man > crypt_checksalt(3)

CRYPT_CHECKSALT(3)                     Library Functions Manual                   CRYPT_CHECKSALT(3)

NAME
       crypt_checksalt — validate a crypt setting string

LIBRARY
       Crypt Library (libcrypt, -lcrypt)

SYNOPSIS
       #include <crypt.h>

       int
       crypt_checksalt(const char *setting);

DESCRIPTION
       crypt_checksalt  checks  the  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 login(1) to determine whether the user's passphrase should be re-
       hashed using the currently preferred hashing method.

RETURN VALUES
       The return value is 0 if there is nothing wrong with this setting.  Otherwise, it is  one  of
       the following constants:

       CRYPT_SALT_OK
             setting is a fully correct setting string.  This constant is guaranteed to equal 0.

       CRYPT_SALT_INVALID
             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.

       CRYPT_SALT_METHOD_DISABLED (Not implemented, yet)
             setting  specifies  a hashing method that is no longer allowed to be used at all; crypt
             will fail if passed this setting.  Manual intervention will be required  to  reactivate
             the user's account.

       CRYPT_SALT_METHOD_LEGACY
             setting  specifies  a hashing method that is no longer considered strong enough for use
             with new passphrases.  crypt will still authenticate a passphrase against this setting,
             but if authentication succeeds, the passphrase should be re-hashed using the  currently
             preferred method.

       CRYPT_SALT_TOO_CHEAP (Not implemented, yet)
             setting  specifies  cost  parameters  that  are  considered  too cheap for use with new
             passphrases.  crypt will still authenticate a passphrase against this setting,  but  if
             authentication  succeeds,  the  passphrase should be re-hashed using the currently pre‐
             ferred method.

FEATURE TEST MACROS
       <crypt.h> will define the macro CRYPT_CHECKSALT_AVAILABLE if crypt_checksalt is available  in
       the current version of libxcrypt.

BUGS
       Since  full configurability is not yet implemented, the current implementation will only ever
       return CRYPT_SALT_OK (0) or CRYPT_SALT_INVALID when invoked.

PORTABILITY NOTES
       The function crypt_checksalt is not part of any standard.  It was added to libxcrypt in  ver‐
       sion 4.3.0.

ATTRIBUTES
       For an explanation of the terms used in this section, see attributes(7).
       ┌─────────────────┬───────────────┬─────────┐
       │ Interface       │ Attribute     │ Value   │
       ├─────────────────┼───────────────┼─────────┤
       │ crypt_checksalt │ Thread safety │ MT-Safe │
       └─────────────────┴───────────────┴─────────┘


SEE ALSO
       crypt(3), crypt_gensalt(3), crypt(5)

libxcrypt                                 November 8, 2018                        CRYPT_CHECKSALT(3)