---
name: "pam_sm_chauthtok"
section: "3"
platform: "linux"
package: "pam"
version: "1.7.3-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux", "freebsd", "macos"]
url: "https://new.carta.tech/pam_sm_chauthtok"
---

# pam\_sm\_chauthtok(3)

PAM service function for authentication token management

## NAME

pam\_sm\_chauthtok - PAM service function for authentication token management

## SYNOPSIS

```
#include <security/pam_modules.h>
```

**int pam\_sm\_chauthtok(pam\_handle\_t \****pamh***, int** *flags***, int** *argc***, const char \*\****argv***);**

## DESCRIPTION

The **pam\_sm\_chauthtok** function is the service module's implementation of the [**pam\_chauthtok**(3)](/pam_chauthtok/3.md) interface.

This function is used to (re-)set the authentication token of the user.

Valid flags, which may be logically OR'd with *PAM\_SILENT*, are:

PAM\_SILENT

Do not emit any messages.

PAM\_CHANGE\_EXPIRED\_AUTHTOK

This argument indicates to the module that the user's authentication token (password) should only be changed if it has expired. This flag is optional and *must* be combined with one of the following two flags. Note, however, the following two options are *mutually exclusive*.

PAM\_PRELIM\_CHECK

This indicates that the modules are being probed as to their ready status for altering the user's authentication token. If the module requires access to another system over some network it should attempt to verify it can connect to this system on receiving this flag. If a module cannot establish it is ready to update the user's authentication token it should return **PAM\_TRY\_AGAIN**, this information will be passed back to the application.

If the control value *sufficient* is used in the password stack, the *PAM\_PRELIM\_CHECK* section of the modules following that control value is not always executed.

PAM\_UPDATE\_AUTHTOK

This informs the module that this is the call it should change the authorization tokens. If the flag is logically OR'd with **PAM\_CHANGE\_EXPIRED\_AUTHTOK**, the token is only changed if it has actually expired.

The PAM library calls this function twice in succession. The first time with **PAM\_PRELIM\_CHECK** and then, if the module does not return **PAM\_TRY\_AGAIN**, subsequently with **PAM\_UPDATE\_AUTHTOK**. It is only on the second call that the authorization token is (possibly) changed.

## RETURN VALUES

PAM\_AUTHTOK\_ERR

The module was unable to obtain the new authentication token.

PAM\_AUTHTOK\_RECOVERY\_ERR

The module was unable to obtain the old authentication token.

PAM\_AUTHTOK\_LOCK\_BUSY

Cannot change the authentication token since it is currently locked.

PAM\_AUTHTOK\_DISABLE\_AGING

Authentication token aging has been disabled.

PAM\_PERM\_DENIED

Permission denied.

PAM\_TRY\_AGAIN

Preliminary check was unsuccessful. Signals an immediate return to the application is desired.

PAM\_SUCCESS

The authentication token was successfully updated.

PAM\_USER\_UNKNOWN

User unknown to password service.

## SEE ALSO

[**pam**(3)](/pam/3.md), [**pam\_chauthtok**(3)](/pam_chauthtok/3.md), [**pam\_sm\_chauthtok**(3)](/pam_sm_chauthtok/3.md), [**pam\_strerror**(3)](/pam_strerror/3.md), [**PAM**(8)](/PAM/8.md)