C++ drop_privs函数代码示例

/**
 * Spawn external command using system() with dropped privileges.
 * TODO: avoid system() and use exec*() instead
 */
static int spawn_command(const char *cmd, uid_t uid){
	int child;
	int status = -1;

	if (verbose > 1)
		printf("spawn_command: %s\n", cmd);

	child = fork();
	if (child == -1) {
		perror(_("Unable to fork"));
		return status;
	}

	if (child == 0) {
		if (drop_privs(uid) != 0) exit(-1);

		status = system(cmd);
		status_to_retval(status, status);
		exit(status);
	}

	waitpid(child, &status, 0);
	status_to_retval(status, status);
	return status;
}

/*
 * rend_private_init
 *
 * Initialize howl and start runloop
 */
int rend_private_init(char *user) {
    sw_result result;
    
    DPRINTF(E_DBG,L_REND,"Starting rendezvous services\n");
    signal(SIGHUP,  SIG_IGN);           // SIGHUP might happen from a request to reload the daap server

    if(sw_discovery_init(&rend_handle) != SW_OKAY) {
	DPRINTF(E_WARN,L_REND,"Error initializing howl\n");
	errno=EINVAL;
	return -1;
    }

    if(drop_privs(user)) 
	return -1;

    DPRINTF(E_DBG,L_REND,"Starting polling thread\n");
    
    if(pthread_create(&rend_tid,NULL,rend_pipe_monitor,NULL)) {
	DPRINTF(E_FATAL,L_REND,"Could not start thread.  Terminating\n");
	/* should kill parent, too */
	exit(EXIT_FAILURE);
    }

    DPRINTF(E_DBG,L_REND,"Entering runloop\n");

    sw_discovery_run(rend_handle);

    DPRINTF(E_DBG,L_REND,"Exiting runloop\n");

    return 0;
}

int main(int argc, char* argv[]) {
    int rc;

    /* drop privileges */
    if (drop_privs() < 0) return EXIT_FAILURE;

    /* parse arguments */
    parse_args(argc, argv);

    /* initialize secure storage directory */
    rc = storage_init(ss_data_root);
    if (rc < 0) return EXIT_FAILURE;

    /* open rpmb device */
    rc = rpmb_open(rpmb_devname, dev_type);
    if (rc < 0) return EXIT_FAILURE;

    /* connect to Trusty secure storage server */
    rc = ipc_connect(trusty_devname, ss_srv_name);
    if (rc < 0) return EXIT_FAILURE;

    /* enter main loop */
    rc = proxy_loop();
    ALOGE("exiting proxy loop with status (%d)\n", rc);

    ipc_disconnect();
    rpmb_close();

    return (rc < 0) ? EXIT_FAILURE : EXIT_SUCCESS;
}

static int do_mount(const char *dev, const char *mnt, const char *type,
                    mode_t rootmode, int fd, int fuseflags)
{
    int res;
    struct fuse_mount_data data;
    int flags = MS_NOSUID | MS_NODEV;

    if(getuid() != 0) {
        res = drop_privs();
        if(res == -1)
            return -1;

        flags |= MS_PERMISSION;
    }

    data.version = FUSE_KERNEL_VERSION;
    data.fd = fd;
    data.rootmode = rootmode;
    data.uid = getuid();
    data.flags = fuseflags;

    res = mount(dev, mnt, type, flags, &data);
    if(res == -1)
        fprintf(stderr, "%s: mount failed: %s\n", progname, strerror(errno));

    if(getuid() != 0)
        restore_privs();

    return res;
}

static int try_open(const char *dev, char **devp)
{
    int fd;
     
    if (restore_privs())
	return -1;
    fd = open(dev, O_RDWR);
    if (drop_privs())
	return -1;
    if (fd != -1) {
        *devp = strdup(dev);
        if (*devp == NULL) {
            fprintf(stderr, "%s: failed to allocate memory\n", progname);
            close(fd);
            fd = -1;
        }
    } else if (errno == ENODEV ||
               errno == ENOENT) /* check for ENOENT too, for the udev case */
        return -2;
    else {
        fprintf(stderr, "%s: failed to open %s: %s\n", progname, dev,
                strerror(errno));
    }
    return fd;
}

int main(void)
{
    _buttonusr_isr = (void *)&buttonisr_usr;
    _timerusr_isr = (void *)&timerisr_usr;
    _mmhusr_isr = (void *)&mmhisr;

    /* Drop privileges */
    drop_privs();

    /* Init board */
    kk_board_init();

    /* Program the model into OTP, if we're not in screen-test mode, and it's
     * not already there
     */
    (void)flash_programModel();

    /* Init for safeguard against stack overflow (-fstack-protector-all) */
    __stack_chk_guard = (uintptr_t)random32();

    /* Bootloader Verification */
    check_bootloader();

    led_func(SET_RED_LED);
    dbg_print("Application Version %d.%d.%d\n\r", MAJOR_VERSION, MINOR_VERSION,
              PATCH_VERSION);

    /* Init storage */
    storage_init();

    /* Init protcol buffer message map and usb msg callback */
    fsm_init();

    led_func(SET_GREEN_LED);

    usbInit();
    u2fInit();
    led_func(CLR_RED_LED);

    reset_idle_time();

    if (is_mfg_mode())
        layout_screen_test();
    else if (!storage_isInitialized())
        layout_standard_notification("Welcome", "keepkey.com/get-started",
                                     NOTIFICATION_LOGO);
    else
        layoutHomeForced();

    while (1) {
        delay_ms_with_callback(ONE_SEC, &exec, 1);
        increment_idle_time(ONE_SEC);
        toggle_screensaver();
    }

    return 0;
}

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

	ASSERT0(putenv("TZ=UTC"));

	cmn_err(CE_INFO, "blahgd version %s", version_string);

	/* drop unneeded privs */
	ret = drop_privs();
	if (ret)
		goto err;

	jeffpc_init(&init_ops);
	init_math(true);
	init_pipe_subsys();
	init_req_subsys();
	init_post_subsys();
	init_file_cache();

	ret = config_load((argc >= 2) ? argv[1] : NULL);
	if (ret)
		goto err;

	ret = load_all_posts();
	if (ret)
		goto err;

	handle_signals();

	ret = start_helpers();
	if (ret)
		goto err_helpers;

	ret = start_listening();
	if (ret)
		goto err_helpers;

	accept_conns();

	stop_listening();

	stop_helpers();

	free_all_posts();
	uncache_all_files();

	return 0;

err_helpers:
	stop_helpers();

err:
	DBG("Failed to inintialize: %s", xstrerror(ret));

	return ret;
}

void tree(void) {
	drop_privs(1);
	
	char *arg[4];
	arg[0] = "bash";
	arg[1] = "-c";
	arg[2] = "firemon --tree";
	arg[3] = NULL;
	execvp("/bin/bash", arg); 
}

void netstats(void) {
	drop_privs(1);
	
	char *arg[4];
	arg[0] = "bash";
	arg[1] = "-c";
	arg[2] = "firemon --netstats";
	arg[3] = NULL;
	execvp("/bin/bash", arg); 
}

void tree(void) {
	EUID_ASSERT();
	drop_privs(1);
	char *cmd = get_firemon_path("--tree");
	
	char *arg[4];
	arg[0] = "bash";
	arg[1] = "-c";
	arg[2] = cmd;
	arg[3] = NULL;
	execvp("/bin/bash", arg); 
}

void seccomp_print_filter(pid_t pid) {
	// if the pid is that of a firejail  process, use the pid of the first child process
	char *comm = pid_proc_comm(pid);
	if (comm) {
		// remove \n
		char *ptr = strchr(comm, '\n');
		if (ptr)
			*ptr = '\0';
		if (strcmp(comm, "firejail") == 0) {
			pid_t child;
			if (find_child(pid, &child) == 0) {
				pid = child;
			}
		}
		free(comm);
	}

	// check privileges for non-root users
	uid_t uid = getuid();
	if (uid != 0) {
		struct stat s;
		char *dir;
		if (asprintf(&dir, "/proc/%u/ns", pid) == -1)
			errExit("asprintf");
		if (stat(dir, &s) < 0)
			errExit("stat");
		if (s.st_uid != uid) {
			printf("Error: permission denied.\n");
			exit(1);
		}
	}


	// find the seccomp filter
	char *fname;
	if (asprintf(&fname, "/proc/%d/root/tmp/firejail/mnt/seccomp", pid) == -1)
		errExit("asprintf");

	struct stat s;
	if (stat(fname, &s) == -1) {
		printf("Cannot access seccomp filter.\n");
		exit(1);
	}

	// read and print the filter
	read_seccomp_file(fname);
	drop_privs(1);
	filter_debug();

	exit(0);
}

static void set_privileges(void) {
	struct stat s;
	if (stat("/proc/sys/kernel/grsecurity", &s) == 0) {
		EUID_ROOT();

		// elevate privileges
		if (setreuid(0, 0))
			errExit("setreuid");
		if (setregid(0, 0))
			errExit("setregid");
	}
	else
		drop_privs(1);
}

void seccomp_print_filter(pid_t pid) {
	EUID_ASSERT();
	
	// if the pid is that of a firejail  process, use the pid of the first child process
	char *comm = pid_proc_comm(pid);
	if (comm) {
		// remove \n
		char *ptr = strchr(comm, '\n');
		if (ptr)
			*ptr = '\0';
		if (strcmp(comm, "firejail") == 0) {
			pid_t child;
			if (find_child(pid, &child) == 0) {
				pid = child;
			}
		}
		free(comm);
	}

	// check privileges for non-root users
	uid_t uid = getuid();
	if (uid != 0) {
		uid_t sandbox_uid = pid_get_uid(pid);
		if (uid != sandbox_uid) {
			fprintf(stderr, "Error: permission denied.\n");
			exit(1);
		}
	}


	// find the seccomp filter
	EUID_ROOT();
	char *fname;
	if (asprintf(&fname, "/proc/%d/root%s", pid, RUN_SECCOMP_CFG) == -1)
		errExit("asprintf");

	struct stat s;
	if (stat(fname, &s) == -1) {
		printf("Cannot access seccomp filter.\n");
		exit(1);
	}

	// read and print the filter
	read_seccomp_file(fname);
	drop_privs(1);
	filter_debug();
	free(fname);

	exit(0);
}

int main (int argc, char *argv[])
{
   int     pid,index,usable;
   char    *pgname;

   pgname = argv[0];

   if (argc < 2)
   {
      printf("%s: nothing to do\n",pgname);
      exit(0);
   }

   /* printf("Real UID\tReal GID\tEff UID\tEff GID\n"); */

   init_privs();

   set_privs();

   while (argc > 1)
   {
      usable = 1;

      for (index=0; index < strlen(argv[1]); index++)
      {
	 if (!isdigit(argv[1][index]))
         {
            usable = 0;
            break;
         }
      }

      if (usable)
      {
         pid = atoi(argv[1]);
         /* printf("pid is %d\n",pid); */
         kill(pid,SIGUSR1);
      }
      else
         printf("%s: invalid argument %s\n",pgname,argv[1]);

      argc--;
      argv++;
   }

   drop_privs();

   exit(0);
}

int main(int argc, char* argv[]) {
    
    int sockfd = init_socket();
    logf("Server listening on port %d\n", PORT);
  
    if (signal(SIGCHLD, SIG_IGN) == SIG_ERR) {
        perror("Error setting SIGCHILD handler.");
        return EXIT_FAILURE;
    }

    load_module();

    while (1) {
        socklen_t client_len = sizeof(client);
        int client_fd = accept(sockfd, (struct sockaddr*) &client, &client_len);
        if (client_fd < 0) {
            perror("Error creating socket for incoming connection");
            exit(EXIT_FAILURE);
        }
        logf("New connection from %s on port %d\n", inet_ntoa(client.sin_addr), htons(client.sin_port));

        int pid = fork();
        if (pid < 0) {
            perror("Unable to fork");
            exit(EXIT_FAILURE);
        }

        if (pid == 0) { // client
            alarm(300);
            close(sockfd);

            dup2(client_fd, 0);
            dup2(client_fd, 1);
            setvbuf(stdout, NULL, _IONBF, 0);

            drop_privs();

            interact();

            close(client_fd);
            logf("%s:%d disconnected\n", inet_ntoa(client.sin_addr), htons(client.sin_port));
            exit(EXIT_SUCCESS);
        } else {        // server
            logf("%s:%d forked new process with pid %d\n", inet_ntoa(client.sin_addr), htons(client.sin_port), pid);
            close(client_fd);
        }

    }
}