X-Git-Url: https://git.distorted.org.uk/u/mdw/catacomb/blobdiff_plain/ba6e6b64033b1f9de49feccb5c9cd438354481f7..0f00dc4c8eb47e67bc0f148c2dd109f73a451e0a:/pub/gkcdsa.c

diff --git a/pub/gkcdsa.c b/pub/gkcdsa.c
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+/* -*-c-*-
+ *
+ * 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.
+ */
+
+/*----- Header files ------------------------------------------------------*/
+
+#include "gkcdsa.h"
+#include "group.h"
+#include "ghash.h"
+#include "mpbarrett.h"
+#include "mprand.h"
+
+/*----- Main code ---------------------------------------------------------*/
+
+/* --- @gkcdsa_beginhash@ --- *
+ *
+ * Arguments:	@const gkcdsa *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(const 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_ZEROP(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_modinv(MP_NEW, c.u, c.g->r);
+  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 "/t/gkcdsa");
+  return (0);
+}
+
+#endif
+
+/*----- That's all, folks -------------------------------------------------*/