Establish / delete user credentials
#include <security/pam_appl.h>
int pam_setcred(pam_handle_t *pamh, int flags);
The pam_setcred function is used to establish, maintain and delete the credentials of a user. It should be called to set the credentials after a user has been authenticated and before a session is opened for the user (with pam_open_session(3)). The credentials should be deleted after the session has been closed (with pam_close_session(3)).
A credential is something that the user possesses. It is some property, such as a Kerberos ticket, or a supplementary group membership that make up the uniqueness of a given user. On a Linux system the user's UID and GID's are credentials too. However, it has been decided that these properties (along with the default supplementary groups of which the user is a member) are credentials that should be set directly by the application and not by PAM. Such credentials should be established, by the application, prior to a call to this function. For example, initgroups(2) (or equivalent) should have been performed.
Valid flags, any one of which, may be logically OR'd with PAM_SILENT, are:
PAM_ESTABLISH_CRED
Initialize the credentials for the user.
PAM_DELETE_CRED
Delete the user's credentials.
PAM_REINITIALIZE_CRED
Fully reinitialize the user's credentials.
PAM_REFRESH_CRED
Extend the lifetime of the existing credentials.
PAM_BUF_ERR
Memory buffer error.
PAM_CRED_ERR
Failed to set user credentials.
PAM_CRED_EXPIRED
User credentials are expired.
PAM_CRED_UNAVAIL
Failed to retrieve user credentials.
PAM_SUCCESS
Data was successful stored.
PAM_SYSTEM_ERR
A NULL pointer was submitted as PAM handle, the function was called by a module or another system error occured.
PAM_USER_UNKNOWN
User is not known to an authentication module.