.\" $OpenBSD: crypt_checkpass.3,v 1.13 2021/10/29 10:54:33 deraadt Exp $
.\"
.\" Copyright (c) 2014 Ted Unangst <tedu@openbsd.org>
.\"
.\" Permission to use, copy, modify, and distribute this software for any
.\" purpose with or without fee is hereby granted, provided that the above
.\" copyright notice and this permission notice appear in all copies.
.\"
.\" THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
.\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
.\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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.\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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.\"
.Dd $Mdocdate: October 29 2021 $
.Dt CRYPT_CHECKPASS 3
.Os
.Sh NAME
.Nm crypt_checkpass ,
.Nm crypt_newhash
.Nd password hashing
.Sh SYNOPSIS
.In pwd.h
.In unistd.h
.Ft int
.Fn crypt_checkpass "const char *password" "const char *hash"
.Ft int
.Fn crypt_newhash "const char *password" "const char *pref" "char *hash" "size_t hashsize"
.Sh DESCRIPTION
The
.Fn crypt_checkpass
function simplifies checking a user's password.
If both the
.Fa hash
and the
.Fa password
are the empty string, authentication
is a success.
Otherwise, the
.Fa password
is hashed and compared to the provided
.Fa hash .
If the
.Fa hash
is
.Dv NULL ,
authentication will always fail, but a default
amount of work is performed to simulate the hashing operation.
A successful match will return 0.
A failure will return \-1 and set
.Xr errno 2 .
.Pp
The
.Fn crypt_newhash
function simplifies the creation of new password hashes.
The provided
.Fa password
is randomly salted and hashed and stored in
.Fa hash .
The size of the available space is specified by
.Fa hashsize ,
which should be
.Dv _PASSWORD_LEN .
The
.Fa pref
argument identifies the preferred hashing algorithm and parameters.
Possible values are:
.Bl -tag -width Ds
.It Dq bcrypt,<rounds>
The bcrypt algorithm, where the value of rounds can be between 4 and 31 and
specifies the base 2 logarithm of the number of rounds.
If rounds is omitted or the special value
.Sq a ,
an appropriate number of rounds is automatically selected based on system
performance.
.El
.Sh RETURN VALUES
.Rv -std crypt_checkpass crypt_newhash
.Sh ERRORS
The
.Fn crypt_checkpass
function sets
.Va errno
to
.Er EACCES
when authentication fails.
.Pp
The
.Fn crypt_newhash
function sets
.Va errno
to
.Er EINVAL
if
.Fa pref
is unsupported or insufficient space is provided.
.Sh SEE ALSO
.Xr crypt 3 ,
.Xr login.conf 5 ,
.Xr passwd 5
.Sh HISTORY
The function
.Fn crypt_checkpass
first appeared in
.Ox 5.6 ,
and
.Fn crypt_newhash
in
.Ox 5.7 .
.Sh AUTHORS
.An Ted Unangst Aq Mt tedu@openbsd.org