convince/sway/ipc-server.c

// See https://i3wm.org/docs/ipc.html for protocol information
#ifndef __FreeBSD__
// Any value will hide SOCK_CLOEXEC on FreeBSD (__BSD_VISIBLE=0)
#define _XOPEN_SOURCE 700
#endif
#include <assert.h>
#include <errno.h>
#include <fcntl.h>
#include <json-c/json.h>
#include <stdbool.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <sys/ioctl.h>
#include <sys/un.h>
#include <unistd.h>
#include <wayland-server.h>
#include "sway/commands.h"
#include "sway/ipc-json.h"
#include "sway/ipc-server.h"
#include "sway/server.h"
#include "list.h"
#include "log.h"

static int ipc_socket = -1;
static struct wl_event_source *ipc_event_source =  NULL;
static struct sockaddr_un *ipc_sockaddr = NULL;
static list_t *ipc_client_list = NULL;

static const char ipc_magic[] = {'i', '3', '-', 'i', 'p', 'c'};

struct ipc_client {
	struct wl_event_source *event_source;
	struct wl_event_source *writable_event_source;
	struct sway_server *server;
	int fd;
	uint32_t payload_length;
	uint32_t security_policy;
	enum ipc_command_type current_command;
	enum ipc_command_type subscribed_events;
	size_t write_buffer_len;
	size_t write_buffer_size;
	char *write_buffer;
};

struct sockaddr_un *ipc_user_sockaddr(void);
int ipc_handle_connection(int fd, uint32_t mask, void *data);
int ipc_client_handle_readable(int client_fd, uint32_t mask, void *data);
int ipc_client_handle_writable(int client_fd, uint32_t mask, void *data);
void ipc_client_disconnect(struct ipc_client *client);
void ipc_client_handle_command(struct ipc_client *client);
bool ipc_send_reply(struct ipc_client *client, const char *payload, uint32_t payload_length);

void ipc_init(struct sway_server *server) {
	ipc_socket = socket(AF_UNIX, SOCK_STREAM | SOCK_NONBLOCK | SOCK_CLOEXEC, 0);
	if (ipc_socket == -1) {
		sway_abort("Unable to create IPC socket");
	}

	ipc_sockaddr = ipc_user_sockaddr();

	// We want to use socket name set by user, not existing socket from another sway instance.
	if (getenv("SWAYSOCK") != NULL && access(getenv("SWAYSOCK"), F_OK) == -1) {
		strncpy(ipc_sockaddr->sun_path, getenv("SWAYSOCK"), sizeof(ipc_sockaddr->sun_path));
		ipc_sockaddr->sun_path[sizeof(ipc_sockaddr->sun_path) - 1] = 0;
	}

	unlink(ipc_sockaddr->sun_path);
	if (bind(ipc_socket, (struct sockaddr *)ipc_sockaddr, sizeof(*ipc_sockaddr)) == -1) {
		sway_abort("Unable to bind IPC socket");
	}

	if (listen(ipc_socket, 3) == -1) {
		sway_abort("Unable to listen on IPC socket");
	}

	// Set i3 IPC socket path so that i3-msg works out of the box
	setenv("I3SOCK", ipc_sockaddr->sun_path, 1);
	setenv("SWAYSOCK", ipc_sockaddr->sun_path, 1);

	ipc_client_list = create_list();

	ipc_event_source = wl_event_loop_add_fd(server->wl_event_loop, ipc_socket,
			WL_EVENT_READABLE, ipc_handle_connection, server);
}

void ipc_terminate(void) {
	if (ipc_event_source) {
		wl_event_source_remove(ipc_event_source);
	}
	close(ipc_socket);
	unlink(ipc_sockaddr->sun_path);

	list_free(ipc_client_list);

	if (ipc_sockaddr) {
		free(ipc_sockaddr);
	}
}

struct sockaddr_un *ipc_user_sockaddr(void) {
	struct sockaddr_un *ipc_sockaddr = malloc(sizeof(struct sockaddr_un));
	if (ipc_sockaddr == NULL) {
		sway_abort("Can't allocate ipc_sockaddr");
	}

	ipc_sockaddr->sun_family = AF_UNIX;
	int path_size = sizeof(ipc_sockaddr->sun_path);

	// Env var typically set by logind, e.g. "/run/user/<user-id>"
	const char *dir = getenv("XDG_RUNTIME_DIR");
	if (!dir) {
		dir = "/tmp";
	}
	if (path_size <= snprintf(ipc_sockaddr->sun_path, path_size,
			"%s/sway-ipc.%i.%i.sock", dir, getuid(), getpid())) {
		sway_abort("Socket path won't fit into ipc_sockaddr->sun_path");
	}

	return ipc_sockaddr;
}

int ipc_handle_connection(int fd, uint32_t mask, void *data) {
	(void) fd;
	struct sway_server *server = data;
	sway_log(L_DEBUG, "Event on IPC listening socket");
	assert(mask == WL_EVENT_READABLE);

	int client_fd = accept(ipc_socket, NULL, NULL);
	if (client_fd == -1) {
		sway_log_errno(L_ERROR, "Unable to accept IPC client connection");
		return 0;
	}

	int flags;
	if ((flags = fcntl(client_fd, F_GETFD)) == -1
			|| fcntl(client_fd, F_SETFD, flags|FD_CLOEXEC) == -1) {
		sway_log_errno(L_ERROR, "Unable to set CLOEXEC on IPC client socket");
		close(client_fd);
		return 0;
	}
	if ((flags = fcntl(client_fd, F_GETFL)) == -1
			|| fcntl(client_fd, F_SETFL, flags|O_NONBLOCK) == -1) {
		sway_log_errno(L_ERROR, "Unable to set NONBLOCK on IPC client socket");
		close(client_fd);
		return 0;
	}

	struct ipc_client *client = malloc(sizeof(struct ipc_client));
	if (!client) {
		sway_log(L_ERROR, "Unable to allocate ipc client");
		close(client_fd);
		return 0;
	}
	client->server = server;
	client->payload_length = 0;
	client->fd = client_fd;
	client->subscribed_events = 0;
	client->event_source = wl_event_loop_add_fd(server->wl_event_loop,
			client_fd, WL_EVENT_READABLE, ipc_client_handle_readable, client);
	client->writable_event_source = NULL;

	client->write_buffer_size = 128;
	client->write_buffer_len = 0;
	client->write_buffer = malloc(client->write_buffer_size);
	if (!client->write_buffer) {
		sway_log(L_ERROR, "Unable to allocate ipc client write buffer");
		close(client_fd);
		return 0;
	}

	sway_log(L_DEBUG, "New client: fd %d", client_fd);
	list_add(ipc_client_list, client);
	return 0;
}

static const int ipc_header_size = sizeof(ipc_magic) + 8;

int ipc_client_handle_readable(int client_fd, uint32_t mask, void *data) {
	struct ipc_client *client = data;

	if (mask & WL_EVENT_ERROR) {
		sway_log(L_ERROR, "IPC Client socket error, removing client");
		ipc_client_disconnect(client);
		return 0;
	}

	if (mask & WL_EVENT_HANGUP) {
		sway_log(L_DEBUG, "Client %d hung up", client->fd);
		ipc_client_disconnect(client);
		return 0;
	}

	sway_log(L_DEBUG, "Client %d readable", client->fd);

	int read_available;
	if (ioctl(client_fd, FIONREAD, &read_available) == -1) {
		sway_log_errno(L_INFO, "Unable to read IPC socket buffer size");
		ipc_client_disconnect(client);
		return 0;
	}

	// Wait for the rest of the command payload in case the header has already been read
	if (client->payload_length > 0) {
		if ((uint32_t)read_available >= client->payload_length) {
			ipc_client_handle_command(client);
		}
		return 0;
	}

	if (read_available < ipc_header_size) {
		return 0;
	}

	uint8_t buf[ipc_header_size];
	uint32_t *buf32 = (uint32_t*)(buf + sizeof(ipc_magic));
	// Should be fully available, because read_available >= ipc_header_size
	ssize_t received = recv(client_fd, buf, ipc_header_size, 0);
	if (received == -1) {
		sway_log_errno(L_INFO, "Unable to receive header from IPC client");
		ipc_client_disconnect(client);
		return 0;
	}

	if (memcmp(buf, ipc_magic, sizeof(ipc_magic)) != 0) {
		sway_log(L_DEBUG, "IPC header check failed");
		ipc_client_disconnect(client);
		return 0;
	}

	client->payload_length = buf32[0];
	client->current_command = (enum ipc_command_type)buf32[1];

	if (read_available - received >= (long)client->payload_length) {
		ipc_client_handle_command(client);
	}

	return 0;
}

int ipc_client_handle_writable(int client_fd, uint32_t mask, void *data) {
	struct ipc_client *client = data;

	if (mask & WL_EVENT_ERROR) {
		sway_log(L_ERROR, "IPC Client socket error, removing client");
		ipc_client_disconnect(client);
		return 0;
	}

	if (mask & WL_EVENT_HANGUP) {
		sway_log(L_DEBUG, "Client %d hung up", client->fd);
		ipc_client_disconnect(client);
		return 0;
	}

	if (client->write_buffer_len <= 0) {
		return 0;
	}

	sway_log(L_DEBUG, "Client %d writable", client->fd);

	ssize_t written = write(client->fd, client->write_buffer, client->write_buffer_len);

	if (written == -1 && errno == EAGAIN) {
		return 0;
	} else if (written == -1) {
		sway_log_errno(L_INFO, "Unable to send data from queue to IPC client");
		ipc_client_disconnect(client);
		return 0;
	}

	memmove(client->write_buffer, client->write_buffer + written, client->write_buffer_len - written);
	client->write_buffer_len -= written;

	if (client->write_buffer_len == 0 && client->writable_event_source) {
		wl_event_source_remove(client->writable_event_source);
		client->writable_event_source = NULL;
	}

	return 0;
}

void ipc_client_disconnect(struct ipc_client *client) {
	if (!sway_assert(client != NULL, "client != NULL")) {
		return;
	}

	if (client->fd != -1) {
		shutdown(client->fd, SHUT_RDWR);
	}

	sway_log(L_INFO, "IPC Client %d disconnected", client->fd);
	wl_event_source_remove(client->event_source);
	if (client->writable_event_source) {
		wl_event_source_remove(client->writable_event_source);
	}
	int i = 0;
	while (i < ipc_client_list->length && ipc_client_list->items[i] != client) {
		i++;
	}
	list_del(ipc_client_list, i);
	free(client->write_buffer);
	close(client->fd);
	free(client);
}

void ipc_client_handle_command(struct ipc_client *client) {
	if (!sway_assert(client != NULL, "client != NULL")) {
		return;
	}

	char *buf = malloc(client->payload_length + 1);
	if (!buf) {
		sway_log_errno(L_INFO, "Unable to allocate IPC payload");
		ipc_client_disconnect(client);
		return;
	}
	if (client->payload_length > 0) {
		// Payload should be fully available
		ssize_t received = recv(client->fd, buf, client->payload_length, 0);
		if (received == -1)
		{
			sway_log_errno(L_INFO, "Unable to receive payload from IPC client");
			ipc_client_disconnect(client);
			free(buf);
			return;
		}
	}
	buf[client->payload_length] = '\0';

	const char *error_denied = "{ \"success\": false, \"error\": \"Permission denied\" }";

	switch (client->current_command) {
	case IPC_COMMAND:
	{
		struct cmd_results *results = handle_command(buf);
		const char *json = cmd_results_to_json(results);
		char reply[256];
		int length = snprintf(reply, sizeof(reply), "%s", json);
		ipc_send_reply(client, reply, (uint32_t) length);
		free_cmd_results(results);
		goto exit_cleanup;
	}

	case IPC_GET_TREE:
	{
		json_object *tree =
			ipc_json_describe_container_recursive(&root_container);
		const char *json_string = json_object_to_json_string(tree);
		ipc_send_reply(client, json_string, (uint32_t) strlen(json_string));
		json_object_put(tree);
		goto exit_cleanup;
	}

	case IPC_GET_VERSION:
	{
		json_object *version = ipc_json_get_version();
		const char *json_string = json_object_to_json_string(version);
		ipc_send_reply(client, json_string, (uint32_t)strlen(json_string));
		json_object_put(version); // free
		goto exit_cleanup;
	}

	default:
		sway_log(L_INFO, "Unknown IPC command type %i", client->current_command);
		goto exit_cleanup;
	}

	ipc_send_reply(client, error_denied, (uint32_t)strlen(error_denied));
	sway_log(L_DEBUG, "Denied IPC client access to %i", client->current_command);

exit_cleanup:
	client->payload_length = 0;
	free(buf);
	return;
}

bool ipc_send_reply(struct ipc_client *client, const char *payload, uint32_t payload_length) {
	assert(payload);

	char data[ipc_header_size];
	uint32_t *data32 = (uint32_t*)(data + sizeof(ipc_magic));

	memcpy(data, ipc_magic, sizeof(ipc_magic));
	data32[0] = payload_length;
	data32[1] = client->current_command;

	while (client->write_buffer_len + ipc_header_size + payload_length >=
				 client->write_buffer_size) {
		client->write_buffer_size *= 2;
	}

	if (client->write_buffer_size > 4e6) { // 4 MB
		sway_log(L_ERROR, "Client write buffer too big, disconnecting client");
		ipc_client_disconnect(client);
		return false;
	}

	char *new_buffer = realloc(client->write_buffer, client->write_buffer_size);
	if (!new_buffer) {
		sway_log(L_ERROR, "Unable to reallocate ipc client write buffer");
		ipc_client_disconnect(client);
		return false;
	}
	client->write_buffer = new_buffer;

	memcpy(client->write_buffer + client->write_buffer_len, data, ipc_header_size);
	client->write_buffer_len += ipc_header_size;
	memcpy(client->write_buffer + client->write_buffer_len, payload, payload_length);
	client->write_buffer_len += payload_length;

	if (!client->writable_event_source) {
		client->writable_event_source = wl_event_loop_add_fd(
				server.wl_event_loop, client->fd, WL_EVENT_WRITABLE,
				ipc_client_handle_writable, client);
	}

	sway_log(L_DEBUG, "Added IPC reply to client %d queue: %s", client->fd, payload);
	return true;
}