/* $FreeBSD$ */


#ifdef USE_PAM
/*
 * the following code is stolen from imap-uw PAM authentication module and
 * login.c
 */
#define COPY_STRING(s) (s ? strdup(s) : NULL)

struct cred_t {
	const char *uname;		/* user name */
	const char *pass;		/* password */
};
typedef struct cred_t cred_t;

static int
auth_conv(int num_msg, const struct pam_message **msg,
	  struct pam_response **resp, void *appdata)
{
	int i;
	cred_t *cred = (cred_t *) appdata;
	struct pam_response *reply;

	reply = calloc(num_msg, sizeof *reply);
	if (reply == NULL)
		return PAM_BUF_ERR;

	for (i = 0; i < num_msg; i++) {
		switch (msg[i]->msg_style) {
		case PAM_PROMPT_ECHO_ON:	/* assume want user name */
			reply[i].resp_retcode = PAM_SUCCESS;
			reply[i].resp = COPY_STRING(cred->uname);
			/* PAM frees resp. */
			break;
		case PAM_PROMPT_ECHO_OFF:	/* assume want password */
			reply[i].resp_retcode = PAM_SUCCESS;
			reply[i].resp = COPY_STRING(cred->pass);
			/* PAM frees resp. */
			break;
		case PAM_TEXT_INFO:
		case PAM_ERROR_MSG:
			reply[i].resp_retcode = PAM_SUCCESS;
			reply[i].resp = NULL;
			break;
		default:			/* unknown message style */
			free(reply);
			return PAM_CONV_ERR;
		}
	}

	*resp = reply;
	return PAM_SUCCESS;
}

/*
 * Attempt to authenticate the user using PAM.  Returns 0 if the user is
 * authenticated, or 1 if not authenticated.  If some sort of PAM system
 * error occurs (e.g., the "/etc/pam.conf" file is missing) then this
 * function returns -1.  This can be used as an indication that we should
 * fall back to a different authentication mechanism.
 */
static int
auth_pam(struct passwd **ppw, const char *pass)
{
	pam_handle_t *pamh = NULL;
	const char *tmpl_user;
	const void *item;
	int rval;
	int e;
	cred_t auth_cred = { (*ppw)->pw_name, pass };
	struct pam_conv conv = { &auth_conv, &auth_cred };

	e = pam_start("ftpd", (*ppw)->pw_name, &conv, &pamh);
	if (e != PAM_SUCCESS) {
		syslog(LOG_ERR, "pam_start: %s", pam_strerror(pamh, e));
		return -1;
	}

	e = pam_set_item(pamh, PAM_RHOST, remotehost);
	if (e != PAM_SUCCESS) {
		syslog(LOG_ERR, "pam_set_item(PAM_RHOST): %s",
			pam_strerror(pamh, e));
		return -1;
	}

	e = pam_authenticate(pamh, 0);
	switch (e) {
	case PAM_SUCCESS:
		/*
		 * With PAM we support the concept of a "template"
		 * user.  The user enters a login name which is
		 * authenticated by PAM, usually via a remote service
		 * such as RADIUS or TACACS+.  If authentication
		 * succeeds, a different but related "template" name
		 * is used for setting the credentials, shell, and
		 * home directory.  The name the user enters need only
		 * exist on the remote authentication server, but the
		 * template name must be present in the local password
		 * database.
		 *
		 * This is supported by two various mechanisms in the
		 * individual modules.  However, from the application's
		 * point of view, the template user is always passed
		 * back as a changed value of the PAM_USER item.
		 */
		if ((e = pam_get_item(pamh, PAM_USER, &item)) ==
		    PAM_SUCCESS) {
			tmpl_user = (const char *) item;
			if (strcmp((*ppw)->pw_name, tmpl_user) != 0)
				*ppw = getpwnam(tmpl_user);
		} else
			syslog(LOG_ERR, "Couldn't get PAM_USER: %s",
			    pam_strerror(pamh, e));
		rval = 0;
		break;

	case PAM_AUTH_ERR:
	case PAM_USER_UNKNOWN:
	case PAM_MAXTRIES:
		rval = 1;
		break;

	default:
		syslog(LOG_ERR, "pam_authenticate: %s", pam_strerror(pamh, e));
		rval = -1;
		break;
	}

	if (rval == 0) {
		e = pam_acct_mgmt(pamh, 0);
		if (e == PAM_NEW_AUTHTOK_REQD) {
			e = pam_chauthtok(pamh, PAM_CHANGE_EXPIRED_AUTHTOK);
			if (e != PAM_SUCCESS) {
				syslog(LOG_ERR, "pam_chauthtok: %s",
				    pam_strerror(pamh, e));
				rval = 1;
			}
		} else if (e != PAM_SUCCESS) {
			rval = 1;
		}
	}

	if (rval != 0) {
		if ((e = pam_end(pamh, e)) != PAM_SUCCESS) {
			syslog(LOG_ERR, "pam_end: %s", pam_strerror(pamh, e));
		}
		pamh = NULL;
	}
	return rval;
}

#endif /* USE_PAM */