mdw@git.distorted.org.uk Git - tripe/blob - keymgmt.c

   1 /* -*-c-*-
   2  *
   3  * $Id$
   4  *
   5  * Key loading and storing
   6  *
   7  * (c) 2001 Straylight/Edgeware
   8  */
   9
  10 /*----- Licensing notice --------------------------------------------------*
  11  *
  12  * This file is part of Trivial IP Encryption (TrIPE).
  13  *
  14  * TrIPE is free software; you can redistribute it and/or modify
  15  * it under the terms of the GNU General Public License as published by
  16  * the Free Software Foundation; either version 2 of the License, or
  17  * (at your option) any later version.
  18  *
  19  * TrIPE is distributed in the hope that it will be useful,
  20  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  21  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  22  * GNU General Public License for more details.
  23  *
  24  * You should have received a copy of the GNU General Public License
  25  * along with TrIPE; if not, write to the Free Software Foundation,
  26  * Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  27  */
  28
  29 /*----- Header files ------------------------------------------------------*/
  30
  31 #include "tripe.h"
  32
  33 /*----- Global variables --------------------------------------------------*/
  34
  35 group *gg;
  36 mp *kpriv;
  37 ge *kpub;
  38 algswitch algs;
  39 size_t indexsz;
  40
  41 /*----- Static variables --------------------------------------------------*/
  42
  43 static key_file *kf_pub;
  44 static const char *kr_priv, *kr_pub, *tag_priv;
  45 static fwatch w_priv, w_pub;
  46
  47 /*----- Key groups --------------------------------------------------------*/
  48
  49 typedef struct kgops {
  50   const char *ty;
  51   const char *(*loadpriv)(key_data *, group **, mp **, dstr *);
  52   const char *(*loadpub)(key_data *, group **, ge **, dstr *);
  53 } kgops;
  54
  55 /* --- Diffie-Hellman --- */
  56
  57 static const char *kgdh_priv(key_data *kd, group **g, mp **x, dstr *t)
  58 {
  59   key_packstruct kps[DH_PRIVFETCHSZ];
  60   key_packdef *kp;
  61   dh_priv dp;
  62   const char *e;
  63   int rc;
  64
  65   kp = key_fetchinit(dh_privfetch, kps, &dp);
  66   if ((rc = key_unpack(kp, kd, t)) != 0) {
  67     e = key_strerror(rc);
  68     goto done;
  69   }
  70   *g = group_prime(&dp.dp);
  71   *x = MP_COPY(dp.x);
  72   e = 0;
  73 done:
  74   key_fetchdone(kp);
  75   return (e);
  76 }
  77
  78 static const char *kgdh_pub(key_data *kd, group **g, ge **p, dstr *t)
  79 {
  80   key_packstruct kps[DH_PUBFETCHSZ];
  81   key_packdef *kp;
  82   dh_pub dp;
  83   const char *e;
  84   int rc;
  85
  86   kp = key_fetchinit(dh_pubfetch, kps, &dp);
  87   if ((rc = key_unpack(kp, kd, t)) != 0) {
  88     e = key_strerror(rc);
  89     goto done;
  90   }
  91   *g = group_prime(&dp.dp);
  92   *p = G_CREATE(*g);
  93   if (G_FROMINT(*g, *p, dp.y)) {
  94     e = "bad public value";
  95     goto done;
  96   }
  97   e = 0;
  98 done:
  99   key_fetchdone(kp);
 100   return (e);
 101 }
 102
 103 static const kgops kgdh_ops = { "tripe-dh", kgdh_priv, kgdh_pub };
 104
 105 /* --- Elliptic curve --- */
 106
 107 static const char *kgec_priv(key_data *kd, group **g, mp **x, dstr *t)
 108 {
 109   key_packstruct kps[EC_PRIVFETCHSZ];
 110   key_packdef *kp;
 111   ec_priv ep;
 112   ec_info ei;
 113   const char *e;
 114   int rc;
 115
 116   kp = key_fetchinit(ec_privfetch, kps, &ep);
 117   if ((rc = key_unpack(kp, kd, t)) != 0) {
 118     e = key_strerror(rc);
 119     goto done;
 120   }
 121   if ((e = ec_getinfo(&ei, ep.cstr)) != 0)
 122     goto done;
 123   *g = group_ec(&ei);
 124   *x = MP_COPY(ep.x);
 125   e = 0;
 126 done:
 127   key_fetchdone(kp);
 128   return (e);
 129 }
 130
 131 static const char *kgec_pub(key_data *kd, group **g, ge **p, dstr *t)
 132 {
 133   key_packstruct kps[EC_PUBFETCHSZ];
 134   key_packdef *kp;
 135   ec_pub ep;
 136   ec_info ei;
 137   const char *e;
 138   int rc;
 139
 140   kp = key_fetchinit(ec_pubfetch, kps, &ep);
 141   if ((rc = key_unpack(kp, kd, t)) != 0) {
 142     e = key_strerror(rc);
 143     goto done;
 144   }
 145   if ((e = ec_getinfo(&ei, ep.cstr)) != 0)
 146     goto done;
 147   *g = group_ec(&ei);
 148   *p = G_CREATE(*g);
 149   if (G_FROMEC(*g, *p, &ep.p)) {
 150     e = "bad public point";
 151     goto done;
 152   }
 153   e = 0;
 154 done:
 155   key_fetchdone(kp);
 156   return (e);
 157 }
 158
 159 static const kgops kgec_ops = { "tripe-ec", kgec_priv, kgec_pub };
 160
 161 /* --- Table of supported key types --- */
 162
 163 static const kgops *kgtab[] = { &kgdh_ops, &kgec_ops, 0 };
 164
 165 /*----- Algswitch stuff ---------------------------------------------------*/
 166
 167 /* --- @algs_get@ --- *
 168  *
 169  * Arguments:   @algswitch *a@ = where to put the algorithms
 170  *              @key_file *kf@ = key file (for some stupid reason)
 171  *              @key *k@ = key to inspect
 172  *
 173  * Returns:     Null if OK, or an error message.
 174  *
 175  * Use:         Extracts an algorithm choice from a key.
 176  */
 177
 178 static const char *algs_get(algswitch *a, key_file *kf, key *k)
 179 {
 180   const char *p;
 181   char *q;
 182   dstr d = DSTR_INIT;
 183   const char *e;
 184
 185 #define FAIL(msg) do { e = msg; goto done; } while (0)
 186
 187   if ((p = key_getattr(kf, k, "cipher")) == 0)
 188     p = "blowfish-cbc";
 189   if ((a->c = gcipher_byname(p)) == 0)
 190     FAIL("unknown-cipher");
 191
 192   if ((p = key_getattr(kf, k, "hash")) == 0)
 193     p = "rmd160";
 194   if ((a->h = ghash_byname(p)) == 0)
 195     FAIL("unknown-hash");
 196
 197   if ((p = key_getattr(kf, k, "mgf")) == 0) {
 198     dstr_reset(&d);
 199     dstr_putf(&d, "%s-mgf", a->h->name);
 200     p = d.buf;
 201   }
 202   if ((a->mgf = gcipher_byname(p)) == 0)
 203     FAIL("unknown-mgf-cipher");
 204
 205   if ((p = key_getattr(kf, k, "mac")) != 0) {
 206     dstr_reset(&d);
 207     dstr_puts(&d, p);
 208     if ((q = strchr(d.buf, '/')) != 0)
 209       *q++ = 0;
 210     if ((a->m = gmac_byname(d.buf)) == 0)
 211       FAIL("unknown-mac");
 212     if (!q)
 213       a->tagsz = a->m->hashsz;
 214     else {
 215       unsigned long n = strtoul(q, &q, 0);
 216       if (*q) FAIL("bad-tag-length-string");
 217       if (n%8 || n > ~(size_t)0) FAIL("bad-tag-length");
 218       a->tagsz = n/8;
 219     }
 220   } else {
 221     dstr_reset(&d);
 222     dstr_putf(&d, "%s-hmac", a->h->name);
 223     if ((a->m = gmac_byname(d.buf)) == 0)
 224       FAIL("no-hmac-for-hash");
 225     a->tagsz = a->h->hashsz/2;
 226   }
 227
 228   e = 0;
 229 done:
 230   dstr_destroy(&d);
 231   return (e);
 232 }
 233
 234 /* --- @algs_check@ --- *
 235  *
 236  * Arguments:   @algswitch *a@ = a choice of algorithms
 237  *              @const group *g@ = the group we're working in
 238  *
 239  * Returns:     Null if OK, or an error message.
 240  *
 241  * Use:         Checks an algorithm choice for sensibleness.  This also
 242  *              derives some useful information from the choices, and you
 243  *              must call this before committing the algorithm selection
 244  *              for use by @keyset@ functions.
 245  */
 246
 247 static const char *algs_check(algswitch *a, const group *g)
 248 {
 249   /* --- Derive the key sizes --- *
 250    *
 251    * Must ensure that we have non-empty keys.  This isn't ideal, but it
 252    * provides a handy sanity check.
 253    */
 254
 255   a->hashsz = a->h->hashsz;
 256   if ((a->cksz = keysz(a->hashsz, a->c->keysz)) == 0)
 257     return ("no key size found for cipher");
 258   if ((a->mksz = keysz(a->hashsz, a->m->keysz)) == 0)
 259     return ("no key size found for MAC");
 260
 261   /* --- Ensure that the tag size is sane --- */
 262
 263   if (a->tagsz > a->m->hashsz) return ("tag length too large");
 264
 265   /* --- Ensure the MGF accepts hashes as keys --- */
 266
 267   if (keysz(a->hashsz, a->mgf->keysz) != a->hashsz)
 268     return ("MGF not suitable -- restrictive key schedule");
 269
 270   /* --- All ship-shape and Bristol-fashion --- */
 271
 272   return (0);
 273 }
 274
 275 /* --- @algs_samep@ --- *
 276  *
 277  * Arguments:   @const algswitch *a, *aa@ = two algorithm selections
 278  *
 279  * Returns:     Nonzero if the two selections are the same.
 280  *
 281  * Use:         Checks sameness of algorithm selections: used to ensure that
 282  *              peers are using sensible algorithms.
 283  */
 284
 285 static int algs_samep(const algswitch *a, const algswitch *aa)
 286 {
 287   return (a->c == aa->c && a->mgf == aa->mgf && a->h == aa->h &&
 288           a->m == aa->m && a->tagsz == aa->tagsz);
 289 }
 290
 291 /*----- Main code ---------------------------------------------------------*/
 292
 293 /* --- @keymoan@ --- *
 294  *
 295  * Arguments:   @const char *file@ = name of the file
 296  *              @int line@ = line number in file
 297  *              @const char *msg@ = error message
 298  *              @void *p@ = argument pointer
 299  *
 300  * Returns:     ---
 301  *
 302  * Use:         Reports an error message about loading a key file.
 303  */
 304
 305 static void keymoan(const char *file, int line, const char *msg, void *p)
 306 {
 307   a_warn("KEYMGMT",
 308          "key-file-error",
 309          "%s:%i", file, line,
 310          "%s", msg,
 311          A_END);
 312 }
 313
 314 /* --- @loadpriv@ --- *
 315  *
 316  * Arguments:   @dstr *d@ = string to write errors in
 317  *
 318  * Returns:     Zero if OK, nonzero on error.
 319  *
 320  * Use:         Loads the private key from its keyfile.
 321  */
 322
 323 static int loadpriv(dstr *d)
 324 {
 325   key_file kf;
 326   key *k;
 327   key_data **kd;
 328   dstr t = DSTR_INIT;
 329   group *g = 0;
 330   mp *x = 0;
 331   int rc = -1;
 332   const kgops **ko;
 333   const char *e;
 334   algswitch a;
 335
 336   /* --- Open the private key file --- */
 337
 338   if (key_open(&kf, kr_priv, KOPEN_READ, keymoan, 0)) {
 339     dstr_putf(d, "error reading private keyring `%s': %s",
 340               kr_priv, strerror(errno));
 341     goto done_0;
 342   }
 343
 344   /* --- Find the private key --- */
 345
 346   if (key_qtag(&kf, tag_priv, &t, &k, &kd)) {
 347     dstr_putf(d, "private key `%s' not found in keyring `%s'",
 348               tag_priv, kr_priv);
 349     goto done_1;
 350   }
 351
 352   /* --- Look up the key type in the table --- */
 353
 354   for (ko = kgtab; *ko; ko++) {
 355     if (strcmp((*ko)->ty, k->type) == 0)
 356       goto tymatch;
 357   }
 358   dstr_putf(d, "private key `%s' has unknown type `%s'", t.buf, k->type);
 359   goto done_1;
 360 tymatch:;
 361
 362   /* --- Load the key --- */
 363
 364   if ((e = (*ko)->loadpriv(*kd, &g, &x, &t)) != 0) {
 365     dstr_putf(d, "error reading private key `%s': %s", t.buf, e);
 366     goto done_1;
 367   }
 368
 369   /* --- Check that the key is sensible --- */
 370
 371   if ((e = G_CHECK(g, &rand_global)) != 0) {
 372     dstr_putf(d, "bad group in private key `%s': %s", t.buf, e);
 373     goto done_1;
 374   }
 375
 376   /* --- Collect the algorithms --- */
 377
 378   if ((e = algs_get(&a, &kf, k)) != 0 ||
 379       (e = algs_check(&a, g)) != 0) {
 380     dstr_putf(d, "bad symmetric algorithm selection in private key `%s': %s",
 381               t.buf, e);
 382     goto done_1;
 383   }
 384
 385   /* --- Good, we're happy --- *
 386    *
 387    * Dodginess!  We change the group over here, but don't free any old group
 388    * elements.  This assumes that the new group is basically the same as the
 389    * old one, and will happily adopt the existing elements.  If it isn't,
 390    * then we lose badly.  Check this, then.
 391    */
 392
 393   if (gg) {
 394     if (!group_samep(g, gg)) {
 395       dstr_putf(d, "private key `%s' has different group", t.buf);
 396       goto done_1;
 397     }
 398     G_DESTROYGROUP(gg);
 399   }
 400   if (kpriv)
 401     mp_drop(kpriv);
 402
 403   if (kpub)
 404     G_DESTROY(g, kpub);
 405   kpub = G_CREATE(g);
 406   G_EXP(g, kpub, g->g, x);
 407   indexsz = mp_octets(g->r);
 408
 409   /* --- Dump out the group --- */
 410
 411   IF_TRACING(T_KEYMGMT, {
 412     trace(T_KEYMGMT, "keymgmt: extracted private key `%s'", t.buf);
 413     IF_TRACING(T_CRYPTO, {
 414       trace(T_CRYPTO, "crypto: r = %s", mpstr(g->r));
 415       trace(T_CRYPTO, "crypto: h = %s", mpstr(g->h));
 416       trace(T_CRYPTO, "crypto: x = %s", mpstr(x));
 417       trace(T_CRYPTO, "crypto: cipher = %s", a.c->name);
 418       trace(T_CRYPTO, "crypto: mgf = %s", a.mgf->name);
 419       trace(T_CRYPTO, "crypto: hash = %s", a.h->name);
 420       trace(T_CRYPTO, "crypto: mac = %s/%lu",
 421             a.m->name, (unsigned long)a.tagsz * 8);
 422     })
 423   })
 424
 425   /* --- Success! --- */
 426
 427   gg = g; g = 0;
 428   algs = a;
 429   kpriv = x; x = 0;
 430   rc = 0;
 431
 432   /* --- Tidy up --- */
 433
 434 done_1:
 435   key_close(&kf);
 436 done_0:
 437   dstr_destroy(&t);
 438   if (x) mp_drop(x);
 439   if (g) G_DESTROYGROUP(g);
 440   return (rc);
 441 }
 442
 443 /* --- @loadpub@ --- *
 444  *
 445  * Arguments:   @dstr *d@ = string to write errors to
 446  *
 447  * Returns:     Zero if OK, nonzero on error.
 448  *
 449  * Use:         Reloads the public keyring.
 450  */
 451
 452 static int loadpub(dstr *d)
 453 {
 454   key_file *kf = CREATE(key_file);
 455
 456   if (key_open(kf, kr_pub, KOPEN_READ, keymoan, 0)) {
 457     dstr_putf(d, "error reading public keyring `%s': %s",
 458               kr_pub, strerror(errno));
 459     DESTROY(kf);
 460     return (-1);
 461   }
 462   kf_pub = kf;
 463   T( trace(T_KEYMGMT, "keymgmt: loaded public keyring `%s'", kr_pub); )
 464   return (0);
 465 }
 466
 467 /* --- @km_reload@ --- *
 468  *
 469  * Arguments:   ---
 470  *
 471  * Returns:     Zero if OK, nonzero to force reloading of keys.
 472  *
 473  * Use:         Checks the keyrings to see if they need reloading.
 474  */
 475
 476 int km_reload(void)
 477 {
 478   dstr d = DSTR_INIT;
 479   key_file *kf;
 480   int reload = 0;
 481
 482   /* --- Check the private key first --- */
 483
 484   if (fwatch_update(&w_priv, kr_priv)) {
 485     T( trace(T_KEYMGMT, "keymgmt: private keyring updated: reloading..."); )
 486     DRESET(&d);
 487     if (loadpriv(&d))
 488       a_warn("KEYMGMT", "bad-private-key", "%s", d.buf, A_END);
 489     else
 490       reload = 1;
 491   }
 492
 493   /* --- Now check the public keys --- */
 494
 495   if (fwatch_update(&w_pub, kr_pub)) {
 496     T( trace(T_KEYMGMT, "keymgmt: public keyring updated: reloading..."); )
 497     kf = kf_pub;
 498     DRESET(&d);
 499     if (loadpub(&d))
 500       a_warn("KEYMGMT", "bad-public-keyring", "%s", d.buf, A_END);
 501     else {
 502       reload = 1;
 503       key_close(kf);
 504       DESTROY(kf);
 505     }
 506   }
 507
 508   /* --- Done --- */
 509
 510   return (reload);
 511 }
 512
 513 /* --- @km_init@ --- *
 514  *
 515  * Arguments:   @const char *priv@ = private keyring file
 516  *              @const char *pub@ = public keyring file
 517  *              @const char *tag@ = tag to load
 518  *
 519  * Returns:     ---
 520  *
 521  * Use:         Initializes, and loads the private key.
 522  */
 523
 524 void km_init(const char *priv, const char *pub, const char *tag)
 525 {
 526   dstr d = DSTR_INIT;
 527   const gchash *const *hh;
 528
 529   kr_priv = priv;
 530   kr_pub = pub;
 531   tag_priv = tag;
 532   fwatch_init(&w_priv, kr_priv);
 533   fwatch_init(&w_pub, kr_pub);
 534
 535   for (hh = ghashtab; *hh; hh++) {
 536     if ((*hh)->hashsz > MAXHASHSZ) {
 537       die(EXIT_FAILURE, "INTERNAL ERROR: %s hash length %lu > MAXHASHSZ %d",
 538           (*hh)->name, (unsigned long)(*hh)->hashsz, MAXHASHSZ);
 539     }
 540   }
 541
 542   DRESET(&d);
 543   if (loadpriv(&d))
 544     die(EXIT_FAILURE, "%s", d.buf);
 545   if (loadpub(&d))
 546     die(EXIT_FAILURE, "%s", d.buf);
 547 }
 548
 549 /* --- @km_getpubkey@ --- *
 550  *
 551  * Arguments:   @const char *tag@ = public key tag to load
 552  *              @ge *kpub@ = where to put the public key
 553  *              @time_t *t_exp@ = where to put the expiry time
 554  *
 555  * Returns:     Zero if OK, nonzero if it failed.
 556  *
 557  * Use:         Fetches a public key from the keyring.
 558  */
 559
 560 int km_getpubkey(const char *tag, ge *kpub, time_t *t_exp)
 561 {
 562   key *k;
 563   key_data **kd;
 564   dstr t = DSTR_INIT;
 565   const kgops **ko;
 566   const char *e;
 567   group *g = 0;
 568   ge *p = 0;
 569   algswitch a;
 570   int rc = -1;
 571
 572   /* --- Find the key --- */
 573
 574   if (key_qtag(kf_pub, tag, &t, &k, &kd)) {
 575     a_warn("KEYMGMT", "public-key", "%s", tag, "not-found", A_END);
 576     goto done;
 577   }
 578
 579   /* --- Look up the key type in the table --- */
 580
 581   for (ko = kgtab; *ko; ko++) {
 582     if (strcmp((*ko)->ty, k->type) == 0)
 583       goto tymatch;
 584   }
 585   a_warn("KEYMGMT",
 586          "public-key", "%s", t.buf,
 587          "unknown-type", "%s", k->type,
 588          A_END);
 589   goto done;
 590 tymatch:;
 591
 592   /* --- Load the key --- */
 593
 594   if ((e = (*ko)->loadpub(*kd, &g, &p, &t)) != 0) {
 595     a_warn("KEYMGMT", "public-key", "%s", t.buf, "bad", "%s", e, A_END);
 596     goto done;
 597   }
 598
 599   /* --- Ensure that the group is correct --- *
 600    *
 601    * Dodginess!  We assume that if this works, our global group is willing to
 602    * adopt this public element.  Probably reasonable.
 603    */
 604
 605   if (!group_samep(gg, g)) {
 606     a_warn("KEYMGMT", "public-key", "%s", t.buf, "incorrect-group", A_END);
 607     goto done;
 608   }
 609
 610   /* --- Check the public group element --- */
 611
 612   if (group_check(gg, p)) {
 613     a_warn("KEYMGMT",
 614            "public-key", "%s", t.buf,
 615            "bad-public-group-element",
 616            A_END);
 617     goto done;
 618   }
 619
 620   /* --- Check the algorithms --- */
 621
 622   if ((e = algs_get(&a, kf_pub, k)) != 0) {
 623     a_warn("KEYMGMT",
 624            "public-key", "%s", t.buf,
 625            "bad-algorithm-selection", e,
 626            A_END);
 627     goto done;
 628   }
 629   if (!algs_samep(&a, &algs)) {
 630     a_warn("KEYMGMT",
 631            "public-key", "%s", t.buf,
 632            "algorithm-mismatch",
 633            A_END);
 634     goto done;
 635   }
 636
 637   /* --- Dump the public key --- */
 638
 639   IF_TRACING(T_KEYMGMT, {
 640     trace(T_KEYMGMT, "keymgmt: extracted public key `%s'", t.buf);
 641     trace(T_CRYPTO, "crypto: p = %s", gestr(gg, p));
 642   })
 643
 644   /* --- OK, accept the public key --- */
 645
 646   *t_exp = k->exp;
 647   G_COPY(gg, kpub, p);
 648   rc = 0;
 649
 650   /* --- Tidy up --- */
 651
 652 done:
 653   if (p) G_DESTROY(g, p);
 654   if (g) G_DESTROYGROUP(g);
 655   dstr_destroy(&t);
 656   return (rc);
 657 }
 658
 659 /*----- That's all, folks -------------------------------------------------*/