gnupg/agent/divert-scd.c

/* divert-scd.c - divert operations to the scdaemon 
 *	Copyright (C) 2002 Free Software Foundation, Inc.
 *
 * This file is part of GnuPG.
 *
 * GnuPG is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * GnuPG is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
 */

#include <config.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <assert.h>
#include <unistd.h>
#include <sys/stat.h>

#include "agent.h"
#include "sexp-parse.h"



static int
ask_for_card (const unsigned char *shadow_info, char **r_kid)
{
  int rc, i;
  const unsigned char *s;
  size_t n;
  char *serialno;
  int no_card = 0;
  char *desc;
  char *want_sn, *want_kid;

  *r_kid = NULL;
  s = shadow_info;
  if (*s != '(')
    return GNUPG_Invalid_Sexp;
  s++;
  n = snext (&s);
  if (!n)
    return GNUPG_Invalid_Sexp;
  want_sn = xtrymalloc (n*2+1);
  if (!want_sn)
    return GNUPG_Out_Of_Core;
  for (i=0; i < n; i++)
    sprintf (want_sn+2*i, "%02X", s[i]);
  s += n;

  n = snext (&s);
  if (!n)
    return GNUPG_Invalid_Sexp;
  want_kid = xtrymalloc (n+1);
  if (!want_kid)
    {
      xfree (want_sn);
      return GNUPG_Out_Of_Core;
    }
  memcpy (want_kid, s, n);
  want_kid[n] = 0;

  for (;;)
    {
      rc = agent_card_serialno (&serialno);
      if (!rc)
        {
          log_debug ("detected card with S/N %s\n", serialno);
          i = strcmp (serialno, want_sn);
          xfree (serialno);
          serialno = NULL;
          if (!i)
            {
              xfree (want_sn);
              *r_kid = want_kid;
              return 0; /* yes, we have the correct card */
            }
        }
      else if (rc == GNUPG_Card_Not_Present)
        {
          log_debug ("no card present\n");
          rc = 0;
          no_card = 1;
        }
      else
        {
          log_error ("error accesing card: %s\n", gnupg_strerror (rc));
        }

      if (!rc)
        {
          if (asprintf (&desc,
                    "%s:%%0A%%0A"
                    "  \"%s\"",
                    no_card? "Please insert the card with serial number" 
                    : "Please remove the current card and "
                    "insert the one with serial number",
                    want_sn) < 0)
            {
              rc = GNUPG_Out_Of_Core;
            }
          else
            {
              rc = agent_get_confirmation (desc, NULL);
              free (desc);
            }
        }
      if (rc)
        {
          xfree (want_sn);
          xfree (want_kid);
          return rc;
        }
    }
}


/* fixme: this should be moved to libgcrypt and only be used if the
   smartcard does not support pkcs-1 itself */
static int
encode_md_for_card (const unsigned char *digest, size_t digestlen, int algo,
                    unsigned int nbits, unsigned char **r_val, size_t *r_len)
{
  int nframe = (nbits+7) / 8;
  byte *frame;
  int i, n;
  byte asn[100];
  size_t asnlen;

  asnlen = DIM(asn);
  if (gcry_md_algo_info (algo, GCRYCTL_GET_ASNOID, asn, &asnlen))
    {
      log_error ("no object identifier for algo %d\n", algo);
      return GNUPG_Internal_Error;
    }

  if (digestlen + asnlen + 4  > nframe )
    {
      log_error ("can't encode a %d bit MD into a %d bits frame\n",
                 (int)(digestlen*8), (int)nbits);
      return GNUPG_Internal_Error;
    }
  
  /* We encode the MD in this way:
   *
   *	   0  1 PAD(n bytes)   0  ASN(asnlen bytes)  MD(len bytes)
   *
   * PAD consists of FF bytes.
   */
  frame = xtrymalloc (nframe);
  if (!frame)
    return GNUPG_Out_Of_Core;
  n = 0;
  frame[n++] = 0;
  frame[n++] = 1; /* block type */
  i = nframe - digestlen - asnlen -3 ;
  assert ( i > 1 );
  memset ( frame+n, 0xff, i ); n += i;
  frame[n++] = 0;
  memcpy ( frame+n, asn, asnlen ); n += asnlen;
  memcpy ( frame+n, digest, digestlen ); n += digestlen;
  assert ( n == nframe );
  if (DBG_CRYPTO)
    log_printhex ("encoded hash:", frame, nframe);
      
  *r_val = frame;
  *r_len = nframe;
  return 0;
}


/* Callback used to ask for the PIN which should be set into BUF.  The
   buf has been allocated by the caller and is of size MAXBUF which
   includes the terminating null.  The function should return an UTF-8
   string with the passphrase, the buffer may optioanlly be padded
   with arbitrary characters */
static int 
getpin_cb (void *opaque, const char *info, char *buf, size_t maxbuf)
{
  struct pin_entry_info_s *pi;
  int rc;
  int tries = 0;
  const char *errtext;
  
  assert (!opaque);

  if (maxbuf < 2)
    return GNUPG_Invalid_Value;

  /* FIXME: keep PI and TRIES in OPAQUE */
  pi = gcry_calloc_secure (1, sizeof (*pi) + 100);
  pi->max_length = maxbuf-1;
  pi->min_digits = 0;  /* we want a real passphrase */
  pi->max_digits = 8;
  pi->max_tries = 3;

  errtext = NULL;
  do
    {
      rc = agent_askpin (info, errtext, pi);
      if (!rc)
        {
          strncpy (buf, pi->pin, maxbuf-1);
          buf[maxbuf-1] = 0;
          xfree (pi);
          return 0;
        }
      errtext = pi->min_digits? trans ("Bad PIN") : trans ("Bad Passphrase");
    }
  while ((rc == GNUPG_Bad_Passphrase || rc == GNUPG_Bad_PIN)
         && tries++ < 3);
  xfree (pi);
  return rc;
}




int
divert_pksign (const unsigned char *digest, size_t digestlen, int algo,
               const unsigned char *shadow_info, unsigned char **r_sig)
{
  int rc;
  char *kid;
  size_t siglen;
  char *sigval;
  unsigned char *data;
  size_t ndata;

  rc = ask_for_card (shadow_info, &kid);
  if (rc)
    return rc;

  rc = encode_md_for_card (digest, digestlen, algo, 1024 /* fixme*/,
                           &data, &ndata);
  if (rc)
    return rc;

  rc = agent_card_pksign (kid, getpin_cb, NULL,
                          data, ndata, &sigval, &siglen);
  if (!rc)
    *r_sig = sigval;
  xfree (data);
  xfree (kid);
  
  return rc;
}


/* Decrypt the the value given asn an S-expression in CIPHER using the
   key identified by SHADOW_INFO and return the plaintext in an
   allocated buffer in R_BUF.  */
int  
divert_pkdecrypt (const unsigned char *cipher,
                  const unsigned char *shadow_info,
                  char **r_buf, size_t *r_len)
{
  int rc;
  char *kid;
  const unsigned char *s;
  size_t n;
  const unsigned char *ciphertext;
  size_t ciphertextlen;
  char *plaintext;
  size_t plaintextlen;

  s = cipher;
  if (*s != '(')
    return GNUPG_Invalid_Sexp;
  s++;
  n = snext (&s);
  if (!n)
    return GNUPG_Invalid_Sexp; 
  if (!smatch (&s, n, "enc-val"))
    return GNUPG_Unknown_Sexp; 
  if (*s != '(')
    return GNUPG_Unknown_Sexp;
  s++;
  n = snext (&s);
  if (!n)
    return GNUPG_Invalid_Sexp; 
  if (!smatch (&s, n, "rsa"))
    return GNUPG_Unsupported_Algorithm; 
  if (*s != '(')
    return GNUPG_Unknown_Sexp;
  s++;
  n = snext (&s);
  if (!n)
    return GNUPG_Invalid_Sexp; 
  if (!smatch (&s, n, "a"))
    return GNUPG_Unknown_Sexp;
  n = snext (&s);
  if (!n)
    return GNUPG_Unknown_Sexp; 
  ciphertext = s;
  ciphertextlen = n;

  rc = ask_for_card (shadow_info, &kid);
  if (rc)
    return rc;

  rc = agent_card_pkdecrypt (kid, getpin_cb, NULL,
                             ciphertext, ciphertextlen,
                             &plaintext, &plaintextlen);
  if (!rc)
    {
      *r_buf = plaintext;
      *r_len = plaintextlen;
    }
  xfree (kid);
  return rc;
}