sm/sign.c

   1 /* sign.c - Sign a message
   2  *      Copyright (C) 2001, 2002, 2003, 2008 Free Software Foundation, Inc.
   3  *
   4  * This file is part of GnuPG.
   5  *
   6  * GnuPG is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License as published by
   8  * the Free Software Foundation; either version 3 of the License, or
   9  * (at your option) any later version.
  10  *
  11  * GnuPG is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with this program; if not, see <http://www.gnu.org/licenses/>.
  18  */
  19
  20 #include <config.h>
  21 #include <stdio.h>
  22 #include <stdlib.h>
  23 #include <string.h>
  24 #include <errno.h>
  25 #include <unistd.h>
  26 #include <time.h>
  27 #include <assert.h>
  28
  29 #include "gpgsm.h"
  30 #include <gcrypt.h>
  31 #include <ksba.h>
  32
  33 #include "keydb.h"
  34 #include "i18n.h"
  35
  36
  37 static void
  38 hash_data (int fd, gcry_md_hd_t md)
  39 {
  40   FILE *fp;
  41   char buffer[4096];
  42   int nread;
  43
  44   fp = fdopen ( dup (fd), "rb");
  45   if (!fp)
  46     {
  47       log_error ("fdopen(%d) failed: %s\n", fd, strerror (errno));
  48       return;
  49     }
  50
  51   do
  52     {
  53       nread = fread (buffer, 1, DIM(buffer), fp);
  54       gcry_md_write (md, buffer, nread);
  55     }
  56   while (nread);
  57   if (ferror (fp))
  58       log_error ("read error on fd %d: %s\n", fd, strerror (errno));
  59   fclose (fp);
  60 }
  61
  62 static int
  63 hash_and_copy_data (int fd, gcry_md_hd_t md, ksba_writer_t writer)
  64 {
  65   gpg_error_t err;
  66   FILE *fp;
  67   char buffer[4096];
  68   int nread;
  69   int rc = 0;
  70   int any = 0;
  71
  72   fp = fdopen ( dup (fd), "rb");
  73   if (!fp)
  74     {
  75       gpg_error_t tmperr = gpg_error (gpg_err_code_from_errno (errno));
  76       log_error ("fdopen(%d) failed: %s\n", fd, strerror (errno));
  77       return tmperr;
  78     }
  79
  80   do
  81     {
  82       nread = fread (buffer, 1, DIM(buffer), fp);
  83       if (nread)
  84         {
  85           any = 1;
  86           gcry_md_write (md, buffer, nread);
  87           err = ksba_writer_write_octet_string (writer, buffer, nread, 0);
  88           if (err)
  89             {
  90               log_error ("write failed: %s\n", gpg_strerror (err));
  91               rc = err;
  92             }
  93         }
  94     }
  95   while (nread && !rc);
  96   if (ferror (fp))
  97     {
  98       rc = gpg_error (gpg_err_code_from_errno (errno));
  99       log_error ("read error on fd %d: %s\n", fd, strerror (errno));
 100     }
 101   fclose (fp);
 102   if (!any)
 103     {
 104       /* We can't allow to sign an empty message because it does not
 105          make much sense and more seriously, ksba-cms_build has
 106          already written the tag for data and now expects an octet
 107          string but an octet string of zeize 0 is illegal. */
 108       log_error ("cannot sign an empty message\n");
 109       rc = gpg_error (GPG_ERR_NO_DATA);
 110     }
 111   if (!rc)
 112     {
 113       err = ksba_writer_write_octet_string (writer, NULL, 0, 1);
 114       if (err)
 115         {
 116           log_error ("write failed: %s\n", gpg_strerror (err));
 117           rc = err;
 118         }
 119     }
 120
 121   return rc;
 122 }
 123
 124
 125 /* Get the default certificate which is defined as the first
 126    certificate capable of signing returned by the keyDB and has a
 127    secret key available. */
 128 int
 129 gpgsm_get_default_cert (ctrl_t ctrl, ksba_cert_t *r_cert)
 130 {
 131   KEYDB_HANDLE hd;
 132   ksba_cert_t cert = NULL;
 133   int rc;
 134   char *p;
 135
 136   hd = keydb_new (0);
 137   if (!hd)
 138     return gpg_error (GPG_ERR_GENERAL);
 139   rc = keydb_search_first (hd);
 140   if (rc)
 141     {
 142       keydb_release (hd);
 143       return rc;
 144     }
 145
 146   do
 147     {
 148       rc = keydb_get_cert (hd, &cert);
 149       if (rc)
 150         {
 151           log_error ("keydb_get_cert failed: %s\n", gpg_strerror (rc));
 152           keydb_release (hd);
 153           return rc;
 154         }
 155
 156       if (!gpgsm_cert_use_sign_p (cert))
 157         {
 158           p = gpgsm_get_keygrip_hexstring (cert);
 159           if (p)
 160             {
 161               if (!gpgsm_agent_havekey (ctrl, p))
 162                 {
 163                   xfree (p);
 164                   keydb_release (hd);
 165                   *r_cert = cert;
 166                   return 0; /* got it */
 167                 }
 168               xfree (p);
 169             }
 170         }
 171
 172       ksba_cert_release (cert);
 173       cert = NULL;
 174     }
 175   while (!(rc = keydb_search_next (hd)));
 176   if (rc && rc != -1)
 177     log_error ("keydb_search_next failed: %s\n", gpg_strerror (rc));
 178
 179   ksba_cert_release (cert);
 180   keydb_release (hd);
 181   return rc;
 182 }
 183
 184
 185 static ksba_cert_t
 186 get_default_signer (ctrl_t ctrl)
 187 {
 188   KEYDB_SEARCH_DESC desc;
 189   ksba_cert_t cert = NULL;
 190   KEYDB_HANDLE kh = NULL;
 191   int rc;
 192
 193   if (!opt.local_user)
 194     {
 195       rc = gpgsm_get_default_cert (ctrl, &cert);
 196       if (rc)
 197         {
 198           if (rc != -1)
 199             log_debug ("failed to find default certificate: %s\n",
 200                        gpg_strerror (rc));
 201           return NULL;
 202         }
 203       return cert;
 204     }
 205
 206   rc = keydb_classify_name (opt.local_user, &desc);
 207   if (rc)
 208     {
 209       log_error ("failed to find default signer: %s\n", gpg_strerror (rc));
 210       return NULL;
 211     }
 212
 213   kh = keydb_new (0);
 214   if (!kh)
 215     return NULL;
 216
 217   rc = keydb_search (kh, &desc, 1);
 218   if (rc)
 219     {
 220       log_debug ("failed to find default certificate: rc=%d\n", rc);
 221     }
 222   else
 223     {
 224       rc = keydb_get_cert (kh, &cert);
 225       if (rc)
 226         {
 227           log_debug ("failed to get cert: rc=%d\n", rc);
 228         }
 229     }
 230
 231   keydb_release (kh);
 232   return cert;
 233 }
 234
 235 /* Depending on the options in CTRL add the certificate CERT as well as
 236    other certificate up in the chain to the Root-CA to the CMS
 237    object. */
 238 static int
 239 add_certificate_list (ctrl_t ctrl, ksba_cms_t cms, ksba_cert_t cert)
 240 {
 241   gpg_error_t err;
 242   int rc = 0;
 243   ksba_cert_t next = NULL;
 244   int n;
 245   int not_root = 0;
 246
 247   ksba_cert_ref (cert);
 248
 249   n = ctrl->include_certs;
 250   log_debug ("adding certificates at level %d\n", n);
 251   if (n == -2)
 252     {
 253       not_root = 1;
 254       n = -1;
 255     }
 256   if (n < 0 || n > 50)
 257     n = 50; /* We better apply an upper bound */
 258
 259   /* First add my own certificate unless we don't want any certificate
 260      included at all. */
 261   if (n)
 262     {
 263       if (not_root && gpgsm_is_root_cert (cert))
 264         err = 0;
 265       else
 266         err = ksba_cms_add_cert (cms, cert);
 267       if (err)
 268         goto ksba_failure;
 269       if (n>0)
 270         n--;
 271     }
 272   /* Walk the chain to include all other certificates.  Note that a -1
 273      used for N makes sure that there is no limit and all certs get
 274      included. */
 275   while ( n-- && !(rc = gpgsm_walk_cert_chain (ctrl, cert, &next)) )
 276     {
 277       if (not_root && gpgsm_is_root_cert (next))
 278         err = 0;
 279       else
 280         err = ksba_cms_add_cert (cms, next);
 281       ksba_cert_release (cert);
 282       cert = next; next = NULL;
 283       if (err)
 284         goto ksba_failure;
 285     }
 286   ksba_cert_release (cert);
 287
 288   return rc == -1? 0: rc;
 289
 290  ksba_failure:
 291   ksba_cert_release (cert);
 292   log_error ("ksba_cms_add_cert failed: %s\n", gpg_strerror (err));
 293   return err;
 294 }
 295
 296
 297
 298 \f
 299 /* Perform a sign operation.
 300
 301    Sign the data received on DATA-FD in embedded mode or in detached
 302    mode when DETACHED is true.  Write the signature to OUT_FP.  The
 303    keys used to sign are taken from SIGNERLIST or the default one will
 304    be used if the value of this argument is NULL. */
 305 int
 306 gpgsm_sign (ctrl_t ctrl, certlist_t signerlist,
 307             int data_fd, int detached, FILE *out_fp)
 308 {
 309   int i, rc;
 310   gpg_error_t err;
 311   Base64Context b64writer = NULL;
 312   ksba_writer_t writer;
 313   ksba_cms_t cms = NULL;
 314   ksba_stop_reason_t stopreason;
 315   KEYDB_HANDLE kh = NULL;
 316   gcry_md_hd_t data_md = NULL;
 317   int signer;
 318   const char *algoid;
 319   int algo;
 320   ksba_isotime_t signed_at;
 321   certlist_t cl;
 322   int release_signerlist = 0;
 323
 324   kh = keydb_new (0);
 325   if (!kh)
 326     {
 327       log_error (_("failed to allocated keyDB handle\n"));
 328       rc = gpg_error (GPG_ERR_GENERAL);
 329       goto leave;
 330     }
 331
 332   ctrl->pem_name = "SIGNED MESSAGE";
 333   rc = gpgsm_create_writer (&b64writer, ctrl, out_fp, NULL, &writer);
 334   if (rc)
 335     {
 336       log_error ("can't create writer: %s\n", gpg_strerror (rc));
 337       goto leave;
 338     }
 339
 340   err = ksba_cms_new (&cms);
 341   if (err)
 342     {
 343       rc = err;
 344       goto leave;
 345     }
 346
 347   err = ksba_cms_set_reader_writer (cms, NULL, writer);
 348   if (err)
 349     {
 350       log_debug ("ksba_cms_set_reader_writer failed: %s\n",
 351                  gpg_strerror (err));
 352       rc = err;
 353       goto leave;
 354     }
 355
 356   /* We are going to create signed data with data as encap. content */
 357   err = ksba_cms_set_content_type (cms, 0, KSBA_CT_SIGNED_DATA);
 358   if (!err)
 359     err = ksba_cms_set_content_type (cms, 1, KSBA_CT_DATA);
 360   if (err)
 361     {
 362       log_debug ("ksba_cms_set_content_type failed: %s\n",
 363                  gpg_strerror (err));
 364       rc = err;
 365       goto leave;
 366     }
 367
 368   /* If no list of signers is given, use the default certificate. */
 369   if (!signerlist)
 370     {
 371       ksba_cert_t cert = get_default_signer (ctrl);
 372       if (!cert)
 373         {
 374           log_error ("no default signer found\n");
 375           rc = gpg_error (GPG_ERR_GENERAL);
 376           goto leave;
 377         }
 378
 379       /* Although we don't check for ambigious specification we will
 380          check that the signer's certificate is usable and valid.  */
 381       rc = gpgsm_cert_use_sign_p (cert);
 382       if (!rc)
 383         rc = gpgsm_validate_chain (ctrl, cert, "", NULL, 0, NULL, 0, NULL);
 384       if (rc)
 385         goto leave;
 386
 387       /* That one is fine - create signerlist. */
 388       signerlist = xtrycalloc (1, sizeof *signerlist);
 389       if (!signerlist)
 390         {
 391           rc = out_of_core ();
 392           ksba_cert_release (cert);
 393           goto leave;
 394         }
 395       signerlist->cert = cert;
 396       release_signerlist = 1;
 397     }
 398
 399   /* Figure out the hash algorithm to use. We do not want to use the
 400      one for the certificate but if possible an OID for the plain
 401      algorithm.  */
 402   for (i=0, cl=signerlist; cl; cl = cl->next, i++)
 403     {
 404       const char *oid = ksba_cert_get_digest_algo (cl->cert);
 405
 406       cl->hash_algo = oid ? gcry_md_map_name (oid) : 0;
 407       switch (cl->hash_algo)
 408         {
 409         case GCRY_MD_SHA1:   oid = "1.3.14.3.2.26"; break;
 410         case GCRY_MD_RMD160: oid = "1.3.36.3.2.1"; break;
 411         case GCRY_MD_SHA224: oid = "2.16.840.1.101.3.4.2.4"; break;
 412         case GCRY_MD_SHA256: oid = "2.16.840.1.101.3.4.2.1"; break;
 413         case GCRY_MD_SHA384: oid = "2.16.840.1.101.3.4.2.2"; break;
 414         case GCRY_MD_SHA512: oid = "2.16.840.1.101.3.4.2.3"; break;
 415 /*         case GCRY_MD_WHIRLPOOL: oid = "No OID yet"; break; */
 416
 417         case GCRY_MD_MD5:  /* We don't want to use MD5.  */
 418         case 0:            /* No algorithm found in cert.  */
 419         default:           /* Other algorithms.  */
 420           log_info (_("hash algorithm %d (%s) for signer %d not supported;"
 421                       " using %s\n"),
 422                     cl->hash_algo, oid? oid: "?", i,
 423                     gcry_md_algo_name (GCRY_MD_SHA1));
 424           cl->hash_algo = GCRY_MD_SHA1;
 425           oid = "1.3.14.3.2.26";
 426           break;
 427         }
 428       cl->hash_algo_oid = oid;
 429     }
 430   if (opt.verbose)
 431     {
 432       for (i=0, cl=signerlist; cl; cl = cl->next, i++)
 433         log_info (_("hash algorithm used for signer %d: %s (%s)\n"),
 434                   i, gcry_md_algo_name (cl->hash_algo), cl->hash_algo_oid);
 435     }
 436
 437
 438   /* Gather certificates of signers and store them in the CMS object. */
 439   for (cl=signerlist; cl; cl = cl->next)
 440     {
 441       rc = gpgsm_cert_use_sign_p (cl->cert);
 442       if (rc)
 443         goto leave;
 444
 445       err = ksba_cms_add_signer (cms, cl->cert);
 446       if (err)
 447         {
 448           log_error ("ksba_cms_add_signer failed: %s\n", gpg_strerror (err));
 449           rc = err;
 450           goto leave;
 451         }
 452       rc = add_certificate_list (ctrl, cms, cl->cert);
 453       if (rc)
 454         {
 455           log_error ("failed to store list of certificates: %s\n",
 456                      gpg_strerror(rc));
 457           goto leave;
 458         }
 459       /* Set the hash algorithm we are going to use */
 460       err = ksba_cms_add_digest_algo (cms, cl->hash_algo_oid);
 461       if (err)
 462         {
 463           log_debug ("ksba_cms_add_digest_algo failed: %s\n",
 464                      gpg_strerror (err));
 465           rc = err;
 466           goto leave;
 467         }
 468     }
 469
 470
 471   /* Check whether one of the certificates is qualified.  Note that we
 472      already validated the certificate and thus the user data stored
 473      flag must be available. */
 474   for (cl=signerlist; cl; cl = cl->next)
 475     {
 476       size_t buflen;
 477       char buffer[1];
 478
 479       err = ksba_cert_get_user_data (cl->cert, "is_qualified",
 480                                      &buffer, sizeof (buffer), &buflen);
 481       if (err || !buflen)
 482         {
 483           log_error (_("checking for qualified certificate failed: %s\n"),
 484                      gpg_strerror (err));
 485           rc = err;
 486           goto leave;
 487         }
 488       if (*buffer)
 489         err = gpgsm_qualified_consent (ctrl, cl->cert);
 490       else
 491         err = gpgsm_not_qualified_warning (ctrl, cl->cert);
 492       if (err)
 493         {
 494           rc = err;
 495           goto leave;
 496         }
 497     }
 498
 499   /* Prepare hashing (actually we are figuring out what we have set
 500      above). */
 501   rc = gcry_md_open (&data_md, 0, 0);
 502   if (rc)
 503     {
 504       log_error ("md_open failed: %s\n", gpg_strerror (rc));
 505       goto leave;
 506     }
 507   if (DBG_HASHING)
 508     gcry_md_start_debug (data_md, "sign.data");
 509
 510   for (i=0; (algoid=ksba_cms_get_digest_algo_list (cms, i)); i++)
 511     {
 512       algo = gcry_md_map_name (algoid);
 513       if (!algo)
 514         {
 515           log_error ("unknown hash algorithm `%s'\n", algoid? algoid:"?");
 516           rc = gpg_error (GPG_ERR_BUG);
 517           goto leave;
 518         }
 519       gcry_md_enable (data_md, algo);
 520     }
 521
 522   if (detached)
 523     { /* We hash the data right now so that we can store the message
 524          digest.  ksba_cms_build() takes this as an flag that detached
 525          data is expected. */
 526       unsigned char *digest;
 527       size_t digest_len;
 528
 529       hash_data (data_fd, data_md);
 530       for (cl=signerlist,signer=0; cl; cl = cl->next, signer++)
 531         {
 532           digest = gcry_md_read (data_md, cl->hash_algo);
 533           digest_len = gcry_md_get_algo_dlen (cl->hash_algo);
 534           if ( !digest || !digest_len )
 535             {
 536               log_error ("problem getting the hash of the data\n");
 537               rc = gpg_error (GPG_ERR_BUG);
 538               goto leave;
 539             }
 540           err = ksba_cms_set_message_digest (cms, signer, digest, digest_len);
 541           if (err)
 542             {
 543               log_error ("ksba_cms_set_message_digest failed: %s\n",
 544                          gpg_strerror (err));
 545               rc = err;
 546               goto leave;
 547             }
 548         }
 549     }
 550
 551   gnupg_get_isotime (signed_at);
 552   for (cl=signerlist,signer=0; cl; cl = cl->next, signer++)
 553     {
 554       err = ksba_cms_set_signing_time (cms, signer, signed_at);
 555       if (err)
 556         {
 557           log_error ("ksba_cms_set_signing_time failed: %s\n",
 558                      gpg_strerror (err));
 559           rc = err;
 560           goto leave;
 561         }
 562     }
 563
 564   /* We need to write at least a minimal list of our capabilities to
 565      try to convince some MUAs to use 3DES and not the crippled
 566      RC2. Our list is:
 567
 568         aes128-CBC
 569         des-EDE3-CBC
 570   */
 571   err = ksba_cms_add_smime_capability (cms, "2.16.840.1.101.3.4.1.2", NULL, 0);
 572   if (!err)
 573     err = ksba_cms_add_smime_capability (cms, "1.2.840.113549.3.7", NULL, 0);
 574   if (err)
 575     {
 576       log_error ("ksba_cms_add_smime_capability failed: %s\n",
 577                  gpg_strerror (err));
 578       goto leave;
 579     }
 580
 581
 582   /* Main building loop. */
 583   do
 584     {
 585       err = ksba_cms_build (cms, &stopreason);
 586       if (err)
 587         {
 588           log_debug ("ksba_cms_build failed: %s\n", gpg_strerror (err));
 589           rc = err;
 590           goto leave;
 591         }
 592
 593       if (stopreason == KSBA_SR_BEGIN_DATA)
 594         {
 595           /* Hash the data and store the message digest. */
 596           unsigned char *digest;
 597           size_t digest_len;
 598
 599           assert (!detached);
 600
 601           rc = hash_and_copy_data (data_fd, data_md, writer);
 602           if (rc)
 603             goto leave;
 604           for (cl=signerlist,signer=0; cl; cl = cl->next, signer++)
 605             {
 606               digest = gcry_md_read (data_md, cl->hash_algo);
 607               digest_len = gcry_md_get_algo_dlen (cl->hash_algo);
 608               if ( !digest || !digest_len )
 609                 {
 610                   log_error ("problem getting the hash of the data\n");
 611                   rc = gpg_error (GPG_ERR_BUG);
 612                   goto leave;
 613                 }
 614               err = ksba_cms_set_message_digest (cms, signer,
 615                                                  digest, digest_len);
 616               if (err)
 617                 {
 618                   log_error ("ksba_cms_set_message_digest failed: %s\n",
 619                              gpg_strerror (err));
 620                   rc = err;
 621                   goto leave;
 622                 }
 623             }
 624         }
 625       else if (stopreason == KSBA_SR_NEED_SIG)
 626         {
 627           /* Compute the signature for all signers.  */
 628           gcry_md_hd_t md;
 629
 630           rc = gcry_md_open (&md, 0, 0);
 631           if (rc)
 632             {
 633               log_error ("md_open failed: %s\n", gpg_strerror (rc));
 634               goto leave;
 635             }
 636           if (DBG_HASHING)
 637             gcry_md_start_debug (md, "sign.attr");
 638           ksba_cms_set_hash_function (cms, HASH_FNC, md);
 639           for (cl=signerlist,signer=0; cl; cl = cl->next, signer++)
 640             {
 641               unsigned char *sigval = NULL;
 642               char *buf, *fpr;
 643
 644               if (signer)
 645                 gcry_md_reset (md);
 646               {
 647                 certlist_t cl_tmp;
 648
 649                 for (cl_tmp=signerlist; cl_tmp; cl_tmp = cl_tmp->next)
 650                   gcry_md_enable (md, cl_tmp->hash_algo);
 651               }
 652
 653               rc = ksba_cms_hash_signed_attrs (cms, signer);
 654               if (rc)
 655                 {
 656                   log_debug ("hashing signed attrs failed: %s\n",
 657                              gpg_strerror (rc));
 658                   gcry_md_close (md);
 659                   goto leave;
 660                 }
 661
 662               rc = gpgsm_create_cms_signature (ctrl, cl->cert,
 663                                                md, cl->hash_algo, &sigval);
 664               if (rc)
 665                 {
 666                   gcry_md_close (md);
 667                   goto leave;
 668                 }
 669
 670               err = ksba_cms_set_sig_val (cms, signer, sigval);
 671               xfree (sigval);
 672               if (err)
 673                 {
 674                   log_error ("failed to store the signature: %s\n",
 675                              gpg_strerror (err));
 676                   rc = err;
 677                   gcry_md_close (md);
 678                   goto leave;
 679                 }
 680
 681               /* write a status message */
 682               fpr = gpgsm_get_fingerprint_hexstring (cl->cert, GCRY_MD_SHA1);
 683               if (!fpr)
 684                 {
 685                   rc = gpg_error (GPG_ERR_ENOMEM);
 686                   gcry_md_close (md);
 687                   goto leave;
 688                 }
 689               {
 690                 int pkalgo = gpgsm_get_key_algo_info (cl->cert, NULL);
 691                 rc = asprintf (&buf, "%c %d %d 00 %s %s",
 692                                detached? 'D':'S',
 693                                pkalgo,
 694                                cl->hash_algo,
 695                                signed_at,
 696                                fpr);
 697               }
 698               xfree (fpr);
 699               if (rc < 0)
 700                 {
 701                   rc = gpg_error (GPG_ERR_ENOMEM);
 702                   gcry_md_close (md);
 703                   goto leave;
 704                 }
 705               rc = 0;
 706               gpgsm_status (ctrl, STATUS_SIG_CREATED, buf);
 707               free (buf); /* yes, we must use the regular free() here */
 708             }
 709           gcry_md_close (md);
 710
 711         }
 712     }
 713   while (stopreason != KSBA_SR_READY);
 714
 715   rc = gpgsm_finish_writer (b64writer);
 716   if (rc)
 717     {
 718       log_error ("write failed: %s\n", gpg_strerror (rc));
 719       goto leave;
 720     }
 721
 722   log_info ("signature created\n");
 723
 724
 725  leave:
 726   if (rc)
 727     log_error ("error creating signature: %s <%s>\n",
 728                gpg_strerror (rc), gpg_strsource (rc) );
 729   if (release_signerlist)
 730     gpgsm_release_certlist (signerlist);
 731   ksba_cms_release (cms);
 732   gpgsm_destroy_writer (b64writer);
 733   keydb_release (kh);
 734   gcry_md_close (data_md);
 735   return rc;
 736 }