source: openpam/trunk/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: pam_get_authtok.c 938 2017-04-30 21:34:42Z des $
 */

#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
 */