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  *      2:  Ditto, but change the text to "repeat entry"
 241  *
 242  * Note that TRYAGAIN_TEXT must not be translated.  If CANCELED is not
 243  * NULL, the function does set it to 1 if the user canceled the
 244  * operation.  If CACHEID is not NULL, it will be used as the cacheID
 245  * for the gpg-agent; if is NULL and a key fingerprint can be
 246  * computed, this will be used as the cacheid.
 247  */
 248 static char *
 249 passphrase_get ( u32 *keyid, int mode, const char *cacheid,
 250                  const char *tryagain_text,
 251                  const char *custom_description,
 252                  const char *custom_prompt, int *canceled)
 253 {
 254   int rc;
 255   char *atext = NULL;
 256   char *pw = NULL;
 257   PKT_public_key *pk = xmalloc_clear( sizeof *pk );
 258   byte fpr[MAX_FINGERPRINT_LEN];
 259   int have_fpr = 0;
 260   char *orig_codeset;
 261   char *my_prompt;
 262   char hexfprbuf[20*2+1];
 263   const char *my_cacheid;
 264
 265   if (canceled)
 266     *canceled = 0;
 267
 268 #if MAX_FINGERPRINT_LEN < 20
 269 #error agent needs a 20 byte fingerprint
 270 #endif
 271
 272   memset (fpr, 0, MAX_FINGERPRINT_LEN );
 273   if( keyid && get_pubkey( pk, keyid ) )
 274     {
 275       if (pk)
 276         free_public_key( pk );
 277       pk = NULL; /* oops: no key for some reason */
 278     }
 279
 280   orig_codeset = i18n_switchto_utf8 ();
 281
 282   if (custom_description)
 283     atext = native_to_utf8 (custom_description);
 284   else if ( !mode && pk && keyid )
 285     {
 286       char *uid;
 287       size_t uidlen;
 288       const char *algo_name = gcry_pk_algo_name ( pk->pubkey_algo );
 289       const char *timestr;
 290       char *maink;
 291
 292       if ( !algo_name )
 293         algo_name = "?";
 294
 295 #define KEYIDSTRING _(" (main key ID %s)")
 296
 297       maink = xmalloc ( strlen (KEYIDSTRING) + keystrlen() + 20 );
 298       if( keyid[2] && keyid[3] && keyid[0] != keyid[2]
 299           && keyid[1] != keyid[3] )
 300         sprintf( maink, KEYIDSTRING, keystr(&keyid[2]) );
 301       else
 302         *maink = 0;
 303
 304       uid = get_user_id ( keyid, &uidlen );
 305       timestr = strtimestamp (pk->timestamp);
 306
 307 #undef KEYIDSTRING
 308
 309 #define PROMPTSTRING _("You need a passphrase to unlock the secret" \
 310                        " key for user:\n" \
 311                        "\"%.*s\"\n" \
 312                        "%u-bit %s key, ID %s, 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 if (mode == 2 )
 334     atext = xstrdup ( _("Repeat passphrase\n") );
 335   else
 336     atext = xstrdup ( _("Enter passphrase\n") );
 337
 338
 339   if (!mode && cacheid)
 340     my_cacheid = cacheid;
 341   else if (!mode && have_fpr)
 342     my_cacheid = bin2hex (fpr, 20, hexfprbuf);
 343   else
 344     my_cacheid = NULL;
 345
 346   if (tryagain_text)
 347     tryagain_text = _(tryagain_text);
 348
 349   my_prompt = custom_prompt ? native_to_utf8 (custom_prompt): NULL;
 350
 351   rc = agent_get_passphrase (my_cacheid, tryagain_text, my_prompt, atext, &pw);
 352
 353   xfree (my_prompt);
 354   xfree (atext); atext = NULL;
 355
 356   i18n_switchback (orig_codeset);
 357
 358
 359   if (!rc)
 360     ;
 361   else if ( gpg_err_code (rc) == GPG_ERR_CANCELED )
 362     {
 363       log_info (_("cancelled by user\n") );
 364       if (canceled)
 365         *canceled = 1;
 366     }
 367   else
 368     {
 369       log_error (_("problem with the agent: %s\n"), gpg_strerror (rc));
 370       /* Due to limitations in the API of the upper layers they
 371          consider an error as no passphrase entered.  This works in
 372          most cases but not during key creation where this should
 373          definitely not happen and let it continue without requiring a
 374          passphrase.  Given that now all the upper layers handle a
 375          cancel correctly, we simply set the cancel flag now for all
 376          errors from the agent.  */
 377       if (canceled)
 378         *canceled = 1;
 379     }
 380
 381   if (pk)
 382     free_public_key( pk );
 383   if (rc)
 384     {
 385       xfree (pw);
 386       return NULL;
 387     }
 388   return pw;
 389 }
 390
 391
 392 /*
 393  * Clear the cached passphrase.  If CACHEID is not NULL, it will be
 394  * used instead of a cache ID derived from KEYID.
 395  */
 396 void
 397 passphrase_clear_cache ( u32 *keyid, const char *cacheid, int algo )
 398 {
 399   int rc;
 400
 401   if (!cacheid)
 402     {
 403       PKT_public_key *pk;
 404 #     if MAX_FINGERPRINT_LEN < 20
 405 #       error agent needs a 20 byte fingerprint
 406 #     endif
 407       byte fpr[MAX_FINGERPRINT_LEN];
 408       char hexfprbuf[2*20+1];
 409       size_t dummy;
 410
 411       pk = xcalloc (1, sizeof *pk);
 412       if ( !keyid || get_pubkey( pk, keyid ) )
 413         {
 414           log_error ("key not found in passphrase_clear_cache\n");
 415           free_public_key (pk);
 416           return;
 417         }
 418       memset (fpr, 0, MAX_FINGERPRINT_LEN );
 419       fingerprint_from_pk ( pk, fpr, &dummy );
 420       bin2hex (fpr, 20, hexfprbuf);
 421       rc = agent_clear_passphrase (hexfprbuf);
 422       free_public_key ( pk );
 423     }
 424   else
 425     rc = agent_clear_passphrase (cacheid);
 426
 427   if (rc)
 428     log_error (_("problem with the agent: %s\n"), gpg_strerror (rc));
 429 }
 430
 431
 432 /****************
 433  * Ask for a passphrase and return that string.
 434  */
 435 char *
 436 ask_passphrase (const char *description,
 437                 const char *tryagain_text,
 438                 const char *promptid,
 439                 const char *prompt,
 440                 const char *cacheid, int *canceled)
 441 {
 442   char *pw = NULL;
 443
 444   if (canceled)
 445     *canceled = 0;
 446
 447   if (!opt.batch && description)
 448     {
 449       if (strchr (description, '%'))
 450         {
 451           char *tmp = unescape_percent_string (description);
 452           tty_printf ("\n%s\n", tmp);
 453           xfree (tmp);
 454         }
 455       else
 456         tty_printf ("\n%s\n",description);
 457     }
 458
 459   if (have_static_passphrase ())
 460     {
 461       pw = xmalloc_secure (strlen(fd_passwd)+1);
 462       strcpy (pw, fd_passwd);
 463     }
 464   else
 465     pw = passphrase_get (NULL, 0, cacheid,
 466                          tryagain_text, description, prompt,
 467                          canceled );
 468
 469   if (!pw || !*pw)
 470     write_status( STATUS_MISSING_PASSPHRASE );
 471
 472   return pw;
 473 }
 474
 475
 476 /* Return a new DEK object Using the string-to-key sepcifier S2K.  Use
 477    KEYID and PUBKEY_ALGO to prompt the user.  Returns NULL is the user
 478    selected to cancel the passphrase entry and if CANCELED is not
 479    NULL, sets it to true.
 480
 481    MODE 0:  Allow cached passphrase
 482         1:  Ignore cached passphrase
 483         2:  Ditto, but change the text to "repeat entry"
 484 */
 485 DEK *
 486 passphrase_to_dek (u32 *keyid, int pubkey_algo,
 487                    int cipher_algo, STRING2KEY *s2k, int mode,
 488                    const char *tryagain_text, int *canceled)
 489 {
 490   char *pw = NULL;
 491   DEK *dek;
 492   STRING2KEY help_s2k;
 493   int dummy_canceled;
 494
 495   if (!canceled)
 496     canceled = &dummy_canceled;
 497   *canceled = 0;
 498
 499   if ( !s2k )
 500     {
 501       /* This is used for the old rfc1991 mode
 502        * Note: This must match the code in encode.c with opt.rfc1991 set */
 503       s2k = &help_s2k;
 504       s2k->mode = 0;
 505       s2k->hash_algo = S2K_DIGEST_ALGO;
 506     }
 507
 508   /* If we do not have a passphrase available in NEXT_PW and status
 509      information are request, we print them now. */
 510   if ( !next_pw && is_status_enabled() )
 511     {
 512       char buf[50];
 513
 514       if ( keyid )
 515         {
 516           u32 used_kid[2];
 517           char *us;
 518
 519           if ( keyid[2] && keyid[3] )
 520             {
 521               used_kid[0] = keyid[2];
 522               used_kid[1] = keyid[3];
 523             }
 524           else
 525             {
 526               used_kid[0] = keyid[0];
 527               used_kid[1] = keyid[1];
 528             }
 529
 530           us = get_long_user_id_string ( keyid );
 531           write_status_text ( STATUS_USERID_HINT, us );
 532           xfree(us);
 533
 534           snprintf (buf, sizeof buf -1, "%08lX%08lX %08lX%08lX %d 0",
 535                     (ulong)keyid[0], (ulong)keyid[1],
 536                     (ulong)used_kid[0], (ulong)used_kid[1],
 537                     pubkey_algo );
 538
 539           write_status_text ( STATUS_NEED_PASSPHRASE, buf );
 540         }
 541       else
 542         {
 543           snprintf (buf, sizeof buf -1, "%d %d %d",
 544                     cipher_algo, s2k->mode, s2k->hash_algo );
 545           write_status_text ( STATUS_NEED_PASSPHRASE_SYM, buf );
 546         }
 547     }
 548
 549   /* If we do have a keyID, we do not have a passphrase available in
 550      NEXT_PW, we are not running in batch mode and we do not want to
 551      ignore the passphrase cache (mode!=1), print a prompt with
 552      information on that key. */
 553   if ( keyid && !opt.batch && !next_pw && mode!=1 )
 554     {
 555       PKT_public_key *pk = xmalloc_clear( sizeof *pk );
 556       char *p;
 557
 558       p = get_user_id_native(keyid);
 559       tty_printf ("\n");
 560       tty_printf (_("You need a passphrase to unlock the secret key for\n"
 561                     "user: \"%s\"\n"),p);
 562       xfree(p);
 563
 564       if ( !get_pubkey( pk, keyid ) )
 565         {
 566           const char *s = gcry_pk_algo_name ( pk->pubkey_algo );
 567
 568           tty_printf (_("%u-bit %s key, ID %s, created %s"),
 569                       nbits_from_pk( pk ), s?s:"?", keystr(keyid),
 570                       strtimestamp(pk->timestamp) );
 571           if ( keyid[2] && keyid[3]
 572                && keyid[0] != keyid[2] && keyid[1] != keyid[3] )
 573             {
 574               if ( keystrlen () > 10 )
 575                 {
 576                   tty_printf ("\n");
 577                   tty_printf (_("         (subkey on main key ID %s)"),
 578                               keystr(&keyid[2]) );
 579                 }
 580               else
 581                 tty_printf ( _(" (main key ID %s)"), keystr(&keyid[2]) );
 582             }
 583           tty_printf("\n");
 584         }
 585
 586       tty_printf("\n");
 587       if (pk)
 588         free_public_key( pk );
 589     }
 590
 591   if ( next_pw )
 592     {
 593       /* Simply return the passphrase we already have in NEXT_PW. */
 594       pw = next_pw;
 595       next_pw = NULL;
 596     }
 597   else if ( have_static_passphrase () )
 598     {
 599       /* Return the passphrase we have stored in FD_PASSWD. */
 600       pw = xmalloc_secure ( strlen(fd_passwd)+1 );
 601       strcpy ( pw, fd_passwd );
 602     }
 603   else
 604     {
 605       /* Divert to the gpg-agent. */
 606       pw = passphrase_get ( keyid, mode == 2? 1: 0, NULL,
 607                             tryagain_text, NULL, NULL, canceled );
 608       if (*canceled)
 609         {
 610           xfree (pw);
 611           write_status( STATUS_MISSING_PASSPHRASE );
 612           return NULL;
 613         }
 614       if (!pw)
 615         pw = xstrdup ("");
 616       if ( *pw && mode == 2 )
 617         {
 618           int i;
 619           for(i=0;i<opt.passwd_repeat;i++)
 620             {
 621               char *pw2 = passphrase_get ( keyid, 2, NULL, NULL, NULL,
 622                                            NULL, canceled );
 623               if (*canceled)
 624                 {
 625                   xfree (pw);
 626                   xfree (pw2);
 627                   write_status( STATUS_MISSING_PASSPHRASE );
 628                   return NULL;
 629                 }
 630               if (!pw2)
 631                 pw2 = xstrdup ("");
 632               if ( strcmp(pw, pw2) )
 633                 {
 634                   xfree(pw2);
 635                   xfree(pw);
 636                   return NULL;
 637                 }
 638               xfree(pw2);
 639             }
 640         }
 641     }
 642
 643   if ( !pw || !*pw )
 644     write_status( STATUS_MISSING_PASSPHRASE );
 645
 646   /* Hash the passphrase and store it in a newly allocated DEK object.
 647      Keep a copy of the passphrase in LAST_PW for use by
 648      get_last_passphrase(). */
 649   dek = xmalloc_secure_clear ( sizeof *dek );
 650   dek->algo = cipher_algo;
 651   if ( !*pw && mode == 2 )
 652     dek->keylen = 0;
 653   else
 654     hash_passphrase( dek, pw, s2k, mode==2 );
 655   xfree(last_pw);
 656   last_pw = pw;
 657   return dek;
 658 }