+/*
+ * dh.c
+ */
+/*
+ * This file is Free Software. It was originally written for secnet.
+ *
+ * Copyright 1995-2003 Stephen Early
+ * Copyright 2002-2014 Ian Jackson
+ *
+ * You may redistribute secnet as a whole and/or modify it under the
+ * terms of the GNU General Public License as published by the Free
+ * Software Foundation; either version 3, or (at your option) any
+ * later version.
+ *
+ * You may redistribute this file and/or modify it under the terms of
+ * the GNU General Public License as published by the Free Software
+ * Foundation; either version 2, or (at your option) any later
+ * version.
+ *
+ * This software 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 this software; if not, see
+ * https://www.gnu.org/licenses/gpl.html.
+ */
+
#include <stdio.h>
#include <gmp.h>
#include <limits.h>
read_mpbin(&a, secret, secretlen);
- mpz_powm(&b, &st->g, &a, &st->p);
+ mpz_powm_sec(&b, &st->g, &a, &st->p);
r=write_mpstring(&b);
return r;
}
+static void write_mpbin_anomalous(MP_INT *a, uint8_t *buffer,
+ int32_t buflen)
+ /* If the BN is smaller than buflen, pads it *at the wrong end* */
+{
+ char *hb = write_mpstring(a);
+ int32_t len;
+ hex_decode(buffer, buflen, &len, hb, True);
+ if (len<buflen)
+ memset(buffer+len,0,buflen-len);
+ free(hb);
+}
+
static dh_makeshared_fn dh_makeshared;
static void dh_makeshared(void *sst, uint8_t *secret, int32_t secretlen,
cstring_t rempublic, uint8_t *sharedsecret,
read_mpbin(&a, secret, secretlen);
mpz_set_str(&b, rempublic, 16);
- mpz_powm(&c, &b, &a, &st->p);
+ mpz_powm_sec(&c, &b, &a, &st->p);
- write_mpbin(&c,sharedsecret,buflen);
+ write_mpbin_anomalous(&c,sharedsecret,buflen);
mpz_clear(&a);
mpz_clear(&b);
string_t p,g;
item_t *i;
- st=safe_malloc(sizeof(*st),"dh_apply");
+ NEW(st);
st->cl.description="dh";
st->cl.type=CL_DH;
st->cl.apply=NULL;
st->ops.len=sz;
+ st->ops.ceil_len=(mpz_sizeinbase(&st->p,2)+7)/8;
+ /* According to the docs, mpz_sizeinbase(,256) is allowed to return
+ * an answer which is 1 too large. But mpz_sizeinbase(,2) isn't. */
+
return new_closure(&st->cl);
}