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 _("Please enter the passphrase to unlock the" \
 310                        " secret key for the OpenPGP certificate:\n" \
 311                        "\"%.*s\"\n" \
 312                        "%u-bit %s key, ID %s,\n" \
 313                        "created %s%s.\n" )
 314
 315       atext = xmalloc ( 100 + strlen (PROMPTSTRING)
 316                         + uidlen + 15 + strlen(algo_name) + keystrlen()
 317                         + strlen (timestr) + strlen (maink) );
 318       sprintf (atext, PROMPTSTRING,
 319                (int)uidlen, uid,
 320                nbits_from_pk (pk), algo_name, keystr(&keyid[0]), timestr,
 321                maink  );
 322       xfree (uid);
 323       xfree (maink);
 324
 325 #undef PROMPTSTRING
 326
 327       {
 328         size_t dummy;
 329         fingerprint_from_pk( pk, fpr, &dummy );
 330         have_fpr = 1;
 331       }
 332
 333     }
 334   else if (mode == 2 )
 335     atext = xstrdup ( _("Repeat passphrase\n") );
 336   else
 337     atext = xstrdup ( _("Enter passphrase\n") );
 338
 339
 340   if (!mode && cacheid)
 341     my_cacheid = cacheid;
 342   else if (!mode && have_fpr)
 343     my_cacheid = bin2hex (fpr, 20, hexfprbuf);
 344   else
 345     my_cacheid = NULL;
 346
 347   if (tryagain_text)
 348     tryagain_text = _(tryagain_text);
 349
 350   my_prompt = custom_prompt ? native_to_utf8 (custom_prompt): NULL;
 351
 352   rc = agent_get_passphrase (my_cacheid, tryagain_text, my_prompt, atext, &pw);
 353
 354   xfree (my_prompt);
 355   xfree (atext); atext = NULL;
 356
 357   i18n_switchback (orig_codeset);
 358
 359
 360   if (!rc)
 361     ;
 362   else if ( gpg_err_code (rc) == GPG_ERR_CANCELED )
 363     {
 364       log_info (_("cancelled by user\n") );
 365       if (canceled)
 366         *canceled = 1;
 367     }
 368   else
 369     {
 370       log_error (_("problem with the agent: %s\n"), gpg_strerror (rc));
 371       /* Due to limitations in the API of the upper layers they
 372          consider an error as no passphrase entered.  This works in
 373          most cases but not during key creation where this should
 374          definitely not happen and let it continue without requiring a
 375          passphrase.  Given that now all the upper layers handle a
 376          cancel correctly, we simply set the cancel flag now for all
 377          errors from the agent.  */
 378       if (canceled)
 379         *canceled = 1;
 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 = unescape_percent_string
 457             ((const unsigned char*)description);
 458           tty_printf ("\n%s\n", tmp);
 459           xfree (tmp);
 460         }
 461       else
 462         tty_printf ("\n%s\n",description);
 463     }
 464
 465   if (have_static_passphrase ())
 466     {
 467       pw = xmalloc_secure (strlen(fd_passwd)+1);
 468       strcpy (pw, fd_passwd);
 469     }
 470   else
 471     pw = passphrase_get (NULL, 0, cacheid,
 472                          tryagain_text, description, prompt,
 473                          canceled );
 474
 475   if (!pw || !*pw)
 476     write_status( STATUS_MISSING_PASSPHRASE );
 477
 478   return pw;
 479 }
 480
 481
 482 /* Return a new DEK object Using the string-to-key sepcifier S2K.  Use
 483    KEYID and PUBKEY_ALGO to prompt the user.  Returns NULL is the user
 484    selected to cancel the passphrase entry and if CANCELED is not
 485    NULL, sets it to true.
 486
 487    MODE 0:  Allow cached passphrase
 488         1:  Ignore cached passphrase
 489         2:  Ditto, but change the text to "repeat entry"
 490 */
 491 DEK *
 492 passphrase_to_dek (u32 *keyid, int pubkey_algo,
 493                    int cipher_algo, STRING2KEY *s2k, int mode,
 494                    const char *tryagain_text, int *canceled)
 495 {
 496   char *pw = NULL;
 497   DEK *dek;
 498   STRING2KEY help_s2k;
 499   int dummy_canceled;
 500
 501   if (!canceled)
 502     canceled = &dummy_canceled;
 503   *canceled = 0;
 504
 505   if ( !s2k )
 506     {
 507       /* This is used for the old rfc1991 mode
 508        * Note: This must match the code in encode.c with opt.rfc1991 set */
 509       s2k = &help_s2k;
 510       s2k->mode = 0;
 511       s2k->hash_algo = S2K_DIGEST_ALGO;
 512     }
 513
 514   /* If we do not have a passphrase available in NEXT_PW and status
 515      information are request, we print them now. */
 516   if ( !next_pw && is_status_enabled() )
 517     {
 518       char buf[50];
 519
 520       if ( keyid )
 521         {
 522           u32 used_kid[2];
 523           char *us;
 524
 525           if ( keyid[2] && keyid[3] )
 526             {
 527               used_kid[0] = keyid[2];
 528               used_kid[1] = keyid[3];
 529             }
 530           else
 531             {
 532               used_kid[0] = keyid[0];
 533               used_kid[1] = keyid[1];
 534             }
 535
 536           us = get_long_user_id_string ( keyid );
 537           write_status_text ( STATUS_USERID_HINT, us );
 538           xfree(us);
 539
 540           snprintf (buf, sizeof buf -1, "%08lX%08lX %08lX%08lX %d 0",
 541                     (ulong)keyid[0], (ulong)keyid[1],
 542                     (ulong)used_kid[0], (ulong)used_kid[1],
 543                     pubkey_algo );
 544
 545           write_status_text ( STATUS_NEED_PASSPHRASE, buf );
 546         }
 547       else
 548         {
 549           snprintf (buf, sizeof buf -1, "%d %d %d",
 550                     cipher_algo, s2k->mode, s2k->hash_algo );
 551           write_status_text ( STATUS_NEED_PASSPHRASE_SYM, buf );
 552         }
 553     }
 554
 555   /* If we do have a keyID, we do not have a passphrase available in
 556      NEXT_PW, we are not running in batch mode and we do not want to
 557      ignore the passphrase cache (mode!=1), print a prompt with
 558      information on that key. */
 559   if ( keyid && !opt.batch && !next_pw && mode!=1 )
 560     {
 561       PKT_public_key *pk = xmalloc_clear( sizeof *pk );
 562       char *p;
 563
 564       p = get_user_id_native(keyid);
 565       tty_printf ("\n");
 566       tty_printf (_("You need a passphrase to unlock the secret key for\n"
 567                     "user: \"%s\"\n"),p);
 568       xfree(p);
 569
 570       if ( !get_pubkey( pk, keyid ) )
 571         {
 572           const char *s = gcry_pk_algo_name ( pk->pubkey_algo );
 573
 574           tty_printf (_("%u-bit %s key, ID %s, created %s"),
 575                       nbits_from_pk( pk ), s?s:"?", keystr(keyid),
 576                       strtimestamp(pk->timestamp) );
 577           if ( keyid[2] && keyid[3]
 578                && keyid[0] != keyid[2] && keyid[1] != keyid[3] )
 579             {
 580               if ( keystrlen () > 10 )
 581                 {
 582                   tty_printf ("\n");
 583                   tty_printf (_("         (subkey on main key ID %s)"),
 584                               keystr(&keyid[2]) );
 585                 }
 586               else
 587                 tty_printf ( _(" (main key ID %s)"), keystr(&keyid[2]) );
 588             }
 589           tty_printf("\n");
 590         }
 591
 592       tty_printf("\n");
 593       if (pk)
 594         free_public_key( pk );
 595     }
 596
 597   if ( next_pw )
 598     {
 599       /* Simply return the passphrase we already have in NEXT_PW. */
 600       pw = next_pw;
 601       next_pw = NULL;
 602     }
 603   else if ( have_static_passphrase () )
 604     {
 605       /* Return the passphrase we have stored in FD_PASSWD. */
 606       pw = xmalloc_secure ( strlen(fd_passwd)+1 );
 607       strcpy ( pw, fd_passwd );
 608     }
 609   else
 610     {
 611       /* Divert to the gpg-agent. */
 612       pw = passphrase_get ( keyid, mode == 2? 1: 0, NULL,
 613                             tryagain_text, NULL, NULL, canceled );
 614       if (*canceled)
 615         {
 616           xfree (pw);
 617           write_status( STATUS_MISSING_PASSPHRASE );
 618           return NULL;
 619         }
 620       if (!pw)
 621         pw = xstrdup ("");
 622       if ( *pw && mode == 2 )
 623         {
 624           int i;
 625           for(i=0;i<opt.passwd_repeat;i++)
 626             {
 627               char *pw2 = passphrase_get ( keyid, 2, NULL, NULL, NULL,
 628                                            NULL, canceled );
 629               if (*canceled)
 630                 {
 631                   xfree (pw);
 632                   xfree (pw2);
 633                   write_status( STATUS_MISSING_PASSPHRASE );
 634                   return NULL;
 635                 }
 636               if (!pw2)
 637                 pw2 = xstrdup ("");
 638               if ( strcmp(pw, pw2) )
 639                 {
 640                   xfree(pw2);
 641                   xfree(pw);
 642                   return NULL;
 643                 }
 644               xfree(pw2);
 645             }
 646         }
 647     }
 648
 649   if ( !pw || !*pw )
 650     write_status( STATUS_MISSING_PASSPHRASE );
 651
 652   /* Hash the passphrase and store it in a newly allocated DEK object.
 653      Keep a copy of the passphrase in LAST_PW for use by
 654      get_last_passphrase(). */
 655   dek = xmalloc_secure_clear ( sizeof *dek );
 656   dek->algo = cipher_algo;
 657   if ( !*pw && mode == 2 )
 658     dek->keylen = 0;
 659   else
 660     hash_passphrase( dek, pw, s2k, mode==2 );
 661   xfree(last_pw);
 662   last_pw = pw;
 663   return dek;
 664 }