b76f52c03a
Ultimately, it's better to invest effort in alternative forms of protection of key material. Calling `OPENSSL_cleanse` with a NULL pointer is not safe, but `OPENSSL_cleanse` is often called in cleanup code, especially error- handling code, where it is difficult to keep track of the NULLness of things. The likelihood of getting this wrong is compounded by the fact that, in OpenSSL upstream, calling `OPENSSL_cleanse(NULL, x)` for any `x` is safe (a no-op). BoringSSL upstream doesn't want to change its `OPENSSL_cleanse` to work like OpenSSL's. We don't want to worry about the issue. Apart from that, by inspection, it is clear that there are many places in the code that don't call `OPENSSL_clease` where they "should". It would be difficult to find all the places where a call to `OPENSSL_clease` "should" be inserted. It is unlikely we'll ever get it right. Actually, it's basically impossible to get it right using this coding pattern. See http://www.daemonology.net/blog/2014-09-06-zeroing-buffers-is-insufficient.html and https://github.com/bitcoin/secp256k1/issues/185. Besides all that, the zeroization isn't free. Especially in the case of non-MSVC platforms, it either interferes with the optimizer or it doesn't work. More importantly, thinking about how to make this approach work wastes a lot of time that could be spent actually improving the fundementals of the security of the code.
71 lines
3.3 KiB
C
71 lines
3.3 KiB
C
/* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
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* All rights reserved.
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*
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* This package is an SSL implementation written
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* by Eric Young (eay@cryptsoft.com).
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* The implementation was written so as to conform with Netscapes SSL.
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*
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* This library is free for commercial and non-commercial use as long as
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* the following conditions are aheared to. The following conditions
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* apply to all code found in this distribution, be it the RC4, RSA,
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* lhash, DES, etc., code; not just the SSL code. The SSL documentation
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* included with this distribution is covered by the same copyright terms
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* except that the holder is Tim Hudson (tjh@cryptsoft.com).
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*
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* Copyright remains Eric Young's, and as such any Copyright notices in
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* the code are not to be removed.
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* If this package is used in a product, Eric Young should be given attribution
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* as the author of the parts of the library used.
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* This can be in the form of a textual message at program startup or
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* in documentation (online or textual) provided with the package.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* "This product includes cryptographic software written by
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* Eric Young (eay@cryptsoft.com)"
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* The word 'cryptographic' can be left out if the rouines from the library
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* being used are not cryptographic related :-).
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* 4. If you include any Windows specific code (or a derivative thereof) from
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* the apps directory (application code) you must include an acknowledgement:
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* "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
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*
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* THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* The licence and distribution terms for any publically available version or
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* derivative of this code cannot be changed. i.e. this code cannot simply be
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* copied and put under another distribution licence
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* [including the GNU Public Licence.] */
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#include <openssl/mem.h>
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int CRYPTO_memcmp(const void *in_a, const void *in_b, size_t len) {
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size_t i;
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const uint8_t *a = in_a;
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const uint8_t *b = in_b;
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uint8_t x = 0;
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for (i = 0; i < len; i++) {
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x |= a[i] ^ b[i];
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}
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return x;
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}
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