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d7222a4956
Various cryptographic operations leak timing information if comparisons are not executed in constant time. This change adds DCRYPTO_equals(), a constant runtime comparator. Also replace crypto related callsites that used memcmp() as a binary comparator. BUG=none BRANCH=none TEST=tcg tests pass Change-Id: I3d3da3c0524c3a349d60675902d1f2d338ad455f Signed-off-by: nagendra modadugu <ngm@google.com> Reviewed-on: https://chromium-review.googlesource.com/410163 Commit-Ready: Nagendra Modadugu <ngm@google.com> Tested-by: Nagendra Modadugu <ngm@google.com> Reviewed-by: Marius Schilder <mschilder@chromium.org> Reviewed-by: Bill Richardson <wfrichar@chromium.org>
21 lines
439 B
C
21 lines
439 B
C
/* Copyright 2016 The Chromium OS Authors. All rights reserved.
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* Use of this source code is governed by a BSD-style license that can be
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* found in the LICENSE file.
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*/
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#include "dcrypto.h"
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/* Constant time comparator. */
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int DCRYPTO_equals(const void *a, const void *b, size_t len)
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{
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size_t i;
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const uint8_t *pa = a;
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const uint8_t *pb = b;
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uint8_t diff = 0;
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for (i = 0; i < len; i++)
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diff |= pa[i] ^ pb[i];
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return !diff;
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}
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