[apple/libc.git] / gen / crypt.3

.\" $OpenBSD: crypt.3,v 1.5 1996/12/10 09:06:09 deraadt Exp $
.\"
.\" FreeSec: libcrypt
.\"
.\" 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.
.\"
.\" Manual page, using -mandoc macros
.\"
.Dd March 9, 1994
.Dt CRYPT 3
.Os "FreeSec 1.0"
.Sh NAME
.Nm crypt ,
.Nm encrypt ,
.Nm setkey
.Nd DES encryption
.Sh SYNOPSIS
.Fd #include <unistd.h>
.Ft char *
.Fo crypt
.Fa "const char *key"
.Fa "const char *salt"
.Fc
.Ft void
.Fo encrypt
.Fa "char *block"
.Fa "int edflag"
.Fc
.Fd #include <stdlib.h>
.Ft void
.Fo setkey
.Fa "const char *key"
.Fc
.Sh DESCRIPTION
The
.Fn crypt
function performs password encryption, based on the
.Tn NBS
Data Encryption Standard (DES).
Additional code has been added to deter key search attempts.
The first argument to
.Fn crypt
is a
.Dv null Ns -terminated
string, typically a user's typed password.
The second is in one of two forms:
if it begins with an underscore (``_''), an extended format is used
in interpreting both the key and the salt value, as outlined below.
.Ss Extended crypt:
.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
.Ar 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 .
.Ss "Traditional" crypt:
.Pp
The first 8 bytes of the key are null-padded, and the low-order 7 bits of
each character is used to form the 56-bit
.Tn DES
key.
.Pp
The
.Fa salt
is a 2-character array of the ASCII-encoded salt.
Thus, only 12 bits of salt are used.
.Fa count
is set to 25.
.Ss Algorithm:
.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.
.Pp
The functions,
.Fn encrypt
and
.Fn setkey
provide access to the
.Tn DES
algorithm itself.
.Fn setkey
is passed a 64-byte array of binary values (numeric 0 or 1).
A 56-bit key is extracted from this array by dividing the
array into groups of 8 and ignoring the last bit in each group.
That bit is reserved for a byte parity check by DES, but is ignored
by these functions.
.Pp
The
.Fa block
argument to
.Fn encrypt
is also a 64-byte array of binary values.
If the value of
.Fa edflag
is 0,
.Fa block
is encrypted; otherwise, it is decrypted.
The result is returned in the original array
.Fa block ,
after using the key specified by
.Fn setkey
to process it.
.Pp
The function
.Fn crypt
returns a pointer to the encrypted value on success, and NULL on failure.
.Pp
The
.Fn crypt
and
.Fn setkey
functions all manipulate the same key space.
.Sh SEE ALSO
.Xr login 1 ,
.Xr passwd 1 ,
.Xr getpass 3 ,
.Xr compat 5 ,
.Xr passwd 5
.Sh LEGACY SYNOPSIS
.Fd #include <unistd.h>
.Pp
.Ft int
.br
.Fo encrypt
.Fa "char *block"
.Fa "int edflag"
.Fc ;
.Pp
The function
.Fn encrypt
returns 0 on success and 1 on failure.
.Pp
.Ft void
.br
.Fo setkey
.Fa "const char *key"
.Fc ;
.Pp
The include file
.In unistd.h
is necessary and sufficient for the
.Fn setkey
function.
.Sh BUGS
The
.Fn crypt
function returns a pointer to static data, and subsequent calls to
.Fn crypt
will modify the same object.
.Sh HISTORY
A rotor-based
.Fn crypt
function appeared in
.At v6 .
The current style
.Fn crypt
first appeared in
.At v7 .
.Pp
This library (FreeSec 1.0) was developed outside the United States of America
as an unencumbered replacement for the U.S.-only libcrypt encryption
library.
Programs linked against the 
.Fn crypt
interface may be exported from the U.S.A. only if they use 
.Fn crypt
solely for authentication purposes and avoid use of
the other programmer interfaces listed above. Special care has been taken
in the library so that programs which only use the 
.Fn crypt
interface do not pull in the other components.
.Sh AUTHOR
David Burren <davidb@werj.com.au>
Commit	Line	Data
59e0d9fe A	1	.\" $OpenBSD: crypt.3,v 1.5 1996/12/10 09:06:09 deraadt Exp $
	2	.\"
	3	.\" FreeSec: libcrypt
	4	.\"
	5	.\" Copyright (c) 1994 David Burren
	6	.\" All rights reserved.
	7	.\"
	8	.\" Redistribution and use in source and binary forms, with or without
	9	.\" modification, are permitted provided that the following conditions
	10	.\" are met:
	11	.\" 1. Redistributions of source code must retain the above copyright
	12	.\" notice, this list of conditions and the following disclaimer.
	13	.\" 2. Redistributions in binary form must reproduce the above copyright
	14	.\" notice, this list of conditions and the following disclaimer in the
	15	.\" documentation and/or other materials provided with the distribution.
	16	.\" 4. Neither the name of the author nor the names of other contributors
	17	.\" may be used to endorse or promote products derived from this software
	18	.\" without specific prior written permission.
	19	.\"
	20	.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
	21	.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
	22	.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
	23	.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
	24	.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
	25	.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
	26	.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
	27	.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
	28	.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
	29	.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
	30	.\" SUCH DAMAGE.
	31	.\"
	32	.\" Manual page, using -mandoc macros
	33	.\"
	34	.Dd March 9, 1994
	35	.Dt CRYPT 3
	36	.Os "FreeSec 1.0"
	37	.Sh NAME
	38	.Nm crypt ,
59e0d9fe	39	.Nm encrypt ,
224c7076	40	.Nm setkey
59e0d9fe A	41	.Nd DES encryption
	42	.Sh SYNOPSIS
	43	.Fd #include <unistd.h>
224c7076 A	44	.Ft char *
	45	.Fo crypt
	46	.Fa "const char *key"
	47	.Fa "const char *salt"
	48	.Fc
59e0d9fe	49	.Ft void
224c7076 A	50	.Fo encrypt
	51	.Fa "char *block"
	52	.Fa "int edflag"
	53	.Fc
	54	.Fd #include <stdlib.h>
59e0d9fe	55	.Ft void
224c7076 A	56	.Fo setkey
	57	.Fa "const char *key"
	58	.Fc
59e0d9fe A	59	.Sh DESCRIPTION
	60	The
	61	.Fn crypt
	62	function performs password encryption, based on the
	63	.Tn NBS
	64	Data Encryption Standard (DES).
	65	Additional code has been added to deter key search attempts.
	66	The first argument to
	67	.Fn crypt
	68	is a
	69	.Dv null Ns -terminated
	70	string, typically a user's typed password.
	71	The second is in one of two forms:
224c7076 A	72	if it begins with an underscore (``_''), an extended format is used
224c7076 A	73	in interpreting both the key and the salt value, as outlined below.
59e0d9fe A	74	.Ss Extended crypt:
	75	.Pp
	76	The
	77	.Ar key
	78	is divided into groups of 8 characters (the last group is null-padded)
	79	and the low-order 7 bits of each each character (56 bits per group) are
	80	used to form the DES key as follows:
	81	the first group of 56 bits becomes the initial DES key.
	82	For each additional group, the XOR of the encryption of the current DES
	83	key with itself and the group bits becomes the next DES key.
	84	.Pp
224c7076 A	85	The
	86	.Ar salt
	87	is a 9-character array consisting of an underscore, followed
59e0d9fe A	88	by 4 bytes of iteration count and 4 bytes of salt.
	89	These are encoded as printable characters, 6 bits per character,
	90	least significant character first.
	91	The values 0 to 63 are encoded as ``./0-9A-Za-z''.
	92	This allows 24 bits for both
	93	.Fa count
	94	and
	95	.Fa salt .
	96	.Ss "Traditional" crypt:
	97	.Pp
	98	The first 8 bytes of the key are null-padded, and the low-order 7 bits of
	99	each character is used to form the 56-bit
	100	.Tn DES
	101	key.
	102	.Pp
224c7076	103	The
59e0d9fe	104	.Fa salt
224c7076 A	105	is a 2-character array of the ASCII-encoded salt.
224c7076 A	106	Thus, only 12 bits of salt are used.
59e0d9fe A	107	.Fa count
	108	is set to 25.
	109	.Ss Algorithm:
	110	.Pp
	111	The
	112	.Fa salt
	113	introduces disorder in the
	114	.Tn DES
	115	algorithm in one of 16777216 or 4096 possible ways
	116	(ie. with 24 or 12 bits: if bit
	117	.Em i
	118	of the
	119	.Ar salt
	120	is set, then bits
	121	.Em i
	122	and
	123	.Em i+24
	124	are swapped in the
	125	.Tn DES
	126	E-box output).
	127	.Pp
224c7076	128	The DES key is used to encrypt a 64-bit constant, using
59e0d9fe A	129	.Ar count
	130	iterations of
	131	.Tn DES .
	132	The value returned is a
	133	.Dv null Ns -terminated
	134	string, 20 or 13 bytes (plus null) in length, consisting of the
224c7076	135	.Ar salt ,
59e0d9fe A	136	followed by the encoded 64-bit encryption.
	137	.Pp
	138	The functions,
224c7076	139	.Fn encrypt
59e0d9fe	140	and
224c7076	141	.Fn setkey
59e0d9fe A	142	provide access to the
	143	.Tn DES
	144	algorithm itself.
	145	.Fn setkey
	146	is passed a 64-byte array of binary values (numeric 0 or 1).
	147	A 56-bit key is extracted from this array by dividing the
224c7076	148	array into groups of 8 and ignoring the last bit in each group.
59e0d9fe A	149	That bit is reserved for a byte parity check by DES, but is ignored
	150	by these functions.
	151	.Pp
	152	The
	153	.Fa block
	154	argument to
	155	.Fn encrypt
	156	is also a 64-byte array of binary values.
	157	If the value of
224c7076	158	.Fa edflag
59e0d9fe A	159	is 0,
59e0d9fe A	160	.Fa block
224c7076	161	is encrypted; otherwise, it is decrypted.
59e0d9fe	162	The result is returned in the original array
224c7076	163	.Fa block ,
59e0d9fe A	164	after using the key specified by
	165	.Fn setkey
	166	to process it.
	167	.Pp
59e0d9fe A	168	The function
	169	.Fn crypt
	170	returns a pointer to the encrypted value on success, and NULL on failure.
59e0d9fe A	171	.Pp
59e0d9fe A	172	The
224c7076	173	.Fn crypt
59e0d9fe	174	and
224c7076	175	.Fn setkey
59e0d9fe A	176	functions all manipulate the same key space.
	177	.Sh SEE ALSO
	178	.Xr login 1 ,
	179	.Xr passwd 1 ,
	180	.Xr getpass 3 ,
224c7076	181	.Xr compat 5 ,
59e0d9fe	182	.Xr passwd 5
224c7076 A	183	.Sh LEGACY SYNOPSIS
	184	.Fd #include <unistd.h>
	185	.Pp
	186	.Ft int
	187	.br
	188	.Fo encrypt
	189	.Fa "char *block"
	190	.Fa "int edflag"
	191	.Fc ;
	192	.Pp
	193	The function
	194	.Fn encrypt
	195	returns 0 on success and 1 on failure.
	196	.Pp
	197	.Ft void
	198	.br
	199	.Fo setkey
	200	.Fa "const char *key"
	201	.Fc ;
	202	.Pp
	203	The include file
	204	.In unistd.h
	205	is necessary and sufficient for the
	206	.Fn setkey
	207	function.
59e0d9fe A	208	.Sh BUGS
	209	The
	210	.Fn crypt
	211	function returns a pointer to static data, and subsequent calls to
	212	.Fn crypt
	213	will modify the same object.
	214	.Sh HISTORY
	215	A rotor-based
	216	.Fn crypt
	217	function appeared in
	218	.At v6 .
	219	The current style
	220	.Fn crypt
	221	first appeared in
	222	.At v7 .
	223	.Pp
	224	This library (FreeSec 1.0) was developed outside the United States of America
	225	as an unencumbered replacement for the U.S.-only libcrypt encryption
	226	library.
	227	Programs linked against the
	228	.Fn crypt
	229	interface may be exported from the U.S.A. only if they use
	230	.Fn crypt
	231	solely for authentication purposes and avoid use of
	232	the other programmer interfaces listed above. Special care has been taken
	233	in the library so that programs which only use the
	234	.Fn crypt
	235	interface do not pull in the other components.
	236	.Sh AUTHOR
	237	David Burren <davidb@werj.com.au>