Fix inaccurate comments in bn_prime.c

[openssl.git] / crypto / bn / bn_word.c

diff --git a/crypto/bn/bn_word.c b/crypto/bn/bn_word.c
index 718777b5b83986352cfee2604fcd6ffc716d3b19..1af13a53fb1c81e93328da7eb0b828759a5efbad 100644 (file)
--- a/crypto/bn/bn_word.c
+++ b/crypto/bn/bn_word.c
@@ -1,58 +1,10 @@
-/* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
- * All rights reserved.
+/*
+ * Copyright 1995-2016 The OpenSSL Project Authors. All Rights Reserved.
  *
- * This package is an SSL implementation written
- * by Eric Young (eay@cryptsoft.com).
- * The implementation was written so as to conform with Netscapes SSL.
- *
- * This library is free for commercial and non-commercial use as long as
- * the following conditions are aheared to.  The following conditions
- * apply to all code found in this distribution, be it the RC4, RSA,
- * lhash, DES, etc., code; not just the SSL code.  The SSL documentation
- * included with this distribution is covered by the same copyright terms
- * except that the holder is Tim Hudson (tjh@cryptsoft.com).
- *
- * Copyright remains Eric Young's, and as such any Copyright notices in
- * the code are not to be removed.
- * If this package is used in a product, Eric Young should be given attribution
- * as the author of the parts of the library used.
- * This can be in the form of a textual message at program startup or
- * in documentation (online or textual) provided with the package.
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions
- * are met:
- * 1. Redistributions of source code must retain the copyright
- *    notice, this list of conditions and the following disclaimer.
- * 2. Redistributions in binary form must reproduce the above copyright
- *    notice, this list of conditions and the following disclaimer in the
- *    documentation and/or other materials provided with the distribution.
- * 3. All advertising materials mentioning features or use of this software
- *    must display the following acknowledgement:
- *    "This product includes cryptographic software written by
- *     Eric Young (eay@cryptsoft.com)"
- *    The word 'cryptographic' can be left out if the rouines from the library
- *    being used are not cryptographic related :-).
- * 4. If you include any Windows specific code (or a derivative thereof) from
- *    the apps directory (application code) you must include an acknowledgement:
- *    "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
- *
- * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
- * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
- * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
- * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
- * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
- * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
- * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
- * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
- * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
- * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
- * SUCH DAMAGE.
- *
- * The licence and distribution terms for any publically available version or
- * derivative of this code cannot be changed.  i.e. this code cannot simply be
- * copied and put under another distribution licence
- * [including the GNU Public Licence.]
+ * Licensed under the OpenSSL license (the "License").  You may not use
+ * this file except in compliance with the License.  You can obtain a copy
+ * in the file LICENSE in the source distribution or at
+ * https://www.openssl.org/source/license.html
  */
 
 #include "internal/cryptlib.h"
@@ -70,10 +22,32 @@ BN_ULONG BN_mod_word(const BIGNUM *a, BN_ULONG w)
     if (w == 0)
         return (BN_ULONG)-1;
 
+#ifndef BN_LLONG
+    /*
+     * If |w| is too long and we don't have BN_ULLONG then we need to fall
+     * back to using BN_div_word
+     */
+    if (w > ((BN_ULONG)1 << BN_BITS4)) {
+        BIGNUM *tmp = BN_dup(a);
+        if (tmp == NULL)
+            return (BN_ULONG)-1;
+
+        ret = BN_div_word(tmp, w);
+        BN_free(tmp);
+
+        return ret;
+    }
+#endif
+
     bn_check_top(a);
     w &= BN_MASK2;
     for (i = a->top - 1; i >= 0; i--) {
 #ifndef BN_LLONG
+        /*
+         * We can assume here that | w <= ((BN_ULONG)1 << BN_BITS4) | and so
+         * | ret < ((BN_ULONG)1 << BN_BITS4) | and therefore the shifts here are
+         * safe and will not overflow
+         */
         ret = ((ret << BN_BITS4) | ((a->d[i] >> BN_BITS4) & BN_MASK2l)) % w;
         ret = ((ret << BN_BITS4) | (a->d[i] & BN_MASK2l)) % w;
 #else
@@ -115,6 +89,8 @@ BN_ULONG BN_div_word(BIGNUM *a, BN_ULONG w)
     if ((a->top > 0) && (a->d[a->top - 1] == 0))
         a->top--;
     ret >>= j;
+    if (!a->top)
+        a->neg = 0; /* don't allow negative zero */
     bn_check_top(a);
     return (ret);
 }