---
name: "crypt_checksalt"
section: "3"
platform: "linux"
package: "libxcrypt"
version: "4.5.2-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/crypt_checksalt"
---

# crypt\_checksalt(3)

validate a crypt setting string

## NAME

**crypt\_checksalt** – validate a crypt setting string

## LIBRARY

library “libcrypt”

## 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)](/login/1.md) 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 preferred 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 version 4.3.0.

## ATTRIBUTES

For an explanation of the terms used in this section, see [attributes(7)](/attributes/7.md).

| | | |
| --- | --- | --- |
| **Interface** | **Attribute** | **Value** |
|  | Thread safety | MT-Safe |

## SEE ALSO

[crypt(3)](/crypt/3.md), [crypt\_gensalt(3)](/crypt_gensalt/3.md), [crypt(5)](/crypt/5.md)