OpenPAM/lib/libpam/pam_get_authtok.c

/*-
 * Copyright (c) 2002-2003 Networks Associates Technology, Inc.
 * Copyright (c) 2004-2017 Dag-Erling Smørgrav
 * All rights reserved.
 *
 * This software was 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 program.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote
 *    products derived from this software without specific prior written
 *    permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 * $OpenPAM$
 */

#ifdef HAVE_CONFIG_H
# include "config.h"
#endif

#include <sys/param.h>

#include <stdlib.h>
#include <string.h>

#include <security/pam_appl.h>
#include <security/openpam.h>

#include "openpam_impl.h"
#include "openpam_strlset.h"

static const char authtok_prompt[] = "Password:";
static const char authtok_prompt_remote[] = "Password for %u@%h:";
static const char oldauthtok_prompt[] = "Old Password:";
static const char newauthtok_prompt[] = "New Password:";

/*
 * OpenPAM extension
 *
 * Retrieve authentication token
 */

int
pam_get_authtok(pam_handle_t *pamh,
	int item,
	const char **authtok,
	const char *prompt)
{
	char prompt_buf[1024];
	size_t prompt_size;
	const void *oldauthtok, *prevauthtok, *promptp;
	const char *prompt_option, *default_prompt;
	const void *lhost, *rhost;
	char *resp, *resp2;
	int pitem, r, style, twice;

	ENTER();
	*authtok = NULL;
	twice = 0;
	switch (item) {
	case PAM_AUTHTOK:
		pitem = PAM_AUTHTOK_PROMPT;
		prompt_option = "authtok_prompt";
		default_prompt = authtok_prompt;
		r = pam_get_item(pamh, PAM_RHOST, &rhost);
		if (r == PAM_SUCCESS && rhost != NULL) {
			r = pam_get_item(pamh, PAM_HOST, &lhost);
			if (r == PAM_SUCCESS && lhost != NULL) {
				if (strcmp(rhost, lhost) != 0)
					default_prompt = authtok_prompt_remote;
			}
		}
		r = pam_get_item(pamh, PAM_OLDAUTHTOK, &oldauthtok);
		if (r == PAM_SUCCESS && oldauthtok != NULL) {
			default_prompt = newauthtok_prompt;
			twice = 1;
		}
		break;
	case PAM_OLDAUTHTOK:
		pitem = PAM_OLDAUTHTOK_PROMPT;
		prompt_option = "oldauthtok_prompt";
		default_prompt = oldauthtok_prompt;
		twice = 0;
		break;
	default:
		RETURNC(PAM_BAD_CONSTANT);
	}
	if (openpam_get_option(pamh, "try_first_pass") ||
	    openpam_get_option(pamh, "use_first_pass")) {
		r = pam_get_item(pamh, item, &prevauthtok);
		if (r == PAM_SUCCESS && prevauthtok != NULL) {
			*authtok = prevauthtok;
			RETURNC(PAM_SUCCESS);
		} else if (openpam_get_option(pamh, "use_first_pass")) {
			RETURNC(r == PAM_SUCCESS ? PAM_AUTH_ERR : r);
		}
	}
	/* pam policy overrides the module's choice */
	if ((promptp = openpam_get_option(pamh, prompt_option)) != NULL)
		prompt = promptp;
	/* no prompt provided, see if there is one tucked away somewhere */
	if (prompt == NULL) {
		r = pam_get_item(pamh, pitem, &promptp);
		if (r == PAM_SUCCESS && promptp != NULL)
			prompt = promptp;
	}
	/* fall back to hardcoded default */
	if (prompt == NULL)
		prompt = default_prompt;
	/* expand */
	prompt_size = sizeof prompt_buf;
	r = openpam_subst(pamh, prompt_buf, &prompt_size, prompt);
	if (r == PAM_SUCCESS && prompt_size <= sizeof prompt_buf)
		prompt = prompt_buf;
	style = openpam_get_option(pamh, "echo_pass") ?
	    PAM_PROMPT_ECHO_ON : PAM_PROMPT_ECHO_OFF;
	r = pam_prompt(pamh, style, &resp, "%s", prompt);
	if (r != PAM_SUCCESS)
		RETURNC(r);
	if (twice) {
		r = pam_prompt(pamh, style, &resp2, "Retype %s", prompt);
		if (r != PAM_SUCCESS) {
			strlset(resp, 0, PAM_MAX_RESP_SIZE);
			FREE(resp);
			RETURNC(r);
		}
		if (strcmp(resp, resp2) != 0) {
			strlset(resp, 0, PAM_MAX_RESP_SIZE);
			FREE(resp);
		}
		strlset(resp2, 0, PAM_MAX_RESP_SIZE);
		FREE(resp2);
	}
	if (resp == NULL)
		RETURNC(PAM_TRY_AGAIN);
	r = pam_set_item(pamh, item, resp);
	strlset(resp, 0, PAM_MAX_RESP_SIZE);
	FREE(resp);
	if (r != PAM_SUCCESS)
		RETURNC(r);
	r = pam_get_item(pamh, item, (const void **)authtok);
	RETURNC(r);
}

/*
 * Error codes:
 *
 *	=pam_get_item
 *	=pam_prompt
 *	=pam_set_item
 *	!PAM_SYMBOL_ERR
 *	PAM_BAD_CONSTANT
 *	PAM_TRY_AGAIN
 */

/**
 * The =pam_get_authtok function either prompts the user for an
 * authentication token or retrieves a cached authentication token,
 * depending on circumstances.
 * Either way, a pointer to the authentication token is stored in the
 * location pointed to by the =authtok argument, and the corresponding PAM
 * item is updated.
 *
 * The =item argument must have one of the following values:
 *
 *	=PAM_AUTHTOK:
 *		Returns the current authentication token, or the new token
 *		when changing authentication tokens.
 *	=PAM_OLDAUTHTOK:
 *		Returns the previous authentication token when changing
 *		authentication tokens.
 *
 * The =prompt argument specifies a prompt to use if no token is cached.
 * If it is =NULL, the =PAM_AUTHTOK_PROMPT or =PAM_OLDAUTHTOK_PROMPT item,
 * as appropriate, will be used.
 * If that item is also =NULL, a hardcoded default prompt will be used.
 * Additionally, when =pam_get_authtok is called from a service module,
 * the prompt may be affected by module options as described below.
 * The prompt is then expanded using =openpam_subst before it is passed to
 * the conversation function.
 *
 * If =item is set to =PAM_AUTHTOK and there is a non-null =PAM_OLDAUTHTOK
 * item, =pam_get_authtok will ask the user to confirm the new token by
 * retyping it.
 * If there is a mismatch, =pam_get_authtok will return =PAM_TRY_AGAIN.
 *
 * MODULE OPTIONS
 *
 * When called by a service module, =pam_get_authtok will recognize the
 * following module options:
 *
 *	;authtok_prompt:
 *		Prompt to use when =item is set to =PAM_AUTHTOK.
 *		This option overrides both the =prompt argument and the
 *		=PAM_AUTHTOK_PROMPT item.
 *	;echo_pass:
 *		If the application's conversation function allows it, this
 *		lets the user see what they are typing.
 *		This should only be used for non-reusable authentication
 *		tokens.
 *	;oldauthtok_prompt:
 *		Prompt to use when =item is set to =PAM_OLDAUTHTOK.
 *		This option overrides both the =prompt argument and the
 *		=PAM_OLDAUTHTOK_PROMPT item.
 *	;try_first_pass:
 *		If the requested item is non-null, return it without
 *		prompting the user.
 *		Typically, the service module will verify the token, and
 *		if it does not match, clear the item before calling
 *		=pam_get_authtok a second time.
 *	;use_first_pass:
 *		Do not prompt the user at all; just return the cached
 *		value, or =PAM_AUTH_ERR if there is none.
 *
 * >pam_conv
 * >pam_get_item
 * >pam_get_user
 * >openpam_get_option
 * >openpam_subst
 */