PAM_CONV(3)              BSD Library Functions Manual              PAM_CONV(3)

NAME
     pam_conv -- PAM conversation system

LIBRARY
     Pluggable Authentication Module Library (libpam, -lpam)

SYNOPSIS
     #include <security/pam_appl.h>

     struct pam_message {
             int      msg_style;
             char    *msg;
     };

     struct pam_response {
             char    *resp;
             int      resp_retcode;
     };

     struct pam_conv {
             int     (*conv)(int, const struct pam_message **,
                 struct pam_response **, void *);
             void    *appdata_ptr;
     };

DESCRIPTION
     The PAM library uses an application-defined callback to communicate with
     the user.  This callback is specified by the struct pam_conv passed to
     pam_start() at the start of the transaction.  It is also possible to set
     or change the conversation function at any point during a PAM transaction
     by changing the value of the PAM_CONV item.

     The conversation function's first argument specifies the number of mes-
     sages (up to PAM_NUM_MSG) to process.  The second argument is a pointer
     to an array of pointers to pam_message structures containing the actual
     messages.

     Each message can have one of four types, specified by the msg_style mem-
     ber of struct pam_message:

     PAM_PROMPT_ECHO_OFF
                         Display a prompt and accept the user's response with-
                         out echoing it to the terminal.  This is commonly
                         used for passwords.

     PAM_PROMPT_ECHO_ON  Display a prompt and accept the user's response,
                         echoing it to the terminal.  This is commonly used
                         for login names and one-time passphrases.

     PAM_ERROR_MSG       Display an error message.

     PAM_TEXT_INFO       Display an informational message.

     In each case, the prompt or message to display is pointed to by the msg
     member of struct pam_message.  It can be up to PAM_MAX_MSG_SIZE charac-
     ters long, including the terminating NUL.

     On success, the conversation function should allocate and fill a contigu-
     ous array of struct pam_response, one for each message that was passed
     in.  A pointer to the user's response to each message (or NULL in the
     case of informational or error messages) should be stored in the resp
     member of the corresponding struct pam_response.  Each response can be up
     to PAM_MAX_RESP_SIZE characters long, including the terminating NUL.

     The resp_retcode member of struct pam_response is unused and should be
     set to zero.

     The conversation function should store a pointer to this array in the
     location pointed to by its third argument.  It is the caller's responsi-
     bility to release both this array and the responses themselves, using
     free(3).  It is the conversation function's responsibility to ensure that
     it is legal to do so.

     The appdata_ptr member of struct pam_conv is passed unmodified to the
     conversation function as its fourth and final argument.

     On failure, the conversation function should release any resources it has
     allocated, and return one of the predefined PAM error codes.

RETURN VALUES
     The conversation function should return one of the following values:

     [PAM_BUF_ERR]       Memory buffer error.

     [PAM_CONV_ERR]      Conversation failure.

     [PAM_SUCCESS]       Success.

     [PAM_SYSTEM_ERR]    System error.

SEE ALSO
     openpam_nullconv(3), openpam_ttyconv(3), pam(3), pam_error(3),
     pam_get_item(3), pam_info(3), pam_prompt(3), pam_set_item(3),
     pam_start(3)

STANDARDS
     X/Open Single Sign-On Service (XSSO) - Pluggable Authentication Modules,
     June 1997.

AUTHORS
     The OpenPAM library and this manual page were developed for the FreeBSD
     Project by ThinkSec AS and Network Associates Laboratories, the Security
     Research Division of Network Associates, Inc. under DARPA/SPAWAR contract
     N66001-01-C-8035 (``CBOSS''), as part of the DARPA CHATS research pro-
     gram.

BSD                              June 16, 2005                             BSD