Import OpenPGP keys into the agent.

1 files changed, 807 insertions, 0 deletions

diff --git a/agent/cvt-openpgp.c b/agent/cvt-openpgp.c
new file mode 100644
index 000000000..a392518ba
--- /dev/null
+++ b/agent/cvt-openpgp.c
@@ -0,0 +1,807 @@
+/* cvt-openpgp.c - Convert an OpenPGP key to our internal format.
+ * Copyright (C) 1998, 1999, 2000, 2001, 2002, 2006, 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 <assert.h>
+
+#include "agent.h"
+#include "i18n.h"
+#include "cvt-openpgp.h"
+
+
+/* Helper to pass data via the callback to do_unprotect. */
+struct try_do_unprotect_arg_s 
+{
+  int  is_v4;
+  int  is_protected;
+  int  pubkey_algo;
+  int  protect_algo;
+  char *iv;
+  int  ivlen;
+  int  s2k_mode;
+  int  s2k_algo;
+  byte *s2k_salt;
+  u32  s2k_count;
+  u16 desired_csum;
+  gcry_mpi_t *skey;
+  size_t skeysize;
+  int skeyidx;
+  gcry_sexp_t *r_key;
+};
+
+
+
+/* Compute the keygrip from the public key and store it at GRIP.  */
+static gpg_error_t
+get_keygrip (int pubkey_algo, gcry_mpi_t *pkey, unsigned char *grip)
+{
+  gpg_error_t err;
+  gcry_sexp_t s_pkey = NULL;
+
+  switch (pubkey_algo)
+    {
+    case GCRY_PK_DSA:
+      err = gcry_sexp_build (&s_pkey, NULL,
+                             "(public-key(dsa(p%m)(q%m)(g%m)(y%m)))",
+                             pkey[0], pkey[1], pkey[2], pkey[3]);
+      break;
+
+    case GCRY_PK_ELG:
+    case GCRY_PK_ELG_E:
+      err = gcry_sexp_build (&s_pkey, NULL,
+                             "(public-key(elg(p%m)(g%m)(y%m)))",
+                             pkey[0], pkey[1], pkey[2]);
+      break;
+
+    case GCRY_PK_RSA:
+    case GCRY_PK_RSA_E:
+    case GCRY_PK_RSA_S:
+      err = gcry_sexp_build (&s_pkey, NULL,
+                             "(public-key(rsa(n%m)(e%m)))", pkey[0], pkey[1]);
+      break;
+
+    default:
+      err = gpg_error (GPG_ERR_PUBKEY_ALGO);
+      break;
+    }
+
+  if (!err && !gcry_pk_get_keygrip (s_pkey, grip))
+    err = gpg_error (GPG_ERR_INTERNAL);
+
+  gcry_sexp_release (s_pkey);
+  return err;
+}
+
+
+/* Convert a secret key given as algorithm id and an array of key
+   parameters into our s-expression based format.  */
+static gpg_error_t
+convert_secret_key (gcry_sexp_t *r_key, int pubkey_algo, gcry_mpi_t *skey)
+{
+  gpg_error_t err;
+  gcry_sexp_t s_skey = NULL;
+
+  *r_key = NULL;
+
+  switch (pubkey_algo)
+    {
+    case GCRY_PK_DSA:
+      err = gcry_sexp_build (&s_skey, NULL,
+                             "(private-key(dsa(p%m)(q%m)(g%m)(y%m)(x%m)))",
+                             skey[0], skey[1], skey[2], skey[3], skey[4]);
+      break;
+
+    case GCRY_PK_ELG:
+    case GCRY_PK_ELG_E:
+      err = gcry_sexp_build (&s_skey, NULL,
+                             "(private-key(elg(p%m)(g%m)(y%m)(x%m)))",
+                             skey[0], skey[1], skey[2], skey[3]);
+      break;
+
+
+    case GCRY_PK_RSA:
+    case GCRY_PK_RSA_E:
+    case GCRY_PK_RSA_S:
+      err = gcry_sexp_build (&s_skey, NULL,
+                             "(private-key(rsa(n%m)(e%m)(d%m)(p%m)(q%m)(u%m)))",
+                             skey[0], skey[1], skey[2], skey[3], skey[4],
+                             skey[5]);
+
+    default:
+      err = gpg_error (GPG_ERR_PUBKEY_ALGO);
+      break;
+    }
+
+  if (!err)
+    *r_key = s_skey;
+  return err;
+}
+
+
+
+/* Hash the passphrase and set the key. */
+static gpg_error_t
+hash_passphrase_and_set_key (const char *passphrase,
+                             gcry_cipher_hd_t hd, int protect_algo,
+                             int s2k_mode, int s2k_algo,
+                             byte *s2k_salt, u32 s2k_count)
+{
+  gpg_error_t err;
+  unsigned char *key;
+  size_t keylen;
+
+  keylen = gcry_cipher_get_algo_keylen (protect_algo);
+  if (!keylen)
+    return gpg_error (GPG_ERR_INTERNAL);
+  
+  key = xtrymalloc_secure (keylen);
+  if (!key)
+    return gpg_error_from_syserror ();
+
+  err = s2k_hash_passphrase (passphrase,
+                             s2k_algo, s2k_mode, s2k_salt, s2k_count,
+                             key, keylen);
+  if (!err)
+    err = gcry_cipher_setkey (hd, key, keylen);
+
+  xfree (key);
+  return err;
+}
+
+
+static u16
+checksum (const unsigned char *p, unsigned int n)
+{
+  u16 a;
+  
+  for (a=0; n; n-- )
+    a += *p++;
+  return a;
+}
+
+
+/* Note that this function modified SKEY.  SKEYSIZE is the allocated
+   size of the array including the NULL item; this is used for a
+   bounds check.  On success a converted key is stored at R_KEY.  */
+static int
+do_unprotect (const char *passphrase,
+              int pkt_version, int pubkey_algo, int is_protected,
+              gcry_mpi_t *skey, size_t skeysize,
+              int protect_algo, void *protect_iv, size_t protect_ivlen,
+              int s2k_mode, int s2k_algo, byte *s2k_salt, u32 s2k_count,
+              u16 desired_csum, gcry_sexp_t *r_key)
+{
+  gpg_error_t err;
+  size_t npkey, nskey, skeylen;
+  gcry_cipher_hd_t cipher_hd = NULL;
+  u16 actual_csum;
+  size_t nbytes;
+  int i;
+  gcry_mpi_t tmpmpi;
+
+  *r_key = NULL;
+
+  /* Count the actual number of MPIs is in the array and set the
+     remainder to NULL for easier processing later on.  */
+  for (skeylen = 0; skey[skeylen]; skeylen++)
+    ;
+  for (i=skeylen; i < skeysize; i++)
+    skey[i] = NULL;
+
+  /* Check some args.  */
+  if (s2k_mode == 1001)
+    {
+      /* Stub key.  */
+      log_info (_("secret key parts are not available\n"));
+      return gpg_error (GPG_ERR_UNUSABLE_SECKEY);
+    }
+
+  if (gcry_pk_test_algo (pubkey_algo))
+    {
+      /* The algorithm numbers are Libgcrypt numbers but fortunately
+         the OpenPGP algorithm numbers map one-to-one to the Libgcrypt
+         numbers.  */
+      log_info (_("public key algorithm %d (%s) is not supported\n"),
+                pubkey_algo, gcry_pk_algo_name (pubkey_algo));
+      return gpg_error (GPG_ERR_PUBKEY_ALGO);
+    }
+
+  /* Get properties of the public key algorithm and do some
+     consistency checks.  Note that we need at least NPKEY+1 elements
+     in the SKEY array. */
+  if ( (err = gcry_pk_algo_info (pubkey_algo, GCRYCTL_GET_ALGO_NPKEY,
+                                 NULL, &npkey))
+       || (err = gcry_pk_algo_info (pubkey_algo, GCRYCTL_GET_ALGO_NSKEY,
+                                    NULL, &nskey)))
+    return err;
+  if (!npkey || npkey >= nskey)
+    return gpg_error (GPG_ERR_INTERNAL);
+  if (skeylen <= npkey)
+    return gpg_error (GPG_ERR_MISSING_VALUE);
+  if (nskey+1 >= skeysize)
+    return gpg_error (GPG_ERR_BUFFER_TOO_SHORT);
+  
+  /* Check whether SKEY is at all protected.  If it is not protected
+     merely verify the checksum.  */
+  if (!is_protected)
+    {
+      unsigned char *buffer;
+
+      actual_csum = 0;
+      for (i=npkey; i < nskey; i++)
+        {
+          if (!skey[i] || gcry_mpi_get_flag (skey[i], GCRYMPI_FLAG_OPAQUE))
+            return gpg_error (GPG_ERR_BAD_SECKEY);
+          
+          err = gcry_mpi_print (GCRYMPI_FMT_PGP, NULL, 0, &nbytes, skey[i]);
+          if (!err)
+            {
+              buffer = (gcry_is_secure (skey[i])?
+                        xtrymalloc_secure (nbytes) : xtrymalloc (nbytes));
+              if (!buffer)
+                return gpg_error_from_syserror ();
+              err = gcry_mpi_print (GCRYMPI_FMT_PGP, buffer, nbytes,
+                                    NULL, skey[i]);
+              if (!err)
+                actual_csum += checksum (buffer, nbytes);
+              xfree (buffer);
+            }
+          if (err)
+            return err;
+        }
+      
+      if (actual_csum != desired_csum)
+        return gpg_error (GPG_ERR_CHECKSUM);
+      return 0;
+    }
+
+
+  if (gcry_cipher_test_algo (protect_algo))
+    {
+      /* The algorithm numbers are Libgcrypt numbers but fortunately
+         the OpenPGP algorithm numbers map one-to-one to the Libgcrypt
+         numbers.  */
+      log_info (_("protection algorithm %d (%s) is not supported\n"),
+                protect_algo, gcry_cipher_algo_name (protect_algo));
+      return gpg_error (GPG_ERR_CIPHER_ALGO);
+    }
+
+  if (gcry_md_test_algo (s2k_algo))
+    {
+      log_info (_("protection hash algorithm %d (%s) is not supported\n"),
+                s2k_algo, gcry_md_algo_name (s2k_algo));
+      return gpg_error (GPG_ERR_DIGEST_ALGO);
+    }
+  
+  err = gcry_cipher_open (&cipher_hd, protect_algo,
+                          GCRY_CIPHER_MODE_CFB,
+                          (GCRY_CIPHER_SECURE
+                           | (protect_algo >= 100 ?
+                              0 : GCRY_CIPHER_ENABLE_SYNC)));
+  if (err)
+    {
+      log_error ("failed to open cipher_algo %d: %s\n",
+                 protect_algo, gpg_strerror (err));
+      return err;
+    }
+
+  err = hash_passphrase_and_set_key (passphrase, cipher_hd, protect_algo,
+                                     s2k_mode, s2k_algo, s2k_salt, s2k_count);
+  if (err)
+    {
+      gcry_cipher_close (cipher_hd);
+      return err;
+    }  
+
+  gcry_cipher_setiv (cipher_hd, protect_iv, protect_ivlen);
+  
+  actual_csum = 0;
+  if (pkt_version >= 4)
+    {
+      int ndata;
+      unsigned int ndatabits;
+      unsigned char *p, *data;
+      u16 csum_pgp7 = 0;
+
+      if (!gcry_mpi_get_flag (skey[npkey], GCRYMPI_FLAG_OPAQUE ))
+        {
+          gcry_cipher_close (cipher_hd);
+          return gpg_error (GPG_ERR_BAD_SECKEY);
+        }
+      p = gcry_mpi_get_opaque (skey[npkey], &ndatabits);
+      ndata = (ndatabits+7)/8;
+
+      if (ndata > 1)
+        csum_pgp7 = p[ndata-2] << 8 | p[ndata-1];
+      data = xtrymalloc_secure (ndata);
+      if (!data)
+        {
+          err = gpg_error_from_syserror ();
+          gcry_cipher_close (cipher_hd);
+          return err;
+        }
+      gcry_cipher_decrypt (cipher_hd, data, ndata, p, ndata);
+
+      p = data;
+      if (is_protected == 2)
+        {
+          /* This is the new SHA1 checksum method to detect tampering
+             with the key as used by the Klima/Rosa attack.  */
+          desired_csum = 0; 
+          actual_csum = 1;  /* Default to bad checksum.  */
+
+          if (ndata < 20) 
+            log_error ("not enough bytes for SHA-1 checksum\n");
+          else 
+            {
+              gcry_md_hd_t h;
+              
+              if (gcry_md_open (&h, GCRY_MD_SHA1, 1))
+                BUG(); /* Algo not available. */
+              gcry_md_write (h, data, ndata - 20);
+              gcry_md_final (h);
+              if (!memcmp (gcry_md_read (h, GCRY_MD_SHA1), data+ndata-20, 20))
+                actual_csum = 0; /* Digest does match.  */
+              gcry_md_close (h);
+            }
+        }
+      else 
+        {
+          /* Old 16 bit checksum method.  */
+          if (ndata < 2)
+            {
+              log_error ("not enough bytes for checksum\n");
+              desired_csum = 0; 
+              actual_csum = 1;  /* Mark checksum bad.  */
+            }
+          else
+            {
+              desired_csum = (data[ndata-2] << 8 | data[ndata-1]);
+              actual_csum = checksum (data, ndata-2);
+              if (desired_csum != actual_csum)
+                {
+                  /* This is a PGP 7.0.0 workaround */
+                  desired_csum = csum_pgp7; /* Take the encrypted one.  */
+                }
+            }
+        }
+      
+      /* Better check it here.  Otherwise the gcry_mpi_scan would fail
+         because the length may have an arbitrary value.  */
+      if (desired_csum == actual_csum)
+        {
+          for (i=npkey; i < nskey; i++ )
+            {
+              if (gcry_mpi_scan (&tmpmpi, GCRYMPI_FMT_PGP, p, ndata, &nbytes))
+                {
+                  /* Checksum was okay, but not correctly decrypted.  */
+                  desired_csum = 0;
+                  actual_csum = 1;   /* Mark checksum bad.  */
+                  break;
+                }
+              gcry_mpi_release (skey[i]);
+              skey[i] = tmpmpi;
+              ndata -= nbytes;
+              p += nbytes;
+            }
+          skey[i] = NULL;
+          skeylen = i;
+          assert (skeylen <= skeysize);
+
+          /* Note: at this point NDATA should be 2 for a simple
+             checksum or 20 for the sha1 digest.  */
+        }
+      xfree(data);
+    }
+  else /* Packet version <= 3.  */
+    {
+      unsigned char *buffer;
+
+      for (i = npkey; i < nskey; i++)
+        {
+          unsigned char *p;
+          size_t ndata;
+          unsigned int ndatabits;
+
+          if (!skey[i] || !gcry_mpi_get_flag (skey[i], GCRYMPI_FLAG_OPAQUE))
+            {
+              gcry_cipher_close (cipher_hd);
+              return gpg_error (GPG_ERR_BAD_SECKEY);
+            }
+          p = gcry_mpi_get_opaque (skey[i], &ndatabits);
+          ndata = (ndatabits+7)/8;
+
+          if (!(ndata >= 2) || !(ndata == ((p[0] << 8 | p[1]) + 7)/8 + 2))
+            {
+              gcry_cipher_close (cipher_hd);
+              return gpg_error (GPG_ERR_BAD_SECKEY);
+            }
+          
+          buffer = xtrymalloc_secure (ndata);
+          if (!buffer)
+            {
+              err = gpg_error_from_syserror ();
+              gcry_cipher_close (cipher_hd);
+              return err;
+            }
+              
+          gcry_cipher_sync (cipher_hd);
+          buffer[0] = p[0];
+          buffer[1] = p[1];
+          gcry_cipher_decrypt (cipher_hd, buffer+2, ndata-2, p+2, ndata-2);
+          actual_csum += checksum (buffer, ndata);
+          err = gcry_mpi_scan (&tmpmpi, GCRYMPI_FMT_PGP, buffer, ndata, &ndata);
+          xfree (buffer);
+          if (err)
+            {
+              /* Checksum was okay, but not correctly decrypted.  */
+              desired_csum = 0;
+              actual_csum = 1;   /* Mark checksum bad.  */
+              break;
+            }
+          gcry_mpi_release (skey[i]);
+          skey[i] = tmpmpi;
+        }
+    }
+  gcry_cipher_close (cipher_hd);
+
+  /* Now let's see whether we have used the correct passphrase. */
+  if (actual_csum != desired_csum)
+    return gpg_error (GPG_ERR_BAD_PASSPHRASE);
+
+  if (nskey != skeylen)
+    err = gpg_error (GPG_ERR_BAD_SECKEY);
+  else
+    err = convert_secret_key (r_key, pubkey_algo, skey);
+  if (err)
+    return err;
+
+  /* The checksum may fail, thus we also check the key itself.  */
+  err = gcry_pk_testkey (*r_key);
+  if (err)
+    {
+      gcry_sexp_release (*r_key);
+      *r_key = NULL;
+      return gpg_error (GPG_ERR_BAD_PASSPHRASE);
+    }
+
+  return 0;
+}
+
+
+/* Callback function to try the unprotection from the passpharse query
+   code.  */
+static int
+try_do_unprotect_cb (struct pin_entry_info_s *pi)
+{
+  gpg_error_t err;
+  struct try_do_unprotect_arg_s *arg = pi->check_cb_arg;
+
+  err = do_unprotect (pi->pin, arg->is_v4? 4:3,
+                      arg->pubkey_algo, arg->is_protected,
+                      arg->skey, arg->skeysize,
+                      arg->protect_algo, arg->iv, arg->ivlen,
+                      arg->s2k_mode, arg->s2k_algo,
+                      arg->s2k_salt, arg->s2k_count,
+                      arg->desired_csum, arg->r_key);
+  /* SKEY may be modified now, thus we need to re-compute SKEYIDX.  */
+  for (arg->skeyidx = 0; (arg->skeyidx < arg->skeysize
+                          && arg->skey[arg->skeyidx]); arg->skeyidx++)
+         ;
+  return err;
+}
+
+
+/* Convert an OpenPGP transfer key into our internal format.  Before
+   asking for a passphrase we check whether the key already exists in
+   our key storage.  S_PGP is the OpenPGP key in transfer format.  On
+   success R_KEY will receive a canonical encoded S-expression with
+   the unprotected key in our internal format; the caller needs to
+   release that memory.  The passphrase used to decrypt the OpenPGP
+   key will be returned at R_PASSPHRASE; the caller must release this
+   passphrase.  The keygrip will be stored at the 20 byte buffer
+   pointed to by GRIP.  On error NULL is stored at all return
+   arguments.  */
+gpg_error_t
+convert_openpgp (ctrl_t ctrl, gcry_sexp_t s_pgp, 
+                 unsigned char *grip, const char *prompt,
+                 unsigned char **r_key, char **r_passphrase)
+{
+  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.  */
+  u16 desired_csum;
+  int skeyidx = 0;
+  gcry_sexp_t s_skey;
+  struct pin_entry_info_s *pi;
+  struct try_do_unprotect_arg_s pi_arg;
+
+  *r_key = NULL;
+  *r_passphrase = NULL;
+
+  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);
+      if (!protect_algo && !!strcmp (string, "IDEA"))
+        protect_algo = GCRY_CIPHER_IDEA;
+      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)
+    goto bad_seckey;
+
+  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 = 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"); */
+  /*   } */
+
+  err = get_keygrip (pubkey_algo, skey, grip);
+  if (err)
+    goto leave;
+
+  if (!agent_key_available (grip))
+    {
+      err = gpg_error (GPG_ERR_EEXIST);
+      goto leave;
+    }
+
+  pi = xtrycalloc_secure (1, sizeof (*pi) + 100);
+  if (!pi)
+    return gpg_error_from_syserror ();
+  pi->max_length = 100;
+  pi->min_digits = 0;  /* We want a real passphrase.  */
+  pi->max_digits = 16;
+  pi->max_tries = 3;
+  pi->check_cb = try_do_unprotect_cb;
+  pi->check_cb_arg = &pi_arg;
+  pi_arg.is_v4 = is_v4;
+  pi_arg.is_protected = is_protected;
+  pi_arg.pubkey_algo = pubkey_algo;
+  pi_arg.protect_algo = protect_algo;
+  pi_arg.iv = iv;
+  pi_arg.ivlen = ivlen;
+  pi_arg.s2k_mode = s2k_mode;
+  pi_arg.s2k_algo = s2k_algo;
+  pi_arg.s2k_salt = s2k_salt;
+  pi_arg.s2k_count = s2k_count;
+  pi_arg.desired_csum = desired_csum;
+  pi_arg.skey = skey;
+  pi_arg.skeysize = DIM (skey);
+  pi_arg.skeyidx = skeyidx;
+  pi_arg.r_key = &s_skey;
+  err = agent_askpin (ctrl, prompt, NULL, NULL, pi);
+  skeyidx = pi_arg.skeyidx;
+  if (!err)
+    {
+      *r_passphrase = xtrystrdup (pi->pin);
+      if (!*r_passphrase)
+        err = gpg_error_from_syserror ();
+    }
+  xfree (pi);
+  if (err)
+    goto leave;
+
+  /* Save some memory and get rid of the SKEY array now.  */
+  for (idx=0; idx < skeyidx; idx++)
+    gcry_mpi_release (skey[idx]);
+  skeyidx = 0;
+
+  /* Note that the padding is not required - we use it only because
+     that function allows us to created the result in secure memory.  */
+  err = make_canon_sexp_pad (s_skey, 1, r_key, NULL);
+  gcry_sexp_release (s_skey);
+
+ leave:
+  gcry_sexp_release (list);
+  gcry_sexp_release (top_list);
+  for (idx=0; idx < skeyidx; idx++)
+    gcry_mpi_release (skey[idx]);
+  if (err)
+    {
+      xfree (*r_passphrase);
+      *r_passphrase = NULL;
+    }
+  return err;
+
+ bad_seckey:
+  err = gpg_error (GPG_ERR_BAD_SECKEY);
+  goto leave;
+  
+ outofmem:
+  err = gpg_error (GPG_ERR_ENOMEM);
+  goto leave;
+
+}
+
+
+