5.1. Functions supplied

5.1.1. Text based conversation function

#include <security/pam_misc.h>
void misc_conv(num_msg,  
 msgm,  
 response,  
 appdata_ptr); 
int  num_msg;
const struct pam_message ** msgm;
struct pam_response ** response;
void * appdata_ptr;

5.1.1.1. DESCRIPTION

The misc_conv function is part of libpam_misc and not of the standard libpam library. This function will prompt the user with the appropriate comments and obtain the appropriate inputs as directed by authentication modules.

In addition to simply slotting into the appropriate pam_conv(3), this function provides some time-out facilities. The function exports five variables that can be used by an application programmer to limit the amount of time this conversation function will spend waiting for the user to type something. The five variabls are as follows:

time_t pam_misc_conv_warn_time;

This variable contains the time (as returned by time(2)) that the user should be first warned that the clock is ticking. By default it has the value 0, which indicates that no such warning will be given. The application may set its value to sometime in the future, but this should be done prior to passing control to the Linux-PAM library.

const char *pam_misc_conv_warn_line;

Used in conjuction with pam_misc_conv_warn_time, this variable is a pointer to the string that will be displayed when it becomes time to warn the user that the timeout is approaching. Its default value is a translated version of “...Time is running out...”, but this can be changed by the application prior to passing control to Linux-PAM.

time_t pam_misc_conv_die_time;

This variable contains the time (as returned by time(2)) that the will time out. By default it has the value 0, which indicates that the conversation function will not timeout. The application may set its value to sometime in the future, but this should be done prior to passing control to the Linux-PAM library.

const char *pam_misc_conv_die_line;

Used in conjuction with pam_misc_conv_die_time, this variable is a pointer to the string that will be displayed when the conversation times out. Its default value is a translated version of “...Sorry, your time is up!”, but this can be changed by the application prior to passing control to Linux-PAM.

int pam_misc_conv_died;

Following a return from the Linux-PAM libraray, the value of this variable indicates whether the conversation has timed out. A value of 1 indicates the time-out occurred.

The following two function pointers are available for supporting binary prompts in the conversation function. They are optimized for the current incarnation of the libpamc library and are subject to change.

int (*pam_binary_handler_fn)(void *appdata, pamc_bp_t *prompt_p);

This function pointer is initialized to NULL but can be filled with a function that provides machine-machine (hidden) message exchange. It is intended for use with hidden authentication protocols such as RSA or Diffie-Hellman key exchanges. (This is still under development.)

int (*pam_binary_handler_free)(void *appdata, pamc_bp_t *delete_me);

This function pointer is initialized to PAM_BP_RENEW(delete_me, 0, 0), but can be redefined as desired by the application.

5.1.2. Transcribing an environment to that of PAM

#include <security/pam_misc.h>
int pam_misc_paste_env(pamh,  
 user); 
pam_handle_t * pamh;
const char * const * user;

5.1.2.1. DESCRIPTION

This function takes the supplied list of environment pointers and uploads its contents to the PAM environment. Success is indicated by PAM_SUCCESS.

5.1.3. Liberating a locally saved environment

#include <security/pam_misc.h>
int pam_misc_drop_env(env); 
char ** env;

5.1.3.1. DESCRIPTION

This function is defined to complement the pam_getenvlist(3) function. It liberates the memory associated with env, overwriting with 0 all memory before free()ing it.

5.1.4. BSD like PAM environment variable setting

#include <security/pam_misc.h>
int pam_misc_setenv(pamh,  
 name,  
 value,  
 readonly); 
pam_handle_t * pamh;
const char * name;
const char * value;
int readonly;

5.1.4.1. DESCRIPTION

This function performs a task equivalent to pam_putenv(3), its syntax is, however, more like the BSD style function; setenv(). The name and value are concatenated with an '=' to form a name=value and passed to pam_putenv(). If, however, the PAM variable is already set, the replacement will only be applied if the last argument, readonly, is zero.