pam_get_item man page
pam_get_item — getting PAM informations
int pam_get_item(const pam_handle_t *pamh, int item_type, const void **item);
The pam_get_item function allows applications and PAM service modules to access and retrieve PAM informations of item_type. Upon successful return, item contains a pointer to the value of the corresponding item. Note, this is a pointer to the actual data and should not be free()'ed or over-written! The following values are supported for item_type:
The service name (which identifies that PAM stack that the PAM functions will use to authenticate the program).
The username of the entity under whose identity service will be given. That is, following authentication, PAM_USER identifies the local entity that gets to use the service. Note, this value can be mapped from something (eg., "anonymous") to something else (eg. "guest119") by any module in the PAM stack. As such an application should consult the value of PAM_USER after each call to a PAM function.
The string used when prompting for a user's name. The default value for this string is a localized version of "login: ".
The terminal name: prefixed by /dev/ if it is a device file; for graphical, X-based, applications the value for this item should be the $DISPLAY variable.
The requesting user name: local name for a locally requesting user or a remote user name for a remote requesting user.
Generally an application or module will attempt to supply the value that is most strongly authenticated (a local account before a remote one. The level of trust in this value is embodied in the actual authentication stack associated with the application, so it is ultimately at the discretion of the system administrator.
PAM_RUSER@PAM_RHOST should always identify the requesting user. In some cases, PAM_RUSER may be NULL. In such situations, it is unclear who the requesting entity is.
The requesting hostname (the hostname of the machine from which the PAM_RUSER entity is requesting service). That is PAM_RUSER@PAM_RHOST does identify the requesting user. In some applications, PAM_RHOST may be NULL. In such situations, it is unclear where the authentication request is originating from.
The authentication token (often a password). This token should be ignored by all module functions besides pam_sm_authenticate(3) and pam_sm_chauthtok(3). In the former function it is used to pass the most recent authentication token from one stacked module to another. In the latter function the token is used for another purpose. It contains the currently active authentication token.
The old authentication token. This token should be ignored by all module functions except pam_sm_chauthtok(3).
The pam_conv structure. See pam_conv(3).
The following additional items are specific to Linux-PAM and should not be used in portable applications:
A function pointer to redirect centrally managed failure delays. See pam_fail_delay(3).
The name of the X display. For graphical, X-based applications the value for this item should be the $DISPLAY variable. This value may be used independently of PAM_TTY for passing the name of the display.
A pointer to a structure containing the X authentication data required to make a connection to the display specified by PAM_XDISPLAY, if such information is necessary. See pam_xauth_data(3).
The default action is for the module to use the following prompts when requesting passwords: "New UNIX password: " and "Retype UNIX password: ". The example word UNIX can be replaced with this item, by default it is empty. This item is used by pam_get_authtok(3).
If a service module wishes to obtain the name of the user, it should not use this function, but instead perform a call to pam_get_user(3).
Only a service module is privileged to read the authentication tokens, PAM_AUTHTOK and PAM_OLDAUTHTOK.
The application attempted to set an undefined or inaccessible item.
Memory buffer error.
The value of item was NULL.
Data was successful updated.
The pam_handle_t passed as first argument was invalid.
access.conf(5), pam(3), pam_authenticate(3), pam_chauthtok(3), pam_conv(3), pam_end(3), pam_fail_delay(3), pam_get_user(3), pam_set_item(3), pam_start(3), pam_xauth_data(3).