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.\" Written by Zack Weinberg <zackw at panix.com> in 2018.
.\"
.\" To the extent possible under law, the authors have waived
.\" all copyright and related or neighboring rights to this work.
.\" See https://creativecommons.org/publicdomain/zero/1.0/ for further
.\" details.
.\"
.Dd November 8, 2018
.Dt CRYPT_CHECKSALT 3
.Os "libxcrypt"
.Sh NAME
.Nm crypt_checksalt
.Nd validate a crypt setting string
.Sh LIBRARY
.Lb libcrypt
.Sh SYNOPSIS
.In crypt.h
.Ft int
.Fo crypt_checksalt
.Fa "const char *setting"
.Fc
.Sh DESCRIPTION
.Nm
checks the
.Ar setting
string against the system configuration
and reports whether the hashing method and parameters it specifies
are acceptable.
It is intended to be used by programs
such as
.Xr login 1
to determine whether the user's passphrase should be re-hashed
using the currently preferred hashing method.
.Sh RETURN VALUES
The return value is 0 if there is nothing wrong with this setting.
Otherwise, it is one of the following constants:
.Bl -tag -width 4n
.It Dv CRYPT_SALT_OK
.Ar setting
is a fully correct setting string.
This constant is guaranteed to equal 0.
.It Dv CRYPT_SALT_INVALID
.Ar setting
is not a valid setting string; either it specifies a hashing method
that is not known to this version of libxcrypt,
or it specifies invalid parameters for the method.
.It Dv CRYPT_SALT_METHOD_DISABLED (Not implemented, yet)
.Ar setting
specifies a hashing method that is no longer allowed to be used at all;
.Nm crypt
will fail if passed this
.Ar setting .
Manual intervention will be required to reactivate the user's account.
.It Dv CRYPT_SALT_METHOD_LEGACY
.Ar setting
specifies a hashing method that is no longer considered strong enough
for use with new passphrases.
.Nm crypt
will still authenticate a passphrase against this setting,
but if authentication succeeds,
the passphrase should be re-hashed using the currently preferred method.
.It Dv CRYPT_SALT_TOO_CHEAP (Not implemented, yet)
.Ar setting
specifies cost parameters that are considered too cheap for use with
new passphrases.
.Nm crypt
will still authenticate a passphrase against this setting,
but if authentication succeeds,
the passphrase should be re-hashed using the currently preferred method.
.El
.Sh FEATURE TEST MACROS
.In crypt.h
will define the macro
.Dv CRYPT_CHECKSALT_AVAILABLE
if
.Nm
is available in the current version of libxcrypt.
.Sh BUGS
Since full configurability is not yet implemented, the current
implementation will only ever return
.Nm CRYPT_SALT_OK (0)
or
.Nm CRYPT_SALT_INVALID
when invoked.
.Sh PORTABILITY NOTES
The function
.Nm
is not part of any standard.
It was added to libxcrypt in version 4.3.0.
.Sh ATTRIBUTES
For an explanation of the terms used in this section, see
.Xr attributes 7 .
.TS
allbox;
lb lb lb
l l l.
Interface Attribute Value
T{
.Nm
T} Thread safety MT-Safe
.TE
.sp
.Sh SEE ALSO
.Xr crypt 3 ,
.Xr crypt_gensalt 3 ,
.Xr crypt 5
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