Force subkeys to be sorted in structured keys.

[u/mdw/catacomb] / gkcdsa.c

/* -*-c-*-
 *
 * $Id: gkcdsa.c,v 1.1 2004/04/04 19:42:59 mdw Exp $
 *
 * Generalized version of KCDSA
 *
 * (c) 2004 Straylight/Edgeware
 */

/*----- Licensing notice --------------------------------------------------* 
 *
 * This file is part of Catacomb.
 *
 * Catacomb is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Library General Public License as
 * published by the Free Software Foundation; either version 2 of the
 * License, or (at your option) any later version.
 * 
 * Catacomb is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Library General Public License for more details.
 * 
 * You should have received a copy of the GNU Library General Public
 * License along with Catacomb; if not, write to the Free
 * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
 * MA 02111-1307, USA.
 */

/*----- Revision history --------------------------------------------------* 
 *
 * $Log: gkcdsa.c,v $
 * Revision 1.1  2004/04/04 19:42:59  mdw
 * Add set -e.
 *
 */

/*----- Header files ------------------------------------------------------*/

#include "gkcdsa.h"
#include "group.h"
#include "ghash.h"
#include "mpbarrett.h"
#include "mprand.h"

/*----- Main code ---------------------------------------------------------*/

/* --- @gdsa_beginhash@ --- *
 *
 * Arguments:	@const gdsa *c@ = pointer to the context structure
 *
 * Returns:	A hashing context for you to hash the message.
 *
 * Use:		Initializes a hash function correctly for you to hash a
 *		message.  Requires @h@, @g@ and @p@.
 */

ghash *gkcdsa_beginhash(const gkcdsa *c)
{
  ghash *h = GH_INIT(c->h);
  mp *v = G_TOINT(c->g, MP_NEW, c->p);
  size_t sz = c->h->bufsz;
  void *p = xmalloc(sz);

  if (/*ouch*/ !v) memset(p, 0, sz);
  else mp_storeb(v, p, sz);
  GH_HASH(h, p, sz);
  mp_drop(v); xfree(p);
  return (h);
}

/* --- @gkcdsa_endhash@ --- *
 *
 * Arguments:	@const gkcdsa *c@ = pointer to the context structure
 *		@ghash *h@ = the hashing context
 *
 * Returns:	---
 *
 * Use:		Does any final thing that KCDSA wants to do when hashing a
 *		message.  (Actually, there's nothing.)  The hashing context
 *		isn't finalized.
 */

void gkcdsa_endhash(gkcdsa *c, ghash *h) { ; }

/* --- @hashge@ --- *
 *
 * Arguments:	@group *g@ = abstract group
 *		@const gchash *hc@ = hash class
 *		@ge *w@ = a group element
 *
 * Returns:	A hash context, with the hash of @w@ in it.
 */

static ghash *hashge(group *g, const gchash *hc, ge *w)
{
  ghash *h;
  size_t sz;
  void *p;
  buf b;
  int rc;

  sz = hc->hashsz;
  if (sz < g->noctets)
    sz = g->noctets;
  p = xmalloc(sz);
  buf_init(&b, p, sz);
  rc = G_TORAW(g, &b, w);
  assert(rc == 0);
  h = GH_INIT(hc);
  GH_HASH(h, BBASE(&b), BLEN(&b));
  xfree(p);
  return (h);
}

/* --- @gkcdsa_sign@ --- *
 *
 * Arguments:	@const gkcdsa *c@ = my context structure
 *		@gkcdsa_sig *s@ = where to put the signature (initialized)
 *		@const void *m@ = pointer to message hash
 *		@mp *k@ = random exponent for this message or null
 *
 * Returns:	---
 *
 * Use:		Signs a message.  Requires @g@, @u@, @h@, and @r@ if @k@ is
 *		null.  This is a better idea than inventing @k@ yourself.
 */

void gkcdsa_sign(const gkcdsa *c, gkcdsa_sig *s, const void *m, mp *k)
{
  group *g = c->g;
  mp *x, *y;
  ge *z = G_CREATE(g);
  size_t hsz = c->h->hashsz;
  ghash *h;

  if (k) { MP_COPY(k); goto have_k; }
new_k:
  k = mprand_range(k, g->r, c->r, 0);
have_k:
  if (MP_ISZERO(k)) goto new_k;
  G_EXP(g, z, g->g, k);
  if (!s->r) s->r = xmalloc(hsz);
  h = hashge(g, c->h, z); GH_DONE(h, s->r);

  x = mp_loadb(s->s, m, hsz);
  y = mp_loadb(MP_NEW, s->r, hsz);
  x = mp_xor(x, x, y);
  mp_div(0, &x, x, g->r);
  x = mp_sub(x, g->r, x);
  x = mp_add(x, x, k);
  if (MP_CMP(x, >=, g->r)) x = mp_sub(x, x, g->r);
  x = mp_mul(x, x, c->u); mp_div(0, &x, x, g->r);
  s->s = x;
  mp_drop(k); mp_drop(y); GH_DESTROY(h); G_DESTROY(g, z);
}

/* --- @gkcdsa_verify@ --- *
 *
 * Arguments:	@const gkcdsa *c@ = my context structure
 *		@const gkcdsa_sig *s@ = the signature to verify
 *		@const void *m@ = pointer to message hash
 *
 * Returns:	Zero if OK, negative on failure.
 *
 * Use:		Checks a signature on a message,  Requires @g@, @p@, @h@.
 */

int gkcdsa_verify(const gkcdsa *c, const gkcdsa_sig *s, const void *m)
{
  group *g = c->g;
  size_t hsz = c->h->hashsz;
  group_expfactor e[2];
  mp *x, *y;
  ghash *h;
  ge *z;
  octet *p;
  int rc = -1;

  if (MP_CMP(s->s, <, MP_ONE) || MP_CMP(s->s, >=, g->r))
    return (-1);
  x = mp_loadb(MP_NEW, m, hsz); y = mp_loadb(MP_NEW, s->r, hsz);
  x = mp_xor(x, x, y); mp_div(0, &x, x, g->r);
  e[0].base = c->p; e[0].exp = s->s;
  e[1].base = g->g; e[1].exp = x;
  z = G_CREATE(g); G_MEXP(g, z, e, 2);
  h = hashge(g, c->h, z); p = GH_DONE(h, 0);
  if (memcmp(p, s->r, hsz) == 0) rc = 0;
  mp_drop(x); mp_drop(y); G_DESTROY(g, z); GH_DESTROY(h);
  return (rc);
}

/*----- Test rig ----------------------------------------------------------*/

#ifdef TEST_RIG

static group *getgroup(const char *p) {
  group *g; qd_parse qd;
  qd.p = p; qd.e = 0; g = group_parse(&qd);
  if (g && !qd_eofp(&qd)) { G_DESTROYGROUP(g); g = 0; qd.e = "junk at eof"; }
  if (!g) { fprintf(stderr, "bad group string `%.*s|%s': %s\n", qd.p - p,
		    p, qd.p, qd.e); exit(1); }
  return (g);
}

static ge *getge(group *g, const char *p) {
  ge *x = G_CREATE(g);
  if (group_readstring(g, x, p, 0)) {
    fprintf(stderr, "bad group element `%s'\n", p);
    exit(1);
  }
  return (x);
}

static void showge(group *g, const char *p, ge *x) {
  fprintf(stderr, "*** %s = ", p); group_writefile(g, x, stderr);
  putc('\n', stderr);
}

static void showmp(const char *p, mp *x, int r) {
  fprintf(stderr, "*** %s = ", p); mp_writefile(x, stderr, r); 
  putc('\n', stderr);
}

static int tsign(dstr *v)
{
  gdsa c;
  gkcdsa_sig s, ss = GKCDSA_SIG_INIT;
  ghash *h;
  mp *k;
  dstr d = DSTR_INIT;
  mp *x;
  int ok = 1;

  c.g = getgroup(v[0].buf); c.h = ghash_byname(v[1].buf);
  c.u = *(mp **)v[2].buf; k = *(mp **)v[4].buf;
  s.r = (octet *)v[5].buf; s.s = *(mp **)v[6].buf;
  DENSURE(&d, c.h->hashsz); d.len = c.h->hashsz; memset(d.buf, 0, d.len);
  ss.r = (octet *)d.buf;

  x = MP_NEW; mp_gcd(0, 0, &x, c.g->r, c.u);
  c.p = G_CREATE(c.g); G_EXP(c.g, c.p, c.g->g, x);
  h = gkcdsa_beginhash(&c);
  GH_HASH(h, v[3].buf, v[3].len);
  gkcdsa_endhash(&c, h);
  gkcdsa_sign(&c, &ss, GH_DONE(h, 0), k);
  if (memcmp(s.r, ss.r, c.h->hashsz) || !MP_EQ(s.s, ss.s)) {
    ok = 0;
    fprintf(stderr, "*** sign failed!\n");
    fprintf(stderr, "*** group: %s\n", v[0].buf);
    fprintf(stderr, "*** hash: %s\n", c.h->name);
    showmp("private key", c.u, 16);
    showge(c.g, "public key", c.p);
    fprintf(stderr, "*** message: `%s'\n", v[3].buf);
    fprintf(stderr, "*** computed r = ");
    type_hex.dump(&d, stderr); putc('\n', stderr);
    showmp("computed s", ss.s, 16);
    fprintf(stderr, "*** computed r = ");
    type_hex.dump(&v[5], stderr); putc('\n', stderr);
    showmp("expected s", s.s, 16);
  }
  mp_drop(s.s); dstr_destroy(&d); mp_drop(ss.s); mp_drop(x); mp_drop(k);
  mp_drop(c.u); G_DESTROY(c.g, c.p); G_DESTROYGROUP(c.g); GH_DESTROY(h);
  assert(mparena_count(MPARENA_GLOBAL) == 0);
  return (ok);
}

static int tverify(dstr *v)
{
  gkcdsa c;
  gkcdsa_sig s;
  ghash *h;
  int rc, erc;
  int ok = 1;

  c.g = getgroup(v[0].buf); c.h = ghash_byname(v[1].buf);
  c.p = getge(c.g, v[2].buf);
  s.r = (octet *)v[4].buf; s.s = *(mp **)v[5].buf;
  erc = *(int *)v[6].buf;

  h = gkcdsa_beginhash(&c);
  GH_HASH(h, v[3].buf, v[3].len);
  gkcdsa_endhash(&c, h);
  rc = gkcdsa_verify(&c, &s, GH_DONE(h, 0));
  if (!rc != !erc) {
    ok = 0;
    fprintf(stderr, "*** verify failed!\n");
    fprintf(stderr, "*** group: %s\n", v[0].buf);
    fprintf(stderr, "*** hash: %s\n", c.h->name);
    showge(c.g, "public key", c.p);
    fprintf(stderr, "*** message: `%s'\n", v[3].buf);
    fprintf(stderr, "*** sig r = ");
    type_hex.dump(&v[4], stderr); putc('\n', stderr);
    showmp("sig s", s.s, 16);
    fprintf(stderr, "*** expected %s\n", !erc ? "pass" : "fail");
  }
  mp_drop(s.s); G_DESTROY(c.g, c.p); G_DESTROYGROUP(c.g);
  GH_DESTROY(h);
  assert(mparena_count(MPARENA_GLOBAL) == 0);
  return (ok);
}

static const test_chunk tests[] = {
  { "sign", tsign, { &type_string, &type_string, &type_mp, &type_string,
		     &type_mp, &type_hex, &type_mp } },
  { "verify", tverify, { &type_string, &type_string, &type_string,
			 &type_string, &type_hex, &type_mp, &type_int } },
  { 0 }
};

int main(int argc, char *argv[])
{
  sub_init();
  test_run(argc, argv, tests, SRCDIR "/tests/gkcdsa");
  return (0);
}

#endif

/*----- That's all, folks -------------------------------------------------*/