mdw@git.distorted.org.uk Git - catacomb/blob - pub/gkcdsa.c

   1 /* -*-c-*-
   2  *
   3  * Generalized version of KCDSA
   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 #include "dsa.h"
  31 #include "gkcdsa.h"
  32 #include "group.h"
  33 #include "ghash.h"
  34 #include "mpbarrett.h"
  35 #include "mprand.h"
  36
  37 /*----- Main code ---------------------------------------------------------*/
  38
  39 /* --- @gkcdsa_beginhash@ --- *
  40  *
  41  * Arguments:   @const gkcdsa *c@ = pointer to the context structure
  42  *
  43  * Returns:     A hashing context for you to hash the message.
  44  *
  45  * Use:         Initializes a hash function correctly for you to hash a
  46  *              message.  Requires @h@, @g@ and @p@.
  47  */
  48
  49 ghash *gkcdsa_beginhash(const gkcdsa *c)
  50 {
  51   ghash *h = GH_INIT(c->h);
  52   mp *v = G_TOINT(c->g, MP_NEW, c->p);
  53   size_t sz = c->h->bufsz;
  54   void *p = xmalloc(sz);
  55   if (/*ouch*/ !v) memset(p, 0, sz);
  56   else mp_storeb(v, p, sz);
  57   GH_HASH(h, p, sz);
  58   mp_drop(v); xfree(p);
  59   return (h);
  60 }
  61
  62 /* --- @gkcdsa_endhash@ --- *
  63  *
  64  * Arguments:   @const gkcdsa *c@ = pointer to the context structure
  65  *              @ghash *h@ = the hashing context
  66  *
  67  * Returns:     ---
  68  *
  69  * Use:         Does any final thing that KCDSA wants to do when hashing a
  70  *              message.  (Actually, there's nothing.)  The hashing context
  71  *              isn't finalized.
  72  */
  73
  74 void gkcdsa_endhash(const gkcdsa *c, ghash *h) { ; }
  75
  76 /* --- @hashge@ --- *
  77  *
  78  * Arguments:   @group *g@ = abstract group
  79  *              @const gchash *hc@ = hash class
  80  *              @ge *w@ = a group element
  81  *
  82  * Returns:     A hash context, with the hash of @w@ in it.
  83  */
  84
  85 static ghash *hashge(group *g, const gchash *hc, ge *w)
  86 {
  87   ghash *h;
  88   size_t sz;
  89   void *p;
  90   buf b;
  91   int rc;
  92
  93   sz = hc->hashsz;
  94   if (sz < g->noctets)
  95     sz = g->noctets;
  96   p = xmalloc(sz);
  97   buf_init(&b, p, sz);
  98   rc = G_TORAW(g, &b, w);
  99   assert(rc == 0);
 100   h = GH_INIT(hc);
 101   GH_HASH(h, BBASE(&b), BLEN(&b));
 102   xfree(p);
 103   return (h);
 104 }
 105
 106 /* --- @gkcdsa_sign@ --- *
 107  *
 108  * Arguments:   @const gkcdsa *c@ = my context structure
 109  *              @gkcdsa_sig *s@ = where to put the signature (initialized)
 110  *              @const void *m@ = pointer to message hash
 111  *              @mp *k@ = random exponent for this message or null
 112  *
 113  * Returns:     ---
 114  *
 115  * Use:         Signs a message.  Requires @g@, @u@, @h@, and @r@ if @k@ is
 116  *              null.  This is a better idea than inventing @k@ yourself.
 117  */
 118
 119 void gkcdsa_sign(const gkcdsa *c, gkcdsa_sig *s, const void *m, mp *k)
 120 {
 121   group *g = c->g;
 122   mp *x, *y;
 123   ge *z = G_CREATE(g);
 124   size_t hsz = c->h->hashsz;
 125   ghash *h;
 126
 127   if (k) { MP_COPY(k); goto have_k; }
 128 new_k:
 129   k = dsa_nonce(k, g->r, c->u, m, c->h, c->r);
 130 have_k:
 131   if (MP_ZEROP(k)) goto new_k;
 132   G_EXP(g, z, g->g, k);
 133   if (!s->r) s->r = xmalloc(hsz);
 134   h = hashge(g, c->h, z); GH_DONE(h, s->r);
 135
 136   x = mp_loadb(s->s, m, hsz);
 137   y = mp_loadb(MP_NEW, s->r, hsz);
 138   x = mp_xor(x, x, y);
 139   mp_div(0, &x, x, g->r);
 140   x = mp_sub(x, g->r, x);
 141   x = mp_add(x, x, k);
 142   if (MP_CMP(x, >=, g->r)) x = mp_sub(x, x, g->r);
 143   x = mp_mul(x, x, c->u); mp_div(0, &x, x, g->r);
 144   s->s = x;
 145   mp_drop(k); mp_drop(y); GH_DESTROY(h); G_DESTROY(g, z);
 146 }
 147
 148 /* --- @gkcdsa_verify@ --- *
 149  *
 150  * Arguments:   @const gkcdsa *c@ = my context structure
 151  *              @const gkcdsa_sig *s@ = the signature to verify
 152  *              @const void *m@ = pointer to message hash
 153  *
 154  * Returns:     Zero if OK, negative on failure.
 155  *
 156  * Use:         Checks a signature on a message,  Requires @g@, @p@, @h@.
 157  */
 158
 159 int gkcdsa_verify(const gkcdsa *c, const gkcdsa_sig *s, const void *m)
 160 {
 161   group *g = c->g;
 162   size_t hsz = c->h->hashsz;
 163   group_expfactor e[2];
 164   mp *x, *y;
 165   ghash *h;
 166   ge *z;
 167   octet *p;
 168   int rc = -1;
 169
 170   if (MP_CMP(s->s, <, MP_ONE) || MP_CMP(s->s, >=, g->r))
 171     return (-1);
 172   x = mp_loadb(MP_NEW, m, hsz); y = mp_loadb(MP_NEW, s->r, hsz);
 173   x = mp_xor(x, x, y); mp_div(0, &x, x, g->r);
 174   e[0].base = c->p; e[0].exp = s->s;
 175   e[1].base = g->g; e[1].exp = x;
 176   z = G_CREATE(g); G_MEXP(g, z, e, 2);
 177   h = hashge(g, c->h, z); p = GH_DONE(h, 0);
 178   if (memcmp(p, s->r, hsz) == 0) rc = 0;
 179   mp_drop(x); mp_drop(y); G_DESTROY(g, z); GH_DESTROY(h);
 180   return (rc);
 181 }
 182
 183 /*----- Test rig ----------------------------------------------------------*/
 184
 185 #ifdef TEST_RIG
 186
 187 #include "rand.h"
 188
 189 static group *getgroup(const char *p) {
 190   group *g; qd_parse qd;
 191   qd.p = p; qd.e = 0; g = group_parse(&qd);
 192   if (g && !qd_eofp(&qd)) { G_DESTROYGROUP(g); g = 0; qd.e = "junk at eof"; }
 193   if (!g) {
 194     fprintf(stderr, "bad group string `%.*s|%s': %s\n",
 195             (int)(qd.p - p), p, qd.p, qd.e);
 196     exit(1);
 197   }
 198   return (g);
 199 }
 200
 201 static ge *getge(group *g, const char *p) {
 202   ge *x = G_CREATE(g);
 203   if (group_readstring(g, x, p, 0)) {
 204     fprintf(stderr, "bad group element `%s'\n", p);
 205     exit(1);
 206   }
 207   return (x);
 208 }
 209
 210 static void showge(group *g, const char *p, ge *x) {
 211   fprintf(stderr, "*** %s = ", p); group_writefile(g, x, stderr);
 212   putc('\n', stderr);
 213 }
 214
 215 static void showmp(const char *p, mp *x, int r) {
 216   fprintf(stderr, "*** %s = ", p); mp_writefile(x, stderr, r);
 217   putc('\n', stderr);
 218 }
 219
 220 static int tsign(dstr *v)
 221 {
 222   gdsa c;
 223   gkcdsa_sig s, ss = GKCDSA_SIG_INIT;
 224   ghash *h;
 225   octet *m;
 226   mp *k;
 227   dstr d = DSTR_INIT;
 228   mp *x;
 229   int ok = 1;
 230
 231   c.g = getgroup(v[0].buf); c.h = ghash_byname(v[1].buf);
 232   c.u = *(mp **)v[2].buf; k = *(mp **)v[4].buf;
 233   s.r = (octet *)v[5].buf; s.s = *(mp **)v[6].buf;
 234   DENSURE(&d, c.h->hashsz); d.len = c.h->hashsz; memset(d.buf, 0, d.len);
 235   ss.r = (octet *)d.buf;
 236
 237   x = mp_modinv(MP_NEW, c.u, c.g->r);
 238   c.p = G_CREATE(c.g); G_EXP(c.g, c.p, c.g->g, x);
 239   h = gkcdsa_beginhash(&c);
 240   GH_HASH(h, v[3].buf, v[3].len);
 241   gkcdsa_endhash(&c, h);
 242   gkcdsa_sign(&c, &ss, GH_DONE(h, 0), k);
 243   GH_DESTROY(h);
 244   if (memcmp(s.r, ss.r, c.h->hashsz) || !MP_EQ(s.s, ss.s)) {
 245     ok = 0;
 246     fprintf(stderr, "*** sign failed!\n");
 247     fprintf(stderr, "*** group: %s\n", v[0].buf);
 248     fprintf(stderr, "*** hash: %s\n", c.h->name);
 249     showmp("private key", c.u, 16);
 250     showge(c.g, "public key", c.p);
 251     fprintf(stderr, "*** message: `%s'\n", v[3].buf);
 252     fprintf(stderr, "*** computed r = ");
 253     type_hex.dump(&d, stderr); putc('\n', stderr);
 254     showmp("computed s", ss.s, 16);
 255     fprintf(stderr, "*** expected r = ");
 256     type_hex.dump(&v[5], stderr); putc('\n', stderr);
 257     showmp("expected s", s.s, 16);
 258   }
 259
 260   c.r = &rand_global;
 261   h = gkcdsa_beginhash(&c);
 262   GH_HASH(h, v[3].buf, v[3].len);
 263   m = GH_DONE(h, 0);
 264   GH_DESTROY(h);
 265   gkcdsa_sign(&c, &ss, m, 0);
 266   if (gkcdsa_verify(&c, &ss, m)) {
 267     ok = 0;
 268     fprintf(stderr, "*** sign cross-check failed!\n");
 269     fprintf(stderr, "*** group: %s\n", v[0].buf);
 270     fprintf(stderr, "*** hash: %s\n", c.h->name);
 271     showmp("private key", c.u, 16);
 272     showge(c.g, "public key", c.p);
 273     fprintf(stderr, "*** message: `%s'\n", v[3].buf);
 274     fprintf(stderr, "*** computed r = ");
 275     type_hex.dump(&d, stderr); putc('\n', stderr);
 276     showmp("computed s", ss.s, 16);
 277   }
 278
 279   mp_drop(s.s); mp_drop(x); mp_drop(k); dstr_destroy(&d); mp_drop(ss.s);
 280   mp_drop(c.u); G_DESTROY(c.g, c.p); G_DESTROYGROUP(c.g);
 281   assert(mparena_count(MPARENA_GLOBAL) == 0);
 282   return (ok);
 283 }
 284
 285 static int tverify(dstr *v)
 286 {
 287   gkcdsa c;
 288   gkcdsa_sig s;
 289   ghash *h;
 290   int rc, erc;
 291   int ok = 1;
 292
 293   c.g = getgroup(v[0].buf); c.h = ghash_byname(v[1].buf);
 294   c.p = getge(c.g, v[2].buf);
 295   s.r = (octet *)v[4].buf; s.s = *(mp **)v[5].buf;
 296   erc = *(int *)v[6].buf;
 297
 298   h = gkcdsa_beginhash(&c);
 299   GH_HASH(h, v[3].buf, v[3].len);
 300   gkcdsa_endhash(&c, h);
 301   rc = gkcdsa_verify(&c, &s, GH_DONE(h, 0));
 302   if (!rc != !erc) {
 303     ok = 0;
 304     fprintf(stderr, "*** verify failed!\n");
 305     fprintf(stderr, "*** group: %s\n", v[0].buf);
 306     fprintf(stderr, "*** hash: %s\n", c.h->name);
 307     showge(c.g, "public key", c.p);
 308     fprintf(stderr, "*** message: `%s'\n", v[3].buf);
 309     fprintf(stderr, "*** sig r = ");
 310     type_hex.dump(&v[4], stderr); putc('\n', stderr);
 311     showmp("sig s", s.s, 16);
 312     fprintf(stderr, "*** expected %s\n", !erc ? "pass" : "fail");
 313   }
 314   mp_drop(s.s); G_DESTROY(c.g, c.p); G_DESTROYGROUP(c.g);
 315   GH_DESTROY(h);
 316   assert(mparena_count(MPARENA_GLOBAL) == 0);
 317   return (ok);
 318 }
 319
 320 static const test_chunk tests[] = {
 321   { "sign", tsign, { &type_string, &type_string, &type_mp, &type_string,
 322                      &type_mp, &type_hex, &type_mp } },
 323   { "verify", tverify, { &type_string, &type_string, &type_string,
 324                          &type_string, &type_hex, &type_mp, &type_int } },
 325   { 0 }
 326 };
 327
 328 int main(int argc, char *argv[])
 329 {
 330   sub_init();
 331   test_run(argc, argv, tests, SRCDIR "/t/gkcdsa");
 332   return (0);
 333 }
 334
 335 #endif
 336
 337 /*----- That's all, folks -------------------------------------------------*/