X-Git-Url: https://git.distorted.org.uk/~mdw/secnet/blobdiff_plain/59230b9b9fc44453f24c6b3cf33a0f4c570a3563..1fc8a4acb3ef658696038c9c4bd3c155fbc27ac3:/dh.c

diff --git a/dh.c b/dh.c
index fff9b99..0616a43 100644
--- a/dh.c
+++ b/dh.c
@@ -1,3 +1,32 @@
+/*
+ * 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>
@@ -12,7 +41,7 @@ struct dh {
     MP_INT p,g; /* prime modulus and generator */
 };
 
-static string_t dh_makepublic(void *sst, uint8_t *secret, uint32_t secretlen)
+static string_t dh_makepublic(void *sst, uint8_t *secret, int32_t secretlen)
 {
     struct dh *st=sst;
     string_t r;
@@ -23,7 +52,7 @@ static string_t dh_makepublic(void *sst, uint8_t *secret, uint32_t secretlen)
 
     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);
 
@@ -33,9 +62,9 @@ static string_t dh_makepublic(void *sst, uint8_t *secret, uint32_t secretlen)
 }
 
 static dh_makeshared_fn dh_makeshared;
-static void dh_makeshared(void *sst, uint8_t *secret, uint32_t secretlen,
+static void dh_makeshared(void *sst, uint8_t *secret, int32_t secretlen,
 			  cstring_t rempublic, uint8_t *sharedsecret,
-			  uint32_t buflen)
+			  int32_t buflen)
 {
     struct dh *st=sst;
     MP_INT a, b, c;
@@ -47,7 +76,7 @@ static void dh_makeshared(void *sst, uint8_t *secret, uint32_t secretlen,
     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);
 
@@ -63,7 +92,7 @@ static list_t *dh_apply(closure_t *self, struct cloc loc, dict_t *context,
     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;
@@ -125,6 +154,10 @@ static list_t *dh_apply(closure_t *self, struct cloc loc, dict_t *context,
 
     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);
 }