X-Git-Url: https://git.distorted.org.uk/~mdw/secnet/blobdiff_plain/70dc107b6edee55270619b895f17acb66065f7ea..1fc8a4acb3ef658696038c9c4bd3c155fbc27ac3:/dh.c

diff --git a/dh.c b/dh.c
index 67ebd50..0616a43 100644
--- a/dh.c
+++ b/dh.c
@@ -1,38 +1,35 @@
-/***************************************************************************
- *
- *              Part II Project, "A secure, private IP network"
- *              Stephen Early <sde1000@cam.ac.uk>
- *   
- *
- *     $RCSfile: dh.c,v $
- *
- *  Description: Diffie-Hellman implementation
- *
- *    Copyright: (C) Stephen Early 1995
- *
- *    $Revision: 1.3 $
- *
- *        $Date: 1996/05/16 18:38:54 $
+/*
+ * dh.c
+ */
+/*
+ * This file is Free Software.  It was originally written for secnet.
  *
- *       $State: Exp $
+ * Copyright 1995-2003 Stephen Early
+ * Copyright 2002-2014 Ian Jackson
  *
- ***************************************************************************/
-
-/*
- * $Log: dh.c,v $
- * Revision 1.3  1996/05/16 18:38:54  sde1000
- * Removed unused hexdigits variable.
+ * 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.
  *
- * Revision 1.2  1996/04/14 16:33:52  sde1000
- * Moved mpbin/mpstring functions into util.c
+ * 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.
  *
- * Revision 1.1  1996/04/14 16:21:47  sde1000
- * Initial revision
+ * 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>
 
 #include "secnet.h"
 #include "util.h"
@@ -44,7 +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;
@@ -55,7 +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);
 
@@ -64,9 +61,10 @@ static string_t dh_makepublic(void *sst, uint8_t *secret, uint32_t secretlen)
     return r;
 }
 
-static void dh_makeshared(void *sst, uint8_t *secret, uint32_t secretlen,
-			  string_t rempublic, uint8_t *sharedsecret,
-			  uint32_t buflen)
+static dh_makeshared_fn dh_makeshared;
+static void dh_makeshared(void *sst, uint8_t *secret, int32_t secretlen,
+			  cstring_t rempublic, uint8_t *sharedsecret,
+			  int32_t buflen)
 {
     struct dh *st=sst;
     MP_INT a, b, c;
@@ -78,7 +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);
 
@@ -94,7 +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;
@@ -145,12 +143,24 @@ static list_t *dh_apply(closure_t *self, struct cloc loc, dict_t *context,
 	    cfgfatal(loc,"diffie-hellman","modulus must be a prime\n");
 	}
     }
-    st->ops.len=mpz_sizeinbase(&st->p,2)/8;
+
+    size_t sz=mpz_sizeinbase(&st->p,2)/8;
+    if (sz>INT_MAX) {
+	cfgfatal(loc,"diffie-hellman","modulus far too large\n");
+    }
+    if (mpz_cmp(&st->g,&st->p) >= 0) {
+	cfgfatal(loc,"diffie-hellman","generator must be less than modulus\n");
+    }
+
+    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);
 }
 
-init_module dh_module;
 void dh_module(dict_t *dict)
 {
     add_closure(dict,"diffie-hellman",dh_apply);