git.distorted.org.uk Git - u/mdw/catacomb/blob - cc-kem.c

   1 /* -*-c-*-
   2  *
   3  * $Id$
   4  *
   5  * Catcrypt key-encapsulation
   6  *
   7  * (c) 2004 Straylight/Edgeware
   8  */
   9
  10 /*----- Licensing notice --------------------------------------------------*
  11  *
  12  * This file is part of Catacomb.
  13  *
  14  * Catacomb is free software; you can redistribute it and/or modify
  15  * it under the terms of the GNU Library General Public License as
  16  * published by the Free Software Foundation; either version 2 of the
  17  * License, or (at your option) any later version.
  18  *
  19  * Catacomb 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 Library General Public License for more details.
  23  *
  24  * You should have received a copy of the GNU Library General Public
  25  * License along with Catacomb; if not, write to the Free
  26  * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
  27  * MA 02111-1307, USA.
  28  */
  29
  30 /*----- Header files ------------------------------------------------------*/
  31
  32 #include <stdlib.h>
  33
  34 #include <mLib/alloc.h>
  35 #include <mLib/dstr.h>
  36 #include <mLib/report.h>
  37 #include <mLib/sub.h>
  38
  39 #include "mprand.h"
  40 #include "rand.h"
  41
  42 #include "ec.h"
  43 #include "ec-keys.h"
  44 #include "dh.h"
  45 #include "rsa.h"
  46
  47 #include "rmd160.h"
  48 #include "blowfish-cbc.h"
  49
  50 #include "cc.h"
  51
  52 /*----- Key encapsulation -------------------------------------------------*/
  53
  54 /* --- RSA --- */
  55
  56 typedef struct rsa_encctx {
  57   kem k;
  58   rsa_pubctx rp;
  59 } rsa_encctx;
  60
  61 static kem *rsa_encinit(key *k, void *kd)
  62 {
  63   rsa_encctx *re = CREATE(rsa_encctx);
  64   rsa_pubcreate(&re->rp, kd);
  65   return (&re->k);
  66 }
  67
  68 static int rsa_encdoit(kem *k, dstr *d, ghash *h)
  69 {
  70   rsa_encctx *re = (rsa_encctx *)k;
  71   mp *x = mprand_range(MP_NEW, re->rp.rp->n, &rand_global, 0);
  72   mp *y = rsa_pubop(&re->rp, MP_NEW, x);
  73   size_t n = mp_octets(re->rp.rp->n);
  74   dstr_ensure(d, n);
  75   mp_storeb(x, d->buf, n);
  76   GH_HASH(h, d->buf, n);
  77   mp_storeb(y, d->buf, n);
  78   d->len += n;
  79   mp_drop(x);
  80   mp_drop(y);
  81   return (0);
  82 }
  83
  84 static const char *rsa_lengthcheck(mp *n)
  85 {
  86   if (mp_bits(n) < 1020) return ("key too short");
  87   return (0);
  88 }
  89
  90 static const char *rsa_enccheck(kem *k)
  91 {
  92   rsa_encctx *re = (rsa_encctx *)k;
  93   const char *e;
  94   if ((e = rsa_lengthcheck(re->rp.rp->n)) != 0) return (e);
  95   return (0);
  96 }
  97
  98 static void rsa_encdestroy(kem *k)
  99 {
 100   rsa_encctx *re = (rsa_encctx *)k;
 101   rsa_pubdestroy(&re->rp);
 102   DESTROY(re);
 103 }
 104
 105 static const kemops rsa_encops = {
 106   rsa_pubfetch, sizeof(rsa_pub),
 107   rsa_encinit, rsa_encdoit, rsa_enccheck, rsa_encdestroy
 108 };
 109
 110 typedef struct rsa_decctx {
 111   kem k;
 112   rsa_privctx rp;
 113 } rsa_decctx;
 114
 115 static kem *rsa_decinit(key *k, void *kd)
 116 {
 117   rsa_decctx *rd = CREATE(rsa_decctx);
 118   rsa_privcreate(&rd->rp, kd, &rand_global);
 119   return (&rd->k);
 120 }
 121
 122 static int rsa_decdoit(kem *k, dstr *d, ghash *h)
 123 {
 124   rsa_decctx *rd = (rsa_decctx *)k;
 125   mp *x = mp_loadb(MP_NEW, d->buf, d->len);
 126   size_t n;
 127   char *p;
 128
 129   if (MP_CMP(x, >=, rd->rp.rp->n)) {
 130     mp_drop(x);
 131     return (-1);
 132   }
 133   n = mp_octets(rd->rp.rp->n);
 134   p = xmalloc(n);
 135   x = rsa_privop(&rd->rp, x, x);
 136   mp_storeb(x, p, n);
 137   GH_HASH(h, p, n);
 138   mp_drop(x);
 139   xfree(p);
 140   return (0);
 141 }
 142
 143 static const char *rsa_deccheck(kem *k)
 144 {
 145   rsa_decctx *rd = (rsa_decctx *)k;
 146   const char *e;
 147   if ((e = rsa_lengthcheck(rd->rp.rp->n)) != 0) return (e);
 148   return (0);
 149 }
 150
 151 static void rsa_decdestroy(kem *k)
 152 {
 153   rsa_decctx *rd = (rsa_decctx *)k;
 154   rsa_privdestroy(&rd->rp);
 155   DESTROY(rd);
 156 }
 157
 158 static const kemops rsa_decops = {
 159   rsa_privfetch, sizeof(rsa_priv),
 160   rsa_decinit, rsa_decdoit, rsa_deccheck, rsa_decdestroy
 161 };
 162
 163 /* --- DH and EC --- */
 164
 165 typedef struct dh_encctx {
 166   kem k;
 167   group *g;
 168   mp *x;
 169   ge *y;
 170 } dh_encctx;
 171
 172 static dh_encctx *dh_doinit(key *k, const gprime_param *gp, mp *y,
 173                             group *(*makegroup)(const gprime_param *),
 174                             const char *what)
 175 {
 176   dh_encctx *de = CREATE(dh_encctx);
 177   dstr t = DSTR_INIT;
 178
 179   key_fulltag(k, &t);
 180   if ((de->g = makegroup(gp)) == 0)
 181     die(EXIT_FAILURE, "bad %s group in key `%s'", what, t.buf);
 182   de->x = MP_NEW;
 183   de->y = G_CREATE(de->g);
 184   if (G_FROMINT(de->g, de->y, y))
 185     die(EXIT_FAILURE, "bad public key `%s'", t.buf);
 186   dstr_destroy(&t);
 187   return (de);
 188 }
 189
 190 static dh_encctx *ec_doinit(key *k, const char *cstr, const ec *y)
 191 {
 192   dh_encctx *de = CREATE(dh_encctx);
 193   ec_info ei;
 194   const char *e;
 195   dstr t = DSTR_INIT;
 196
 197   key_fulltag(k, &t);
 198   if ((e = ec_getinfo(&ei, cstr)) != 0 ||
 199       (de->g = group_ec(&ei)) == 0)
 200     die(EXIT_FAILURE, "bad elliptic curve spec in key `%s': %s", t.buf, e);
 201   de->x = MP_NEW;
 202   de->y = G_CREATE(de->g);
 203   if (G_FROMEC(de->g, de->y, y))
 204     die(EXIT_FAILURE, "bad public curve point `%s'", t.buf);
 205   dstr_destroy(&t);
 206   return (de);
 207 }
 208
 209 static kem *dh_encinit(key *k, void *kd)
 210 {
 211   dh_pub *dp = kd;
 212   dh_encctx *de = dh_doinit(k, &dp->dp, dp->y, group_prime, "prime");
 213   return (&de->k);
 214 }
 215
 216 static kem *bindh_encinit(key *k, void *kd)
 217 {
 218   dh_pub *dp = kd;
 219   dh_encctx *de = dh_doinit(k, &dp->dp, dp->y, group_binary, "binary");
 220   return (&de->k);
 221 }
 222
 223 static kem *ec_encinit(key *k, void *kd)
 224 {
 225   ec_pub *ep = kd;
 226   dh_encctx *de = ec_doinit(k, ep->cstr, &ep->p);
 227   return (&de->k);
 228 }
 229
 230 static int dh_encdoit(kem *k, dstr *d, ghash *h)
 231 {
 232   dh_encctx *de = (dh_encctx *)k;
 233   mp *r = mprand_range(MP_NEW, de->g->r, &rand_global, 0);
 234   ge *x = G_CREATE(de->g);
 235   ge *y = G_CREATE(de->g);
 236   size_t n = de->g->noctets;
 237   buf b;
 238
 239   G_EXP(de->g, x, de->g->g, r);
 240   G_EXP(de->g, y, de->y, r);
 241   dstr_ensure(d, n);
 242   buf_init(&b, d->buf, n);
 243   G_TORAW(de->g, &b, y);
 244   GH_HASH(h, BBASE(&b), BLEN(&b));
 245   buf_init(&b, d->buf, n);
 246   G_TORAW(de->g, &b, x);
 247   GH_HASH(h, BBASE(&b), BLEN(&b));
 248   d->len += BLEN(&b);
 249   mp_drop(r);
 250   G_DESTROY(de->g, x);
 251   G_DESTROY(de->g, y);
 252   return (0);
 253 }
 254
 255 static const char *dh_enccheck(kem *k)
 256 {
 257   dh_encctx *de = (dh_encctx *)k;
 258   const char *e;
 259   if ((e = G_CHECK(de->g, &rand_global)) != 0)
 260     return (0);
 261   if (group_check(de->g, de->y))
 262     return ("public key not in subgroup");
 263   return (0);
 264 }
 265
 266 static void dh_encdestroy(kem *k)
 267 {
 268   dh_encctx *de = (dh_encctx *)k;
 269   G_DESTROY(de->g, de->y);
 270   mp_drop(de->x);
 271   G_DESTROYGROUP(de->g);
 272   DESTROY(de);
 273 }
 274
 275 static const kemops dh_encops = {
 276   dh_pubfetch, sizeof(dh_pub),
 277   dh_encinit, dh_encdoit, dh_enccheck, dh_encdestroy
 278 };
 279
 280 static const kemops bindh_encops = {
 281   dh_pubfetch, sizeof(dh_pub),
 282   bindh_encinit, dh_encdoit, dh_enccheck, dh_encdestroy
 283 };
 284
 285 static const kemops ec_encops = {
 286   ec_pubfetch, sizeof(ec_pub),
 287   ec_encinit, dh_encdoit, dh_enccheck, dh_encdestroy
 288 };
 289
 290 static kem *dh_decinit(key *k, void *kd)
 291 {
 292   dh_priv *dp = kd;
 293   dh_encctx *de = dh_doinit(k, &dp->dp, dp->y, group_prime, "prime");
 294   de->x = MP_COPY(dp->x);
 295   return (&de->k);
 296 }
 297
 298 static kem *bindh_decinit(key *k, void *kd)
 299 {
 300   dh_priv *dp = kd;
 301   dh_encctx *de = dh_doinit(k, &dp->dp, dp->y, group_binary, "binary");
 302   de->x = MP_COPY(dp->x);
 303   return (&de->k);
 304 }
 305
 306 static kem *ec_decinit(key *k, void *kd)
 307 {
 308   ec_priv *ep = kd;
 309   dh_encctx *de = ec_doinit(k, ep->cstr, &ep->p);
 310   de->x = MP_COPY(ep->x);
 311   return (&de->k);
 312 }
 313
 314 static int dh_decdoit(kem *k, dstr *d, ghash *h)
 315 {
 316   dh_encctx *de = (dh_encctx *)k;
 317   ge *x = G_CREATE(de->g);
 318   size_t n = de->g->noctets;
 319   void *p = xmalloc(n);
 320   buf b;
 321   int rc = -1;
 322
 323   buf_init(&b, d->buf, d->len);
 324   if (G_FROMRAW(de->g, &b, x) || group_check(de->g, x))
 325     goto done;
 326   G_EXP(de->g, x, x, de->x);
 327   buf_init(&b, p, n);
 328   G_TORAW(de->g, &b, x);
 329   GH_HASH(h, BBASE(&b), BLEN(&b));
 330   GH_HASH(h, d->buf, d->len);
 331   rc = 0;
 332 done:
 333   G_DESTROY(de->g, x);
 334   xfree(p);
 335   return (rc);
 336 }
 337
 338 static const kemops dh_decops = {
 339   dh_privfetch, sizeof(dh_priv),
 340   dh_decinit, dh_decdoit, dh_enccheck, dh_encdestroy
 341 };
 342
 343 static const kemops bindh_decops = {
 344   dh_privfetch, sizeof(dh_priv),
 345   bindh_decinit, dh_decdoit, dh_enccheck, dh_encdestroy
 346 };
 347
 348 static const kemops ec_decops = {
 349   ec_privfetch, sizeof(ec_priv),
 350   ec_decinit, dh_decdoit, dh_enccheck, dh_encdestroy
 351 };
 352
 353 /* --- Symmetric --- */
 354
 355 typedef struct symm_ctx {
 356   kem k;
 357   key_packdef kp;
 358   key_bin kb;
 359 } symm_ctx;
 360
 361 static kem *symm_init(key *k, void *kd)
 362 {
 363   symm_ctx *s;
 364   dstr d = DSTR_INIT;
 365   int err;
 366
 367   s = CREATE(symm_ctx);
 368
 369   key_fulltag(k, &d);
 370   s->kp.e = KENC_BINARY;
 371   s->kp.p = &s->kb;
 372   s->kp.kd = 0;
 373
 374   if ((err = key_unpack(&s->kp, kd, &d)) != 0) {
 375     die(EXIT_FAILURE, "failed to unpack symmetric key `%s': %s",
 376         d.buf, key_strerror(err));
 377   }
 378   dstr_destroy(&d);
 379   return (&s->k);
 380 }
 381
 382 static int symm_decdoit(kem *k, dstr *d, ghash *h)
 383 {
 384   symm_ctx *s = (symm_ctx *)k;
 385
 386   GH_HASH(h, s->kb.k, s->kb.sz);
 387   GH_HASH(h, d->buf, d->len);
 388   return (0);
 389 }
 390
 391 static int symm_encdoit(kem *k, dstr *d, ghash *h)
 392 {
 393   dstr_ensure(d, h->ops->c->hashsz);
 394   d->len += h->ops->c->hashsz;
 395   rand_get(RAND_GLOBAL, d->buf, d->len);
 396   return (symm_decdoit(k, d, h));
 397 }
 398
 399 static const char *symm_check(kem *k) { return (0); }
 400
 401 static void symm_destroy(kem *k)
 402   { symm_ctx *s = (symm_ctx *)k; key_unpackdone(&s->kp); }
 403
 404 static const kemops symm_encops = {
 405   0, 0,
 406   symm_init, symm_encdoit, symm_check, symm_destroy
 407 };
 408
 409 static const kemops symm_decops = {
 410   0, 0,
 411   symm_init, symm_decdoit, symm_check, symm_destroy
 412 };
 413
 414 /* --- The switch table --- */
 415
 416 const struct kemtab kemtab[] = {
 417   { "rsa",      &rsa_encops,    &rsa_decops },
 418   { "dh",       &dh_encops,     &dh_decops },
 419   { "bindh",    &bindh_encops,  &bindh_decops },
 420   { "ec",       &ec_encops,     &ec_decops },
 421   { "symm",     &symm_encops,   &symm_decops },
 422   { 0,          0,              0 }
 423 };
 424
 425 /* --- @getkem@ --- *
 426  *
 427  * Arguments:   @key *k@ = the key to load
 428  *              @const char *app@ = application name
 429  *              @int wantpriv@ = nonzero if we want to decrypt
 430  *
 431  * Returns:     A key-encapsulating thing.
 432  *
 433  * Use:         Loads a key.
 434  */
 435
 436 kem *getkem(key *k, const char *app, int wantpriv)
 437 {
 438   const char *kalg, *halg = 0, *calg = 0;
 439   dstr d = DSTR_INIT;
 440   dstr t = DSTR_INIT;
 441   size_t n;
 442   char *p = 0;
 443   const char *q;
 444   kem *kk;
 445   const struct kemtab *kt;
 446   const kemops *ko;
 447   void *kd;
 448   int e;
 449   key_packdef *kp;
 450
 451   /* --- Setup stuff --- */
 452
 453   key_fulltag(k, &t);
 454
 455   /* --- Get the KEM name --- *
 456    *
 457    * Take the attribute if it's there; otherwise use the key type.
 458    */
 459
 460   n = strlen(app);
 461   if ((q = key_getattr(0, k, "kem")) != 0) {
 462     dstr_puts(&d, q);
 463     p = d.buf;
 464   } else if (strncmp(k->type, app, n) == 0 && k->type[n] == '-') {
 465     dstr_puts(&d, k->type);
 466     p = d.buf + n + 1;
 467   } else
 468     die(EXIT_FAILURE, "no KEM for key `%s'", t.buf);
 469   kalg = p;
 470
 471   /* --- Grab the encryption scheme --- *
 472    *
 473    * Grab it from the KEM if it's there, but override it from the attribute.
 474    */
 475
 476   if (p && (p = strchr(p, '/')) != 0) {
 477     *p++ = 0;
 478     calg = p;
 479   }
 480   if ((q = key_getattr(0, k, "cipher")) != 0)
 481     calg = q;
 482
 483   /* --- Grab the hash function --- */
 484
 485   if (p && (p = strchr(p, '/')) != 0) {
 486     *p++ = 0;
 487     halg = p;
 488   }
 489   if ((q = key_getattr(0, k, "hash")) != 0)
 490     halg = q;
 491
 492   /* --- Instantiate the KEM --- */
 493
 494   for (kt = kemtab; kt->name; kt++) {
 495     if (strcmp(kt->name, kalg) == 0)
 496       goto k_found;
 497   }
 498   die(EXIT_FAILURE, "key encapsulation mechanism `%s' not found in key `%s'",
 499       kalg, t.buf);
 500 k_found:;
 501   ko = wantpriv ? kt->decops : kt->encops;
 502   if (!ko->kf) {
 503     kd = k->k;
 504     key_incref(kd);
 505   } else {
 506     kd = xmalloc(ko->kdsz);
 507     kp = key_fetchinit(ko->kf, 0, kd);
 508     if ((e = key_fetch(kp, k)) != 0) {
 509       die(EXIT_FAILURE, "error fetching key `%s': %s",
 510           t.buf, key_strerror(e));
 511     }
 512   }
 513   kk = ko->init(k, kd);
 514   kk->kp = kp;
 515   kk->ops = ko;
 516   kk->kd = kd;
 517
 518   /* --- Set up the algorithms --- */
 519
 520   if (!halg)
 521     kk->h = &rmd160;
 522   else if ((kk->h = ghash_byname(halg)) == 0) {
 523     die(EXIT_FAILURE, "hash algorithm `%s' not found in key `%s'",
 524         halg, t.buf);
 525   }
 526
 527   if (!calg)
 528     kk->c = &blowfish_cbc;
 529   else if ((kk->c = gcipher_byname(calg)) == 0) {
 530     die(EXIT_FAILURE, "encryption scheme `%s' not found in key `%s'",
 531         calg, t.buf);
 532   }
 533
 534   dstr_reset(&d);
 535   if ((q = key_getattr(0, k, "kdf")) == 0) {
 536     dstr_putf(&d, "%s-mgf", kk->h->name);
 537     q = d.buf;
 538   }
 539   if ((kk->cx = gcipher_byname(q)) == 0) {
 540     die(EXIT_FAILURE, "encryption scheme (KDF) `%s' not found in key `%s'",
 541         q, t.buf);
 542   }
 543
 544   dstr_reset(&d);
 545   if ((q = key_getattr(0, k, "mac")) == 0) {
 546     dstr_putf(&d, "%s-hmac", kk->h->name);
 547     q = d.buf;
 548   }
 549   if ((kk->m = gmac_byname(q)) == 0) {
 550     die(EXIT_FAILURE,
 551         "message authentication code `%s' not found in key `%s'",
 552         q, t.buf);
 553   }
 554
 555   /* --- Tidy up --- */
 556
 557   dstr_destroy(&d);
 558   dstr_destroy(&t);
 559   return (kk);
 560 }
 561
 562 /* --- @setupkem@ --- *
 563  *
 564  * Arguments:   @kem *k@ = key-encapsulation thing
 565  *              @dstr *d@ = key-encapsulation data
 566  *              @gcipher **cx@ = key-expansion function (for IVs)
 567  *              @gcipher **c@ = where to put initialized encryption scheme
 568  *              @gmac **m@ = where to put initialized MAC
 569  *
 570  * Returns:     Zero on success, nonzero on failure.
 571  *
 572  * Use:         Initializes all the various symmetric things from a KEM.
 573  */
 574
 575 int setupkem(kem *k, dstr *d, gcipher **cx, gcipher **c, gmac **m)
 576 {
 577   octet *kd;
 578   size_t n, cn, mn;
 579   ghash *h;
 580   int rc = -1;
 581
 582   h = GH_INIT(k->h);
 583   if (k->ops->doit(k, d, h))
 584     goto done;
 585   n = keysz(GH_CLASS(h)->hashsz, k->cx->keysz);
 586   if (!n)
 587     goto done;
 588   kd = GH_DONE(h, 0);
 589   *cx = GC_INIT(k->cx, kd, n);
 590
 591   cn = keysz(0, k->c->keysz); n = cn;
 592   mn = keysz(0, k->m->keysz); if (mn > n) n = mn;
 593   kd = xmalloc(n);
 594   GC_ENCRYPT(*cx, 0, kd, cn);
 595   *c = GC_INIT(k->c, kd, cn);
 596   GC_ENCRYPT(*cx, 0, kd, mn);
 597   *m = GM_KEY(k->m, kd, mn);
 598   xfree(kd);
 599
 600   rc = 0;
 601 done:
 602   GH_DESTROY(h);
 603   return (rc);
 604 }
 605
 606 /* --- @freekem@ --- *
 607  *
 608  * Arguments:   @kem *k@ = key-encapsulation thing
 609  *
 610  * Returns:     ---
 611  *
 612  * Use:         Frees up a key-encapsulation thing.
 613  */
 614
 615 void freekem(kem *k)
 616 {
 617   if (!k->ops->kf)
 618     key_drop(k->kd);
 619   else {
 620     key_fetchdone(k->kp);
 621     xfree(k->kd);
 622   }
 623   k->ops->destroy(k);
 624 }
 625
 626 /*----- That's all, folks -------------------------------------------------*/