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 <mLib/macros.h>
  31
  32 #include "dsa.h"
  33 #include "gkcdsa.h"
  34 #include "group.h"
  35 #include "ghash.h"
  36 #include "mpbarrett.h"
  37 #include "mprand.h"
  38
  39 /*----- Main code ---------------------------------------------------------*/
  40
  41 /* --- @gkcdsa_beginhash@ --- *
  42  *
  43  * Arguments:   @const gkcdsa *c@ = pointer to the context structure
  44  *
  45  * Returns:     A hashing context for you to hash the message.
  46  *
  47  * Use:         Initializes a hash function correctly for you to hash a
  48  *              message.  Requires @h@, @g@ and @p@.
  49  */
  50
  51 ghash *gkcdsa_beginhash(const gkcdsa *c)
  52 {
  53   ghash *h = GH_INIT(c->h);
  54   mp *v = G_TOINT(c->g, MP_NEW, c->p);
  55   size_t sz = c->h->bufsz;
  56   void *p = xmalloc(sz);
  57   if (/*ouch*/ !v) memset(p, 0, sz);
  58   else mp_storeb(v, p, sz);
  59   GH_HASH(h, p, sz);
  60   mp_drop(v); xfree(p);
  61   return (h);
  62 }
  63
  64 /* --- @gkcdsa_endhash@ --- *
  65  *
  66  * Arguments:   @const gkcdsa *c@ = pointer to the context structure
  67  *              @ghash *h@ = the hashing context
  68  *
  69  * Returns:     ---
  70  *
  71  * Use:         Does any final thing that KCDSA wants to do when hashing a
  72  *              message.  (Actually, there's nothing.)  The hashing context
  73  *              isn't finalized.
  74  */
  75
  76 void gkcdsa_endhash(const gkcdsa *c, ghash *h) { ; }
  77
  78 /* --- @hashge@ --- *
  79  *
  80  * Arguments:   @group *g@ = abstract group
  81  *              @const gchash *hc@ = hash class
  82  *              @ge *w@ = a group element
  83  *
  84  * Returns:     A hash context, with the hash of @w@ in it.
  85  */
  86
  87 static ghash *hashge(group *g, const gchash *hc, ge *w)
  88 {
  89   ghash *h;
  90   size_t sz;
  91   void *p;
  92   buf b;
  93   int rc;
  94
  95   sz = hc->hashsz;
  96   if (sz < g->noctets)
  97     sz = g->noctets;
  98   p = xmalloc(sz);
  99   buf_init(&b, p, sz);
 100   rc = G_TORAW(g, &b, w);
 101   assert(rc == 0);
 102   h = GH_INIT(hc);
 103   GH_HASH(h, BBASE(&b), BLEN(&b));
 104   xfree(p);
 105   return (h);
 106 }
 107
 108 /* --- @gkcdsa_sign@ --- *
 109  *
 110  * Arguments:   @const gkcdsa *c@ = my context structure
 111  *              @gkcdsa_sig *s@ = where to put the signature (initialized)
 112  *              @const void *m@ = pointer to message hash
 113  *              @mp *k@ = random exponent for this message or null
 114  *
 115  * Returns:     ---
 116  *
 117  * Use:         Signs a message.  Requires @g@, @u@, @h@, and @r@ if @k@ is
 118  *              null.  This is a better idea than inventing @k@ yourself.
 119  */
 120
 121 void gkcdsa_sign(const gkcdsa *c, gkcdsa_sig *s, const void *m, mp *k)
 122 {
 123   group *g = c->g;
 124   mp *x, *y;
 125   ge *z = G_CREATE(g);
 126   size_t hsz = c->h->hashsz;
 127   ghash *h;
 128
 129   if (k) { MP_COPY(k); goto have_k; }
 130 new_k:
 131   k = dsa_nonce(k, g->r, c->u, m, c->h, c->r);
 132 have_k:
 133   if (MP_ZEROP(k)) goto new_k;
 134   G_EXP(g, z, g->g, k);
 135   if (!s->r) s->r = xmalloc(hsz);
 136   h = hashge(g, c->h, z); GH_DONE(h, s->r);
 137
 138   x = mp_loadb(s->s, m, hsz);
 139   y = mp_loadb(MP_NEW, s->r, hsz);
 140   x = mp_xor(x, x, y);
 141   mp_div(0, &x, x, g->r);
 142   x = mp_sub(x, g->r, x);
 143   x = mp_add(x, x, k);
 144   if (MP_CMP(x, >=, g->r)) x = mp_sub(x, x, g->r);
 145   x = mp_mul(x, x, c->u); mp_div(0, &x, x, g->r);
 146   s->s = x;
 147   mp_drop(k); mp_drop(y); GH_DESTROY(h); G_DESTROY(g, z);
 148 }
 149
 150 /* --- @gkcdsa_verify@ --- *
 151  *
 152  * Arguments:   @const gkcdsa *c@ = my context structure
 153  *              @const gkcdsa_sig *s@ = the signature to verify
 154  *              @const void *m@ = pointer to message hash
 155  *
 156  * Returns:     Zero if OK, negative on failure.
 157  *
 158  * Use:         Checks a signature on a message,  Requires @g@, @p@, @h@.
 159  */
 160
 161 int gkcdsa_verify(const gkcdsa *c, const gkcdsa_sig *s, const void *m)
 162 {
 163   group *g = c->g;
 164   size_t hsz = c->h->hashsz;
 165   group_expfactor e[2];
 166   mp *x, *y;
 167   ghash *h;
 168   ge *z;
 169   octet *p;
 170   int rc = -1;
 171
 172   if (MP_CMP(s->s, <, MP_ONE) || MP_CMP(s->s, >=, g->r))
 173     return (-1);
 174   x = mp_loadb(MP_NEW, m, hsz); y = mp_loadb(MP_NEW, s->r, hsz);
 175   x = mp_xor(x, x, y); mp_div(0, &x, x, g->r);
 176   e[0].base = c->p; e[0].exp = s->s;
 177   e[1].base = g->g; e[1].exp = x;
 178   z = G_CREATE(g); G_MEXP(g, z, e, 2);
 179   h = hashge(g, c->h, z); p = GH_DONE(h, 0);
 180   if (MEMCMP(p, ==, s->r, hsz)) rc = 0;
 181   mp_drop(x); mp_drop(y); G_DESTROY(g, z); GH_DESTROY(h);
 182   return (rc);
 183 }
 184
 185 /*----- Test rig ----------------------------------------------------------*/
 186
 187 #ifdef TEST_RIG
 188
 189 #include "rand.h"
 190
 191 static group *getgroup(const char *p) {
 192   group *g; qd_parse qd;
 193   qd.p = p; qd.e = 0; g = group_parse(&qd);
 194   if (g && !qd_eofp(&qd)) { G_DESTROYGROUP(g); g = 0; qd.e = "junk at eof"; }
 195   if (!g) {
 196     fprintf(stderr, "bad group string `%.*s|%s': %s\n",
 197             (int)(qd.p - p), p, qd.p, qd.e);
 198     exit(1);
 199   }
 200   return (g);
 201 }
 202
 203 static ge *getge(group *g, const char *p) {
 204   ge *x = G_CREATE(g);
 205   if (group_readstring(g, x, p, 0)) {
 206     fprintf(stderr, "bad group element `%s'\n", p);
 207     exit(1);
 208   }
 209   return (x);
 210 }
 211
 212 static void showge(group *g, const char *p, ge *x) {
 213   fprintf(stderr, "*** %s = ", p); group_writefile(g, x, stderr);
 214   putc('\n', stderr);
 215 }
 216
 217 static void showmp(const char *p, mp *x, int r) {
 218   fprintf(stderr, "*** %s = ", p); mp_writefile(x, stderr, r);
 219   putc('\n', stderr);
 220 }
 221
 222 static int tsign(dstr *v)
 223 {
 224   gdsa c;
 225   gkcdsa_sig s, ss = GKCDSA_SIG_INIT;
 226   ghash *h;
 227   octet *m;
 228   mp *k;
 229   dstr d = DSTR_INIT;
 230   mp *x;
 231   int ok = 1;
 232
 233   c.g = getgroup(v[0].buf); c.h = ghash_byname(v[1].buf);
 234   c.u = *(mp **)v[2].buf; k = *(mp **)v[4].buf;
 235   s.r = (octet *)v[5].buf; s.s = *(mp **)v[6].buf;
 236   DENSURE(&d, c.h->hashsz); d.len = c.h->hashsz; memset(d.buf, 0, d.len);
 237   ss.r = (octet *)d.buf;
 238
 239   x = mp_modinv(MP_NEW, c.u, c.g->r);
 240   c.p = G_CREATE(c.g); G_EXP(c.g, c.p, c.g->g, x);
 241   h = gkcdsa_beginhash(&c);
 242   GH_HASH(h, v[3].buf, v[3].len);
 243   gkcdsa_endhash(&c, h);
 244   gkcdsa_sign(&c, &ss, GH_DONE(h, 0), k);
 245   GH_DESTROY(h);
 246   if (MEMCMP(s.r, !=, ss.r, c.h->hashsz) || !MP_EQ(s.s, ss.s)) {
 247     ok = 0;
 248     fprintf(stderr, "*** sign failed!\n");
 249     fprintf(stderr, "*** group: %s\n", v[0].buf);
 250     fprintf(stderr, "*** hash: %s\n", c.h->name);
 251     showmp("private key", c.u, 16);
 252     showge(c.g, "public key", c.p);
 253     fprintf(stderr, "*** message: `%s'\n", v[3].buf);
 254     fprintf(stderr, "*** computed r = ");
 255     type_hex.dump(&d, stderr); putc('\n', stderr);
 256     showmp("computed s", ss.s, 16);
 257     fprintf(stderr, "*** expected r = ");
 258     type_hex.dump(&v[5], stderr); putc('\n', stderr);
 259     showmp("expected s", s.s, 16);
 260   }
 261
 262   c.r = &rand_global;
 263   h = gkcdsa_beginhash(&c);
 264   GH_HASH(h, v[3].buf, v[3].len);
 265   m = GH_DONE(h, 0);
 266   GH_DESTROY(h);
 267   gkcdsa_sign(&c, &ss, m, 0);
 268   if (gkcdsa_verify(&c, &ss, m)) {
 269     ok = 0;
 270     fprintf(stderr, "*** sign cross-check failed!\n");
 271     fprintf(stderr, "*** group: %s\n", v[0].buf);
 272     fprintf(stderr, "*** hash: %s\n", c.h->name);
 273     showmp("private key", c.u, 16);
 274     showge(c.g, "public key", c.p);
 275     fprintf(stderr, "*** message: `%s'\n", v[3].buf);
 276     fprintf(stderr, "*** computed r = ");
 277     type_hex.dump(&d, stderr); putc('\n', stderr);
 278     showmp("computed s", ss.s, 16);
 279   }
 280
 281   mp_drop(s.s); mp_drop(x); mp_drop(k); dstr_destroy(&d); mp_drop(ss.s);
 282   mp_drop(c.u); G_DESTROY(c.g, c.p); G_DESTROYGROUP(c.g);
 283   assert(mparena_count(MPARENA_GLOBAL) == 0);
 284   return (ok);
 285 }
 286
 287 static int tverify(dstr *v)
 288 {
 289   gkcdsa c;
 290   gkcdsa_sig s;
 291   ghash *h;
 292   int rc, erc;
 293   int ok = 1;
 294
 295   c.g = getgroup(v[0].buf); c.h = ghash_byname(v[1].buf);
 296   c.p = getge(c.g, v[2].buf);
 297   s.r = (octet *)v[4].buf; s.s = *(mp **)v[5].buf;
 298   erc = *(int *)v[6].buf;
 299
 300   h = gkcdsa_beginhash(&c);
 301   GH_HASH(h, v[3].buf, v[3].len);
 302   gkcdsa_endhash(&c, h);
 303   rc = gkcdsa_verify(&c, &s, GH_DONE(h, 0));
 304   if (!rc != !erc) {
 305     ok = 0;
 306     fprintf(stderr, "*** verify failed!\n");
 307     fprintf(stderr, "*** group: %s\n", v[0].buf);
 308     fprintf(stderr, "*** hash: %s\n", c.h->name);
 309     showge(c.g, "public key", c.p);
 310     fprintf(stderr, "*** message: `%s'\n", v[3].buf);
 311     fprintf(stderr, "*** sig r = ");
 312     type_hex.dump(&v[4], stderr); putc('\n', stderr);
 313     showmp("sig s", s.s, 16);
 314     fprintf(stderr, "*** expected %s\n", !erc ? "pass" : "fail");
 315   }
 316   mp_drop(s.s); G_DESTROY(c.g, c.p); G_DESTROYGROUP(c.g);
 317   GH_DESTROY(h);
 318   assert(mparena_count(MPARENA_GLOBAL) == 0);
 319   return (ok);
 320 }
 321
 322 static const test_chunk tests[] = {
 323   { "sign", tsign, { &type_string, &type_string, &type_mp, &type_string,
 324                      &type_mp, &type_hex, &type_mp } },
 325   { "verify", tverify, { &type_string, &type_string, &type_string,
 326                          &type_string, &type_hex, &type_mp, &type_int } },
 327   { 0 }
 328 };
 329
 330 int main(int argc, char *argv[])
 331 {
 332   sub_init();
 333   test_run(argc, argv, tests, SRCDIR "/t/gkcdsa");
 334   return (0);
 335 }
 336
 337 #endif
 338
 339 /*----- That's all, folks -------------------------------------------------*/