gnupg/sm/verify.c

/* verify.c - Verify a messages signature
 *	Copyright (C) 2001, 2002, 2003 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 "gpgsm.h"
#include <gcrypt.h>
#include <ksba.h>

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

static char *
strtimestamp_r (ksba_isotime_t atime)
{
  char *buffer = xmalloc (15);
  
  if (!atime || !*atime)
    strcpy (buffer, "none");
  else
    sprintf (buffer, "%.4s-%.2s-%.2s", atime, atime+4, atime+6);
  return buffer;
}



/* Hash the data for a detached signature */
static void
hash_data (int fd, gcry_md_hd_t md)
{
  FILE *fp;
  char buffer[4096];
  int nread;

  fp = fdopen ( dup (fd), "rb");
  if (!fp)
    {
      log_error ("fdopen(%d) failed: %s\n", fd, strerror (errno));
      return;
    }

  do 
    {
      nread = fread (buffer, 1, DIM(buffer), fp);
      gcry_md_write (md, buffer, nread);
    }
  while (nread);
  if (ferror (fp))
      log_error ("read error on fd %d: %s\n", fd, strerror (errno));
  fclose (fp);
}




/* Perform a verify operation.  To verify detached signatures, data_fd
   must be different than -1.  With OUT_FP given and a non-detached
   signature, the signed material is written to that stream. */
int
gpgsm_verify (CTRL ctrl, int in_fd, int data_fd, FILE *out_fp)
{
  int i, rc;
  Base64Context b64reader = NULL;
  Base64Context b64writer = NULL;
  KsbaError err;
  KsbaReader reader;
  KsbaWriter writer = NULL;
  KsbaCMS cms = NULL;
  KsbaStopReason stopreason;
  KsbaCert cert;
  KEYDB_HANDLE kh;
  gcry_md_hd_t data_md = NULL;
  int signer;
  const char *algoid;
  int algo;
  int is_detached;
  FILE *fp = NULL;
  char *p;

  kh = keydb_new (0);
  if (!kh)
    {
      log_error (_("failed to allocated keyDB handle\n"));
      rc = gpg_error (GPG_ERR_GENERAL);
      goto leave;
    }


  fp = fdopen ( dup (in_fd), "rb");
  if (!fp)
    {
      rc = gpg_error (gpg_err_code_from_errno (errno));
      log_error ("fdopen() failed: %s\n", strerror (errno));
      goto leave;
    }

  rc = gpgsm_create_reader (&b64reader, ctrl, fp, &reader);
  if (rc)
    {
      log_error ("can't create reader: %s\n", gpg_strerror (rc));
      goto leave;
    }

  if (out_fp)
    {
      rc = gpgsm_create_writer (&b64writer, ctrl, out_fp, &writer);
      if (rc)
        {
          log_error ("can't create writer: %s\n", gpg_strerror (rc));
          goto leave;
        }
    }

  err = ksba_cms_new (&cms);
  if (err)
    {
      rc = gpg_error (GPG_ERR_ENOMEM);
      goto leave;
    }

  err = ksba_cms_set_reader_writer (cms, reader, writer);
  if (err)
    {
      log_error ("ksba_cms_set_reader_writer failed: %s\n",
                 gpg_strerror (err));
      rc = err;
      goto leave;
    }

  rc = gcry_md_open (&data_md, 0, 0);
  if (rc)
    {
      log_error ("md_open failed: %s\n", gpg_strerror (rc));
      goto leave;
    }
  if (DBG_HASHING)
    gcry_md_start_debug (data_md, "vrfy.data");

  is_detached = 0;
  do 
    {
      err = ksba_cms_parse (cms, &stopreason);
      if (err)
        {
          log_error ("ksba_cms_parse failed: %s\n", gpg_strerror (err));
          rc = err;
          goto leave;
        }

      if (stopreason == KSBA_SR_NEED_HASH)
        {
          is_detached = 1;
          if (opt.verbose)
            log_info ("detached signature\n");
        }

      if (stopreason == KSBA_SR_NEED_HASH
          || stopreason == KSBA_SR_BEGIN_DATA)
        { /* We are now able to enable the hash algorithms */
          for (i=0; (algoid=ksba_cms_get_digest_algo_list (cms, i)); i++)
            {
              algo = gcry_md_map_name (algoid);
              if (!algo)
                log_error ("unknown hash algorithm `%s'\n",
                           algoid? algoid:"?");
              else
                gcry_md_enable (data_md, algo);
            }
          if (is_detached)
            {
              if (data_fd == -1)
                log_info ("detached signature w/o data "
                          "- assuming certs-only\n");
              else
                hash_data (data_fd, data_md);  
            }
          else
            {
              ksba_cms_set_hash_function (cms, HASH_FNC, data_md);
            }
        }
      else if (stopreason == KSBA_SR_END_DATA)
        { /* The data bas been hashed */

        }
    }
  while (stopreason != KSBA_SR_READY);   

  if (b64writer)
    {
      rc = gpgsm_finish_writer (b64writer);
      if (rc) 
        {
          log_error ("write failed: %s\n", gpg_strerror (rc));
          goto leave;
        }
    }

  if (data_fd != -1 && !is_detached)
    {
      log_error ("data given for a non-detached signature\n");
      rc = gpg_error (GPG_ERR_CONFLICT);
      goto leave;
    }

  for (i=0; (cert=ksba_cms_get_cert (cms, i)); i++)
    {
      /* Fixme: it might be better to check the validity of the
         certificate first before entering it into the DB.  This way
         we would avoid cluttering the DB with invalid
         certificates. */
      keydb_store_cert (cert, 0, NULL);
      ksba_cert_release (cert);
    }

  cert = NULL;
  err = 0;
  for (signer=0; ; signer++)
    {
      char *issuer = NULL;
      KsbaSexp sigval = NULL;
      ksba_isotime_t sigtime, keyexptime;
      KsbaSexp serial;
      char *msgdigest = NULL;
      size_t msgdigestlen;
      char *ctattr;

      err = ksba_cms_get_issuer_serial (cms, signer, &issuer, &serial);
      if (!signer && gpg_err_code (err) == GPG_ERR_NO_DATA
          && data_fd == -1 && is_detached)
        {
          log_info ("certs-only message accepted\n");
          err = 0;
          break;
        }
      if (err)
        {
          if (signer && err == -1)
            err = 0;
          break;
        }
      if (DBG_X509)
        {
          log_debug ("signer %d - issuer: `%s'\n",
                     signer, issuer? issuer:"[NONE]");
          log_debug ("signer %d - serial: ", signer);
          gpgsm_dump_serial (serial);
          log_printf ("\n");
        }

      err = ksba_cms_get_signing_time (cms, signer, sigtime);
      if (gpg_err_code (err) == GPG_ERR_NO_DATA)
        *sigtime = 0;
      else if (err)
        {
          log_error ("error getting signing time: %s\n", gpg_strerror (err));
          *sigtime = 0; /* FIXME: we can't encode an error in the time
                           string. */
        }

      err = ksba_cms_get_message_digest (cms, signer,
                                         &msgdigest, &msgdigestlen);
      if (!err)
        {
          algoid = ksba_cms_get_digest_algo (cms, signer);
          algo = gcry_md_map_name (algoid);
          if (DBG_X509)
            log_debug ("signer %d - digest algo: %d\n", signer, algo);
          if ( !gcry_md_info (data_md, GCRYCTL_IS_ALGO_ENABLED, &algo, NULL) )
            {
              log_error ("digest algo %d has not been enabled\n", algo);
              goto next_signer;
            }
        }
      else if (gpg_err_code (err) == GPG_ERR_NO_DATA)
        {
          assert (!msgdigest);
          err = 0;
          algoid = NULL;
          algo = 0; 
        }
      else /* real error */
        break;

      err = ksba_cms_get_sigattr_oids (cms, signer,
                                       "1.2.840.113549.1.9.3",&ctattr);
      if (!err) 
        {
          const char *s;

          if (DBG_X509)
            log_debug ("signer %d - content-type attribute: %s", signer, ctattr);
          s = ksba_cms_get_content_oid (cms, 1);
          if (!s || strcmp (ctattr, s))
            {
              log_error ("content-type attribute does not match "
                         "actual content-type\n");
              ksba_free (ctattr);
              ctattr = NULL;
              goto next_signer;
            }
          ksba_free (ctattr);
          ctattr = NULL;
        }
      else if (err != -1)
        {
          log_error ("error getting content-type attribute: %s\n",
                     gpg_strerror (err));
          goto next_signer;
        }
      err = 0;


      sigval = ksba_cms_get_sig_val (cms, signer);
      if (!sigval)
        {
          log_error ("no signature value available\n");
          goto next_signer;
        }
      if (DBG_X509)
        log_debug ("signer %d - signature available", signer);

      /* Find the certificate of the signer */
      keydb_search_reset (kh);
      rc = keydb_search_issuer_sn (kh, issuer, serial);
      if (rc)
        {
          if (rc == -1)
            {
              log_error ("certificate not found\n");
              rc = gpg_error (GPG_ERR_NO_PUBKEY);
            }
          else
            log_error ("failed to find the certificate: %s\n",
                       gpg_strerror(rc));
          {
            char numbuf[50];
            sprintf (numbuf, "%d", rc);

            gpgsm_status2 (ctrl, STATUS_ERROR, "verify.findkey",
                           numbuf, NULL);
          }
          /* fixme: we might want to append the issuer and serial
             using our standard notation */
          goto next_signer;
        }

      rc = keydb_get_cert (kh, &cert);
      if (rc)
        {
          log_error ("failed to get cert: %s\n", gpg_strerror (rc));
          goto next_signer;
        }

      log_info (_("Signature made "));
      if (*sigtime)
        gpgsm_dump_time (sigtime);
      else
        log_printf (_("[date not given]"));
      log_printf (_(" using certificate ID %08lX\n"),
                  gpgsm_get_short_fingerprint (cert));


      if (msgdigest)
        { /* Signed attributes are available. */
          gcry_md_hd_t md;
          unsigned char *s;

          /* check that the message digest in the signed attributes
             matches the one we calculated on the data */
          s = gcry_md_read (data_md, algo);
          if ( !s || !msgdigestlen
               || gcry_md_get_algo_dlen (algo) != msgdigestlen
               || !s || memcmp (s, msgdigest, msgdigestlen) )
            {
              char *fpr;

              log_error ("invalid signature: message digest attribute "
                         "does not match calculated one\n");
              fpr = gpgsm_get_fingerprint_hexstring (cert, GCRY_MD_SHA1);
              gpgsm_status (ctrl, STATUS_BADSIG, fpr);
              xfree (fpr);
              goto next_signer; 
            }
            
          rc = gcry_md_open (&md, algo, 0);
          if (rc)
            {
              log_error ("md_open failed: %s\n", gpg_strerror (rc));
              goto next_signer;
            }
          if (DBG_HASHING)
            gcry_md_start_debug (md, "vrfy.attr");

          ksba_cms_set_hash_function (cms, HASH_FNC, md);
          rc = ksba_cms_hash_signed_attrs (cms, signer);
          if (rc)
            {
              log_error ("hashing signed attrs failed: %s\n",
                         gpg_strerror (rc));
              gcry_md_close (md);
              goto next_signer;
            }
          rc = gpgsm_check_cms_signature (cert, sigval, md, algo);
          gcry_md_close (md);
        }
      else
        {
          rc = gpgsm_check_cms_signature (cert, sigval, data_md, algo);
        }

      if (rc)
        {
          char *fpr;

          log_error ("invalid signature: %s\n", gpg_strerror (rc));
          fpr = gpgsm_get_fingerprint_hexstring (cert, GCRY_MD_SHA1);
          gpgsm_status (ctrl, STATUS_BADSIG, fpr);
          xfree (fpr);
          goto next_signer;
        }
      rc = gpgsm_cert_use_verify_p (cert); /*(this displays an info message)*/
      if (rc)
        {
          gpgsm_status_with_err_code (ctrl, STATUS_ERROR, "verify.keyusage",
                                      gpg_err_code (rc));
          rc = 0;
        }

      if (DBG_X509)
        log_debug ("signature okay - checking certs\n");
      rc = gpgsm_validate_chain (ctrl, cert, keyexptime);
      if (gpg_err_code (rc) == GPG_ERR_CERT_EXPIRED)
        {
          gpgsm_status (ctrl, STATUS_EXPKEYSIG, NULL);
          rc = 0;
        }
      else
        gpgsm_status (ctrl, STATUS_GOODSIG, NULL);
      
      {
        char *buf, *fpr, *tstr;

        fpr = gpgsm_get_fingerprint_hexstring (cert, GCRY_MD_SHA1);
        tstr = strtimestamp_r (sigtime);
        buf = xmalloc ( strlen(fpr) + strlen (tstr) + 120);
        sprintf (buf, "%s %s %s %s", fpr, tstr,
                 sigtime, keyexptime );
        xfree (tstr);
        xfree (fpr);
        gpgsm_status (ctrl, STATUS_VALIDSIG, buf);
        xfree (buf);
      }

      if (rc) /* of validate_chain */
        {
          log_error ("invalid certification chain: %s\n", gpg_strerror (rc));
          if (gpg_err_code (rc) == GPG_ERR_BAD_CERT_CHAIN
              || gpg_err_code (rc) == GPG_ERR_BAD_CERT
              || gpg_err_code (rc) == GPG_ERR_BAD_CA_CERT
              || gpg_err_code (rc) == GPG_ERR_CERT_REVOKED)
            gpgsm_status_with_err_code (ctrl, STATUS_TRUST_NEVER, NULL,
                                        gpg_err_code (rc));
          else
            gpgsm_status_with_err_code (ctrl, STATUS_TRUST_UNDEFINED, NULL, 
                                        gpg_err_code (rc));
          goto next_signer;
        }

      for (i=0; (p = ksba_cert_get_subject (cert, i)); i++)
        {
          log_info (!i? _("Good signature from")
                      : _("                aka"));
          log_printf (" \"");
          gpgsm_print_name (log_get_stream (), p);
          log_printf ("\"\n");
          ksba_free (p);
        }

      gpgsm_status (ctrl, STATUS_TRUST_FULLY, NULL);
          

    next_signer:
      rc = 0;
      xfree (issuer);
      xfree (serial);
      xfree (sigval);
      xfree (msgdigest);
      ksba_cert_release (cert);
      cert = NULL;
    }
  rc = 0;
  if (err)
    { /* FIXME: still needed? */
      log_error ("ksba error: %s\n", gpg_strerror (err));
      rc = err;
    }    



 leave:
  ksba_cms_release (cms);
  gpgsm_destroy_reader (b64reader);
  gpgsm_destroy_writer (b64writer);
  keydb_release (kh); 
  gcry_md_close (data_md);
  if (fp)
    fclose (fp);

  if (rc)
    {
      char numbuf[50];
      sprintf (numbuf, "%d", rc );
      gpgsm_status2 (ctrl, STATUS_ERROR, "verify.leave",
                     numbuf, NULL);
    }

  return rc;
}