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