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

     pam_conv -- PAM conversation system

     Pluggable Authentication Module Library (libpam, -lpam)

     #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;

     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_MAX_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:

			 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 lo-
     cation pointed to by its third argument.  It is the caller's responsibil-
     ity 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.

     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.

     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),

     June 1997.

     The OpenPAM library and this manual page were developed for the FreeBSD
     Project by	ThinkSec AS and	Network	Associates Laboratories, the Security

     The OpenPAM library is maintained by Dag-Erling Smorgrav <>.

BSD			      September	12, 2014			   BSD


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