path: root/src/core/ws_protocol.c

/* BSD-2-Clause license
 * 
 * Copyright (c) 2018-2023 NST <www.newinfosec.ru>, sss <sss at dark-alexandr dot net>. 
 * 
 */

#include <stdbool.h>
#include <stdio.h>
#include <string.h>

#include <ev.h>
#include <json.h>
#include <wslay/wslay.h>
#include <curl/curl.h>

#include <errno.h>
#include "base64_url.h"

#include <openssl/hmac.h>

#include <webrdp_module_api.h>

#include "wrdp_thpool.h"
#include "wrdp_thpool_internals.h"
#include "ws_session.h"
#include "ws_protocol.h"
#include "globals.h"
#include "task.h"
#include "thread_impl.h"
#include "json_helpers.h"
#include "curl_helpers.h"
#include "backend_helpers.h"

#include "utilities.h"

#include "log.h"

static bool
token_check(ws_session *session)
{
	char *token = session->token_base64;
	size_t token_len = strlen(token), raw_token_len = 0;
	unsigned int raw_token_signature_len = 0;
	/* used additional 2 bytes in buffer
	 * required for base64_url_decode */
	uint8_t *raw_token = malloc(96 + 2), *raw_token_signature = 0;
	if (!raw_token)
	{
		perror("malloc");
		goto error;
	}
	{
		char buf[128];
		snprintf(buf, 127, "recieved token: %s", token);
		log_msg(
		    (const uint8_t *)buf, strlen(buf), wrdp_log_level_trace, 0);
	}
	errno = base64_url_decode(
	    (uint8_t *)token, token_len, raw_token, token_len, &raw_token_len);
	if (errno)
	{
		perror("token_check: base64_url_decode");
		free(raw_token);
		goto error;
	}
	if (raw_token_len != 96)
	{
		const char *msg = "token_check: raw_roken length != 96";
		log_msg(
		    (const uint8_t *)msg, strlen(msg), wrdp_log_level_error, 0);
		free(raw_token);
		goto error;
	}
	raw_token_signature = malloc(32);
	if (!raw_token_signature)
	{
		perror("malloc");
		free(raw_token);
		goto error;
	}
	/* verify token */
	{
		HMAC_CTX *ctx = HMAC_CTX_new();
		HMAC_Init_ex(ctx, g_globals.settings.secret_key_verify, 64,
		    EVP_sha256(), NULL);
		HMAC_Update(ctx, raw_token, raw_token_len - 32);
		HMAC_Final(ctx, raw_token_signature, &raw_token_signature_len);
		HMAC_CTX_free(ctx);
		if (raw_token_signature_len != 32)
		{
			const char *msg = "token signature validation failed"
					  " (incorrect result hash size)";
			log_msg((const uint8_t *)msg, strlen(msg),
			    wrdp_log_level_error, 0);
			free(raw_token);
			free(raw_token_signature);
			goto error;
		}
#ifdef DEBUG
		{
			log_msg((const uint8_t *)"old hash", strlen("old hash"),
			    wrdp_log_level_trace, wrdp_log_flag_binary);
			log_msg(raw_token + 64, 32, wrdp_log_level_trace,
			    wrdp_log_flag_binary);
			log_msg((const uint8_t *)"new hash", strlen("new hash"),
			    wrdp_log_level_trace, wrdp_log_flag_binary);
			log_msg(raw_token_signature, 32, wrdp_log_level_trace,
			    wrdp_log_flag_binary);
		}
#endif
		if (memcmp(raw_token + 64, raw_token_signature, 32))
		{
			const char *msg
			    = "token signature validation failed (result"
			      " hash differs)";
			log_msg((const uint8_t *)msg, strlen(msg),
			    wrdp_log_level_error, 0);
			free(raw_token);
			free(raw_token_signature);
			goto error;
		}
	}
	/* extract and store base64-urlsafe encoded sid into session */
	{
		/* TODO: check if size calculation correct and optimal */
		size_t sid_len = (4 * (64 / 3)) + 4 + 2, encoded_len = 0;
		char *sid_base64 = calloc(sid_len, sizeof(char)), *ptr;
		base64_url_encode(raw_token, 64, (uint8_t *)sid_base64, sid_len,
		    &encoded_len);
		sid_base64[encoded_len] = 0;
		ptr = realloc(sid_base64, encoded_len + 1);
		if (!ptr)
		{
			//if realloc failed we still can use preveously
			//allocated memory
			perror("realloc");
		}
		else
		{
			sid_base64 = ptr;
		}
		session->sid_base64 = sid_base64;
	}
	/* reencrypt token */
	{
		HMAC_CTX *ctx = HMAC_CTX_new();
		uint8_t resigned_raw_token[96] = {0};
		size_t base64_len = 0;
		HMAC_Init_ex(ctx, g_globals.settings.secret_key_sign, 64,
		    EVP_sha256(), NULL);
		HMAC_Update(ctx, raw_token, raw_token_len - 32);
		HMAC_Final(ctx, raw_token_signature, &raw_token_signature_len);
		HMAC_CTX_free(ctx);
		if (raw_token_signature_len != 32)
		{
			const char *msg
			    = "token signature generation failed (incorrect"
			      " result hash size)";
			log_msg((const uint8_t *)msg, strlen(msg),
			    wrdp_log_level_error, 0);
			free(raw_token);
			free(raw_token_signature);
			goto error;
		}
		memcpy(resigned_raw_token, raw_token, 64);
		memcpy(resigned_raw_token + 64, raw_token_signature, 32);
		errno = base64_url_encode(
		    resigned_raw_token, 96, (uint8_t *)token, 255, &base64_len);
		if (errno)
		{
			free(raw_token);
			free(raw_token_signature);
			perror("token_verify: base64_url_encode");
			goto error;
		}
		token[base64_len] = 0;
	}
	session->token_verified = true;
	free(raw_token);
	free(raw_token_signature);
	return true;
error:
	session->session_state = ws_session_error;
	free(session->token_base64);
	session->token_base64 = 0;
	free(session->backend_module_name);
	session->backend_module_name = 0;
	return false;
}

static bool
handle_session_setting_element(
    struct json_object_element_s *json_option, ws_session *session)
{
	task_info *info = session->task_info;
	/* TODO: move timeouts to session ?
	 * cache timeouts settings until task_info created ?
	 */
	/*	if (!strncmp(json_option->name->string, "session_time_limit",
			json_option->name->string_size))
		{
			info->settings.session_time_limit =
				json_option_extract_int64 (json_option);
			return true;
		}
		else if (!strncmp(json_option->name->string,
	   "session_idle_timeout", json_option->name->string_size))
		{
			info->settings.session_idle_timeout =
				json_option_extract_int64 (json_option);
			return true;
		}
		else */
	if (!strncmp(json_option->name->string, "token",
		json_option->name->string_size))
	{
		struct json_string_s *jsopt
		    = (struct json_string_s *)json_option->value->payload;
		char *token_base64;
		if (!jsopt->string_size)
		{
			const char *msg = "zero size token received";
			log_msg((const uint8_t *)msg, strlen(msg),
			    wrdp_log_level_warning, 0);
			return true;
		}
		token_base64 = malloc(jsopt->string_size + 1);
		memcpy(token_base64, jsopt->string, jsopt->string_size);
		token_base64[jsopt->string_size] = 0;
		if (session->token_base64)
			free(session->token_base64);
		session->token_base64 = token_base64;
		return true;
	}
	else if (!strncmp(json_option->name->string, "attach_sid",
		     json_option->name->string_size))
	{
		/*		if (session->sid_base64)
				{
					free (session->sid_base64);
				} */
		struct json_string_s *jsopt
		    = (struct json_string_s *)json_option->value->payload;
		char *attach_sid = malloc(jsopt->string_size + 1);
		memcpy(attach_sid, jsopt->string, jsopt->string_size);
		attach_sid[jsopt->string_size] = 0;
		if (session->attach_sid_base64)
			free(session->attach_sid_base64);
		session->attach_sid_base64 = attach_sid;
		return true;
	}
	else if (!strncmp(json_option->name->string, "proto",
		     json_option->name->string_size))
	{
		if (info && info->backend)
		{
			/* backend already created, possible by "proto" setting
			 * from web ui */
			return true;
		}
		struct json_string_s *jsopt
		    = (struct json_string_s *)json_option->value->payload;
		char *var = malloc(jsopt->string_size + 1);
		memcpy(var, jsopt->string, jsopt->string_size);
		var[jsopt->string_size] = 0;
		if (session->backend_module_name)
			free(session->backend_module_name);
		session->backend_module_name = var;
		return true;
	}
	{
		char buf[128];
		snprintf(buf, 127,
		    "handle_session_setting:"
		    " unhandled option: %.*s",
		    (int)(json_option->name->string_size),
		    json_option->name->string);
		log_msg((const uint8_t *)buf, strlen(buf),
		    wrdp_log_level_warning, 0);
	}
	return false;
}

static bool
handle_backend_setting_element(
    struct json_object_element_s *json_option, ws_session *session)
{
	char option_name[json_option->name->string_size + 1];
	strncpy(option_name, json_option->name->string,
	    json_option->name->string_size);
	option_name[json_option->name->string_size] = 0;
	switch (json_option->value->type)
	{
		case json_type_null:
		case json_type_false:
		{
			if (!handle_backend_setting_int(
				option_name, 0, session))
			{
				return false;
			}
			return true;
		}
		break;
		case json_type_true:
		{
			if (!handle_backend_setting_int(
				option_name, 1, session))
			{
				return false;
			}
			return true;
		}
		break;
		case json_type_number:
		{
			int64_t num = json_option_extract_int64(json_option);
			if (!handle_backend_setting_int(
				option_name, num, session))
			{
				return false;
			}
			return true;
		}
		break;
		case json_type_string:
		{
			struct json_string_s *jsopt
			    = (struct json_string_s *)
				  json_option->value->payload;
			char value[jsopt->string_size + 1];
			strncpy(value, jsopt->string, jsopt->string_size);
			value[jsopt->string_size] = 0;

			if (!strcmp(option_name, "dtsize"))
			{
				/* extract resolution width and height */
				char *ptr = strchr(value, 'x');
				if (!ptr)
					return false;
				char w[jsopt->string_size],
				    h[jsopt->string_size];
				{
					char *ptr2 = value;
					int i;
					for (i = 0; ptr2 != ptr; ++i, ++ptr2)
					{
						w[i] = ptr2[0];
					}
					w[i] = 0;
					ptr++;
					for (i = 0; ptr[i]; ++i)
					{
						h[i] = ptr[i];
					}
					h[i] = 0;
					{
						if (!handle_backend_setting_int(
							"width", atoll(w),
							session))
						{
							return false;
						}
						if (!handle_backend_setting_int(
							"height", atoll(h),
							session))
						{
							return false;
						}
						return true;
					}
				}
			}
			else
			{
				if (!handle_backend_setting_string(
					option_name, value, session))
				{
					return false;
				}
				return true;
			}
		}
		break;
		default:
		{
			const char *msg = "handle_backend_setting:"
					  " unsupported json value type";
			log_msg((const uint8_t *)msg, strlen(msg),
			    wrdp_log_level_warning, 0);
			return true;
		}
		break;
	}
	{
		char buf[128];
		snprintf(buf, 127,
		    "handle_backend_setting:"
		    " unhandled option: %s",
		    option_name);
		log_msg((const uint8_t *)buf, strlen(buf),
		    wrdp_log_level_warning, 0);
	}
	return true;
}

static void
handle_json_session_option(
    struct json_object_element_s *json_option, ws_session *session)
{
	switch (json_option->value->type)
	{
		case json_type_object:
		{
			if (memmem(json_option->name->string,
				json_option->name->string_size,
				"session_settings", strlen("session_settings")))
			{
				struct json_object_s *obj
				    = json_option->value->payload;
				struct json_object_element_s *jsoption
				    = obj->start;
				bool unhandled_option = false;
				while (jsoption && !unhandled_option)
				{
					unhandled_option
					    = !handle_session_setting_element(
						jsoption, session);
					if (unhandled_option)
						break;
					jsoption = jsoption->next;
				}
				return;
			}
		}
		break;
		default:
		{
			const char *msg
			    = "handle_json_option: unsupported json value type"
			      " (not object)";
			log_msg((const uint8_t *)msg, strlen(msg),
			    wrdp_log_level_warning, 0);
			return;
		}
		break;
	}
}

static void
handle_json_session_options(struct json_value_s *root, ws_session *session)
{
	struct json_object_s *object = (struct json_object_s *)root->payload;
	struct json_object_element_s *option = object->start;
	while (option)
	{
		handle_json_session_option(option, session);
		option = option->next;
	}
}

static void
handle_json_backend_option(
    struct json_object_element_s *json_option, ws_session *session)
{
	switch (json_option->value->type)
	{
		case json_type_object:
		{
			if (memmem(json_option->name->string,
				json_option->name->string_size,
				"backend_settings", strlen("backend_settings")))
			{
				struct json_object_s *obj
				    = json_option->value->payload;
				struct json_object_element_s *jsoption
				    = obj->start;
				bool unhandled_option = false;
				while (jsoption && !unhandled_option)
				{
					unhandled_option
					    = !handle_backend_setting_element(
						jsoption, session);
					if (unhandled_option)
						break;
					jsoption = jsoption->next;
				}
			}
		}
		break;
		default:
		{
			const char *msg
			    = "handle_json_option: unsupported json value type"
			      " (not object)";
			log_msg((const uint8_t *)msg, strlen(msg),
			    wrdp_log_level_warning, 0);
		}
		break;
	}
}

static void
handle_json_backend_options(struct json_value_s *root, ws_session *session)
{
	struct json_object_s *object = (struct json_object_s *)root->payload;
	struct json_object_element_s *option = object->start;
	while (option)
	{
		handle_json_backend_option(option, session);
		option = option->next;
	}
}

static bool
ws_handle_json_settings_array(
    char *json_buf, size_t json_buf_len, ws_session *session)
{
	struct json_parse_result_s res = {0};
	struct json_value_s *root = json_parse_ex(
	    json_buf, json_buf_len, json_parse_flags_allow_json5, 0, 0, &res);
#ifdef DEBUG
	{
		const size_t msg_len = json_buf_len + 256;
		char msg[msg_len];
		snprintf(msg, msg_len, "%s: %s\n", "received json data:\n",
		    json_buf);
		log_msg(
		    (const uint8_t *)msg, strlen(msg), wrdp_log_level_trace, 0);
	}
#endif
	if (!root)
	{
		const char *msg = "Failed to parse auth data json";
		log_msg(
		    (const uint8_t *)msg, strlen(msg), wrdp_log_level_error, 0);
		return false;
	}
	/* handle json data
	 * assume what this is one level array
	 * of json options for backend or session*/
	handle_json_session_options(root, session);
	handle_json_backend_options(root, session);

	if (!session->backend_module_name)
	{
		free(session->token_base64);
		session->token_base64 = 0;
		free(root);
		return false;
	}
	if (!(session->token_verified) && session->token_base64)
	{
		if (!token_check(session))
		{
			free(root);
			return false;
		}
	}
	free(root);
	return true;
}

bool
ws_handle_token_reply_json(
    uint8_t *_json_buf, ws_session *session, void *userdata)
{
	char *json_buf = (char *)_json_buf;
	task_info *info = 0, *old_info = session->task_info;
	if (!ws_handle_json_settings_array(json_buf, strlen(json_buf), session))
	{
		return false;
	}
	if (!backend_get(session->backend_module_name, session))
	{
		free(session->backend_module_name);
		session->backend_module_name = 0;
		return false;
	}
	else
	{
		backend_fill_settings(session);
	}
	free(session->attach_sid_base64);
	session->attach_sid_base64 = 0;
	info = session->task_info;

	if (!info->backend)
	{
		const char *msg = "backend type(proto)setting does not set";
		log_msg(
		    (const uint8_t *)msg, strlen(msg), wrdp_log_level_error, 0);
		return false;
	}
	if (info == old_info
	    && !info->backend->callbacks_module->init(
		info->backend->backend_internals))
	{
		return false;
	}
	session->session_state = ws_session_started;
	{
		uint8_t *data = 0;
		size_t data_size
		    = curl_prepare_post_request_data(&data, session);
		curl_request_info *request = curl_init_request(
		    session, curl_request_type_post, data, data_size, 0, 0, 0);
		free(data);
		curl_request(request);
	}
	return true;
}

static bool
validate_msg_size(
    size_t msg_size, size_t expected_size, ws_input_codes msg_code)
{
	if (msg_size > expected_size)
	{
		char buf[128];
		snprintf(buf, 127,
		    "ws_protocol: message size is: %ld, expected size"
		    " is: %ld for message type %d",
		    msg_size, expected_size, msg_code);
		log_msg((const uint8_t *)buf, strlen(buf),
		    wrdp_log_level_warning, 0);
		return true;
	}
	else if (msg_size < expected_size)
	{
		char buf[128];
		snprintf(buf, 127,
		    "ws_protocol: message size is: %ld, expected size"
		    " is: %ld for message type %d",
		    msg_size, expected_size, msg_code);
		log_msg(
		    (const uint8_t *)buf, strlen(buf), wrdp_log_level_error, 0);
		return false;
	}
	return true;
}

static void
generate_random_session_sid(ws_session *session)
{
	size_t sid_len = (4 * (64 / 3)) + 4 + 2, encoded_len = 0;
	char *sid_base64 = calloc(sid_len, sizeof(char)), *ptr;
	uint8_t random_data[64];
	random_bytes(random_data, 64);
	base64_url_encode(
	    random_data, 64, (uint8_t *)sid_base64, sid_len, &encoded_len);
	sid_base64[encoded_len] = 0;
	ptr = realloc(sid_base64, encoded_len + 1);
	if (!ptr)
	{
		/* if realloc failed we still can use preveously allocated
		 * memory
		 */
		perror("realloc");
	}
	else
	{
		sid_base64 = ptr;
	}
	session->sid_base64 = sid_base64;
}

bool
ws_handle_message(
    const struct wslay_event_on_msg_recv_arg *msg, ws_session *session)
{
	uint32_t hcode1 = 0;
	task_info *info = session->task_info;
	if (msg->msg_length < 4)
	{
		const char *msg = "Error: websocket message is too short";
		log_msg(
		    (const uint8_t *)msg, strlen(msg), wrdp_log_level_error, 0);
		return false;
	}
	memcpy(&hcode1, msg->msg, 4);
	if (session->session_state == ws_session_initial)
	{
		switch (hcode1)
		{
			case ws_in_credential_json:
			{
				size_t str_len = (msg->msg_length - 4) / 4;
				char *str = malloc(str_len + 1);
				if (!str)
				{
					perror("malloc");
					return false;
				}
				{
					size_t i, pos = 4;
					for (i = 0; i < str_len; ++i, pos += 4)
					{
						str[i] = msg->msg[pos];
					}
				}
				str[str_len] = 0;
				if (!ws_handle_json_settings_array(
					str, str_len, session))
				{
					free(str);
					return false;
				}
				free(str);

				/* backend and task_info created/set inside
				 * "ws_handle_json_settings_array", refresh
				 * pointer here */
				info = session->task_info;

				/* TODO: DEBUG BEGIN*/
				//use_token = true;
				/* DEBUG END */
				if (!session->token_base64)
				{
					if (!info || !info->backend)
					{
						const char *msg
						    = "backend "
						      "type(proto)setting"
						      "does not set";
						log_msg((const uint8_t *)msg,
						    strlen(msg),
						    wrdp_log_level_error, 0);
						return false;
					}
					if (!info->backend->callbacks_module
						 ->init(
						     info->backend
							 ->backend_internals))
					{
						return false;
					}
					/* token is not used, we need to
					 * generate random sid */
					generate_random_session_sid(session);
					session->session_state
					    = ws_session_started;

					if (session->token_base64)
					{
						uint8_t *data = 0;
						size_t data_size
						    = curl_prepare_post_request_data(
							&data, session);
						curl_request_info *request
						    = curl_init_request(session,
							curl_request_type_post,
							data, data_size, 0, 0,
							0);
						free(data);
						curl_request(request);
					}
				}
				else
				{
					curl_request_info *request
					    = curl_init_request(session,
						curl_request_type_get, 0, 0,
						ws_handle_token_reply_json, 0,
						0);
					bool ok = curl_request(request);
					if (!ok)
					{
						return false;
					}
					return true;
				}
			}
			break;
			default:
				break;
		}
	}
	else if (session->session_state == ws_session_started)
	{
		switch (hcode1)
		{
			case ws_in_specialcomb:
			{
				uint32_t *hcode2 = (uint32_t *)msg->msg + 1;
				ws_input_keycomb comb;
				if (!info->backend->callbacks_input->kcomb)
					break;
				if (!validate_msg_size(msg->msg_length - 4,
					sizeof(uint32_t), ws_in_specialcomb))
				{
					return false;
				}
				switch (*hcode2)
				{
					case 0:
						comb
						    = ws_keycomb_ctrlaltdel_press;
						break;
					case 1:
						comb = ws_keycomb_alttab_press;
						break;
					case 2:
						comb
						    = ws_keycomb_alttab_release;
						break;
					default:
						/* this should never happen */
						comb
						    = ws_keycomb_ctrlaltdel_press;
						break;
				}
				if (!info->backend->callbacks_input->kcomb(
					comb, info->backend->backend_internals))
				{
					return false;
				}
			}
			break;
			case ws_in_mouse:
			{
				if (!info->backend->callbacks_input->mouse)
					break;
				typedef struct
				{
					uint32_t op;
					uint32_t flags;
					uint32_t x;
					uint32_t y;
				} wsmsg;
				if (!validate_msg_size(msg->msg_length,
					sizeof(wsmsg), ws_in_mouse))
				{
					return false;
				}
				const wsmsg *m = (const wsmsg *)msg->msg;
				ws_input_mouse mi;
				mi.flags = m->flags;
				mi.x = m->x;
				mi.y = m->y;
				if (!info->backend->callbacks_input->mouse(
					mi, info->backend->backend_internals))
				{
					return false;
				}
			}
			break;
			case ws_in_kupdown:
			{
				if (!info->backend->callbacks_input->kupdown)
					break;
				typedef struct
				{
					uint32_t op;
					uint32_t down;
					uint32_t code;
				} wsmsg;
				if (!validate_msg_size(msg->msg_length,
					sizeof(wsmsg), ws_in_kupdown))
				{
					return false;
				}
				const wsmsg *m = (const wsmsg *)msg->msg;
				ws_input_kupdown mi;
				mi.code = m->code;
				mi.down = m->down;
				if (!info->backend->callbacks_input->kupdown(
					mi, info->backend->backend_internals))
				{
					return false;
				}
			}
			break;
			case ws_in_kpress:
			{
				if (!info->backend->callbacks_input->kpress)
					break;
				typedef struct
				{
					uint32_t op;
					uint32_t shiftstate;
					uint32_t code;
				} wsmsg;
				if (!validate_msg_size(msg->msg_length,
					sizeof(wsmsg), ws_in_kpress))
				{
					return false;
				}
				const wsmsg *m = (const wsmsg *)msg->msg;
				ws_input_kpress mi;
				mi.code = m->code;
				mi.shiftstate = m->shiftstate;
				if (!info->backend->callbacks_input->kpress(
					mi, info->backend->backend_internals))
				{
					return false;
				}
			}
			break;
			case ws_in_unicode:
			{
				if (!info->backend->callbacks_input->unicode)
					break;
				ws_input_unicode mu;
				mu.length = msg->msg_length - 4;
				mu.input = (const uint32_t *)msg->msg + 4;
				if (!info->backend->callbacks_input->unicode(
					mu, info->backend->backend_internals))
				{
					return false;
				}
			}
			break;
			case ws_in_clipbrd_data_request:
			{
				if (!info->backend->callbacks_clipbrd
					 ->request_data)
				{
					const char *msg
					    = "wrdp_backend_cb_clipboard->"
					      "request_data"
					      " not set";
					log_msg((const uint8_t *)msg,
					    strlen(msg), wrdp_log_level_warning,
					    0);
					break;
				}
				if (!validate_msg_size(msg->msg_length - 4,
					sizeof(uint8_t),
					ws_in_clipbrd_data_request))
				{
					return false;
				}
				wrdp_backend_clipbrd_data_request req;
				req.format = *((uint8_t *)(msg->msg + 4));
				if (!info->backend->callbacks_clipbrd
					 ->request_data(&req,
					     info->backend->backend_internals))
				{
					return false;
				}
			}
			break;
			case ws_in_clipbrd_changed:
			{
				if (!info->backend->callbacks_clipbrd
					 ->data_changed)
				{
					const char *msg
					    = "wrdp_backend_cb_clipboard->"
					      "data_changed not set";
					log_msg((const uint8_t *)msg,
					    strlen(msg), wrdp_log_level_warning,
					    0);
					break;
				}
				wrdp_backend_clipbrd_fmts fmts;
				fmts.count = msg->msg_length - 4;
				fmts.formats = (uint8_t *)msg->msg + 4;
				if (!info->backend->callbacks_clipbrd
					 ->data_changed(&fmts,
					     info->backend->backend_internals))
				{
					return false;
				}
			}
			break;
			case ws_in_clipbrd_data:
			{
				if (!info->backend->callbacks_clipbrd
					 ->send_data)
				{
					const char *msg = "wrdp_backend_cb_"
							  "clipboard->send_data"
							  " not set";
					log_msg((const uint8_t *)msg,
					    strlen(msg), wrdp_log_level_warning,
					    0);
					break;
				}
				wrdp_backend_clipbrd_data data;
				data.size = msg->msg_length - 4;
				data.data = (uint8_t *)msg->msg + 4;
				if (!info->backend->callbacks_clipbrd
					 ->send_data(&data,
					     info->backend->backend_internals))
				{
					return false;
				}
			}
			break;
			case ws_in_ft_request:
			{
				if (!info->backend->callbacks_ft->request)
				{
					const char *msg
					    = "wrdp_backend_cb_filetransfer->"
					      "request not set";
					log_msg((const uint8_t *)msg,
					    strlen(msg), wrdp_log_level_warning,
					    0);
					break;
				}
				if ((msg->msg_length - 4) < sizeof(uint16_t))
				{
					const char *msg
					    = "ws_protocol: ws_in_ft_request "
					      "message"
					      " is too small";
					log_msg((const uint8_t *)msg,
					    strlen(msg), wrdp_log_level_error,
					    0);
					return false;
				}
				wrdp_backend_ft_file_request req;
				if (!validate_msg_size(msg->msg_length - 4,
					4 + 8 + 8, ws_in_ft_request))
				{
					return false;
				}
				memcpy(&(req.file_id), msg->msg + 4, 4);
				memcpy(&(req.req_size), msg->msg + 4 + 4, 8);
				memcpy(&(req.file_offset), msg->msg + 4 + 4 + 8,
				    8);
				if (!info->backend->callbacks_ft->request(
					&req, info->backend->backend_internals))
				{
					return false;
				}
			}
			break;
			case ws_in_ft_chunk:
			{
				if (!info->backend->callbacks_ft->chunk)
				{
					const char *msg = "wrdp_backend_cb_"
							  "filetransfer->chunk"
							  " not set";
					log_msg((const uint8_t *)msg,
					    strlen(msg), wrdp_log_level_warning,
					    0);
					break;
				}
				if ((msg->msg_length - 4)
				    < sizeof(wrdp_backend_ft_chunk))
				{
					const char *msg
					    = "ws_protocol: ws_in_ft_chunk "
					      "message"
					      " is too small";
					log_msg((const uint8_t *)msg,
					    strlen(msg), wrdp_log_level_error,
					    0);
					return false;
				}
				const wrdp_backend_ft_chunk *c
				    = (wrdp_backend_ft_chunk *)(msg->msg + 4);
				if (!validate_msg_size(msg->msg_length - 4,
					sizeof(wrdp_backend_ft_chunk) + c->size,
					ws_in_ft_chunk))
				{
					return false;
				}
				const uint8_t *data = (const uint8_t
					*)(msg->msg + 4
					   + sizeof(wrdp_backend_ft_chunk));
				if (!info->backend->callbacks_ft->chunk(c, data,
					info->backend->backend_internals))
				{
					return false;
				}
			}
			break;
			case ws_in_ft_finished:
			{
				if (!info->backend->callbacks_ft->finish)
				{
					const char *msg = "wrdp_backend_cb_"
							  "filetransfer->finish"
							  " not set";
					log_msg((const uint8_t *)msg,
					    strlen(msg), wrdp_log_level_warning,
					    0);
					break;
				}
				if (!validate_msg_size(msg->msg_length - 4,
					sizeof(wrdp_backend_ft_status),
					ws_in_ft_finished))
				{
					return false;
				}
				const wrdp_backend_ft_status *f
				    = (wrdp_backend_ft_status *)(msg->msg + 4);
				if (!info->backend->callbacks_ft->finish(
					f, info->backend->backend_internals))
				{
					return false;
				}
			}
			break;
			default:
			{
				char buf[128];
				snprintf(buf, 127,
				    "protocol error, unsupported message code"
				    " %d",
				    hcode1);
				log_msg((const uint8_t *)buf, strlen(buf),
				    wrdp_log_level_warning, 0);
				return false;
			}
			break;
		}
	}
	return true;
}

static void
ev_con_w_cb(struct ev_loop *loop, ev_io *w, int revents)
{
	ws_session *s = w->data;
	if (wslay_event_want_write(s->wslay_ctx))
	{
		wslay_event_send(s->wslay_ctx);
	}
	if (!wslay_event_want_write(s->wslay_ctx))
	{
		ev_io_stop(loop, w);
	}
}

static void
ws_send(const uint8_t *buf, size_t buf_size, uint8_t opcode, void *_ws_session)
{
	ws_session *session = _ws_session;
	task_info *info = session->task_info;
	wrdp_thpool_task *t = info->wrdp_thpool_task;
	struct wslay_event_msg msgarg;
	if (info->stopped)
	{
		return;
	}
	msgarg.opcode = opcode;
	msgarg.msg = buf;
	msgarg.msg_length = buf_size;
	wslay_event_queue_msg(session->wslay_ctx, &msgarg);
	if (wslay_event_want_write(session->wslay_ctx)
	    && !ev_is_active(&(session->ev_con_fd_w)))
	{
		ev_io *io = &(session->ev_con_fd_w);
		ev_io_init(io, ev_con_w_cb, session->connection_fd, EV_WRITE);
		io->data = session;
		ev_io_start(t->thread->ev_th_loop, io);
	}
}

static void
ws_send_impl(
    const uint8_t *buf, size_t buf_size, void *_task_info, uint8_t type)
{
	task_info *info = _task_info;
	SLIST_HEAD(sessions_head, ws_session_list_entry_s) *sessions_list_head_p
	    = info->backend->sessions_list_head;
	if (!SLIST_EMPTY(sessions_list_head_p))
	{
		for (struct ws_session_list_entry_s *s
		     = SLIST_FIRST(sessions_list_head_p);
		     s; s = SLIST_NEXT(s, entries))
		{
			if (s->session)
				ws_send(buf, buf_size, type, s->session);
		}
	}
}

void
ws_send_text(const uint8_t *buf, size_t buf_size, void *_task_info)
{
	ws_send_impl(buf, buf_size, _task_info, 1);
}

void
ws_send_binary(const uint8_t *buf, size_t buf_size, void *_task_info)
{
	ws_send_impl(buf, buf_size, _task_info, 2);
}

uint8_t *
ws_pack_msg(const uint8_t *buf, size_t buf_size, uint32_t msg_code)
{
	/* TODO: avoid copying data somehow */
	uint8_t *msg = malloc(buf_size + 4);
	if (!msg)
	{
		/* TODO: handle error */
		perror("malloc");
		return 0;
	}
	memcpy(msg, &msg_code, 4);
	if (buf)
	{
		memcpy(msg + 4, buf, buf_size);
	}
	return msg;
}