src/mobilebackup2.c - third_party/libimobiledevice - Git at Google

 /*
  * mobilebackup2.c
  * Contains functions for the built-in MobileBackup2 client (iOS4+ only)
  *
  * Copyright (c) 2010-2019 Nikias Bassen, All Rights Reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
  * License as published by the Free Software Foundation; either
  * version 2.1 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Lesser General Public License for more details.
  *
  * You should have received a copy of the GNU Lesser General Public
  * License along with this library; if not, write to the Free Software
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
  */

 #ifdef HAVE_CONFIG_H
 #include <config.h>
 #endif
 #include <plist/plist.h>
 #include <string.h>
 #include <stdlib.h>

 #include "mobilebackup2.h"
 #include "device_link_service.h"
 #include "common/debug.h"

 #define MBACKUP2_VERSION_INT1 400
 #define MBACKUP2_VERSION_INT2 0

 #define IS_FLAG_SET(x, y) (((x) & (y)) == (y))

 /**
  * Convert an device_link_service_error_t value to an mobilebackup2_error_t value.
  * Used internally to get correct error codes from the underlying
  * device_link_service.
  *
  * @param err An device_link_service_error_t error code
  *
  * @return A matching mobilebackup2_error_t error code,
  *     MOBILEBACKUP2_E_UNKNOWN_ERROR otherwise.
  */
 static mobilebackup2_error_t mobilebackup2_error(device_link_service_error_t err)
 {
 	switch (err) {
 		case DEVICE_LINK_SERVICE_E_SUCCESS:
 			return MOBILEBACKUP2_E_SUCCESS;
 		case DEVICE_LINK_SERVICE_E_INVALID_ARG:
 			return MOBILEBACKUP2_E_INVALID_ARG;
 		case DEVICE_LINK_SERVICE_E_PLIST_ERROR:
 			return MOBILEBACKUP2_E_PLIST_ERROR;
 		case DEVICE_LINK_SERVICE_E_MUX_ERROR:
 			return MOBILEBACKUP2_E_MUX_ERROR;
 		case DEVICE_LINK_SERVICE_E_SSL_ERROR:
 			return MOBILEBACKUP2_E_SSL_ERROR;
 		case DEVICE_LINK_SERVICE_E_RECEIVE_TIMEOUT:
 			return MOBILEBACKUP2_E_RECEIVE_TIMEOUT;
 		case DEVICE_LINK_SERVICE_E_BAD_VERSION:
 			return MOBILEBACKUP2_E_BAD_VERSION;
 		default:
 			break;
 	}
 	return MOBILEBACKUP2_E_UNKNOWN_ERROR;
 }

 mobilebackup2_error_t mobilebackup2_client_new(idevice_t device, lockdownd_service_descriptor_t service,
 						mobilebackup2_client_t * client)
 {
 	if (!device || !service || service->port == 0 || !client || *client)
 		return MOBILEBACKUP2_E_INVALID_ARG;

 	device_link_service_client_t dlclient = NULL;
 	mobilebackup2_error_t ret = mobilebackup2_error(device_link_service_client_new(device, service, &dlclient));
 	if (ret != MOBILEBACKUP2_E_SUCCESS) {
 		return ret;
 	}

 	mobilebackup2_client_t client_loc = (mobilebackup2_client_t) malloc(sizeof(struct mobilebackup2_client_private));
 	client_loc->parent = dlclient;

 	/* perform handshake */
 	ret = mobilebackup2_error(device_link_service_version_exchange(dlclient, MBACKUP2_VERSION_INT1, MBACKUP2_VERSION_INT2));
 	if (ret != MOBILEBACKUP2_E_SUCCESS) {
 		debug_info("version exchange failed, error %d", ret);
 		mobilebackup2_client_free(client_loc);
 		return ret;
 	}

 	*client = client_loc;

 	return ret;
 }

 mobilebackup2_error_t mobilebackup2_client_start_service(idevice_t device, mobilebackup2_client_t * client, const char* label)
 {
 	mobilebackup2_error_t err = MOBILEBACKUP2_E_UNKNOWN_ERROR;
 	service_client_factory_start_service(device, MOBILEBACKUP2_SERVICE_NAME, (void**)client, label, SERVICE_CONSTRUCTOR(mobilebackup2_client_new), &err);
 	return err;
 }

 mobilebackup2_error_t mobilebackup2_client_free(mobilebackup2_client_t client)
 {
 	if (!client)
 		return MOBILEBACKUP2_E_INVALID_ARG;
 	mobilebackup2_error_t err = MOBILEBACKUP2_E_SUCCESS;
 	if (client->parent) {
 		device_link_service_disconnect(client->parent, NULL);
 		err = mobilebackup2_error(device_link_service_client_free(client->parent));
 	}
 	free(client);
 	return err;
 }

 mobilebackup2_error_t mobilebackup2_send_message(mobilebackup2_client_t client, const char *message, plist_t options)
 {
 	if (!client || !client->parent || (!message && !options))
 		return MOBILEBACKUP2_E_INVALID_ARG;

 	if (options && (plist_get_node_type(options) != PLIST_DICT)) {
 		return MOBILEBACKUP2_E_INVALID_ARG;
 	}

 	mobilebackup2_error_t err;

 	if (message) {
 		plist_t dict = NULL;
 		if (options) {
 			dict = plist_copy(options);
 		} else {
 			dict = plist_new_dict();
 		}
 		plist_dict_set_item(dict, "MessageName", plist_new_string(message));

 		/* send it as DLMessageProcessMessage */
 		err = mobilebackup2_error(device_link_service_send_process_message(client->parent, dict));
 		plist_free(dict);
 	} else {
 		err = mobilebackup2_error(device_link_service_send_process_message(client->parent, options));
 	}
 	if (err != MOBILEBACKUP2_E_SUCCESS) {
 		debug_info("ERROR: Could not send message '%s' (%d)!", message, err);
 	}
 	return err;
 }

 /**
  * Receives a plist from the device and checks if the value for the
  * MessageName key matches the value passed in the message parameter.
  *
  * @param client The connected MobileBackup client to use.
  * @param message The expected message to check.
  * @param result Pointer to a plist_t that will be set to the received plist
  *    for further processing. The caller has to free it using plist_free().
  *    Note that it will be set to NULL if the operation itself fails due to
  *    a communication or plist error.
  *    If this parameter is NULL, it will be ignored.
  *
  * @return MOBILEBACKUP2_E_SUCCESS on success, MOBILEBACKUP2_E_INVALID_ARG if
  *    client or message is invalid, MOBILEBACKUP2_E_REPLY_NOT_OK if the
  *    expected message could not be received, MOBILEBACKUP2_E_PLIST_ERROR if
  *    the received message is not a valid backup message plist (i.e. the
  *    MessageName key is not present), or MOBILEBACKUP2_E_MUX_ERROR
  *    if a communication error occurs.
  */
 static mobilebackup2_error_t internal_mobilebackup2_receive_message(mobilebackup2_client_t client, const char *message, plist_t *result)
 {
 	if (!client || !client->parent || !message)
 		return MOBILEBACKUP2_E_INVALID_ARG;

 	if (result)
 		*result = NULL;
 	mobilebackup2_error_t err;

 	plist_t dict = NULL;

 	/* receive DLMessageProcessMessage */
 	err = mobilebackup2_error(device_link_service_receive_process_message(client->parent, &dict));
 	if (err != MOBILEBACKUP2_E_SUCCESS) {
 		goto leave;
 	}

 	plist_t node = plist_dict_get_item(dict, "MessageName");
 	if (!node) {
 		debug_info("ERROR: MessageName key not found in plist!");
 		err = MOBILEBACKUP2_E_PLIST_ERROR;
 		goto leave;
 	}

 	char *str = NULL;
 	plist_get_string_val(node, &str);
 	if (str && (strcmp(str, message) == 0)) {
 		err = MOBILEBACKUP2_E_SUCCESS;
 	} else {
 		debug_info("ERROR: MessageName value does not match '%s'!", message);
 		err = MOBILEBACKUP2_E_REPLY_NOT_OK;
 	}
 	if (str)
 		free(str);

 	if (result) {
 		*result = dict;
 		dict = NULL;
 	}
 leave:
 	if (dict) {
 		plist_free(dict);
 	}

 	return err;
 }

 mobilebackup2_error_t mobilebackup2_receive_message(mobilebackup2_client_t client, plist_t *msg_plist, char **dlmessage)
 {
 	return mobilebackup2_error(device_link_service_receive_message(client->parent, msg_plist, dlmessage));
 }

 mobilebackup2_error_t mobilebackup2_send_raw(mobilebackup2_client_t client, const char *data, uint32_t length, uint32_t *bytes)
 {
 	if (!client || !client->parent || !data || (length == 0) || !bytes)
 		return MOBILEBACKUP2_E_INVALID_ARG;

 	*bytes = 0;

 	service_client_t raw = client->parent->parent->parent;

 	int bytes_loc = 0;
 	uint32_t sent = 0;
 	do {
 		bytes_loc = 0;
 		service_send(raw, data+sent, length-sent, (uint32_t*)&bytes_loc);
 		if (bytes_loc <= 0)
 			break;
 		sent += bytes_loc;
 	} while (sent < length);
 	if (sent > 0) {
 		*bytes = sent;
 		return MOBILEBACKUP2_E_SUCCESS;
 	}
 	return MOBILEBACKUP2_E_MUX_ERROR;
 }

 mobilebackup2_error_t mobilebackup2_receive_raw(mobilebackup2_client_t client, char *data, uint32_t length, uint32_t *bytes)
 {
 	if (!client || !client->parent || !data || (length == 0) || !bytes)
 		return MOBILEBACKUP2_E_INVALID_ARG;

 	service_client_t raw = client->parent->parent->parent;

 	*bytes = 0;

 	int bytes_loc = 0;
 	uint32_t received = 0;
 	do {
 		bytes_loc = 0;
 		service_receive(raw, data+received, length-received, (uint32_t*)&bytes_loc);
 		if (bytes_loc <= 0) break;
 		received += bytes_loc;
 	} while (received < length);
 	if (received > 0) {
 		*bytes = received;
 		return MOBILEBACKUP2_E_SUCCESS;
 	}
 	if (received == 0) {
 		return MOBILEBACKUP2_E_SUCCESS;
 	}
 	return MOBILEBACKUP2_E_MUX_ERROR;
 }

 mobilebackup2_error_t mobilebackup2_version_exchange(mobilebackup2_client_t client, double local_versions[], char count, double *remote_version)
 {
 	int i;

 	if (!client || !client->parent)
 		return MOBILEBACKUP2_E_INVALID_ARG;

 	plist_t dict = plist_new_dict();
 	plist_t array = plist_new_array();
 	for (i = 0; i < count; i++) {
 		plist_array_append_item(array, plist_new_real(local_versions[i]));
 	}
 	plist_dict_set_item(dict, "SupportedProtocolVersions", array);

 	mobilebackup2_error_t err = mobilebackup2_send_message(client, "Hello", dict);
 	plist_free(dict);

 	if (err != MOBILEBACKUP2_E_SUCCESS)
 		goto leave;

 	dict = NULL;
 	err = internal_mobilebackup2_receive_message(client, "Response", &dict);
 	if (err != MOBILEBACKUP2_E_SUCCESS)
 		goto leave;

 	/* check if we received an error */
 	plist_t node = plist_dict_get_item(dict, "ErrorCode");
 	if (!node || (plist_get_node_type(node) != PLIST_UINT)) {
 		err = MOBILEBACKUP2_E_PLIST_ERROR;
 		goto leave;
 	}

 	uint64_t val = 0;
 	plist_get_uint_val(node, &val);
 	if (val != 0) {
 		if (val == 1) {
 			err = MOBILEBACKUP2_E_NO_COMMON_VERSION;
 		} else {
 			err = MOBILEBACKUP2_E_REPLY_NOT_OK;
 		}
 		goto leave;
 	}

 	/* retrieve the protocol version of the device */
 	node = plist_dict_get_item(dict, "ProtocolVersion");
 	if (!node || (plist_get_node_type(node) != PLIST_REAL)) {
 		err = MOBILEBACKUP2_E_PLIST_ERROR;
 		goto leave;
 	}

 	*remote_version = 0.0;
 	plist_get_real_val(node, remote_version);
 leave:
 	if (dict)
 		plist_free(dict);
 	return err;
 }

 mobilebackup2_error_t mobilebackup2_send_request(mobilebackup2_client_t client, const char *request, const char *target_identifier, const char *source_identifier, plist_t options)
 {
 	if (!client || !client->parent || !request || !target_identifier)
 		return MOBILEBACKUP2_E_INVALID_ARG;

 	plist_t dict = plist_new_dict();
 	plist_dict_set_item(dict, "TargetIdentifier", plist_new_string(target_identifier));
 	if (source_identifier) {
 		plist_dict_set_item(dict, "SourceIdentifier", plist_new_string(source_identifier));
 	}
 	if (options) {
 		plist_dict_set_item(dict, "Options", plist_copy(options));
 	}
 	if (!strcmp(request, "Unback") && options) {
 		plist_t node = plist_dict_get_item(options, "Password");
 		if (node) {
 			plist_dict_set_item(dict, "Password", plist_copy(node));
 		}
 	}
 	if (!strcmp(request, "EnableCloudBackup") && options) {
 		plist_t node = plist_dict_get_item(options, "CloudBackupState");
 		if (node) {
 			plist_dict_set_item(dict, "CloudBackupState", plist_copy(node));
 		}
 	}
 	mobilebackup2_error_t err = mobilebackup2_send_message(client, request, dict);
 	plist_free(dict);

 	return err;
 }

 mobilebackup2_error_t mobilebackup2_send_status_response(mobilebackup2_client_t client, int status_code, const char *status1, plist_t status2)
 {
 	if (!client || !client->parent)
 		return MOBILEBACKUP2_E_INVALID_ARG;

 	plist_t array = plist_new_array();
 	plist_array_append_item(array, plist_new_string("DLMessageStatusResponse"));
 	plist_array_append_item(array, plist_new_uint(status_code));
 	if (status1) {
 		plist_array_append_item(array, plist_new_string(status1));
 	} else {
 		plist_array_append_item(array, plist_new_string("___EmptyParameterString___"));
 	}
 	if (status2) {
 		plist_array_append_item(array, plist_copy(status2));
 	} else {
 		plist_array_append_item(array, plist_new_string("___EmptyParameterString___"));
 	}

 	mobilebackup2_error_t err = mobilebackup2_error(device_link_service_send(client->parent, array));
 	plist_free(array);

 	return err;
 }
	/*
	* mobilebackup2.c
	* Contains functions for the built-in MobileBackup2 client (iOS4+ only)
	*
	* Copyright (c) 2010-2019 Nikias Bassen, All Rights Reserved.
	*
	* This library is free software; you can redistribute it and/or
	* modify it under the terms of the GNU Lesser General Public
	* License as published by the Free Software Foundation; either
	* version 2.1 of the License, or (at your option) any later version.
	*
	* This library is distributed in the hope that it will be useful,
	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
	* Lesser General Public License for more details.
	*
	* You should have received a copy of the GNU Lesser General Public
	* License along with this library; if not, write to the Free Software
	* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
	*/

	#ifdef HAVE_CONFIG_H
	#include <config.h>
	#endif
	#include <plist/plist.h>
	#include <string.h>
	#include <stdlib.h>

	#include "mobilebackup2.h"
	#include "device_link_service.h"
	#include "common/debug.h"

	#define MBACKUP2_VERSION_INT1 400
	#define MBACKUP2_VERSION_INT2 0

	#define IS_FLAG_SET(x, y) (((x) & (y)) == (y))

	/**
	* Convert an device_link_service_error_t value to an mobilebackup2_error_t value.
	* Used internally to get correct error codes from the underlying
	* device_link_service.
	*
	* @param err An device_link_service_error_t error code
	*
	* @return A matching mobilebackup2_error_t error code,
	* MOBILEBACKUP2_E_UNKNOWN_ERROR otherwise.
	*/
	static mobilebackup2_error_t mobilebackup2_error(device_link_service_error_t err)
	{
	switch (err) {
	case DEVICE_LINK_SERVICE_E_SUCCESS:
	return MOBILEBACKUP2_E_SUCCESS;
	case DEVICE_LINK_SERVICE_E_INVALID_ARG:
	return MOBILEBACKUP2_E_INVALID_ARG;
	case DEVICE_LINK_SERVICE_E_PLIST_ERROR:
	return MOBILEBACKUP2_E_PLIST_ERROR;
	case DEVICE_LINK_SERVICE_E_MUX_ERROR:
	return MOBILEBACKUP2_E_MUX_ERROR;
	case DEVICE_LINK_SERVICE_E_SSL_ERROR:
	return MOBILEBACKUP2_E_SSL_ERROR;
	case DEVICE_LINK_SERVICE_E_RECEIVE_TIMEOUT:
	return MOBILEBACKUP2_E_RECEIVE_TIMEOUT;
	case DEVICE_LINK_SERVICE_E_BAD_VERSION:
	return MOBILEBACKUP2_E_BAD_VERSION;
	default:
	break;
	}
	return MOBILEBACKUP2_E_UNKNOWN_ERROR;
	}

	mobilebackup2_error_t mobilebackup2_client_new(idevice_t device, lockdownd_service_descriptor_t service,
	mobilebackup2_client_t * client)
	{
	if (!device \|\| !service \|\| service->port == 0 \|\| !client \|\| *client)
	return MOBILEBACKUP2_E_INVALID_ARG;

	device_link_service_client_t dlclient = NULL;
	mobilebackup2_error_t ret = mobilebackup2_error(device_link_service_client_new(device, service, &dlclient));
	if (ret != MOBILEBACKUP2_E_SUCCESS) {
	return ret;
	}

	mobilebackup2_client_t client_loc = (mobilebackup2_client_t) malloc(sizeof(struct mobilebackup2_client_private));
	client_loc->parent = dlclient;

	/* perform handshake */
	ret = mobilebackup2_error(device_link_service_version_exchange(dlclient, MBACKUP2_VERSION_INT1, MBACKUP2_VERSION_INT2));
	if (ret != MOBILEBACKUP2_E_SUCCESS) {
	debug_info("version exchange failed, error %d", ret);
	mobilebackup2_client_free(client_loc);
	return ret;
	}

	*client = client_loc;

	return ret;
	}

	mobilebackup2_error_t mobilebackup2_client_start_service(idevice_t device, mobilebackup2_client_t * client, const char* label)
	{
	mobilebackup2_error_t err = MOBILEBACKUP2_E_UNKNOWN_ERROR;
	service_client_factory_start_service(device, MOBILEBACKUP2_SERVICE_NAME, (void**)client, label, SERVICE_CONSTRUCTOR(mobilebackup2_client_new), &err);
	return err;
	}

	mobilebackup2_error_t mobilebackup2_client_free(mobilebackup2_client_t client)
	{
	if (!client)
	return MOBILEBACKUP2_E_INVALID_ARG;
	mobilebackup2_error_t err = MOBILEBACKUP2_E_SUCCESS;
	if (client->parent) {
	device_link_service_disconnect(client->parent, NULL);
	err = mobilebackup2_error(device_link_service_client_free(client->parent));
	}
	free(client);
	return err;
	}

	mobilebackup2_error_t mobilebackup2_send_message(mobilebackup2_client_t client, const char *message, plist_t options)
	{
	if (!client \|\| !client->parent \|\| (!message && !options))
	return MOBILEBACKUP2_E_INVALID_ARG;

	if (options && (plist_get_node_type(options) != PLIST_DICT)) {
	return MOBILEBACKUP2_E_INVALID_ARG;
	}

	mobilebackup2_error_t err;

	if (message) {
	plist_t dict = NULL;
	if (options) {
	dict = plist_copy(options);
	} else {
	dict = plist_new_dict();
	}
	plist_dict_set_item(dict, "MessageName", plist_new_string(message));

	/* send it as DLMessageProcessMessage */
	err = mobilebackup2_error(device_link_service_send_process_message(client->parent, dict));
	plist_free(dict);
	} else {
	err = mobilebackup2_error(device_link_service_send_process_message(client->parent, options));
	}
	if (err != MOBILEBACKUP2_E_SUCCESS) {
	debug_info("ERROR: Could not send message '%s' (%d)!", message, err);
	}
	return err;
	}

	/**
	* Receives a plist from the device and checks if the value for the
	* MessageName key matches the value passed in the message parameter.
	*
	* @param client The connected MobileBackup client to use.
	* @param message The expected message to check.
	* @param result Pointer to a plist_t that will be set to the received plist
	* for further processing. The caller has to free it using plist_free().
	* Note that it will be set to NULL if the operation itself fails due to
	* a communication or plist error.
	* If this parameter is NULL, it will be ignored.
	*
	* @return MOBILEBACKUP2_E_SUCCESS on success, MOBILEBACKUP2_E_INVALID_ARG if
	* client or message is invalid, MOBILEBACKUP2_E_REPLY_NOT_OK if the
	* expected message could not be received, MOBILEBACKUP2_E_PLIST_ERROR if
	* the received message is not a valid backup message plist (i.e. the
	* MessageName key is not present), or MOBILEBACKUP2_E_MUX_ERROR
	* if a communication error occurs.
	*/
	static mobilebackup2_error_t internal_mobilebackup2_receive_message(mobilebackup2_client_t client, const char message, plist_t result)
	{
	if (!client \|\| !client->parent \|\| !message)
	return MOBILEBACKUP2_E_INVALID_ARG;

	if (result)
	*result = NULL;
	mobilebackup2_error_t err;

	plist_t dict = NULL;

	/* receive DLMessageProcessMessage */
	err = mobilebackup2_error(device_link_service_receive_process_message(client->parent, &dict));
	if (err != MOBILEBACKUP2_E_SUCCESS) {
	goto leave;
	}

	plist_t node = plist_dict_get_item(dict, "MessageName");
	if (!node) {
	debug_info("ERROR: MessageName key not found in plist!");
	err = MOBILEBACKUP2_E_PLIST_ERROR;
	goto leave;
	}

	char *str = NULL;
	plist_get_string_val(node, &str);
	if (str && (strcmp(str, message) == 0)) {
	err = MOBILEBACKUP2_E_SUCCESS;
	} else {
	debug_info("ERROR: MessageName value does not match '%s'!", message);
	err = MOBILEBACKUP2_E_REPLY_NOT_OK;
	}
	if (str)
	free(str);

	if (result) {
	*result = dict;
	dict = NULL;
	}
	leave:
	if (dict) {
	plist_free(dict);
	}

	return err;
	}

	mobilebackup2_error_t mobilebackup2_receive_message(mobilebackup2_client_t client, plist_t msg_plist, char *dlmessage)
	{
	return mobilebackup2_error(device_link_service_receive_message(client->parent, msg_plist, dlmessage));
	}

	mobilebackup2_error_t mobilebackup2_send_raw(mobilebackup2_client_t client, const char data, uint32_t length, uint32_t bytes)
	{
	if (!client \|\| !client->parent \|\| !data \|\| (length == 0) \|\| !bytes)
	return MOBILEBACKUP2_E_INVALID_ARG;

	*bytes = 0;

	service_client_t raw = client->parent->parent->parent;

	int bytes_loc = 0;
	uint32_t sent = 0;
	do {
	bytes_loc = 0;
	service_send(raw, data+sent, length-sent, (uint32_t*)&bytes_loc);
	if (bytes_loc <= 0)
	break;
	sent += bytes_loc;
	} while (sent < length);
	if (sent > 0) {
	*bytes = sent;
	return MOBILEBACKUP2_E_SUCCESS;
	}
	return MOBILEBACKUP2_E_MUX_ERROR;
	}

	mobilebackup2_error_t mobilebackup2_receive_raw(mobilebackup2_client_t client, char data, uint32_t length, uint32_t bytes)
	{
	if (!client \|\| !client->parent \|\| !data \|\| (length == 0) \|\| !bytes)
	return MOBILEBACKUP2_E_INVALID_ARG;

	service_client_t raw = client->parent->parent->parent;

	*bytes = 0;

	int bytes_loc = 0;
	uint32_t received = 0;
	do {
	bytes_loc = 0;
	service_receive(raw, data+received, length-received, (uint32_t*)&bytes_loc);
	if (bytes_loc <= 0) break;
	received += bytes_loc;
	} while (received < length);
	if (received > 0) {
	*bytes = received;
	return MOBILEBACKUP2_E_SUCCESS;
	}
	if (received == 0) {
	return MOBILEBACKUP2_E_SUCCESS;
	}
	return MOBILEBACKUP2_E_MUX_ERROR;
	}

	mobilebackup2_error_t mobilebackup2_version_exchange(mobilebackup2_client_t client, double local_versions[], char count, double *remote_version)
	{
	int i;

	if (!client \|\| !client->parent)
	return MOBILEBACKUP2_E_INVALID_ARG;

	plist_t dict = plist_new_dict();
	plist_t array = plist_new_array();
	for (i = 0; i < count; i++) {
	plist_array_append_item(array, plist_new_real(local_versions[i]));
	}
	plist_dict_set_item(dict, "SupportedProtocolVersions", array);

	mobilebackup2_error_t err = mobilebackup2_send_message(client, "Hello", dict);
	plist_free(dict);

	if (err != MOBILEBACKUP2_E_SUCCESS)
	goto leave;

	dict = NULL;
	err = internal_mobilebackup2_receive_message(client, "Response", &dict);
	if (err != MOBILEBACKUP2_E_SUCCESS)
	goto leave;

	/* check if we received an error */
	plist_t node = plist_dict_get_item(dict, "ErrorCode");
	if (!node \|\| (plist_get_node_type(node) != PLIST_UINT)) {
	err = MOBILEBACKUP2_E_PLIST_ERROR;
	goto leave;
	}

	uint64_t val = 0;
	plist_get_uint_val(node, &val);
	if (val != 0) {
	if (val == 1) {
	err = MOBILEBACKUP2_E_NO_COMMON_VERSION;
	} else {
	err = MOBILEBACKUP2_E_REPLY_NOT_OK;
	}
	goto leave;
	}

	/* retrieve the protocol version of the device */
	node = plist_dict_get_item(dict, "ProtocolVersion");
	if (!node \|\| (plist_get_node_type(node) != PLIST_REAL)) {
	err = MOBILEBACKUP2_E_PLIST_ERROR;
	goto leave;
	}

	*remote_version = 0.0;
	plist_get_real_val(node, remote_version);
	leave:
	if (dict)
	plist_free(dict);
	return err;
	}

	mobilebackup2_error_t mobilebackup2_send_request(mobilebackup2_client_t client, const char request, const char target_identifier, const char *source_identifier, plist_t options)
	{
	if (!client \|\| !client->parent \|\| !request \|\| !target_identifier)
	return MOBILEBACKUP2_E_INVALID_ARG;

	plist_t dict = plist_new_dict();
	plist_dict_set_item(dict, "TargetIdentifier", plist_new_string(target_identifier));
	if (source_identifier) {
	plist_dict_set_item(dict, "SourceIdentifier", plist_new_string(source_identifier));
	}
	if (options) {
	plist_dict_set_item(dict, "Options", plist_copy(options));
	}
	if (!strcmp(request, "Unback") && options) {
	plist_t node = plist_dict_get_item(options, "Password");
	if (node) {
	plist_dict_set_item(dict, "Password", plist_copy(node));
	}
	}
	if (!strcmp(request, "EnableCloudBackup") && options) {
	plist_t node = plist_dict_get_item(options, "CloudBackupState");
	if (node) {
	plist_dict_set_item(dict, "CloudBackupState", plist_copy(node));
	}
	}
	mobilebackup2_error_t err = mobilebackup2_send_message(client, request, dict);
	plist_free(dict);

	return err;
	}

	mobilebackup2_error_t mobilebackup2_send_status_response(mobilebackup2_client_t client, int status_code, const char *status1, plist_t status2)
	{
	if (!client \|\| !client->parent)
	return MOBILEBACKUP2_E_INVALID_ARG;

	plist_t array = plist_new_array();
	plist_array_append_item(array, plist_new_string("DLMessageStatusResponse"));
	plist_array_append_item(array, plist_new_uint(status_code));
	if (status1) {
	plist_array_append_item(array, plist_new_string(status1));
	} else {
	plist_array_append_item(array, plist_new_string("___EmptyParameterString___"));
	}
	if (status2) {
	plist_array_append_item(array, plist_copy(status2));
	} else {
	plist_array_append_item(array, plist_new_string("___EmptyParameterString___"));
	}

	mobilebackup2_error_t err = mobilebackup2_error(device_link_service_send(client->parent, array));
	plist_free(array);

	return err;
	}