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

   1 /* -*-c-*-
   2  *
   3  * $Id$
   4  *
   5  * Catcrypt signatures
   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/report.h>
  35
  36 #include "rand.h"
  37 #include "sha.h"
  38 #include "has160.h"
  39
  40 #include "ec.h"
  41 #include "ec-keys.h"
  42 #include "dh.h"
  43 #include "gdsa.h"
  44 #include "gkcdsa.h"
  45 #include "rsa.h"
  46
  47 #include "cc.h"
  48
  49 /*----- Main code ---------------------------------------------------------*/
  50
  51 /* --- RSA PKCS1 --- */
  52
  53 typedef struct rsap1_sigctx {
  54   sig s;
  55   rsa_privctx rp;
  56   pkcs1 p1;
  57 } rsap1_sigctx;
  58
  59 static sig *rsap1_siginit(key *k, void *kd, const gchash *hc)
  60 {
  61   rsap1_sigctx *rs = CREATE(rsap1_sigctx);
  62   rsa_privcreate(&rs->rp, kd, &rand_global);
  63   rs->p1.r = &rand_global;
  64   rs->p1.ep = hc->name;
  65   rs->p1.epsz = strlen(hc->name) + 1;
  66   rs->s.h = 0;
  67   return (&rs->s);
  68 }
  69
  70 static int rsap1_sigdoit(sig *s, dstr *d)
  71 {
  72   rsap1_sigctx *rs = (rsap1_sigctx *)s;
  73   size_t n;
  74   mp *m = rsa_sign(&rs->rp, MP_NEW,
  75                    GH_DONE(s->h, 0), GH_CLASS(s->h)->hashsz,
  76                    pkcs1_sigencode, &rs->p1);
  77   if (!m) return (-1);
  78   n = mp_octets(rs->rp.rp->n); dstr_ensure(d, n); mp_storeb(m, d->buf, n);
  79   d->len += n; mp_drop(m);
  80   return (0);
  81 }
  82
  83 static const char *rsa_lengthcheck(mp *n)
  84 {
  85   if (mp_bits(n) < 1024) return ("key too short");
  86   return (0);
  87 }
  88
  89 static const char *rsap1_sigcheck(sig *s)
  90 {
  91   rsap1_sigctx *rs = (rsap1_sigctx *)s;
  92   const char *e;
  93   if ((e = rsa_lengthcheck(rs->rp.rp->n)) != 0) return (e);
  94   return (0);
  95 }
  96
  97 static void rsap1_sigdestroy(sig *s)
  98 {
  99   rsap1_sigctx *rs = (rsap1_sigctx *)s;
 100   rsa_privdestroy(&rs->rp);
 101   DESTROY(rs);
 102 }
 103
 104 static const sigops rsap1_sig = {
 105   rsa_privfetch, sizeof(rsa_priv),
 106   rsap1_siginit, rsap1_sigdoit, rsap1_sigcheck, rsap1_sigdestroy
 107 };
 108
 109 typedef struct rsap1_vrfctx {
 110   sig s;
 111   rsa_pubctx rp;
 112   pkcs1 p1;
 113 } rsap1_vrfctx;
 114
 115 static sig *rsap1_vrfinit(key *k, void *kd, const gchash *hc)
 116 {
 117   rsap1_vrfctx *rv = CREATE(rsap1_vrfctx);
 118   rsa_pubcreate(&rv->rp, kd);
 119   rv->p1.r = &rand_global;
 120   rv->p1.ep = hc->name;
 121   rv->p1.epsz = strlen(hc->name) + 1;
 122   rv->s.h = 0;
 123   return (&rv->s);
 124 }
 125
 126 static int rsap1_vrfdoit(sig *s, dstr *d)
 127 {
 128   rsap1_vrfctx *rv = (rsap1_vrfctx *)s;
 129   mp *m = mp_loadb(MP_NEW, d->buf, d->len);
 130   int rc = rsa_verify(&rv->rp, m,
 131                       GH_DONE(s->h, 0), GH_CLASS(s->h)->hashsz,
 132                       0, pkcs1_sigdecode, &rv->p1);
 133   mp_drop(m);
 134   return (rc);
 135 }
 136
 137 static const char *rsap1_vrfcheck(sig *s)
 138 {
 139   rsap1_vrfctx *rv = (rsap1_vrfctx *)s;
 140   const char *e;
 141   if ((e = rsa_lengthcheck(rv->rp.rp->n)) != 0) return (e);
 142   return (0);
 143 }
 144
 145 static void rsap1_vrfdestroy(sig *s)
 146 {
 147   rsap1_vrfctx *rv = (rsap1_vrfctx *)s;
 148   rsa_pubdestroy(&rv->rp);
 149   DESTROY(rv);
 150 }
 151
 152 static const sigops rsap1_vrf = {
 153   rsa_pubfetch, sizeof(rsa_pub),
 154   rsap1_vrfinit, rsap1_vrfdoit, rsap1_vrfcheck, rsap1_vrfdestroy
 155 };
 156
 157 /* --- RSA PSS --- */
 158
 159 static const gccipher *getmgf(key *k, const gchash *hc)
 160 {
 161   dstr d = DSTR_INIT;
 162   const gccipher *gc;
 163   const char *mm;
 164
 165   if ((mm = key_getattr(0, k, "mgf")) == 0) {
 166     dstr_putf(&d, "%s-mgf", hc->name);
 167     mm = d.buf;
 168   }
 169   if ((gc = gcipher_byname(mm)) == 0)
 170     die(EXIT_FAILURE, "unknown encryption scheme `%s'", mm);
 171   dstr_destroy(&d);
 172   return (gc);
 173 }
 174
 175 typedef struct rsapss_sigctx {
 176   sig s;
 177   rsa_privctx rp;
 178   pss p;
 179 } rsapss_sigctx;
 180
 181 static sig *rsapss_siginit(key *k, void *kd, const gchash *hc)
 182 {
 183   rsapss_sigctx *rs = CREATE(rsapss_sigctx);
 184   rsa_privcreate(&rs->rp, kd, &rand_global);
 185   rs->p.r = &rand_global;
 186   rs->p.cc = getmgf(k, hc);
 187   rs->p.ch = hc;
 188   rs->p.ssz = hc->hashsz;
 189   rsa_privdestroy(&rs->rp);
 190   return (&rs->s);
 191 }
 192
 193 static int rsapss_sigdoit(sig *s, dstr *d)
 194 {
 195   rsapss_sigctx *rs = (rsapss_sigctx *)s;
 196   size_t n;
 197   mp *m = rsa_sign(&rs->rp, MP_NEW,
 198                    GH_DONE(s->h, 0), GH_CLASS(s->h)->hashsz,
 199                    pss_encode, &rs->p);
 200   if (!m) return (-1);
 201   n = mp_octets(rs->rp.rp->n); dstr_ensure(d, n); mp_storeb(m, d->buf, n);
 202   d->len += n;  mp_drop(m);
 203   return (0);
 204 }
 205
 206 static const char *rsapss_sigcheck(sig *s)
 207 {
 208   rsapss_sigctx *rs = (rsapss_sigctx *)s;
 209   const char *e;
 210   if ((e = rsa_lengthcheck(rs->rp.rp->n)) != 0) return (e);
 211   return (0);
 212 }
 213
 214 static void rsapss_sigdestroy(sig *s)
 215 {
 216   rsapss_sigctx *rs = (rsapss_sigctx *)s;
 217   rsa_privdestroy(&rs->rp);
 218   DESTROY(rs);
 219 }
 220
 221 static const sigops rsapss_sig = {
 222   rsa_privfetch, sizeof(rsa_priv),
 223   rsapss_siginit, rsapss_sigdoit, rsapss_sigcheck, rsapss_sigdestroy
 224 };
 225
 226 typedef struct rsapss_vrfctx {
 227   sig s;
 228   rsa_pubctx rp;
 229   pss p;
 230 } rsapss_vrfctx;
 231
 232 static sig *rsapss_vrfinit(key *k, void *kd, const gchash *hc)
 233 {
 234   rsapss_vrfctx *rv = CREATE(rsapss_vrfctx);
 235   rsa_pubcreate(&rv->rp, kd);
 236   rv->p.r = &rand_global;
 237   rv->p.cc = getmgf(k, hc);
 238   rv->p.ch = hc;
 239   rv->p.ssz = hc->hashsz;
 240   return (&rv->s);
 241 }
 242
 243 static int rsapss_vrfdoit(sig *s, dstr *d)
 244 {
 245   rsapss_vrfctx *rv = (rsapss_vrfctx *)s;
 246   mp *m = mp_loadb(MP_NEW, d->buf, d->len);
 247   int rc = rsa_verify(&rv->rp, m,
 248                       GH_DONE(s->h, 0), GH_CLASS(s->h)->hashsz,
 249                       0, pss_decode, &rv->p);
 250   mp_drop(m);
 251   return (rc);
 252 }
 253
 254 static const char *rsapss_vrfcheck(sig *s)
 255 {
 256   rsapss_vrfctx *rv = (rsapss_vrfctx *)s;
 257   const char *e;
 258   if ((e = rsa_lengthcheck(rv->rp.rp->n)) != 0) return (e);
 259   return (0);
 260 }
 261
 262 static void rsapss_vrfdestroy(sig *s)
 263 {
 264   rsapss_vrfctx *rv = (rsapss_vrfctx *)s;
 265   rsa_pubdestroy(&rv->rp);
 266   DESTROY(rv);
 267 }
 268
 269 static const sigops rsapss_vrf = {
 270   rsa_pubfetch, sizeof(rsa_pub),
 271   rsapss_vrfinit, rsapss_vrfdoit, rsapss_vrfcheck, rsapss_vrfdestroy
 272 };
 273
 274 /* --- DSA and ECDSA --- */
 275
 276 typedef struct dsa_sigctx {
 277   sig s;
 278   gdsa g;
 279 } dsa_sigctx;
 280
 281 static void dsa_initcommon(dsa_sigctx *ds, const gchash *hc,
 282                            const char *ktag)
 283 {
 284   ds->g.r = &rand_global;
 285   ds->g.h = hc;
 286   ds->g.u = MP_NEW;
 287   ds->s.h = 0;
 288 }
 289
 290 static dsa_sigctx *dsa_doinit(key *k, const gprime_param *gp,
 291                               mp *y, const gchash *hc)
 292 {
 293   dsa_sigctx *ds = CREATE(dsa_sigctx);
 294   dstr t = DSTR_INIT;
 295
 296   key_fulltag(k, &t);
 297   if ((ds->g.g = group_prime(gp)) == 0)
 298     die(EXIT_FAILURE, "bad prime group in key `%s'", t.buf);
 299   ds->g.p = G_CREATE(ds->g.g);
 300   if (G_FROMINT(ds->g.g, ds->g.p, y))
 301     die(EXIT_FAILURE, "bad public key in key `%s'", t.buf);
 302   dsa_initcommon(ds, hc, t.buf);
 303   dstr_destroy(&t);
 304   return (ds);
 305 }
 306
 307 static dsa_sigctx *ecdsa_doinit(key *k, const char *cstr,
 308                                 ec *y, const gchash *hc)
 309 {
 310   dsa_sigctx *ds = CREATE(dsa_sigctx);
 311   ec_info ei;
 312   const char *e;
 313   dstr t = DSTR_INIT;
 314
 315   key_fulltag(k, &t);
 316   if ((e = ec_getinfo(&ei, cstr)) != 0)
 317     die(EXIT_FAILURE, "bad curve in key `%s': %s", t.buf, e);
 318   ds->g.g = group_ec(&ei);
 319   ds->g.p = G_CREATE(ds->g.g);
 320   if (G_FROMEC(ds->g.g, ds->g.p, y))
 321     die(EXIT_FAILURE, "bad public key in key `%s'", t.buf);
 322   dsa_initcommon(ds, hc, t.buf);
 323   dstr_destroy(&t);
 324   return (ds);
 325 }
 326
 327 static sig *dsa_siginit(key *k, void *kd, const gchash *hc)
 328 {
 329   dh_priv *dp = kd;
 330   dsa_sigctx *ds = dsa_doinit(k, &dp->dp, dp->y, hc);
 331   ds->g.u = MP_COPY(dp->x);
 332   return (&ds->s);
 333 }
 334
 335 static sig *ecdsa_siginit(key *k, void *kd, const gchash *hc)
 336 {
 337   ec_priv *ep = kd;
 338   dsa_sigctx *ds = ecdsa_doinit(k, ep->cstr, &ep->p, hc);
 339   ds->g.u = MP_COPY(ep->x);
 340   return (&ds->s);
 341 }
 342
 343 static int dsa_sigdoit(sig *s, dstr *d)
 344 {
 345   dsa_sigctx *ds = (dsa_sigctx *)s;
 346   gdsa_sig ss = GDSA_SIG_INIT;
 347   size_t n = mp_octets(ds->g.g->r);
 348
 349   gdsa_sign(&ds->g, &ss, GH_DONE(ds->s.h, 0), 0);
 350   dstr_ensure(d, 2 * n);
 351   mp_storeb(ss.r, d->buf, n);
 352   mp_storeb(ss.s, d->buf + n, n);
 353   d->len += 2 * n;
 354   mp_drop(ss.r); mp_drop(ss.s);
 355   return (0);
 356 }
 357
 358 static const char *dsa_sigcheck(sig *s)
 359 {
 360   dsa_sigctx *ds = (dsa_sigctx *)s;
 361   const char *e;
 362   if ((e = G_CHECK(ds->g.g, &rand_global)) != 0)
 363     return (0);
 364   if (group_check(ds->g.g, ds->g.p))
 365     return ("public key not in subgroup");
 366   return (0);
 367 }
 368
 369 static void dsa_sigdestroy(sig *s)
 370 {
 371   dsa_sigctx *ds = (dsa_sigctx *)s;
 372   G_DESTROY(ds->g.g, ds->g.p);
 373   mp_drop(ds->g.u);
 374   G_DESTROYGROUP(ds->g.g);
 375 }
 376
 377 static const sigops dsa_sig = {
 378   dh_privfetch, sizeof(dh_priv),
 379   dsa_siginit, dsa_sigdoit, dsa_sigcheck, dsa_sigdestroy
 380 };
 381
 382 static const sigops ecdsa_sig = {
 383   ec_privfetch, sizeof(ec_priv),
 384   ecdsa_siginit, dsa_sigdoit, dsa_sigcheck, dsa_sigdestroy
 385 };
 386
 387 static sig *dsa_vrfinit(key *k, void *kd, const gchash *hc)
 388 {
 389   dh_pub *dp = kd;
 390   dsa_sigctx *ds = dsa_doinit(k, &dp->dp, dp->y, hc);
 391   return (&ds->s);
 392 }
 393
 394 static sig *ecdsa_vrfinit(key *k, void *kd, const gchash *hc)
 395 {
 396   ec_pub *ep = kd;
 397   dsa_sigctx *ds = ecdsa_doinit(k, ep->cstr, &ep->p, hc);
 398   return (&ds->s);
 399 }
 400
 401 static int dsa_vrfdoit(sig *s, dstr *d)
 402 {
 403   dsa_sigctx *ds = (dsa_sigctx *)s;
 404   gdsa_sig ss;
 405   size_t n = d->len/2;
 406   int rc;
 407
 408   ss.r = mp_loadb(MP_NEW, d->buf, n);
 409   ss.s = mp_loadb(MP_NEW, d->buf + n, d->len - n);
 410   rc = gdsa_verify(&ds->g, &ss, GH_DONE(ds->s.h, 0));
 411   mp_drop(ss.r); mp_drop(ss.s);
 412   return (rc);
 413 }
 414
 415 static const sigops dsa_vrf = {
 416   dh_pubfetch, sizeof(dh_pub),
 417   dsa_vrfinit, dsa_vrfdoit, dsa_sigcheck, dsa_sigdestroy
 418 };
 419
 420 static const sigops ecdsa_vrf = {
 421   ec_pubfetch, sizeof(ec_pub),
 422   ecdsa_vrfinit, dsa_vrfdoit, dsa_sigcheck, dsa_sigdestroy
 423 };
 424
 425 /* --- KCDSA and ECKCDSA --- */
 426
 427 static void kcdsa_privkey(dsa_sigctx *ds, mp *x)
 428   { ds->g.u = mp_modinv(MP_NEW, x, ds->g.g->r); }
 429
 430 static void kcdsa_sethash(dsa_sigctx *ds, const gchash *hc)
 431   { ds->s.h = gkcdsa_beginhash(&ds->g); }
 432
 433 static sig *kcdsa_siginit(key *k, void *kd, const gchash *hc)
 434 {
 435   dh_priv *dp = kd;
 436   dsa_sigctx *ds = dsa_doinit(k, &dp->dp, dp->y, hc);
 437   kcdsa_privkey(ds, dp->x);
 438   kcdsa_sethash(ds, hc);
 439   return (&ds->s);
 440 }
 441
 442 static sig *eckcdsa_siginit(key *k, void *kd, const gchash *hc)
 443 {
 444   ec_priv *ep = kd;
 445   dsa_sigctx *ds = ecdsa_doinit(k, ep->cstr, &ep->p, hc);
 446   kcdsa_privkey(ds, ep->x);
 447   kcdsa_sethash(ds, hc);
 448   return (&ds->s);
 449 }
 450
 451 static int kcdsa_sigdoit(sig *s, dstr *d)
 452 {
 453   dsa_sigctx *ds = (dsa_sigctx *)s;
 454   gkcdsa_sig ss = GKCDSA_SIG_INIT;
 455   size_t hsz = ds->g.h->hashsz, n = mp_octets(ds->g.g->r);
 456
 457   gkcdsa_sign(&ds->g, &ss, GH_DONE(ds->s.h, 0), 0);
 458   dstr_ensure(d, hsz + n);
 459   memcpy(d->buf, ss.r, hsz);
 460   mp_storeb(ss.s, d->buf + hsz, n);
 461   d->len += hsz + n;
 462   xfree(ss.r); mp_drop(ss.s);
 463   return (0);
 464 }
 465
 466 static const sigops kcdsa_sig = {
 467   dh_privfetch, sizeof(dh_priv),
 468   kcdsa_siginit, kcdsa_sigdoit, dsa_sigcheck, dsa_sigdestroy
 469 };
 470
 471 static const sigops eckcdsa_sig = {
 472   ec_privfetch, sizeof(ec_priv),
 473   eckcdsa_siginit, kcdsa_sigdoit, dsa_sigcheck, dsa_sigdestroy
 474 };
 475
 476 static sig *kcdsa_vrfinit(key *k, void *kd, const gchash *hc)
 477 {
 478   dh_pub *dp = kd;
 479   dsa_sigctx *ds = dsa_doinit(k, &dp->dp, dp->y, hc);
 480   kcdsa_sethash(ds, hc);
 481   return (&ds->s);
 482 }
 483
 484 static sig *eckcdsa_vrfinit(key *k, void *kd, const gchash *hc)
 485 {
 486   ec_pub *ep = kd;
 487   dsa_sigctx *ds = ecdsa_doinit(k, ep->cstr, &ep->p, hc);
 488   kcdsa_sethash(ds, hc);
 489   return (&ds->s);
 490 }
 491
 492 static int kcdsa_vrfdoit(sig *s, dstr *d)
 493 {
 494   dsa_sigctx *ds = (dsa_sigctx *)s;
 495   gkcdsa_sig ss;
 496   size_t hsz = ds->g.h->hashsz, n = d->len - hsz;
 497   int rc;
 498
 499   if (d->len < hsz)
 500     return (-1);
 501   ss.r = (octet *)d->buf;
 502   ss.s = mp_loadb(MP_NEW, d->buf + hsz, n);
 503   rc = gkcdsa_verify(&ds->g, &ss, GH_DONE(ds->s.h, 0));
 504   mp_drop(ss.s);
 505   return (rc);
 506 }
 507
 508 static const sigops kcdsa_vrf = {
 509   dh_pubfetch, sizeof(dh_pub),
 510   kcdsa_vrfinit, kcdsa_vrfdoit, dsa_sigcheck, dsa_sigdestroy
 511 };
 512
 513 static const sigops eckcdsa_vrf = {
 514   ec_pubfetch, sizeof(ec_pub),
 515   eckcdsa_vrfinit, kcdsa_vrfdoit, dsa_sigcheck, dsa_sigdestroy
 516 };
 517
 518 /* --- The switch table --- */
 519
 520 const struct sigtab sigtab[] = {
 521   { "rsapkcs1", &rsap1_sig,     &rsap1_vrf,     &sha },
 522   { "rsapss",   &rsapss_sig,    &rsapss_vrf,    &sha },
 523   { "dsa",      &dsa_sig,       &dsa_vrf,       &sha },
 524   { "ecdsa",    &ecdsa_sig,     &ecdsa_vrf,     &sha },
 525   { "kcdsa",    &kcdsa_sig,     &kcdsa_vrf,     &has160 },
 526   { "eckcdsa",  &eckcdsa_sig,   &eckcdsa_vrf,   &has160 },
 527   { 0,          0,              0 }
 528 };
 529
 530 /* --- @getsig@ --- *
 531  *
 532  * Arguments:   @key *k@ = the key to load
 533  *              @const char *app@ = application name
 534  *              @int wantpriv@ = nonzero if we want to sign
 535  *
 536  * Returns:     A signature-making thing.
 537  *
 538  * Use:         Loads a key and starts hashing.
 539  */
 540
 541 sig *getsig(key *k, const char *app, int wantpriv)
 542 {
 543   const char *salg, *halg = 0;
 544   dstr d = DSTR_INIT;
 545   dstr t = DSTR_INIT;
 546   char *p = 0;
 547   const char *q;
 548   sig *s;
 549   size_t n;
 550   const struct sigtab *st;
 551   const sigops *so;
 552   const gchash *ch;
 553   void *kd;
 554   int e;
 555   key_packdef *kp;
 556
 557   /* --- Setup stuff --- */
 558
 559   key_fulltag(k, &t);
 560
 561   /* --- Get the signature algorithm --- *
 562    *
 563    * Take the attribute if it's there; otherwise use the key type.
 564    */
 565
 566   n = strlen(app);
 567   if ((q = key_getattr(0, k, "sig")) != 0) {
 568     dstr_puts(&d, q);
 569     p = d.buf;
 570   } else if (strncmp(k->type, app, n) == 0 && k->type[n] == '-') {
 571     dstr_puts(&d, k->type);
 572     p = d.buf + n + 1;
 573   } else
 574     die(EXIT_FAILURE, "no signature algorithm for key `%s'", t.buf);
 575
 576   /* --- Grab the hash algorithm --- *
 577    *
 578    * Grab it from the signature algorithm if it's there.  But override that
 579    * from the attribute.
 580    */
 581
 582   salg = p;
 583   if ((p = strchr(p, '/')) != 0) {
 584     *p++ = 0;
 585     halg = p;
 586   }
 587   if ((q = key_getattr(0, k, "hash")) != 0)
 588     halg = q;
 589
 590   /* --- Look up the algorithms in the table --- */
 591
 592   for (st = sigtab; st->name; st++) {
 593     if (strcmp(st->name, salg) == 0)
 594       goto s_found;
 595   }
 596   die(EXIT_FAILURE, "signature algorithm `%s' not found in key `%s'",
 597       salg, t.buf);
 598 s_found:;
 599   if (!halg)
 600     ch = st->ch;
 601   else {
 602     if ((ch = ghash_byname(halg)) == 0) {
 603       die(EXIT_FAILURE, "hash algorithm `%s' not found in key `%s'",
 604           halg, t.buf);
 605     }
 606   }
 607   so = wantpriv ? st->signops : st->verifyops;
 608
 609   /* --- Load the key --- */
 610
 611   kd = xmalloc(so->kdsz);
 612   kp = key_fetchinit(so->kf, 0, kd);
 613   if ((e = key_fetch(kp, k)) != 0)
 614     die(EXIT_FAILURE, "error fetching key `%s': %s", t.buf, key_strerror(e));
 615   s = so->init(k, kd, ch);
 616   if (!s->h)
 617     s->h = GH_INIT(ch);
 618   s->kp = kp;
 619   s->ops = so;
 620   s->kd = kd;
 621
 622   /* --- Free stuff up --- */
 623
 624   dstr_destroy(&d);
 625   dstr_destroy(&t);
 626   return (s);
 627 }
 628
 629 /* --- @freesig@ --- *
 630  *
 631  * Arguments:   @sig *s@ = signature-making thing
 632  *
 633  * Returns:     ---
 634  *
 635  * Use:         Frees up a signature-making thing
 636  */
 637
 638 void freesig(sig *s)
 639 {
 640   GH_DESTROY(s->h);
 641   key_fetchdone(s->kp);
 642   xfree(s->kd);
 643   s->ops->destroy(s);
 644 }
 645
 646 /*----- That's all, folks -------------------------------------------------*/