/* call-agent.c - Divert GPG operations to the agent.
 * Copyright (C) 2001, 2002, 2003, 2006, 2007, 2008, 2009,
 *               2010 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 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/>.
 */

#include <config.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>
#include <time.h>
#include <assert.h>
#ifdef HAVE_LOCALE_H
#include <locale.h>
#endif

#include "gpg.h"
#include <assuan.h>
#include "util.h"
#include "membuf.h"
#include "options.h"
#include "i18n.h"
#include "asshelp.h"
#include "sysutils.h"
#include "call-agent.h"
#include "status.h"

#ifndef DBG_ASSUAN
# define DBG_ASSUAN 1
#endif

static assuan_context_t agent_ctx = NULL;
static int did_early_card_test;

struct cipher_parm_s
{
  ctrl_t ctrl;
  assuan_context_t ctx;
  unsigned char *ciphertext;
  size_t ciphertextlen;
};

struct writecert_parm_s
{
  assuan_context_t ctx;
  const unsigned char *certdata;
  size_t certdatalen;
};

struct writekey_parm_s
{
  assuan_context_t ctx;
  const unsigned char *keydata;
  size_t keydatalen;
};

struct genkey_parm_s
{
  ctrl_t ctrl;
  assuan_context_t ctx;
  const char *keyparms;
};

struct import_key_parm_s
{
  ctrl_t ctrl;
  assuan_context_t ctx;
  const void *key;
  size_t keylen;
};


struct cache_nonce_parm_s
{
  char **cache_nonce_addr;
  char **passwd_nonce_addr;
};


struct scd_genkey_parm_s
{
  struct agent_card_genkey_s *cgk;
  char *savedbytes;     /* Malloced space to save key parameter chunks.  */
};


static gpg_error_t learn_status_cb (void *opaque, const char *line);



/* If RC is not 0, write an appropriate status message. */
static void
status_sc_op_failure (int rc)
{
  switch (gpg_err_code (rc))
    {
    case 0:
      break;
    case GPG_ERR_CANCELED:
    case GPG_ERR_FULLY_CANCELED:
      write_status_text (STATUS_SC_OP_FAILURE, "1");
      break;
    case GPG_ERR_BAD_PIN:
      write_status_text (STATUS_SC_OP_FAILURE, "2");
      break;
    default:
      write_status (STATUS_SC_OP_FAILURE);
      break;
    }
}



/* Try to connect to the agent via socket or fork it off and work by
   pipes.  Handle the server's initial greeting */
static int
start_agent (ctrl_t ctrl, int for_card)
{
  int rc;

  (void)ctrl;  /* Not yet used.  */

  /* Fixme: We need a context for each thread or serialize the access
     to the agent. */
  if (agent_ctx)
    rc = 0;
  else
    {
      rc = start_new_gpg_agent (&agent_ctx,
                                GPG_ERR_SOURCE_DEFAULT,
                                opt.homedir,
                                opt.agent_program,
                                opt.lc_ctype, opt.lc_messages,
                                opt.session_env,
                                opt.verbose, DBG_ASSUAN,
                                NULL, NULL);
      if (!rc)
        {
          /* Tell the agent that we support Pinentry notifications.
             No error checking so that it will work also with older
             agents.  */
          assuan_transact (agent_ctx, "OPTION allow-pinentry-notify",
                           NULL, NULL, NULL, NULL, NULL, NULL);
          /* Tell the agent about what version we are aware.  This is
             here used to indirectly enable GPG_ERR_FULLY_CANCELED.  */
          assuan_transact (agent_ctx, "OPTION agent-awareness=2.1.0",
                           NULL, NULL, NULL, NULL, NULL, NULL);

        }
    }

  if (!rc && for_card && !did_early_card_test)
    {
      /* Request the serial number of the card for an early test.  */
      struct agent_card_info_s info;

      memset (&info, 0, sizeof info);
      rc = assuan_transact (agent_ctx, "SCD SERIALNO openpgp",
                            NULL, NULL, NULL, NULL,
                            learn_status_cb, &info);
      if (rc)
        {
          switch (gpg_err_code (rc))
            {
            case GPG_ERR_NOT_SUPPORTED:
            case GPG_ERR_NO_SCDAEMON:
              write_status_text (STATUS_CARDCTRL, "6");
              break;
            default:
              write_status_text (STATUS_CARDCTRL, "4");
              log_info ("selecting openpgp failed: %s\n", gpg_strerror (rc));
              break;
            }
        }

      if (!rc && is_status_enabled () && info.serialno)
        {
          char *buf;

          buf = xasprintf ("3 %s", info.serialno);
          write_status_text (STATUS_CARDCTRL, buf);
          xfree (buf);
        }

      agent_release_card_info (&info);

      if (!rc)
        did_early_card_test = 1;
    }


  return rc;
}


/* Return a new malloced string by unescaping the string S.  Escaping
   is percent escaping and '+'/space mapping.  A binary nul will
   silently be replaced by a 0xFF.  Function returns NULL to indicate
   an out of memory status. */
static char *
unescape_status_string (const unsigned char *s)
{
  return percent_plus_unescape (s, 0xff);
}


/* Take a 20 byte hexencoded string and put it into the the provided
   20 byte buffer FPR in binary format. */
static int
unhexify_fpr (const char *hexstr, unsigned char *fpr)
{
  const char *s;
  int n;

  for (s=hexstr, n=0; hexdigitp (s); s++, n++)
    ;
  if (*s || (n != 40))
    return 0; /* no fingerprint (invalid or wrong length). */
  for (s=hexstr, n=0; *s; s += 2, n++)
    fpr[n] = xtoi_2 (s);
  return 1; /* okay */
}

/* Take the serial number from LINE and return it verbatim in a newly
   allocated string.  We make sure that only hex characters are
   returned. */
static char *
store_serialno (const char *line)
{
  const char *s;
  char *p;

  for (s=line; hexdigitp (s); s++)
    ;
  p = xtrymalloc (s + 1 - line);
  if (p)
    {
      memcpy (p, line, s-line);
      p[s-line] = 0;
    }
  return p;
}



/* This is a dummy data line callback.  */
static gpg_error_t
dummy_data_cb (void *opaque, const void *buffer, size_t length)
{
  (void)opaque;
  (void)buffer;
  (void)length;
  return 0;
}

/* A simple callback used to return the serialnumber of a card.  */
static gpg_error_t
get_serialno_cb (void *opaque, const char *line)
{
  char **serialno = opaque;
  const char *keyword = line;
  const char *s;
  int keywordlen, n;

  for (keywordlen=0; *line && !spacep (line); line++, keywordlen++)
    ;
  while (spacep (line))
    line++;

  if (keywordlen == 8 && !memcmp (keyword, "SERIALNO", keywordlen))
    {
      if (*serialno)
        return gpg_error (GPG_ERR_CONFLICT); /* Unexpected status line. */
      for (n=0,s=line; hexdigitp (s); s++, n++)
        ;
      if (!n || (n&1)|| !(spacep (s) || !*s) )
        return gpg_error (GPG_ERR_ASS_PARAMETER);
      *serialno = xtrymalloc (n+1);
      if (!*serialno)
        return out_of_core ();
      memcpy (*serialno, line, n);
      (*serialno)[n] = 0;
    }

  return 0;
}


/* This is the default inquiry callback.  It mainly handles the
   Pinentry notifications.  */
static gpg_error_t
default_inq_cb (void *opaque, const char *line)
{
  (void)opaque;

  if (!strncmp (line, "PINENTRY_LAUNCHED", 17) && (line[17]==' '||!line[17]))
    {
      /* There is no working server mode yet thus we use
         AllowSetForegroundWindow window right here.  We might want to
         do this anyway in case gpg is called on the console. */
      gnupg_allow_set_foregound_window ((pid_t)strtoul (line+17, NULL, 10));
      /* We do not pass errors to avoid breaking other code.  */
    }
  else
    log_debug ("ignoring gpg-agent inquiry `%s'\n", line);

  return 0;
}



/* Release the card info structure INFO. */
void
agent_release_card_info (struct agent_card_info_s *info)
{
  if (!info)
    return;

  xfree (info->serialno); info->serialno = NULL;
  xfree (info->apptype); info->apptype = NULL;
  xfree (info->disp_name); info->disp_name = NULL;
  xfree (info->disp_lang); info->disp_lang = NULL;
  xfree (info->pubkey_url); info->pubkey_url = NULL;
  xfree (info->login_data); info->login_data = NULL;
  info->cafpr1valid = info->cafpr2valid = info->cafpr3valid = 0;
  info->fpr1valid = info->fpr2valid = info->fpr3valid = 0;
}

static gpg_error_t
learn_status_cb (void *opaque, const char *line)
{
  struct agent_card_info_s *parm = opaque;
  const char *keyword = line;
  int keywordlen;
  int i;

  for (keywordlen=0; *line && !spacep (line); line++, keywordlen++)
    ;
  while (spacep (line))
    line++;

  if (keywordlen == 8 && !memcmp (keyword, "SERIALNO", keywordlen))
    {
      xfree (parm->serialno);
      parm->serialno = store_serialno (line);
      parm->is_v2 = (strlen (parm->serialno) >= 16
                     && xtoi_2 (parm->serialno+12) >= 2 );
    }
  else if (keywordlen == 7 && !memcmp (keyword, "APPTYPE", keywordlen))
    {
      xfree (parm->apptype);
      parm->apptype = unescape_status_string (line);
    }
  else if (keywordlen == 9 && !memcmp (keyword, "DISP-NAME", keywordlen))
    {
      xfree (parm->disp_name);
      parm->disp_name = unescape_status_string (line);
    }
  else if (keywordlen == 9 && !memcmp (keyword, "DISP-LANG", keywordlen))
    {
      xfree (parm->disp_lang);
      parm->disp_lang = unescape_status_string (line);
    }
  else if (keywordlen == 8 && !memcmp (keyword, "DISP-SEX", keywordlen))
    {
      parm->disp_sex = *line == '1'? 1 : *line == '2' ? 2: 0;
    }
  else if (keywordlen == 10 && !memcmp (keyword, "PUBKEY-URL", keywordlen))
    {
      xfree (parm->pubkey_url);
      parm->pubkey_url = unescape_status_string (line);
    }
  else if (keywordlen == 10 && !memcmp (keyword, "LOGIN-DATA", keywordlen))
    {
      xfree (parm->login_data);
      parm->login_data = unescape_status_string (line);
    }
  else if (keywordlen == 11 && !memcmp (keyword, "SIG-COUNTER", keywordlen))
    {
      parm->sig_counter = strtoul (line, NULL, 0);
    }
  else if (keywordlen == 10 && !memcmp (keyword, "CHV-STATUS", keywordlen))
    {
      char *p, *buf;

      buf = p = unescape_status_string (line);
      if (buf)
        {
          while (spacep (p))
            p++;
          parm->chv1_cached = atoi (p);
          while (*p && !spacep (p))
            p++;
          while (spacep (p))
            p++;
          for (i=0; *p && i < 3; i++)
            {
              parm->chvmaxlen[i] = atoi (p);
              while (*p && !spacep (p))
                p++;
              while (spacep (p))
                p++;
            }
          for (i=0; *p && i < 3; i++)
            {
              parm->chvretry[i] = atoi (p);
              while (*p && !spacep (p))
                p++;
              while (spacep (p))
                p++;
            }
          xfree (buf);
        }
    }
  else if (keywordlen == 6 && !memcmp (keyword, "EXTCAP", keywordlen))
    {
      char *p, *p2, *buf;
      int abool;

      buf = p = unescape_status_string (line);
      if (buf)
        {
          for (p = strtok (buf, " "); p; p = strtok (NULL, " "))
            {
              p2 = strchr (p, '=');
              if (p2)
                {
                  *p2++ = 0;
                  abool = (*p2 == '1');
                  if (!strcmp (p, "ki"))
                    parm->extcap.ki = abool;
                  else if (!strcmp (p, "aac"))
                    parm->extcap.aac = abool;
                }
            }
          xfree (buf);
        }
    }
  else if (keywordlen == 7 && !memcmp (keyword, "KEY-FPR", keywordlen))
    {
      int no = atoi (line);
      while (*line && !spacep (line))
        line++;
      while (spacep (line))
        line++;
      if (no == 1)
        parm->fpr1valid = unhexify_fpr (line, parm->fpr1);
      else if (no == 2)
        parm->fpr2valid = unhexify_fpr (line, parm->fpr2);
      else if (no == 3)
        parm->fpr3valid = unhexify_fpr (line, parm->fpr3);
    }
  else if (keywordlen == 8 && !memcmp (keyword, "KEY-TIME", keywordlen))
    {
      int no = atoi (line);
      while (* line && !spacep (line))
        line++;
      while (spacep (line))
        line++;
      if (no == 1)
        parm->fpr1time = strtoul (line, NULL, 10);
      else if (no == 2)
        parm->fpr2time = strtoul (line, NULL, 10);
      else if (no == 3)
        parm->fpr3time = strtoul (line, NULL, 10);
    }
  else if (keywordlen == 6 && !memcmp (keyword, "CA-FPR", keywordlen))
    {
      int no = atoi (line);
      while (*line && !spacep (line))
        line++;
      while (spacep (line))
        line++;
      if (no == 1)
        parm->cafpr1valid = unhexify_fpr (line, parm->cafpr1);
      else if (no == 2)
        parm->cafpr2valid = unhexify_fpr (line, parm->cafpr2);
      else if (no == 3)
        parm->cafpr3valid = unhexify_fpr (line, parm->cafpr3);
    }
  else if (keywordlen == 8 && !memcmp (keyword, "KEY-ATTR", keywordlen))
    {
      int keyno, algo, nbits;

      sscanf (line, "%d %d %d", &keyno, &algo, &nbits);
      keyno--;
      if (keyno >= 0 && keyno < DIM (parm->key_attr))
        {
          parm->key_attr[keyno].algo = algo;
          parm->key_attr[keyno].nbits = nbits;
        }
    }

  return 0;
}

/* Call the agent to learn about a smartcard */
int
agent_learn (struct agent_card_info_s *info)
{
  int rc;

  rc = start_agent (NULL, 1);
  if (rc)
    return rc;

  /* Send the serialno command to initialize the connection.  We don't
     care about the data returned.  If the card has already been
     initialized, this is a very fast command.  The main reason we
     need to do this here is to handle a card removed case so that an
     "l" command in --card-edit can be used to show ta newly inserted
     card.  We request the openpgp card because that is what we
     expect. */
  rc = assuan_transact (agent_ctx, "SCD SERIALNO openpgp",
                        NULL, NULL, NULL, NULL, NULL, NULL);
  if (rc)
    return rc;


  memset (info, 0, sizeof *info);
  rc = assuan_transact (agent_ctx, "SCD LEARN --force",
                        dummy_data_cb, NULL, default_inq_cb, NULL,
                        learn_status_cb, info);
  /* Also try to get the key attributes.  */
  if (!rc)
    agent_scd_getattr ("KEY-ATTR", info);

  return rc;
}

/* Call the agent to retrieve a data object.  This function returns
   the data in the same structure as used by the learn command.  It is
   allowed to update such a structure using this commmand. */
int
agent_scd_getattr (const char *name, struct agent_card_info_s *info)
{
  int rc;
  char line[ASSUAN_LINELENGTH];

  if (!*name)
    return gpg_error (GPG_ERR_INV_VALUE);

  /* We assume that NAME does not need escaping. */
  if (12 + strlen (name) > DIM(line)-1)
    return gpg_error (GPG_ERR_TOO_LARGE);
  stpcpy (stpcpy (line, "SCD GETATTR "), name);

  rc = start_agent (NULL, 1);
  if (rc)
    return rc;

  rc = assuan_transact (agent_ctx, line, NULL, NULL, default_inq_cb, NULL,
                        learn_status_cb, info);

  return rc;
}


/* Send an setattr command to the SCdaemon.  SERIALNO is not actually
   used here but required by gpg 1.4's implementation of this code in
   cardglue.c. */
int
agent_scd_setattr (const char *name,
                   const unsigned char *value, size_t valuelen,
                   const char *serialno)
{
  int rc;
  char line[ASSUAN_LINELENGTH];
  char *p;

  (void)serialno;

  if (!*name || !valuelen)
    return gpg_error (GPG_ERR_INV_VALUE);

  /* We assume that NAME does not need escaping. */
  if (12 + strlen (name) > DIM(line)-1)
    return gpg_error (GPG_ERR_TOO_LARGE);

  p = stpcpy (stpcpy (line, "SCD SETATTR "), name);
  *p++ = ' ';
  for (; valuelen; value++, valuelen--)
    {
      if (p >= line + DIM(line)-5 )
        return gpg_error (GPG_ERR_TOO_LARGE);
      if (*value < ' ' || *value == '+' || *value == '%')
        {
          sprintf (p, "%%%02X", *value);
          p += 3;
        }
      else if (*value == ' ')
        *p++ = '+';
      else
        *p++ = *value;
    }
  *p = 0;

  rc = start_agent (NULL, 1);
  if (!rc)
    {
      rc = assuan_transact (agent_ctx, line, NULL, NULL,
                            default_inq_cb, NULL, NULL, NULL);
    }

  status_sc_op_failure (rc);
  return rc;
}



/* Handle a CERTDATA inquiry.  Note, we only send the data,
   assuan_transact takes care of flushing and writing the END
   command. */
static gpg_error_t
inq_writecert_parms (void *opaque, const char *line)
{
  int rc;
  struct writecert_parm_s *parm = opaque;

  if (!strncmp (line, "CERTDATA", 8) && (line[8]==' '||!line[8]))
    {
      rc = assuan_send_data (parm->ctx, parm->certdata, parm->certdatalen);
    }
  else
    rc = default_inq_cb (opaque, line);

  return rc;
}


/* Send a WRITECERT command to the SCdaemon. */
int
agent_scd_writecert (const char *certidstr,
                     const unsigned char *certdata, size_t certdatalen)
{
  int rc;
  char line[ASSUAN_LINELENGTH];
  struct writecert_parm_s parms;

  rc = start_agent (NULL, 1);
  if (rc)
    return rc;

  memset (&parms, 0, sizeof parms);

  snprintf (line, DIM(line)-1, "SCD WRITECERT %s", certidstr);
  line[DIM(line)-1] = 0;
  parms.ctx = agent_ctx;
  parms.certdata = certdata;
  parms.certdatalen = certdatalen;

  rc = assuan_transact (agent_ctx, line, NULL, NULL,
                        inq_writecert_parms, &parms, NULL, NULL);

  return rc;
}



/* Handle a KEYDATA inquiry.  Note, we only send the data,
   assuan_transact takes care of flushing and writing the end */
static gpg_error_t
inq_writekey_parms (void *opaque, const char *line)
{
  int rc;
  struct writekey_parm_s *parm = opaque;

  if (!strncmp (line, "KEYDATA", 7) && (line[7]==' '||!line[7]))
    {
      rc = assuan_send_data (parm->ctx, parm->keydata, parm->keydatalen);
    }
  else
    rc = default_inq_cb (opaque, line);

  return rc;
}


/* Send a WRITEKEY command to the SCdaemon. */
int
agent_scd_writekey (int keyno, const char *serialno,
                    const unsigned char *keydata, size_t keydatalen)
{
  int rc;
  char line[ASSUAN_LINELENGTH];
  struct writekey_parm_s parms;

  (void)serialno;

  rc = start_agent (NULL, 1);
  if (rc)
    return rc;

  memset (&parms, 0, sizeof parms);

  snprintf (line, DIM(line)-1, "SCD WRITEKEY --force OPENPGP.%d", keyno);
  line[DIM(line)-1] = 0;
  parms.ctx = agent_ctx;
  parms.keydata = keydata;
  parms.keydatalen = keydatalen;

  rc = assuan_transact (agent_ctx, line, NULL, NULL,
                        inq_writekey_parms, &parms, NULL, NULL);

  status_sc_op_failure (rc);
  return rc;
}



static gpg_error_t
scd_genkey_cb_append_savedbytes (struct scd_genkey_parm_s *parm,
                                 const char *line)
{
  gpg_error_t err = 0;
  char *p;

  if (!parm->savedbytes)
    {
      parm->savedbytes = xtrystrdup (line);
      if (!parm->savedbytes)
        err = gpg_error_from_syserror ();
    }
  else
    {
      p = xtrymalloc (strlen (parm->savedbytes) + strlen (line) + 1);
      if (!p)
        err = gpg_error_from_syserror ();
      else
        {
          strcpy (stpcpy (p, parm->savedbytes), line);
          xfree (parm->savedbytes);
          parm->savedbytes = p;
        }
    }

  return err;
}

/* Status callback for the SCD GENKEY command. */
static gpg_error_t
scd_genkey_cb (void *opaque, const char *line)
{
  struct scd_genkey_parm_s *parm = opaque;
  const char *keyword = line;
  int keywordlen;
  gpg_error_t rc = 0;

  for (keywordlen=0; *line && !spacep (line); line++, keywordlen++)
    ;
  while (spacep (line))
    line++;

  if (keywordlen == 7 && !memcmp (keyword, "KEY-FPR", keywordlen))
    {
      parm->cgk->fprvalid = unhexify_fpr (line, parm->cgk->fpr);
    }
  else if (keywordlen == 8 && !memcmp (keyword, "KEY-DATA", keywordlen))
    {
      gcry_mpi_t a;
      const char *name = line;

      while (*line && !spacep (line))
        line++;
      while (spacep (line))
        line++;

      if (*name == '-' && spacep (name+1))
        rc = scd_genkey_cb_append_savedbytes (parm, line);
      else
        {
          if (parm->savedbytes)
            {
              rc = scd_genkey_cb_append_savedbytes (parm, line);
              if (!rc)
                rc = gcry_mpi_scan (&a, GCRYMPI_FMT_HEX,
                                    parm->savedbytes, 0, NULL);
            }
          else
            rc = gcry_mpi_scan (&a, GCRYMPI_FMT_HEX, line, 0, NULL);
          if (rc)
            log_error ("error parsing received key data: %s\n",
                       gpg_strerror (rc));
          else if (*name == 'n' && spacep (name+1))
            parm->cgk->n = a;
          else if (*name == 'e' && spacep (name+1))
            parm->cgk->e = a;
          else
            {
              log_info ("unknown parameter name in received key data\n");
              gcry_mpi_release (a);
              rc = gpg_error (GPG_ERR_INV_PARAMETER);
            }

          xfree (parm->savedbytes);
          parm->savedbytes = NULL;
        }
    }
  else if (keywordlen == 14 && !memcmp (keyword,"KEY-CREATED-AT", keywordlen))
    {
      parm->cgk->created_at = (u32)strtoul (line, NULL, 10);
    }
  else if (keywordlen == 8 && !memcmp (keyword, "PROGRESS", keywordlen))
    {
      write_status_text (STATUS_PROGRESS, line);
    }

  return rc;
}

/* Send a GENKEY command to the SCdaemon.  SERIALNO is not used in
   this implementation.  If CREATEDATE is not 0, it will be passed to
   SCDAEMON so that the key is created with this timestamp.  INFO will
   receive information about the generated key.  */
int
agent_scd_genkey (struct agent_card_genkey_s *info, int keyno, int force,
                  const char *serialno, u32 createtime)
{
  int rc;
  char line[ASSUAN_LINELENGTH];
  gnupg_isotime_t tbuf;
  struct scd_genkey_parm_s parms;

  (void)serialno;

  memset (&parms, 0, sizeof parms);
  parms.cgk = info;

  rc = start_agent (NULL, 1);
  if (rc)
    return rc;

  if (createtime)
    epoch2isotime (tbuf, createtime);
  else
    *tbuf = 0;

  snprintf (line, DIM(line)-1, "SCD GENKEY %s%s %s %d",
            *tbuf? "--timestamp=":"", tbuf,
            force? "--force":"",
            keyno);
  line[DIM(line)-1] = 0;

  memset (info, 0, sizeof *info);
  rc = assuan_transact (agent_ctx, line,
                        NULL, NULL, default_inq_cb, NULL,
                        scd_genkey_cb, &parms);

  xfree (parms.savedbytes);

  status_sc_op_failure (rc);
  return rc;
}




/* Issue an SCD SERIALNO openpgp command and if SERIALNO is not NULL
   ask the user to insert the requested card.  */
gpg_error_t
select_openpgp (const char *serialno)
{
  gpg_error_t err;

  /* Send the serialno command to initialize the connection.  Without
     a given S/N we don't care about the data returned.  If the card
     has already been initialized, this is a very fast command.  We
     request the openpgp card because that is what we expect.

     Note that an opt.limit_card_insert_tries of 1 means: No tries at
     all whereas 0 means do not limit the number of tries.  Due to the
     sue of a pinentry prompt with a cancel option we use it here in a
     boolean sense.  */
  if (!serialno || opt.limit_card_insert_tries == 1)
    err = assuan_transact (agent_ctx, "SCD SERIALNO openpgp",
                           NULL, NULL, NULL, NULL, NULL, NULL);
  else
    {
      char *this_sn = NULL;
      char *desc;
      int ask;
      char *want_sn;
      char *p;

      want_sn = xtrystrdup (serialno);
      if (!want_sn)
        return gpg_error_from_syserror ();
      p = strchr (want_sn, '/');
      if (p)
        *p = 0;

      do
        {
          ask = 0;
          err = assuan_transact (agent_ctx, "SCD SERIALNO openpgp",
                                 NULL, NULL, NULL, NULL,
                                 get_serialno_cb, &this_sn);
          if (gpg_err_code (err) == GPG_ERR_CARD_NOT_PRESENT)
            ask = 1;
          else if (gpg_err_code (err) == GPG_ERR_NOT_SUPPORTED)
            ask = 2;
          else if (err)
            ;
          else if (this_sn)
            {
              if (strcmp (want_sn, this_sn))
                ask = 2;
            }

          xfree (this_sn);
          this_sn = NULL;

          if (ask)
            {
              char *formatted = NULL;
              char *ocodeset = i18n_switchto_utf8 ();

              if (!strncmp (want_sn, "D27600012401", 12)
                  && strlen (want_sn) == 32 )
                formatted = xtryasprintf ("(%.4s) %.8s",
                                          want_sn + 16, want_sn + 20);

              err = 0;
              desc = xtryasprintf
                ("%s:\n\n"
                 "  \"%s\"",
                 ask == 1
                 ? _("Please insert the card with serial number")
                 : _("Please remove the current card and "
                     "insert the one with serial number"),
                 formatted? formatted : want_sn);
              if (!desc)
                err = gpg_error_from_syserror ();
              xfree (formatted);
              i18n_switchback (ocodeset);
              if (!err)
                err = gpg_agent_get_confirmation (desc);
              xfree (desc);
            }
        }
      while (ask && !err);
      xfree (want_sn);
    }

  return err;
}



static gpg_error_t
membuf_data_cb (void *opaque, const void *buffer, size_t length)
{
  membuf_t *data = opaque;

  if (buffer)
    put_membuf (data, buffer, length);
  return 0;
}




/* Send a READCERT command to the SCdaemon. */
int
agent_scd_readcert (const char *certidstr,
                    void **r_buf, size_t *r_buflen)
{
  int rc;
  char line[ASSUAN_LINELENGTH];
  membuf_t data;
  size_t len;

  *r_buf = NULL;
  rc = start_agent (NULL, 1);
  if (rc)
    return rc;

  init_membuf (&data, 2048);

  snprintf (line, DIM(line)-1, "SCD READCERT %s", certidstr);
  line[DIM(line)-1] = 0;
  rc = assuan_transact (agent_ctx, line,
                        membuf_data_cb, &data,
                        default_inq_cb, NULL, NULL, NULL);
  if (rc)
    {
      xfree (get_membuf (&data, &len));
      return rc;
    }
  *r_buf = get_membuf (&data, r_buflen);
  if (!*r_buf)
    return gpg_error (GPG_ERR_ENOMEM);

  return 0;
}



/* Change the PIN of an OpenPGP card or reset the retry counter.
   CHVNO 1: Change the PIN
         2: For v1 cards: Same as 1.
            For v2 cards: Reset the PIN using the Reset Code.
         3: Change the admin PIN
       101: Set a new PIN and reset the retry counter
       102: For v1 cars: Same as 101.
            For v2 cards: Set a new Reset Code.
   SERIALNO is not used.
 */
int
agent_scd_change_pin (int chvno, const char *serialno)
{
  int rc;
  char line[ASSUAN_LINELENGTH];
  const char *reset = "";

  (void)serialno;

  if (chvno >= 100)
    reset = "--reset";
  chvno %= 100;

  rc = start_agent (NULL, 1);
  if (rc)
    return rc;

  snprintf (line, DIM(line)-1, "SCD PASSWD %s %d", reset, chvno);
  line[DIM(line)-1] = 0;
  rc = assuan_transact (agent_ctx, line, NULL, NULL,
                        default_inq_cb, NULL, NULL, NULL);
  status_sc_op_failure (rc);
  return rc;
}


/* Perform a CHECKPIN operation.  SERIALNO should be the serial
   number of the card - optionally followed by the fingerprint;
   however the fingerprint is ignored here. */
int
agent_scd_checkpin  (const char *serialno)
{
  int rc;
  char line[ASSUAN_LINELENGTH];

  rc = start_agent (NULL, 1);
  if (rc)
    return rc;

  snprintf (line, DIM(line)-1, "SCD CHECKPIN %s", serialno);
  line[DIM(line)-1] = 0;
  rc = assuan_transact (agent_ctx, line,
                        NULL, NULL,
                        default_inq_cb, NULL, NULL, NULL);
  status_sc_op_failure (rc);
  return rc;
}


/* Dummy function, only used by the gpg 1.4 implementation. */
void
agent_clear_pin_cache (const char *sn)
{
  (void)sn;
}




/* Note: All strings shall be UTF-8. On success the caller needs to
   free the string stored at R_PASSPHRASE. On error NULL will be
   stored at R_PASSPHRASE and an appropriate fpf error code
   returned. */
gpg_error_t
agent_get_passphrase (const char *cache_id,
                      const char *err_msg,
                      const char *prompt,
                      const char *desc_msg,
                      int repeat,
                      int check,
                      char **r_passphrase)
{
  int rc;
  char line[ASSUAN_LINELENGTH];
  char *arg1 = NULL;
  char *arg2 = NULL;
  char *arg3 = NULL;
  char *arg4 = NULL;
  membuf_t data;

  *r_passphrase = NULL;

  rc = start_agent (NULL, 0);
  if (rc)
    return rc;

  /* Check that the gpg-agent understands the repeat option.  */
  if (assuan_transact (agent_ctx,
                       "GETINFO cmd_has_option GET_PASSPHRASE repeat",
                       NULL, NULL, NULL, NULL, NULL, NULL))
    return gpg_error (GPG_ERR_NOT_SUPPORTED);

  if (cache_id && *cache_id)
    if (!(arg1 = percent_plus_escape (cache_id)))
      goto no_mem;
  if (err_msg && *err_msg)
    if (!(arg2 = percent_plus_escape (err_msg)))
      goto no_mem;
  if (prompt && *prompt)
    if (!(arg3 = percent_plus_escape (prompt)))
      goto no_mem;
  if (desc_msg && *desc_msg)
    if (!(arg4 = percent_plus_escape (desc_msg)))
      goto no_mem;

  snprintf (line, DIM(line)-1,
            "GET_PASSPHRASE --data --repeat=%d%s -- %s %s %s %s",
            repeat,
            check? " --check --qualitybar":"",
            arg1? arg1:"X",
            arg2? arg2:"X",
            arg3? arg3:"X",
            arg4? arg4:"X");
  line[DIM(line)-1] = 0;
  xfree (arg1);
  xfree (arg2);
  xfree (arg3);
  xfree (arg4);

  init_membuf_secure (&data, 64);
  rc = assuan_transact (agent_ctx, line,
                        membuf_data_cb, &data,
                        default_inq_cb, NULL, NULL, NULL);

  if (rc)
    xfree (get_membuf (&data, NULL));
  else
    {
      put_membuf (&data, "", 1);
      *r_passphrase = get_membuf (&data, NULL);
      if (!*r_passphrase)
        rc = gpg_error_from_syserror ();
    }
  return rc;
 no_mem:
  rc = gpg_error_from_syserror ();
  xfree (arg1);
  xfree (arg2);
  xfree (arg3);
  xfree (arg4);
  return rc;
}


gpg_error_t
agent_clear_passphrase (const char *cache_id)
{
  int rc;
  char line[ASSUAN_LINELENGTH];

  if (!cache_id || !*cache_id)
    return 0;

  rc = start_agent (NULL, 0);
  if (rc)
    return rc;

  snprintf (line, DIM(line)-1, "CLEAR_PASSPHRASE %s", cache_id);
  line[DIM(line)-1] = 0;
  return assuan_transact (agent_ctx, line, NULL, NULL,
                          default_inq_cb, NULL, NULL, NULL);
}


/* Ask the agent to pop up a confirmation dialog with the text DESC
   and an okay and cancel button. */
gpg_error_t
gpg_agent_get_confirmation (const char *desc)
{
  int rc;
  char *tmp;
  char line[ASSUAN_LINELENGTH];

  rc = start_agent (NULL, 0);
  if (rc)
    return rc;

  tmp = percent_plus_escape (desc);
  if (!tmp)
    return gpg_error_from_syserror ();
  snprintf (line, DIM(line)-1, "GET_CONFIRMATION %s", tmp);
  line[DIM(line)-1] = 0;
  xfree (tmp);

  rc = assuan_transact (agent_ctx, line, NULL, NULL,
                        default_inq_cb, NULL, NULL, NULL);
  return rc;
}


/* Return the S2K iteration count as computed by gpg-agent.  */
gpg_error_t
agent_get_s2k_count (unsigned long *r_count)
{
  gpg_error_t err;
  membuf_t data;
  char *buf;

  *r_count = 0;

  err = start_agent (NULL, 0);
  if (err)
    return err;

  init_membuf (&data, 32);
  err = assuan_transact (agent_ctx, "GETINFO s2k_count",
                        membuf_data_cb, &data,
                        NULL, NULL, NULL, NULL);
  if (err)
    xfree (get_membuf (&data, NULL));
  else
    {
      put_membuf (&data, "", 1);
      buf = get_membuf (&data, NULL);
      if (!buf)
        err = gpg_error_from_syserror ();
      else
        {
          *r_count = strtoul (buf, NULL, 10);
          xfree (buf);
        }
    }
  return err;
}



/* Ask the agent whether a secret key for the given public key is
   available.  Returns 0 if available.  */
gpg_error_t
agent_probe_secret_key (ctrl_t ctrl, PKT_public_key *pk)
{
  gpg_error_t err;
  char line[ASSUAN_LINELENGTH];
  char *hexgrip;

  err = start_agent (ctrl, 0);
  if (err)
    return err;

  err = hexkeygrip_from_pk (pk, &hexgrip);
  if (err)
    return err;

  snprintf (line, sizeof line, "HAVEKEY %s", hexgrip);
  xfree (hexgrip);

  err = assuan_transact (agent_ctx, line, NULL, NULL, NULL, NULL, NULL, NULL);
  return err;
}

/* Ask the agent whether a secret key is availabale for any of the
   keys (primary or sub) in KEYBLOCK.  Returns 0 if available.  */
gpg_error_t
agent_probe_any_secret_key (ctrl_t ctrl, kbnode_t keyblock)
{
  gpg_error_t err;
  char line[ASSUAN_LINELENGTH];
  char *p;
  kbnode_t kbctx, node;
  int nkeys;
  unsigned char grip[20];

  err = start_agent (ctrl, 0);
  if (err)
    return err;

  err = gpg_error (GPG_ERR_NO_SECKEY); /* Just in case no key was
                                          found in KEYBLOCK.  */
  p = stpcpy (line, "HAVEKEY");
  for (kbctx=NULL, nkeys=0; (node = walk_kbnode (keyblock, &kbctx, 0)); )
    if (node->pkt->pkttype == PKT_PUBLIC_KEY
        || node->pkt->pkttype == PKT_PUBLIC_SUBKEY
        || node->pkt->pkttype == PKT_SECRET_KEY
        || node->pkt->pkttype == PKT_SECRET_SUBKEY)
      {
        if (nkeys && ((p - line) + 41) > (ASSUAN_LINELENGTH - 2))
          {
            err = assuan_transact (agent_ctx, line,
                                   NULL, NULL, NULL, NULL, NULL, NULL);
            if (err != gpg_err_code (GPG_ERR_NO_SECKEY))
              break; /* Seckey available or unexpected error - ready.  */
            p = stpcpy (line, "HAVEKEY");
            nkeys = 0;
          }

        err = keygrip_from_pk (node->pkt->pkt.public_key, grip);
        if (err)
          return err;
        *p++ = ' ';
        bin2hex (grip, 20, p);
        p += 40;
        nkeys++;
      }

  if (!err && nkeys)
    err = assuan_transact (agent_ctx, line,
                           NULL, NULL, NULL, NULL, NULL, NULL);

  return err;
}



static gpg_error_t
keyinfo_status_cb (void *opaque, const char *line)
{
  char **serialno = opaque;
  const char *s, *s2;

  if (!strncmp (line, "KEYINFO ", 8) && !*serialno)
    {
      s = strchr (line+8, ' ');
      if (s && s[1] == 'T' && s[2] == ' ' && s[3])
        {
          s += 3;
          s2 = strchr (s, ' ');
          if ( s2 > s )
            {
              *serialno = xtrymalloc ((s2 - s)+1);
              if (*serialno)
                {
                  memcpy (*serialno, s, s2 - s);
                  (*serialno)[s2 - s] = 0;
                }
            }
        }
    }
  return 0;
}


/* Return the serial number for a secret key.  If the returned serial
   number is NULL, the key is not stored on a smartcard.  Caller needs
   to free R_SERIALNO.  */
gpg_error_t
agent_get_keyinfo (ctrl_t ctrl, const char *hexkeygrip, char **r_serialno)
{
  gpg_error_t err;
  char line[ASSUAN_LINELENGTH];
  char *serialno = NULL;

  *r_serialno = NULL;

  err = start_agent (ctrl, 0);
  if (err)
    return err;

  if (!hexkeygrip || strlen (hexkeygrip) != 40)
    return gpg_error (GPG_ERR_INV_VALUE);

  snprintf (line, DIM(line)-1, "KEYINFO %s", hexkeygrip);
  line[DIM(line)-1] = 0;

  err = assuan_transact (agent_ctx, line, NULL, NULL, NULL, NULL,
                         keyinfo_status_cb, &serialno);
  if (!err && serialno)
    {
      /* Sanity check for bad characters.  */
      if (strpbrk (serialno, ":\n\r"))
        err = GPG_ERR_INV_VALUE;
    }
  if (err)
    xfree (serialno);
  else
    *r_serialno = serialno;
  return err;
}


/* Status callback for agent_import_key, agent_export_key and
   agent_genkey.  */
static gpg_error_t
cache_nonce_status_cb (void *opaque, const char *line)
{
  struct cache_nonce_parm_s *parm = opaque;
  const char *keyword = line;
  int keywordlen;

  for (keywordlen=0; *line && !spacep (line); line++, keywordlen++)
    ;
  while (spacep (line))
    line++;

  if (keywordlen == 11 && !memcmp (keyword, "CACHE_NONCE", keywordlen))
    {
      if (parm->cache_nonce_addr)
        {
          xfree (*parm->cache_nonce_addr);
          *parm->cache_nonce_addr = xtrystrdup (line);
        }
    }
  else if (keywordlen == 12 && !memcmp (keyword, "PASSWD_NONCE", keywordlen))
    {
      if (parm->passwd_nonce_addr)
        {
          xfree (*parm->passwd_nonce_addr);
          *parm->passwd_nonce_addr = xtrystrdup (line);
        }
    }

  return 0;
}



/* Handle a KEYPARMS inquiry.  Note, we only send the data,
   assuan_transact takes care of flushing and writing the end */
static gpg_error_t
inq_genkey_parms (void *opaque, const char *line)
{
  struct genkey_parm_s *parm = opaque;
  gpg_error_t err;

  if (!strncmp (line, "KEYPARAM", 8) && (line[8]==' '||!line[8]))
    {
      err = assuan_send_data (parm->ctx,
                              parm->keyparms, strlen (parm->keyparms));
    }
  else
    err = default_inq_cb (parm->ctrl, line);

  return err;
}


/* Call the agent to generate a new key.  KEYPARMS is the usual
   S-expression giving the parameters of the key.  gpg-agent passes it
   gcry_pk_genkey.  If NO_PROTECTION is true the agent is advised not
   to protect the generated key. */
gpg_error_t
agent_genkey (ctrl_t ctrl, char **cache_nonce_addr,
              const char *keyparms, int no_protection, gcry_sexp_t *r_pubkey)
{
  gpg_error_t err;
  struct genkey_parm_s gk_parm;
  struct cache_nonce_parm_s cn_parm;
  membuf_t data;
  size_t len;
  unsigned char *buf;
  char line[ASSUAN_LINELENGTH];

  *r_pubkey = NULL;
  err = start_agent (ctrl, 0);
  if (err)
    return err;

  err = assuan_transact (agent_ctx, "RESET",
                         NULL, NULL, NULL, NULL, NULL, NULL);
  if (err)
    return err;

  init_membuf (&data, 1024);
  gk_parm.ctrl     = ctrl;
  gk_parm.ctx      = agent_ctx;
  gk_parm.keyparms = keyparms;
  snprintf (line, sizeof line, "GENKEY%s%s%s",
            no_protection? " --no-protection":"",
            cache_nonce_addr && *cache_nonce_addr? " ":"",
            cache_nonce_addr && *cache_nonce_addr? *cache_nonce_addr:"");
  cn_parm.cache_nonce_addr = cache_nonce_addr;
  cn_parm.passwd_nonce_addr = NULL;
  err = assuan_transact (agent_ctx, line,
                         membuf_data_cb, &data,
                         inq_genkey_parms, &gk_parm,
                         cache_nonce_status_cb, &cn_parm);
  if (err)
    {
      xfree (get_membuf (&data, &len));
      return err;
    }

  buf = get_membuf (&data, &len);
  if (!buf)
    err = gpg_error_from_syserror ();
  else
    {
      err = gcry_sexp_sscan (r_pubkey, NULL, buf, len);
      xfree (buf);
    }
  return err;
}




/* FIXME: Call the agent to read the public key part for a given keygrip.  If
   FROMCARD is true, the key is directly read from the current
   smartcard. In this case HEXKEYGRIP should be the keyID
   (e.g. OPENPGP.3). */
/* int */
/* agent_readkey (ctrl_t ctrl, int fromcard, const char *hexkeygrip, */
/*                ksba_sexp_t *r_pubkey) */
/* { */
/*   int rc; */
/*   membuf_t data; */
/*   size_t len; */
/*   unsigned char *buf; */
/*   char line[ASSUAN_LINELENGTH]; */

/*   *r_pubkey = NULL; */
/*   rc = start_agent (ctrl); */
/*   if (rc) */
/*     return rc; */

/*   rc = assuan_transact (agent_ctx, "RESET",NULL, NULL, NULL, NULL, NULL, NULL); */
/*   if (rc) */
/*     return rc; */

/*   snprintf (line, DIM(line)-1, "%sREADKEY %s", */
/*             fromcard? "SCD ":"", hexkeygrip); */
/*   line[DIM(line)-1] = 0; */

/*   init_membuf (&data, 1024); */
/*   rc = assuan_transact (agent_ctx, line, */
/*                         membuf_data_cb, &data,  */
/*                         default_inq_cb, ctrl, NULL, NULL); */
/*   if (rc) */
/*     { */
/*       xfree (get_membuf (&data, &len)); */
/*       return rc; */
/*     } */
/*   buf = get_membuf (&data, &len); */
/*   if (!buf) */
/*     return gpg_error (GPG_ERR_ENOMEM); */
/*   if (!gcry_sexp_canon_len (buf, len, NULL, NULL)) */
/*     { */
/*       xfree (buf); */
/*       return gpg_error (GPG_ERR_INV_SEXP); */
/*     } */
/*   *r_pubkey = buf; */
/*   return 0; */
/* } */



/* Call the agent to do a sign operation using the key identified by
   the hex string KEYGRIP.  DESC is a description of the key to be
   displayed if the agent needs to ask for the PIN.  DIGEST and
   DIGESTLEN is the hash value to sign and DIGESTALGO the algorithm id
   used to compute the digest.  If CACHE_NONCE is used the agent is
   advised to first try a passphrase associated with that nonce. */
gpg_error_t
agent_pksign (ctrl_t ctrl, const char *cache_nonce,
              const char *keygrip, const char *desc,
              unsigned char *digest, size_t digestlen, int digestalgo,
              gcry_sexp_t *r_sigval)
{
  gpg_error_t err;
  char line[ASSUAN_LINELENGTH];
  membuf_t data;

  *r_sigval = NULL;
  err = start_agent (ctrl, 0);
  if (err)
    return err;

  if (digestlen*2 + 50 > DIM(line))
    return gpg_error (GPG_ERR_GENERAL);

  err = assuan_transact (agent_ctx, "RESET",
                         NULL, NULL, NULL, NULL, NULL, NULL);
  if (err)
    return err;

  snprintf (line, DIM(line)-1, "SIGKEY %s", keygrip);
  line[DIM(line)-1] = 0;
  err = assuan_transact (agent_ctx, line, NULL, NULL, NULL, NULL, NULL, NULL);
  if (err)
    return err;

  if (desc)
    {
      snprintf (line, DIM(line)-1, "SETKEYDESC %s", desc);
      line[DIM(line)-1] = 0;
      err = assuan_transact (agent_ctx, line,
                            NULL, NULL, NULL, NULL, NULL, NULL);
      if (err)
        return err;
    }

  snprintf (line, sizeof line, "SETHASH %d ", digestalgo);
  bin2hex (digest, digestlen, line + strlen (line));
  err = assuan_transact (agent_ctx, line, NULL, NULL, NULL, NULL, NULL, NULL);
  if (err)
    return err;

  init_membuf (&data, 1024);

  snprintf (line, sizeof line, "PKSIGN%s%s",
            cache_nonce? " -- ":"",
            cache_nonce? cache_nonce:"");
  err = assuan_transact (agent_ctx, line,
                        membuf_data_cb, &data, default_inq_cb, ctrl,
                        NULL, NULL);
  if (err)
    xfree (get_membuf (&data, NULL));
  else
    {
      unsigned char *buf;
      size_t len;

      buf = get_membuf (&data, &len);
      if (!buf)
        err = gpg_error_from_syserror ();
      else
        {
          err = gcry_sexp_sscan (r_sigval, NULL, buf, len);
          xfree (buf);
        }
    }
  return err;
}



/* Handle a CIPHERTEXT inquiry.  Note, we only send the data,
   assuan_transact takes care of flushing and writing the END. */
static gpg_error_t
inq_ciphertext_cb (void *opaque, const char *line)
{
  struct cipher_parm_s *parm = opaque;
  int rc;

  if (!strncmp (line, "CIPHERTEXT", 10) && (line[10]==' '||!line[10]))
    {
      assuan_begin_confidential (parm->ctx);
      rc = assuan_send_data (parm->ctx, parm->ciphertext, parm->ciphertextlen);
      assuan_end_confidential (parm->ctx);
    }
  else
    rc = default_inq_cb (parm->ctrl, line);

  return rc;
}


/* Call the agent to do a decrypt operation using the key identified
   by the hex string KEYGRIP and the input data S_CIPHERTEXT.  On the
   success the decoded value is stored verbatim at R_BUF and its
   length at R_BUF; the callers needs to release it.  */
gpg_error_t
agent_pkdecrypt (ctrl_t ctrl, const char *keygrip, const char *desc,
                 gcry_sexp_t s_ciphertext,
                 unsigned char **r_buf, size_t *r_buflen)
{
  gpg_error_t err;
  char line[ASSUAN_LINELENGTH];
  membuf_t data;
  size_t n, len;
  char *p, *buf, *endp;

  if (!keygrip || strlen(keygrip) != 40 || !s_ciphertext || !r_buf || !r_buflen)
    return gpg_error (GPG_ERR_INV_VALUE);
  *r_buf = NULL;

  err = start_agent (ctrl, 0);
  if (err)
    return err;

  err = assuan_transact (agent_ctx, "RESET",
                         NULL, NULL, NULL, NULL, NULL, NULL);
  if (err)
    return err;

  snprintf (line, sizeof line, "SETKEY %s", keygrip);
  err = assuan_transact (agent_ctx, line, NULL, NULL, NULL, NULL, NULL, NULL);
  if (err)
    return err;

  if (desc)
    {
      snprintf (line, DIM(line)-1, "SETKEYDESC %s", desc);
      line[DIM(line)-1] = 0;
      err = assuan_transact (agent_ctx, line,
                            NULL, NULL, NULL, NULL, NULL, NULL);
      if (err)
        return err;
    }

  init_membuf_secure (&data, 1024);
  {
    struct cipher_parm_s parm;

    parm.ctrl = ctrl;
    parm.ctx = agent_ctx;
    err = make_canon_sexp (s_ciphertext, &parm.ciphertext, &parm.ciphertextlen);
    if (err)
      return err;
    err = assuan_transact (agent_ctx, "PKDECRYPT",
                           membuf_data_cb, &data,
                           inq_ciphertext_cb, &parm, NULL, NULL);
    xfree (parm.ciphertext);
  }
  if (err)
    {
      xfree (get_membuf (&data, &len));
      return err;
    }

  put_membuf (&data, "", 1); /* Make sure it is 0 terminated.  */
  buf = get_membuf (&data, &len);
  if (!buf)
    return gpg_error_from_syserror ();
  assert (len); /* (we forced Nul termination.)  */

  if (*buf != '(')
    {
      xfree (buf);
      return gpg_error (GPG_ERR_INV_SEXP);
    }

  if (len < 13 || memcmp (buf, "(5:value", 8) ) /* "(5:valueN:D)\0" */
    {
      xfree (buf);
      return gpg_error (GPG_ERR_INV_SEXP);
    }
  len -= 11;   /* Count only the data of the second part. */
  p = buf + 8; /* Skip leading parenthesis and the value tag. */

  n = strtoul (p, &endp, 10);
  if (!n || *endp != ':')
    {
      xfree (buf);
      return gpg_error (GPG_ERR_INV_SEXP);
    }
  endp++;
  if (endp-p+n > len)
    {
      xfree (buf);
      return gpg_error (GPG_ERR_INV_SEXP); /* Oops: Inconsistent S-Exp. */
    }

  memmove (buf, endp, n);

  *r_buflen = n;
  *r_buf = buf;
  return 0;
}



/* Retrieve a key encryption key from the agent.  With FOREXPORT true
   the key shall be used for export, with false for import.  On success
   the new key is stored at R_KEY and its length at R_KEKLEN.  */
gpg_error_t
agent_keywrap_key (ctrl_t ctrl, int forexport, void **r_kek, size_t *r_keklen)
{
  gpg_error_t err;
  membuf_t data;
  size_t len;
  unsigned char *buf;
  char line[ASSUAN_LINELENGTH];

  *r_kek = NULL;
  err = start_agent (ctrl, 0);
  if (err)
    return err;

  snprintf (line, DIM(line)-1, "KEYWRAP_KEY %s",
            forexport? "--export":"--import");

  init_membuf_secure (&data, 64);
  err = assuan_transact (agent_ctx, line,
                         membuf_data_cb, &data,
                         default_inq_cb, ctrl, NULL, NULL);
  if (err)
    {
      xfree (get_membuf (&data, &len));
      return err;
    }
  buf = get_membuf (&data, &len);
  if (!buf)
    return gpg_error_from_syserror ();
  *r_kek = buf;
  *r_keklen = len;
  return 0;
}



/* Handle the inquiry for an IMPORT_KEY command.  */
static gpg_error_t
inq_import_key_parms (void *opaque, const char *line)
{
  struct import_key_parm_s *parm = opaque;
  gpg_error_t err;

  if (!strncmp (line, "KEYDATA", 7) && (line[7]==' '||!line[7]))
    {
      err = assuan_send_data (parm->ctx, parm->key, parm->keylen);
    }
  else
    err = default_inq_cb (parm->ctrl, line);

  return err;
}


/* Call the agent to import a key into the agent.  */
gpg_error_t
agent_import_key (ctrl_t ctrl, const char *desc, char **cache_nonce_addr,
                  const void *key, size_t keylen)
{
  gpg_error_t err;
  struct import_key_parm_s parm;
  struct cache_nonce_parm_s cn_parm;
  char line[ASSUAN_LINELENGTH];

  err = start_agent (ctrl, 0);
  if (err)
    return err;

  if (desc)
    {
      snprintf (line, DIM(line)-1, "SETKEYDESC %s", desc);
      line[DIM(line)-1] = 0;
      err = assuan_transact (agent_ctx, line,
                            NULL, NULL, NULL, NULL, NULL, NULL);
      if (err)
        return err;
    }

  parm.ctrl   = ctrl;
  parm.ctx    = agent_ctx;
  parm.key    = key;
  parm.keylen = keylen;

  snprintf (line, sizeof line, "IMPORT_KEY%s%s",
            cache_nonce_addr && *cache_nonce_addr? " ":"",
            cache_nonce_addr && *cache_nonce_addr? *cache_nonce_addr:"");
  cn_parm.cache_nonce_addr = cache_nonce_addr;
  cn_parm.passwd_nonce_addr = NULL;
  err = assuan_transact (agent_ctx, line,
                         NULL, NULL, inq_import_key_parms, &parm,
                         cache_nonce_status_cb, &cn_parm);
  return err;
}



/* Receive a secret key from the agent.  HEXKEYGRIP is the hexified
   keygrip, DESC a prompt to be displayed with the agent's passphrase
   question (needs to be plus+percent escaped).  On success the key is
   stored as a canonical S-expression at R_RESULT and R_RESULTLEN.  */
gpg_error_t
agent_export_key (ctrl_t ctrl, const char *hexkeygrip, const char *desc,
                  char **cache_nonce_addr,
                  unsigned char **r_result, size_t *r_resultlen)
{
  gpg_error_t err;
  struct cache_nonce_parm_s cn_parm;
  membuf_t data;
  size_t len;
  unsigned char *buf;
  char line[ASSUAN_LINELENGTH];

  *r_result = NULL;

  err = start_agent (ctrl, 0);
  if (err)
    return err;

  if (desc)
    {
      snprintf (line, DIM(line)-1, "SETKEYDESC %s", desc);
      err = assuan_transact (agent_ctx, line,
                             NULL, NULL, NULL, NULL, NULL, NULL);
      if (err)
        return err;
    }

  snprintf (line, DIM(line)-1, "EXPORT_KEY --openpgp %s%s %s",
            cache_nonce_addr && *cache_nonce_addr? "--cache-nonce=":"",
            cache_nonce_addr && *cache_nonce_addr? *cache_nonce_addr:"",
            hexkeygrip);

  init_membuf_secure (&data, 1024);
  cn_parm.cache_nonce_addr = cache_nonce_addr;
  cn_parm.passwd_nonce_addr = NULL;
  err = assuan_transact (agent_ctx, line,
                         membuf_data_cb, &data,
                         default_inq_cb, ctrl,
                         cache_nonce_status_cb, &cn_parm);
  if (err)
    {
      xfree (get_membuf (&data, &len));
      return err;
    }
  buf = get_membuf (&data, &len);
  if (!buf)
    return gpg_error_from_syserror ();
  *r_result = buf;
  *r_resultlen = len;
  return 0;
}



/* Ask the agent to change the passphrase of the key identified by
   HEXKEYGRIP.  If DESC is not NULL, display DESC instead of the
   default description message.  If CACHE_NONCE_ADDR is not NULL the
   agent is advised to first try a passphrase associated with that
   nonce.  If PASSWD_NONCE_ADDR is not NULL the agent will try to use
   the passphrase associated with that nonce.  */
gpg_error_t
agent_passwd (ctrl_t ctrl, const char *hexkeygrip, const char *desc,
              char **cache_nonce_addr, char **passwd_nonce_addr)
{
  gpg_error_t err;
  struct cache_nonce_parm_s cn_parm;
  char line[ASSUAN_LINELENGTH];

  err = start_agent (ctrl, 0);
  if (err)
    return err;

  if (!hexkeygrip || strlen (hexkeygrip) != 40)
    return gpg_error (GPG_ERR_INV_VALUE);

  if (desc)
    {
      snprintf (line, DIM(line)-1, "SETKEYDESC %s", desc);
      err = assuan_transact (agent_ctx, line,
                             NULL, NULL, NULL, NULL, NULL, NULL);
      if (err)
        return err;
    }

  snprintf (line, DIM(line)-1, "PASSWD %s%s %s%s %s",
            cache_nonce_addr && *cache_nonce_addr? "--cache-nonce=":"",
            cache_nonce_addr && *cache_nonce_addr? *cache_nonce_addr:"",
            passwd_nonce_addr && *passwd_nonce_addr? "--passwd-nonce=":"",
            passwd_nonce_addr && *passwd_nonce_addr? *passwd_nonce_addr:"",
            hexkeygrip);
  cn_parm.cache_nonce_addr = cache_nonce_addr;
  cn_parm.passwd_nonce_addr = passwd_nonce_addr;
  err = assuan_transact (agent_ctx, line, NULL, NULL,
                         default_inq_cb, ctrl,
                         cache_nonce_status_cb, &cn_parm);
  return err;
}