Adding upstream version 2.2.40.upstream/2.2.40upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1827 insertions, 0 deletions

diff --git a/agent/findkey.c b/agent/findkey.c
new file mode 100644
index 0000000..dadcc3c
--- /dev/null
+++ b/agent/findkey.c
@@ -0,0 +1,1827 @@
+/* findkey.c - Locate the secret key
+ * Copyright (C) 2001, 2002, 2003, 2004, 2005, 2007,
+ *               2010, 2011 Free Software Foundation, Inc.
+ * Copyright (C) 2014 Werner Koch
+ *
+ * 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 <https://www.gnu.org/licenses/>.
+ */
+
+#include <config.h>
+#include <errno.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <ctype.h>
+#include <fcntl.h>
+#include <assert.h>
+#include <unistd.h>
+#include <sys/stat.h>
+#include <assert.h>
+#include <npth.h> /* (we use pth_sleep) */
+
+#include "agent.h"
+#include "../common/i18n.h"
+#include "../common/ssh-utils.h"
+#include "../common/name-value.h"
+
+#ifndef O_BINARY
+#define O_BINARY 0
+#endif
+
+/* Helper to pass data to the check callback of the unprotect function. */
+struct try_unprotect_arg_s
+{
+  ctrl_t ctrl;
+  const unsigned char *protected_key;
+  unsigned char *unprotected_key;
+  int change_required; /* Set by the callback to indicate that the
+                          user should change the passphrase.  */
+};
+
+
+/* Return the file name for the 20 byte keygrip GRIP.  Return NULL on
+ * error. */
+static char *
+fname_from_keygrip (const unsigned char *grip)
+{
+  char hexgrip[40+4+1];
+
+  bin2hex (grip, 20, hexgrip);
+  strcpy (hexgrip+40, ".key");
+
+  return make_filename_try (gnupg_homedir (), GNUPG_PRIVATE_KEYS_DIR,
+                            hexgrip, NULL);
+}
+
+
+/* Note: Ownership of FNAME and FP are moved to this function.
+ * OLD_FORMAT is true if the file exists but is still in the
+ * non-extended mode format.  If MAYBE_UPDATE is set the function
+ * assumes that the file exists but writes it only if it figures that
+ * an update is required.  */
+static gpg_error_t
+write_extended_private_key (int maybe_update,
+                            char *fname, estream_t fp,
+                            int old_format, int newkey,
+                            const void *buf, size_t len, time_t timestamp,
+                            const char *serialno, const char *keyref,
+                            const char *dispserialno)
+{
+  gpg_error_t err;
+  nvc_t pk = NULL;
+  gcry_sexp_t key = NULL;
+  int remove = 0;
+  char *token0 = NULL;
+  char *token = NULL;
+  char *dispserialno_buffer = NULL;
+  char **tokenfields = NULL;
+
+  if (old_format || newkey)
+    {
+      /* We must create a new NVC if the key is still in the old
+       * format and of course if it is a new key.  */
+      pk = nvc_new_private_key ();
+      if (!pk)
+        {
+          err = gpg_error_from_syserror ();
+          goto leave;
+        }
+      maybe_update = 0; /* Always write.  */
+    }
+  else
+    { /* Parse the existing NVC.  */
+      int lineno = 0;
+
+      err = nvc_parse_private_key (&pk, &lineno, fp);
+      if (err)
+        {
+          log_error ("error parsing '%s' line %d: %s\n",
+                     fname, lineno, gpg_strerror (err));
+          goto leave;
+        }
+    }
+  es_clearerr (fp);
+
+  err = gcry_sexp_sscan (&key, NULL, buf, len);
+  if (err)
+    goto leave;
+
+  err = nvc_set_private_key (pk, key);
+  if (err)
+    goto leave;
+
+  /* If a timestamp has been supplied and the key is new write a
+   * creation timestamp.  Note that we can't add this item if we are
+   * still in the old format.  We also add an extra check that there
+   * is no Created item yet.  */
+  if (timestamp && newkey && !nvc_lookup (pk, "Created:"))
+    {
+      gnupg_isotime_t timebuf;
+
+      epoch2isotime (timebuf, timestamp);
+      err = nvc_add (pk, "Created:", timebuf);
+      if (err)
+        goto leave;
+    }
+
+  /* If requested write a Token line.  */
+  if (serialno && keyref)
+    {
+      nve_t item;
+      const char *s;
+      size_t token0len;
+
+      if (dispserialno)
+        {
+          /* Escape the DISPSERIALNO.  */
+          dispserialno_buffer = percent_plus_escape (dispserialno);
+          if (!dispserialno_buffer)
+            {
+              err = gpg_error_from_syserror ();
+              goto leave;
+            }
+          dispserialno = dispserialno_buffer;
+        }
+
+      token0 = strconcat (serialno, " ", keyref, NULL);
+      if (token0)
+        token = strconcat (token0, " - ", dispserialno? dispserialno:"-", NULL);
+      if (!token0 || !token)
+        {
+          err = gpg_error_from_syserror ();
+          goto leave;
+        }
+
+      token0len = strlen (token0);
+      for (item = nvc_lookup (pk, "Token:");
+           item;
+           item = nve_next_value (item, "Token:"))
+        if ((s = nve_value (item)) && !strncmp (s, token0, token0len))
+          break;
+      if (!item)
+        {
+          /* No token or no token with that value exists.  Add a new
+           * one so that keys which have been stored on several cards
+           * are well supported.  */
+          err = nvc_add (pk, "Token:", token);
+          if (err)
+            goto leave;
+          maybe_update = 0; /* Force write.  */
+        }
+      else
+        {
+          /* Token exists: Update the display s/n.  It may have
+           * changed due to changes in a newer software version.  */
+          if (maybe_update && s && (tokenfields = strtokenize (s, " \t\n"))
+              && tokenfields[0] && tokenfields[1] && tokenfields[2]
+              && tokenfields[3]
+              && !strcmp (tokenfields[3], dispserialno))
+            ; /* No need to update Token entry.  */
+          else
+            {
+              err = nve_set (item, token);
+              if (err)
+                goto leave;
+              maybe_update = 0; /* Force write.  */
+            }
+        }
+    }
+
+  err = es_fseek (fp, 0, SEEK_SET);
+  if (err)
+    goto leave;
+
+  if (!maybe_update)
+    {
+      err = nvc_write (pk, fp);
+      if (!err)
+        err = es_fflush (fp);
+      if (err)
+        {
+          log_error ("error writing '%s': %s\n", fname, gpg_strerror (err));
+          remove = 1;
+          goto leave;
+        }
+
+      if (ftruncate (es_fileno (fp), es_ftello (fp)))
+        {
+          err = gpg_error_from_syserror ();
+          log_error ("error truncating '%s': %s\n", fname, gpg_strerror (err));
+          remove = 1;
+          goto leave;
+        }
+    }
+
+  if (es_fclose (fp))
+    {
+      err = gpg_error_from_syserror ();
+      log_error ("error closing '%s': %s\n", fname, gpg_strerror (err));
+      remove = 1;
+      goto leave;
+    }
+  else
+    fp = NULL;
+
+  if (!maybe_update)
+    bump_key_eventcounter ();
+
+ leave:
+  es_fclose (fp);
+  if (remove)
+    gnupg_remove (fname);
+  xfree (fname);
+  xfree (token);
+  xfree (token0);
+  xfree (dispserialno_buffer);
+  xfree (tokenfields);
+  gcry_sexp_release (key);
+  nvc_release (pk);
+  return err;
+}
+
+/* Write an S-expression formatted key to our key storage.  With FORCE
+ * passed as true an existing key with the given GRIP will get
+ * overwritten.  If TIMESTAMP is not zero and the key does not yet
+ * exists it will be recorded as creation date.  If SERIALNO, KEYREF,
+ * of DISPSERIALNO are not NULL they will be recorded as well.  */
+int
+agent_write_private_key (const unsigned char *grip,
+                         const void *buffer, size_t length,
+                         int force, time_t timestamp,
+                         const char *serialno, const char *keyref,
+                         const char *dispserialno)
+{
+  char *fname;
+  estream_t fp;
+
+  fname = fname_from_keygrip (grip);
+  if (!fname)
+    return gpg_error_from_syserror ();
+
+  /* FIXME: Write to a temp file first so that write failures during
+     key updates won't lead to a key loss.  */
+
+  if (!force && !gnupg_access (fname, F_OK))
+    {
+      log_error ("secret key file '%s' already exists\n", fname);
+      xfree (fname);
+      return gpg_error (GPG_ERR_EEXIST);
+    }
+
+  fp = es_fopen (fname, force? "rb+,mode=-rw" : "wbx,mode=-rw");
+  if (!fp)
+    {
+      gpg_error_t tmperr = gpg_error_from_syserror ();
+
+      if (force && gpg_err_code (tmperr) == GPG_ERR_ENOENT)
+        {
+          fp = es_fopen (fname, "wbx,mode=-rw");
+          if (!fp)
+            tmperr = gpg_error_from_syserror ();
+        }
+      if (!fp)
+        {
+          log_error ("can't create '%s': %s\n", fname, gpg_strerror (tmperr));
+          xfree (fname);
+          return tmperr;
+        }
+    }
+  else if (force)
+    {
+      gpg_error_t rc;
+      char first;
+
+      /* See if an existing key is in extended format.  */
+      if (es_fread (&first, 1, 1, fp) != 1)
+        {
+          rc = gpg_error_from_syserror ();
+          log_error ("error reading first byte from '%s': %s\n",
+                     fname, strerror (errno));
+          xfree (fname);
+          es_fclose (fp);
+          return rc;
+        }
+
+      rc = es_fseek (fp, 0, SEEK_SET);
+      if (rc)
+        {
+          log_error ("error seeking in '%s': %s\n", fname, strerror (errno));
+          xfree (fname);
+          es_fclose (fp);
+          return rc;
+        }
+
+      if (first != '(')
+        {
+          /* Key is already in the extended format.  */
+          return write_extended_private_key (0, fname, fp, 0, 0,
+                                             buffer, length,
+                                             timestamp, serialno, keyref,
+                                             dispserialno);
+        }
+      if (first == '(' && opt.enable_extended_key_format)
+        {
+          /* Key is in the old format - but we want the extended format.  */
+          return write_extended_private_key (0, fname, fp, 1, 0,
+                                             buffer, length,
+                                             timestamp, serialno, keyref,
+                                             dispserialno);
+        }
+    }
+
+  if (opt.enable_extended_key_format)
+    return write_extended_private_key (0, fname, fp, 0, 1,
+                                       buffer, length,
+                                       timestamp, serialno, keyref,
+                                       dispserialno);
+
+  if (es_fwrite (buffer, length, 1, fp) != 1)
+    {
+      gpg_error_t tmperr = gpg_error_from_syserror ();
+      log_error ("error writing '%s': %s\n", fname, gpg_strerror (tmperr));
+      es_fclose (fp);
+      gnupg_remove (fname);
+      xfree (fname);
+      return tmperr;
+    }
+
+  /* When force is given, the file might have to be truncated.  */
+  if (force && ftruncate (es_fileno (fp), es_ftello (fp)))
+    {
+      gpg_error_t tmperr = gpg_error_from_syserror ();
+      log_error ("error truncating '%s': %s\n", fname, gpg_strerror (tmperr));
+      es_fclose (fp);
+      gnupg_remove (fname);
+      xfree (fname);
+      return tmperr;
+    }
+
+  if (es_fclose (fp))
+    {
+      gpg_error_t tmperr = gpg_error_from_syserror ();
+      log_error ("error closing '%s': %s\n", fname, gpg_strerror (tmperr));
+      gnupg_remove (fname);
+      xfree (fname);
+      return tmperr;
+    }
+  bump_key_eventcounter ();
+  xfree (fname);
+  return 0;
+}
+
+
+/* Callback function to try the unprotection from the passphrase query
+   code. */
+static gpg_error_t
+try_unprotect_cb (struct pin_entry_info_s *pi)
+{
+  struct try_unprotect_arg_s *arg = pi->check_cb_arg;
+  ctrl_t ctrl = arg->ctrl;
+  size_t dummy;
+  gpg_error_t err;
+  gnupg_isotime_t now, protected_at, tmptime;
+  char *desc = NULL;
+
+  assert (!arg->unprotected_key);
+
+  arg->change_required = 0;
+  err = agent_unprotect (ctrl, arg->protected_key, pi->pin, protected_at,
+                         &arg->unprotected_key, &dummy);
+  if (err)
+    return err;
+  if (!opt.max_passphrase_days || ctrl->in_passwd)
+    return 0;  /* No regular passphrase change required.  */
+
+  if (!*protected_at)
+    {
+      /* No protection date known - must force passphrase change.  */
+      desc = xtrystrdup (L_("Note: This passphrase has never been changed.%0A"
+                            "Please change it now."));
+      if (!desc)
+        return gpg_error_from_syserror ();
+    }
+  else
+    {
+      gnupg_get_isotime (now);
+      gnupg_copy_time (tmptime, protected_at);
+      err = add_days_to_isotime (tmptime, opt.max_passphrase_days);
+      if (err)
+        return err;
+      if (strcmp (now, tmptime) > 0 )
+        {
+          /* Passphrase "expired".  */
+          desc = xtryasprintf
+            (L_("This passphrase has not been changed%%0A"
+                "since %.4s-%.2s-%.2s.  Please change it now."),
+             protected_at, protected_at+4, protected_at+6);
+          if (!desc)
+            return gpg_error_from_syserror ();
+        }
+    }
+
+  if (desc)
+    {
+      /* Change required.  */
+      if (opt.enforce_passphrase_constraints)
+        {
+          err = agent_get_confirmation (ctrl, desc,
+                                        L_("Change passphrase"), NULL, 0);
+          if (!err)
+            arg->change_required = 1;
+        }
+      else
+        {
+          err = agent_get_confirmation (ctrl, desc,
+                                        L_("Change passphrase"),
+                                        L_("I'll change it later"), 0);
+          if (!err)
+            arg->change_required = 1;
+          else if (gpg_err_code (err) == GPG_ERR_CANCELED
+                   || gpg_err_code (err) == GPG_ERR_FULLY_CANCELED)
+            err = 0;
+        }
+      xfree (desc);
+    }
+
+  return err;
+}
+
+
+/* Modify a Key description, replacing certain special format
+   characters.  List of currently supported replacements:
+
+   %% - Replaced by a single %
+   %c - Replaced by the content of COMMENT.
+   %C - Same as %c but put into parentheses.
+   %F - Replaced by an ssh style fingerprint computed from KEY.
+
+   The functions returns 0 on success or an error code.  On success a
+   newly allocated string is stored at the address of RESULT.
+ */
+gpg_error_t
+agent_modify_description (const char *in, const char *comment,
+                          const gcry_sexp_t key, char **result)
+{
+  size_t comment_length;
+  size_t in_len;
+  size_t out_len;
+  char *out;
+  size_t i;
+  int special, pass;
+  char *ssh_fpr = NULL;
+  char *p;
+
+  *result = NULL;
+
+  if (!comment)
+    comment = "";
+
+  comment_length = strlen (comment);
+  in_len  = strlen (in);
+
+  /* First pass calculates the length, second pass does the actual
+     copying.  */
+  /* FIXME: This can be simplified by using es_fopenmem.  */
+  out = NULL;
+  out_len = 0;
+  for (pass=0; pass < 2; pass++)
+    {
+      special = 0;
+      for (i = 0; i < in_len; i++)
+        {
+          if (special)
+            {
+              special = 0;
+              switch (in[i])
+                {
+                case '%':
+                  if (out)
+                    *out++ = '%';
+                  else
+                    out_len++;
+                  break;
+
+                case 'c': /* Comment.  */
+                  if (out)
+                    {
+                      memcpy (out, comment, comment_length);
+                      out += comment_length;
+                    }
+                  else
+                    out_len += comment_length;
+                  break;
+
+                case 'C': /* Comment.  */
+                  if (!comment_length)
+                    ;
+                  else if (out)
+                    {
+                      *out++ = '(';
+                      memcpy (out, comment, comment_length);
+                      out += comment_length;
+                      *out++ = ')';
+                    }
+                  else
+                    out_len += comment_length + 2;
+                  break;
+
+                case 'F': /* SSH style fingerprint.  */
+                  if (!ssh_fpr && key)
+                    ssh_get_fingerprint_string (key, opt.ssh_fingerprint_digest,
+                                                &ssh_fpr);
+                  if (ssh_fpr)
+                    {
+                      if (out)
+                        out = stpcpy (out, ssh_fpr);
+                      else
+                        out_len += strlen (ssh_fpr);
+                    }
+                  break;
+
+                default: /* Invalid special sequences are kept as they are. */
+                  if (out)
+                    {
+                      *out++ = '%';
+                      *out++ = in[i];
+                    }
+                  else
+                    out_len+=2;
+                  break;
+                }
+            }
+          else if (in[i] == '%')
+            special = 1;
+          else
+            {
+              if (out)
+                *out++ = in[i];
+              else
+                out_len++;
+            }
+        }
+
+      if (!pass)
+        {
+          *result = out = xtrymalloc (out_len + 1);
+          if (!out)
+            {
+              xfree (ssh_fpr);
+              return gpg_error_from_syserror ();
+            }
+        }
+    }
+
+  *out = 0;
+  log_assert (*result + out_len == out);
+  xfree (ssh_fpr);
+
+  /* The ssh prompt may sometimes end in
+   *    "...%0A  ()"
+   * The empty parentheses doesn't look very good.  We use this hack
+   * here to remove them as well as the indentation spaces. */
+  p = *result;
+  i = strlen (p);
+  if (i > 2 && !strcmp (p + i - 2, "()"))
+    {
+      p += i - 2;
+      *p-- = 0;
+      while (p > *result && spacep (p))
+        *p-- = 0;
+    }
+
+  return 0;
+}
+
+
+
+/* Unprotect the canconical encoded S-expression key in KEYBUF.  GRIP
+   should be the hex encoded keygrip of that key to be used with the
+   caching mechanism. DESC_TEXT may be set to override the default
+   description used for the pinentry.  If LOOKUP_TTL is given this
+   function is used to lookup the default ttl.  If R_PASSPHRASE is not
+   NULL, the function succeeded and the key was protected the used
+   passphrase (entered or from the cache) is stored there; if not NULL
+   will be stored.  The caller needs to free the returned
+   passphrase. */
+static gpg_error_t
+unprotect (ctrl_t ctrl, const char *cache_nonce, const char *desc_text,
+           unsigned char **keybuf, const unsigned char *grip,
+           cache_mode_t cache_mode, lookup_ttl_t lookup_ttl,
+           char **r_passphrase)
+{
+  struct pin_entry_info_s *pi;
+  struct try_unprotect_arg_s arg;
+  int rc;
+  unsigned char *result;
+  size_t resultlen;
+  char hexgrip[40+1];
+
+  if (r_passphrase)
+    *r_passphrase = NULL;
+
+  bin2hex (grip, 20, hexgrip);
+
+  /* Initially try to get it using a cache nonce.  */
+  if (cache_nonce)
+    {
+      char *pw;
+
+      pw = agent_get_cache (ctrl, cache_nonce, CACHE_MODE_NONCE);
+      if (pw)
+        {
+          rc = agent_unprotect (ctrl, *keybuf, pw, NULL, &result, &resultlen);
+          if (!rc)
+            {
+              if (r_passphrase)
+                *r_passphrase = pw;
+              else
+                xfree (pw);
+              xfree (*keybuf);
+              *keybuf = result;
+              return 0;
+            }
+          xfree (pw);
+        }
+    }
+
+  /* First try to get it from the cache - if there is none or we can't
+     unprotect it, we fall back to ask the user */
+  if (cache_mode != CACHE_MODE_IGNORE)
+    {
+      char *pw;
+
+    retry:
+      pw = agent_get_cache (ctrl, hexgrip, cache_mode);
+      if (pw)
+        {
+          rc = agent_unprotect (ctrl, *keybuf, pw, NULL, &result, &resultlen);
+          if (!rc)
+            {
+              if (cache_mode == CACHE_MODE_NORMAL)
+                agent_store_cache_hit (hexgrip);
+              if (r_passphrase)
+                *r_passphrase = pw;
+              else
+                xfree (pw);
+              xfree (*keybuf);
+              *keybuf = result;
+              return 0;
+            }
+          xfree (pw);
+        }
+      else if (cache_mode == CACHE_MODE_NORMAL)
+        {
+          /* The standard use of GPG keys is to have a signing and an
+             encryption subkey.  Commonly both use the same
+             passphrase.  We try to help the user to enter the
+             passphrase only once by silently trying the last
+             correctly entered passphrase.  Checking one additional
+             passphrase should be acceptable; despite the S2K
+             introduced delays. The assumed workflow is:
+
+               1. Read encrypted message in a MUA and thus enter a
+                  passphrase for the encryption subkey.
+
+               2. Reply to that mail with an encrypted and signed
+                  mail, thus entering the passphrase for the signing
+                  subkey.
+
+             We can often avoid the passphrase entry in the second
+             step.  We do this only in normal mode, so not to
+             interfere with unrelated cache entries.  */
+          pw = agent_get_cache (ctrl, NULL, cache_mode);
+          if (pw)
+            {
+              rc = agent_unprotect (ctrl, *keybuf, pw, NULL,
+                                    &result, &resultlen);
+              if (!rc)
+                {
+                  if (r_passphrase)
+                    *r_passphrase = pw;
+                  else
+                    xfree (pw);
+                  xfree (*keybuf);
+                  *keybuf = result;
+                  return 0;
+                }
+              xfree (pw);
+            }
+        }
+
+      /* If the pinentry is currently in use, we wait up to 60 seconds
+         for it to close and check the cache again.  This solves a common
+         situation where several requests for unprotecting a key have
+         been made but the user is still entering the passphrase for
+         the first request.  Because all requests to agent_askpin are
+         serialized they would then pop up one after the other to
+         request the passphrase - despite that the user has already
+         entered it and is then available in the cache.  This
+         implementation is not race free but in the worst case the
+         user has to enter the passphrase only once more. */
+      if (pinentry_active_p (ctrl, 0))
+        {
+          /* Active - wait */
+          if (!pinentry_active_p (ctrl, 60))
+            {
+              /* We need to give the other thread a chance to actually put
+                 it into the cache. */
+              npth_sleep (1);
+              goto retry;
+            }
+          /* Timeout - better call pinentry now the plain way. */
+        }
+    }
+
+  pi = gcry_calloc_secure (1, sizeof (*pi) + MAX_PASSPHRASE_LEN + 1);
+  if (!pi)
+    return gpg_error_from_syserror ();
+  pi->max_length = MAX_PASSPHRASE_LEN + 1;
+  pi->min_digits = 0;  /* we want a real passphrase */
+  pi->max_digits = 16;
+  pi->max_tries = 3;
+  pi->check_cb = try_unprotect_cb;
+  arg.ctrl = ctrl;
+  arg.protected_key = *keybuf;
+  arg.unprotected_key = NULL;
+  arg.change_required = 0;
+  pi->check_cb_arg = &arg;
+
+  rc = agent_askpin (ctrl, desc_text, NULL, NULL, pi, hexgrip, cache_mode);
+  if (rc)
+    {
+      if ((pi->status & PINENTRY_STATUS_PASSWORD_FROM_CACHE))
+        {
+          log_error ("Clearing pinentry cache which caused error %s\n",
+                     gpg_strerror (rc));
+
+          agent_clear_passphrase (ctrl, hexgrip, cache_mode);
+        }
+    }
+  else
+    {
+      assert (arg.unprotected_key);
+      if (arg.change_required)
+        {
+          /* The callback told as that the user should change their
+             passphrase.  Present the dialog to do.  */
+          size_t canlen, erroff;
+          gcry_sexp_t s_skey;
+
+          assert (arg.unprotected_key);
+          canlen = gcry_sexp_canon_len (arg.unprotected_key, 0, NULL, NULL);
+          rc = gcry_sexp_sscan (&s_skey, &erroff,
+                                (char*)arg.unprotected_key, canlen);
+          if (rc)
+            {
+              log_error ("failed to build S-Exp (off=%u): %s\n",
+                         (unsigned int)erroff, gpg_strerror (rc));
+              wipememory (arg.unprotected_key, canlen);
+              xfree (arg.unprotected_key);
+              xfree (pi);
+              return rc;
+            }
+          rc = agent_protect_and_store (ctrl, s_skey, NULL);
+          gcry_sexp_release (s_skey);
+          if (rc)
+            {
+              log_error ("changing the passphrase failed: %s\n",
+                         gpg_strerror (rc));
+              wipememory (arg.unprotected_key, canlen);
+              xfree (arg.unprotected_key);
+              xfree (pi);
+              return rc;
+            }
+        }
+      else
+        {
+          /* Passphrase is fine.  */
+          agent_put_cache (ctrl, hexgrip, cache_mode, pi->pin,
+                           lookup_ttl? lookup_ttl (hexgrip) : 0);
+          agent_store_cache_hit (hexgrip);
+          if (r_passphrase && *pi->pin)
+            *r_passphrase = xtrystrdup (pi->pin);
+        }
+      xfree (*keybuf);
+      *keybuf = arg.unprotected_key;
+    }
+  xfree (pi);
+  return rc;
+}
+
+
+/* Read the key identified by GRIP from the private key directory and
+ * return it as an gcrypt S-expression object in RESULT.  If R_KEYMETA
+ * is not NULl and the extended key format is used, the meta data
+ * items are stored there.  However the "Key:" item is removed from
+ * it.  On failure returns an error code and stores NULL at RESULT. */
+static gpg_error_t
+read_key_file (const unsigned char *grip, gcry_sexp_t *result, nvc_t *r_keymeta)
+{
+  gpg_error_t err;
+  char *fname;
+  estream_t fp;
+  struct stat st;
+  unsigned char *buf;
+  size_t buflen, erroff;
+  gcry_sexp_t s_skey;
+  char hexgrip[40+4+1];
+  char first;
+
+  *result = NULL;
+  if (r_keymeta)
+    *r_keymeta = NULL;
+
+  bin2hex (grip, 20, hexgrip);
+  strcpy (hexgrip+40, ".key");
+
+  fname = make_filename (gnupg_homedir (), GNUPG_PRIVATE_KEYS_DIR,
+                         hexgrip, NULL);
+  fp = es_fopen (fname, "rb");
+  if (!fp)
+    {
+      err = gpg_error_from_syserror ();
+      if (gpg_err_code (err) != GPG_ERR_ENOENT)
+        log_error ("can't open '%s': %s\n", fname, gpg_strerror (err));
+      xfree (fname);
+      return err;
+    }
+
+  if (es_fread (&first, 1, 1, fp) != 1)
+    {
+      err = gpg_error_from_syserror ();
+      log_error ("error reading first byte from '%s': %s\n",
+                 fname, gpg_strerror (err));
+      xfree (fname);
+      es_fclose (fp);
+      return err;
+    }
+
+  if (es_fseek (fp, 0, SEEK_SET))
+    {
+      err = gpg_error_from_syserror ();
+      log_error ("error seeking in '%s': %s\n", fname, gpg_strerror (err));
+      xfree (fname);
+      es_fclose (fp);
+      return err;
+    }
+
+  if (first != '(')
+    {
+      /* Key is in extended format.  */
+      nvc_t pk;
+      int line;
+
+      err = nvc_parse_private_key (&pk, &line, fp);
+      es_fclose (fp);
+
+      if (err)
+        log_error ("error parsing '%s' line %d: %s\n",
+                   fname, line, gpg_strerror (err));
+      else
+        {
+          err = nvc_get_private_key (pk, result);
+          if (err)
+            log_error ("error getting private key from '%s': %s\n",
+                       fname, gpg_strerror (err));
+          else
+            nvc_delete_named (pk, "Key:");
+        }
+
+      if (!err && r_keymeta)
+        *r_keymeta = pk;
+      else
+        nvc_release (pk);
+      xfree (fname);
+      return err;
+    }
+
+  if (fstat (es_fileno (fp), &st))
+    {
+      err = gpg_error_from_syserror ();
+      log_error ("can't stat '%s': %s\n", fname, gpg_strerror (err));
+      xfree (fname);
+      es_fclose (fp);
+      return err;
+    }
+
+  buflen = st.st_size;
+  buf = xtrymalloc (buflen+1);
+  if (!buf)
+    {
+      err = gpg_error_from_syserror ();
+      log_error ("error allocating %zu bytes for '%s': %s\n",
+                 buflen, fname, gpg_strerror (err));
+      xfree (fname);
+      es_fclose (fp);
+      xfree (buf);
+      return err;
+
+    }
+
+  if (es_fread (buf, buflen, 1, fp) != 1)
+    {
+      err = gpg_error_from_syserror ();
+      log_error ("error reading %zu bytes from '%s': %s\n",
+                 buflen, fname, gpg_strerror (err));
+      xfree (fname);
+      es_fclose (fp);
+      xfree (buf);
+      return err;
+    }
+
+  /* Convert the file into a gcrypt S-expression object.  */
+  err = gcry_sexp_sscan (&s_skey, &erroff, (char*)buf, buflen);
+  xfree (fname);
+  es_fclose (fp);
+  xfree (buf);
+  if (err)
+    {
+      log_error ("failed to build S-Exp (off=%u): %s\n",
+                 (unsigned int)erroff, gpg_strerror (err));
+      return err;
+    }
+  *result = s_skey;
+  return 0;
+}
+
+
+/* Remove the key identified by GRIP from the private key directory.  */
+static gpg_error_t
+remove_key_file (const unsigned char *grip)
+{
+  gpg_error_t err = 0;
+  char *fname;
+  char hexgrip[40+4+1];
+
+  bin2hex (grip, 20, hexgrip);
+  strcpy (hexgrip+40, ".key");
+  fname = make_filename (gnupg_homedir (), GNUPG_PRIVATE_KEYS_DIR,
+                         hexgrip, NULL);
+  if (gnupg_remove (fname))
+    err = gpg_error_from_syserror ();
+  xfree (fname);
+  return err;
+}
+
+
+/* Return the secret key as an S-Exp in RESULT after locating it using
+   the GRIP.  If the operation shall be diverted to a token, an
+   allocated S-expression with the shadow_info part from the file is
+   stored at SHADOW_INFO; if not NULL will be stored at SHADOW_INFO.
+   CACHE_MODE defines now the cache shall be used.  DESC_TEXT may be
+   set to present a custom description for the pinentry.  LOOKUP_TTL
+   is an optional function to convey a TTL to the cache manager; we do
+   not simply pass the TTL value because the value is only needed if
+   an unprotect action was needed and looking up the TTL may have some
+   overhead (e.g. scanning the sshcontrol file).  If a CACHE_NONCE is
+   given that cache item is first tried to get a passphrase.  If
+   R_PASSPHRASE is not NULL, the function succeeded and the key was
+   protected the used passphrase (entered or from the cache) is stored
+   there; if not NULL will be stored.  The caller needs to free the
+   returned passphrase.   */
+gpg_error_t
+agent_key_from_file (ctrl_t ctrl, const char *cache_nonce,
+                     const char *desc_text,
+                     const unsigned char *grip, unsigned char **shadow_info,
+                     cache_mode_t cache_mode, lookup_ttl_t lookup_ttl,
+                     gcry_sexp_t *result, char **r_passphrase)
+{
+  gpg_error_t err;
+  unsigned char *buf;
+  size_t len, buflen, erroff;
+  gcry_sexp_t s_skey;
+
+  *result = NULL;
+  if (shadow_info)
+    *shadow_info = NULL;
+  if (r_passphrase)
+    *r_passphrase = NULL;
+
+  err = read_key_file (grip, &s_skey, NULL);
+  if (err)
+    {
+      if (gpg_err_code (err) == GPG_ERR_ENOENT)
+        err = gpg_error (GPG_ERR_NO_SECKEY);
+      return err;
+    }
+
+  /* For use with the protection functions we also need the key as an
+     canonical encoded S-expression in a buffer.  Create this buffer
+     now.  */
+  err = make_canon_sexp (s_skey, &buf, &len);
+  if (err)
+    return err;
+
+  switch (agent_private_key_type (buf))
+    {
+    case PRIVATE_KEY_CLEAR:
+      break; /* no unprotection needed */
+    case PRIVATE_KEY_OPENPGP_NONE:
+      {
+        unsigned char *buf_new;
+        size_t buf_newlen;
+
+        err = agent_unprotect (ctrl, buf, "", NULL, &buf_new, &buf_newlen);
+        if (err)
+          log_error ("failed to convert unprotected openpgp key: %s\n",
+                     gpg_strerror (err));
+        else
+          {
+            xfree (buf);
+            buf = buf_new;
+          }
+      }
+      break;
+    case PRIVATE_KEY_PROTECTED:
+      {
+	char *desc_text_final;
+	char *comment = NULL;
+
+        /* Note, that we will take the comment as a C string for
+           display purposes; i.e. all stuff beyond a Nul character is
+           ignored.  */
+        {
+          gcry_sexp_t comment_sexp;
+
+          comment_sexp = gcry_sexp_find_token (s_skey, "comment", 0);
+          if (comment_sexp)
+            comment = gcry_sexp_nth_string (comment_sexp, 1);
+          gcry_sexp_release (comment_sexp);
+        }
+
+        desc_text_final = NULL;
+	if (desc_text)
+          err = agent_modify_description (desc_text, comment, s_skey,
+                                          &desc_text_final);
+        gcry_free (comment);
+
+	if (!err)
+	  {
+	    err = unprotect (ctrl, cache_nonce, desc_text_final, &buf, grip,
+                            cache_mode, lookup_ttl, r_passphrase);
+	    if (err)
+	      log_error ("failed to unprotect the secret key: %s\n",
+			 gpg_strerror (err));
+	  }
+
+	xfree (desc_text_final);
+      }
+      break;
+    case PRIVATE_KEY_SHADOWED:
+      if (shadow_info)
+        {
+          const unsigned char *s;
+          size_t n;
+
+          err = agent_get_shadow_info (buf, &s);
+          if (!err)
+            {
+              n = gcry_sexp_canon_len (s, 0, NULL,NULL);
+              log_assert (n);
+              *shadow_info = xtrymalloc (n);
+              if (!*shadow_info)
+                err = out_of_core ();
+              else
+                {
+                  memcpy (*shadow_info, s, n);
+                  err = 0;
+                }
+            }
+          if (err)
+            log_error ("get_shadow_info failed: %s\n", gpg_strerror (err));
+        }
+      else
+        err = gpg_error (GPG_ERR_UNUSABLE_SECKEY);
+      break;
+    default:
+      log_error ("invalid private key format\n");
+      err = gpg_error (GPG_ERR_BAD_SECKEY);
+      break;
+    }
+  gcry_sexp_release (s_skey);
+  s_skey = NULL;
+  if (err)
+    {
+      xfree (buf);
+      if (r_passphrase)
+        {
+          xfree (*r_passphrase);
+          *r_passphrase = NULL;
+        }
+      return err;
+    }
+
+  buflen = gcry_sexp_canon_len (buf, 0, NULL, NULL);
+  err = gcry_sexp_sscan (&s_skey, &erroff, (char*)buf, buflen);
+  wipememory (buf, buflen);
+  xfree (buf);
+  if (err)
+    {
+      log_error ("failed to build S-Exp (off=%u): %s\n",
+                 (unsigned int)erroff, gpg_strerror (err));
+      if (r_passphrase)
+        {
+          xfree (*r_passphrase);
+          *r_passphrase = NULL;
+        }
+      return err;
+    }
+
+  *result = s_skey;
+  return 0;
+}
+
+
+/* Return the string name from the S-expression S_KEY as well as a
+   string describing the names of the parameters.  ALGONAMESIZE and
+   ELEMSSIZE give the allocated size of the provided buffers.  The
+   buffers may be NULL if not required.  If R_LIST is not NULL the top
+   level list will be stored there; the caller needs to release it in
+   this case.  */
+static gpg_error_t
+key_parms_from_sexp (gcry_sexp_t s_key, gcry_sexp_t *r_list,
+                     char *r_algoname, size_t algonamesize,
+                     char *r_elems, size_t elemssize)
+{
+  gcry_sexp_t list, l2;
+  const char *name, *algoname, *elems;
+  size_t n;
+
+  if (r_list)
+    *r_list = NULL;
+
+  list = gcry_sexp_find_token (s_key, "shadowed-private-key", 0 );
+  if (!list)
+    list = gcry_sexp_find_token (s_key, "protected-private-key", 0 );
+  if (!list)
+    list = gcry_sexp_find_token (s_key, "private-key", 0 );
+  if (!list)
+    {
+      log_error ("invalid private key format\n");
+      return gpg_error (GPG_ERR_BAD_SECKEY);
+    }
+
+  l2 = gcry_sexp_cadr (list);
+  gcry_sexp_release (list);
+  list = l2;
+  name = gcry_sexp_nth_data (list, 0, &n);
+  if (n==3 && !memcmp (name, "rsa", 3))
+    {
+      algoname = "rsa";
+      elems = "ne";
+    }
+  else if (n==3 && !memcmp (name, "dsa", 3))
+    {
+      algoname = "dsa";
+      elems = "pqgy";
+    }
+  else if (n==3 && !memcmp (name, "ecc", 3))
+    {
+      algoname = "ecc";
+      elems = "pabgnq";
+    }
+  else if (n==5 && !memcmp (name, "ecdsa", 5))
+    {
+      algoname = "ecdsa";
+      elems = "pabgnq";
+    }
+  else if (n==4 && !memcmp (name, "ecdh", 4))
+    {
+      algoname = "ecdh";
+      elems = "pabgnq";
+    }
+  else if (n==3 && !memcmp (name, "elg", 3))
+    {
+      algoname = "elg";
+      elems = "pgy";
+    }
+  else
+    {
+      log_error ("unknown private key algorithm\n");
+      gcry_sexp_release (list);
+      return gpg_error (GPG_ERR_BAD_SECKEY);
+    }
+
+  if (r_algoname)
+    {
+      if (strlen (algoname) >= algonamesize)
+        return gpg_error (GPG_ERR_BUFFER_TOO_SHORT);
+      strcpy (r_algoname, algoname);
+    }
+  if (r_elems)
+    {
+      if (strlen (elems) >= elemssize)
+        return gpg_error (GPG_ERR_BUFFER_TOO_SHORT);
+      strcpy (r_elems, elems);
+    }
+
+  if (r_list)
+    *r_list = list;
+  else
+    gcry_sexp_release (list);
+
+  return 0;
+}
+
+
+/* Return true if KEYPARMS holds an EdDSA key.  */
+static int
+is_eddsa (gcry_sexp_t keyparms)
+{
+  int result = 0;
+  gcry_sexp_t list;
+  const char *s;
+  size_t n;
+  int i;
+
+  list = gcry_sexp_find_token (keyparms, "flags", 0);
+  for (i = list ? gcry_sexp_length (list)-1 : 0; i > 0; i--)
+    {
+      s = gcry_sexp_nth_data (list, i, &n);
+      if (!s)
+        continue; /* Not a data element. */
+
+      if (n == 5 && !memcmp (s, "eddsa", 5))
+        {
+          result = 1;
+          break;
+        }
+    }
+  gcry_sexp_release (list);
+  return result;
+}
+
+
+/* Return the public key algorithm number if S_KEY is a DSA style key.
+   If it is not a DSA style key, return 0.  */
+int
+agent_is_dsa_key (gcry_sexp_t s_key)
+{
+  int result;
+  gcry_sexp_t list;
+  char algoname[6];
+
+  if (!s_key)
+    return 0;
+
+  if (key_parms_from_sexp (s_key, &list, algoname, sizeof algoname, NULL, 0))
+    return 0; /* Error - assume it is not an DSA key.  */
+
+  if (!strcmp (algoname, "dsa"))
+    result = GCRY_PK_DSA;
+  else if (!strcmp (algoname, "ecc"))
+    {
+      if (is_eddsa (list))
+        result = 0;
+      else
+        result = GCRY_PK_ECDSA;
+    }
+  else if (!strcmp (algoname, "ecdsa"))
+    result = GCRY_PK_ECDSA;
+  else
+    result = 0;
+
+  gcry_sexp_release (list);
+  return result;
+}
+
+
+/* Return true if S_KEY is an EdDSA key as used with curve Ed25519.  */
+int
+agent_is_eddsa_key (gcry_sexp_t s_key)
+{
+  int result;
+  gcry_sexp_t list;
+  char algoname[6];
+
+  if (!s_key)
+    return 0;
+
+  if (key_parms_from_sexp (s_key, &list, algoname, sizeof algoname, NULL, 0))
+    return 0; /* Error - assume it is not an EdDSA key.  */
+
+  if (!strcmp (algoname, "ecc") && is_eddsa (list))
+    result = 1;
+  else if (!strcmp (algoname, "eddsa")) /* backward compatibility.  */
+    result = 1;
+  else
+    result = 0;
+
+  gcry_sexp_release (list);
+  return result;
+}
+
+
+/* Return the key for the keygrip GRIP.  The result is stored at
+   RESULT.  This function extracts the key from the private key
+   database and returns it as an S-expression object as it is.  On
+   failure an error code is returned and NULL stored at RESULT. */
+gpg_error_t
+agent_raw_key_from_file (ctrl_t ctrl, const unsigned char *grip,
+                         gcry_sexp_t *result)
+{
+  gpg_error_t err;
+  gcry_sexp_t s_skey;
+
+  (void)ctrl;
+
+  *result = NULL;
+
+  err = read_key_file (grip, &s_skey, NULL);
+  if (!err)
+    *result = s_skey;
+  return err;
+}
+
+
+gpg_error_t
+agent_keymeta_from_file (ctrl_t ctrl, const unsigned char *grip,
+                         nvc_t *r_keymeta)
+{
+  gpg_error_t err;
+  gcry_sexp_t s_skey;
+
+  (void)ctrl;
+
+  err = read_key_file (grip, &s_skey, r_keymeta);
+  gcry_sexp_release (s_skey);
+  return err;
+}
+
+
+/* Return the public key for the keygrip GRIP.  The result is stored
+   at RESULT.  This function extracts the public key from the private
+   key database.  On failure an error code is returned and NULL stored
+   at RESULT. */
+gpg_error_t
+agent_public_key_from_file (ctrl_t ctrl,
+                            const unsigned char *grip,
+                            gcry_sexp_t *result)
+{
+  gpg_error_t err;
+  int i, idx;
+  gcry_sexp_t s_skey;
+  const char *algoname, *elems;
+  int npkey;
+  gcry_mpi_t array[10];
+  gcry_sexp_t curve = NULL;
+  gcry_sexp_t flags = NULL;
+  gcry_sexp_t uri_sexp, comment_sexp;
+  const char *uri, *comment;
+  size_t uri_length, comment_length;
+  int uri_intlen, comment_intlen;
+  char *format, *p;
+  void *args[2+7+2+2+1]; /* Size is 2 + max. # of elements + 2 for uri + 2
+                            for comment + end-of-list.  */
+  int argidx;
+  gcry_sexp_t list = NULL;
+  const char *s;
+
+  (void)ctrl;
+
+  *result = NULL;
+
+  err = read_key_file (grip, &s_skey, NULL);
+  if (err)
+    return err;
+
+  for (i=0; i < DIM (array); i++)
+    array[i] = NULL;
+
+  err = extract_private_key (s_skey, 0, &algoname, &npkey, NULL, &elems,
+                             array, DIM (array), &curve, &flags);
+  if (err)
+    {
+      gcry_sexp_release (s_skey);
+      return err;
+    }
+
+  uri = NULL;
+  uri_length = 0;
+  uri_sexp = gcry_sexp_find_token (s_skey, "uri", 0);
+  if (uri_sexp)
+    uri = gcry_sexp_nth_data (uri_sexp, 1, &uri_length);
+
+  comment = NULL;
+  comment_length = 0;
+  comment_sexp = gcry_sexp_find_token (s_skey, "comment", 0);
+  if (comment_sexp)
+    comment = gcry_sexp_nth_data (comment_sexp, 1, &comment_length);
+
+  gcry_sexp_release (s_skey);
+  s_skey = NULL;
+
+
+  /* FIXME: The following thing is pretty ugly code; we should
+     investigate how to make it cleaner.  Probably code to handle
+     canonical S-expressions in a memory buffer is better suited for
+     such a task.  After all that is what we do in protect.c.  Need
+     to find common patterns and write a straightformward API to use
+     them.  */
+  assert (sizeof (size_t) <= sizeof (void*));
+
+  format = xtrymalloc (15+4+7*npkey+10+15+1+1);
+  if (!format)
+    {
+      err = gpg_error_from_syserror ();
+      for (i=0; array[i]; i++)
+        gcry_mpi_release (array[i]);
+      gcry_sexp_release (curve);
+      gcry_sexp_release (flags);
+      gcry_sexp_release (uri_sexp);
+      gcry_sexp_release (comment_sexp);
+      return err;
+    }
+
+  argidx = 0;
+  p = stpcpy (stpcpy (format, "(public-key("), algoname);
+  p = stpcpy (p, "%S%S");       /* curve name and flags.  */
+  args[argidx++] = &curve;
+  args[argidx++] = &flags;
+  for (idx=0, s=elems; idx < npkey; idx++)
+    {
+      *p++ = '(';
+      *p++ = *s++;
+      p = stpcpy (p, " %m)");
+      assert (argidx < DIM (args));
+      args[argidx++] = &array[idx];
+    }
+  *p++ = ')';
+  if (uri)
+    {
+      p = stpcpy (p, "(uri %b)");
+      assert (argidx+1 < DIM (args));
+      uri_intlen = (int)uri_length;
+      args[argidx++] = (void *)&uri_intlen;
+      args[argidx++] = (void *)&uri;
+    }
+  if (comment)
+    {
+      p = stpcpy (p, "(comment %b)");
+      assert (argidx+1 < DIM (args));
+      comment_intlen = (int)comment_length;
+      args[argidx++] = (void *)&comment_intlen;
+      args[argidx++] = (void*)&comment;
+    }
+  *p++ = ')';
+  *p = 0;
+  assert (argidx < DIM (args));
+  args[argidx] = NULL;
+
+  err = gcry_sexp_build_array (&list, NULL, format, args);
+  xfree (format);
+  for (i=0; array[i]; i++)
+    gcry_mpi_release (array[i]);
+  gcry_sexp_release (curve);
+  gcry_sexp_release (flags);
+  gcry_sexp_release (uri_sexp);
+  gcry_sexp_release (comment_sexp);
+
+  if (!err)
+    *result = list;
+  return err;
+}
+
+
+
+/* Check whether the secret key identified by GRIP is available.
+   Returns 0 is the key is available.  */
+int
+agent_key_available (const unsigned char *grip)
+{
+  int result;
+  char *fname;
+  char hexgrip[40+4+1];
+
+  bin2hex (grip, 20, hexgrip);
+  strcpy (hexgrip+40, ".key");
+
+  fname = make_filename (gnupg_homedir (), GNUPG_PRIVATE_KEYS_DIR,
+                         hexgrip, NULL);
+  result = !gnupg_access (fname, R_OK)? 0 : -1;
+  xfree (fname);
+  return result;
+}
+
+
+
+/* Return the information about the secret key specified by the binary
+   keygrip GRIP.  If the key is a shadowed one the shadow information
+   will be stored at the address R_SHADOW_INFO as an allocated
+   S-expression.  */
+gpg_error_t
+agent_key_info_from_file (ctrl_t ctrl, const unsigned char *grip,
+                          int *r_keytype, unsigned char **r_shadow_info)
+{
+  gpg_error_t err;
+  unsigned char *buf;
+  size_t len;
+  int keytype;
+
+  (void)ctrl;
+
+  if (r_keytype)
+    *r_keytype = PRIVATE_KEY_UNKNOWN;
+  if (r_shadow_info)
+    *r_shadow_info = NULL;
+
+  {
+    gcry_sexp_t sexp;
+
+    err = read_key_file (grip, &sexp, NULL);
+    if (err)
+      {
+        if (gpg_err_code (err) == GPG_ERR_ENOENT)
+          return gpg_error (GPG_ERR_NOT_FOUND);
+        else
+          return err;
+      }
+    err = make_canon_sexp (sexp, &buf, &len);
+    gcry_sexp_release (sexp);
+    if (err)
+      return err;
+  }
+
+  keytype = agent_private_key_type (buf);
+  switch (keytype)
+    {
+    case PRIVATE_KEY_CLEAR:
+    case PRIVATE_KEY_OPENPGP_NONE:
+      break;
+    case PRIVATE_KEY_PROTECTED:
+      /* If we ever require it we could retrieve the comment fields
+         from such a key. */
+      break;
+    case PRIVATE_KEY_SHADOWED:
+      if (r_shadow_info)
+        {
+          const unsigned char *s;
+          size_t n;
+
+          err = agent_get_shadow_info (buf, &s);
+          if (!err)
+            {
+              n = gcry_sexp_canon_len (s, 0, NULL, NULL);
+              assert (n);
+              *r_shadow_info = xtrymalloc (n);
+              if (!*r_shadow_info)
+                err = gpg_error_from_syserror ();
+              else
+                memcpy (*r_shadow_info, s, n);
+            }
+        }
+      break;
+    default:
+      err = gpg_error (GPG_ERR_BAD_SECKEY);
+      break;
+    }
+
+  if (!err && r_keytype)
+    *r_keytype = keytype;
+
+  xfree (buf);
+  return err;
+}
+
+
+
+/* Delete the key with GRIP from the disk after having asked for
+ * confirmation using DESC_TEXT.  If FORCE is set the function won't
+ * require a confirmation via Pinentry or warns if the key is also
+ * used by ssh.  If ONLY_STUBS is set only stub keys (references to
+ * smartcards) will be affected.
+ *
+ * Common error codes are:
+ *   GPG_ERR_NO_SECKEY
+ *   GPG_ERR_KEY_ON_CARD
+ *   GPG_ERR_NOT_CONFIRMED
+ *   GPG_ERR_FORBIDDEN     - Not a stub key and ONLY_STUBS requested.
+ */
+gpg_error_t
+agent_delete_key (ctrl_t ctrl, const char *desc_text,
+                  const unsigned char *grip, int force, int only_stubs)
+{
+  gpg_error_t err;
+  gcry_sexp_t s_skey = NULL;
+  unsigned char *buf = NULL;
+  size_t len;
+  char *desc_text_final = NULL;
+  char *comment = NULL;
+  ssh_control_file_t cf = NULL;
+  char hexgrip[40+4+1];
+  char *default_desc = NULL;
+  int key_type;
+
+  err = read_key_file (grip, &s_skey, NULL);
+  if (gpg_err_code (err) == GPG_ERR_ENOENT)
+    err = gpg_error (GPG_ERR_NO_SECKEY);
+  if (err)
+    goto leave;
+
+  err = make_canon_sexp (s_skey, &buf, &len);
+  if (err)
+    goto leave;
+
+  key_type = agent_private_key_type (buf);
+  if (only_stubs && key_type != PRIVATE_KEY_SHADOWED)
+    {
+      err  = gpg_error (GPG_ERR_FORBIDDEN);
+      goto leave;
+    }
+
+  switch (key_type)
+    {
+    case PRIVATE_KEY_CLEAR:
+    case PRIVATE_KEY_OPENPGP_NONE:
+    case PRIVATE_KEY_PROTECTED:
+      bin2hex (grip, 20, hexgrip);
+      if (!force)
+        {
+          if (!desc_text)
+            {
+              default_desc = xtryasprintf
+          (L_("Do you really want to delete the key identified by keygrip%%0A"
+              "  %s%%0A  %%C%%0A?"), hexgrip);
+              desc_text = default_desc;
+            }
+
+          /* Note, that we will take the comment as a C string for
+             display purposes; i.e. all stuff beyond a Nul character is
+             ignored.  */
+          {
+            gcry_sexp_t comment_sexp;
+
+            comment_sexp = gcry_sexp_find_token (s_skey, "comment", 0);
+            if (comment_sexp)
+              comment = gcry_sexp_nth_string (comment_sexp, 1);
+            gcry_sexp_release (comment_sexp);
+          }
+
+          if (desc_text)
+            err = agent_modify_description (desc_text, comment, s_skey,
+                                            &desc_text_final);
+          if (err)
+            goto leave;
+
+          err = agent_get_confirmation (ctrl, desc_text_final,
+                                        L_("Delete key"), L_("No"), 0);
+          if (err)
+            goto leave;
+
+          cf = ssh_open_control_file ();
+          if (cf)
+            {
+              if (!ssh_search_control_file (cf, hexgrip, NULL, NULL, NULL))
+                {
+                  err = agent_get_confirmation
+                    (ctrl,
+                     L_("Warning: This key is also listed for use with SSH!\n"
+                        "Deleting the key might remove your ability to "
+                        "access remote machines."),
+                     L_("Delete key"), L_("No"), 0);
+                  if (err)
+                    goto leave;
+                }
+            }
+        }
+      err = remove_key_file (grip);
+      break;
+
+    case PRIVATE_KEY_SHADOWED:
+      err = remove_key_file (grip);
+      break;
+
+    default:
+      log_error ("invalid private key format\n");
+      err = gpg_error (GPG_ERR_BAD_SECKEY);
+      break;
+    }
+
+ leave:
+  ssh_close_control_file (cf);
+  gcry_free (comment);
+  xfree (desc_text_final);
+  xfree (default_desc);
+  xfree (buf);
+  gcry_sexp_release (s_skey);
+  return err;
+}
+
+
+/* Write an S-expression formatted shadow key to our key storage.
+   Shadow key is created by an S-expression public key in PKBUF and
+   card's SERIALNO and the IDSTRING.  With FORCE passed as true an
+   existing key with the given GRIP will get overwritten. If
+   DISPSERIALNO is not NULL the human readable s/n will also be
+   recorded in the key file.  If MAYBE_UPDATE is set it is assumed that
+   the shadow key already exists and we test whether we should update
+   it (FORCE is ignored in this case).  */
+gpg_error_t
+agent_write_shadow_key (int maybe_update, const unsigned char *grip,
+                        const char *serialno, const char *keyid,
+                        const unsigned char *pkbuf, int force,
+                        const char *dispserialno)
+{
+  gpg_error_t err;
+  unsigned char *shadow_info;
+  unsigned char *shdkey;
+  size_t len;
+  char *fname = NULL;
+  estream_t fp = NULL;
+  char first;
+
+  if (maybe_update && !opt.enable_extended_key_format)
+    return 0;  /* Silently ignore.  */
+
+  /* Just in case some caller did not parse the stuff correctly, skip
+   * leading spaces.  */
+  while (spacep (serialno))
+    serialno++;
+  while (spacep (keyid))
+    keyid++;
+
+  shadow_info = make_shadow_info (serialno, keyid);
+  if (!shadow_info)
+    return gpg_error_from_syserror ();
+
+  err = agent_shadow_key (pkbuf, shadow_info, &shdkey);
+  xfree (shadow_info);
+  if (err)
+    {
+      log_error ("shadowing the key failed: %s\n", gpg_strerror (err));
+      return err;
+    }
+
+  len = gcry_sexp_canon_len (shdkey, 0, NULL, NULL);
+
+  if (maybe_update)  /* Update mode.  */
+    {
+      fname = fname_from_keygrip (grip);
+      if (!fname)
+        {
+          err = gpg_error_from_syserror ();
+          goto leave;
+        }
+
+      fp = es_fopen (fname, "rb+,mode=-rw");
+      if (!fp)
+        {
+          err = gpg_error_from_syserror ();
+          log_error ("shadow key file '%s' disappeared\n", fname);
+          goto leave;
+        }
+
+      /* See if an existing key is in extended format.  */
+      if (es_fread (&first, 1, 1, fp) != 1)
+        {
+          err = gpg_error_from_syserror ();
+          log_error ("error reading first byte from '%s': %s\n",
+                     fname, gpg_strerror (err));
+          goto leave;
+        }
+
+      if (es_fseek (fp, 0, SEEK_SET))
+        {
+          err = gpg_error_from_syserror ();
+          log_error ("error seeking in '%s': %s\n", fname, gpg_strerror (err));
+          goto leave;
+        }
+
+      /* "(first == '(')" indicates that the key is in the old format.  */
+      err = write_extended_private_key (maybe_update,
+                                        fname, fp, (first == '('), 0,
+                                        shdkey, len,
+                                        0, serialno, keyid,
+                                        dispserialno);
+      fname = NULL;  /* Ownership was transferred.  */
+      fp = NULL;     /* Ditto.  */
+    }
+  else  /* Standard mode */
+    {
+      err = agent_write_private_key (grip, shdkey, len, force, 0,
+                                     serialno, keyid, dispserialno);
+    }
+
+ leave:
+  xfree (fname);
+  es_fclose (fp);
+  xfree (shdkey);
+  if (err)
+    log_error ("error %s key: %s\n", maybe_update? "updating":"writing",
+               gpg_strerror (err));
+
+  return err;
+}