151 lines
5.2 KiB
Groff
151 lines
5.2 KiB
Groff
.\" $OpenBSD: SSL_get_client_random.3,v 1.2 2018/03/24 00:55:37 schwarze Exp $
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.\" full merge up to: OpenSSL e9b77246 Jan 20 19:58:49 2017 +0100
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.\"
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.\" This file was written by Nick Mathewson <nickm@torproject.org>
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.\" Copyright (c) 2015 The OpenSSL Project. All rights reserved.
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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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.\"
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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
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.\" the documentation and/or other materials provided with the
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.\" distribution.
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.\"
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.\" 3. All advertising materials mentioning features or use of this
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.\" software must display the following acknowledgment:
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.\" "This product includes software developed by the OpenSSL Project
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.\" for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
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.\"
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.\" 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
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.\" endorse or promote products derived from this software without
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.\" prior written permission. For written permission, please contact
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.\" openssl-core@openssl.org.
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.\"
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.\" 5. Products derived from this software may not be called "OpenSSL"
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.\" nor may "OpenSSL" appear in their names without prior written
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.\" permission of the OpenSSL Project.
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.\"
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.\" 6. Redistributions of any form whatsoever must retain the following
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.\" acknowledgment:
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.\" "This product includes software developed by the OpenSSL Project
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.\" for use in the OpenSSL Toolkit (http://www.openssl.org/)"
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
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.\" EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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.\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR
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.\" ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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.\" SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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.\" LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
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.\" STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
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.\" OF THE POSSIBILITY OF SUCH DAMAGE.
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.\"
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.Dd $Mdocdate: March 24 2018 $
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.Dt SSL_GET_CLIENT_RANDOM 3
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.Os
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.Sh NAME
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.Nm SSL_get_client_random ,
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.Nm SSL_get_server_random ,
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.Nm SSL_SESSION_get_master_key
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.Nd get internal TLS handshake random values and master key
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.Sh SYNOPSIS
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.In openssl/ssl.h
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.Ft size_t
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.Fo SSL_get_client_random
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.Fa "const SSL *ssl"
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.Fa "unsigned char *out"
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.Fa "size_t outlen"
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.Fc
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.Ft size_t
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.Fo SSL_get_server_random
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.Fa "const SSL *ssl"
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.Fa "unsigned char *out"
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.Fa "size_t outlen"
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.Fc
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.Ft size_t
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.Fo SSL_SESSION_get_master_key
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.Fa "const SSL_SESSION *session"
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.Fa "unsigned char *out"
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.Fa "size_t outlen"
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.Fc
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.Sh DESCRIPTION
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.Fn SSL_get_client_random
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extracts the random value that was sent from the client to the server
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during the initial TLS handshake.
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It copies at most
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.Fa outlen
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bytes of this value into the buffer
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.Fa out .
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If
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.Fa outlen
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is zero, nothing is copied.
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.Pp
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.Fn SSL_get_server_random
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behaves the same, but extracts the random value that was sent
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from the server to the client during the initial TLS handshake.
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.Pp
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.Fn SSL_SESSION_get_master_key
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behaves the same, but extracts the master secret used to guarantee the
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security of the TLS session.
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The security of the TLS session depends on keeping the master key
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secret: do not expose it, or any information about it, to anybody.
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To calculate another secret value that depends on the master secret,
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use
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.Xr SSL_export_keying_material 3
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instead.
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.Pp
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All these functions expose internal values from the TLS handshake,
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for use in low-level protocols.
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Avoid using them unless implementing a feature
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that requires access to the internal protocol details.
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.Pp
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Despite the names of
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.Fn SSL_get_client_random
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and
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.Fn SSL_get_server_random ,
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they are not random number generators.
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Instead, they return the mostly-random values that were already
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generated and used in the TLS protocol.
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.Pp
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In current versions of the TLS protocols,
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the length of client_random and server_random is always
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.Dv SSL3_RANDOM_SIZE
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bytes.
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Support for other
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.Fa outlen
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arguments is provided for the unlikely event that a future
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version or variant of TLS uses some other length.
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.Pp
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Finally, though the client_random and server_random values are called
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.Dq random ,
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many TLS implementations generate four bytes of those values
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based on their view of the current time.
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.Sh RETURN VALUES
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If
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.Fa outlen
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is greater than 0, these functions return the number of bytes
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actually copied, which is less than or equal to
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.Fa outlen .
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If
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.Fa outlen
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is 0, these functions return the maximum number of bytes they would
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copy \(em that is, the length of the underlying field.
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.Sh SEE ALSO
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.Xr ssl 3 ,
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.Xr SSL_export_keying_material 3 ,
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.Xr SSL_SESSION_get_id 3 ,
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.Xr SSL_SESSION_get_time 3 ,
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.Xr SSL_SESSION_new 3
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.Sh HISTORY
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These functions first appeared in OpenSSL 1.1.0
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and have been available since
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.Ox 6.3 .
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