SecurityManager

/* mbed Microcontroller Library
 * Copyright (c) 2006-2013 ARM Limited
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include <events/mbed_events.h>
#include "ble/BLE.h"
#include "mbed-os-ble-utils/pretty_printer.h"

#if MBED_CONF_APP_FILESYSTEM_SUPPORT
#include "LittleFileSystem.h"
#include "HeapBlockDevice.h"
#endif //MBED_CONF_APP_FILESYSTEM_SUPPORT

/** This example demonstrates all the basic setup required for pairing and setting
 *  up link security both as a central and peripheral. It also demonstrates privacy
 *  features in Gap. It shows how to use private addresses when advertising and
 *  connecting and how filtering ties in with these operations.
 *
 *  The application will start by repeatedly trying to connect to the same
 *  application running on another board. It will do this by advertising and
 *  scanning for random intervals waiting until the difference in intervals
 *  between the boards will make them meet when one is advertising and the
 *  other scanning.
 *
 *  Two devices will be operating using random resolvable addresses. The
 *  applications will connect to the peer and pair. It will attempt bonding
 *  to store the IRK that resolve the peer. Subsequent connections will
 *  turn on filtering based on stored IRKs.
 */

static const char DEVICE_NAME[] = "SecurityDemo";

using std::literals::chrono_literals::operator""ms;

/* Delay between steps */
static const std::chrono::milliseconds delay = 3000ms;

/** Base class for both peripheral and central. The same class that provides
 *  the logic for the application also implements the SecurityManagerEventHandler
 *  which is the interface used by the Security Manager to communicate events
 *  back to the applications. You can provide overrides for a selection of events
 *  your application is interested in.
 */
class SecurityDemo : private mbed::NonCopyable<SecurityDemo>,
                     public SecurityManager::EventHandler,
                     public ble::Gap::EventHandler
{
public:
    SecurityDemo(BLE &ble, events::EventQueue &event_queue) :
        _ble(ble), _event_queue(event_queue) { };

    virtual ~SecurityDemo()
    {
        _ble.onEventsToProcess(nullptr);
    };

    /** Start BLE interface initialisation */
    void run()
    {
        /* this will inform us off all events so we can schedule their handling
         * using our event queue */
        _ble.onEventsToProcess(makeFunctionPointer(this, &SecurityDemo::schedule_ble_events));

        /* handle gap events */
        _ble.gap().setEventHandler(this);

        if (_ble.hasInitialized()) {
            /* ble instance already initialised, skip init and start activity */
            start();
        } else {
            ble_error_t error = _ble.init(this, &SecurityDemo::on_init_complete);

            if (error) {
                print_error(error, "Error returned by BLE::init.\r\n");
                return;
            }
        }

        /* this will not return until shutdown */
        _event_queue.dispatch_forever();
    };

    /** Override to start chosen activity when the system starts */
    virtual void start() = 0;

    /* callbacks */

    /** This is called when BLE interface is initialised and starts the demonstration */
    void on_init_complete(BLE::InitializationCompleteCallbackContext *event)
    {
        ble_error_t error;

        if (event->error) {
            printf("Error during the initialisation\r\n");
            return;
        }

        /* for use by tools we print out own address and also use it
         * to seed RNG as the address is unique */
        print_local_address();


		/* This path will be used to store bonding information but will fallback
         * to storing in memory if file access fails (for example due to lack of a filesystem) */
        const char* db_path = "/fs/bt_sec_db";

        error = _ble.securityManager().init(
            /* enableBonding */ true,
            /* requireMITM */ false,
            /* iocaps */ SecurityManager::IO_CAPS_NONE,
            /* passkey */ nullptr,
            /* signing */ false,
            /* dbFilepath */ db_path
        );

        if (error) {
            print_error(error, "Error during initialising security manager\r\n");
            return;
        }

        /* This tells the stack to generate a pairingRequest event which will require
         * this application to respond before pairing can proceed. Setting it to false
         * will automatically accept pairing. */
        _ble.securityManager().setPairingRequestAuthorisation(true);

#if MBED_CONF_APP_FILESYSTEM_SUPPORT
        error = _ble.securityManager().preserveBondingStateOnReset(true);

        if (error) {
            print_error(error, "Error during preserveBondingStateOnReset %d\r\n");
        }
#endif // MBED_CONF_APP_FILESYSTEM_SUPPORT

        /* this demo switches between being master and slave */
        _ble.securityManager().setHintFutureRoleReversal(true);

        /* Tell the security manager to use methods in this class to inform us
         * of any events. Class needs to implement SecurityManagerEventHandler. */
        _ble.securityManager().setSecurityManagerEventHandler(this);

        /* gap events also handled by this class */
        _ble.gap().setEventHandler(this);

        error = _ble.gap().enablePrivacy(true);
        if (error) {
            print_error(error, "Error enabling privacy.\r\n");
            return;
        }

        /* continuation is in onPrivacyEnabled() */
    };

    /** Schedule processing of events from the BLE in the event queue. */
    void schedule_ble_events(BLE::OnEventsToProcessCallbackContext *context)
    {
        _event_queue.call([&ble_instance = context->ble] { ble_instance.processEvents(); });
    };

private:
    /* SecurityManager Event handler */

    /** Respond to a pairing request. This will be called by the stack
     * when a pairing request arrives and expects the application to
     * call acceptPairingRequest or cancelPairingRequest */
    void pairingRequest(ble::connection_handle_t connectionHandle) override
    {
        printf("Pairing requested - authorising\r\n");
        _ble.securityManager().acceptPairingRequest(connectionHandle);
    }

    /** Inform the application of pairing */
    void pairingResult(
        ble::connection_handle_t connectionHandle,
        SecurityManager::SecurityCompletionStatus_t result
    ) override
    {
        if (result == SecurityManager::SEC_STATUS_SUCCESS) {
            printf("Pairing successful\r\n");
            _bonded = true;
        } else {
            printf("Pairing failed\r\n");
        }

        _event_queue.call_in(
            delay,
            [this, connectionHandle] {
                _ble.gap().disconnect(connectionHandle, ble::local_disconnection_reason_t::USER_TERMINATION);
            }
        );
    }

    /** Inform the application of change in encryption status. This will be
      * communicated through the serial port */
    void linkEncryptionResult(ble::connection_handle_t connectionHandle, ble::link_encryption_t result) override
    {
        if (result == ble::link_encryption_t::ENCRYPTED) {
            printf("Link ENCRYPTED\r\n");
        } else if (result == ble::link_encryption_t::ENCRYPTED_WITH_MITM) {
            printf("Link ENCRYPTED_WITH_MITM\r\n");
        } else if (result == ble::link_encryption_t::NOT_ENCRYPTED) {
            printf("Link NOT_ENCRYPTED\r\n");
        }
    }

    void onPrivacyEnabled() override
    {
        /* all initialisation complete, start our main activity */
        start();
    }

    /* Gap Event handler */

    /** This is called by Gap to notify the application we connected */
    void onConnectionComplete(const ble::ConnectionCompleteEvent &event) override
    {
        printf("Connected to peer: ");
        print_address(event.getPeerAddress().data());
        if (event.getPeerResolvablePrivateAddress() != ble::address_t()) {
            printf("Peer random resolvable address: ");
            print_address(event.getPeerResolvablePrivateAddress().data());
        }

        _handle = event.getConnectionHandle();

        if (_bonded) {
            /* disconnect in 2s */
            _event_queue.call_in(
                delay,
                [this] {
                    _ble.gap().disconnect(_handle, ble::local_disconnection_reason_t::USER_TERMINATION);
                }
            );
        } else {
            /* start bonding */
            ble_error_t error = _ble.securityManager().setLinkSecurity(
                _handle,
                SecurityManager::SECURITY_MODE_ENCRYPTION_NO_MITM
            );
            if (error) {
                print_error(error, "Failed to set link security\r\n");
                _ble.gap().disconnect(_handle, ble::local_disconnection_reason_t::USER_TERMINATION);
            }
        }
    };

    /** This is called by Gap to notify the application we disconnected */
    void onDisconnectionComplete(const ble::DisconnectionCompleteEvent &event) override
    {
        if (_bonded) {
            /* we have connected to and bonded with the other device, from now
             * on we will use the second start function and stay in the same role
             * as peripheral or central */
            printf("Disconnected.\r\n\r\n");
            _event_queue.call_in(delay, [this] { start(); });
        } else {
            printf("Failed to bond.\r\n");
            _event_queue.break_dispatch();
        }
    };

    void onScanTimeout(const ble::ScanTimeoutEvent &) override
    {
        /* if we failed to find the other device, abort so that we change roles */
        printf("Haven't seen other device, switch modes.\r\n");
        _event_queue.break_dispatch();
    }

    void onAdvertisingEnd(const ble::AdvertisingEndEvent &event) override
    {
        if (!event.isConnected()) {
            printf("No device connected to us, switch modes.\r\n");
            _event_queue.break_dispatch();
        }
    }

private:
    void print_local_address()
    {
        /* show what address we are using now */
        ble::own_address_type_t addr_type;
        ble::address_t addr;
        _ble.gap().getAddress(addr_type, addr);
        printf("Device address: ");
        print_address(addr);
        static bool _seeded = false;
        if (!_seeded) {
            _seeded = true;
            /* use the address as a seed */
            uint8_t* random_data = addr.data();
            srand(*((unsigned int*)random_data));
        }
    }

protected:
    BLE &_ble;
    events::EventQueue &_event_queue;
    ble::connection_handle_t _handle = 0;
    bool _bonded = false;
};

/** A peripheral device will advertise and accept the connections */
class SecurityPeripheral : public SecurityDemo {
public:
    SecurityPeripheral(BLE &ble, events::EventQueue &event_queue)
        : SecurityDemo(ble, event_queue) { }

    /** Set up and start advertising accepting anyone */
    void start() override
    {
        ble::peripheral_privacy_configuration_t privacy_configuration = {
            /* use_non_resolvable_random_address */ false,
            ble::peripheral_privacy_configuration_t::PERFORM_PAIRING_PROCEDURE
        };

        if (_bonded) {
            /** advertise and filter based on known devices */
            printf("We are bonded, we will only accept known devices\r\n");
            privacy_configuration.resolution_strategy =
                ble::peripheral_privacy_configuration_t::REJECT_NON_RESOLVED_ADDRESS;
        }

        _ble.gap().setPeripheralPrivacyConfiguration(&privacy_configuration);

        start_advertising();
    };

private:
    void start_advertising()
    {
        uint8_t adv_buffer[ble::LEGACY_ADVERTISING_MAX_SIZE];
        /* use the helper to build the payload */
        ble::AdvertisingDataBuilder adv_data_builder(adv_buffer);

        adv_data_builder.setFlags();
        adv_data_builder.setName(DEVICE_NAME);

        /* Set payload for the set */
        ble_error_t error = _ble.gap().setAdvertisingPayload(
            ble::LEGACY_ADVERTISING_HANDLE,
            adv_data_builder.getAdvertisingData()
        );

        if (error) {
            print_error(error, "Gap::setAdvertisingPayload() failed");
            return;
        }

        ble::AdvertisingParameters adv_parameters(
            ble::advertising_type_t::CONNECTABLE_UNDIRECTED
        );

        error = _ble.gap().setAdvertisingParameters(ble::LEGACY_ADVERTISING_HANDLE, adv_parameters);

        if (error) {
            print_error(error, "Gap::setAdvertisingParameters() failed");
            return;
        }

        if (_bonded) {
            /* if we bonded it means we have found the other device, from now on
             * wait at each step until completion */
            error = _ble.gap().startAdvertising(ble::LEGACY_ADVERTISING_HANDLE);
        } else {
            /* since we have two boards which might start running this example at the same time
             * we randomise the interval of advertising to have them meet when one is advertising
             * and the other one is scanning (we use their random address as source of randomness) */
            ble::millisecond_t random_duration_ms((5 + rand() % 6) * 1000);
            ble::adv_duration_t random_duration(random_duration_ms);

            error = _ble.gap().startAdvertising(ble::LEGACY_ADVERTISING_HANDLE, random_duration);
        }

        if (error) {
            print_error(error, "Gap::startAdvertising() failed");
            return;
        }

        printf("Advertising...\r\n");
    }

};

/** A central device will scan and connect to a peer. */
class SecurityCentral : public SecurityDemo {
public:
    SecurityCentral(BLE &ble, events::EventQueue &event_queue)
        : SecurityDemo(ble, event_queue) { }

    /** start scanning and attach a callback that will handle advertisements
     *  and scan requests responses */
    void start() override
    {
        ble::central_privacy_configuration_t privacy_configuration = {
            /* use_non_resolvable_random_address */ false,
            ble::central_privacy_configuration_t::DO_NOT_RESOLVE
        };
        if (_bonded) {
            printf("We are bonded - we will only see known devices\r\n");
            privacy_configuration.resolution_strategy = ble::central_privacy_configuration_t::RESOLVE_AND_FILTER;
        }

        _ble.gap().setCentralPrivacyConfiguration(&privacy_configuration);

        start_scanning();
    }

    /* helper functions */
private:
    bool start_scanning()
    {
        ble_error_t error;
        ble::ScanParameters scan_params;
        _ble.gap().setScanParameters(scan_params);

        _is_connecting = false;

        if (_bonded) {
            /* if we bonded it means we have found the other device, from now on
             * wait at each step until completion */
            error = _ble.gap().startScan(ble::scan_duration_t::forever());
        } else {
            /* otherwise only scan for a limited time before changing roles again
             * if we fail to find the other device */
            error = _ble.gap().startScan(ble::scan_duration_t(ble::millisecond_t(5000)));
        }

        if (error) {
            print_error(error, "Error during Gap::startScan\r\n");
            return false;
        }

        printf("Scanning...\r\n");

        return true;
    }

private:
    /* Event handler */

    /** Look at scan payload to find a peer device and connect to it */
    void onAdvertisingReport(const ble::AdvertisingReportEvent &event) override
    {
        /* don't bother with analysing scan result if we're already connecting */
        if (_is_connecting) {
            return;
        }

        ble::AdvertisingDataParser adv_data(event.getPayload());

        /* parse the advertising payload, looking for a discoverable device */
        while (adv_data.hasNext()) {
            ble::AdvertisingDataParser::element_t field = adv_data.next();

            /* connect to a known device by name */
            if (field.type == ble::adv_data_type_t::COMPLETE_LOCAL_NAME &&
                field.value.size() == strlen(DEVICE_NAME) &&
                (memcmp(field.value.data(), DEVICE_NAME, field.value.size()) == 0)) {

                printf("We found a connectable device: \r\n");
                print_address(event.getPeerAddress().data());

                ble_error_t error = _ble.gap().stopScan();

                if (error) {
                    print_error(error, "Error caused by Gap::stopScan");
                    return;
                }

                error = _ble.gap().connect(
                    event.getPeerAddressType(),
                    event.getPeerAddress(),
                    ble::ConnectionParameters()
                );

                printf("Connecting...\r\n");

                if (error) {
                    print_error(error, "Error caused by Gap::connect");
                    return;
                }

                /* we may have already scan events waiting
                 * to be processed so we need to remember
                 * that we are already connecting and ignore them */
                _is_connecting = true;

                return;
            }
        }
    }

private:
    bool _is_connecting = false;
};

#if MBED_CONF_APP_FILESYSTEM_SUPPORT
bool create_filesystem()
{
    static LittleFileSystem fs("fs");

    /* replace this with any physical block device your board supports (like an SD card) */
    static HeapBlockDevice bd(4096, 256);

    int err = bd.init();

    if (err) {
        return false;
    }

    err = bd.erase(0, bd.size());

    if (err) {
        return false;
    }

    err = fs.mount(&bd);

    if (err) {
        /* Reformat if we can't mount the filesystem */
        printf("No filesystem found, formatting...\r\n");

        err = fs.reformat(&bd);

        if (err) {
            return false;
        }
    }

    return true;
}
#endif //MBED_CONF_APP_FILESYSTEM_SUPPORT

int main()
{
    BLE& ble = BLE::Instance();
    events::EventQueue queue;

#if MBED_CONF_APP_FILESYSTEM_SUPPORT
    /* if filesystem creation fails or there is no filesystem the security manager
     * will fallback to storing the security database in memory */
    if (!create_filesystem()) {
        printf("Filesystem creation failed, will use memory storage\r\n");
    }
#endif

    while(true) {
        {
            printf("\r\n * Device is a peripheral *\r\n\r\n");
            SecurityPeripheral peripheral(ble, queue);
            peripheral.run();
        }
        {
            printf("\r\n * Device is a central *\r\n\r\n");
            SecurityCentral central(ble, queue);
            central.run();
        }
    }

    return 0;
}