gnupg/g10/export.c

/* export.c - Export keys in the OpenPGP defined format.
 * Copyright (C) 1998, 1999, 2000, 2001, 2002, 2003, 2004,
 *               2005, 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 <assert.h>

#include "gpg.h"
#include "options.h"
#include "packet.h"
#include "status.h"
#include "keydb.h"
#include "util.h"
#include "main.h"
#include "i18n.h"
#include "trustdb.h"
#include "call-agent.h"

/* An object to keep track of subkeys. */
struct subkey_list_s
{
  struct subkey_list_s *next;
  u32 kid[2];
};
typedef struct subkey_list_s *subkey_list_t;


static int do_export (ctrl_t ctrl,
                      strlist_t users, int secret, unsigned int options );
static int do_export_stream (ctrl_t ctrl, iobuf_t out,
                             strlist_t users, int secret,
                             kbnode_t *keyblock_out, unsigned int options,
			     int *any);
static int build_sexp (iobuf_t out, PACKET *pkt, int *indent);


int
parse_export_options(char *str,unsigned int *options,int noisy)
{
  struct parse_options export_opts[]=
    {
      {"export-local-sigs",EXPORT_LOCAL_SIGS,NULL,
       N_("export signatures that are marked as local-only")},
      {"export-attributes",EXPORT_ATTRIBUTES,NULL,
       N_("export attribute user IDs (generally photo IDs)")},
      {"export-sensitive-revkeys",EXPORT_SENSITIVE_REVKEYS,NULL,
       N_("export revocation keys marked as \"sensitive\"")},
      {"export-clean",EXPORT_CLEAN,NULL,
       N_("remove unusable parts from key during export")},
      {"export-minimal",EXPORT_MINIMAL|EXPORT_CLEAN,NULL,
       N_("remove as much as possible from key during export")},
      {"export-sexp-format",EXPORT_SEXP_FORMAT, NULL,
       N_("export keys in an S-expression based format")},
      /* Aliases for backward compatibility */
      {"include-local-sigs",EXPORT_LOCAL_SIGS,NULL,NULL},
      {"include-attributes",EXPORT_ATTRIBUTES,NULL,NULL},
      {"include-sensitive-revkeys",EXPORT_SENSITIVE_REVKEYS,NULL,NULL},
      /* dummy */
      {"export-unusable-sigs",0,NULL,NULL},
      {"export-clean-sigs",0,NULL,NULL},
      {"export-clean-uids",0,NULL,NULL},
      {NULL,0,NULL,NULL}
      /* add tags for include revoked and disabled? */
    };

  return parse_options(str,options,export_opts,noisy);
}


/****************
 * Export the public keys (to standard out or --output).
 * Depending on opt.armor the output is armored.
 * options are defined in main.h.
 * If USERS is NULL, the complete ring will be exported.  */
int
export_pubkeys (ctrl_t ctrl, strlist_t users, unsigned int options )
{
  return do_export (ctrl, users, 0, options );
}

/****************
 * Export to an already opened stream; return -1 if no keys have
 * been exported
 */
int
export_pubkeys_stream (ctrl_t ctrl, iobuf_t out, strlist_t users,
		       kbnode_t *keyblock_out, unsigned int options )
{
  int any, rc;

  rc = do_export_stream (ctrl, out, users, 0, keyblock_out, options, &any);
  if (!rc && !any)
    rc = -1;
  return rc;
}


/*
 * Export a single key into a memory buffer.
 */
gpg_error_t
export_pubkey_buffer (ctrl_t ctrl, const char *keyspec, unsigned int options,
                      kbnode_t *r_keyblock, void **r_data, size_t *r_datalen)
{
  gpg_error_t err;
  iobuf_t iobuf;
  int any;
  strlist_t helplist;

  *r_keyblock = NULL;
  *r_data = NULL;
  *r_datalen = 0;

  helplist = NULL;
  if (!add_to_strlist_try (&helplist, keyspec))
    return gpg_error_from_syserror ();

  iobuf = iobuf_temp ();
  err = do_export_stream (ctrl, iobuf, helplist, 0, r_keyblock, options, &any);
  if (!err && !any)
    err = gpg_error (GPG_ERR_NOT_FOUND);
  if (!err)
    {
      const void *src;
      size_t datalen;

      iobuf_flush_temp (iobuf);
      src = iobuf_get_temp_buffer (iobuf);
      datalen = iobuf_get_temp_length (iobuf);
      if (!datalen)
        err = gpg_error (GPG_ERR_NO_PUBKEY);
      else if (!(*r_data = xtrymalloc (datalen)))
        err = gpg_error_from_syserror ();
      else
        {
          memcpy (*r_data, src, datalen);
          *r_datalen = datalen;
        }
    }
  iobuf_close (iobuf);
  free_strlist (helplist);
  if (err && *r_keyblock)
    {
      release_kbnode (*r_keyblock);
      *r_keyblock = NULL;
    }
  return err;
}


int
export_seckeys (ctrl_t ctrl, strlist_t users )
{
  /* Use only relevant options for the secret key. */
  unsigned int options = (opt.export_options & EXPORT_SEXP_FORMAT);
  return do_export (ctrl, users, 1, options);
}

int
export_secsubkeys (ctrl_t ctrl, strlist_t users )
{
  /* Use only relevant options for the secret key. */
  unsigned int options = (opt.export_options & EXPORT_SEXP_FORMAT);
  return do_export (ctrl, users, 2, options);
}


/* Export the keys identified by the list of strings in USERS.  If
   Secret is false public keys will be exported.  With secret true
   secret keys will be exported; in this case 1 means the entire
   secret keyblock and 2 only the subkeys.  OPTIONS are the export
   options to apply.  */
static int
do_export (ctrl_t ctrl, strlist_t users, int secret, unsigned int options )
{
  IOBUF out = NULL;
  int any, rc;
  armor_filter_context_t *afx = NULL;
  compress_filter_context_t zfx;

  memset( &zfx, 0, sizeof zfx);

  rc = open_outfile (GNUPG_INVALID_FD, NULL, 0, &out );
  if (rc)
    return rc;

  if (!(options & EXPORT_SEXP_FORMAT))
    {
      if ( opt.armor )
        {
          afx = new_armor_context ();
          afx->what = secret? 5 : 1;
          push_armor_filter (afx, out);
        }
      if ( opt.compress_keys )
        push_compress_filter (out,&zfx,default_compress_algo());
    }

  rc = do_export_stream (ctrl, out, users, secret, NULL, options, &any );

  if ( rc || !any )
    iobuf_cancel (out);
  else
    iobuf_close (out);
  release_armor_context (afx);
  return rc;
}



/* Release an entire subkey list. */
static void
release_subkey_list (subkey_list_t list)
{
  while (list)
    {
      subkey_list_t tmp = list->next;;
      xfree (list);
      list = tmp;
    }
}


/* Returns true if NODE is a subkey and contained in LIST. */
static int
subkey_in_list_p (subkey_list_t list, KBNODE node)
{
  if (node->pkt->pkttype == PKT_PUBLIC_SUBKEY
      || node->pkt->pkttype == PKT_SECRET_SUBKEY )
    {
      u32 kid[2];

      keyid_from_pk (node->pkt->pkt.public_key, kid);

      for (; list; list = list->next)
        if (list->kid[0] == kid[0] && list->kid[1] == kid[1])
          return 1;
    }
  return 0;
}

/* Allocate a new subkey list item from NODE. */
static subkey_list_t
new_subkey_list_item (KBNODE node)
{
  subkey_list_t list = xcalloc (1, sizeof *list);

  if (node->pkt->pkttype == PKT_PUBLIC_SUBKEY
      || node->pkt->pkttype == PKT_SECRET_SUBKEY)
    keyid_from_pk (node->pkt->pkt.public_key, list->kid);

  return list;
}


/* Helper function to check whether the subkey at NODE actually
   matches the description at DESC.  The function returns true if the
   key under question has been specified by an exact specification
   (keyID or fingerprint) and does match the one at NODE.  It is
   assumed that the packet at NODE is either a public or secret
   subkey. */
static int
exact_subkey_match_p (KEYDB_SEARCH_DESC *desc, KBNODE node)
{
  u32 kid[2];
  byte fpr[MAX_FINGERPRINT_LEN];
  size_t fprlen;
  int result = 0;

  switch(desc->mode)
    {
    case KEYDB_SEARCH_MODE_SHORT_KID:
    case KEYDB_SEARCH_MODE_LONG_KID:
      keyid_from_pk (node->pkt->pkt.public_key, kid);
      break;

    case KEYDB_SEARCH_MODE_FPR16:
    case KEYDB_SEARCH_MODE_FPR20:
    case KEYDB_SEARCH_MODE_FPR:
      fingerprint_from_pk (node->pkt->pkt.public_key, fpr,&fprlen);
      break;

    default:
      break;
    }

  switch(desc->mode)
    {
    case KEYDB_SEARCH_MODE_SHORT_KID:
      if (desc->u.kid[1] == kid[1])
        result = 1;
      break;

    case KEYDB_SEARCH_MODE_LONG_KID:
      if (desc->u.kid[0] == kid[0] && desc->u.kid[1] == kid[1])
        result = 1;
      break;

    case KEYDB_SEARCH_MODE_FPR16:
      if (!memcmp (desc->u.fpr, fpr, 16))
        result = 1;
      break;

    case KEYDB_SEARCH_MODE_FPR20:
    case KEYDB_SEARCH_MODE_FPR:
      if (!memcmp (desc->u.fpr, fpr, 20))
        result = 1;
      break;

    default:
      break;
    }

  return result;
}


/* Return a canonicalized public key algoithms.  This is used to
   compare different flavors of algorithms (e.g. ELG and ELG_E are
   considered the same).  */
static int
canon_pubkey_algo (int algo)
{
  switch (algo)
    {
    case GCRY_PK_RSA:
    case GCRY_PK_RSA_E:
    case GCRY_PK_RSA_S: return GCRY_PK_RSA;
    case GCRY_PK_ELG:
    case GCRY_PK_ELG_E: return GCRY_PK_ELG;
    default: return algo;
    }
}


/* Use the key transfer format given in S_PGP to create the secinfo
   structure in PK and change the parameter array in PK to include the
   secret parameters.  */
static gpg_error_t
transfer_format_to_openpgp (gcry_sexp_t s_pgp, PKT_public_key *pk)
{
  gpg_error_t err;
  gcry_sexp_t top_list;
  gcry_sexp_t list = NULL;
  const char *value;
  size_t valuelen;
  char *string;
  int  idx;
  int  is_v4, is_protected;
  int  pubkey_algo;
  int  protect_algo = 0;
  char iv[16];
  int  ivlen = 0;
  int  s2k_mode = 0;
  int  s2k_algo = 0;
  byte s2k_salt[8];
  u32  s2k_count = 0;
  size_t npkey, nskey;
  gcry_mpi_t skey[10];  /* We support up to 9 parameters.  */
  int skeyidx = 0;
  struct seckey_info *ski;

  top_list = gcry_sexp_find_token (s_pgp, "openpgp-private-key", 0);
  if (!top_list)
    goto bad_seckey;

  list = gcry_sexp_find_token (top_list, "version", 0);
  if (!list)
    goto bad_seckey;
  value = gcry_sexp_nth_data (list, 1, &valuelen);
  if (!value || valuelen != 1 || !(value[0] == '3' || value[0] == '4'))
    goto bad_seckey;
  is_v4 = (value[0] == '4');

  gcry_sexp_release (list);
  list = gcry_sexp_find_token (top_list, "protection", 0);
  if (!list)
    goto bad_seckey;
  value = gcry_sexp_nth_data (list, 1, &valuelen);
  if (!value)
    goto bad_seckey;
  if (valuelen == 4 && !memcmp (value, "sha1", 4))
    is_protected = 2;
  else if (valuelen == 3 && !memcmp (value, "sum", 3))
    is_protected = 1;
  else if (valuelen == 4 && !memcmp (value, "none", 4))
    is_protected = 0;
  else
    goto bad_seckey;
  if (is_protected)
    {
      string = gcry_sexp_nth_string (list, 2);
      if (!string)
        goto bad_seckey;
      protect_algo = gcry_cipher_map_name (string);
      xfree (string);

      value = gcry_sexp_nth_data (list, 3, &valuelen);
      if (!value || !valuelen || valuelen > sizeof iv)
        goto bad_seckey;
      memcpy (iv, value, valuelen);
      ivlen = valuelen;

      string = gcry_sexp_nth_string (list, 4);
      if (!string)
        goto bad_seckey;
      s2k_mode = strtol (string, NULL, 10);
      xfree (string);

      string = gcry_sexp_nth_string (list, 5);
      if (!string)
        goto bad_seckey;
      s2k_algo = gcry_md_map_name (string);
      xfree (string);

      value = gcry_sexp_nth_data (list, 6, &valuelen);
      if (!value || !valuelen || valuelen > sizeof s2k_salt)
        goto bad_seckey;
      memcpy (s2k_salt, value, valuelen);

      string = gcry_sexp_nth_string (list, 7);
      if (!string)
        goto bad_seckey;
      s2k_count = strtoul (string, NULL, 10);
      xfree (string);
    }

  gcry_sexp_release (list);
  list = gcry_sexp_find_token (top_list, "algo", 0);
  if (!list)
    goto bad_seckey;
  string = gcry_sexp_nth_string (list, 1);
  if (!string)
    goto bad_seckey;
  pubkey_algo = gcry_pk_map_name (string);
  xfree (string);

  if (gcry_pk_algo_info (pubkey_algo, GCRYCTL_GET_ALGO_NPKEY, NULL, &npkey)
      || gcry_pk_algo_info (pubkey_algo, GCRYCTL_GET_ALGO_NSKEY, NULL, &nskey)
      || !npkey || npkey >= nskey || nskey > PUBKEY_MAX_NSKEY)
    goto bad_seckey;
  pubkey_algo = map_pk_gcry_to_openpgp (pubkey_algo);

  gcry_sexp_release (list);
  list = gcry_sexp_find_token (top_list, "skey", 0);
  if (!list)
    goto bad_seckey;
  for (idx=0;;)
    {
      int is_enc;

      value = gcry_sexp_nth_data (list, ++idx, &valuelen);
      if (!value && skeyidx >= npkey)
        break;  /* Ready.  */

      /* Check for too many parameters.  Note that depending on the
         protection mode and version number we may see less than NSKEY
         (but at least NPKEY+1) parameters.  */
      if (idx >= 2*nskey)
        goto bad_seckey;
      if (skeyidx >= DIM (skey)-1)
        goto bad_seckey;

      if (!value || valuelen != 1 || !(value[0] == '_' || value[0] == 'e'))
        goto bad_seckey;
      is_enc = (value[0] == 'e');
      value = gcry_sexp_nth_data (list, ++idx, &valuelen);
      if (!value || !valuelen)
        goto bad_seckey;
      if (is_enc)
        {
          void *p = xtrymalloc (valuelen);
          if (!p)
            goto outofmem;
          memcpy (p, value, valuelen);
          skey[skeyidx] = gcry_mpi_set_opaque (NULL, p, valuelen*8);
          if (!skey[skeyidx])
            goto outofmem;
        }
      else
        {
          if (gcry_mpi_scan (skey + skeyidx, GCRYMPI_FMT_STD,
                             value, valuelen, NULL))
            goto bad_seckey;
        }
      skeyidx++;
    }
  skey[skeyidx++] = NULL;

  gcry_sexp_release (list); list = NULL;

  /* We have no need for the CSUM valuel thus we don't parse it.  */
  /* list = gcry_sexp_find_token (top_list, "csum", 0); */
  /* if (list) */
  /*   { */
  /*     string = gcry_sexp_nth_string (list, 1); */
  /*     if (!string) */
  /*       goto bad_seckey; */
  /*     desired_csum = strtoul (string, NULL, 10); */
  /*     xfree (string); */
  /*   } */
  /* else */
  /*   desired_csum = 0; */
  /* gcry_sexp_release (list); list = NULL; */

  gcry_sexp_release (top_list); top_list = NULL;

  /* log_debug ("XXX is_v4=%d\n", is_v4); */
  /* log_debug ("XXX pubkey_algo=%d\n", pubkey_algo); */
  /* log_debug ("XXX is_protected=%d\n", is_protected); */
  /* log_debug ("XXX protect_algo=%d\n", protect_algo); */
  /* log_printhex ("XXX iv", iv, ivlen); */
  /* log_debug ("XXX ivlen=%d\n", ivlen); */
  /* log_debug ("XXX s2k_mode=%d\n", s2k_mode); */
  /* log_debug ("XXX s2k_algo=%d\n", s2k_algo); */
  /* log_printhex ("XXX s2k_salt", s2k_salt, sizeof s2k_salt); */
  /* log_debug ("XXX s2k_count=%lu\n", (unsigned long)s2k_count); */
  /* for (idx=0; skey[idx]; idx++) */
  /*   { */
  /*     int is_enc = gcry_mpi_get_flag (skey[idx], GCRYMPI_FLAG_OPAQUE); */
  /*     log_info ("XXX skey[%d]%s:", idx, is_enc? " (enc)":""); */
  /*     if (is_enc) */
  /*       { */
  /*         void *p; */
  /*         unsigned int nbits; */
  /*         p = gcry_mpi_get_opaque (skey[idx], &nbits); */
  /*         log_printhex (NULL, p, (nbits+7)/8); */
  /*       } */
  /*     else */
  /*       gcry_mpi_dump (skey[idx]); */
  /*     log_printf ("\n"); */
  /*   } */

  if (!is_v4 || is_protected != 2 )
    {
      /* We only support the v4 format and a SHA-1 checksum.  */
      err = gpg_error (GPG_ERR_NOT_IMPLEMENTED);
      goto leave;
    }

  /* We need to change the received parameters for ECC algorithms.
     The transfer format has all parameters but OpenPGP defines that
     only the OID of the curve is to be used.  */
  if (pubkey_algo == PUBKEY_ALGO_ECDSA || pubkey_algo == PUBKEY_ALGO_ECDH)
    {
      gcry_sexp_t s_pubkey;
      const char *curvename, *curveoidstr;
      gcry_mpi_t mpi;

      /* We build an S-expression with the public key parameters and
         ask Libgcrypt to return the matching curve name.  */
      if (npkey != 6 || !skey[0] || !skey[1] || !skey[2]
          || !skey[3] || !skey[4] || !skey[5]
          || !skey[6] || skey[7])
        {
          err = gpg_error (GPG_ERR_INTERNAL);
          goto leave;
        }
      err = gcry_sexp_build (&s_pubkey, NULL,
                             "(public-key(ecc(p%m)(a%m)(b%m)(g%m)(n%m)))",
                             skey[0], skey[1], skey[2], skey[3], skey[4]);
      if (err)
        goto leave;
      curvename = gcry_pk_get_curve (s_pubkey, 0, NULL);
      gcry_sexp_release (s_pubkey);
      curveoidstr = gpg_curve_to_oid (curvename, NULL);
      if (!curveoidstr)
        {
          log_error ("no OID known for curve `%s'\n", curvename);
          err = gpg_error (GPG_ERR_UNKNOWN_NAME);
          goto leave;
        }
      err = openpgp_oid_from_str (curveoidstr, &mpi);
      if (err)
        goto leave;

      /* Now replace the curve parameters by the OID and shift the
         rest of the parameters.  */
      gcry_mpi_release (skey[0]);
      skey[0] = mpi;
      for (idx=1; idx <= 4; idx++)
        gcry_mpi_release (skey[idx]);
      skey[1] = skey[5];
      skey[2] = skey[6];
      for (idx=3; idx <= 6; idx++)
        skey[idx] = NULL;

      /* Fixup the NPKEY and NSKEY to match OpenPGP reality.  */
      npkey = 2;
      nskey = 3;

      /* for (idx=0; skey[idx]; idx++) */
      /*   { */
      /*     log_info ("YYY skey[%d]:", idx); */
      /*     if (gcry_mpi_get_flag (skey[idx], GCRYMPI_FLAG_OPAQUE)) */
      /*       { */
      /*         void *p; */
      /*         unsigned int nbits; */
      /*         p = gcry_mpi_get_opaque (skey[idx], &nbits); */
      /*         log_printhex (NULL, p, (nbits+7)/8); */
      /*       } */
      /*     else */
      /*       gcry_mpi_dump (skey[idx]); */
      /*     log_printf ("\n"); */
      /*   } */
    }

  /* Do some sanity checks.  */
  if (s2k_count > 255)
    {
      /* We expect an already encoded S2K count.  */
      err = gpg_error (GPG_ERR_INV_DATA);
      goto leave;
    }
  if (canon_pubkey_algo (pubkey_algo) != canon_pubkey_algo (pk->pubkey_algo))
    {
      err = gpg_error (GPG_ERR_PUBKEY_ALGO);
      goto leave;
    }
  err = openpgp_cipher_test_algo (protect_algo);
  if (err)
    goto leave;
  err = openpgp_md_test_algo (s2k_algo);
  if (err)
    goto leave;

  /* Check that the public key parameters match.  Note that since
     Libgcrypt 1.5 gcry_mpi_cmp handles opaque MPI correctly.  */
  for (idx=0; idx < npkey; idx++)
    if (gcry_mpi_cmp (pk->pkey[idx], skey[idx]))
      {
        err = gpg_error (GPG_ERR_BAD_PUBKEY);
        goto leave;
      }

  /* Check that the first secret key parameter in SKEY is encrypted
     and that there are no more secret key parameters.  The latter is
     guaranteed by the v4 packet format.  */
  if (!gcry_mpi_get_flag (skey[npkey], GCRYMPI_FLAG_OPAQUE))
    goto bad_seckey;
  if (npkey+1 < DIM (skey) && skey[npkey+1])
    goto bad_seckey;

  /* Check that the secret key parameters in PK are all set to NULL. */
  for (idx=npkey; idx < nskey; idx++)
    if (pk->pkey[idx])
      goto bad_seckey;

  /* Now build the protection info. */
  pk->seckey_info = ski = xtrycalloc (1, sizeof *ski);
  if (!ski)
    {
      err = gpg_error_from_syserror ();
      goto leave;
    }

  ski->is_protected = 1;
  ski->sha1chk = 1;
  ski->algo = protect_algo;
  ski->s2k.mode = s2k_mode;
  ski->s2k.hash_algo = s2k_algo;
  assert (sizeof ski->s2k.salt == sizeof s2k_salt);
  memcpy (ski->s2k.salt, s2k_salt, sizeof s2k_salt);
  ski->s2k.count = s2k_count;
  assert (ivlen <= sizeof ski->iv);
  memcpy (ski->iv, iv, ivlen);
  ski->ivlen = ivlen;

  /* Store the protected secret key parameter.  */
  pk->pkey[npkey] = skey[npkey];
  skey[npkey] = NULL;

  /* That's it.  */

 leave:
  gcry_sexp_release (list);
  gcry_sexp_release (top_list);
  for (idx=0; idx < skeyidx; idx++)
    gcry_mpi_release (skey[idx]);
  return err;

 bad_seckey:
  err = gpg_error (GPG_ERR_BAD_SECKEY);
  goto leave;

 outofmem:
  err = gpg_error (GPG_ERR_ENOMEM);
  goto leave;
}

/* Export the keys identified by the list of strings in USERS to the
   stream OUT.  If Secret is false public keys will be exported.  With
   secret true secret keys will be exported; in this case 1 means the
   entire secret keyblock and 2 only the subkeys.  OPTIONS are the
   export options to apply.  If KEYBLOCK_OUT is not NULL, AND the exit
   code is zero, a pointer to the first keyblock found and exported
   will be stored at this address; no other keyblocks are exported in
   this case.  The caller must free it the returned keyblock.  If any
   key has been exported true is stored at ANY. */
static int
do_export_stream (ctrl_t ctrl, iobuf_t out, strlist_t users, int secret,
		  kbnode_t *keyblock_out, unsigned int options, int *any)
{
  gpg_error_t err = 0;
  PACKET pkt;
  KBNODE keyblock = NULL;
  KBNODE kbctx, node;
  size_t ndesc, descindex;
  KEYDB_SEARCH_DESC *desc = NULL;
  subkey_list_t subkey_list = NULL;  /* Track already processed subkeys. */
  KEYDB_HANDLE kdbhd;
  strlist_t sl;
  int indent = 0;
  gcry_cipher_hd_t cipherhd = NULL;

  *any = 0;
  init_packet (&pkt);
  kdbhd = keydb_new ();

  if (!users)
    {
      ndesc = 1;
      desc = xcalloc (ndesc, sizeof *desc);
      desc[0].mode = KEYDB_SEARCH_MODE_FIRST;
    }
  else
    {
      for (ndesc=0, sl=users; sl; sl = sl->next, ndesc++)
        ;
      desc = xmalloc ( ndesc * sizeof *desc);

      for (ndesc=0, sl=users; sl; sl = sl->next)
        {
          if (!(err=classify_user_id (sl->d, desc+ndesc, 1)))
            ndesc++;
          else
            log_error (_("key \"%s\" not found: %s\n"),
                       sl->d, gpg_strerror (err));
        }

      /* It would be nice to see which of the given users did actually
         match one in the keyring.  To implement this we need to have
         a found flag for each entry in desc.  To set this flag we
         must check all those entries after a match to mark all
         matched one - currently we stop at the first match.  To do
         this we need an extra flag to enable this feature.  */
    }

#ifdef ENABLE_SELINUX_HACKS
  if (secret)
    {
      log_error (_("exporting secret keys not allowed\n"));
      err = gpg_error (GPG_ERR_NOT_SUPPORTED);
      goto leave;
    }
#endif

  /* For secret key export we need to setup a decryption context.  */
  if (secret)
    {
      void *kek = NULL;
      size_t keklen;

      err = agent_keywrap_key (ctrl, 1, &kek, &keklen);
      if (err)
        {
          log_error ("error getting the KEK: %s\n", gpg_strerror (err));
          goto leave;
        }

      /* Prepare a cipher context.  */
      err = gcry_cipher_open (&cipherhd, GCRY_CIPHER_AES128,
                              GCRY_CIPHER_MODE_AESWRAP, 0);
      if (!err)
        err = gcry_cipher_setkey (cipherhd, kek, keklen);
      if (err)
        {
          log_error ("error setting up an encryption context: %s\n",
                     gpg_strerror (err));
          goto leave;
        }
      xfree (kek);
      kek = NULL;
    }

  while (!(err = keydb_search2 (kdbhd, desc, ndesc, &descindex)))
    {
      int skip_until_subkey = 0;
      u32 keyid[2];
      PKT_public_key *pk;

      if (!users)
        desc[0].mode = KEYDB_SEARCH_MODE_NEXT;

      /* Read the keyblock. */
      release_kbnode (keyblock);
      keyblock = NULL;
      err = keydb_get_keyblock (kdbhd, &keyblock);
      if (err)
        {
          log_error (_("error reading keyblock: %s\n"), gpg_strerror (err));
          goto leave;
	}

      node = find_kbnode (keyblock, PKT_PUBLIC_KEY);
      if (!node)
        {
          log_error ("public key packet not found in keyblock - skipped\n");
          continue;
        }
      pk = node->pkt->pkt.public_key;
      keyid_from_pk (pk, keyid);

      /* If a secret key export is required we need to check whether
         we have a secret key at all and if so create the seckey_info
         structure.  */
      if (secret)
        {
          if (agent_probe_any_secret_key (ctrl, keyblock))
            continue;  /* No secret key (neither primary nor subkey).  */

          /* No v3 keys with GNU mode 1001. */
          if (secret == 2 && pk->version == 3)
            {
              log_info (_("key %s: PGP 2.x style key - skipped\n"),
                        keystr (keyid));
              continue;
            }

          /* The agent does not yet allow to export v3 packets.  It is
             actually questionable whether we should allow them at
             all.  */
          if (pk->version == 3)
            {
              log_info ("key %s: PGP 2.x style key (v3) export "
                        "not yet supported - skipped\n", keystr (keyid));
              continue;
            }
        }

      /* Always do the cleaning on the public key part if requested.
         Note that we don't yet set this option if we are exporting
         secret keys.  Note that both export-clean and export-minimal
         only apply to UID sigs (0x10, 0x11, 0x12, and 0x13).  A
         designated revocation is never stripped, even with
         export-minimal set.  */
      if ((options & EXPORT_CLEAN))
        clean_key (keyblock, opt.verbose, (options&EXPORT_MINIMAL), NULL, NULL);

      /* And write it. */
      for (kbctx=NULL; (node = walk_kbnode (keyblock, &kbctx, 0)); )
        {
          if (skip_until_subkey)
            {
              if (node->pkt->pkttype == PKT_PUBLIC_SUBKEY)
                skip_until_subkey = 0;
              else
                continue;
            }

          /* We used to use comment packets, but not any longer.  In
             case we still have comments on a key, strip them here
             before we call build_packet(). */
          if (node->pkt->pkttype == PKT_COMMENT)
            continue;

          /* Make sure that ring_trust packets never get exported. */
          if (node->pkt->pkttype == PKT_RING_TRUST)
            continue;

          /* If exact is set, then we only export what was requested
             (plus the primary key, if the user didn't specifically
             request it). */
          if (desc[descindex].exact
              && node->pkt->pkttype == PKT_PUBLIC_SUBKEY)
            {
              if (!exact_subkey_match_p (desc+descindex, node))
                {
                  /* Before skipping this subkey, check whether any
                     other description wants an exact match on a
                     subkey and include that subkey into the output
                     too.  Need to add this subkey to a list so that
                     it won't get processed a second time.

                     So the first step here is to check that list and
                     skip in any case if the key is in that list.

                     We need this whole mess because the import
                     function of GnuPG < 2.1 is not able to merge
                     secret keys and thus it is useless to output them
                     as two separate keys and have import merge them.  */
                  if (subkey_in_list_p (subkey_list, node))
                    skip_until_subkey = 1; /* Already processed this one. */
                  else
                    {
                      size_t j;

                      for (j=0; j < ndesc; j++)
                        if (j != descindex && desc[j].exact
                            && exact_subkey_match_p (desc+j, node))
                          break;
                      if (!(j < ndesc))
                        skip_until_subkey = 1; /* No other one matching. */
                    }
                }

              if(skip_until_subkey)
                continue;

              /* Mark this one as processed. */
              {
                subkey_list_t tmp = new_subkey_list_item (node);
                tmp->next = subkey_list;
                subkey_list = tmp;
              }
            }

          if (node->pkt->pkttype == PKT_SIGNATURE)
            {
              /* Do not export packets which are marked as not
                 exportable.  */
              if (!(options&EXPORT_LOCAL_SIGS)
                  && !node->pkt->pkt.signature->flags.exportable)
                continue; /* not exportable */

              /* Do not export packets with a "sensitive" revocation
                 key unless the user wants us to.  Note that we do
                 export these when issuing the actual revocation
                 (see revoke.c). */
              if (!(options&EXPORT_SENSITIVE_REVKEYS)
                  && node->pkt->pkt.signature->revkey)
                {
                  int i;

                  for (i=0;i<node->pkt->pkt.signature->numrevkeys;i++)
                    if ( (node->pkt->pkt.signature->revkey[i]->class & 0x40))
                      break;

                  if (i < node->pkt->pkt.signature->numrevkeys)
                    continue;
                }
            }

          /* Don't export attribs? */
          if (!(options&EXPORT_ATTRIBUTES)
              && node->pkt->pkttype == PKT_USER_ID
              && node->pkt->pkt.user_id->attrib_data )
            {
	      /* Skip until we get to something that is not an attrib
		 or a signature on an attrib */
	      while (kbctx->next && kbctx->next->pkt->pkttype==PKT_SIGNATURE)
                kbctx = kbctx->next;

	      continue;
	    }

          if (secret && (node->pkt->pkttype == PKT_PUBLIC_KEY
                         || node->pkt->pkttype == PKT_PUBLIC_SUBKEY))
            {
              u32 subkidbuf[2], *subkid;
              char *hexgrip, *serialno;

              pk = node->pkt->pkt.public_key;
              if (node->pkt->pkttype == PKT_PUBLIC_KEY)
                subkid = NULL;
              else
                {
                  keyid_from_pk (pk, subkidbuf);
                  subkid = subkidbuf;
                }

              if (pk->seckey_info)
                {
                  log_error ("key %s: oops: seckey_info already set"
                             " - skipped\n", keystr_with_sub (keyid, subkid));
                  skip_until_subkey = 1;
                  continue;
                }

              err = hexkeygrip_from_pk (pk, &hexgrip);
              if (err)
                {
                  log_error ("key %s: error computing keygrip: %s"
                             " - skipped\n", keystr_with_sub (keyid, subkid),
                             gpg_strerror (err));
                  skip_until_subkey = 1;
                  err = 0;
                  continue;
                }

              if (secret == 2 && node->pkt->pkttype == PKT_PUBLIC_KEY)
                {
                  /* We are asked not to export the secret parts of
                     the primary key.  Make up an error code to create
                     the stub.  */
                  err = GPG_ERR_NOT_FOUND;
                  serialno = NULL;
                }
              else
                err = agent_get_keyinfo (ctrl, hexgrip, &serialno);

              if ((!err && serialno)
                  && secret == 2 && node->pkt->pkttype == PKT_PUBLIC_KEY)
                {
                  /* It does not make sense to export a key with its
                     primary key on card using a non-key stub.  Thus
                     we skip those keys when used with
                     --export-secret-subkeys. */
                  log_info (_("key %s: key material on-card - skipped\n"),
                            keystr_with_sub (keyid, subkid));
                  skip_until_subkey = 1;
                }
              else if (gpg_err_code (err) == GPG_ERR_NOT_FOUND
                       || (!err && serialno))
                {
                  /* Create a key stub.  */
                  struct seckey_info *ski;
                  const char *s;

                  pk->seckey_info = ski = xtrycalloc (1, sizeof *ski);
                  if (!ski)
                    {
                      err = gpg_error_from_syserror ();
                      xfree (hexgrip);
                      goto leave;
                    }

                  ski->is_protected = 1;
                  if (err)
                    ski->s2k.mode = 1001; /* GNU dummy (no secret key).  */
                  else
                    {
                      ski->s2k.mode = 1002; /* GNU-divert-to-card.  */
                      for (s=serialno; sizeof (ski->ivlen) && *s && s[1];
                           ski->ivlen++, s += 2)
                        ski->iv[ski->ivlen] = xtoi_2 (s);
                    }

                  if ((options&EXPORT_SEXP_FORMAT))
                    err = build_sexp (out, node->pkt, &indent);
                  else
                    err = build_packet (out, node->pkt);
                }
              else if (!err)
                {
                  /* FIXME: Move this spaghetti code into a separate
                     function.  */
                  unsigned char *wrappedkey = NULL;
                  size_t wrappedkeylen;
                  unsigned char *key = NULL;
                  size_t keylen, realkeylen;
                  gcry_sexp_t s_skey;

                  if (opt.verbose)
                    log_info ("key %s: asking agent for the secret parts\n",
                              keystr_with_sub (keyid, subkid));

                  err = agent_export_key (ctrl, hexgrip, "Key foo", NULL,
                                          &wrappedkey, &wrappedkeylen);
                  if (err)
                    goto unwraperror;
                  if (wrappedkeylen < 24)
                    {
                      err = gpg_error (GPG_ERR_INV_LENGTH);
                      goto unwraperror;
                    }
                  keylen = wrappedkeylen - 8;
                  key = xtrymalloc_secure (keylen);
                  if (!key)
                    {
                      err = gpg_error_from_syserror ();
                      goto unwraperror;
                    }
                  err = gcry_cipher_decrypt (cipherhd, key, keylen,
                                             wrappedkey, wrappedkeylen);
                  if (err)
                    goto unwraperror;
                  realkeylen = gcry_sexp_canon_len (key, keylen, NULL, &err);
                  if (!realkeylen)
                    goto unwraperror; /* Invalid csexp.  */

                  err = gcry_sexp_sscan (&s_skey, NULL, key, realkeylen);
                  xfree (key);
                  key = NULL;
                  if (err)
                    goto unwraperror;
                  err = transfer_format_to_openpgp (s_skey, pk);
                  gcry_sexp_release (s_skey);
                  if (err)
                    goto unwraperror;

                  if ((options&EXPORT_SEXP_FORMAT))
                    err = build_sexp (out, node->pkt, &indent);
                  else
                    err = build_packet (out, node->pkt);
                  goto unwraperror_leave;

                unwraperror:
                  xfree (wrappedkey);
                  xfree (key);
                  if (err)
                    {
                      log_error ("key %s: error receiving key from agent:"
                                 " %s%s\n",
                                 keystr_with_sub (keyid, subkid),
                                 gpg_strerror (err),
                                 gpg_err_code (err) == GPG_ERR_FULLY_CANCELED?
                                 "":_(" - skipped"));
                      if (gpg_err_code (err) == GPG_ERR_FULLY_CANCELED)
                        goto leave;
                      skip_until_subkey = 1;
                      err = 0;
                    }
                unwraperror_leave:
                  ;
                }
              else
                {
                  log_error ("key %s: error getting keyinfo from agent: %s"
                             " - skipped\n", keystr_with_sub (keyid, subkid),
                             gpg_strerror (err));
                  skip_until_subkey = 1;
                  err = 0;
                }

              xfree (pk->seckey_info);
              pk->seckey_info = NULL;
              xfree (hexgrip);
            }
          else
            {
              if ((options&EXPORT_SEXP_FORMAT))
                err = build_sexp (out, node->pkt, &indent);
              else
                err = build_packet (out, node->pkt);
            }

          if (err)
            {
              log_error ("build_packet(%d) failed: %s\n",
                         node->pkt->pkttype, gpg_strerror (err));
              goto leave;
	    }

          if (!skip_until_subkey)
            *any = 1;
	}

      if ((options&EXPORT_SEXP_FORMAT) && indent)
        {
          for (; indent; indent--)
            iobuf_put (out, ')');
          iobuf_put (out, '\n');
        }

      if (keyblock_out)
        {
          *keyblock_out = keyblock;
          break;
        }
    }
  if ((options&EXPORT_SEXP_FORMAT) && indent)
    {
      for (; indent; indent--)
        iobuf_put (out, ')');
      iobuf_put (out, '\n');
    }
  if (gpg_err_code (err) == GPG_ERR_NOT_FOUND)
    err = 0;

 leave:
  gcry_cipher_close (cipherhd);
  release_subkey_list (subkey_list);
  xfree(desc);
  keydb_release (kdbhd);
  if (err || !keyblock_out)
    release_kbnode( keyblock );
  if( !*any )
    log_info(_("WARNING: nothing exported\n"));
  return err;
}



/* static int */
/* write_sexp_line (iobuf_t out, int *indent, const char *text) */
/* { */
/*   int i; */

/*   for (i=0; i < *indent; i++) */
/*     iobuf_put (out, ' '); */
/*   iobuf_writestr (out, text); */
/*   return 0; */
/* } */

/* static int */
/* write_sexp_keyparm (iobuf_t out, int *indent, const char *name, gcry_mpi_t a) */
/* { */
/*   int rc; */
/*   unsigned char *buffer; */

/*   write_sexp_line (out, indent, "("); */
/*   iobuf_writestr (out, name); */
/*   iobuf_writestr (out, " #"); */

/*   rc = gcry_mpi_aprint (GCRYMPI_FMT_HEX, &buffer, NULL, a); */
/*   assert (!rc); */
/*   iobuf_writestr (out, buffer); */
/*   iobuf_writestr (out, "#)"); */
/*   gcry_free (buffer); */
/*   return 0; */
/* } */

static int
build_sexp_seckey (iobuf_t out, PACKET *pkt, int *indent)
{
  (void)out;
  (void)pkt;
  (void)indent;

  /* FIXME: Not yet implemented.  */
  return gpg_error (GPG_ERR_NOT_IMPLEMENTED);
  /* PKT_secret_key *sk = pkt->pkt.secret_key; */
  /* char tmpbuf[100]; */

  /* if (pkt->pkttype == PKT_SECRET_KEY) */
  /*   { */
  /*     iobuf_writestr (out, "(openpgp-key\n"); */
  /*     (*indent)++; */
  /*   } */
  /* else */
  /*   { */
  /*     iobuf_writestr (out, " (subkey\n"); */
  /*     (*indent)++; */
  /*   } */
  /* (*indent)++; */
  /* write_sexp_line (out, indent, "(private-key\n"); */
  /* (*indent)++; */
  /* if (is_RSA (sk->pubkey_algo) && !sk->is_protected) */
  /*   { */
  /*     write_sexp_line (out, indent, "(rsa\n"); */
  /*     (*indent)++; */
  /*     write_sexp_keyparm (out, indent, "n", sk->skey[0]); iobuf_put (out,'\n'); */
  /*     write_sexp_keyparm (out, indent, "e", sk->skey[1]); iobuf_put (out,'\n'); */
  /*     write_sexp_keyparm (out, indent, "d", sk->skey[2]); iobuf_put (out,'\n'); */
  /*     write_sexp_keyparm (out, indent, "p", sk->skey[3]); iobuf_put (out,'\n'); */
  /*     write_sexp_keyparm (out, indent, "q", sk->skey[4]); iobuf_put (out,'\n'); */
  /*     write_sexp_keyparm (out, indent, "u", sk->skey[5]);  */
  /*     iobuf_put (out,')'); iobuf_put (out,'\n'); */
  /*     (*indent)--; */
  /*   } */
  /* else if (sk->pubkey_algo == PUBKEY_ALGO_DSA && !sk->is_protected) */
  /*   { */
  /*     write_sexp_line (out, indent, "(dsa\n"); */
  /*     (*indent)++; */
  /*     write_sexp_keyparm (out, indent, "p", sk->skey[0]); iobuf_put (out,'\n'); */
  /*     write_sexp_keyparm (out, indent, "q", sk->skey[1]); iobuf_put (out,'\n'); */
  /*     write_sexp_keyparm (out, indent, "g", sk->skey[2]); iobuf_put (out,'\n'); */
  /*     write_sexp_keyparm (out, indent, "y", sk->skey[3]); iobuf_put (out,'\n'); */
  /*     write_sexp_keyparm (out, indent, "x", sk->skey[4]); */
  /*     iobuf_put (out,')'); iobuf_put (out,'\n'); */
  /*     (*indent)--; */
  /*   } */
  /* else if (sk->pubkey_algo == PUBKEY_ALGO_ECDSA && !sk->is_protected) */
  /*   { */
  /*     write_sexp_line (out, indent, "(ecdsa\n"); */
  /*     (*indent)++;  */
  /*     write_sexp_keyparm (out, indent, "c", sk->skey[0]); iobuf_put (out,'\n'); */
  /*     write_sexp_keyparm (out, indent, "q", sk->skey[6]); iobuf_put (out,'\n'); */
  /*     write_sexp_keyparm (out, indent, "d", sk->skey[7]); */
  /*     iobuf_put (out,')'); iobuf_put (out,'\n'); */
  /*     (*indent)--; */
  /*   } */
  /* else if (is_ELGAMAL (sk->pubkey_algo) && !sk->is_protected) */
  /*   { */
  /*     write_sexp_line (out, indent, "(elg\n"); */
  /*     (*indent)++; */
  /*     write_sexp_keyparm (out, indent, "p", sk->skey[0]); iobuf_put (out,'\n'); */
  /*     write_sexp_keyparm (out, indent, "g", sk->skey[2]); iobuf_put (out,'\n'); */
  /*     write_sexp_keyparm (out, indent, "y", sk->skey[3]); iobuf_put (out,'\n'); */
  /*     write_sexp_keyparm (out, indent, "x", sk->skey[4]); */
  /*     iobuf_put (out,')'); iobuf_put (out,'\n'); */
  /*     (*indent)--; */
  /*   } */
  /* write_sexp_line (out, indent,  "(attrib\n"); (*indent)++; */
  /* sprintf (tmpbuf, "(created \"%lu\"", (unsigned long)sk->timestamp); */
  /* write_sexp_line (out, indent, tmpbuf); */
  /* iobuf_put (out,')'); (*indent)--; /\* close created *\/ */
  /* iobuf_put (out,')'); (*indent)--; /\* close attrib *\/ */
  /* iobuf_put (out,')'); (*indent)--; /\* close private-key *\/ */
  /* if (pkt->pkttype != PKT_SECRET_KEY) */
  /*   iobuf_put (out,')'), (*indent)--; /\* close subkey *\/ */
  /* iobuf_put (out,'\n'); */

  /* return 0; */
}


/* For some packet types we write them in a S-expression format.  This
   is still EXPERIMENTAL and subject to change.  */
static int
build_sexp (iobuf_t out, PACKET *pkt, int *indent)
{
  int rc;

  switch (pkt->pkttype)
    {
    case PKT_SECRET_KEY:
    case PKT_SECRET_SUBKEY:
      rc = build_sexp_seckey (out, pkt, indent);
      break;
    default:
      rc = 0;
      break;
    }
  return rc;
}