use a copy of LINE, because PIN_CB uses the same
     context and thus reuses the Assuan provided LINE. */
  line = linebuf = xtrystrdup (orig_line);
  if (!line)
    return out_of_core ();

  keyword = line;
  for (keywordlen=0; *line && !spacep (line); line++, keywordlen++)
    ;
  if (*line)
      *line++ = 0;
  while (spacep (line))
    line++;
  nbytes = percent_plus_unescape ((unsigned char*)line);

  rc = app_setattr (ctrl->app_ctx, keyword, pin_cb, ctx,
                    (const unsigned char*)line, nbytes);
  xfree (linebuf);

  TEST_CARD_REMOVAL (ctrl, rc);
  return rc;
}



/* WRITEKEY [--force] <keyid> 

   This command is used to store a secret key on a a smartcard.  The
   allowed keyids depend on the currently selected smartcard
   application. The actual keydata is requested using the inquiry
   "KETDATA" and need to be provided without any protection.  With
   --force set an existing key under this KEYID will get overwritten.
   The keydata is expected to be the usual canonical encoded
   S-expression.

   A PIN will be requested for most NAMEs.  See the corresponding
   writekey function of the actually used application (app-*.c) for
   details.  */
static int
cmd_writekey (assuan_context_t ctx, char *line)
{
  ctrl_t ctrl = assuan_get_pointer (ctx);
  int rc;
  char *keyid;
  int force = has_option (line, "--force");
  unsigned char *keydata;
  size_t keydatalen;

  if ( IS_LOCKED (ctrl) )
    return gpg_error (GPG_ERR_LOCKED);

  /* Skip over options. */
  while ( *line == '-' && line[1] == '-' )
    {
      while (*line && !spacep (line))
        line++;
      while (spacep (line))
        line++;
    }
  if (!*line)
    return set_error (GPG_ERR_ASS_PARAMETER, "no keyid given");
  keyid = line;
  while (*line && !spacep (line))
    line++;
  *line = 0;

  if ((rc = open_card (ctrl, NULL)))
    return rc;

  if (!ctrl->app_ctx)
    return gpg_error (GPG_ERR_UNSUPPORTED_OPERATION);

  keyid = xtrystrdup (keyid);
  if (!keyid)
    return out_of_core ();

  /* Now get the actual keydata. */
  rc = assuan_inquire (ctx, "KEYDATA", &keydata, &keydatalen, MAXLEN_KEYDATA);
  if (rc)
    {
      xfree (keyid);
      return rc;
    }

  /* Write the key to the card. */
  rc = app_writekey (ctrl->app_ctx, ctrl, keyid, force? 1:0,
                     pin_cb, ctx, keydata, keydatalen);
  xfree (keyid);
  xfree (keydata);

  TEST_CARD_REMOVAL (ctrl, rc);
  return rc;
}



/* GENKEY [--force] <no>

   Generate a key on-card identified by NO, which is application
   specific.  Return values are application specific.  For OpenPGP
   cards 2 status lines are returned:

     S KEY-FPR  <hexstring>
     S KEY-CREATED-AT <seconds_since_epoch>
     S KEY-DATA [p|n] <hexdata>
     

   --force is required to overwrite an already existing key.  The
   KEY-CREATED-AT is required for further processing because it is
   part of the hashed key material for the fingerprint.

   The public part of the key can also later be retrieved using the
   READKEY command.

 */
static int
cmd_genkey (assuan_context_t ctx, char *line)
{
  ctrl_t ctrl = assuan_get_pointer (ctx);
  int rc;
  char *keyno;
  int force = has_option (line, "--force");

  if ( IS_LOCKED (ctrl) )
    return gpg_error (GPG_ERR_LOCKED);

  /* Skip over options. */
  while ( *line == '-' && line[1] == '-' )
    {
      while (*line && !spacep (line))
        line++;
      while (spacep (line))
        line++;
    }
  if (!*line)
    return set_error (GPG_ERR_ASS_PARAMETER, "no key number given");
  keyno = line;
  while (*line && !spacep (line))
    line++;
  *line = 0;

  if ((rc = open_card (ctrl, NULL)))
    return rc;

  if (!ctrl->app_ctx)
    return gpg_error (GPG_ERR_UNSUPPORTED_OPERATION);

  keyno = xtrystrdup (keyno);
  if (!keyno)
    return out_of_core ();
  rc = app_genkey (ctrl->app_ctx, ctrl, keyno, force? 1:0, pin_cb, ctx);
  xfree (keyno);

  TEST_CARD_REMOVAL (ctrl, rc);
  return rc;
}


/* RANDOM <nbytes>

   Get NBYTES of random from the card and send them back as data. 

   Note, that this function may be even be used on a locked card.
*/
static int
cmd_random (assuan_context_t ctx, char *line)
{
  ctrl_t ctrl = assuan_get_pointer (ctx);
  int rc;
  size_t nbytes;
  unsigned char *buffer;

  if (!*line)
    return set_error (GPG_ERR_ASS_PARAMETER, "number of requested bytes missing");
  nbytes = strtoul (line, NULL, 0);

  if ((rc = open_card (ctrl, NULL)))
    return rc;

  if (!ctrl->app_ctx)
    return gpg_error (GPG_ERR_UNSUPPORTED_OPERATION);

  buffer = xtrymalloc (nbytes);
  if (!buffer)
    return out_of_core ();

  rc = app_get_challenge (ctrl->app_ctx, nbytes, buffer);
  if (!rc)
    {
      rc = assuan_send_data (ctx, buffer, nbytes);
      xfree (buffer);
      return rc; /* that is already an assuan error code */
    }
  xfree (buffer);

  TEST_CARD_REMOVAL (ctrl, rc);
  return rc;
}


/* PASSWD [--reset] <chvno>
  
   Change the PIN or reset the retry counter of the card holder
   verfication vector CHVNO. */
static int
cmd_passwd (assuan_context_t ctx, char *line)
{
  ctrl_t ctrl = assuan_get_pointer (ctx);
  int rc;
  char *chvnostr;
  int reset_mode = has_option (line, "--reset");

  if ( IS_LOCKED (ctrl) )
    return gpg_error (GPG_ERR_LOCKED);

  /* Skip over options. */
  while (*line == '-' && line[1] == '-')
    {
      while (*line && !spacep (line))
        line++;
      while (spacep (line))
        line++;
    }
  if (!*line)
    return set_error (GPG_ERR_ASS_PARAMETER, "no CHV number given");
  chvnostr = line;
  while (*line && !spacep (line))
    line++;
  *line = 0;

  if ((rc = open_card (ctrl, NULL)))
    return rc;

  if (!ctrl->app_ctx)
    return gpg_error (GPG_ERR_UNSUPPORTED_OPERATION);
  
  chvnostr = xtrystrdup (chvnostr);
  if (!chvnostr)
    return out_of_core ();
  rc = app_change_pin (ctrl->app_ctx, ctrl, chvnostr, reset_mode, pin_cb, ctx);
  if (rc)
    log_error ("command passwd failed: %s\n", gpg_strerror (rc));
  xfree (chvnostr);

  TEST_CARD_REMOVAL (ctrl, rc);
  return rc;
}


/* CHECKPIN <idstr>

   Perform a VERIFY operation without doing anything else.  This may
   be used to initialize a the PIN cache earlier to long lasting
   operations.  Its use is highly application dependent.

   For OpenPGP:

      Perform a simple verify operation for CHV1 and CHV2, so that
      further operations won't ask for CHV2 and it is possible to do a
      cheap check on the PIN: If there is something wrong with the PIN
      entry system, only the regular CHV will get blocked and not the
      dangerous CHV3.  IDSTR is the usual card's serial number in hex
      notation; an optional fingerprint part will get ignored.  There
      is however a special mode if the IDSTR is sffixed with the
      literal string "[CHV3]": In this case the Admin PIN is checked
      if and only if the retry counter is still at 3.

 */
static int
cmd_checkpin (assuan_context_t ctx, char *line)
{
  ctrl_t ctrl = assuan_get_pointer (ctx);
  int rc;
  char *keyidstr;

  if ( IS_LOCKED (ctrl) )
    return gpg_error (GPG_ERR_LOCKED);

  if ((rc = open_card (ctrl, NULL)))
    return rc;

  if (!ctrl->app_ctx)
    return gpg_error (GPG_ERR_UNSUPPORTED_OPERATION);

  /* We have to use a copy of the key ID because the function may use
     the pin_cb which in turn uses the assuan line buffer and thus
     overwriting the original line with the keyid. */
  keyidstr = xtrystrdup (line);
  if (!keyidstr)
    return out_of_core ();
  
  rc = app_check_pin (ctrl->app_ctx,
                      keyidstr,
                      pin_cb, ctx);
  xfree (keyidstr);
  if (rc)
    log_error ("app_check_pin failed: %s\n", gpg_strerror (rc));

  TEST_CARD_REMOVAL (ctrl, rc);
  return rc;
}


/* LOCK [--wait]

   Grant exclusive card access to this session.  Note that there is
   no lock counter used and a second lock from the same session will
   be ignored.  A single unlock (or RESET) unlocks the session.
   Return GPG_ERR_LOCKED if another session has locked the reader.

   If the option --wait is given the command will wait until a
   lock has been released.
 */
static int
cmd_lock (assuan_context_t ctx, char *line)
{
  ctrl_t ctrl = assuan_get_pointer (ctx);
  int rc = 0;

 retry:
  if (locked_session)
    {
      if (locked_session != ctrl->server_local)
        rc = gpg_error (GPG_ERR_LOCKED);
    }
  else
    locked_session = ctrl->server_local;

#ifdef USE_GNU_PTH
  if (rc && has_option (line, "--wait"))
    {
      rc = 0;
      pth_sleep (1); /* Better implement an event mechanism. However,
                        for card operations this should be
                        sufficient. */
      /* FIXME: Need to check that the connection is still alive.
         This can be done by issuing status messages. */
      goto retry;
    }
#endif /*USE_GNU_PTH*/
  
  if (rc)
    log_error ("cmd_lock failed: %s\n", gpg_strerror (rc));
  return rc;
}


/* UNLOCK

   Release exclusive card access.
 */
static int
cmd_unlock (assuan_context_t ctx, char *line)
{
  ctrl_t ctrl = assuan_get_pointer (ctx);
  int rc = 0;

  if (locked_session)
    {
      if (locked_session != ctrl->server_local)
        rc = gpg_error (GPG_ERR_LOCKED);
      else
        locked_session = NULL;
    }
  else
    rc = gpg_error (GPG_ERR_NOT_LOCKED);

  if (rc)
    log_error ("cmd_unlock failed: %s\n", gpg_strerror (rc));
  return rc;
}


/* GETINFO <what>

   Multi purpose command to return certain information.  
   Supported values of WHAT are:

   socket_name - Return the name of the socket.
   status - Return the status of the current slot (in the future, may
   also return the status of all slots).  The status is a list of
   one-character flags.  The following flags are currently defined:
     'u'  Usable card present.  This is the normal state during operation.
     'r'  Card removed.  A reset is necessary.
   These flags are exclusive.
*/

static int
cmd_getinfo (assuan_context_t ctx, char *line)
{
  int rc = 0;

  if (!strcmp (line, "socket_name"))
    {
      const char *s = scd_get_socket_name ();

      if (s)
        rc = assuan_send_data (ctx, s, strlen (s));
      else
        rc = gpg_error (GPG_ERR_NO_DATA);
    }
  else if (!strcmp (line, "status"))
    {
      ctrl_t ctrl = assuan_get_pointer (ctx);
      int slot = ctrl->reader_slot;
      char flag = 'r';

      if (!ctrl->server_local->card_removed && slot != -1)
	{
	  struct slot_status_s *ss;
	  
	  if (!(slot >= 0 && slot < DIM(slot_table)))
	    BUG ();

	  ss = &slot_table[slot];

	  if (!ss->valid)
	    BUG ();

	  if (ss->any && (ss->status & 1))
	    flag = 'u';
	}
      rc = assuan_send_data (ctx, &flag, 1);
    }
  else
    rc = set_error (GPG_ERR_ASS_PARAMETER, "unknown value for WHAT");
  return rc;
}


/* RESTART

   Restart the current connection; this is a kind of warm reset.  It
   deletes the context used by this connection but does not send a
   RESET to the card.  Thus the card itself won't get reset. 

   This is used by gpg-agent to reuse a primary pipe connection and
   may be used by clients to backup from a conflict in the serial
   command; i.e. to select another application. 
*/

static int
cmd_restart (assuan_context_t ctx, char *line)
{
  ctrl_t ctrl = assuan_get_pointer (ctx);

  if (ctrl->app_ctx)
    {
      release_application (ctrl->app_ctx);
      ctrl->app_ctx = NULL;
    }
  if (locked_session && ctrl->server_local == locked_session)
    {
      locked_session = NULL;
      log_info ("implicitly unlocking due to RESTART\n");
    }
  return 0;
}


/* APDU [--atr] [--more] [hexstring]

   Send an APDU to the current reader.  This command bypasses the high
   level functions and sends the data directly to the card.  HEXSTRING
   is expected to be a proper APDU.  If HEXSTRING is not given no
   commands are set to the card but the command will implictly check
   whether the card is ready for use. 

   Using the option "--atr" returns the ATR of the card as a status
   message before any data like this:
     S CARD-ATR 3BFA1300FF813180450031C173C00100009000B1

   Using the option --more handles the card status word MORE_DATA
   (61xx) and concatenate all reponses to one block.

 */
static int
cmd_apdu (assuan_context_t ctx, char *line)
{
  ctrl_t ctrl = assuan_get_pointer (ctx);
  int rc;
  unsigned char *apdu;
  size_t apdulen;
  int with_atr;
  int handle_more;

  with_atr = has_option (line, "--atr");
  handle_more = has_option (line, "--more");

  /* Skip over options. */
  while ( *line == '-' && line[1] == '-' )
    {
      while (*line && !spacep (line))
        line++;
      while (spacep (line))
        line++;
    }

  if ( IS_LOCKED (ctrl) )
    return gpg_error (GPG_ERR_LOCKED);

  if ((rc = open_card (ctrl, NULL)))
    return rc;

  if (with_atr)
    {
      unsigned char *atr;
      size_t atrlen;
      int i;
      char hexbuf[400];
      
      atr = apdu_get_atr (ctrl->reader_slot, &atrlen);
      if (!atr || atrlen > sizeof hexbuf - 2 )
        {
          rc = gpg_error (GPG_ERR_INV_CARD);
          goto leave;
        }
      for (i=0; i < atrlen; i++)
        sprintf (hexbuf+2*i, "%02X", atr[i]);
      xfree (atr);
      send_status_info (ctrl, "CARD-ATR", hexbuf, strlen (hexbuf), NULL, 0);
    }

  apdu = hex_to_buffer (line, &apdulen);
  if (!apdu)
    {
      rc = gpg_error_from_syserror ();
      goto leave;
    }
  if (apdulen)
    {
      unsigned char *result = NULL;
      size_t resultlen;

      rc = apdu_send_direct (ctrl->reader_slot, apdu, apdulen, handle_more,
                             &result, &resultlen);
      if (rc)
        log_error ("apdu_send_direct failed: %s\n", gpg_strerror (rc));
      else
        {
          rc = assuan_send_data (ctx, result, resultlen);
          xfree (result);
        }
    }
  xfree (apdu);

 leave:
  TEST_CARD_REMOVAL (ctrl, rc);
  return rc;
}





/* Tell the assuan library about our commands */
static int
register_commands (assuan_context_t ctx)
{
  static struct {
    const char *name;
    int (*handler)(assuan_context_t, char *line);
  } table[] = {
    { "SERIALNO",     cmd_serialno },
    { "LEARN",        cmd_learn },
    { "READCERT",     cmd_readcert },
    { "READKEY",      cmd_readkey },
    { "SETDATA",      cmd_setdata },
    { "PKSIGN",       cmd_pksign },
    { "PKAUTH",       cmd_pkauth },
    { "PKDECRYPT",    cmd_pkdecrypt },
    { "INPUT",        NULL }, 
    { "OUTPUT",       NULL }, 
    { "GETATTR",      cmd_getattr },
    { "SETATTR",      cmd_setattr },
    { "WRITEKEY",     cmd_writekey },
    { "GENKEY",       cmd_genkey },
    { "RANDOM",       cmd_random },
    { "PASSWD",       cmd_passwd },
    { "CHECKPIN",     cmd_checkpin },
    { "LOCK",         cmd_lock },
    { "UNLOCK",       cmd_unlock },
    { "GETINFO",      cmd_getinfo },
    { "RESTART",      cmd_restart },
    { "APDU",         cmd_apdu },
    { NULL }
  };
  int i, rc;

  for (i=0; table[i].name; i++)
    {
      rc = assuan_register_command (ctx, table[i].name, table[i].handler);
      if (rc)
        return rc;
    } 
  assuan_set_hello_line (ctx, "GNU Privacy Guard's Smartcard server ready");

  assuan_register_reset_notify (ctx, reset_notify);
  assuan_register_option_handler (ctx, option_handler);
  return 0;
}


/* Startup the server.  If FD is given as -1 this is simple pipe
   server, otherwise it is a regular server. */
void
scd_command_handler (ctrl_t ctrl, int fd)
{
  int rc;
  assuan_context_t ctx;
  
  if (fd == -1)
    {
      int filedes[2];

      filedes[0] = 0;
      filedes[1] = 1;
      rc = assuan_init_pipe_server (&ctx, filedes);
    }
  else
    {
      rc = assuan_init_socket_server_ext (&ctx, fd, 2);
    }
  if (rc)
    {
      log_error ("failed to initialize the server: %s\n",
                 gpg_strerror(rc));
      scd_exit (2);
    }
  rc = register_commands (ctx);
  if (rc)
    {
      log_error ("failed to register commands with Assuan: %s\n",
                 gpg_strerror(rc));
      scd_exit (2);
    }
  assuan_set_pointer (ctx, ctrl);

  /* Allocate and initialize the server object.  Put it into the list
     of active sessions. */
  ctrl->server_local = xcalloc (1, sizeof *ctrl->server_local);
  ctrl->server_local->next_session = session_list;
  session_list = ctrl->server_local;
  ctrl->server_local->ctrl_backlink = ctrl;
  ctrl->server_local->assuan_ctx = ctx;

  if (DBG_ASSUAN)
    assuan_set_log_stream (ctx, log_get_stream ());

  /* We open the reader right at startup so that the ticker is able to
     update the status file. */
  if (ctrl->reader_slot == -1)
    {
      ctrl->reader_slot = get_reader_slot ();
    }

  /* Command processing loop. */
  for (;;)
    {
      rc = assuan_accept (ctx);
      if (rc == -1)
        {
          break;
        }
      else if (rc)
        {
          log_info ("Assuan accept problem: %s\n", gpg_strerror (rc));
          break;
        }
      
      rc = assuan_process (ctx);
      if (rc)
        {
          log_info ("Assuan processing failed: %s\n", gpg_strerror (rc));
          continue;
        }
    }

  /* Cleanup.  */
  do_reset (ctrl, 0); 

  /* Release the server object.  */
  if (session_list == ctrl->server_local)
    session_list = ctrl->server_local->next_session;
  else
    {
      struct server_local_s *sl;
      
      for (sl=session_list; sl->next_session; sl = sl->next_session)
        if (sl->next_session == ctrl->server_local)
          break;
      if (!sl->next_session)
          BUG ();
      sl->next_session = ctrl->server_local->next_session;
    }
  xfree (ctrl->server_local);
  ctrl->server_local = NULL;

  /* Release the Assuan context.  */
  assuan_deinit_server (ctx);
}


/* Send a line with status information via assuan and escape all given
   buffers. The variable elements are pairs of (char *, size_t),
   terminated with a (NULL, 0). */
void
send_status_info (ctrl_t ctrl, const char *keyword, ...)
{
  va_list arg_ptr;
  const unsigned char *value;
  size_t valuelen;
  char buf[950], *p;
  size_t n;
  assuan_context_t ctx = ctrl->server_local->assuan_ctx;
  
  va_start (arg_ptr, keyword);

  p = buf; 
  n = 0;
  while ( (value = va_arg (arg_ptr, const unsigned char *)) )
    {
      valuelen = va_arg (arg_ptr, size_t);
      if (!valuelen)
        continue; /* empty buffer */
      if (n)
        {
          *p++ = ' ';
          n++;
        }
      for ( ; valuelen && n < DIM (buf)-2; n++, valuelen--, value++)
        {
          if (*value < ' ' || *value == '+')
            {
              sprintf (p, "%%%02X", *value);
              p += 3;
            }
          else if (*value == ' ')
            *p++ = '+';
          else
            *p++ = *value;
        }
    }
  *p = 0;
  assuan_write_status (ctx, keyword, buf);

  va_end (arg_ptr);
}


/* This is the core of scd_update_reader_status_file but the caller
   needs to take care of the locking. */
static void
update_reader_status_file (void)
{
  int idx;
  unsigned int status, changed;

  /* Note, that we only try to get the status, because it does not
     make sense to wait here for a operation to complete.  If we are
     busy working with a card, delays in the status file update should
     be acceptable. */
  for (idx=0; idx < DIM(slot_table); idx++)
    {
      struct slot_status_s *ss = slot_table + idx;

      if (!ss->valid || ss->slot == -1)
        continue; /* Not valid or reader not yet open. */
      
      if ( apdu_get_status (ss->slot, 0, &status, &changed) )
        continue; /* Get status failed. */

      if (!ss->any || ss->status != status || ss->changed != changed )
        {
          char *fname;
          char templ[50];
          FILE *fp;
          struct server_local_s *sl;

          log_info ("updating status of slot %d to 0x%04X\n",
                    ss->slot, status);

	  /* FIXME: Should this be IDX instead of ss->slot?  This
	     depends on how client sessions will associate the reader
	     status with their session.  */
          sprintf (templ, "reader_%d.status", ss->slot);
          fname = make_filename (opt.homedir, templ, NULL );
          fp = fopen (fname, "w");
          if (fp)
            {
              fprintf (fp, "%s\n",
                       (status & 1)? "USABLE":
                       (status & 4)? "ACTIVE":
                       (status & 2)? "PRESENT": "NOCARD");
              fclose (fp);
            }
          xfree (fname);
            
          /* If a status script is executable, run it. */
          {
            const char *args[9], *envs[2];
            char numbuf1[30], numbuf2[30], numbuf3[30];
            char *homestr, *envstr;
            gpg_error_t err;
            
            homestr = make_filename (opt.homedir, NULL);
            if (asprintf (&envstr, "GNUPGHOME=%s", homestr) < 0)
              log_error ("out of core while building environment\n");
            else
              {
                envs[0] = envstr;
                envs[1] = NULL;

                sprintf (numbuf1, "%d", ss->slot);
                sprintf (numbuf2, "0x%04X", ss->status);
                sprintf (numbuf3, "0x%04X", status);
                args[0] = "--reader-port";
                args[1] = numbuf1; 
                args[2] = "--old-code";
                args[3] = numbuf2;  
                args[4] = "--new-code";
                args[5] = numbuf3; 
                args[6] = "--status";
                args[7] = ((status & 1)? "USABLE":
                           (status & 4)? "ACTIVE":
                           (status & 2)? "PRESENT": "NOCARD");
                args[8] = NULL;  

                fname = make_filename (opt.homedir, "scd-event", NULL);
                err = gnupg_spawn_process_detached (fname, args, envs);
                if (err && gpg_err_code (err) != GPG_ERR_ENOENT)
                  log_error ("failed to run event handler `%s': %s\n",
                             fname, gpg_strerror (err));
                xfree (fname);
                free (envstr);
              }
            xfree (homestr);
          }

          /* Set the card removed flag for all current sessions.  We
             will set this on any card change because a reset or
             SERIALNO request must be done in any case.  */
          if (ss->any)
            update_card_removed (idx, 1);
          
          ss->any = 1;
          ss->status = status;
          ss->changed = changed;

          /* Send a signal to all clients who applied for it.  */
          for (sl=session_list; sl; sl = sl->next_session)
            if (sl->event_signal && sl->assuan_ctx)
              {
                pid_t pid = assuan_get_pid (sl->assuan_ctx);
                int signo = sl->event_signal;
                
                log_info ("client pid is %d, sending signal %d\n",
                          pid, signo);
#ifndef HAVE_W32_SYSTEM
                if (pid != (pid_t)(-1) && pid && signo > 0)
                  kill (pid, signo);
#endif
              }

        }
    }
}

/* This function is called by the ticker thread to check for changes
   of the reader stati.  It updates the reader status files and if
   requested by the caller also send a signal to the caller.  */
void
scd_update_reader_status_file (void)
{
  if (!pth_mutex_acquire (&status_file_update_lock, 1, NULL))
    return; /* locked - give up. */
  update_reader_status_file ();
  if (!pth_mutex_release (&status_file_update_lock))
    log_error ("failed to release status_file_update lock\n");
}