Pam service function to alter credentials
#define PAM_SM_AUTH
#include <security/pam_modules.h>
PAM_EXTERN int pam_sm_setcred(pam_handle_t *pamh, int flags, int argc, const char **argv);
The pam_sm_setcred function is the service module's implementation of the pam_setcred(3) interface.
This function performs the task of altering the credentials of the user with respect to the corresponding authorization scheme. Generally, an authentication module may have access to more information about a user than their authentication token. This function is used to make such information available to the application. It should only be called after the user has been authenticated but before a session has been established.
Valid flags, which may be logically OR'd with PAM_SILENT, are:
PAM_SILENT
Do not emit any messages.
PAM_ESTABLISH_CRED
Initialize the credentials for the user.
PAM_DELETE_CRED
Delete the credentials associated with the authentication service.
PAM_REINITIALIZE_CRED
Reinitialize the user credentials.
PAM_REFRESH_CRED
Extend the lifetime of the user credentials.
The way the auth stack is navigated in order to evaluate the pam_setcred() function call, independent of the pam_sm_setcred() return codes, is exactly the same way that it was navigated when evaluating the pam_authenticate() library call. Typically, if a stack entry was ignored in evaluating pam_authenticate(), it will be ignored when libpam evaluates the pam_setcred() function call. Otherwise, the return codes from each module specific pam_sm_setcred() call are treated as required.
PAM_CRED_UNAVAIL
This module cannot retrieve the user's credentials.
PAM_CRED_EXPIRED
The user's credentials have expired.
PAM_CRED_ERR
This module was unable to set the credentials of the user.
PAM_SUCCESS
The user credential was successfully set.
PAM_USER_UNKNOWN
The user is not known to this authentication module.
These, non-PAM_SUCCESS, return values will typically lead to the credential stack failing. The first such error will dominate in the return value of pam_setcred().