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

   1 /* -*-c-*-
   2  *
   3  * Catcrypt key-encapsulation
   4  *
   5  * (c) 2004 Straylight/Edgeware
   6  */
   7
   8 /*----- Licensing notice --------------------------------------------------*
   9  *
  10  * This file is part of Catacomb.
  11  *
  12  * Catacomb is free software; you can redistribute it and/or modify
  13  * it under the terms of the GNU Library General Public License as
  14  * published by the Free Software Foundation; either version 2 of the
  15  * License, or (at your option) any later version.
  16  *
  17  * Catacomb is distributed in the hope that it will be useful,
  18  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  19  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  20  * GNU Library General Public License for more details.
  21  *
  22  * You should have received a copy of the GNU Library General Public
  23  * License along with Catacomb; if not, write to the Free
  24  * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
  25  * MA 02111-1307, USA.
  26  */
  27
  28 /*----- Header files ------------------------------------------------------*/
  29
  30 #define _FILE_OFFSET_BITS 64
  31
  32 #include <stdlib.h>
  33
  34 #include <mLib/alloc.h>
  35 #include <mLib/dstr.h>
  36 #include <mLib/macros.h>
  37 #include <mLib/report.h>
  38 #include <mLib/sub.h>
  39
  40 #include "gaead.h"
  41 #include "mprand.h"
  42 #include "rand.h"
  43
  44 #include "ec.h"
  45 #include "ec-keys.h"
  46 #include "dh.h"
  47 #include "rsa.h"
  48 #include "x25519.h"
  49 #include "x448.h"
  50
  51 #include "rmd160.h"
  52 #include "blowfish-cbc.h"
  53 #include "chacha20-poly1305.h"
  54 #include "poly1305.h"
  55 #include "salsa20.h"
  56 #include "chacha.h"
  57
  58 #include "cc.h"
  59
  60 /*----- Bulk crypto -------------------------------------------------------*/
  61
  62 /* --- Authenticated encryption schemes --- */
  63
  64 typedef struct aead_encctx {
  65   bulk b;
  66   const gcaead *aec;
  67   gaead_key *key;
  68   union { gaead_enc *enc; gaead_dec *dec; } ed;
  69   octet *t;
  70   size_t nsz, tsz;
  71 } aead_encctx;
  72
  73 static bulk *aead_internalinit(key *k, const gcaead *aec)
  74 {
  75   aead_encctx *ctx = CREATE(aead_encctx);
  76
  77   ctx->key = 0;
  78   ctx->aec = aec;
  79   if ((ctx->nsz = keysz_pad(4, aec->noncesz)) == 0)
  80     die(EXIT_FAILURE, "no suitable nonce size for `%s'", aec->name);
  81   ctx->tsz = keysz(0, ctx->aec->tagsz);
  82
  83   return (&ctx->b);
  84 }
  85
  86 static bulk *aead_init(key *k, const char *calg, const char *halg)
  87 {
  88   const gcaead *aec;
  89   const char *q;
  90   dstr t = DSTR_INIT;
  91
  92   key_fulltag(k, &t);
  93
  94   if ((q = key_getattr(0, k, "cipher")) != 0) calg = q;
  95   if (!calg) aec = &chacha20_poly1305;
  96   else if ((aec = gaead_byname(calg)) == 0)
  97     die(EXIT_FAILURE, "AEAD scheme `%s' not found in key `%s'",
  98         calg, t.buf);
  99
 100   dstr_destroy(&t);
 101   return (aead_internalinit(k, aec));
 102 }
 103
 104 static int aead_commonsetup(aead_encctx *ctx, gcipher *cx)
 105 {
 106   size_t ksz, n;
 107
 108   n = ksz = keysz(0, ctx->aec->keysz);
 109   if (n < ctx->nsz) n = ctx->nsz;
 110   if (n < ctx->tsz) n = ctx->tsz;
 111   ctx->t = xmalloc(n);
 112
 113   GC_ENCRYPT(cx, 0, ctx->t, ksz);
 114   ctx->key = GAEAD_KEY(ctx->aec, ctx->t, ksz);
 115   return (0);
 116 }
 117
 118 static size_t aead_overhead(bulk *b)
 119   { aead_encctx *ctx = (aead_encctx *)b; return (ctx->aec->ohd + ctx->tsz); }
 120
 121 static void aead_commondestroy(aead_encctx *ctx)
 122 {
 123   if (ctx->key) GAEAD_DESTROY(ctx->key);
 124   xfree(ctx->t);
 125   DESTROY(ctx);
 126 }
 127
 128 static int aead_encsetup(bulk *b, gcipher *cx)
 129 {
 130   aead_encctx *ctx = (aead_encctx *)b;
 131   ctx->ed.enc = 0; return (aead_commonsetup(ctx, cx));
 132 }
 133
 134 static const char *aead_encdoit(bulk *b, uint32 seq, buf *bb,
 135                                 const void *p, size_t sz)
 136 {
 137   aead_encctx *ctx = (aead_encctx *)b;
 138   octet *t;
 139   int rc;
 140
 141   memset(ctx->t + 4, 0, ctx->nsz - 4); STORE32_B(ctx->t, seq);
 142   if (!ctx->ed.enc)
 143     ctx->ed.enc = GAEAD_ENC(ctx->key, ctx->t, ctx->nsz, 0, sz, ctx->tsz);
 144   else
 145     GAEAD_REINIT(ctx->ed.enc, ctx->t, ctx->nsz, 0, sz, ctx->tsz);
 146   t = buf_get(bb, ctx->tsz); assert(t);
 147   rc = GAEAD_ENCRYPT(ctx->ed.enc, p, sz, bb); assert(rc >= 0);
 148   rc = GAEAD_DONE(ctx->ed.enc, 0, bb, t, ctx->tsz); assert(rc >= 0);
 149   return (0);
 150 }
 151
 152 static void aead_encdestroy(bulk *b)
 153 {
 154   aead_encctx *ctx = (aead_encctx *)b;
 155   if (ctx->ed.enc) GAEAD_DESTROY(ctx->ed.enc);
 156   aead_commondestroy(ctx);
 157 }
 158
 159 static int aead_decsetup(bulk *b, gcipher *cx)
 160 {
 161   aead_encctx *ctx = (aead_encctx *)b;
 162   ctx->ed.dec = 0; return (aead_commonsetup(ctx, cx));
 163 }
 164
 165 static const char *aead_decdoit(bulk *b, uint32 seq, buf *bb,
 166                                 const void *p, size_t sz)
 167 {
 168   aead_encctx *ctx = (aead_encctx *)b;
 169   buf bin;
 170   const octet *t;
 171   int rc;
 172
 173   memset(ctx->t + 4, 0, ctx->nsz - 4); STORE32_B(ctx->t, seq);
 174   if (!ctx->ed.dec)
 175     ctx->ed.dec = GAEAD_DEC(ctx->key, ctx->t, ctx->nsz, 0, sz, ctx->tsz);
 176   else
 177     GAEAD_REINIT(ctx->ed.enc, ctx->t, ctx->nsz, 0, sz, ctx->tsz);
 178
 179   buf_init(&bin, (/*unconst*/ void *)p, sz);
 180   t = buf_get(&bin, ctx->tsz); if (!t) return ("no tag");
 181   rc = GAEAD_DECRYPT(ctx->ed.dec, BCUR(&bin), BLEFT(&bin), bb);
 182   assert(rc >= 0);
 183   rc = GAEAD_DONE(ctx->ed.dec, 0, bb, t, ctx->tsz); assert(rc >= 0);
 184   if (!rc) return ("authentication failure");
 185   return (0);
 186 }
 187
 188 static void aead_decdestroy(bulk *b)
 189 {
 190   aead_encctx *ctx = (aead_encctx *)b;
 191   if (ctx->ed.dec) GAEAD_DESTROY(ctx->ed.dec);
 192   aead_commondestroy(ctx);
 193 }
 194
 195 static const struct bulkops aead_encops = {
 196   aead_init, aead_encsetup, aead_overhead,
 197   aead_encdoit, aead_encdestroy
 198 }, aead_decops = {
 199   aead_init, aead_decsetup, aead_overhead,
 200   aead_decdoit, aead_decdestroy
 201 };
 202
 203 /* --- NaCl `secretbox' in terms of AEAD --- */
 204
 205 static bulk *naclbox_init(key *k, const char *calg, const char *halg)
 206 {
 207   const gcaead *aec;
 208   dstr t = DSTR_INIT;
 209   const char *q;
 210
 211   key_fulltag(k, &t);
 212
 213   if ((q = key_getattr(0, k, "cipher")) != 0) calg = q;
 214   if (!calg || STRCMP(calg, ==, "salsa20")) aec = &salsa20_naclbox;
 215   else if (STRCMP(calg, ==, "salsa20/12")) aec = &salsa2012_naclbox;
 216   else if (STRCMP(calg, ==, "salsa20/8")) aec = &salsa208_naclbox;
 217   else if (STRCMP(calg, ==, "chacha20")) aec = &chacha20_naclbox;
 218   else if (STRCMP(calg, ==, "chacha12")) aec = &chacha12_naclbox;
 219   else if (STRCMP(calg, ==, "chacha8")) aec = &chacha8_naclbox;
 220   else {
 221     die(EXIT_FAILURE,
 222         "unknown or inappropriate encryption scheme `%s' in key `%s'",
 223         calg, t.buf);
 224   }
 225
 226   dstr_destroy(&t);
 227   return (aead_internalinit(k, aec));
 228 }
 229
 230 static const bulkops naclbox_encops = {
 231   naclbox_init, aead_encsetup, aead_overhead,
 232   aead_encdoit, aead_encdestroy
 233 }, naclbox_decops = {
 234   naclbox_init, aead_decsetup, aead_overhead,
 235   aead_decdoit, aead_decdestroy
 236 };
 237
 238 /* --- Generic composition --- */
 239
 240 typedef struct gencomp_encctx {
 241   bulk b;
 242   const gccipher *cc;
 243   const gcmac *mc;
 244   gcipher *c, *cx;
 245   gmac *m;
 246   octet *t; size_t tsz;
 247 } gencomp_encctx;
 248
 249 static bulk *gencomp_init(key *k, const char *calg, const char *halg)
 250 {
 251   gencomp_encctx *ctx = CREATE(gencomp_encctx);
 252   const char *q;
 253   dstr d = DSTR_INIT, t = DSTR_INIT;
 254
 255   key_fulltag(k, &t);
 256
 257   if ((q = key_getattr(0, k, "cipher")) != 0) calg = q;
 258   if (!calg) ctx->cc = &blowfish_cbc;
 259   else if ((ctx->cc = gcipher_byname(calg)) == 0) {
 260     die(EXIT_FAILURE, "encryption scheme `%s' not found in key `%s'",
 261         calg, t.buf);
 262   }
 263
 264   dstr_reset(&d);
 265   if ((q = key_getattr(0, k, "mac")) == 0) {
 266     dstr_putf(&d, "%s-hmac", halg);
 267     q = d.buf;
 268   }
 269   if ((ctx->mc = gmac_byname(q)) == 0) {
 270     die(EXIT_FAILURE,
 271         "message authentication code `%s' not found in key `%s'",
 272         q, t.buf);
 273   }
 274
 275   return (&ctx->b);
 276 }
 277
 278 static int gencomp_setup(bulk *b, gcipher *cx)
 279 {
 280   gencomp_encctx *ctx = (gencomp_encctx *)b;
 281   size_t cn, mn, n;
 282   octet *kd;
 283
 284   ctx->cx = cx;
 285   n = ctx->cc->blksz;
 286   cn = keysz(0, ctx->cc->keysz); if (cn > n) n = cn;
 287   mn = keysz(0, ctx->mc->keysz); if (mn > n) n = mn;
 288   ctx->t = kd = xmalloc(n); ctx->tsz = n;
 289   GC_ENCRYPT(cx, 0, kd, cn);
 290   ctx->c = GC_INIT(ctx->cc, kd, cn);
 291   GC_ENCRYPT(cx, 0, kd, mn);
 292   ctx->m = GM_KEY(ctx->mc, kd, mn);
 293   return (0);
 294 }
 295
 296 static size_t gencomp_overhead(bulk *b)
 297 {
 298   gencomp_encctx *ctx = (gencomp_encctx *)b;
 299   return (ctx->cc->blksz + ctx->mc->hashsz); }
 300
 301 static void gencomp_destroy(bulk *b)
 302 {
 303   gencomp_encctx *ctx = (gencomp_encctx *)b;
 304
 305   GC_DESTROY(ctx->c);
 306   GC_DESTROY(ctx->m);
 307   xfree(ctx->t);
 308   DESTROY(ctx);
 309 }
 310
 311 static const char *gencomp_encdoit(bulk *b, uint32 seq, buf *bb,
 312                                    const void *p, size_t sz)
 313 {
 314   gencomp_encctx *ctx = (gencomp_encctx *)b;
 315   octet *tag, *ct;
 316   ghash *h = GM_INIT(ctx->m);
 317
 318   GH_HASHU32(h, seq);
 319   if (ctx->cc->blksz) {
 320     GC_ENCRYPT(ctx->cx, 0, ctx->t, ctx->cc->blksz);
 321     GC_SETIV(ctx->c, ctx->t);
 322   }
 323   tag = buf_get(bb, ctx->mc->hashsz); assert(tag);
 324   ct = buf_get(bb, sz); assert(ct);
 325   GC_ENCRYPT(ctx->c, p, ct, sz);
 326   GH_HASH(h, ct, sz);
 327   GH_DONE(h, tag);
 328   GH_DESTROY(h);
 329   return (0);
 330 }
 331
 332 static const char *gencomp_decdoit(bulk *b, uint32 seq, buf *bb,
 333                                    const void *p, size_t sz)
 334 {
 335   gencomp_encctx *ctx = (gencomp_encctx *)b;
 336   buf bin;
 337   const octet *tag, *ct;
 338   octet *pt;
 339   ghash *h;
 340   int ok;
 341
 342   buf_init(&bin, (/*unconst*/ void *)p, sz);
 343   if ((tag = buf_get(&bin, ctx->mc->hashsz)) == 0) return ("no tag");
 344   ct = BCUR(&bin); sz = BLEFT(&bin);
 345   pt = buf_get(bb, sz); assert(pt);
 346
 347   h = GM_INIT(ctx->m);
 348   GH_HASHU32(h, seq);
 349   GH_HASH(h, ct, sz);
 350   ok = ct_memeq(tag, GH_DONE(h, 0), ctx->mc->hashsz);
 351   GH_DESTROY(h);
 352   if (!ok) return ("authentication failure");
 353
 354   if (ctx->cc->blksz) {
 355     GC_ENCRYPT(ctx->cx, 0, ctx->t, ctx->cc->blksz);
 356     GC_SETIV(ctx->c, ctx->t);
 357   }
 358   GC_DECRYPT(ctx->c, ct, pt, sz);
 359   return (0);
 360 }
 361
 362 static const bulkops gencomp_encops = {
 363   gencomp_init, gencomp_setup, gencomp_overhead,
 364   gencomp_encdoit, gencomp_destroy
 365 }, gencomp_decops = {
 366   gencomp_init, gencomp_setup, gencomp_overhead,
 367   gencomp_decdoit, gencomp_destroy
 368 };
 369
 370 const struct bulktab bulktab[] = {
 371   { "gencomp",  &gencomp_encops,        &gencomp_decops },
 372   { "naclbox",  &naclbox_encops,        &naclbox_decops },
 373   { "aead",     &aead_encops,           &aead_decops },
 374   { 0,          0,                      0 }
 375 };
 376
 377 /*----- Key encapsulation -------------------------------------------------*/
 378
 379 /* --- RSA --- */
 380
 381 typedef struct rsa_encctx {
 382   kem k;
 383   rsa_pubctx rp;
 384 } rsa_encctx;
 385
 386 static kem *rsa_encinit(key *k, void *kd)
 387 {
 388   rsa_encctx *re = CREATE(rsa_encctx);
 389   rsa_pubcreate(&re->rp, kd);
 390   return (&re->k);
 391 }
 392
 393 static int rsa_encdoit(kem *k, dstr *d, ghash *h)
 394 {
 395   rsa_encctx *re = (rsa_encctx *)k;
 396   mp *x = mprand_range(MP_NEW, re->rp.rp->n, &rand_global, 0);
 397   mp *y = rsa_pubop(&re->rp, MP_NEW, x);
 398   size_t n = mp_octets(re->rp.rp->n);
 399   dstr_ensure(d, n);
 400   mp_storeb(x, d->buf, n);
 401   GH_HASH(h, d->buf, n);
 402   mp_storeb(y, d->buf, n);
 403   d->len += n;
 404   mp_drop(x);
 405   mp_drop(y);
 406   return (0);
 407 }
 408
 409 static const char *rsa_lengthcheck(mp *n)
 410 {
 411   if (mp_bits(n) < 1020) return ("key too short");
 412   return (0);
 413 }
 414
 415 static const char *rsa_enccheck(kem *k)
 416 {
 417   rsa_encctx *re = (rsa_encctx *)k;
 418   const char *e;
 419   if ((e = rsa_lengthcheck(re->rp.rp->n)) != 0) return (e);
 420   return (0);
 421 }
 422
 423 static void rsa_encdestroy(kem *k)
 424 {
 425   rsa_encctx *re = (rsa_encctx *)k;
 426   rsa_pubdestroy(&re->rp);
 427   DESTROY(re);
 428 }
 429
 430 static const kemops rsa_encops = {
 431   rsa_pubfetch, sizeof(rsa_pub),
 432   rsa_encinit, rsa_encdoit, rsa_enccheck, rsa_encdestroy
 433 };
 434
 435 typedef struct rsa_decctx {
 436   kem k;
 437   rsa_privctx rp;
 438 } rsa_decctx;
 439
 440 static kem *rsa_decinit(key *k, void *kd)
 441 {
 442   rsa_decctx *rd = CREATE(rsa_decctx);
 443   rsa_privcreate(&rd->rp, kd, &rand_global);
 444   return (&rd->k);
 445 }
 446
 447 static int rsa_decdoit(kem *k, dstr *d, ghash *h)
 448 {
 449   rsa_decctx *rd = (rsa_decctx *)k;
 450   mp *x = mp_loadb(MP_NEW, d->buf, d->len);
 451   size_t n;
 452   char *p;
 453
 454   if (MP_CMP(x, >=, rd->rp.rp->n)) {
 455     mp_drop(x);
 456     return (-1);
 457   }
 458   n = mp_octets(rd->rp.rp->n);
 459   p = xmalloc(n);
 460   x = rsa_privop(&rd->rp, x, x);
 461   mp_storeb(x, p, n);
 462   GH_HASH(h, p, n);
 463   mp_drop(x);
 464   xfree(p);
 465   return (0);
 466 }
 467
 468 static const char *rsa_deccheck(kem *k)
 469 {
 470   rsa_decctx *rd = (rsa_decctx *)k;
 471   const char *e;
 472   if ((e = rsa_lengthcheck(rd->rp.rp->n)) != 0) return (e);
 473   return (0);
 474 }
 475
 476 static void rsa_decdestroy(kem *k)
 477 {
 478   rsa_decctx *rd = (rsa_decctx *)k;
 479   rsa_privdestroy(&rd->rp);
 480   DESTROY(rd);
 481 }
 482
 483 static const kemops rsa_decops = {
 484   rsa_privfetch, sizeof(rsa_priv),
 485   rsa_decinit, rsa_decdoit, rsa_deccheck, rsa_decdestroy
 486 };
 487
 488 /* --- DH and EC --- */
 489
 490 typedef struct dh_encctx {
 491   kem k;
 492   group *g;
 493   mp *x;
 494   ge *y;
 495 } dh_encctx;
 496
 497 static dh_encctx *dh_doinit(key *k, const gprime_param *gp, mp *y,
 498                             group *(*makegroup)(const gprime_param *),
 499                             const char *what)
 500 {
 501   dh_encctx *de = CREATE(dh_encctx);
 502   dstr t = DSTR_INIT;
 503
 504   key_fulltag(k, &t);
 505   if ((de->g = makegroup(gp)) == 0)
 506     die(EXIT_FAILURE, "bad %s group in key `%s'", what, t.buf);
 507   de->x = MP_NEW;
 508   de->y = G_CREATE(de->g);
 509   if (G_FROMINT(de->g, de->y, y))
 510     die(EXIT_FAILURE, "bad public key `%s'", t.buf);
 511   dstr_destroy(&t);
 512   return (de);
 513 }
 514
 515 static dh_encctx *ec_doinit(key *k, const char *cstr, const ec *y)
 516 {
 517   dh_encctx *de = CREATE(dh_encctx);
 518   ec_info ei;
 519   const char *e;
 520   dstr t = DSTR_INIT;
 521
 522   key_fulltag(k, &t);
 523   if ((e = ec_getinfo(&ei, cstr)) != 0 ||
 524       (de->g = group_ec(&ei)) == 0)
 525     die(EXIT_FAILURE, "bad elliptic curve spec in key `%s': %s", t.buf, e);
 526   de->x = MP_NEW;
 527   de->y = G_CREATE(de->g);
 528   if (G_FROMEC(de->g, de->y, y))
 529     die(EXIT_FAILURE, "bad public curve point `%s'", t.buf);
 530   dstr_destroy(&t);
 531   return (de);
 532 }
 533
 534 static kem *dh_encinit(key *k, void *kd)
 535 {
 536   dh_pub *dp = kd;
 537   dh_encctx *de = dh_doinit(k, &dp->dp, dp->y, group_prime, "prime");
 538   return (&de->k);
 539 }
 540
 541 static kem *bindh_encinit(key *k, void *kd)
 542 {
 543   dh_pub *dp = kd;
 544   dh_encctx *de = dh_doinit(k, &dp->dp, dp->y, group_binary, "binary");
 545   return (&de->k);
 546 }
 547
 548 static kem *ec_encinit(key *k, void *kd)
 549 {
 550   ec_pub *ep = kd;
 551   dh_encctx *de = ec_doinit(k, ep->cstr, &ep->p);
 552   return (&de->k);
 553 }
 554
 555 static int dh_encdoit(kem *k, dstr *d, ghash *h)
 556 {
 557   dh_encctx *de = (dh_encctx *)k;
 558   mp *r = mprand_range(MP_NEW, de->g->r, &rand_global, 0);
 559   ge *x = G_CREATE(de->g);
 560   ge *y = G_CREATE(de->g);
 561   size_t n = de->g->noctets;
 562   buf b;
 563
 564   G_EXP(de->g, x, de->g->g, r);
 565   G_EXP(de->g, y, de->y, r);
 566   dstr_ensure(d, n);
 567   buf_init(&b, d->buf, n);
 568   G_TORAW(de->g, &b, y);
 569   GH_HASH(h, BBASE(&b), BLEN(&b));
 570   buf_init(&b, d->buf, n);
 571   G_TORAW(de->g, &b, x);
 572   GH_HASH(h, BBASE(&b), BLEN(&b));
 573   d->len += BLEN(&b);
 574   mp_drop(r);
 575   G_DESTROY(de->g, x);
 576   G_DESTROY(de->g, y);
 577   return (0);
 578 }
 579
 580 static const char *dh_enccheck(kem *k)
 581 {
 582   dh_encctx *de = (dh_encctx *)k;
 583   const char *e;
 584   if ((e = G_CHECK(de->g, &rand_global)) != 0)
 585     return (0);
 586   if (group_check(de->g, de->y))
 587     return ("public key not in subgroup");
 588   return (0);
 589 }
 590
 591 static void dh_encdestroy(kem *k)
 592 {
 593   dh_encctx *de = (dh_encctx *)k;
 594   G_DESTROY(de->g, de->y);
 595   mp_drop(de->x);
 596   G_DESTROYGROUP(de->g);
 597   DESTROY(de);
 598 }
 599
 600 static const kemops dh_encops = {
 601   dh_pubfetch, sizeof(dh_pub),
 602   dh_encinit, dh_encdoit, dh_enccheck, dh_encdestroy
 603 };
 604
 605 static const kemops bindh_encops = {
 606   dh_pubfetch, sizeof(dh_pub),
 607   bindh_encinit, dh_encdoit, dh_enccheck, dh_encdestroy
 608 };
 609
 610 static const kemops ec_encops = {
 611   ec_pubfetch, sizeof(ec_pub),
 612   ec_encinit, dh_encdoit, dh_enccheck, dh_encdestroy
 613 };
 614
 615 static kem *dh_decinit(key *k, void *kd)
 616 {
 617   dh_priv *dp = kd;
 618   dh_encctx *de = dh_doinit(k, &dp->dp, dp->y, group_prime, "prime");
 619   de->x = MP_COPY(dp->x);
 620   return (&de->k);
 621 }
 622
 623 static kem *bindh_decinit(key *k, void *kd)
 624 {
 625   dh_priv *dp = kd;
 626   dh_encctx *de = dh_doinit(k, &dp->dp, dp->y, group_binary, "binary");
 627   de->x = MP_COPY(dp->x);
 628   return (&de->k);
 629 }
 630
 631 static kem *ec_decinit(key *k, void *kd)
 632 {
 633   ec_priv *ep = kd;
 634   dh_encctx *de = ec_doinit(k, ep->cstr, &ep->p);
 635   de->x = MP_COPY(ep->x);
 636   return (&de->k);
 637 }
 638
 639 static int dh_decdoit(kem *k, dstr *d, ghash *h)
 640 {
 641   dh_encctx *de = (dh_encctx *)k;
 642   ge *x = G_CREATE(de->g);
 643   size_t n = de->g->noctets;
 644   void *p = xmalloc(n);
 645   buf b;
 646   int rc = -1;
 647
 648   buf_init(&b, d->buf, d->len);
 649   if (G_FROMRAW(de->g, &b, x) || group_check(de->g, x))
 650     goto done;
 651   G_EXP(de->g, x, x, de->x);
 652   buf_init(&b, p, n);
 653   G_TORAW(de->g, &b, x);
 654   GH_HASH(h, BBASE(&b), BLEN(&b));
 655   GH_HASH(h, d->buf, d->len);
 656   rc = 0;
 657 done:
 658   G_DESTROY(de->g, x);
 659   xfree(p);
 660   return (rc);
 661 }
 662
 663 static const kemops dh_decops = {
 664   dh_privfetch, sizeof(dh_priv),
 665   dh_decinit, dh_decdoit, dh_enccheck, dh_encdestroy
 666 };
 667
 668 static const kemops bindh_decops = {
 669   dh_privfetch, sizeof(dh_priv),
 670   bindh_decinit, dh_decdoit, dh_enccheck, dh_encdestroy
 671 };
 672
 673 static const kemops ec_decops = {
 674   ec_privfetch, sizeof(ec_priv),
 675   ec_decinit, dh_decdoit, dh_enccheck, dh_encdestroy
 676 };
 677
 678 /* --- X25519 and similar schemes --- */
 679
 680 #define XDHS(_)                                                         \
 681   _(x25519, X25519)                                                     \
 682   _(x448, X448)
 683
 684 #define XDHDEF(xdh, XDH)                                                \
 685                                                                         \
 686   static kem *xdh##_encinit(key *k, void *kd) { return (CREATE(kem)); } \
 687   static void xdh##_encdestroy(kem *k) { DESTROY(k); }                  \
 688                                                                         \
 689   static const char *xdh##_enccheck(kem *k)                             \
 690   {                                                                     \
 691     xdh##_pub *kd = k->kd;                                              \
 692                                                                         \
 693     if (kd->pub.sz != XDH##_PUBSZ)                                      \
 694       return ("incorrect " #XDH "public key length");                   \
 695     return (0);                                                         \
 696   }                                                                     \
 697                                                                         \
 698   static int xdh##_encdoit(kem *k, dstr *d, ghash *h)                   \
 699   {                                                                     \
 700     octet t[XDH##_KEYSZ], z[XDH##_OUTSZ];                               \
 701     xdh##_pub *kd = k->kd;                                              \
 702                                                                         \
 703     rand_get(RAND_GLOBAL, t, sizeof(t));                                \
 704     dstr_ensure(d, XDH##_PUBSZ);                                        \
 705     xdh((octet *)d->buf, t, xdh##_base);                                \
 706     xdh(z, t, kd->pub.k);                                               \
 707     d->len += XDH##_PUBSZ;                                              \
 708     GH_HASH(h, d->buf, XDH##_PUBSZ);                                    \
 709     GH_HASH(h, z, XDH##_OUTSZ);                                         \
 710     return (0);                                                         \
 711   }                                                                     \
 712                                                                         \
 713   static const char *xdh##_deccheck(kem *k)                             \
 714   {                                                                     \
 715     xdh##_priv *kd = k->kd;                                             \
 716                                                                         \
 717     if (kd->priv.sz != XDH##_KEYSZ)                                     \
 718       return ("incorrect " #XDH " private key length");                 \
 719     if (kd->pub.sz != XDH##_PUBSZ)                                      \
 720       return ("incorrect " #XDH " public key length");                  \
 721     return (0);                                                         \
 722   }                                                                     \
 723                                                                         \
 724   static int xdh##_decdoit(kem *k, dstr *d, ghash *h)                   \
 725   {                                                                     \
 726     octet z[XDH##_OUTSZ];                                               \
 727     xdh##_priv *kd = k->kd;                                             \
 728     int rc = -1;                                                        \
 729                                                                         \
 730     if (d->len != XDH##_PUBSZ) goto done;                               \
 731     xdh(z, kd->priv.k, (const octet *)d->buf);                          \
 732     GH_HASH(h, d->buf, XDH##_PUBSZ);                                    \
 733     GH_HASH(h, z, XDH##_OUTSZ);                                         \
 734     rc = 0;                                                             \
 735   done:                                                                 \
 736     return (rc);                                                        \
 737   }                                                                     \
 738                                                                         \
 739   static const kemops xdh##_encops = {                                  \
 740     xdh##_pubfetch, sizeof(xdh##_pub),                                  \
 741     xdh##_encinit, xdh##_encdoit, xdh##_enccheck, xdh##_encdestroy      \
 742   };                                                                    \
 743                                                                         \
 744   static const kemops xdh##_decops = {                                  \
 745     xdh##_privfetch, sizeof(xdh##_priv),                                \
 746     xdh##_encinit, xdh##_decdoit, xdh##_deccheck, xdh##_encdestroy      \
 747   };
 748
 749 XDHS(XDHDEF)
 750 #undef XDHDEF
 751
 752 /* --- Symmetric --- */
 753
 754 typedef struct symm_ctx {
 755   kem k;
 756   key_packdef kp;
 757   key_bin kb;
 758 } symm_ctx;
 759
 760 static kem *symm_init(key *k, void *kd)
 761 {
 762   symm_ctx *s;
 763   dstr d = DSTR_INIT;
 764   int err;
 765
 766   s = CREATE(symm_ctx);
 767
 768   key_fulltag(k, &d);
 769   s->kp.e = KENC_BINARY;
 770   s->kp.p = &s->kb;
 771   s->kp.kd = 0;
 772
 773   if ((err = key_unpack(&s->kp, kd, &d)) != 0) {
 774     die(EXIT_FAILURE, "failed to unpack symmetric key `%s': %s",
 775         d.buf, key_strerror(err));
 776   }
 777   dstr_destroy(&d);
 778   return (&s->k);
 779 }
 780
 781 static int symm_decdoit(kem *k, dstr *d, ghash *h)
 782 {
 783   symm_ctx *s = (symm_ctx *)k;
 784
 785   GH_HASH(h, s->kb.k, s->kb.sz);
 786   GH_HASH(h, d->buf, d->len);
 787   return (0);
 788 }
 789
 790 static int symm_encdoit(kem *k, dstr *d, ghash *h)
 791 {
 792   dstr_ensure(d, h->ops->c->hashsz);
 793   d->len += h->ops->c->hashsz;
 794   rand_get(RAND_GLOBAL, d->buf, d->len);
 795   return (symm_decdoit(k, d, h));
 796 }
 797
 798 static const char *symm_check(kem *k) { return (0); }
 799
 800 static void symm_destroy(kem *k)
 801   { symm_ctx *s = (symm_ctx *)k; key_unpackdone(&s->kp); }
 802
 803 static const kemops symm_encops = {
 804   0, 0,
 805   symm_init, symm_encdoit, symm_check, symm_destroy
 806 };
 807
 808 static const kemops symm_decops = {
 809   0, 0,
 810   symm_init, symm_decdoit, symm_check, symm_destroy
 811 };
 812
 813 /* --- The switch table --- */
 814
 815 const struct kemtab kemtab[] = {
 816   { "rsa",      &rsa_encops,    &rsa_decops },
 817   { "dh",       &dh_encops,     &dh_decops },
 818   { "bindh",    &bindh_encops,  &bindh_decops },
 819   { "ec",       &ec_encops,     &ec_decops },
 820 #define XDHTAB(xdh, XDH)                                                \
 821   { #xdh,       &xdh##_encops,  &xdh##_decops },
 822   XDHS(XDHTAB)
 823 #undef XDHTAB
 824   { "symm",     &symm_encops,   &symm_decops },
 825   { 0,          0,              0 }
 826 };
 827
 828 /* --- @getkem@ --- *
 829  *
 830  * Arguments:   @key *k@ = the key to load
 831  *              @const char *app@ = application name
 832  *              @int wantpriv@ = nonzero if we want to decrypt
 833  *              @bulk **bc@ = bulk crypto context to set up
 834  *
 835  * Returns:     A key-encapsulating thing.
 836  *
 837  * Use:         Loads a key.
 838  */
 839
 840 kem *getkem(key *k, const char *app, int wantpriv, bulk **bc)
 841 {
 842   const char *kalg, *halg = 0, *balg = 0;
 843   dstr d = DSTR_INIT;
 844   dstr t = DSTR_INIT;
 845   size_t n;
 846   char *p = 0;
 847   const char *q;
 848   kem *kk;
 849   const struct kemtab *kt;
 850   const kemops *ko;
 851   const struct bulktab *bt;
 852   const bulkops *bo;
 853   void *kd;
 854   int e;
 855   key_packdef *kp;
 856
 857   /* --- Setup stuff --- */
 858
 859   key_fulltag(k, &t);
 860
 861   /* --- Get the KEM name --- *
 862    *
 863    * Take the attribute if it's there; otherwise use the key type.
 864    */
 865
 866   n = strlen(app);
 867   if ((q = key_getattr(0, k, "kem")) != 0) {
 868     dstr_puts(&d, q);
 869     p = d.buf;
 870   } else if (STRNCMP(k->type, ==, app, n) && k->type[n] == '-') {
 871     dstr_puts(&d, k->type);
 872     p = d.buf + n + 1;
 873   } else
 874     die(EXIT_FAILURE, "no KEM for key `%s'", t.buf);
 875   kalg = p;
 876
 877   /* --- Grab the bulk encryption scheme --- *
 878    *
 879    * Grab it from the KEM if it's there, but override it from the attribute.
 880    */
 881
 882   if (p && (p = strchr(p, '/')) != 0) {
 883     *p++ = 0;
 884     balg = p;
 885   }
 886   if ((q = key_getattr(0, k, "bulk")) != 0)
 887     balg = q;
 888
 889   /* --- Grab the hash function --- */
 890
 891   if (p && (p = strchr(p, '/')) != 0) {
 892     *p++ = 0;
 893     halg = p;
 894   }
 895   if ((q = key_getattr(0, k, "hash")) != 0)
 896     halg = q;
 897
 898   /* --- Instantiate the KEM --- */
 899
 900   for (kt = kemtab; kt->name; kt++) {
 901     if (STRCMP(kt->name, ==, kalg))
 902       goto k_found;
 903   }
 904   die(EXIT_FAILURE, "key encapsulation mechanism `%s' not found in key `%s'",
 905       kalg, t.buf);
 906 k_found:;
 907   ko = wantpriv ? kt->decops : kt->encops;
 908   if (!ko->kf) {
 909     kd = k->k;
 910     key_incref(kd);
 911     kp = 0;
 912   } else {
 913     kd = xmalloc(ko->kdsz);
 914     kp = key_fetchinit(ko->kf, 0, kd);
 915     if ((e = key_fetch(kp, k)) != 0) {
 916       die(EXIT_FAILURE, "error fetching key `%s': %s",
 917           t.buf, key_strerror(e));
 918     }
 919   }
 920   kk = ko->init(k, kd);
 921   kk->kp = kp;
 922   kk->ops = ko;
 923   kk->kd = kd;
 924
 925   /* --- Set up the bulk crypto --- */
 926
 927   if (!halg)
 928     kk->hc = &rmd160;
 929   else if ((kk->hc = ghash_byname(halg)) == 0) {
 930     die(EXIT_FAILURE, "hash algorithm `%s' not found in key `%s'",
 931         halg, t.buf);
 932   }
 933
 934   if (!balg)
 935     bt = bulktab;
 936   else {
 937     for (bt = bulktab, bo = 0; bt->name; bt++) {
 938       if (STRCMP(balg, ==, bt->name))
 939         { balg = 0; goto b_found; }
 940       n = strlen(bt->name);
 941       if (STRNCMP(balg, ==, bt->name, n) && balg[n] == '-')
 942         { balg += n + 1; goto b_found; }
 943     }
 944     bt = bulktab;
 945   b_found:;
 946   }
 947   bo = wantpriv ? bt->decops : bt->encops;
 948   *bc = bo->init(k, balg, kk->hc->name);
 949   (*bc)->ops = bo;
 950
 951   dstr_reset(&d);
 952   if ((q = key_getattr(0, k, "kdf")) == 0) {
 953     dstr_putf(&d, "%s-mgf", kk->hc->name);
 954     q = d.buf;
 955   }
 956   if ((kk->cxc = gcipher_byname(q)) == 0) {
 957     die(EXIT_FAILURE, "encryption scheme (KDF) `%s' not found in key `%s'",
 958         q, t.buf);
 959   }
 960
 961   /* --- Tidy up --- */
 962
 963   dstr_destroy(&d);
 964   dstr_destroy(&t);
 965   return (kk);
 966 }
 967
 968 /* --- @setupkem@ --- *
 969  *
 970  * Arguments:   @kem *k@ = key-encapsulation thing
 971  *              @dstr *d@ = key-encapsulation data
 972  *              @bulk *bc@ = bulk crypto context to set up
 973  *
 974  * Returns:     Zero on success, nonzero on failure.
 975  *
 976  * Use:         Initializes all the various symmetric things from a KEM.
 977  */
 978
 979 int setupkem(kem *k, dstr *d, bulk *bc)
 980 {
 981   octet *kd;
 982   size_t n;
 983   ghash *h;
 984   int rc = -1;
 985
 986   h = GH_INIT(k->hc);
 987   if (k->ops->doit(k, d, h))
 988     goto done;
 989   n = keysz(GH_CLASS(h)->hashsz, k->cxc->keysz);
 990   if (!n)
 991     goto done;
 992   kd = GH_DONE(h, 0);
 993   k->cx = GC_INIT(k->cxc, kd, n);
 994   bc->ops->setup(bc, k->cx);
 995
 996   rc = 0;
 997 done:
 998   GH_DESTROY(h);
 999   return (rc);
1000 }
1001
1002 /* --- @freekem@ --- *
1003  *
1004  * Arguments:   @kem *k@ = key-encapsulation thing
1005  *
1006  * Returns:     ---
1007  *
1008  * Use:         Frees up a key-encapsulation thing.
1009  */
1010
1011 void freekem(kem *k)
1012 {
1013   if (!k->ops->kf)
1014     key_drop(k->kd);
1015   else {
1016     key_fetchdone(k->kp);
1017     xfree(k->kd);
1018   }
1019   GC_DESTROY(k->cx);
1020   k->ops->destroy(k);
1021 }
1022
1023 /*----- That's all, folks -------------------------------------------------*/