111 lines
4.1 KiB
Plaintext
111 lines
4.1 KiB
Plaintext
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.\" This file is dual-licensed. Choose whichever you want.
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.\"
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.\" The first licence is a regular 2-clause BSD licence. The second licence
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.\" is the CC-0 from Creative Commons. It is intended to release Monocypher
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.\" to the public domain. The BSD licence serves as a fallback option.
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.\"
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.\" SPDX-License-Identifier: BSD-2-Clause OR CC0-1.0
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.\"
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.\" ----------------------------------------------------------------------------
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.\"
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.\" Copyright (c) 2017-2019 Loup Vaillant
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.\" Copyright (c) 2017-2018 Michael Savage
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.\" Copyright (c) 2017, 2019 Fabio Scotoni
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.\" All rights reserved.
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.\"
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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 are
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.\" met:
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.\"
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\"
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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
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.\" distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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.\" "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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.\" LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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.\" A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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.\" HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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.\" SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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.\" LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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.\" OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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.\"
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.\" ----------------------------------------------------------------------------
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.\"
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.\" Written in 2017-2019 by Loup Vaillant, Michael Savage and Fabio Scotoni
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.\"
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.\" To the extent possible under law, the author(s) have dedicated all copyright
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.\" and related neighboring rights to this software to the public domain
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.\" worldwide. This software is distributed without any warranty.
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.\"
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.\" You should have received a copy of the CC0 Public Domain Dedication along
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.\" with this software. If not, see
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.\" <https://creativecommons.org/publicdomain/zero/1.0/>
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.\"
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.Dd December 12, 2019
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.Dt CRYPTO_WIPE 3MONOCYPHER
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.Os
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.Sh NAME
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.Nm crypto_wipe
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.Nd wipe data from memory
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.Sh SYNOPSIS
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.In monocypher.h
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.Ft void
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.Fo crypto_wipe
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.Fa "void *secret"
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.Fa "size_t secret_size"
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.Fc
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.Sh DESCRIPTION
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.Fn crypto_wipe
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securely erases sensitive data in memory.
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.Pp
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Sensitive data (such as cryptographic keys or secret plaintexts) should
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be erased from memory as early as possible, to minimise the window in
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which it can be leaked.
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Standard functions like memset and bzero are not safe to use, as the
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compiler may decide they have no effect and optimise them out.
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.Pp
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The arguments are:
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.Bl -tag -width Ds
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.It Fa secret
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The buffer to erase.
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.It Fa secret_size
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The number of bytes to erase from the buffer.
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Normally this is the size of the entire buffer.
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.El
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.Pp
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Monocypher will wipe its context structs when finalizing an operation
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such as signing or decrypting.
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When using direct interfaces like
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.Xr crypto_lock 3monocypher ,
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these context structs are invisible to you.
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They are exposed in incremental interfaces like
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.Xr crypto_blake2b_init 3monocypher .
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The original key buffer does not get automatically wiped.
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When using incremental interfaces, you may want to wipe the original key
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buffers immediately after calling the respective init function.
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.Pp
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Using
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.Fn crypto_wipe
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alone may not suffice for security.
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It is recommended to lock down relevant memory regions as well.
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Refer to
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.Xr intro 3monocypher
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for instructions on how to lock down memory on common operating systems.
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.Sh RETURN VALUES
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This function returns nothing.
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.Sh SEE ALSO
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.Xr intro 3monocypher
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.Sh HISTORY
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The
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.Fn crypto_wipe
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function first appeared in Monocypher 1.1.0.
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