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/report.h>
  37 #include <mLib/sub.h>
  38
  39 #include "gaead.h"
  40 #include "mprand.h"
  41 #include "rand.h"
  42
  43 #include "ec.h"
  44 #include "ec-keys.h"
  45 #include "dh.h"
  46 #include "rsa.h"
  47 #include "x25519.h"
  48 #include "x448.h"
  49
  50 #include "rmd160.h"
  51 #include "blowfish-cbc.h"
  52 #include "chacha20-poly1305.h"
  53 #include "poly1305.h"
  54 #include "salsa20.h"
  55 #include "chacha.h"
  56
  57 #include "cc.h"
  58
  59 /*----- Bulk crypto -------------------------------------------------------*/
  60
  61 /* --- NaCl `secretbox' --- */
  62
  63 typedef struct naclbox_encctx {
  64   bulk b;
  65   const gccipher *cc;
  66   gcipher *c;
  67 } naclbox_encctx;
  68
  69 static bulk *naclbox_init(key *k, const char *calg, const char *halg)
  70 {
  71   naclbox_encctx *ctx = CREATE(naclbox_encctx);
  72   dstr t = DSTR_INIT;
  73   const char *q;
  74
  75   key_fulltag(k, &t);
  76
  77   if ((q = key_getattr(0, k, "cipher")) != 0) calg = q;
  78   if (!calg || strcmp(calg, "salsa20") == 0) ctx->cc = &salsa20;
  79   else if (strcmp(calg, "salsa20/12") == 0) ctx->cc = &salsa2012;
  80   else if (strcmp(calg, "salsa20/8") == 0) ctx->cc = &salsa208;
  81   else if (strcmp(calg, "chacha20") == 0) ctx->cc = &chacha20;
  82   else if (strcmp(calg, "chacha12") == 0) ctx->cc = &chacha12;
  83   else if (strcmp(calg, "chacha8") == 0) ctx->cc = &chacha8;
  84   else {
  85     die(EXIT_FAILURE,
  86         "unknown or inappropriate encryption scheme `%s' in key `%s'",
  87         calg, t.buf);
  88   }
  89
  90   dstr_destroy(&t);
  91   return (&ctx->b);
  92 }
  93
  94 static int naclbox_setup(bulk *b, gcipher *cx)
  95 {
  96   naclbox_encctx *ctx = (naclbox_encctx *)b;
  97   octet k[SALSA20_KEYSZ];
  98
  99   GC_ENCRYPT(cx, 0, k, sizeof(k));
 100   ctx->c = GC_INIT(ctx->cc, k, sizeof(k));
 101   return (0);
 102 }
 103
 104 static size_t naclbox_overhead(bulk *b) { return (POLY1305_TAGSZ); }
 105
 106 static void naclbox_destroy(bulk *b)
 107 {
 108   naclbox_encctx *ctx = (naclbox_encctx *)b;
 109
 110   GC_DESTROY(ctx->c);
 111   DESTROY(ctx);
 112 }
 113
 114 static const char *naclbox_encdoit(bulk *b, uint32 seq, buf *bb,
 115                                    const void *p, size_t sz)
 116 {
 117   naclbox_encctx *ctx = (naclbox_encctx *)b;
 118   octet t[32];
 119   poly1305_key ak;
 120   poly1305_ctx a;
 121   octet *tag, *ct;
 122
 123   STORE32(t, seq); STORE32(t + 4, 0); GC_SETIV(ctx->c, t);
 124   GC_ENCRYPT(ctx->c, 0, t, POLY1305_KEYSZ + POLY1305_MASKSZ);
 125   poly1305_keyinit(&ak, t, POLY1305_KEYSZ);
 126   poly1305_macinit(&a, &ak, t + POLY1305_KEYSZ);
 127
 128   tag = buf_get(bb, POLY1305_TAGSZ); assert(tag);
 129   ct = buf_get(bb, sz); assert(ct);
 130   GC_ENCRYPT(ctx->c, p, ct, sz);
 131   poly1305_hash(&a, ct, sz);
 132   poly1305_done(&a, tag);
 133   return (0);
 134 }
 135
 136 static const char *naclbox_decdoit(bulk *b, uint32 seq, buf *bb,
 137                                    const void *p, size_t sz)
 138 {
 139   naclbox_encctx *ctx = (naclbox_encctx *)b;
 140   buf bin;
 141   octet t[32];
 142   poly1305_key ak;
 143   poly1305_ctx a;
 144   octet *tag, *ct, *pt;
 145
 146   STORE32(t, seq); STORE32(t + 4, 0); GC_SETIV(ctx->c, t);
 147   GC_ENCRYPT(ctx->c, 0, t, POLY1305_KEYSZ + POLY1305_MASKSZ);
 148   poly1305_keyinit(&ak, t, POLY1305_KEYSZ);
 149   poly1305_macinit(&a, &ak, t + POLY1305_KEYSZ);
 150
 151   buf_init(&bin, (/*unconst*/ void *)p, sz);
 152   if ((tag = buf_get(&bin, POLY1305_TAGSZ)) == 0) return ("no tag");
 153   ct = BCUR(&bin); sz = BLEFT(&bin);
 154   poly1305_hash(&a, ct, sz);
 155   poly1305_done(&a, t);
 156   if (!ct_memeq(t, tag, POLY1305_TAGSZ)) return ("authentication failure");
 157   pt = buf_get(bb, sz); assert(pt);
 158   GC_DECRYPT(ctx->c, ct, pt, sz);
 159   return (0);
 160 }
 161
 162 static const bulkops naclbox_encops = {
 163   naclbox_init, naclbox_setup, naclbox_overhead,
 164   naclbox_encdoit, naclbox_destroy
 165 }, naclbox_decops = {
 166   naclbox_init, naclbox_setup, naclbox_overhead,
 167   naclbox_decdoit, naclbox_destroy
 168 };
 169
 170 /* --- Authenticated encryption schemes --- */
 171
 172 typedef struct aead_encctx {
 173   bulk b;
 174   const gcaead *aec;
 175   gaead_key *key;
 176   union { gaead_enc *enc; gaead_dec *dec; } ed;
 177   octet *t;
 178   size_t nsz, tsz;
 179 } aead_encctx;
 180
 181 static bulk *aead_init(key *k, const char *calg, const char *halg)
 182 {
 183   aead_encctx *ctx = CREATE(aead_encctx);
 184   const char *q;
 185   dstr t = DSTR_INIT;
 186
 187   key_fulltag(k, &t);
 188
 189   if ((q = key_getattr(0, k, "cipher")) != 0) calg = q;
 190   if (!calg) ctx->aec = &chacha20_poly1305;
 191   else if ((ctx->aec = gaead_byname(calg)) == 0)
 192     die(EXIT_FAILURE, "AEAD scheme `%s' not found in key `%s'",
 193         calg, t.buf);
 194
 195   ctx->key = 0;
 196   if ((ctx->nsz = keysz_pad(4, ctx->aec->noncesz)) == 0)
 197     die(EXIT_FAILURE, "no suitable nonce size for `%s'", calg);
 198   ctx->tsz = keysz(0, ctx->aec->tagsz);
 199
 200   dstr_destroy(&t);
 201   return (&ctx->b);
 202 }
 203
 204 static int aead_commonsetup(aead_encctx *ctx, gcipher *cx)
 205 {
 206   size_t ksz, n;
 207
 208   n = ksz = keysz(0, ctx->aec->keysz);
 209   if (n < ctx->nsz) n = ctx->nsz;
 210   if (n < ctx->tsz) n = ctx->tsz;
 211   ctx->t = xmalloc(n);
 212
 213   GC_ENCRYPT(cx, 0, ctx->t, ksz);
 214   ctx->key = GAEAD_KEY(ctx->aec, ctx->t, ksz);
 215   return (0);
 216 }
 217
 218 static size_t aead_overhead(bulk *b)
 219   { aead_encctx *ctx = (aead_encctx *)b; return (ctx->aec->ohd + ctx->tsz); }
 220
 221 static void aead_commondestroy(aead_encctx *ctx)
 222 {
 223   if (ctx->key) GAEAD_DESTROY(ctx->key);
 224   xfree(ctx->t);
 225   DESTROY(ctx);
 226 }
 227
 228 static int aead_encsetup(bulk *b, gcipher *cx)
 229 {
 230   aead_encctx *ctx = (aead_encctx *)b;
 231   ctx->ed.enc = 0; return (aead_commonsetup(ctx, cx));
 232 }
 233
 234 static const char *aead_encdoit(bulk *b, uint32 seq, buf *bb,
 235                                 const void *p, size_t sz)
 236 {
 237   aead_encctx *ctx = (aead_encctx *)b;
 238   octet *t;
 239   int rc;
 240
 241   memset(ctx->t + 4, 0, ctx->nsz - 4); STORE32_B(ctx->t, seq);
 242   if (!ctx->ed.enc)
 243     ctx->ed.enc = GAEAD_ENC(ctx->key, ctx->t, ctx->nsz, 0, sz, ctx->tsz);
 244   else
 245     GAEAD_REINIT(ctx->ed.enc, ctx->t, ctx->nsz, 0, sz, ctx->tsz);
 246   t = buf_get(bb, ctx->tsz); assert(t);
 247   rc = GAEAD_ENCRYPT(ctx->ed.enc, p, sz, bb); assert(rc >= 0);
 248   rc = GAEAD_DONE(ctx->ed.enc, 0, bb, t, ctx->tsz); assert(rc >= 0);
 249   return (0);
 250 }
 251
 252 static void aead_encdestroy(bulk *b)
 253 {
 254   aead_encctx *ctx = (aead_encctx *)b;
 255   if (ctx->ed.enc) GAEAD_DESTROY(ctx->ed.enc);
 256   aead_commondestroy(ctx);
 257 }
 258
 259 static int aead_decsetup(bulk *b, gcipher *cx)
 260 {
 261   aead_encctx *ctx = (aead_encctx *)b;
 262   ctx->ed.dec = 0; return (aead_commonsetup(ctx, cx));
 263 }
 264
 265 static const char *aead_decdoit(bulk *b, uint32 seq, buf *bb,
 266                                 const void *p, size_t sz)
 267 {
 268   aead_encctx *ctx = (aead_encctx *)b;
 269   buf bin;
 270   const octet *t;
 271   int rc;
 272
 273   memset(ctx->t + 4, 0, ctx->nsz - 4); STORE32_B(ctx->t, seq);
 274   if (!ctx->ed.dec)
 275     ctx->ed.dec = GAEAD_DEC(ctx->key, ctx->t, ctx->nsz, 0, sz, ctx->tsz);
 276   else
 277     GAEAD_REINIT(ctx->ed.enc, ctx->t, ctx->nsz, 0, sz, ctx->tsz);
 278
 279   buf_init(&bin, (/*unconst*/ void *)p, sz);
 280   t = buf_get(&bin, ctx->tsz); if (!t) return ("no tag");
 281   rc = GAEAD_DECRYPT(ctx->ed.dec, BCUR(&bin), BLEFT(&bin), bb);
 282   assert(rc >= 0);
 283   rc = GAEAD_DONE(ctx->ed.dec, 0, bb, t, ctx->tsz); assert(rc >= 0);
 284   if (!rc) return ("authentication failure");
 285   return (0);
 286 }
 287
 288 static void aead_decdestroy(bulk *b)
 289 {
 290   aead_encctx *ctx = (aead_encctx *)b;
 291   if (ctx->ed.dec) GAEAD_DESTROY(ctx->ed.dec);
 292   aead_commondestroy(ctx);
 293 }
 294
 295 static const struct bulkops aead_encops = {
 296   aead_init, aead_encsetup, aead_overhead,
 297   aead_encdoit, aead_encdestroy
 298 }, aead_decops = {
 299   aead_init, aead_decsetup, aead_overhead,
 300   aead_decdoit, aead_decdestroy
 301 };
 302
 303 /* --- Generic composition --- */
 304
 305 typedef struct gencomp_encctx {
 306   bulk b;
 307   const gccipher *cc;
 308   const gcmac *mc;
 309   gcipher *c, *cx;
 310   gmac *m;
 311   octet *t; size_t tsz;
 312 } gencomp_encctx;
 313
 314 static bulk *gencomp_init(key *k, const char *calg, const char *halg)
 315 {
 316   gencomp_encctx *ctx = CREATE(gencomp_encctx);
 317   const char *q;
 318   dstr d = DSTR_INIT, t = DSTR_INIT;
 319
 320   key_fulltag(k, &t);
 321
 322   if ((q = key_getattr(0, k, "cipher")) != 0) calg = q;
 323   if (!calg) ctx->cc = &blowfish_cbc;
 324   else if ((ctx->cc = gcipher_byname(calg)) == 0) {
 325     die(EXIT_FAILURE, "encryption scheme `%s' not found in key `%s'",
 326         calg, t.buf);
 327   }
 328
 329   dstr_reset(&d);
 330   if ((q = key_getattr(0, k, "mac")) == 0) {
 331     dstr_putf(&d, "%s-hmac", halg);
 332     q = d.buf;
 333   }
 334   if ((ctx->mc = gmac_byname(q)) == 0) {
 335     die(EXIT_FAILURE,
 336         "message authentication code `%s' not found in key `%s'",
 337         q, t.buf);
 338   }
 339
 340   return (&ctx->b);
 341 }
 342
 343 static int gencomp_setup(bulk *b, gcipher *cx)
 344 {
 345   gencomp_encctx *ctx = (gencomp_encctx *)b;
 346   size_t cn, mn, n;
 347   octet *kd;
 348
 349   ctx->cx = cx;
 350   n = ctx->cc->blksz;
 351   cn = keysz(0, ctx->cc->keysz); if (cn > n) n = cn;
 352   mn = keysz(0, ctx->mc->keysz); if (mn > n) n = mn;
 353   ctx->t = kd = xmalloc(n); ctx->tsz = n;
 354   GC_ENCRYPT(cx, 0, kd, cn);
 355   ctx->c = GC_INIT(ctx->cc, kd, cn);
 356   GC_ENCRYPT(cx, 0, kd, mn);
 357   ctx->m = GM_KEY(ctx->mc, kd, mn);
 358   return (0);
 359 }
 360
 361 static size_t gencomp_overhead(bulk *b)
 362 {
 363   gencomp_encctx *ctx = (gencomp_encctx *)b;
 364   return (ctx->cc->blksz + ctx->mc->hashsz); }
 365
 366 static void gencomp_destroy(bulk *b)
 367 {
 368   gencomp_encctx *ctx = (gencomp_encctx *)b;
 369
 370   GC_DESTROY(ctx->c);
 371   GC_DESTROY(ctx->m);
 372   xfree(ctx->t);
 373   DESTROY(ctx);
 374 }
 375
 376 static const char *gencomp_encdoit(bulk *b, uint32 seq, buf *bb,
 377                                    const void *p, size_t sz)
 378 {
 379   gencomp_encctx *ctx = (gencomp_encctx *)b;
 380   octet *tag, *ct;
 381   ghash *h = GM_INIT(ctx->m);
 382
 383   GH_HASHU32(h, seq);
 384   if (ctx->cc->blksz) {
 385     GC_ENCRYPT(ctx->cx, 0, ctx->t, ctx->cc->blksz);
 386     GC_SETIV(ctx->c, ctx->t);
 387   }
 388   tag = buf_get(bb, ctx->mc->hashsz); assert(tag);
 389   ct = buf_get(bb, sz); assert(ct);
 390   GC_ENCRYPT(ctx->c, p, ct, sz);
 391   GH_HASH(h, ct, sz);
 392   GH_DONE(h, tag);
 393   GH_DESTROY(h);
 394   return (0);
 395 }
 396
 397 static const char *gencomp_decdoit(bulk *b, uint32 seq, buf *bb,
 398                                    const void *p, size_t sz)
 399 {
 400   gencomp_encctx *ctx = (gencomp_encctx *)b;
 401   buf bin;
 402   const octet *tag, *ct;
 403   octet *pt;
 404   ghash *h;
 405   int ok;
 406
 407   buf_init(&bin, (/*unconst*/ void *)p, sz);
 408   if ((tag = buf_get(&bin, ctx->mc->hashsz)) == 0) return ("no tag");
 409   ct = BCUR(&bin); sz = BLEFT(&bin);
 410   pt = buf_get(bb, sz); assert(pt);
 411
 412   h = GM_INIT(ctx->m);
 413   GH_HASHU32(h, seq);
 414   GH_HASH(h, ct, sz);
 415   ok = ct_memeq(tag, GH_DONE(h, 0), ctx->mc->hashsz);
 416   GH_DESTROY(h);
 417   if (!ok) return ("authentication failure");
 418
 419   if (ctx->cc->blksz) {
 420     GC_ENCRYPT(ctx->cx, 0, ctx->t, ctx->cc->blksz);
 421     GC_SETIV(ctx->c, ctx->t);
 422   }
 423   GC_DECRYPT(ctx->c, ct, pt, sz);
 424   return (0);
 425 }
 426
 427 static const bulkops gencomp_encops = {
 428   gencomp_init, gencomp_setup, gencomp_overhead,
 429   gencomp_encdoit, gencomp_destroy
 430 }, gencomp_decops = {
 431   gencomp_init, gencomp_setup, gencomp_overhead,
 432   gencomp_decdoit, gencomp_destroy
 433 };
 434
 435 const struct bulktab bulktab[] = {
 436   { "gencomp",  &gencomp_encops,        &gencomp_decops },
 437   { "naclbox",  &naclbox_encops,        &naclbox_decops },
 438   { "aead",     &aead_encops,           &aead_decops },
 439   { 0,          0,                      0 }
 440 };
 441
 442 /*----- Key encapsulation -------------------------------------------------*/
 443
 444 /* --- RSA --- */
 445
 446 typedef struct rsa_encctx {
 447   kem k;
 448   rsa_pubctx rp;
 449 } rsa_encctx;
 450
 451 static kem *rsa_encinit(key *k, void *kd)
 452 {
 453   rsa_encctx *re = CREATE(rsa_encctx);
 454   rsa_pubcreate(&re->rp, kd);
 455   return (&re->k);
 456 }
 457
 458 static int rsa_encdoit(kem *k, dstr *d, ghash *h)
 459 {
 460   rsa_encctx *re = (rsa_encctx *)k;
 461   mp *x = mprand_range(MP_NEW, re->rp.rp->n, &rand_global, 0);
 462   mp *y = rsa_pubop(&re->rp, MP_NEW, x);
 463   size_t n = mp_octets(re->rp.rp->n);
 464   dstr_ensure(d, n);
 465   mp_storeb(x, d->buf, n);
 466   GH_HASH(h, d->buf, n);
 467   mp_storeb(y, d->buf, n);
 468   d->len += n;
 469   mp_drop(x);
 470   mp_drop(y);
 471   return (0);
 472 }
 473
 474 static const char *rsa_lengthcheck(mp *n)
 475 {
 476   if (mp_bits(n) < 1020) return ("key too short");
 477   return (0);
 478 }
 479
 480 static const char *rsa_enccheck(kem *k)
 481 {
 482   rsa_encctx *re = (rsa_encctx *)k;
 483   const char *e;
 484   if ((e = rsa_lengthcheck(re->rp.rp->n)) != 0) return (e);
 485   return (0);
 486 }
 487
 488 static void rsa_encdestroy(kem *k)
 489 {
 490   rsa_encctx *re = (rsa_encctx *)k;
 491   rsa_pubdestroy(&re->rp);
 492   DESTROY(re);
 493 }
 494
 495 static const kemops rsa_encops = {
 496   rsa_pubfetch, sizeof(rsa_pub),
 497   rsa_encinit, rsa_encdoit, rsa_enccheck, rsa_encdestroy
 498 };
 499
 500 typedef struct rsa_decctx {
 501   kem k;
 502   rsa_privctx rp;
 503 } rsa_decctx;
 504
 505 static kem *rsa_decinit(key *k, void *kd)
 506 {
 507   rsa_decctx *rd = CREATE(rsa_decctx);
 508   rsa_privcreate(&rd->rp, kd, &rand_global);
 509   return (&rd->k);
 510 }
 511
 512 static int rsa_decdoit(kem *k, dstr *d, ghash *h)
 513 {
 514   rsa_decctx *rd = (rsa_decctx *)k;
 515   mp *x = mp_loadb(MP_NEW, d->buf, d->len);
 516   size_t n;
 517   char *p;
 518
 519   if (MP_CMP(x, >=, rd->rp.rp->n)) {
 520     mp_drop(x);
 521     return (-1);
 522   }
 523   n = mp_octets(rd->rp.rp->n);
 524   p = xmalloc(n);
 525   x = rsa_privop(&rd->rp, x, x);
 526   mp_storeb(x, p, n);
 527   GH_HASH(h, p, n);
 528   mp_drop(x);
 529   xfree(p);
 530   return (0);
 531 }
 532
 533 static const char *rsa_deccheck(kem *k)
 534 {
 535   rsa_decctx *rd = (rsa_decctx *)k;
 536   const char *e;
 537   if ((e = rsa_lengthcheck(rd->rp.rp->n)) != 0) return (e);
 538   return (0);
 539 }
 540
 541 static void rsa_decdestroy(kem *k)
 542 {
 543   rsa_decctx *rd = (rsa_decctx *)k;
 544   rsa_privdestroy(&rd->rp);
 545   DESTROY(rd);
 546 }
 547
 548 static const kemops rsa_decops = {
 549   rsa_privfetch, sizeof(rsa_priv),
 550   rsa_decinit, rsa_decdoit, rsa_deccheck, rsa_decdestroy
 551 };
 552
 553 /* --- DH and EC --- */
 554
 555 typedef struct dh_encctx {
 556   kem k;
 557   group *g;
 558   mp *x;
 559   ge *y;
 560 } dh_encctx;
 561
 562 static dh_encctx *dh_doinit(key *k, const gprime_param *gp, mp *y,
 563                             group *(*makegroup)(const gprime_param *),
 564                             const char *what)
 565 {
 566   dh_encctx *de = CREATE(dh_encctx);
 567   dstr t = DSTR_INIT;
 568
 569   key_fulltag(k, &t);
 570   if ((de->g = makegroup(gp)) == 0)
 571     die(EXIT_FAILURE, "bad %s group in key `%s'", what, t.buf);
 572   de->x = MP_NEW;
 573   de->y = G_CREATE(de->g);
 574   if (G_FROMINT(de->g, de->y, y))
 575     die(EXIT_FAILURE, "bad public key `%s'", t.buf);
 576   dstr_destroy(&t);
 577   return (de);
 578 }
 579
 580 static dh_encctx *ec_doinit(key *k, const char *cstr, const ec *y)
 581 {
 582   dh_encctx *de = CREATE(dh_encctx);
 583   ec_info ei;
 584   const char *e;
 585   dstr t = DSTR_INIT;
 586
 587   key_fulltag(k, &t);
 588   if ((e = ec_getinfo(&ei, cstr)) != 0 ||
 589       (de->g = group_ec(&ei)) == 0)
 590     die(EXIT_FAILURE, "bad elliptic curve spec in key `%s': %s", t.buf, e);
 591   de->x = MP_NEW;
 592   de->y = G_CREATE(de->g);
 593   if (G_FROMEC(de->g, de->y, y))
 594     die(EXIT_FAILURE, "bad public curve point `%s'", t.buf);
 595   dstr_destroy(&t);
 596   return (de);
 597 }
 598
 599 static kem *dh_encinit(key *k, void *kd)
 600 {
 601   dh_pub *dp = kd;
 602   dh_encctx *de = dh_doinit(k, &dp->dp, dp->y, group_prime, "prime");
 603   return (&de->k);
 604 }
 605
 606 static kem *bindh_encinit(key *k, void *kd)
 607 {
 608   dh_pub *dp = kd;
 609   dh_encctx *de = dh_doinit(k, &dp->dp, dp->y, group_binary, "binary");
 610   return (&de->k);
 611 }
 612
 613 static kem *ec_encinit(key *k, void *kd)
 614 {
 615   ec_pub *ep = kd;
 616   dh_encctx *de = ec_doinit(k, ep->cstr, &ep->p);
 617   return (&de->k);
 618 }
 619
 620 static int dh_encdoit(kem *k, dstr *d, ghash *h)
 621 {
 622   dh_encctx *de = (dh_encctx *)k;
 623   mp *r = mprand_range(MP_NEW, de->g->r, &rand_global, 0);
 624   ge *x = G_CREATE(de->g);
 625   ge *y = G_CREATE(de->g);
 626   size_t n = de->g->noctets;
 627   buf b;
 628
 629   G_EXP(de->g, x, de->g->g, r);
 630   G_EXP(de->g, y, de->y, r);
 631   dstr_ensure(d, n);
 632   buf_init(&b, d->buf, n);
 633   G_TORAW(de->g, &b, y);
 634   GH_HASH(h, BBASE(&b), BLEN(&b));
 635   buf_init(&b, d->buf, n);
 636   G_TORAW(de->g, &b, x);
 637   GH_HASH(h, BBASE(&b), BLEN(&b));
 638   d->len += BLEN(&b);
 639   mp_drop(r);
 640   G_DESTROY(de->g, x);
 641   G_DESTROY(de->g, y);
 642   return (0);
 643 }
 644
 645 static const char *dh_enccheck(kem *k)
 646 {
 647   dh_encctx *de = (dh_encctx *)k;
 648   const char *e;
 649   if ((e = G_CHECK(de->g, &rand_global)) != 0)
 650     return (0);
 651   if (group_check(de->g, de->y))
 652     return ("public key not in subgroup");
 653   return (0);
 654 }
 655
 656 static void dh_encdestroy(kem *k)
 657 {
 658   dh_encctx *de = (dh_encctx *)k;
 659   G_DESTROY(de->g, de->y);
 660   mp_drop(de->x);
 661   G_DESTROYGROUP(de->g);
 662   DESTROY(de);
 663 }
 664
 665 static const kemops dh_encops = {
 666   dh_pubfetch, sizeof(dh_pub),
 667   dh_encinit, dh_encdoit, dh_enccheck, dh_encdestroy
 668 };
 669
 670 static const kemops bindh_encops = {
 671   dh_pubfetch, sizeof(dh_pub),
 672   bindh_encinit, dh_encdoit, dh_enccheck, dh_encdestroy
 673 };
 674
 675 static const kemops ec_encops = {
 676   ec_pubfetch, sizeof(ec_pub),
 677   ec_encinit, dh_encdoit, dh_enccheck, dh_encdestroy
 678 };
 679
 680 static kem *dh_decinit(key *k, void *kd)
 681 {
 682   dh_priv *dp = kd;
 683   dh_encctx *de = dh_doinit(k, &dp->dp, dp->y, group_prime, "prime");
 684   de->x = MP_COPY(dp->x);
 685   return (&de->k);
 686 }
 687
 688 static kem *bindh_decinit(key *k, void *kd)
 689 {
 690   dh_priv *dp = kd;
 691   dh_encctx *de = dh_doinit(k, &dp->dp, dp->y, group_binary, "binary");
 692   de->x = MP_COPY(dp->x);
 693   return (&de->k);
 694 }
 695
 696 static kem *ec_decinit(key *k, void *kd)
 697 {
 698   ec_priv *ep = kd;
 699   dh_encctx *de = ec_doinit(k, ep->cstr, &ep->p);
 700   de->x = MP_COPY(ep->x);
 701   return (&de->k);
 702 }
 703
 704 static int dh_decdoit(kem *k, dstr *d, ghash *h)
 705 {
 706   dh_encctx *de = (dh_encctx *)k;
 707   ge *x = G_CREATE(de->g);
 708   size_t n = de->g->noctets;
 709   void *p = xmalloc(n);
 710   buf b;
 711   int rc = -1;
 712
 713   buf_init(&b, d->buf, d->len);
 714   if (G_FROMRAW(de->g, &b, x) || group_check(de->g, x))
 715     goto done;
 716   G_EXP(de->g, x, x, de->x);
 717   buf_init(&b, p, n);
 718   G_TORAW(de->g, &b, x);
 719   GH_HASH(h, BBASE(&b), BLEN(&b));
 720   GH_HASH(h, d->buf, d->len);
 721   rc = 0;
 722 done:
 723   G_DESTROY(de->g, x);
 724   xfree(p);
 725   return (rc);
 726 }
 727
 728 static const kemops dh_decops = {
 729   dh_privfetch, sizeof(dh_priv),
 730   dh_decinit, dh_decdoit, dh_enccheck, dh_encdestroy
 731 };
 732
 733 static const kemops bindh_decops = {
 734   dh_privfetch, sizeof(dh_priv),
 735   bindh_decinit, dh_decdoit, dh_enccheck, dh_encdestroy
 736 };
 737
 738 static const kemops ec_decops = {
 739   ec_privfetch, sizeof(ec_priv),
 740   ec_decinit, dh_decdoit, dh_enccheck, dh_encdestroy
 741 };
 742
 743 /* --- X25519 and similar schemes --- */
 744
 745 #define XDHS(_)                                                         \
 746   _(x25519, X25519)                                                     \
 747   _(x448, X448)
 748
 749 #define XDHDEF(xdh, XDH)                                                \
 750                                                                         \
 751   static kem *xdh##_encinit(key *k, void *kd) { return (CREATE(kem)); } \
 752   static void xdh##_encdestroy(kem *k) { DESTROY(k); }                  \
 753                                                                         \
 754   static const char *xdh##_enccheck(kem *k)                             \
 755   {                                                                     \
 756     xdh##_pub *kd = k->kd;                                              \
 757                                                                         \
 758     if (kd->pub.sz != XDH##_PUBSZ)                                      \
 759       return ("incorrect " #XDH "public key length");                   \
 760     return (0);                                                         \
 761   }                                                                     \
 762                                                                         \
 763   static int xdh##_encdoit(kem *k, dstr *d, ghash *h)                   \
 764   {                                                                     \
 765     octet t[XDH##_KEYSZ], z[XDH##_OUTSZ];                               \
 766     xdh##_pub *kd = k->kd;                                              \
 767                                                                         \
 768     rand_get(RAND_GLOBAL, t, sizeof(t));                                \
 769     dstr_ensure(d, XDH##_PUBSZ);                                        \
 770     xdh((octet *)d->buf, t, xdh##_base);                                \
 771     xdh(z, t, kd->pub.k);                                               \
 772     d->len += XDH##_PUBSZ;                                              \
 773     GH_HASH(h, d->buf, XDH##_PUBSZ);                                    \
 774     GH_HASH(h, z, XDH##_OUTSZ);                                         \
 775     return (0);                                                         \
 776   }                                                                     \
 777                                                                         \
 778   static const char *xdh##_deccheck(kem *k)                             \
 779   {                                                                     \
 780     xdh##_priv *kd = k->kd;                                             \
 781                                                                         \
 782     if (kd->priv.sz != XDH##_KEYSZ)                                     \
 783       return ("incorrect " #XDH " private key length");                 \
 784     if (kd->pub.sz != XDH##_PUBSZ)                                      \
 785       return ("incorrect " #XDH " public key length");                  \
 786     return (0);                                                         \
 787   }                                                                     \
 788                                                                         \
 789   static int xdh##_decdoit(kem *k, dstr *d, ghash *h)                   \
 790   {                                                                     \
 791     octet z[XDH##_OUTSZ];                                               \
 792     xdh##_priv *kd = k->kd;                                             \
 793     int rc = -1;                                                        \
 794                                                                         \
 795     if (d->len != XDH##_PUBSZ) goto done;                               \
 796     xdh(z, kd->priv.k, (const octet *)d->buf);                          \
 797     GH_HASH(h, d->buf, XDH##_PUBSZ);                                    \
 798     GH_HASH(h, z, XDH##_OUTSZ);                                         \
 799     rc = 0;                                                             \
 800   done:                                                                 \
 801     return (rc);                                                        \
 802   }                                                                     \
 803                                                                         \
 804   static const kemops xdh##_encops = {                                  \
 805     xdh##_pubfetch, sizeof(xdh##_pub),                                  \
 806     xdh##_encinit, xdh##_encdoit, xdh##_enccheck, xdh##_encdestroy      \
 807   };                                                                    \
 808                                                                         \
 809   static const kemops xdh##_decops = {                                  \
 810     xdh##_privfetch, sizeof(xdh##_priv),                                \
 811     xdh##_encinit, xdh##_decdoit, xdh##_deccheck, xdh##_encdestroy      \
 812   };
 813
 814 XDHS(XDHDEF)
 815 #undef XDHDEF
 816
 817 /* --- Symmetric --- */
 818
 819 typedef struct symm_ctx {
 820   kem k;
 821   key_packdef kp;
 822   key_bin kb;
 823 } symm_ctx;
 824
 825 static kem *symm_init(key *k, void *kd)
 826 {
 827   symm_ctx *s;
 828   dstr d = DSTR_INIT;
 829   int err;
 830
 831   s = CREATE(symm_ctx);
 832
 833   key_fulltag(k, &d);
 834   s->kp.e = KENC_BINARY;
 835   s->kp.p = &s->kb;
 836   s->kp.kd = 0;
 837
 838   if ((err = key_unpack(&s->kp, kd, &d)) != 0) {
 839     die(EXIT_FAILURE, "failed to unpack symmetric key `%s': %s",
 840         d.buf, key_strerror(err));
 841   }
 842   dstr_destroy(&d);
 843   return (&s->k);
 844 }
 845
 846 static int symm_decdoit(kem *k, dstr *d, ghash *h)
 847 {
 848   symm_ctx *s = (symm_ctx *)k;
 849
 850   GH_HASH(h, s->kb.k, s->kb.sz);
 851   GH_HASH(h, d->buf, d->len);
 852   return (0);
 853 }
 854
 855 static int symm_encdoit(kem *k, dstr *d, ghash *h)
 856 {
 857   dstr_ensure(d, h->ops->c->hashsz);
 858   d->len += h->ops->c->hashsz;
 859   rand_get(RAND_GLOBAL, d->buf, d->len);
 860   return (symm_decdoit(k, d, h));
 861 }
 862
 863 static const char *symm_check(kem *k) { return (0); }
 864
 865 static void symm_destroy(kem *k)
 866   { symm_ctx *s = (symm_ctx *)k; key_unpackdone(&s->kp); }
 867
 868 static const kemops symm_encops = {
 869   0, 0,
 870   symm_init, symm_encdoit, symm_check, symm_destroy
 871 };
 872
 873 static const kemops symm_decops = {
 874   0, 0,
 875   symm_init, symm_decdoit, symm_check, symm_destroy
 876 };
 877
 878 /* --- The switch table --- */
 879
 880 const struct kemtab kemtab[] = {
 881   { "rsa",      &rsa_encops,    &rsa_decops },
 882   { "dh",       &dh_encops,     &dh_decops },
 883   { "bindh",    &bindh_encops,  &bindh_decops },
 884   { "ec",       &ec_encops,     &ec_decops },
 885 #define XDHTAB(xdh, XDH)                                                \
 886   { #xdh,       &xdh##_encops,  &xdh##_decops },
 887   XDHS(XDHTAB)
 888 #undef XDHTAB
 889   { "symm",     &symm_encops,   &symm_decops },
 890   { 0,          0,              0 }
 891 };
 892
 893 /* --- @getkem@ --- *
 894  *
 895  * Arguments:   @key *k@ = the key to load
 896  *              @const char *app@ = application name
 897  *              @int wantpriv@ = nonzero if we want to decrypt
 898  *              @bulk **bc@ = bulk crypto context to set up
 899  *
 900  * Returns:     A key-encapsulating thing.
 901  *
 902  * Use:         Loads a key.
 903  */
 904
 905 kem *getkem(key *k, const char *app, int wantpriv, bulk **bc)
 906 {
 907   const char *kalg, *halg = 0, *balg = 0;
 908   dstr d = DSTR_INIT;
 909   dstr t = DSTR_INIT;
 910   size_t n;
 911   char *p = 0;
 912   const char *q;
 913   kem *kk;
 914   const struct kemtab *kt;
 915   const kemops *ko;
 916   const struct bulktab *bt;
 917   const bulkops *bo;
 918   void *kd;
 919   int e;
 920   key_packdef *kp;
 921
 922   /* --- Setup stuff --- */
 923
 924   key_fulltag(k, &t);
 925
 926   /* --- Get the KEM name --- *
 927    *
 928    * Take the attribute if it's there; otherwise use the key type.
 929    */
 930
 931   n = strlen(app);
 932   if ((q = key_getattr(0, k, "kem")) != 0) {
 933     dstr_puts(&d, q);
 934     p = d.buf;
 935   } else if (strncmp(k->type, app, n) == 0 && k->type[n] == '-') {
 936     dstr_puts(&d, k->type);
 937     p = d.buf + n + 1;
 938   } else
 939     die(EXIT_FAILURE, "no KEM for key `%s'", t.buf);
 940   kalg = p;
 941
 942   /* --- Grab the bulk encryption scheme --- *
 943    *
 944    * Grab it from the KEM if it's there, but override it from the attribute.
 945    */
 946
 947   if (p && (p = strchr(p, '/')) != 0) {
 948     *p++ = 0;
 949     balg = p;
 950   }
 951   if ((q = key_getattr(0, k, "bulk")) != 0)
 952     balg = q;
 953
 954   /* --- Grab the hash function --- */
 955
 956   if (p && (p = strchr(p, '/')) != 0) {
 957     *p++ = 0;
 958     halg = p;
 959   }
 960   if ((q = key_getattr(0, k, "hash")) != 0)
 961     halg = q;
 962
 963   /* --- Instantiate the KEM --- */
 964
 965   for (kt = kemtab; kt->name; kt++) {
 966     if (strcmp(kt->name, kalg) == 0)
 967       goto k_found;
 968   }
 969   die(EXIT_FAILURE, "key encapsulation mechanism `%s' not found in key `%s'",
 970       kalg, t.buf);
 971 k_found:;
 972   ko = wantpriv ? kt->decops : kt->encops;
 973   if (!ko->kf) {
 974     kd = k->k;
 975     key_incref(kd);
 976     kp = 0;
 977   } else {
 978     kd = xmalloc(ko->kdsz);
 979     kp = key_fetchinit(ko->kf, 0, kd);
 980     if ((e = key_fetch(kp, k)) != 0) {
 981       die(EXIT_FAILURE, "error fetching key `%s': %s",
 982           t.buf, key_strerror(e));
 983     }
 984   }
 985   kk = ko->init(k, kd);
 986   kk->kp = kp;
 987   kk->ops = ko;
 988   kk->kd = kd;
 989
 990   /* --- Set up the bulk crypto --- */
 991
 992   if (!halg)
 993     kk->hc = &rmd160;
 994   else if ((kk->hc = ghash_byname(halg)) == 0) {
 995     die(EXIT_FAILURE, "hash algorithm `%s' not found in key `%s'",
 996         halg, t.buf);
 997   }
 998
 999   if (!balg)
1000     bt = bulktab;
1001   else {
1002     for (bt = bulktab, bo = 0; bt->name; bt++) {
1003       if (strcmp(balg, bt->name) == 0)
1004         { balg = 0; goto b_found; }
1005       n = strlen(bt->name);
1006       if (strncmp(balg, bt->name, n) == 0 && balg[n] == '-')
1007         { balg += n + 1; goto b_found; }
1008     }
1009     bt = bulktab;
1010   b_found:;
1011   }
1012   bo = wantpriv ? bt->decops : bt->encops;
1013   *bc = bo->init(k, balg, kk->hc->name);
1014   (*bc)->ops = bo;
1015
1016   dstr_reset(&d);
1017   if ((q = key_getattr(0, k, "kdf")) == 0) {
1018     dstr_putf(&d, "%s-mgf", kk->hc->name);
1019     q = d.buf;
1020   }
1021   if ((kk->cxc = gcipher_byname(q)) == 0) {
1022     die(EXIT_FAILURE, "encryption scheme (KDF) `%s' not found in key `%s'",
1023         q, t.buf);
1024   }
1025
1026   /* --- Tidy up --- */
1027
1028   dstr_destroy(&d);
1029   dstr_destroy(&t);
1030   return (kk);
1031 }
1032
1033 /* --- @setupkem@ --- *
1034  *
1035  * Arguments:   @kem *k@ = key-encapsulation thing
1036  *              @dstr *d@ = key-encapsulation data
1037  *              @bulk *bc@ = bulk crypto context to set up
1038  *
1039  * Returns:     Zero on success, nonzero on failure.
1040  *
1041  * Use:         Initializes all the various symmetric things from a KEM.
1042  */
1043
1044 int setupkem(kem *k, dstr *d, bulk *bc)
1045 {
1046   octet *kd;
1047   size_t n;
1048   ghash *h;
1049   int rc = -1;
1050
1051   h = GH_INIT(k->hc);
1052   if (k->ops->doit(k, d, h))
1053     goto done;
1054   n = keysz(GH_CLASS(h)->hashsz, k->cxc->keysz);
1055   if (!n)
1056     goto done;
1057   kd = GH_DONE(h, 0);
1058   k->cx = GC_INIT(k->cxc, kd, n);
1059   bc->ops->setup(bc, k->cx);
1060
1061   rc = 0;
1062 done:
1063   GH_DESTROY(h);
1064   return (rc);
1065 }
1066
1067 /* --- @freekem@ --- *
1068  *
1069  * Arguments:   @kem *k@ = key-encapsulation thing
1070  *
1071  * Returns:     ---
1072  *
1073  * Use:         Frees up a key-encapsulation thing.
1074  */
1075
1076 void freekem(kem *k)
1077 {
1078   if (!k->ops->kf)
1079     key_drop(k->kd);
1080   else {
1081     key_fetchdone(k->kp);
1082     xfree(k->kd);
1083   }
1084   GC_DESTROY(k->cx);
1085   k->ops->destroy(k);
1086 }
1087
1088 /*----- That's all, folks -------------------------------------------------*/