[tripe] / server / dh.c

/* -*-c-*-
 *
 * Diffie--Hellman groups
 *
 * (c) 2017 Straylight/Edgeware
 */

/*----- Licensing notice --------------------------------------------------*
 *
 * This file is part of Trivial IP Encryption (TrIPE).
 *
 * TrIPE is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * TrIPE 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with TrIPE; if not, write to the Free Software Foundation,
 * Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 */

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

#include "tripe.h"

/*----- Common utilities --------------------------------------------------*/

/* --- @KLOAD@ --- *
 *
 * Arguments:	@pre@ = prefix for defined functions
 *		@ty@, @TY@ = key type name (lower- and upper-case)
 *		@setgroup@ = code to initialize @kd->g@
 *		@setpriv@ = code to initialize @kd->kpriv@
 *		@setpub@ = code to initialize @kd->kpub@
 *
 * Use:		Generates the body of one of the (rather tedious) key loading
 *		functions.  See the description of @KEYTYPES@ below for the
 *		details.
 */

#define KLOAD_HALF(pre, ty, TY, which, WHICH, setgroup, setpriv, setpub) \
static int pre##_ld##which(key_file *kf, key *k, key_data *d,		\
			   kdata *kd, dstr *t, dstr *e)			\
{									\
  key_packstruct kps[TY##_##WHICH##FETCHSZ];				\
  key_packdef *kp;							\
  ty##_##which p;							\
  int rc;								\
									\
  /* --- Initialize things we've not set up yet --- */			\
									\
  kd->grp = 0; kd->k = 0; kd->K = 0;					\
									\
  /* --- Unpack the key --- */						\
									\
  kp = key_fetchinit(ty##_##which##fetch, kps, &p);			\
  if ((rc = key_unpack(kp, d, t)) != 0) {				\
    a_format(e, "unpack-failed", "%s", key_strerror(rc), A_END);	\
    goto fail;								\
  }									\
									\
  /* --- Extract the pieces of the key --- */				\
									\
  setgroup;								\
  setpriv;								\
  setpub;								\
									\
  /* --- We win --- */							\
									\
  rc = 0;								\
  goto done;								\
									\
fail:									\
  if (kd->grp) {							\
    if (kd->K) pre##_freege(kd->grp, kd->K);				\
    if (kd->k) pre##_freesc(kd->grp, kd->k);				\
    pre##_freegrp(kd->grp);						\
  }									\
  rc = -1;								\
									\
done:									\
  key_fetchdone(kp);							\
  return (rc);								\
}

#define KLOAD(pre, ty, TY, setgroup, setpriv, setpub)			\
static void pre##_freegrp(dhgrp *); \
static void pre##_freesc(const dhgrp *, dhsc *); \
static void pre##_freege(const dhgrp *, dhge *); \
  KLOAD_HALF(pre, ty, TY, priv, PRIV, setgroup, setpriv, setpub)	\
  KLOAD_HALF(pre, ty, TY, pub, PUB, setgroup, { kd->k = 0; }, setpub)

enum { DHSER_V0, DHSER_CONSTLEN };

static int get_serialization(key_file *kf, key *k, dstr *e)
{
  const char *p = key_getattr(kf, k, "serialization");
  if (!p || strcmp(p, "v0") == 0) return (DHSER_V0);
  else if (strcmp(p, "constlen") == 0) return (DHSER_CONSTLEN);
  else {
    a_format(e, "unknown-serialization-format", "%s", p, A_END);
    return (-1);
  }
}

#ifndef NTRACE
static void setupstr(mptext_stringctx *sc)
  { sc->buf = (char *)buf_u; sc->lim = sc->buf + sizeof(buf_u); }

static const char *donestr(mptext_stringctx *sc)
  { *sc->buf = 0; return ((const char *)buf_u); }

static void addlitstr(const char *p, mptext_stringctx *sc)
  { mptext_stringops.put(p, strlen(p), sc); }

static void addmpstr(mp *x, int radix, mptext_stringctx *sc)
{
  char b[12];

  if (radix == 16) addlitstr("0x", sc);
  else if (radix == 8) addlitstr("0", sc);
  else if (radix != 10) { sprintf(b, "%d#", radix); addlitstr(b, sc); }
  mp_write(x, radix, &mptext_stringops, sc);
}

static const char *mpstr(mp *x, int radix)
{
  mptext_stringctx sc;

  setupstr(&sc);
  addmpstr(x, radix, &sc);
  return (donestr(&sc));
}
#endif

/*----- Schnorr groups ----------------------------------------------------*/

typedef struct intdh_grp {
  dhgrp _g;
  mpmont mm;
  mp *q, *G;
  size_t gesz;
  int ser;
} intdh_grp;

typedef struct intdh_sc { mp *x; } intdh_sc;
typedef struct intdh_ge { mp *X; } intdh_ge;

static dhgrp *intdh_mkgroup(key_file *kf, key *k,
			    const dh_param *dp, dstr *e)
{
  intdh_grp *g;
  int ser;

  if ((ser = get_serialization(kf, k, e)) < 0) return (0);
  g = CREATE(intdh_grp);
  g->ser = ser;
  g->_g.scsz = mp_octets(dp->q);
  g->gesz = mp_octets(dp->p);
  mpmont_create(&g->mm, dp->p);
  g->q = MP_COPY(dp->q);
  g->G = mpmont_mul(&g->mm, MP_NEW, dp->g, g->mm.r2);
  return (&g->_g);
}

static dhsc *intdh_mptosc(const dhgrp *gg, mp *z)
{
  const intdh_grp *g = (const intdh_grp *)gg;
  intdh_sc *x = CREATE(intdh_sc);
  x->x = MP_NEW; mp_div(0, &x->x, z, g->q);
  return ((dhsc *)x);
}

static dhge *intdh_mptoge(const dhgrp *gg, mp *z)
{
  const intdh_grp *g = (const intdh_grp *)gg;
  intdh_ge *Y = CREATE(intdh_ge);
  mp *t = MP_NEW; mp_div(0, &t, z, g->mm.m);
  Y->X = mpmont_mul(&g->mm, t, t, g->mm.r2);
  return ((dhge *)Y);
}

KLOAD(intdh, dh, DH,
      { if ((kd->grp = intdh_mkgroup(kf, k, &p.dp, e)) == 0) goto fail; },
      { kd->k = intdh_mptosc(kd->grp, p.x); },
      { kd->K = intdh_mptoge(kd->grp, p.y); })

static const char *intdh_checkgrp(const dhgrp *gg)
{
  const intdh_grp *g = (const intdh_grp *)gg;
  mp *t = MP_NEW;

  if (!pgen_primep(g->mm.m, &rand_global)) return ("p is not prime");
  if (!pgen_primep(g->q, &rand_global)) return ("q is not prime");
  mp_div(0, &t, g->mm.m, g->q);
  if (!MP_EQ(t, MP_ONE)) return ("q is not a subgroup order");
  t = mpmont_expr(&g->mm, t, g->G, g->q);
  if (!MP_EQ(t, g->mm.r)) return ("g not in the subgroup");
  return (0);
}

static void intdh_grpinfo(const dhgrp *gg, admin *adm)
{
  const intdh_grp *g = (const intdh_grp *)gg;
  a_info(adm,
	 "kx-group=prime",
	 "kx-group-order-bits=%lu", (unsigned long)mp_bits(g->q),
	 "kx-group-elt-bits=%lu", (unsigned long)mp_bits(g->mm.m),
	 A_END);
}

#ifndef NTRACE
static void intdh_tracegrp(const dhgrp *gg)
{
  const intdh_grp *g = (const intdh_grp *)gg;
  mp *t = MP_NEW;
  trace(T_CRYPTO, "crypto: group type `dh'");
  trace(T_CRYPTO, "crypto: p = %s", mpstr(g->mm.m, 10));
  trace(T_CRYPTO, "crypto: q = %s", mpstr(g->q, 10));
  t = mpmont_reduce(&g->mm, t, g->G);
  trace(T_CRYPTO, "crypto: g = %s", mpstr(t, 10));
  MP_DROP(t);
}
#endif

static int intdh_samegrpp(const dhgrp *gg, const dhgrp *hh)
{
  const intdh_grp *g = (const intdh_grp *)gg, *h = (const intdh_grp *)hh;
  return (MP_EQ(g->mm.m, h->mm.m) &&
	  MP_EQ(g->q, h->q) && MP_EQ(g->G, h->G) &&
	  g->ser == h->ser);
}

static void intdh_freegrp(dhgrp *gg)
{
  intdh_grp *g = (intdh_grp *)gg;
  mpmont_destroy(&g->mm); MP_DROP(g->q); MP_DROP(g->G);
  DESTROY(g);
}

static dhsc *intdh_ldsc(const dhgrp *gg, const void *p, size_t sz)
{ const intdh_grp *g = (const intdh_grp *)gg;
  intdh_sc *x = CREATE(intdh_sc);
  mp *t = mp_loadb(MP_NEW, p, sz);
  mp_div(0, &t, t, g->q); x->x = t;
  return ((dhsc *)x);
}

static int intdh_stsc(const dhgrp *gg, void *p, size_t sz, const dhsc *xx)
{
  const intdh_sc *x = (const intdh_sc *)xx;
  mp_storeb(x->x, p, sz);
  return (0);
}

static dhsc *intdh_randsc(const dhgrp *gg)
{
  const intdh_grp *g = (const intdh_grp *)gg;
  intdh_sc *x = CREATE(intdh_sc);
  x->x = mprand_range(MP_NEW, g->q, &rand_global, 0);
  return ((dhsc *)x);
}

#ifndef NTRACE
static const char *intdh_scstr(const dhgrp *gg, const dhsc *xx)
  { const intdh_sc *x = (const intdh_sc *)xx; return (mpstr(x->x, 10)); }
#endif

static void intdh_freesc(const dhgrp *gg, dhsc *xx)
{
  intdh_sc *x = (intdh_sc *)xx;
  MP_DROP(x->x); DESTROY(x);
}

static dhge *intdh_ldge(const dhgrp *gg, buf *b, int fmt)
{
  const intdh_grp *g = (const intdh_grp *)gg;
  intdh_ge *Y;
  mp *t;
  const octet *p;

  switch (fmt) {
    case DHFMT_HASH: if (g->ser == DHSER_CONSTLEN) goto std;
    case DHFMT_VAR:
      if ((t = buf_getmp(b)) == 0) return (0);
      break;
    case DHFMT_STD: std:
      if ((p = buf_get(b, g->gesz)) == 0) return (0);
      t = mp_loadb(MP_NEW, p, g->gesz);
      break;
    default:
      abort();
  }
  Y = CREATE(intdh_ge);
  mp_div(0, &t, t, g->mm.m);
  Y->X = mpmont_mul(&g->mm, t, t, g->mm.r2);
  return ((dhge *)Y);
}

static int intdh_stge(const dhgrp *gg, buf *b, const dhge *YY, int fmt)
{
  const intdh_grp *g = (const intdh_grp *)gg;
  const intdh_ge *Y = (const intdh_ge *)YY;
  octet *p;
  mp *t;
  int rc;

  t = mpmont_reduce(&g->mm, MP_NEW, Y->X);
  switch (fmt) {
    case DHFMT_HASH: if (g->ser == DHSER_CONSTLEN) goto std;
    case DHFMT_VAR:
      rc = buf_putmp(b, t);
      break;
    case DHFMT_STD: std:
      if ((p = buf_get(b, g->gesz)) == 0)
	rc = -1;
      else {
	mp_storeb(t, p, g->gesz);
	rc = 0;
      }
      break;
    default:
      abort();
  }
  MP_DROP(t);
  return (rc);
}

static int intdh_checkge(const dhgrp *gg, const dhge *YY)
{
  const intdh_grp *g = (const intdh_grp *)gg;
  const intdh_ge *Y = (const intdh_ge *)YY;
  mp *T;
  int rc = 0;

  if (MP_EQ(Y->X, g->mm.r)) rc = -1;
  T = mpmont_expr(&g->mm, MP_NEW, Y->X, g->q);
  if (!MP_EQ(T, g->mm.r)) rc = -1;
  MP_DROP(T);
  return (rc);
}

static int intdh_eq(const dhgrp *gg, const dhge *YY, const dhge *ZZ)
{
  const intdh_ge *Y = (const intdh_ge *)YY, *Z = (const intdh_ge *)ZZ;
  return (MP_EQ(Y->X, Z->X));
}

static dhge *intdh_mul(const dhgrp *gg, const dhsc *xx, const dhge *YY)
{
  const intdh_grp *g = (const intdh_grp *)gg;
  const intdh_sc *x = (const intdh_sc *)xx;
  const intdh_ge *Y = (const intdh_ge *)YY;
  intdh_ge *Z = CREATE(intdh_ge);

  Z->X = mpmont_expr(&g->mm, MP_NEW, Y ? Y->X : g->G, x->x);
  return ((dhge *)Z);
}

#ifndef NTRACE
static const char *intdh_gestr(const dhgrp *gg, const dhge *YY)
{
  const intdh_grp *g = (const intdh_grp *)gg;
  const intdh_ge *Y = (const intdh_ge *)YY;
  mp *t = mpmont_reduce(&g->mm, MP_NEW, Y->X);
  const char *p = mpstr(t, 10);
  MP_DROP(t);
  return (p);
}
#endif

static void intdh_freege(const dhgrp *gg, dhge *YY)
  { intdh_ge *Y = (intdh_ge *)YY; MP_DROP(Y->X); DESTROY(Y); }

/*----- Elliptic curve groups ---------------------------------------------*/

typedef struct ecdh_grp {
  dhgrp _g;
  ec_info ei;
  ec P;
  int ser;
} ecdh_grp;

typedef struct ecdh_sc { mp *x; } ecdh_sc;
typedef struct ecdh_ge { ec Q; } ecdh_ge;

static dhgrp *ecdh_mkgroup(key_file *kf, key *k, const char *cstr, dstr *e)
{
  ecdh_grp *g;
  ec_info ei;
  int ser;
  const char *err;

  if ((ser = get_serialization(kf, k, e)) < 0) return (0);
  if ((err = ec_getinfo(&ei, cstr)) != 0) {
    a_format(e, "decode-failed", "%s", err, A_END);
    return (0);
  }
  g = CREATE(ecdh_grp);
  g->ser = ser;
  g->ei = ei;
  EC_CREATE(&g->P); EC_IN(g->ei.c, &g->P, &g->ei.g);
  g->_g.scsz = mp_octets(g->ei.r);
  return (&g->_g);
}

static dhsc *ecdh_mptosc(const dhgrp *gg, mp *z)
{
  const ecdh_grp *g = (const ecdh_grp *)gg;
  ecdh_sc *x = CREATE(ecdh_sc);
  x->x = MP_NEW; mp_div(0, &x->x, z, g->ei.r);
  return ((dhsc *)x);
}

static dhge *ecdh_ectoge(const dhgrp *gg, ec *Q)
{
  const ecdh_grp *g = (const ecdh_grp *)gg;
  ecdh_ge *Y = CREATE(ecdh_ge); EC_CREATE(&Y->Q);
  EC_IN(g->ei.c, &Y->Q, Q);
  if (EC_CHECK(g->ei.c, &Y->Q))
    { EC_DESTROY(&Y->Q); DESTROY(Y); return (0); }
  return ((dhge *)Y);
}

KLOAD(ecdh, ec, EC,
      { if ((kd->grp = ecdh_mkgroup(kf, k, p.cstr, e)) == 0) goto fail; },
      { kd->k = ecdh_mptosc(kd->grp, p.x); },
      { if ((kd->K = ecdh_ectoge(kd->grp, &p.p)) == 0) {
	  a_format(e, "bad-public-vector", A_END);
	  goto fail;
	}
      })

static const char *ecdh_checkgrp(const dhgrp *gg)
{
  const ecdh_grp *g = (const ecdh_grp *)gg;
  return (ec_checkinfo(&g->ei, &rand_global));
}

static void ecdh_grpinfo(const dhgrp *gg, admin *adm)
{
  const ecdh_grp *g = (const ecdh_grp *)gg;
  a_info(adm,
	 "kx-group=ec",
	 "kx-group-order-bits=%lu", (unsigned long)mp_bits(g->ei.r),
	 "kx-group-elt-bits=%lu", (unsigned long)2*g->ei.c->f->nbits,
	 A_END);
}

#ifndef NTRACE
static void addfestr(field *f, mp *x, mptext_stringctx *sc)
  { addmpstr(x, F_TYPE(f) == FTY_PRIME ? 10 : 16, sc); }

static void addintfestr(field *f, mp *x, mptext_stringctx *sc)
  { mp *t = F_OUT(f, MP_NEW, x); addfestr(f, x, sc); MP_DROP(t); }

static const char *intfestr(field *f, mp *x)
{
  mptext_stringctx sc;
  setupstr(&sc);
  addintfestr(f, x, &sc);
  return (donestr(&sc));
}

static void ecdh_tracegrp(const dhgrp *gg)
{
  const ecdh_grp *g = (const ecdh_grp *)gg;
  const ec_curve *c = g->ei.c;
  field *f = c->f;

  trace(T_CRYPTO, "crypto: group type `ec'");
  switch (F_TYPE(f)) {
    case FTY_PRIME:
      trace(T_CRYPTO, "crypto: prime field `%s'", F_NAME(f));
      trace(T_CRYPTO, "crypto: p = %s", mpstr(f->q, 10));
      break;
    case FTY_BINARY:
      trace(T_CRYPTO, "crypto: binary field `%s'", F_NAME(f));
      trace(T_CRYPTO, "crypto: degree = %lu", f->nbits - 1);
      break;
    default:
      trace(T_CRYPTO, "crypto: unknown field type! `%s'", F_NAME(f));
      break;
  }
  trace(T_CRYPTO, "crypto: curve type `%s'", EC_NAME(c));
  trace(T_CRYPTO, "crypto: curve a = %s", intfestr(f, c->a));
  trace(T_CRYPTO, "crypto: curve b = %s", intfestr(f, c->b));
  trace(T_CRYPTO, "crypto: n = %s", mpstr(g->ei.r, 10));
  trace(T_CRYPTO, "crypto: h = %s", mpstr(g->ei.h, 10));
}
#endif

static int ecdh_samegrpp(const dhgrp *gg, const dhgrp *hh)
{
  const ecdh_grp *g = (const ecdh_grp *)gg, *h = (const ecdh_grp *)hh;
  return (ec_sameinfop(&g->ei, &h->ei) &&
	  g->ser == h->ser);
}

static void ecdh_freegrp(dhgrp *gg)
{
  ecdh_grp *g = (ecdh_grp *)gg;
  EC_DESTROY(&g->P); ec_freeinfo(&g->ei);
  DESTROY(g);
}

static dhsc *ecdh_ldsc(const dhgrp *gg, const void *p, size_t sz)
{
  const ecdh_grp *g = (const ecdh_grp *)gg;
  ecdh_sc *x = CREATE(ecdh_sc);
  mp *t = mp_loadb(MP_NEW, p, sz);
  mp_div(0, &t, t, g->ei.r); x->x = t;
  return ((dhsc *)x);
}

static int ecdh_stsc(const dhgrp *gg, void *p, size_t sz, const dhsc *xx)
{
  const ecdh_sc *x = (const ecdh_sc *)xx;
  mp_storeb(x->x, p, sz);
  return (0);
}

static dhsc *ecdh_randsc(const dhgrp *gg)
{
  const ecdh_grp *g = (const ecdh_grp *)gg;
  ecdh_sc *x = CREATE(ecdh_sc);
  x->x = mprand_range(MP_NEW, g->ei.r, &rand_global, 0);
  return ((dhsc *)x);
}

#ifndef NTRACE
static const char *ecdh_scstr(const dhgrp *gg, const dhsc *xx)
{
  const ecdh_sc *x = (const ecdh_sc *)xx;
  return (mpstr(x->x, 10));
}
#endif

static void ecdh_freesc(const dhgrp *gg, dhsc *xx)
  { ecdh_sc *x = (ecdh_sc *)xx; MP_DROP(x->x); DESTROY(x); }

static dhge *ecdh_ldge(const dhgrp *gg, buf *b, int fmt)
{
  const ecdh_grp *g = (const ecdh_grp *)gg;
  ecdh_ge *Y;
  ec T = EC_INIT;

  switch (fmt) {
    case DHFMT_HASH: if (g->ser == DHSER_CONSTLEN) goto std;
    case DHFMT_VAR: if (buf_getec(b, &T)) return (0); break;
    case DHFMT_STD: std: if (ec_getraw(g->ei.c, b, &T)) return (0); break;
    default:
      abort();
  }
  EC_IN(g->ei.c, &T, &T);
  Y = CREATE(ecdh_ge); Y->Q = T;
  return ((dhge *)Y);
}

static int ecdh_stge(const dhgrp *gg, buf *b, const dhge *YY, int fmt)
{
  const ecdh_grp *g = (const ecdh_grp *)gg;
  const ecdh_ge *Y = (const ecdh_ge *)YY;
  ec T = EC_INIT;
  int rc;

  EC_OUT(g->ei.c, &T, &Y->Q);
  switch (fmt) {
    case DHFMT_HASH: if (g->ser == DHSER_CONSTLEN) goto std;
    case DHFMT_VAR: rc = buf_putec(b, &T); break;
    case DHFMT_STD: std: rc = ec_putraw(g->ei.c, b, &T); break;
    default: abort();
  }
  EC_DESTROY(&T);
  return (rc);
}

static int ecdh_checkge(const dhgrp *gg, const dhge *YY)
{
  const ecdh_grp *g = (const ecdh_grp *)gg;
  const ecdh_ge *Y = (const ecdh_ge *)YY;
  ec T = EC_INIT;
  int rc = 0;

  if (EC_ATINF(&Y->Q)) rc = -1;
  ec_imul(g->ei.c, &T, &Y->Q, g->ei.r);
  if (!EC_ATINF(&T)) rc = -1;
  EC_DESTROY(&T);
  return (rc);
}

static int ecdh_eq(const dhgrp *gg, const dhge *YY, const dhge *ZZ)
{
  const ecdh_grp *g = (const ecdh_grp *)gg;
  const ecdh_ge *Y = (const ecdh_ge *)YY, *Z = (const ecdh_ge *)ZZ;
  ec T = EC_INIT, U = EC_INIT; int rc;
  EC_FIX(g->ei.c, &T, &Y->Q); EC_FIX(g->ei.c, &U, &Z->Q);
  rc = EC_EQ(&T, &U);
  EC_DESTROY(&T); EC_DESTROY(&U);
  return (rc);
}

static dhge *ecdh_mul(const dhgrp *gg, const dhsc *xx, const dhge *YY)
{
  const ecdh_grp *g = (const ecdh_grp *)gg;
  const ecdh_sc *x = (const ecdh_sc *)xx;
  const ecdh_ge *Y = (const ecdh_ge *)YY;
  ecdh_ge *Z = CREATE(ecdh_ge); EC_CREATE(&Z->Q);

  ec_imul(g->ei.c, &Z->Q, Y ? &Y->Q : &g->P, x->x);
  return ((dhge *)Z);
}

#ifndef NTRACE
static const char *ecdh_gestr(const dhgrp *gg, const dhge *YY)
{
  const ecdh_grp *g = (const ecdh_grp *)gg;
  const ecdh_ge *Y = (const ecdh_ge *)YY;
  ec T = EC_INIT;
  field *f = g->ei.c->f;
  mptext_stringctx sc;

  if (EC_ATINF(&Y->Q)) return ("inf");
  setupstr(&sc);
  EC_OUT(g->ei.c, &T, &Y->Q);
  addfestr(f, T.x, &sc);
  addlitstr(", ", &sc);
  addfestr(f, T.y, &sc);
  EC_DESTROY(&T);
  return (donestr(&sc));
}
#endif

static void ecdh_freege(const dhgrp *gg, dhge *YY)
  { ecdh_ge *Y = (ecdh_ge *)YY; EC_DESTROY(&Y->Q); DESTROY(Y); }

/*----- The X25519 and similar groups -------------------------------------*/

#define XDHS(_)								\
  _(x25519, X25519, "curve25519", 252, 255)				\
  _(x448, X448, "ed448-goldilocks", 446, 448)

#ifdef NTRACE
#  define XDHTRACE(xdh, XDH, gname)
#else

   static const char *binstr(const octet *p, size_t sz)
   {
     char *q;

     for (q = (char *)buf_u; sz--; p++, q += 2) sprintf(q, "%02x", *p);
     return ((const char *)buf_u);
   }

#  define XDHTRACE(xdh, XDH, gname)					\
     static void xdh##_tracegrp(const dhgrp *g)				\
       { trace(T_CRYPTO, "crypto: group type `" gname "'"); }		\
									\
     static const char *xdh##_scstr(const dhgrp *g, const dhsc *xx)	\
     {									\
       const xdh##_sc *x = (const xdh##_sc *)xx;			\
       return (binstr(x->x, XDH##_KEYSZ));				\
     }									\
									\
     static const char *xdh##_gestr(const dhgrp *g, const dhge *YY)	\
     {									\
       const xdh##_ge *Y = (const xdh##_ge *)YY;			\
       return (binstr(Y->X, XDH##_PUBSZ));				\
     }
#endif

#define XDHDEF(xdh, XDH, gname, groupbits, fieldbits)			\
									\
  typedef struct xdh##_sc { octet x[XDH##_KEYSZ]; } xdh##_sc;		\
  typedef struct xdh##_ge { octet X[XDH##_PUBSZ]; } xdh##_ge;		\
									\
  XDHTRACE(xdh, XDH, gname)						\
									\
  static dhsc *xdh##_bintosc(const key_bin *b)				\
  {									\
    xdh##_sc *x;							\
									\
    if (b->sz != XDH##_KEYSZ) return (0);				\
    x = CREATE(xdh##_sc);						\
    memcpy(x->x, b->k, XDH##_KEYSZ);					\
    return ((dhsc *)x);							\
  }									\
									\
  static dhge *xdh##_bintoge(const key_bin *b)				\
  {									\
    xdh##_ge *Y;							\
									\
    if (b->sz != XDH##_PUBSZ) return (0);				\
    Y = CREATE(xdh##_ge);						\
    memcpy(Y->X, b->k, XDH##_PUBSZ);					\
    return ((dhge *)Y);							\
  }									\
									\
  KLOAD(xdh, xdh, XDH,							\
	{ kd->grp = CREATE(dhgrp);					\
	  kd->grp->scsz = XDH##_KEYSZ;					\
	},								\
	{ if ((kd->k = xdh##_bintosc(&p.priv)) == 0) {			\
	    a_format(e, "bad-private-key", A_END);			\
	    goto fail;							\
	  }								\
	},								\
	{ if ((kd->K = xdh##_bintoge(&p.pub)) == 0) {			\
	    a_format(e, "bad-public-vector", A_END);			\
	    goto fail;							\
	  }								\
	})								\
									\
  static const char *xdh##_checkgrp(const dhgrp *g)			\
    { return (0); }							\
									\
  static void xdh##_grpinfo(const dhgrp *g, admin *adm)			\
  {									\
    a_info(adm,								\
	   "kx-group=" gname,						\
	   "kx-group-order-bits=%d", (groupbits),			\
	   "kx-group-elt-bits=%d", (fieldbits),				\
	   A_END);							\
  }									\
									\
  static int xdh##_samegrpp(const dhgrp *g, const dhgrp *hh)		\
    { return (1); }							\
									\
  static void xdh##_freegrp(dhgrp *g)					\
    { DESTROY(g); }							\
									\
  static dhsc *xdh##_ldsc(const dhgrp *g, const void *p, size_t sz)	\
  {									\
    xdh##_sc *x;							\
    if (sz != XDH##_KEYSZ) return (0);					\
    x = CREATE(xdh##_sc);						\
    memcpy(x->x, p, XDH##_KEYSZ);					\
    return ((dhsc *)x);							\
  }									\
									\
  static int xdh##_stsc(const dhgrp *g, void *p, size_t sz,		\
			const dhsc *xx)					\
  {									\
    const xdh##_sc *x = (const xdh##_sc *)xx;				\
    if (sz != XDH##_KEYSZ) return (-1);					\
    memcpy(p, x->x, XDH##_KEYSZ);					\
    return (0);								\
  }									\
									\
  static dhsc *xdh##_randsc(const dhgrp *g)				\
  {									\
    xdh##_sc *x = CREATE(xdh##_sc);					\
    rand_get(RAND_GLOBAL, x->x, XDH##_KEYSZ);				\
    return ((dhsc *)x);							\
  }									\
									\
  static void xdh##_freesc(const dhgrp *g, dhsc *xx)			\
    { xdh##_sc *x = (xdh##_sc *)xx; DESTROY(x); }			\
									\
  static dhge *xdh##_ldge(const dhgrp *g, buf *b, int fmt)		\
  {									\
    xdh##_ge *Y;							\
    const octet *p;							\
									\
    if ((p = buf_get(b, XDH##_PUBSZ)) == 0) return (0);			\
    Y = CREATE(xdh##_ge); memcpy(Y->X, p, XDH##_PUBSZ);			\
    return ((dhge *)Y);							\
  }									\
									\
  static int xdh##_stge(const dhgrp *g, buf *b,				\
			const dhge *YY, int fmt)			\
  {									\
    const xdh##_ge *Y = (const xdh##_ge *)YY;				\
    return (buf_put(b, Y->X, XDH##_PUBSZ));				\
  }									\
									\
  static int xdh##_checkge(const dhgrp *g, const dhge *YY)		\
    { return (0); }							\
									\
  static int xdh##_eq(const dhgrp *g, const dhge *YY, const dhge *ZZ)	\
  {									\
    const xdh##_ge							\
      *Y = (const xdh##_ge *)YY, *Z = (const xdh##_ge *)ZZ;		\
    return (ct_memeq(Y->X, Z->X, XDH##_PUBSZ));				\
  }									\
									\
  static dhge *xdh##_mul(const dhgrp *g,				\
			 const dhsc *xx, const dhge *YY)		\
  {									\
    const xdh##_sc *x = (const xdh##_sc *)xx;				\
    const xdh##_ge *Y = (const xdh##_ge *)YY;				\
    xdh##_ge *Z = CREATE(xdh##_ge);					\
									\
    xdh(Z->X, x->x, Y ? Y->X : xdh##_base);				\
    return ((dhge *)Z);							\
  }									\
									\
  static void xdh##_freege(const dhgrp *g, dhge *YY)			\
    { xdh##_ge *Y = (xdh##_ge *)YY; DESTROY(Y); }

XDHS(XDHDEF)

#undef XDHDEF

/*----- Diffie--Hellman group table ---------------------------------------*/

const dhops dhtab[] = {

#define COMMA ,

#define DH(name, pre)							\
  { name, pre##_ldpriv, pre##_ldpub, pre##_checkgrp,			\
    pre##_grpinfo, T( pre##_tracegrp COMMA ) pre##_samegrpp,		\
    pre##_freegrp,							\
    pre##_ldsc, pre##_stsc, pre##_randsc, T( pre##_scstr COMMA )	\
    pre##_freesc,							\
    pre##_ldge, pre##_stge, pre##_checkge, pre##_eq, pre##_mul,		\
    T( pre##_gestr COMMA ) pre##_freege },				\

  DH("dh", intdh)
  DH("ec", ecdh)

#define XDHDH(xdh, XDH, gname, groupbits, fieldbits) DH(#xdh, xdh)
  XDHS(XDHDH)
#undef XDHDH

#undef DH

  { 0 }
};

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