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 variables 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 conjunction 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 conjunction 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 library, 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.