C++ drop_privileges函数代码示例

int main(){

  printf("Efective user: %s\n", get_effective_user_name());
  printf("Real user: %s\n", get_user_name());
  printf("\n");

  printf("drop_privs temp\n");
  int ret1 = drop_privileges(0); 
  printf("Efective user: %s\n", get_effective_user_name());
  printf("Real user: %s\n", get_user_name());
  printf("\n");

  printf("restore privs\n");
  int ret2 = restore_privileges();
  printf("Efective user: %s\n", get_effective_user_name());
  printf("Real user: %s\n", get_user_name());
  printf("\n");

  printf("drop_privs definitive\n");
  int ret3 = drop_privileges(1); 
  printf("Efective user: %s\n", get_effective_user_name());
  printf("Real user: %s\n", get_user_name());
  printf("\n");

  printf("restore privs\n");
  int ret4 = restore_privileges();
  printf("Efective user: %s\n", get_effective_user_name());
  printf("Real user: %s\n", get_user_name());
  printf("\n");

  printf("return values: %d, %d, %d, %d\n", ret1, ret2, ret3, ret4);

  return 0;
}

static void test_drop_privileges_fail(void) {
        assert_se(drop_privileges(test_uid, test_gid, test_flags) >= 0);
        assert_se(getuid() == test_uid);
        assert_se(getgid() == test_gid);

        assert_se(drop_privileges(test_uid, test_gid, test_flags) < 0);
        assert_se(drop_privileges(0, 0, test_flags) < 0);
}

    /* configuration-dependent initialization */
int main_configure(char *arg1, char *arg2) {
    if(parse_commandline(arg1, arg2))
        return 1;
    str_canary_init(); /* needs prng initialization from parse_commandline */
#if !defined(USE_WIN32) && !defined(__vms)
    /* syslog_open() must be called before change_root()
     * to be able to access /dev/log socket */
    syslog_open();
#endif /* !defined(USE_WIN32) && !defined(__vms) */
    if(bind_ports())
        return 1;

#ifdef HAVE_CHROOT
    /* change_root() must be called before drop_privileges()
     * since chroot() needs root privileges */
    if(change_root())
        return 1;
#endif /* HAVE_CHROOT */

#if !defined(USE_WIN32) && !defined(__vms) && !defined(USE_OS2)
    if(drop_privileges(1))
        return 1;
#endif /* standard Unix */

    /* log_open() must be be called after drop_privileges()
     * or logfile rotation won't be possible */
    /* log_open() must be be called before daemonize()
     * since daemonize() invalidates stderr */
    log_open();
    return 0;
}

/*
 * Return: TEST_OK, TEST_ERR or TEST_SKIP
 * we return TEST_OK only if the children return with the expected
 * 'expected_status' that is specified as an argument.
 */
static int kdbus_fork_test(const char *bus, const char *name,
			   struct kdbus_conn **conn_db, int expected_status)
{
	pid_t pid;
	int ret = 0;
	int status = 0;

	pid = fork();
	ASSERT_RETURN_VAL(pid >= 0, pid);

	if (pid == 0) {
		ret = prctl(PR_SET_PDEATHSIG, SIGKILL);
		ASSERT_EXIT(ret == 0);

		ret = drop_privileges(65534, 65534);
		ASSERT_EXIT(ret == 0);

		ret = kdbus_recv_in_threads(bus, name, conn_db);
		_exit(ret == expected_status ? EXIT_SUCCESS : EXIT_FAILURE);
	}

	ret = waitpid(pid, &status, 0);
	ASSERT_RETURN(ret >= 0);

	return (status == EXIT_SUCCESS) ? TEST_OK : TEST_ERR;
}

int mqtt3_log_init(struct mqtt3_config *config)
{
	int rc = 0;

	log_priorities = config->log_type;
	log_destinations = config->log_dest;

	if(log_destinations & MQTT3_LOG_SYSLOG){
#ifndef WIN32
		openlog("mosquitto", LOG_PID|LOG_CONS, config->log_facility);
#else
		syslog_h = OpenEventLog(NULL, "mosquitto");
#endif
	}

	if(log_destinations & MQTT3_LOG_FILE){
		if(drop_privileges(config, true)){
			return 1;
		}
		config->log_fptr = _mosquitto_fopen(config->log_file, "at");
		if(!config->log_fptr){
			log_destinations = MQTT3_LOG_STDERR;
			log_priorities = MOSQ_LOG_ERR;
			_mosquitto_log_printf(NULL, MOSQ_LOG_ERR, "Error: Unable to open log file %s for writing.", config->log_file);
			return MOSQ_ERR_INVAL;
		}
		restore_privileges();
	}
	return rc;
}

int main(void) {
  int ssock = negchke(socket(AF_INET6, SOCK_STREAM, 0), "unable to create socket");
  struct sockaddr_in6 addr = {
    .sin6_family = AF_INET6,
    .sin6_port = htons(PORT),
    .sin6_addr = IN6ADDR_ANY_INIT
  };
  int one = 1;
  negchke(setsockopt(ssock, SOL_SOCKET, SO_REUSEADDR, &one, sizeof(one)), "unable to set SO_REUSEADDR");
  negchke(bind(ssock, (struct sockaddr *)&addr, sizeof(addr)), "unable to bind");
  negchke(listen(ssock, 16), "unable to listen");

  //signal(SIGCHLD, SIG_IGN);

  while (1) {
    client_fd = negchke(accept(ssock, NULL, NULL), "unable to accept");
    pid_t pid = negchke(fork(), "unable to fork");
    if (pid == 0) {
      close(ssock);
      drop_privileges();
      handle_request();
      return 0;
    }
    close(client_fd);
  }
}

int
main(int argc, char **argv)
{
	LibHalContext *ctx = NULL;
	DBusError error;
	GMainLoop *loop = g_main_loop_new(NULL, FALSE);
	char *udi;

	if ((udi = getenv("UDI")) == NULL) {
		return (0);
	}

	drop_privileges();

	setup_logger();

	dbus_error_init(&error);

	if ((ctx = libhal_ctx_init_direct(&error)) == NULL) {
		return (0);
	}

	if (!libhal_device_addon_is_ready(ctx, udi, &error)) {
		return (0);
	}

	if (nds_claim_interface(ctx, udi, &error) != 0) {
		return (0);
	}

	g_main_loop_run(loop);

	/* NOTREACHED */
}

    /* configuration-dependent initialization */
int main_configure(char *arg1, char *arg2) {
    if(options_cmdline(arg1, arg2))
        return 1;
    options_apply();
    str_canary_init(); /* needs prng initialization from options_cmdline */
#if !defined(USE_WIN32) && !defined(__vms)
    /* syslog_open() must be called before change_root()
     * to be able to access /dev/log socket */
    syslog_open();
#endif /* !defined(USE_WIN32) && !defined(__vms) */
    if(bind_ports())
        return 1;

#ifdef HAVE_CHROOT
    /* change_root() must be called before drop_privileges()
     * since chroot() needs root privileges */
    if(change_root())
        return 1;
#endif /* HAVE_CHROOT */

    if(drop_privileges(1))
        return 1;

    /* log_open() must be be called after drop_privileges()
     * or logfile rotation won't be possible */
    /* log_open() must be be called before daemonize()
     * since daemonize() invalidates stderr */
    if(log_open())
        return 1;
#ifndef USE_FORK
    num_clients=0; /* the first valid config */
#endif
    return 0;
}

int main(int argc, char *argv[]) {
        int r, accept_fd;
        uid_t uid, bus_uid;
        gid_t gid;

        log_set_target(LOG_TARGET_JOURNAL_OR_KMSG);
        log_parse_environment();
        log_open();

        bus_uid = getuid();

        if (geteuid() == 0) {
                const char *user = "systemd-bus-proxy";

                r = get_user_creds(&user, &uid, &gid, NULL, NULL);
                if (r < 0) {
                        log_error_errno(r, "Cannot resolve user name %s: %m", user);
                        goto finish;
                }

                r = drop_privileges(uid, gid, 1ULL << CAP_IPC_OWNER);
                if (r < 0) {
                        log_error_errno(r, "Cannot drop privileges: %m");
                        goto finish;
                }
        }

        r = parse_argv(argc, argv);
        if (r <= 0)
                goto finish;

        r = sd_listen_fds(0);
        if (r != 1) {
                log_error("Illegal number of file descriptors passed");
                goto finish;
        }

        accept_fd = SD_LISTEN_FDS_START;

        r = fd_nonblock(accept_fd, false);
        if (r < 0) {
                log_error_errno(r, "Cannot mark accept-fd non-blocking: %m");
                goto finish;
        }

        r = loop_clients(accept_fd, bus_uid);

finish:
        sd_notify(false,
                  "STOPPING=1\n"
                  "STATUS=Shutting down.");

        strv_free(arg_configuration);
        free(arg_address);

        return r < 0 ? EXIT_FAILURE : EXIT_SUCCESS;
}

int main(int argc, char *argv[])
{
	const struct setting_parser_info *set_roots[] = {
		&lda_setting_parser_info,
		&lmtp_setting_parser_info,
		NULL
	};
	enum master_service_flags service_flags =
		MASTER_SERVICE_FLAG_USE_SSL_SETTINGS;
	enum mail_storage_service_flags storage_service_flags =
		MAIL_STORAGE_SERVICE_FLAG_DISALLOW_ROOT |
		MAIL_STORAGE_SERVICE_FLAG_USERDB_LOOKUP |
		MAIL_STORAGE_SERVICE_FLAG_TEMP_PRIV_DROP |
		MAIL_STORAGE_SERVICE_FLAG_NO_LOG_INIT |
		MAIL_STORAGE_SERVICE_FLAG_NO_IDLE_TIMEOUT |
		MAIL_STORAGE_SERVICE_FLAG_AUTOEXPUNGE;
	int c;

	if (IS_STANDALONE()) {
		service_flags |= MASTER_SERVICE_FLAG_STANDALONE |
			MASTER_SERVICE_FLAG_STD_CLIENT;
	} else {
		service_flags |= MASTER_SERVICE_FLAG_KEEP_CONFIG_OPEN  ;
	}

	master_service = master_service_init("lmtp", service_flags,
					     &argc, &argv, "D");
	while ((c = master_getopt(master_service)) > 0) {
		switch (c) {
		case 'D':
			storage_service_flags |=
				MAIL_STORAGE_SERVICE_FLAG_ENABLE_CORE_DUMPS;
			break;
		default:
			return FATAL_DEFAULT;
		}
	}

	if (t_get_current_dir(&base_dir) < 0)
		i_fatal("getcwd() failed: %m");
	drop_privileges();
	master_service_init_log(master_service,
				t_strdup_printf("lmtp(%s): ", my_pid));

	storage_service = mail_storage_service_init(master_service, set_roots,
						    storage_service_flags);
	restrict_access_allow_coredumps(TRUE);

	main_init();
	master_service_init_finish(master_service);
	master_service_run(master_service, client_connected);

	main_deinit();
	mail_storage_service_deinit(&storage_service);
	master_service_deinit(&master_service);
	return 0;
}

static int __kdbus_clone_userns_test(const char *bus,
				     struct kdbus_conn *conn,
				     uint64_t grandpa_pid,
				     int signal_fd)
{
	int clone_ret;
	int ret;
	struct kdbus_msg *msg = NULL;
	const struct kdbus_item *item;
	uint64_t cookie = time(NULL) ^ 0xdeadbeef;
	struct kdbus_conn *unpriv_conn = NULL;
	struct kdbus_pids parent_pids = {
		.pid = getppid(),
		.tid = getppid(),
		.ppid = grandpa_pid,
	};

	ret = drop_privileges(UNPRIV_UID, UNPRIV_GID);
	ASSERT_EXIT(ret == 0);

	unpriv_conn = kdbus_hello(bus, 0, NULL, 0);
	ASSERT_EXIT(unpriv_conn);

	ret = kdbus_add_match_empty(unpriv_conn);
	ASSERT_EXIT(ret == 0);

	/*
	 * ping privileged connection from this new unprivileged
	 * one
	 */

	ret = kdbus_msg_send(unpriv_conn, NULL, cookie, 0, 0,
			     0, conn->id);
	ASSERT_EXIT(ret == 0);

	/*
	 * Since we just dropped privileges, the dumpable flag
	 * was just cleared which makes the /proc/$clone_child/uid_map
	 * to be owned by root, hence any userns uid mapping will fail
	 * with -EPERM since the mapping will be done by uid 65534.
	 *
	 * To avoid this set the dumpable flag again which makes
	 * procfs update the /proc/$clone_child/ inodes owner to 65534.
	 *
	 * Using this we will be able write to /proc/$clone_child/uid_map
	 * as uid 65534 and map the uid 65534 to 0 inside the user namespace.
	 */
	ret = prctl(PR_SET_DUMPABLE, SUID_DUMP_USER);
	ASSERT_EXIT(ret == 0);

	/* Make child privileged in its new userns and run tests */

	ret = RUN_CLONE_CHILD(&clone_ret,
			      SIGCHLD | CLONE_NEWUSER | CLONE_NEWPID,
	({ 0;  /* Clone setup, nothing */ }),

/* Process command line args, create the bound socket,
 * spawn child (worker) processes, and wait for them all to die
 * (which they shouldn't!) */
int main(int argc, char **argv) {

    parse_cli(argc, argv);

    if (OPTIONS.SYSLOG)
        openlog("stud", LOG_CONS | LOG_PID | LOG_NDELAY, LOG_DAEMON);

    signal(SIGPIPE, SIG_IGN);

    listener_socket = create_main_socket();

    struct addrinfo hints;
    memset(&hints, 0, sizeof hints);
    hints.ai_family = AF_UNSPEC;
    hints.ai_socktype = SOCK_STREAM;
    hints.ai_flags = 0;
    const int gai_err = getaddrinfo(OPTIONS.BACK_IP, OPTIONS.BACK_PORT,
                                    &hints, &backaddr);
    if (gai_err != 0) {
        ERR("{getaddrinfo}: [%s]", gai_strerror(gai_err));
        exit(1);
    }

    /* load certificate, pass to handle_connections */
    SSL_CTX * ctx = init_openssl();

    master_pid = getpid();

    if (OPTIONS.CHROOT && OPTIONS.CHROOT[0])
        change_root();

    if (OPTIONS.UID || OPTIONS.GID)
        drop_privileges();

    for (child_num=0; child_num < OPTIONS.NCORES; child_num++) {
        int pid = fork();
        if (pid == -1) {
            ERR("{core} fork() failed! Goodbye cruel world!\n");
            exit(1);
        }
        else if (pid == 0) // child
            goto handle;
    }

    int child_status;
    int dead_child_pid = wait(&child_status);
    ERR("{core} A child (%d) died!  This should not happen! Goodbye cruel world!\n", dead_child_pid);
    kill(0, SIGTERM);
    exit(2);

handle:
    handle_connections(ctx);

    return 0;
}

/*
 * Authorize authenticated OTP_ID for login as USERNAME using
 * AUTHFILE.  Return 0 on failures, otherwise success.
 */
static int
authorize_user_token (struct cfg *cfg,
                      const char *username,
                      const char *otp_id,
                      pam_handle_t *pamh)
{
    int retval;

    if (cfg->auth_file)
    {
        /* Administrator had configured the file and specified is name
           as an argument for this module.
         */
        DBG (("Using system-wide auth_file %s", cfg->auth_file));
        retval = check_user_token (cfg, cfg->auth_file, username, otp_id);
    }
    else
    {
        char *userfile = NULL;
        struct passwd *p;

        p = getpwnam (username);
        if (p == NULL) {
            DBG (("getpwnam: %s", strerror(errno)));
            return 0;
        }

        /* Getting file from user home directory
           ..... i.e. ~/.yubico/authorized_yubikeys
         */
        if (! get_user_cfgfile_path (NULL, "authorized_yubikeys", username, &userfile)) {
            D (("Failed figuring out per-user cfgfile"));
            return 0;
        }

        DBG (("Dropping privileges"));

        if (drop_privileges(p, pamh) < 0) {
            D (("could not drop privileges"));
            return 0;
        }

        retval = check_user_token (cfg, userfile, username, otp_id);

        if (restore_privileges(pamh) < 0)
        {
            DBG (("could not restore privileges"));
            return 0;
        }

        free (userfile);
    }

    return retval;
}

static void test_have_effective_cap(void) {
        assert_se(have_effective_cap(CAP_KILL));
        assert_se(have_effective_cap(CAP_CHOWN));

        assert_se(drop_privileges(test_uid, test_gid, test_flags | (1ULL << CAP_KILL)) >= 0);
        assert_se(getuid() == test_uid);
        assert_se(getgid() == test_gid);

        assert_se(have_effective_cap(CAP_KILL));
        assert_se(!have_effective_cap(CAP_CHOWN));
}

int main(int argc, char** argv)
{
	int ret = 0;

	parse_command_line(argc, argv);

	if (arg_check_config)
	{
		return check_configuration(arg_dump_config);
	}

#ifndef WIN32
	if (arg_fork)
	{
		ret = fork();
		if (ret == -1)
		{
			LOG_FATAL("Unable to fork to background!");
			return -1;
		}
		else if (ret == 0)
		{
			/* child process - detatch from TTY */
			fclose(stdin);
			fclose(stdout);
			fclose(stderr);
			close(0);
			close(1);
			close(2);
		}
		else
		{
			/* parent process */
			LOG_DEBUG("Forked to background\n");
			return 0;
		}
	}

	if (pidfile_create() == -1)
		return -1;

	if (drop_privileges() == -1)
		return -1;
#endif /* WIN32 */

	ret = main_loop();

#ifndef WIN32
	pidfile_destroy();
#endif

	return ret;
}