X-Git-Url: https://git.distorted.org.uk/~mdw/secnet/blobdiff_plain/389070fed67552c613ce5afd3cdb436f8f8c538f..86420bb75f19f628ffd2d8ff9964e59ed99e3187:/dh.c

diff --git a/dh.c b/dh.c
index 91d08ce..4300a91 100644
--- a/dh.c
+++ b/dh.c
@@ -1,5 +1,35 @@
+/*
+ * 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>
 
 #include "secnet.h"
 #include "util.h"
@@ -11,7 +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;
@@ -32,9 +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;
@@ -62,7 +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;
@@ -113,7 +143,20 @@ 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);
 }