path: root/sm/certcheck.c

/* certcheck.c - check one certificate
 *	Copyright (C) 2001 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 <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <unistd.h> 
#include <time.h>
#include <assert.h>

#include <gcrypt.h>
#include <ksba.h>

#include "gpgsm.h"
#include "keydb.h"
#include "i18n.h"


static int
do_encode_md (GCRY_MD_HD md, int algo,  unsigned int nbits,
              GCRY_MPI *r_val)
{
  int nframe = (nbits+7) / 8;
  byte *frame;
  int i, n;
  byte asn[100];
  size_t asnlen;
  size_t len;

  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;
    }

  len = gcry_md_get_algo_dlen (algo);
  
  if ( len + asnlen + 4  > nframe )
    {
      log_error ("can't encode a %d bit MD into a %d bits frame\n",
                 (int)(len*8), (int)nbits);
      return GNUPG_Internal_Error;
    }
  
  /* We encode the MD in this way:
   *
   *	   0  A 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 - len - 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, gcry_md_read(md, algo), len ); n += len;
  assert ( n == nframe );
  if (DBG_X509)
    {
      int j;
      log_debug ("encoded hash:");
      for (j=0; j < nframe; j++)
        log_printf (" %02X", frame[j]);
      log_printf ("\n");
    }
      
  gcry_mpi_scan (r_val, GCRYMPI_FMT_USG, frame, &nframe);
  xfree (frame);
  return 0;
}


/*
  Check the signature on CERT using the ISSUER-CERT.  This function
  does only test the cryptographic signature and nothing else.  It is
  assumed that the ISSUER_CERT is valid. */
int
gpgsm_check_cert_sig (KsbaCert issuer_cert, KsbaCert cert)
{
  const char *algoid;
  GCRY_MD_HD md;
  int rc, algo;
  GCRY_MPI frame;
  char *p;
  GCRY_SEXP s_sig, s_hash, s_pkey;

  algo = gcry_md_map_name ( (algoid=ksba_cert_get_digest_algo (cert)));
  if (!algo)
    {
      log_error ("unknown hash algorithm `%s'\n", algoid? algoid:"?");
      return GNUPG_General_Error;
    }
  md = gcry_md_open (algo, 0);
  if (!md)
    {
      log_error ("md_open failed: %s\n", gcry_strerror (-1));
      return GNUPG_General_Error;
    }

  rc = ksba_cert_hash (cert, 1, HASH_FNC, md);
  if (rc)
    {
      log_error ("ksba_cert_hash failed: %s\n", ksba_strerror (rc));
      gcry_md_close (md);
      return map_ksba_err (rc);
    }
  gcry_md_final (md);

  p = ksba_cert_get_sig_val (cert); /* fixme: check p*/
  if (DBG_X509)
    log_debug ("signature: %s\n", p);

  rc = gcry_sexp_sscan ( &s_sig, NULL, p, strlen(p));
  if (rc)
    {
      log_error ("gcry_sexp_scan failed: %s\n", gcry_strerror (rc));
      return map_gcry_err (rc);
    }

  p = ksba_cert_get_public_key (issuer_cert);
  if (DBG_X509)
    log_debug ("issuer public key: %s\n", p);

  rc = gcry_sexp_sscan ( &s_pkey, NULL, p, strlen(p));
  if (rc)
    {
      log_error ("gcry_sexp_scan failed: %s\n", gcry_strerror (rc));
      return map_gcry_err (rc);
    }

  rc = do_encode_md (md, algo, gcry_pk_get_nbits (s_pkey), &frame);
  if (rc)
    {
      /* fixme: clean up some things */
      return rc;
    }
  /* put hash into the S-Exp s_hash */
  if ( gcry_sexp_build (&s_hash, NULL, "%m", frame) )
    BUG ();

  
  rc = gcry_pk_verify (s_sig, s_hash, s_pkey);
  if (DBG_CRYPTO)
      log_debug ("gcry_pk_verify: %s\n", gcry_strerror (rc));
  return map_gcry_err (rc);
}



int
gpgsm_check_cms_signature (KsbaCert cert, const char *sigval,
                           GCRY_MD_HD md, int algo)
{
  int rc;
  char *p;
  GCRY_MPI frame;
  GCRY_SEXP s_sig, s_hash, s_pkey;

  rc = gcry_sexp_sscan (&s_sig, NULL, sigval, strlen(sigval));
  if (rc)
    {
      log_error ("gcry_sexp_scan failed: %s\n", gcry_strerror (rc));
      return map_gcry_err (rc);
    }

  if (getenv ("GPGSM_FAKE_KEY"))
    {
      const char n[] = "#8732A669BB7C5057AD070EFA54E035C86DF474F7A7EBE2435"
        "3DADEB86FFE74C32AEEF9E5C6BD7584CB572520167B3E8C89A1FA75C74FF9E938"
        "2710F3B270B638EB96E7486491D81C53CA8A50B4E840B1C7458A4A1E52EC18D681"
        "8A2805C9165827F77EF90D55014E4B2AF9386AE8F6462F46A547CB593ABD509311"
        "4D3D16375F#";
      const char e[] = "#11#";
      char *tmp;

      log_debug ("Using HARDWIRED public key\n");
      asprintf (&tmp, "(public-key(rsa(n %s)(e %s)))", n, e);
      /* asprintf does not use our allocation fucntions, so we can't
         use our free */
      p = xstrdup (tmp);
      free (tmp);
    }
  else
    {
      p = ksba_cert_get_public_key (cert);
    }

  if (DBG_X509)
    log_debug ("public key: %s\n", p);
  rc = gcry_sexp_sscan ( &s_pkey, NULL, p, strlen(p));
  if (rc)
    {
      log_error ("gcry_sexp_scan failed: %s\n", gcry_strerror (rc));
      return map_gcry_err (rc);
    }


  rc = do_encode_md (md, algo, gcry_pk_get_nbits (s_pkey), &frame);
  if (rc)
    {
      /* fixme: clean up some things */
      return rc;
    }
  /* put hash into the S-Exp s_hash */
  if ( gcry_sexp_build (&s_hash, NULL, "%m", frame) )
    BUG ();

  
  rc = gcry_pk_verify (s_sig, s_hash, s_pkey);
  if (DBG_CRYPTO)
      log_debug ("gcry_pk_verify: %s\n", gcry_strerror (rc));
  return map_gcry_err (rc);
}



int
gpgsm_create_cms_signature (KsbaCert cert, GCRY_MD_HD md, int mdalgo,
                            char **r_sigval)
{
#if 0

  /* our sample key */
  const char n[] = "#8732A669BB7C5057AD070EFA54E035C86DF474F7A7EBE2435"
    "3DADEB86FFE74C32AEEF9E5C6BD7584CB572520167B3E8C89A1FA75C74FF9E938"
    "2710F3B270B638EB96E7486491D81C53CA8A50B4E840B1C7458A4A1E52EC18D681"
    "8A2805C9165827F77EF90D55014E4B2AF9386AE8F6462F46A547CB593ABD509311"
    "4D3D16375F#";
  const char e[] = "#11#";
  const char d[] = "#07F3EBABDDDA22D7FB1E8869140D30571586D9B4370DE02213F"
    "DD0DDAC3C24FC6BEFF0950BB0CAAD755F7AA788DA12BCF90987341AC8781CC7115"
    "B59A115B05D9D99B3D7AF77854DC2EE6A36154512CC0EAD832601038A88E837112"
    "AB2A39FD9FBE05E30D6FFA6F43D71C59F423CA43BC91C254A8C89673AB61F326B0"
    "762FBC9#";
  const char p[] = "#B2ABAD4328E66303E206C53CFBED17F18F712B1C47C966EE13DD"
    "AA9AD3616A610ADF513F8376FA48BAE12FED64CECC1E73091A77B45119AF0FC1286A"
    "85BD9BBD#";
  const char q[] = "#C1B648B294BB9AEE7FEEB77C4F64E9333E4EA9A7C54D521356FB"
    "BBB7558A0E7D6331EC7B42E3F0CD7BBBA9B7A013422F615F10DCC1E8462828BF8FC7"
    "39C5E34B#";
  const char  u[] = "#A9B5EFF9C80A4A356B9A95EB63E381B262071E5CE9C1F32FF03"
    "83AD8289BED8BC690555E54411FA2FDB9B49638A21B2046C325F5633B4B1ECABEBFD"
    "1B3519072#";

  GCRY_SEXP s_skey, s_hash, s_sig;
  GCRY_MPI frame;
  int rc;
  char *buf;
  size_t len;

  /* create a secret key as an sexp */
  log_debug ("Using HARDWIRED secret key\n");
  asprintf (&buf, "(private-key(oid.1.2.840.113549.1.1.1"
           "(n %s)(e %s)(d %s)(p %s)(q %s)(u %s)))",
           n, e, d, p, q, u);
  /* asprintf does not use our allocation fucntions, so we can't
     use our free */
  rc = gcry_sexp_sscan (&s_skey, NULL, buf, strlen(buf));
  free (buf);
  if (rc)
    {
      log_error ("failed to build S-Exp: %s\n", gcry_strerror (rc));
      return map_gcry_err (rc);
    }
  
  /* put the hash into a sexp */
  rc = do_encode_md (md, mdalgo, gcry_pk_get_nbits (s_skey), &frame);
  if (rc)
    {
      /* fixme: clean up some things */
      return rc;
    }
  if ( gcry_sexp_build (&s_hash, NULL, "%m", frame) )
    BUG ();


  /* sign */
  rc = gcry_pk_sign (&s_sig, s_hash, s_skey);
  if (rc)
    {
      log_error ("signing failed: %s\n", gcry_strerror (rc));
      return map_gcry_err (rc);
    }

  len = gcry_sexp_sprint (s_sig, GCRYSEXP_FMT_CANON, NULL, 0);
  assert (len);
  buf = xmalloc (len);
  len = gcry_sexp_sprint (s_sig, GCRYSEXP_FMT_CANON, buf, len);
  assert (len);

  *r_sigval = buf;
#else
  int rc;
  char *grip;
  size_t siglen;

  grip = gpgsm_get_keygrip_hexstring (cert);
  if (!grip)
    return seterr (Bad_Certificate);

  rc = gpgsm_agent_pksign (grip, gcry_md_read(md, mdalgo), 
                           gcry_md_get_algo_dlen (mdalgo), mdalgo,
                           r_sigval, &siglen);
  xfree (grip);
  /* FIXME: we should check that the returnes S-Exp is valid fits int
     siglen.  It ould probaly be a good idea to scan and print it
     again to make this sure and be sure that we have canocical
     encoding */

#endif
  return rc;
}