331 lines
9.0 KiB
C
331 lines
9.0 KiB
C
/*
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* SPDX-License-Identifier: ISC
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*
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* Copyright (c) 1993-1996,1998-2005, 2007-2018
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* Todd C. Miller <Todd.Miller@sudo.ws>
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*
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* Permission to use, copy, modify, and distribute this software for any
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* purpose with or without fee is hereby granted, provided that the above
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* copyright notice and this permission notice appear in all copies.
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*
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* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
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* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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*
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* Sponsored in part by the Defense Advanced Research Projects
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* Agency (DARPA) and Air Force Research Laboratory, Air Force
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* Materiel Command, USAF, under agreement number F39502-99-1-0512.
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*/
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/*
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* This is an open source non-commercial project. Dear PVS-Studio, please check it.
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* PVS-Studio Static Code Analyzer for C, C++ and C#: http://www.viva64.com
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*/
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#include <config.h>
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#include <sys/types.h>
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#include <stdio.h>
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#include <stdlib.h>
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#ifdef HAVE_STRING_H
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# include <string.h>
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#endif /* HAVE_STRING_H */
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#ifdef HAVE_STRINGS_H
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# include <strings.h>
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#endif /* HAVE_STRINGS_H */
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#include <unistd.h>
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#include <time.h>
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#include <errno.h>
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#include <fcntl.h>
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#include <pwd.h>
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#include <grp.h>
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#include "sudoers.h"
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#include "check.h"
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static bool display_lecture(int);
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static struct passwd *get_authpw(int);
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struct getpass_closure {
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int tstat;
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void *cookie;
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struct passwd *auth_pw;
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};
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/*
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* Called when getpass is suspended so we can drop the lock.
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*/
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static int
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getpass_suspend(int signo, void *vclosure)
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{
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struct getpass_closure *closure = vclosure;
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timestamp_close(closure->cookie);
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closure->cookie = NULL;
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return 0;
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}
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/*
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* Called when getpass is resumed so we can reacquire the lock.
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*/
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static int
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getpass_resume(int signo, void *vclosure)
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{
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struct getpass_closure *closure = vclosure;
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closure->cookie = timestamp_open(user_name, user_sid);
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if (closure->cookie == NULL)
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return -1;
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if (!timestamp_lock(closure->cookie, closure->auth_pw))
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return -1;
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return 0;
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}
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/*
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* Returns true if the user successfully authenticates, false if not
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* or -1 on fatal error.
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*/
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static int
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check_user_interactive(int validated, int mode, struct getpass_closure *closure)
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{
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struct sudo_conv_callback cb, *callback = NULL;
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int ret = -1;
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char *prompt;
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bool lectured;
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debug_decl(check_user_interactive, SUDOERS_DEBUG_AUTH)
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/* Open, lock and read time stamp file if we are using it. */
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if (!ISSET(mode, MODE_IGNORE_TICKET)) {
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/* Open time stamp file and check its status. */
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closure->cookie = timestamp_open(user_name, user_sid);
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if (timestamp_lock(closure->cookie, closure->auth_pw))
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closure->tstat = timestamp_status(closure->cookie, closure->auth_pw);
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/* Construct callback for getpass function. */
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memset(&cb, 0, sizeof(cb));
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cb.version = SUDO_CONV_CALLBACK_VERSION;
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cb.closure = &closure;
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cb.on_suspend = getpass_suspend;
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cb.on_resume = getpass_resume;
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callback = &cb;
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}
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switch (closure->tstat) {
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case TS_FATAL:
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/* Fatal error (usually setuid failure), unsafe to proceed. */
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goto done;
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case TS_CURRENT:
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/* Time stamp file is valid and current. */
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if (!ISSET(validated, FLAG_CHECK_USER)) {
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ret = true;
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break;
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}
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sudo_debug_printf(SUDO_DEBUG_INFO,
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"%s: check user flag overrides time stamp", __func__);
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/* FALLTHROUGH */
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default:
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/* Bail out if we are non-interactive and a password is required */
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if (ISSET(mode, MODE_NONINTERACTIVE)) {
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validated |= FLAG_NON_INTERACTIVE;
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log_auth_failure(validated, 0);
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goto done;
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}
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/* XXX - should not lecture if askpass helper is being used. */
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lectured = display_lecture(closure->tstat);
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/* Expand any escapes in the prompt. */
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prompt = expand_prompt(user_prompt ? user_prompt : def_passprompt,
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closure->auth_pw->pw_name);
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if (prompt == NULL)
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goto done;
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ret = verify_user(closure->auth_pw, prompt, validated, callback);
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if (ret == true && lectured)
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(void)set_lectured(); /* lecture error not fatal */
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free(prompt);
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break;
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}
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done:
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debug_return_int(ret);
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}
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/*
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* Returns true if the user successfully authenticates, false if not
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* or -1 on error.
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*/
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int
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check_user(int validated, int mode)
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{
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struct getpass_closure closure = { TS_ERROR };
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int ret = -1;
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bool exempt = false;
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debug_decl(check_user, SUDOERS_DEBUG_AUTH)
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/*
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* Init authentication system regardless of whether we need a password.
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* Required for proper PAM session support.
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*/
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if ((closure.auth_pw = get_authpw(mode)) == NULL)
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goto done;
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if (sudo_auth_init(closure.auth_pw) == -1)
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goto done;
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/*
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* Don't prompt for the root passwd or if the user is exempt.
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* If the user is not changing uid/gid, no need for a password.
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*/
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if (!def_authenticate || user_is_exempt()) {
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sudo_debug_printf(SUDO_DEBUG_INFO, "%s: %s", __func__,
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!def_authenticate ? "authentication disabled" :
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"user exempt from authentication");
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exempt = true;
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ret = true;
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goto done;
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}
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if (user_uid == 0 || (user_uid == runas_pw->pw_uid &&
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(!runas_gr || user_in_group(sudo_user.pw, runas_gr->gr_name)))) {
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#ifdef HAVE_SELINUX
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if (user_role == NULL && user_type == NULL)
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#endif
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#ifdef HAVE_PRIV_SET
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if (runas_privs == NULL && runas_limitprivs == NULL)
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#endif
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{
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sudo_debug_printf(SUDO_DEBUG_INFO,
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"%s: user running command as self", __func__);
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ret = true;
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goto done;
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}
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}
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ret = check_user_interactive(validated, mode, &closure);
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done:
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if (ret == true) {
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/* The approval function may disallow a user post-authentication. */
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ret = sudo_auth_approval(closure.auth_pw, validated, exempt);
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/*
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* Only update time stamp if user validated and was approved.
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* Failure to update the time stamp is not a fatal error.
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*/
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if (ret == true && closure.tstat != TS_ERROR) {
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if (ISSET(validated, VALIDATE_SUCCESS))
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(void)timestamp_update(closure.cookie, closure.auth_pw);
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}
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}
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timestamp_close(closure.cookie);
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sudo_auth_cleanup(closure.auth_pw);
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if (closure.auth_pw != NULL)
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sudo_pw_delref(closure.auth_pw);
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debug_return_int(ret);
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}
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/*
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* Display sudo lecture (standard or custom).
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* Returns true if the user was lectured, else false.
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*/
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static bool
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display_lecture(int status)
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{
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FILE *fp;
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char buf[BUFSIZ];
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ssize_t nread;
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struct sudo_conv_message msg;
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struct sudo_conv_reply repl;
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debug_decl(lecture, SUDOERS_DEBUG_AUTH)
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if (def_lecture == never ||
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(def_lecture == once && already_lectured(status)))
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debug_return_bool(false);
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memset(&msg, 0, sizeof(msg));
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memset(&repl, 0, sizeof(repl));
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if (def_lecture_file && (fp = fopen(def_lecture_file, "r")) != NULL) {
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while ((nread = fread(buf, sizeof(char), sizeof(buf) - 1, fp)) != 0) {
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buf[nread] = '\0';
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msg.msg_type = SUDO_CONV_ERROR_MSG|SUDO_CONV_PREFER_TTY;
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msg.msg = buf;
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sudo_conv(1, &msg, &repl, NULL);
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}
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fclose(fp);
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} else {
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msg.msg_type = SUDO_CONV_ERROR_MSG|SUDO_CONV_PREFER_TTY;
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msg.msg = _("\n"
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"We trust you have received the usual lecture from the local System\n"
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"Administrator. It usually boils down to these three things:\n\n"
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" #1) Respect the privacy of others.\n"
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" #2) Think before you type.\n"
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" #3) With great power comes great responsibility.\n\n");
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sudo_conv(1, &msg, &repl, NULL);
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}
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debug_return_bool(true);
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}
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/*
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* Checks if the user is exempt from supplying a password.
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*/
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bool
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user_is_exempt(void)
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{
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bool ret = false;
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debug_decl(user_is_exempt, SUDOERS_DEBUG_AUTH)
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if (def_exempt_group)
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ret = user_in_group(sudo_user.pw, def_exempt_group);
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debug_return_bool(ret);
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}
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/*
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* Get passwd entry for the user we are going to authenticate as.
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* By default, this is the user invoking sudo. In the most common
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* case, this matches sudo_user.pw or runas_pw.
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*/
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static struct passwd *
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get_authpw(int mode)
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{
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struct passwd *pw = NULL;
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debug_decl(get_authpw, SUDOERS_DEBUG_AUTH)
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if (ISSET(mode, (MODE_CHECK|MODE_LIST))) {
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/* In list mode we always prompt for the user's password. */
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sudo_pw_addref(sudo_user.pw);
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pw = sudo_user.pw;
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} else {
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if (def_rootpw) {
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if ((pw = sudo_getpwuid(ROOT_UID)) == NULL) {
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log_warningx(SLOG_SEND_MAIL, N_("unknown uid: %u"), ROOT_UID);
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}
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} else if (def_runaspw) {
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if ((pw = sudo_getpwnam(def_runas_default)) == NULL) {
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log_warningx(SLOG_SEND_MAIL,
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N_("unknown user: %s"), def_runas_default);
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}
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} else if (def_targetpw) {
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if (runas_pw->pw_name == NULL) {
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/* This should never be NULL as we fake up the passwd struct */
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log_warningx(SLOG_RAW_MSG, N_("unknown uid: %u"),
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(unsigned int) runas_pw->pw_uid);
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} else {
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sudo_pw_addref(runas_pw);
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pw = runas_pw;
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}
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} else {
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sudo_pw_addref(sudo_user.pw);
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pw = sudo_user.pw;
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}
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}
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debug_return_ptr(pw);
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}
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