pam_start, pam_end - PAM authentication transaction functions


cc [ flag ... ] file ... -lpam [ library ... ]
#include <security/pam_appl.h>

int pam_start(const char *service, const char *user,
const struct pam_conv *pam_conv, pam_handle_t **pamh);

int pam_end(pam_handle_t *pamh, int status);


The pam_start() function is called to initiate an authentication
transaction. It takes as arguments the name of the current service,
service, the name of the user to be authenticated, user, the address of
the conversation structure, pam_conv, and the address of a variable to be
assigned the authentication handle pamh. Upon successful completion,
pamh refers to a PAM handle for use with subsequent calls to the
authentication library.

The pam_conv structure contains the address of the conversation function
provided by the application. The underlying PAM service module invokes
this function to output information to and retrieve input from the user.
The pam_conv structure has the following entries:

struct pam_conv {
int (*conv)(); /* Conversation function */
void *appdata_ptr; /* Application data */

int conv(int num_msg, const struct pam_message **msg,
struct pam_response **resp, void *appdata_ptr);

The conv() function is called by a service module to hold a PAM
conversation with the application or user. For window applications, the
application can create a new pop-up window to be used by the interaction.

The num_msg parameter is the number of messages associated with the
call. The parameter msg is a pointer to an array of length num_msg of the
pam_message structure.

The pam_message structure is used to pass prompt, error message, or any
text information from the authentication service to the application or
user. It is the responsibility of the PAM service modules to localize the
messages. The memory used by pam_message has to be allocated and freed by
the PAM modules. The pam_message structure has the following entries:

struct pam_message{
int msg_style;
char *msg;

The message style, msg_style, can be set to one of the following values:

Prompt user, disabling echoing of response.

Prompt user, enabling echoing of response.

Print error message.

Print general text information.

The maximum size of the message and the response string is
PAM_MAX_MSG_SIZE as defined in <security/pam.appl.h>.

The structure pam_response is used by the authentication service to get
the user's response back from the application or user. The storage used
by pam_response has to be allocated by the application and freed by the
PAM modules. The pam_response structure has the following entries:

struct pam_response{
char *resp;
int resp_retcode; /* currently not used, */
/* should be set to 0 */

It is the responsibility of the conversation function to strip off
styles, and to add NEWLINE characters (if appropriate) for PAM_ERROR_MSG
and PAM_TEXT_INFO message styles.

The appdata_ptr argument is an application data pointer which is passed
by the application to the PAM service modules. Since the PAM modules
pass it back through the conversation function, the applications can use
this pointer to point to any application-specific data.

The pam_end() function is called to terminate the authentication
transaction identified by pamh and to free any storage area allocated by
the authentication module. The argument, status, is passed to the
cleanup(|) function stored within the pam handle, and is used to
determine what module-specific state must be purged. A cleanup function
is attached to the handle by the underlying PAM modules through a call to
pam_set_data(3PAM) to free module-specific data.

Refer to Solaris Security for Developers Guide for information about
providing authentication, account management, session management, and
password management through PAM modules.


Refer to the RETURN VALUES section on pam(3PAM).


See attributes(5) for description of the following attributes:

|Interface Stability | Stable |
|MT-Level | MT-Safe with exceptions |


libpam(3LIB), pam(3PAM), pam_acct_mgmt(3PAM), pam_authenticate(3PAM),
pam_chauthtok(3PAM), pam_open_session(3PAM), pam_setcred(3PAM),
pam_set_data(3PAM), pam_strerror(3PAM), attributes(5)

Solaris Security for Developers Guide


The interfaces in libpam are MT-Safe only if each thread within the
multithreaded application uses its own PAM handle.

February 22, 2005 PAM_START(3PAM)