sm/sign.c

   1 /* sign.c - Sign a message
   2  *      Copyright (C) 2001, 2002, 2003 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 2 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, write to the Free Software
  18  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  19  */
  20
  21 #include <config.h>
  22 #include <stdio.h>
  23 #include <stdlib.h>
  24 #include <string.h>
  25 #include <errno.h>
  26 #include <unistd.h>
  27 #include <time.h>
  28 #include <assert.h>
  29
  30 #include "gpgsm.h"
  31 #include <gcrypt.h>
  32 #include <ksba.h>
  33
  34 #include "keydb.h"
  35 #include "i18n.h"
  36
  37
  38 static void
  39 hash_data (int fd, gcry_md_hd_t md)
  40 {
  41   FILE *fp;
  42   char buffer[4096];
  43   int nread;
  44
  45   fp = fdopen ( dup (fd), "rb");
  46   if (!fp)
  47     {
  48       log_error ("fdopen(%d) failed: %s\n", fd, strerror (errno));
  49       return;
  50     }
  51
  52   do
  53     {
  54       nread = fread (buffer, 1, DIM(buffer), fp);
  55       gcry_md_write (md, buffer, nread);
  56     }
  57   while (nread);
  58   if (ferror (fp))
  59       log_error ("read error on fd %d: %s\n", fd, strerror (errno));
  60   fclose (fp);
  61 }
  62
  63 static int
  64 hash_and_copy_data (int fd, gcry_md_hd_t md, ksba_writer_t writer)
  65 {
  66   gpg_error_t err;
  67   FILE *fp;
  68   char buffer[4096];
  69   int nread;
  70   int rc = 0;
  71   int any = 0;
  72
  73   fp = fdopen ( dup (fd), "rb");
  74   if (!fp)
  75     {
  76       gpg_error_t tmperr = gpg_error (gpg_err_code_from_errno (errno));
  77       log_error ("fdopen(%d) failed: %s\n", fd, strerror (errno));
  78       return tmperr;
  79     }
  80
  81   do
  82     {
  83       nread = fread (buffer, 1, DIM(buffer), fp);
  84       if (nread)
  85         {
  86           any = 1;
  87           gcry_md_write (md, buffer, nread);
  88           err = ksba_writer_write_octet_string (writer, buffer, nread, 0);
  89           if (err)
  90             {
  91               log_error ("write failed: %s\n", gpg_strerror (err));
  92               rc = err;
  93             }
  94         }
  95     }
  96   while (nread && !rc);
  97   if (ferror (fp))
  98     {
  99       rc = gpg_error (gpg_err_code_from_errno (errno));
 100       log_error ("read error on fd %d: %s\n", fd, strerror (errno));
 101     }
 102   fclose (fp);
 103   if (!any)
 104     {
 105       /* We can't allow to sign an empty message because it does not
 106          make much sense and more seriously, ksba-cms_build has
 107          already written the tag for data and now expects an octet
 108          string but an octet string of zeize 0 is illegal. */
 109       log_error ("cannot sign an empty message\n");
 110       rc = gpg_error (GPG_ERR_NO_DATA);
 111     }
 112   if (!rc)
 113     {
 114       err = ksba_writer_write_octet_string (writer, NULL, 0, 1);
 115       if (err)
 116         {
 117           log_error ("write failed: %s\n", gpg_strerror (err));
 118           rc = err;
 119         }
 120     }
 121
 122   return rc;
 123 }
 124
 125
 126 /* Get the default certificate which is defined as the first one our
 127    keyDB returns and has a 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       p = gpgsm_get_keygrip_hexstring (cert);
 157       if (p)
 158         {
 159           if (!gpgsm_agent_havekey (ctrl, p))
 160             {
 161               xfree (p);
 162               keydb_release (hd);
 163               *r_cert = cert;
 164               return 0; /* got it */
 165             }
 166           xfree (p);
 167         }
 168
 169       ksba_cert_release (cert);
 170       cert = NULL;
 171     }
 172   while (!(rc = keydb_search_next (hd)));
 173   if (rc && rc != -1)
 174     log_error ("keydb_search_next failed: %s\n", gpg_strerror (rc));
 175
 176   ksba_cert_release (cert);
 177   keydb_release (hd);
 178   return rc;
 179 }
 180
 181
 182 static ksba_cert_t
 183 get_default_signer (ctrl_t ctrl)
 184 {
 185   KEYDB_SEARCH_DESC desc;
 186   ksba_cert_t cert = NULL;
 187   KEYDB_HANDLE kh = NULL;
 188   int rc;
 189
 190   if (!opt.local_user)
 191     {
 192       rc = gpgsm_get_default_cert (ctrl, &cert);
 193       if (rc)
 194         {
 195           if (rc != -1)
 196             log_debug ("failed to find default certificate: %s\n",
 197                        gpg_strerror (rc));
 198           return NULL;
 199         }
 200       return cert;
 201     }
 202
 203   rc = keydb_classify_name (opt.local_user, &desc);
 204   if (rc)
 205     {
 206       log_error ("failed to find default signer: %s\n", gpg_strerror (rc));
 207       return NULL;
 208     }
 209
 210   kh = keydb_new (0);
 211   if (!kh)
 212     return NULL;
 213
 214   rc = keydb_search (kh, &desc, 1);
 215   if (rc)
 216     {
 217       log_debug ("failed to find default certificate: rc=%d\n", rc);
 218     }
 219   else
 220     {
 221       rc = keydb_get_cert (kh, &cert);
 222       if (rc)
 223         {
 224           log_debug ("failed to get cert: rc=%d\n", rc);
 225         }
 226     }
 227
 228   keydb_release (kh);
 229   return cert;
 230 }
 231
 232 /* Depending on the options in CTRL add the certificate CERT as well as
 233    other certificate up in the chain to the Root-CA to the CMS
 234    object. */
 235 static int
 236 add_certificate_list (CTRL ctrl, ksba_cms_t cms, ksba_cert_t cert)
 237 {
 238   gpg_error_t err;
 239   int rc = 0;
 240   ksba_cert_t next = NULL;
 241   int n;
 242   int not_root = 0;
 243
 244   ksba_cert_ref (cert);
 245
 246   n = ctrl->include_certs;
 247   log_debug ("adding certificates at level %d\n", n);
 248   if (n == -2)
 249     {
 250       not_root = 1;
 251       n = -1;
 252     }
 253   if (n < 0 || n > 50)
 254     n = 50; /* We better apply an upper bound */
 255
 256   /* First add my own certificate unless we don't want any certificate
 257      included at all. */
 258   if (n)
 259     {
 260       if (not_root && gpgsm_is_root_cert (cert))
 261         err = 0;
 262       else
 263         err = ksba_cms_add_cert (cms, cert);
 264       if (err)
 265         goto ksba_failure;
 266       if (n>0)
 267         n--;
 268     }
 269   /* Walk the chain to include all other certificates.  Note that a -1
 270      used for N makes sure that there is no limit and all certs get
 271      included. */
 272   while ( n-- && !(rc = gpgsm_walk_cert_chain (cert, &next)) )
 273     {
 274       if (not_root && gpgsm_is_root_cert (next))
 275         err = 0;
 276       else
 277         err = ksba_cms_add_cert (cms, next);
 278       ksba_cert_release (cert);
 279       cert = next; next = NULL;
 280       if (err)
 281         goto ksba_failure;
 282     }
 283   ksba_cert_release (cert);
 284
 285   return rc == -1? 0: rc;
 286
 287  ksba_failure:
 288   ksba_cert_release (cert);
 289   log_error ("ksba_cms_add_cert failed: %s\n", gpg_strerror (err));
 290   return err;
 291 }
 292
 293
 294
 295 \f
 296 /* Perform a sign operation.
 297
 298    Sign the data received on DATA-FD in embedded mode or in detached
 299    mode when DETACHED is true.  Write the signature to OUT_FP.  The
 300    keys used to sign are taken from SIGNERLIST or the default one will
 301    be used if the value of this argument is NULL. */
 302 int
 303 gpgsm_sign (CTRL ctrl, CERTLIST signerlist,
 304             int data_fd, int detached, FILE *out_fp)
 305 {
 306   int i, rc;
 307   gpg_error_t err;
 308   Base64Context b64writer = NULL;
 309   ksba_writer_t writer;
 310   ksba_cms_t cms = NULL;
 311   ksba_stop_reason_t stopreason;
 312   KEYDB_HANDLE kh = NULL;
 313   gcry_md_hd_t data_md = NULL;
 314   int signer;
 315   const char *algoid;
 316   int algo;
 317   ksba_isotime_t signed_at;
 318   CERTLIST cl;
 319   int release_signerlist = 0;
 320
 321   kh = keydb_new (0);
 322   if (!kh)
 323     {
 324       log_error (_("failed to allocated keyDB handle\n"));
 325       rc = gpg_error (GPG_ERR_GENERAL);
 326       goto leave;
 327     }
 328
 329   ctrl->pem_name = "SIGNED MESSAGE";
 330   rc = gpgsm_create_writer (&b64writer, ctrl, out_fp, &writer);
 331   if (rc)
 332     {
 333       log_error ("can't create writer: %s\n", gpg_strerror (rc));
 334       goto leave;
 335     }
 336
 337   err = ksba_cms_new (&cms);
 338   if (err)
 339     {
 340       rc = err;
 341       goto leave;
 342     }
 343
 344   err = ksba_cms_set_reader_writer (cms, NULL, writer);
 345   if (err)
 346     {
 347       log_debug ("ksba_cms_set_reader_writer failed: %s\n",
 348                  gpg_strerror (err));
 349       rc = err;
 350       goto leave;
 351     }
 352
 353   /* We are going to create signed data with data as encap. content */
 354   err = ksba_cms_set_content_type (cms, 0, KSBA_CT_SIGNED_DATA);
 355   if (!err)
 356     err = ksba_cms_set_content_type (cms, 1, KSBA_CT_DATA);
 357   if (err)
 358     {
 359       log_debug ("ksba_cms_set_content_type failed: %s\n",
 360                  gpg_strerror (err));
 361       rc = err;
 362       goto leave;
 363     }
 364
 365   /* If no list of signers is given, use a default one. */
 366   if (!signerlist)
 367     {
 368       ksba_cert_t cert = get_default_signer (ctrl);
 369       if (!cert)
 370         {
 371           log_error ("no default signer found\n");
 372           rc = gpg_error (GPG_ERR_GENERAL);
 373           goto leave;
 374         }
 375
 376       /* Although we don't check for ambigious specification we will
 377          check that the signer's certificate is is usable and
 378          valid. */
 379       rc = gpgsm_cert_use_sign_p (cert);
 380       if (!rc)
 381         rc = gpgsm_validate_chain (ctrl, cert, NULL, 0, NULL, 0);
 382       if (rc)
 383         goto leave;
 384
 385       /* That one is fine - create signerlist. */
 386       signerlist = xtrycalloc (1, sizeof *signerlist);
 387       if (!signerlist)
 388         {
 389           rc = OUT_OF_CORE (errno);
 390           ksba_cert_release (cert);
 391           goto leave;
 392         }
 393       signerlist->cert = cert;
 394       release_signerlist = 1;
 395     }
 396
 397
 398   /* Gather certificates of signers and store them in the CMS object. */
 399   for (cl=signerlist; cl; cl = cl->next)
 400     {
 401       rc = gpgsm_cert_use_sign_p (cl->cert);
 402       if (rc)
 403         goto leave;
 404
 405       err = ksba_cms_add_signer (cms, cl->cert);
 406       if (err)
 407         {
 408           log_error ("ksba_cms_add_signer failed: %s\n", gpg_strerror (err));
 409           rc = err;
 410           goto leave;
 411         }
 412       rc = add_certificate_list (ctrl, cms, cl->cert);
 413       if (rc)
 414         {
 415           log_error ("failed to store list of certificates: %s\n",
 416                      gpg_strerror(rc));
 417           goto leave;
 418         }
 419       /* Set the hash algorithm we are going to use */
 420       err = ksba_cms_add_digest_algo (cms, "1.3.14.3.2.26" /*SHA-1*/);
 421       if (err)
 422         {
 423           log_debug ("ksba_cms_add_digest_algo failed: %s\n",
 424                      gpg_strerror (err));
 425           rc = err;
 426           goto leave;
 427         }
 428     }
 429
 430   /* Prepare hashing (actually we are figuring out what we have set above)*/
 431   rc = gcry_md_open (&data_md, 0, 0);
 432   if (rc)
 433     {
 434       log_error ("md_open failed: %s\n", gpg_strerror (rc));
 435       goto leave;
 436     }
 437   if (DBG_HASHING)
 438     gcry_md_start_debug (data_md, "sign.data");
 439
 440   for (i=0; (algoid=ksba_cms_get_digest_algo_list (cms, i)); i++)
 441     {
 442       algo = gcry_md_map_name (algoid);
 443       if (!algo)
 444         {
 445           log_error ("unknown hash algorithm `%s'\n", algoid? algoid:"?");
 446           rc = gpg_error (GPG_ERR_BUG);
 447           goto leave;
 448         }
 449       gcry_md_enable (data_md, algo);
 450     }
 451
 452   if (detached)
 453     { /* we hash the data right now so that we can store the message
 454          digest.  ksba_cms_build() takes this as an flag that detached
 455          data is expected. */
 456       unsigned char *digest;
 457       size_t digest_len;
 458       /* Fixme do this for all signers and get the algo to use from
 459          the signer's certificate - does not make mich sense, but we
 460          should do this consistent as we have already done it above. */
 461       algo = GCRY_MD_SHA1;
 462       hash_data (data_fd, data_md);
 463       digest = gcry_md_read (data_md, algo);
 464       digest_len = gcry_md_get_algo_dlen (algo);
 465       if ( !digest || !digest_len)
 466         {
 467           log_error ("problem getting the hash of the data\n");
 468           rc = gpg_error (GPG_ERR_BUG);
 469           goto leave;
 470         }
 471       for (cl=signerlist,signer=0; cl; cl = cl->next, signer++)
 472         {
 473           err = ksba_cms_set_message_digest (cms, signer, digest, digest_len);
 474           if (err)
 475             {
 476               log_error ("ksba_cms_set_message_digest failed: %s\n",
 477                          gpg_strerror (err));
 478               rc = err;
 479               goto leave;
 480             }
 481         }
 482     }
 483
 484   gnupg_get_isotime (signed_at);
 485   for (cl=signerlist,signer=0; cl; cl = cl->next, signer++)
 486     {
 487       err = ksba_cms_set_signing_time (cms, signer, signed_at);
 488       if (err)
 489         {
 490           log_error ("ksba_cms_set_signing_time failed: %s\n",
 491                      gpg_strerror (err));
 492           rc = err;
 493           goto leave;
 494         }
 495     }
 496
 497   /* We need to write at least a minimal list of our capabilities to
 498      try to convince some MUAs to use 3DEs and not the crippled
 499      RC2. Our list is:
 500
 501         aes128-CBC
 502         des-EDE3-CBC
 503   */
 504   err = ksba_cms_add_smime_capability (cms, "2.16.840.1.101.3.4.1.2", NULL, 0);
 505   if (!err)
 506     err = ksba_cms_add_smime_capability (cms, "1.2.840.113549.3.7", NULL, 0);
 507   if (err)
 508     {
 509       log_error ("ksba_cms_add_smime_capability failed: %s\n",
 510                  gpg_strerror (err));
 511       goto leave;
 512     }
 513
 514
 515   /* Main building loop. */
 516   do
 517     {
 518       err = ksba_cms_build (cms, &stopreason);
 519       if (err)
 520         {
 521           log_debug ("ksba_cms_build failed: %s\n", gpg_strerror (err));
 522           rc = err;
 523           goto leave;
 524         }
 525
 526       if (stopreason == KSBA_SR_BEGIN_DATA)
 527         { /* hash the data and store the message digest */
 528           unsigned char *digest;
 529           size_t digest_len;
 530
 531           assert (!detached);
 532           /* Fixme: get the algo to use from the signer's certificate
 533              - does not make much sense, but we should do this
 534              consistent as we have already done it above.  Code is
 535              mostly duplicated above. */
 536
 537           algo = GCRY_MD_SHA1;
 538           rc = hash_and_copy_data (data_fd, data_md, writer);
 539           if (rc)
 540             goto leave;
 541           digest = gcry_md_read (data_md, algo);
 542           digest_len = gcry_md_get_algo_dlen (algo);
 543           if ( !digest || !digest_len)
 544             {
 545               log_error ("problem getting the hash of the data\n");
 546               rc = gpg_error (GPG_ERR_BUG);
 547               goto leave;
 548             }
 549           for (cl=signerlist,signer=0; cl; cl = cl->next, signer++)
 550             {
 551               err = ksba_cms_set_message_digest (cms, signer,
 552                                                  digest, digest_len);
 553               if (err)
 554                 {
 555                   log_error ("ksba_cms_set_message_digest failed: %s\n",
 556                              gpg_strerror (err));
 557                   rc = err;
 558                   goto leave;
 559                 }
 560             }
 561         }
 562       else if (stopreason == KSBA_SR_NEED_SIG)
 563         { /* calculate the signature for all signers */
 564           gcry_md_hd_t md;
 565
 566           algo = GCRY_MD_SHA1;
 567           rc = gcry_md_open (&md, algo, 0);
 568           if (rc)
 569             {
 570               log_error ("md_open failed: %s\n", gpg_strerror (rc));
 571               goto leave;
 572             }
 573           if (DBG_HASHING)
 574             gcry_md_start_debug (md, "sign.attr");
 575           ksba_cms_set_hash_function (cms, HASH_FNC, md);
 576           for (cl=signerlist,signer=0; cl; cl = cl->next, signer++)
 577             {
 578               char *sigval = NULL;
 579               char *buf, *fpr;
 580
 581               if (signer)
 582                 gcry_md_reset (md);
 583               rc = ksba_cms_hash_signed_attrs (cms, signer);
 584               if (rc)
 585                 {
 586                   log_debug ("hashing signed attrs failed: %s\n",
 587                              gpg_strerror (rc));
 588                   gcry_md_close (md);
 589                   goto leave;
 590                 }
 591
 592               rc = gpgsm_create_cms_signature (ctrl, cl->cert,
 593                                                md, algo, &sigval);
 594               if (rc)
 595                 {
 596                   gcry_md_close (md);
 597                   goto leave;
 598                 }
 599
 600               err = ksba_cms_set_sig_val (cms, signer, sigval);
 601               xfree (sigval);
 602               if (err)
 603                 {
 604                   log_error ("failed to store the signature: %s\n",
 605                              gpg_strerror (err));
 606                   rc = err;
 607                   gcry_md_close (md);
 608                   goto leave;
 609                 }
 610
 611               /* write a status message */
 612               fpr = gpgsm_get_fingerprint_hexstring (cl->cert, GCRY_MD_SHA1);
 613               if (!fpr)
 614                 {
 615                   rc = gpg_error (GPG_ERR_ENOMEM);
 616                   gcry_md_close (md);
 617                   goto leave;
 618                 }
 619               {
 620                 int pkalgo = gpgsm_get_key_algo_info (cl->cert, NULL);
 621                 rc = asprintf (&buf, "%c %d %d 00 %s %s",
 622                                detached? 'D':'S',
 623                                pkalgo,
 624                                algo,
 625                                signed_at,
 626                                fpr);
 627               }
 628               xfree (fpr);
 629               if (rc < 0)
 630                 {
 631                   rc = gpg_error (GPG_ERR_ENOMEM);
 632                   gcry_md_close (md);
 633                   goto leave;
 634                 }
 635               rc = 0;
 636               gpgsm_status (ctrl, STATUS_SIG_CREATED, buf);
 637               free (buf); /* yes, we must use the regular free() here */
 638             }
 639           gcry_md_close (md);
 640
 641         }
 642     }
 643   while (stopreason != KSBA_SR_READY);
 644
 645   rc = gpgsm_finish_writer (b64writer);
 646   if (rc)
 647     {
 648       log_error ("write failed: %s\n", gpg_strerror (rc));
 649       goto leave;
 650     }
 651
 652   log_info ("signature created\n");
 653
 654
 655  leave:
 656   if (rc)
 657     log_error ("error creating signature: %s <%s>\n",
 658                gpg_strerror (rc), gpg_strsource (rc) );
 659   if (release_signerlist)
 660     gpgsm_release_certlist (signerlist);
 661   ksba_cms_release (cms);
 662   gpgsm_destroy_writer (b64writer);
 663   keydb_release (kh);
 664   gcry_md_close (data_md);
 665   return rc;
 666 }