1130b656e5
This will make a number of things easier in the future, as well as (finally!) avoiding the Id-smashing problem which has plagued developers for so long. Boy, I'm glad we're not using sup anymore. This update would have been insane otherwise.
160 lines
4.9 KiB
Groff
160 lines
4.9 KiB
Groff
.\" FreeSec: libcrypt for NetBSD
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.\"
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.\" Copyright (c) 1994 David Burren
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.\" 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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.\" 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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.\" 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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.\" 4. Neither the name of the author nor the names of other contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``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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.\" $FreeBSD$
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.\"
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.\" Manual page, using -mandoc macros
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.\"
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.Dd March 9, 1994
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.Dt CRYPT 3
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.Os "FreeSec 1.0"
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.Sh NAME
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.Nm crypt
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.Nd DES trapdoor encryption
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.Sh SYNOPSIS
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.Ft char
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.Fn *crypt "const char *key" "const char *setting"
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.Sh DESCRIPTION
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The
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.Fn crypt
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function performs password encryption, based on the
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.Tn NBS
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Data Encryption Standard (DES).
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Additional code has been added to deter key search attempts.
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The first argument to
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.Nm crypt
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is a
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.Dv null Ns -terminated
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string, typically a user's typed password.
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The second is in one of three forms:
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if it begins with an underscore (``_'') then an extended format is used
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in interpreting both the the key and the setting, as outlined below.
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if it begins with the string ``$1$'' then an exportable format is used.
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.Ss Extended crypt:
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.Pp
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The
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.Ar key
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is divided into groups of 8 characters (the last group is null-padded)
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and the low-order 7 bits of each each character (56 bits per group) are
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used to form the DES key as follows:
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the first group of 56 bits becomes the initial DES key.
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For each additional group, the XOR of the encryption of the current DES
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key with itself and the group bits becomes the next DES key.
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.Pp
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The setting is a 9-character array consisting of an underscore followed
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by 4 bytes of iteration count and 4 bytes of salt.
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These are encoded as printable characters, 6 bits per character,
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least significant character first.
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The values 0 to 63 are encoded as ``./0-9A-Za-z''.
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This allows 24 bits for both
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.Fa count
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and
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.Fa salt .
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.Ss "Traditional" crypt:
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.Pp
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The first 8 bytes of the key are null-padded, and the low-order 7 bits of
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each character is used to form the 56-bit
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.Tn DES
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key.
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.Pp
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The setting is a 2-character array of the ASCII-encoded salt.
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Thus only 12 bits of
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.Fa salt
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are used.
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.Fa count
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is set to 25.
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.Ss "FreeBSD" or "Exportable" crypt:
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.Pp
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If the salt begins with ``$1$'' then the freely exportable
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.Tn MD5
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algorithm is used to calculate a hash value, from which the password string
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is generated. The
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.Tn MD5
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derived routine is designed to be time-consuming like the DES based version.
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.Ss Algorithm:
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.Pp
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The
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.Fa salt
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introduces disorder in the
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.Tn DES
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algorithm in one of 16777216 or 4096 possible ways
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(ie. with 24 or 12 bits: if bit
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.Em i
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of the
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.Ar salt
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is set, then bits
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.Em i
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and
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.Em i+24
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are swapped in the
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.Tn DES
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E-box output).
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.Pp
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The DES key is used to encrypt a 64-bit constant using
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.Ar count
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iterations of
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.Tn DES .
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The value returned is a
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.Dv null Ns -terminated
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string, 20 or 13 bytes (plus null) in length, consisting of the
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.Ar setting
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followed by the encoded 64-bit encryption.
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.Pp
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The function
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.Fn crypt
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returns a pointer to the encrypted value on success, and NULL on failure.
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.Sh SEE ALSO
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.Xr login 1 ,
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.Xr passwd 1 ,
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.Xr getpass 3 ,
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.Xr passwd 5
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.Sh BUGS
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The
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.Fn crypt
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function returns a pointer to static data, and subsequent calls to
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.Fn crypt
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will modify the same object.
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.Sh HISTORY
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A rotor-based
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.Fn crypt
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function appeared in
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.At v6 .
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The current style
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.Fn crypt
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first appeared in
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.At v7 .
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.Pp
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This library (FreeSec 1.0) was developed outside the United States of America
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as an unencumbered replacement for the U.S.-only NetBSD libcrypt encryption
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library.
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Users should be aware that this code (and programs staticly linked with it)
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may not be exported from the U.S., although it apparently can be imported.
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.Sh AUTHOR
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David Burren <davidb@werj.com.au>
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