204 lines
6.5 KiB
Groff
204 lines
6.5 KiB
Groff
|
.\" FreeSec: libcrypt for NetBSD
|
||
|
|
.\"
|
||
|
|
.\" Copyright (c) 1994 David Burren
|
||
|
|
.\" All rights reserved.
|
||
|
|
.\"
|
||
|
|
.\" Redistribution and use in source and binary forms, with or without
|
||
|
|
.\" modification, are permitted provided that the following conditions
|
||
|
|
.\" are met:
|
||
|
|
.\" 1. Redistributions of source code must retain the above copyright
|
||
|
|
.\" notice, this list of conditions and the following disclaimer.
|
||
|
|
.\" 2. Redistributions in binary form must reproduce the above copyright
|
||
|
|
.\" notice, this list of conditions and the following disclaimer in the
|
||
|
|
.\" documentation and/or other materials provided with the distribution.
|
||
|
|
.\" 4. Neither the name of the author nor the names of other contributors
|
||
|
|
.\" may be used to endorse or promote products derived from this software
|
||
|
|
.\" without specific prior written permission.
|
||
|
|
.\"
|
||
|
|
.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
|
||
|
|
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
|
||
|
|
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
|
||
|
|
.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
|
||
|
|
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
|
||
|
|
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
|
||
|
|
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
|
||
|
|
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
|
||
|
|
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
|
||
|
|
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
|
||
|
|
.\" SUCH DAMAGE.
|
||
|
|
.\"
|
||
|
|
.\" $FreeBSD$
|
||
|
|
.\"
|
||
|
|
.\" Manual page, using -mandoc macros
|
||
|
|
.\"
|
||
|
|
.Dd January 19, 1997
|
||
|
|
.Dt CRYPT 3
|
||
|
|
.Os "FreeSec 1.0"
|
||
|
|
.Sh NAME
|
||
|
|
.Nm crypt
|
||
|
|
.Nd Trapdoor encryption
|
||
|
|
.Sh SYNOPSIS
|
||
|
|
.Ft char
|
||
|
|
.Fn *crypt "const char *key" "const char *salt"
|
||
|
|
.Sh DESCRIPTION
|
||
|
|
The
|
||
|
|
.Fn crypt
|
||
|
|
function performs password hashing with additional code added to
|
||
|
|
deter key search attempts. Different algorithms can be used to
|
||
|
|
in the hash.
|
||
|
|
.\"
|
||
|
|
.\" NOTICE:
|
||
|
|
.\" If you add more algorithms, make sure to update this list
|
||
|
|
.\" and the default used for the Traditional format, below.
|
||
|
|
.\"
|
||
|
|
Currently these include the
|
||
|
|
.Tn NBS
|
||
|
|
Data Encryption Standard (DES), MD5 or SHS. The algorithm
|
||
|
|
used will depend upon the format of the Salt--following the Modular
|
||
|
|
Crypt Format (MCF)--and if DES is installed or not.
|
||
|
|
.Pp
|
||
|
|
The first argument to
|
||
|
|
.Nm crypt
|
||
|
|
is the data to hash (usually a password), in a
|
||
|
|
.Dv null Ns -terminated
|
||
|
|
string.
|
||
|
|
The second is the salt, in one of three forms:
|
||
|
|
.Pp
|
||
|
|
.Bl -tag -width Traditional -compact -offset indent
|
||
|
|
.It Extended
|
||
|
|
If it begins with an underscore (``_'') then the DES Extended Format
|
||
|
|
is used in interpreting both the the key and the salt, as outlined below.
|
||
|
|
.It Modular
|
||
|
|
If it begins with the string ``$digit$'' then the Modular Crypt Format
|
||
|
|
is used, as outlined below.
|
||
|
|
.It Traditional
|
||
|
|
If neither of the above is true, it assumes the Traditional Format,
|
||
|
|
using the entire string as the salt (or the first portion).
|
||
|
|
.El
|
||
|
|
.Pp
|
||
|
|
All routines are designed to be time-consuming. A brief test on a
|
||
|
|
Pentium 166/MMX shows the DES crypt to do approximately 2640 crypts
|
||
|
|
a CPU second, MD5 to do about 62 crypts a CPU second and SHA1
|
||
|
|
to do about 18 crypts a CPU second.
|
||
|
|
.Ss DES Extended Format:
|
||
|
|
.Pp
|
||
|
|
The
|
||
|
|
.Ar key
|
||
|
|
is divided into groups of 8 characters (the last group is null-padded)
|
||
|
|
and the low-order 7 bits of each each character (56 bits per group) are
|
||
|
|
used to form the DES key as follows:
|
||
|
|
the first group of 56 bits becomes the initial DES key.
|
||
|
|
For each additional group, the XOR of the encryption of the current DES
|
||
|
|
key with itself and the group bits becomes the next DES key.
|
||
|
|
.Pp
|
||
|
|
The salt is a 9-character array consisting of an underscore followed
|
||
|
|
by 4 bytes of iteration count and 4 bytes of salt.
|
||
|
|
These are encoded as printable characters, 6 bits per character,
|
||
|
|
least significant character first.
|
||
|
|
The values 0 to 63 are encoded as ``./0-9A-Za-z''.
|
||
|
|
This allows 24 bits for both
|
||
|
|
.Fa count
|
||
|
|
and
|
||
|
|
.Fa salt .
|
||
|
|
.Pp
|
||
|
|
The
|
||
|
|
.Fa salt
|
||
|
|
introduces disorder in the
|
||
|
|
.Tn DES
|
||
|
|
algorithm in one of 16777216 or 4096 possible ways
|
||
|
|
(ie. with 24 or 12 bits: if bit
|
||
|
|
.Em i
|
||
|
|
of the
|
||
|
|
.Ar salt
|
||
|
|
is set, then bits
|
||
|
|
.Em i
|
||
|
|
and
|
||
|
|
.Em i+24
|
||
|
|
are swapped in the
|
||
|
|
.Tn DES
|
||
|
|
E-box output).
|
||
|
|
.Pp
|
||
|
|
The DES key is used to encrypt a 64-bit constant using
|
||
|
|
.Ar count
|
||
|
|
iterations of
|
||
|
|
.Tn DES .
|
||
|
|
The value returned is a
|
||
|
|
.Dv null Ns -terminated
|
||
|
|
string, 20 or 13 bytes (plus null) in length, consisting of the
|
||
|
|
.Ar salt
|
||
|
|
followed by the encoded 64-bit encryption.
|
||
|
|
.Ss "Modular" crypt:
|
||
|
|
.Pp
|
||
|
|
If the salt begins with the string
|
||
|
|
.Fa $digit$
|
||
|
|
then the Modular Crypt Format is used. The
|
||
|
|
.Fa digit
|
||
|
|
represents which algorithm is used in encryption. Following the token is
|
||
|
|
the actual salt to use in the encryption. The length of the salt is limited
|
||
|
|
to 16 characters--because the length of the returned output is also limited
|
||
|
|
(_PASSWORD_LEN). The salt must be terminated with the end of the string
|
||
|
|
(NULL) or a dollar sign. Any characters after the dollar sign are ignored.
|
||
|
|
.Pp
|
||
|
|
Currently supported algorithms are:
|
||
|
|
.Pp
|
||
|
|
.Bl -tag -width 012345678 -compact -offset indent
|
||
|
|
.It 1
|
||
|
|
MD5
|
||
|
|
.It 3
|
||
|
|
SHA1
|
||
|
|
.El
|
||
|
|
.Pp
|
||
|
|
Other crypt formats may be easilly added. An example salt would be:
|
||
|
|
.Bl -tag -offset indent
|
||
|
|
.It Cm "$3$thesalt$rest"
|
||
|
|
.El
|
||
|
|
.Pp
|
||
|
|
.Ss "Traditional" crypt:
|
||
|
|
.Pp
|
||
|
|
The algorithm used will depend upon whether DES is installed or not. If it is,
|
||
|
|
DES will be used. Otherwise, the best algorithm is used, which is currently
|
||
|
|
.\"
|
||
|
|
.\" NOTICE: Also make sure to update this
|
||
|
|
.\"
|
||
|
|
SHA-1.
|
||
|
|
.Pp
|
||
|
|
How the salt is used will depend upon the algorithm for the hash. For
|
||
|
|
best results, specify at least two characters of salt.
|
||
|
|
.Sh RETURN VALUES
|
||
|
|
.Pp
|
||
|
|
.Fn crypt
|
||
|
|
returns a pointer to the encrypted value on success, and NULL on failure.
|
||
|
|
Note: this is not a standard behaviour, AT&T
|
||
|
|
.Fn crypt
|
||
|
|
will always return a pointer to a string.
|
||
|
|
.Sh SEE ALSO
|
||
|
|
.Xr login 1 ,
|
||
|
|
.Xr passwd 1 ,
|
||
|
|
.Xr getpass 3 ,
|
||
|
|
.Xr passwd 5 ,
|
||
|
|
.Xr shs 3 ,
|
||
|
|
.Sh BUGS
|
||
|
|
The
|
||
|
|
.Fn crypt
|
||
|
|
function returns a pointer to static data, and subsequent calls to
|
||
|
|
.Fn crypt
|
||
|
|
will modify the same data.
|
||
|
|
.Sh HISTORY
|
||
|
|
A rotor-based
|
||
|
|
.Fn crypt
|
||
|
|
function appeared in
|
||
|
|
.At v6 .
|
||
|
|
The current style
|
||
|
|
.Fn crypt
|
||
|
|
first appeared in
|
||
|
|
.At v7 .
|
||
|
|
.Pp
|
||
|
|
The DES section of the code (FreeSec 1.0) was developed outside the United
|
||
|
|
States of America as an unencumbered replacement for the U.S.-only NetBSD
|
||
|
|
libcrypt encryption library.
|
||
|
|
Users should be aware that this code (and programs staticly linked with it)
|
||
|
|
may not be exported from the U.S., although it apparently can be imported.
|
||
|
|
.Sh AUTHORS
|
||
|
|
Originally written by David Burren <davidb@werj.com.au>, later additions
|
||
|
|
and changes by Brandon Gillespie, Poul-henning Kamp and Mark R V Murray.
|