g10/passphrase.c

   1 /* passphrase.c -  Get a passphrase
   2  * Copyright (C) 1998, 1999, 2000, 2001, 2002, 2003, 2004,
   3  *               2005, 2006, 2007 Free Software Foundation, Inc.
   4  *
   5  * This file is part of GnuPG.
   6  *
   7  * GnuPG is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License as published by
   9  * the Free Software Foundation; either version 3 of the License, or
  10  * (at your option) any later version.
  11  *
  12  * GnuPG is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  * GNU General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU General Public License
  18  * along with this program; if not, see <http://www.gnu.org/licenses/>.
  19  */
  20
  21 #include <config.h>
  22 #include <stddef.h>
  23 #include <stdio.h>
  24 #include <stdlib.h>
  25 #include <string.h>
  26 #include <unistd.h>
  27 #include <assert.h>
  28 #include <errno.h>
  29 #ifdef HAVE_LOCALE_H
  30 #include <locale.h>
  31 #endif
  32 #ifdef HAVE_LANGINFO_CODESET
  33 #include <langinfo.h>
  34 #endif
  35
  36 #include "gpg.h"
  37 #include "util.h"
  38 #include "options.h"
  39 #include "ttyio.h"
  40 #include "cipher.h"
  41 #include "keydb.h"
  42 #include "main.h"
  43 #include "i18n.h"
  44 #include "status.h"
  45 #include "call-agent.h"
  46
  47
  48 static char *fd_passwd = NULL;
  49 static char *next_pw = NULL;
  50 static char *last_pw = NULL;
  51
  52
  53 /* Hash a passphrase using the supplied s2k. If create is true, create
  54    a new salt or what else must be filled into the s2k for a new key.
  55    always needs: dek->algo, s2k->mode, s2k->hash_algo.  */
  56 static void
  57 hash_passphrase ( DEK *dek, char *pw, STRING2KEY *s2k, int create )
  58 {
  59   gcry_md_hd_t md;
  60   int pass, i;
  61   int used = 0;
  62   int pwlen = strlen(pw);
  63
  64   assert ( s2k->hash_algo );
  65   dek->keylen = gcry_cipher_get_algo_keylen (dek->algo);
  66   if ( !(dek->keylen > 0 && dek->keylen <= DIM(dek->key)) )
  67     BUG();
  68
  69   if (gcry_md_open (&md, s2k->hash_algo, 1))
  70     BUG ();
  71   for (pass=0; used < dek->keylen ; pass++ )
  72     {
  73       if ( pass )
  74         {
  75           gcry_md_reset (md);
  76           for (i=0; i < pass; i++ ) /* Preset the hash context.  */
  77             gcry_md_putc (md, 0 );
  78         }
  79
  80       if ( s2k->mode == 1 || s2k->mode == 3 )
  81         {
  82           int len2 = pwlen + 8;
  83           ulong count = len2;
  84
  85           if ( create && !pass )
  86             {
  87               gcry_randomize (s2k->salt, 8, GCRY_STRONG_RANDOM);
  88               if ( s2k->mode == 3 )
  89                 s2k->count = opt.s2k_count;
  90             }
  91
  92           if ( s2k->mode == 3 )
  93             {
  94               count = S2K_DECODE_COUNT(s2k->count);
  95               if ( count < len2 )
  96                 count = len2;
  97             }
  98
  99           /* A little bit complicated because we need a ulong for count. */
 100           while ( count > len2 )  /* maybe iterated+salted */
 101             {
 102               gcry_md_write ( md, s2k->salt, 8 );
 103               gcry_md_write ( md, pw, pwlen );
 104               count -= len2;
 105             }
 106           if ( count < 8 )
 107             gcry_md_write ( md, s2k->salt, count );
 108           else
 109             {
 110               gcry_md_write ( md, s2k->salt, 8 );
 111               count -= 8;
 112               gcry_md_write ( md, pw, count );
 113             }
 114         }
 115       else
 116         gcry_md_write ( md, pw, pwlen );
 117       gcry_md_final( md );
 118
 119       i = gcry_md_get_algo_dlen ( s2k->hash_algo );
 120       if ( i > dek->keylen - used )
 121         i = dek->keylen - used;
 122
 123       memcpy (dek->key+used, gcry_md_read (md, s2k->hash_algo), i);
 124       used += i;
 125     }
 126   gcry_md_close(md);
 127 }
 128
 129
 130
 131 int
 132 have_static_passphrase()
 133 {
 134   return !!fd_passwd && opt.batch;
 135 }
 136
 137 /****************
 138  * Set the passphrase to be used for the next query and only for the next
 139  * one.
 140  */
 141 void
 142 set_next_passphrase( const char *s )
 143 {
 144   xfree(next_pw);
 145   next_pw = NULL;
 146   if ( s )
 147     {
 148       next_pw = xmalloc_secure( strlen(s)+1 );
 149       strcpy (next_pw, s );
 150     }
 151 }
 152
 153 /****************
 154  * Get the last passphrase used in passphrase_to_dek.
 155  * Note: This removes the passphrase from this modules and
 156  * the caller must free the result.  May return NULL:
 157  */
 158 char *
 159 get_last_passphrase()
 160 {
 161   char *p = last_pw;
 162   last_pw = NULL;
 163   return p;
 164 }
 165
 166 /* As if we had used the passphrase - make it the last_pw. */
 167 void
 168 next_to_last_passphrase(void)
 169 {
 170   if (next_pw)
 171     {
 172       last_pw=next_pw;
 173       next_pw=NULL;
 174     }
 175 }
 176
 177 /* Here's an interesting question: since this passphrase was passed in
 178    on the command line, is there really any point in using secure
 179    memory for it?  I'm going with 'yes', since it doesn't hurt, and
 180    might help in some small way (swapping). */
 181
 182 void
 183 set_passphrase_from_string(const char *pass)
 184 {
 185   xfree (fd_passwd);
 186   fd_passwd = xmalloc_secure(strlen(pass)+1);
 187   strcpy (fd_passwd, pass);
 188 }
 189
 190
 191 void
 192 read_passphrase_from_fd( int fd )
 193 {
 194   int i, len;
 195   char *pw;
 196
 197   if ( !opt.batch )
 198     { /* Not used but we have to do a dummy read, so that it won't end
 199          up at the begin of the message if the quite usual trick to
 200          prepend the passphtrase to the message is used. */
 201       char buf[1];
 202
 203       while (!(read (fd, buf, 1) != 1 || *buf == '\n' ))
 204         ;
 205       *buf = 0;
 206       return;
 207     }
 208
 209   for (pw = NULL, i = len = 100; ; i++ )
 210     {
 211       if (i >= len-1 )
 212         {
 213           char *pw2 = pw;
 214           len += 100;
 215           pw = xmalloc_secure( len );
 216           if( pw2 )
 217             {
 218               memcpy(pw, pw2, i );
 219               xfree (pw2);
 220             }
 221           else
 222             i=0;
 223         }
 224       if (read( fd, pw+i, 1) != 1 || pw[i] == '\n' )
 225         break;
 226     }
 227   pw[i] = 0;
 228   if (!opt.batch)
 229     tty_printf("\b\b\b   \n" );
 230
 231   xfree ( fd_passwd );
 232   fd_passwd = pw;
 233 }
 234
 235
 236 /*
 237  * Ask the GPG Agent for the passphrase.
 238  * Mode 0:  Allow cached passphrase
 239  *      1:  No cached passphrase FIXME: Not really implemented
 240  *
 241  * Note that TRYAGAIN_TEXT must not be translated.  If CANCELED is not
 242  * NULL, the function does set it to 1 if the user canceled the
 243  * operation.  If CACHEID is not NULL, it will be used as the cacheID
 244  * for the gpg-agent; if is NULL and a key fingerprint can be
 245  * computed, this will be used as the cacheid.
 246  */
 247 static char *
 248 passphrase_get ( u32 *keyid, int mode, const char *cacheid, int repeat,
 249                  const char *tryagain_text,
 250                  const char *custom_description,
 251                  const char *custom_prompt, int *canceled)
 252 {
 253   int rc;
 254   char *atext = NULL;
 255   char *pw = NULL;
 256   PKT_public_key *pk = xmalloc_clear( sizeof *pk );
 257   byte fpr[MAX_FINGERPRINT_LEN];
 258   int have_fpr = 0;
 259   char *orig_codeset;
 260   char *my_prompt;
 261   char hexfprbuf[20*2+1];
 262   const char *my_cacheid;
 263
 264   if (canceled)
 265     *canceled = 0;
 266
 267 #if MAX_FINGERPRINT_LEN < 20
 268 #error agent needs a 20 byte fingerprint
 269 #endif
 270
 271   memset (fpr, 0, MAX_FINGERPRINT_LEN );
 272   if( keyid && get_pubkey( pk, keyid ) )
 273     {
 274       if (pk)
 275         free_public_key( pk );
 276       pk = NULL; /* oops: no key for some reason */
 277     }
 278
 279   orig_codeset = i18n_switchto_utf8 ();
 280
 281   if (custom_description)
 282     atext = native_to_utf8 (custom_description);
 283   else if ( !mode && pk && keyid )
 284     {
 285       char *uid;
 286       size_t uidlen;
 287       const char *algo_name = gcry_pk_algo_name ( pk->pubkey_algo );
 288       const char *timestr;
 289       char *maink;
 290
 291       if ( !algo_name )
 292         algo_name = "?";
 293
 294 #define KEYIDSTRING _(" (main key ID %s)")
 295
 296       maink = xmalloc ( strlen (KEYIDSTRING) + keystrlen() + 20 );
 297       if( keyid[2] && keyid[3] && keyid[0] != keyid[2]
 298           && keyid[1] != keyid[3] )
 299         sprintf( maink, KEYIDSTRING, keystr(&keyid[2]) );
 300       else
 301         *maink = 0;
 302
 303       uid = get_user_id ( keyid, &uidlen );
 304       timestr = strtimestamp (pk->timestamp);
 305
 306 #undef KEYIDSTRING
 307
 308 #define PROMPTSTRING _("Please enter the passphrase to unlock the" \
 309                        " secret key for the OpenPGP certificate:\n" \
 310                        "\"%.*s\"\n" \
 311                        "%u-bit %s key, ID %s,\n" \
 312                        "created %s%s.\n" )
 313
 314       atext = xmalloc ( 100 + strlen (PROMPTSTRING)
 315                         + uidlen + 15 + strlen(algo_name) + keystrlen()
 316                         + strlen (timestr) + strlen (maink) );
 317       sprintf (atext, PROMPTSTRING,
 318                (int)uidlen, uid,
 319                nbits_from_pk (pk), algo_name, keystr(&keyid[0]), timestr,
 320                maink  );
 321       xfree (uid);
 322       xfree (maink);
 323
 324 #undef PROMPTSTRING
 325
 326       {
 327         size_t dummy;
 328         fingerprint_from_pk( pk, fpr, &dummy );
 329         have_fpr = 1;
 330       }
 331
 332     }
 333   else
 334     atext = xstrdup ( _("Enter passphrase\n") );
 335
 336
 337   if (!mode && cacheid)
 338     my_cacheid = cacheid;
 339   else if (!mode && have_fpr)
 340     my_cacheid = bin2hex (fpr, 20, hexfprbuf);
 341   else
 342     my_cacheid = NULL;
 343
 344   if (tryagain_text)
 345     tryagain_text = _(tryagain_text);
 346
 347   my_prompt = custom_prompt ? native_to_utf8 (custom_prompt): NULL;
 348
 349   rc = agent_get_passphrase (my_cacheid, tryagain_text, my_prompt, atext,
 350                              repeat, &pw);
 351
 352   xfree (my_prompt);
 353   xfree (atext); atext = NULL;
 354
 355   i18n_switchback (orig_codeset);
 356
 357
 358   if (!rc)
 359     ;
 360   else if ( gpg_err_code (rc) == GPG_ERR_CANCELED )
 361     {
 362       log_info (_("cancelled by user\n") );
 363       if (canceled)
 364         *canceled = 1;
 365     }
 366   else
 367     {
 368       log_error (_("problem with the agent: %s\n"), gpg_strerror (rc));
 369       /* Due to limitations in the API of the upper layers they
 370          consider an error as no passphrase entered.  This works in
 371          most cases but not during key creation where this should
 372          definitely not happen and let it continue without requiring a
 373          passphrase.  Given that now all the upper layers handle a
 374          cancel correctly, we simply set the cancel flag now for all
 375          errors from the agent.  */
 376       if (canceled)
 377         *canceled = 1;
 378
 379       write_status_error ("get_passphrase", rc);
 380     }
 381
 382   if (pk)
 383     free_public_key( pk );
 384   if (rc)
 385     {
 386       xfree (pw);
 387       return NULL;
 388     }
 389   return pw;
 390 }
 391
 392
 393 /*
 394  * Clear the cached passphrase.  If CACHEID is not NULL, it will be
 395  * used instead of a cache ID derived from KEYID.
 396  */
 397 void
 398 passphrase_clear_cache ( u32 *keyid, const char *cacheid, int algo )
 399 {
 400   int rc;
 401
 402   (void)algo;
 403
 404   if (!cacheid)
 405     {
 406       PKT_public_key *pk;
 407 #     if MAX_FINGERPRINT_LEN < 20
 408 #       error agent needs a 20 byte fingerprint
 409 #     endif
 410       byte fpr[MAX_FINGERPRINT_LEN];
 411       char hexfprbuf[2*20+1];
 412       size_t dummy;
 413
 414       pk = xcalloc (1, sizeof *pk);
 415       if ( !keyid || get_pubkey( pk, keyid ) )
 416         {
 417           log_error ("key not found in passphrase_clear_cache\n");
 418           free_public_key (pk);
 419           return;
 420         }
 421       memset (fpr, 0, MAX_FINGERPRINT_LEN );
 422       fingerprint_from_pk ( pk, fpr, &dummy );
 423       bin2hex (fpr, 20, hexfprbuf);
 424       rc = agent_clear_passphrase (hexfprbuf);
 425       free_public_key ( pk );
 426     }
 427   else
 428     rc = agent_clear_passphrase (cacheid);
 429
 430   if (rc)
 431     log_error (_("problem with the agent: %s\n"), gpg_strerror (rc));
 432 }
 433
 434
 435 /****************
 436  * Ask for a passphrase and return that string.
 437  */
 438 char *
 439 ask_passphrase (const char *description,
 440                 const char *tryagain_text,
 441                 const char *promptid,
 442                 const char *prompt,
 443                 const char *cacheid, int *canceled)
 444 {
 445   char *pw = NULL;
 446
 447   (void)promptid;
 448
 449   if (canceled)
 450     *canceled = 0;
 451
 452   if (!opt.batch && description)
 453     {
 454       if (strchr (description, '%'))
 455         {
 456           char *tmp = percent_plus_unescape (description, 0xff);
 457           if (!tmp)
 458             log_fatal(_("out of core\n"));
 459           tty_printf ("\n%s\n", tmp);
 460           xfree (tmp);
 461         }
 462       else
 463         tty_printf ("\n%s\n",description);
 464     }
 465
 466   if (have_static_passphrase ())
 467     {
 468       pw = xmalloc_secure (strlen(fd_passwd)+1);
 469       strcpy (pw, fd_passwd);
 470     }
 471   else
 472     pw = passphrase_get (NULL, 0, cacheid, 0,
 473                          tryagain_text, description, prompt,
 474                          canceled );
 475
 476   if (!pw || !*pw)
 477     write_status( STATUS_MISSING_PASSPHRASE );
 478
 479   return pw;
 480 }
 481
 482
 483 /* Return a new DEK object Using the string-to-key sepcifier S2K.  Use
 484    KEYID and PUBKEY_ALGO to prompt the user.  Returns NULL is the user
 485    selected to cancel the passphrase entry and if CANCELED is not
 486    NULL, sets it to true.
 487
 488    MODE 0:  Allow cached passphrase
 489         1:  Ignore cached passphrase
 490         2:  Ditto, but change the text to "repeat entry"
 491 */
 492 DEK *
 493 passphrase_to_dek (u32 *keyid, int pubkey_algo,
 494                    int cipher_algo, STRING2KEY *s2k, int mode,
 495                    const char *tryagain_text, int *canceled)
 496 {
 497   char *pw = NULL;
 498   DEK *dek;
 499   STRING2KEY help_s2k;
 500   int dummy_canceled;
 501
 502   if (!canceled)
 503     canceled = &dummy_canceled;
 504   *canceled = 0;
 505
 506   if ( !s2k )
 507     {
 508       /* This is used for the old rfc1991 mode
 509        * Note: This must match the code in encode.c with opt.rfc1991 set */
 510       s2k = &help_s2k;
 511       s2k->mode = 0;
 512       s2k->hash_algo = S2K_DIGEST_ALGO;
 513     }
 514
 515   /* If we do not have a passphrase available in NEXT_PW and status
 516      information are request, we print them now. */
 517   if ( !next_pw && is_status_enabled() )
 518     {
 519       char buf[50];
 520
 521       if ( keyid )
 522         {
 523           u32 used_kid[2];
 524           char *us;
 525
 526           if ( keyid[2] && keyid[3] )
 527             {
 528               used_kid[0] = keyid[2];
 529               used_kid[1] = keyid[3];
 530             }
 531           else
 532             {
 533               used_kid[0] = keyid[0];
 534               used_kid[1] = keyid[1];
 535             }
 536
 537           us = get_long_user_id_string ( keyid );
 538           write_status_text ( STATUS_USERID_HINT, us );
 539           xfree(us);
 540
 541           snprintf (buf, sizeof buf -1, "%08lX%08lX %08lX%08lX %d 0",
 542                     (ulong)keyid[0], (ulong)keyid[1],
 543                     (ulong)used_kid[0], (ulong)used_kid[1],
 544                     pubkey_algo );
 545
 546           write_status_text ( STATUS_NEED_PASSPHRASE, buf );
 547         }
 548       else
 549         {
 550           snprintf (buf, sizeof buf -1, "%d %d %d",
 551                     cipher_algo, s2k->mode, s2k->hash_algo );
 552           write_status_text ( STATUS_NEED_PASSPHRASE_SYM, buf );
 553         }
 554     }
 555
 556   /* If we do have a keyID, we do not have a passphrase available in
 557      NEXT_PW, we are not running in batch mode and we do not want to
 558      ignore the passphrase cache (mode!=1), print a prompt with
 559      information on that key. */
 560   if ( keyid && !opt.batch && !next_pw && mode!=1 )
 561     {
 562       PKT_public_key *pk = xmalloc_clear( sizeof *pk );
 563       char *p;
 564
 565       p = get_user_id_native(keyid);
 566       tty_printf ("\n");
 567       tty_printf (_("You need a passphrase to unlock the secret key for\n"
 568                     "user: \"%s\"\n"),p);
 569       xfree(p);
 570
 571       if ( !get_pubkey( pk, keyid ) )
 572         {
 573           const char *s = gcry_pk_algo_name ( pk->pubkey_algo );
 574
 575           tty_printf (_("%u-bit %s key, ID %s, created %s"),
 576                       nbits_from_pk( pk ), s?s:"?", keystr(keyid),
 577                       strtimestamp(pk->timestamp) );
 578           if ( keyid[2] && keyid[3]
 579                && keyid[0] != keyid[2] && keyid[1] != keyid[3] )
 580             {
 581               if ( keystrlen () > 10 )
 582                 {
 583                   tty_printf ("\n");
 584                   tty_printf (_("         (subkey on main key ID %s)"),
 585                               keystr(&keyid[2]) );
 586                 }
 587               else
 588                 tty_printf ( _(" (main key ID %s)"), keystr(&keyid[2]) );
 589             }
 590           tty_printf("\n");
 591         }
 592
 593       tty_printf("\n");
 594       if (pk)
 595         free_public_key( pk );
 596     }
 597
 598   if ( next_pw )
 599     {
 600       /* Simply return the passphrase we already have in NEXT_PW. */
 601       pw = next_pw;
 602       next_pw = NULL;
 603     }
 604   else if ( have_static_passphrase () )
 605     {
 606       /* Return the passphrase we have stored in FD_PASSWD. */
 607       pw = xmalloc_secure ( strlen(fd_passwd)+1 );
 608       strcpy ( pw, fd_passwd );
 609     }
 610   else
 611     {
 612       /* Divert to the gpg-agent. */
 613       pw = passphrase_get ( keyid, mode == 2, NULL,
 614                             mode == 2? opt.passwd_repeat: 0,
 615                             tryagain_text, NULL, NULL, canceled );
 616       if (*canceled)
 617         {
 618           xfree (pw);
 619           write_status( STATUS_MISSING_PASSPHRASE );
 620           return NULL;
 621         }
 622     }
 623
 624   if ( !pw || !*pw )
 625     write_status( STATUS_MISSING_PASSPHRASE );
 626
 627   /* Hash the passphrase and store it in a newly allocated DEK object.
 628      Keep a copy of the passphrase in LAST_PW for use by
 629      get_last_passphrase(). */
 630   dek = xmalloc_secure_clear ( sizeof *dek );
 631   dek->algo = cipher_algo;
 632   if ( !*pw && mode == 2 )
 633     dek->keylen = 0;
 634   else
 635     hash_passphrase( dek, pw, s2k, mode==2 );
 636   xfree(last_pw);
 637   last_pw = pw;
 638   return dek;
 639 }