pam_sm(3)
PAM - PAM Service Module APIs
As shipped in IRIX 6.5.30. Added in IRIX 6.5.19.
NAME PAM - PAM Service Module APIs SYNOPSIS #include <security/pam_appl.h> #include <security/pam_modules.h> cc [ flag ... ] file ... -lpam [ library ... ] DESCRIPTION PAM gives system administrators the flexibility of choosing any authentica- tion service available on the system to perform authentication. The frame- work also allows new authentication service modules to be plugged in and made available without modifying the applications. The PAM framework, libpam, consists of an interface library and multiple authentication service modules. The PAM interface library is the layer im- plementing the Application Programming Interface (API). The authentication service modules are a set of dynamically loadable objects invoked by the PAM API to provide a particular type of user authentication. This manual page gives an overview of the PAM APIs for the service modules. Interface Overview The PAM service module interface consists of functions which can be grouped into four categories. The names for all the authentication library func- tions start with pam_sm. The first category contains functions to authenticate an individual user (pam_sm_authenticate(3)) and to set the credentials of the user (pam_sm_setcred(3)). These back-end functions implement the functionality of pam_authenticate(3) and pam_setcred(3) respectively. The second category contains functions to do account management (pam_sm_acct_mgmt(3)). This includes checking for password aging and ac- cess-hour restrictions. This back-end function implements the functional- ity of pam_acct_mgmt(3). The third category contains functions to perform session management (pam_sm_open_session(3) and pam_sm_close_session(3)) after access to the system has been granted. These back-end functions implement the function- ality of pam_open_session(3) and pam_close_session(3), respectively. The fourth category consists of functions to change authentication tokens (pam_sm_chauthtok(3)) and to manipulate authentication token attributes (pam_sm_set_authtokattr(3)) and (pam_sm_get_authtokattr(3)). These back- end functions implement the functionality of pam_chauthtok(3), pam_set_au- thtokattr(3), and pam_get_authtokattr(3), respectively. The only difference between the pam_*() interfaces and their corresponding pam_sm_*() interfaces is that all the pam_sm_*() interfaces require extra parameters to pass service specific options to the shared modules. They are otherwise identical. Stateful Interface A sequence of calls sharing a common set of state information is referred to as an authentication transaction. An authentication transaction begins with a call to pam_start(). pam_start() allocates space, performs various initialization activities, and assigns an authentication handle to be used for subsequent calls to the library. Note that the service modules do not get called or initialized when pam_start() is called. The modules are loaded and the symbols resolved upon first use of that function. The PAM handle keeps certain information about the transaction that can be accessed through the pam_get_item() API. Though the modules can also use pam_set_item() to change any of the item information, it is recommended that nothing be changed except PAM_AUTHTOK and PAM_OLDAUTHTOK. If the modules want to store any module specific state information then they can use the pam_set_data(3) function to store that information with the PAM handle. The data should be stored with a name which is unique across all modules and module types. For example, SUNW_PAM_DCE_AUTH_userid can be used as a name by the DCE module to store information about the state of user's authentication. Some modules use this technique to share data across two different module types. The module can also store a cleanup function associated with the data. The PAM framework calls this cleanup function, when the application calls pam_end() to close the transaction. Interaction with the User The PAM service modules do not communicate directly with the user; instead they rely on the application to perform all such interactions. The appli- cation passes a pointer to the function, conv(), along with any associated application data pointers, through the pam_conv structure when it initiates an authentication transaction (via a call to pam_start()). The service module will then use the function (conv()) to prompt the user for data, output error messages, and display text information. Refer to pam_start(3) for more information. CONVENTIONS Though the PAM framework enforces no rules about the module's names, loca- tion, options and such, there are certain conventions that all module providers are expected to follow. By convention, the modules should be located in the /usr/lib/security di- rectory. Additional modules may be located in /opt/<pkg>/lib. By convention, the modules are named pam_<service_name>_<module_type>.so.1. If the given module implements more than one module type (for example, pam_unix.so.1 module), then the module_type suffix should be dropped. For every such module, there should be a corresponding manual page in sec- tion 5 which should describe the module_type it supports, the functionality of the module, along with the options it supports. The dependencies should be clearly identified to the system administrator. For example, it should be made clear whether this module is a stand-alone module or depends upon the presence of some other module. One should also specify whether this module should come before or after some other module in the stack. Though not required, it is recommended that the modules support the follow- ing options: debug Syslog debugging information at LOG_DEBUG level. Be careful as to not log any sensitive information such as passwords. nowarn turn off warning messages such as "password is about to expire" In addition, it is recommended that the auth and the password module sup- port the following options: use_first_pass Instead of prompting the user for the password, use the user's initial password (entered when the user was authenticated to the first authentication module in the stack) for authentication. If the passwords do not match, or if no password has been entered, re- turn failure and do not prompt the user for a pass- word. Support for this scheme allows the user to type only one password for multiple schemes. try_first_pass Instead of prompting the user for the password, use the user's initial password (entered when the user was authenticated to the first authentication module in the stack) for authentication. If the passwords do not match, or if no password has been entered, prompt the user for a password after identifying which type of password (ie. UNIX, DCE, etc.) is being requested. Support for this scheme allows the user to try to use only one password for multiple schemes, and type multiple passwords only if necessary. If an unsupported option is passed to the modules, it should syslog the er- ror at LOG_ERR level. The permission bits on the service module should be set such that it is not writable by either "group" or "other". The PAM framework will not load the module if the above permission rules are not followed. ERROR LOGGING If there are any errors, the modules should log them using syslog(3) at the LOG_ERR level. RETURN VALUES The PAM service module functions may return any of the PAM error numbers specified in the specific man pages. It can also return a PAM_IGNORE error number to mean that the PAM framework should ignore this module regardless of whether it is required, optional or sufficient. This error number is normally returned when the module does not want to deal with the given user at all. SEE ALSO pam(3), pam_start(3), pam_set_item(3), pam_authenticate(3), pam_open_ses- sion(3), pam_setcred(3), pam_chauthtok(3), pam_strerror(3), pam_sm_authen- ticate(3), pam_sm_open_session(3), pam_sm_setcred(3), pam_sm_chauthtok(3), pam.conf(4)