meshtastic_firmware/src/mesh/Channels.h

#pragma once

#include "CryptoEngine.h"
#include "NodeDB.h"
#include "mesh-pb-constants.h"
#include <Arduino.h>

/** A channel number (index into the channel table)
 */
typedef uint8_t ChannelIndex;

/** A low quality hash of the channel PSK and the channel name.  created by generateHash(chIndex)
 * Used as a hint to limit which PSKs are considered for packet decoding.
 */
typedef uint8_t ChannelHash;

/** The container/on device API for working with channels */
class Channels
{
    /// The index of the primary channel
    ChannelIndex primaryIndex = 0;

    /** The channel index that was requested for sending/receiving.  Note: if this channel is a secondary
    channel and does not have a PSK, we will use the PSK from the primary channel.  If this channel is disabled
    no sending or receiving will be allowed */
    ChannelIndex activeChannelIndex = 0;

    /// the precomputed hashes for each of our channels, or -1 for invalid
    int16_t hashes[MAX_NUM_CHANNELS] = {};

  public:
    Channels() {}

    /// Well known channel names
    static const char *adminChannel, *gpioChannel, *serialChannel, *mqttChannel;

    const meshtastic_ChannelSettings &getPrimary() { return getByIndex(getPrimaryIndex()).settings; }

    /** Return the Channel for a specified index */
    meshtastic_Channel &getByIndex(ChannelIndex chIndex);

    /** Return the Channel for a specified name, return primary if not found. */
    meshtastic_Channel &getByName(const char *chName);

    /** Using the index inside the channel, update the specified channel's settings and role.  If this channel is being promoted
     * to be primary, force all other channels to be secondary.
     */
    void setChannel(const meshtastic_Channel &c);

    /** Return a human friendly name for this channel (and expand any short strings as needed)
     */
    const char *getName(size_t chIndex);

    /**
     * Return a globally unique channel ID usable with MQTT.
     */
    const char *getGlobalId(size_t chIndex) { return getName(chIndex); } // FIXME, not correct

    /** The index of the primary channel */
    ChannelIndex getPrimaryIndex() const { return primaryIndex; }

    ChannelIndex getNumChannels() { return channelFile.channels_count; }

    /// Called by NodeDB on initial boot when the radio config settings are unset.  Set a default single channel config.
    void initDefaults();

    /// called when the user has just changed our radio config and we might need to change channel keys
    void onConfigChanged();

    /** Given a channel hash setup crypto for decoding that channel (or the primary channel if that channel is unsecured)
     *
     * This method is called before decoding inbound packets
     *
     * @return false if the channel hash or channel is invalid
     */
    bool decryptForHash(ChannelIndex chIndex, ChannelHash channelHash);

    /** Given a channel index setup crypto for encoding that channel (or the primary channel if that channel is unsecured)
     *
     * This method is called before encoding outbound packets
     *
     * @eturn the (0 to 255) hash for that channel - if no suitable channel could be found, return -1
     */
    int16_t setActiveByIndex(ChannelIndex channelIndex);

    // Returns true if the channel has the default name and PSK
    bool isDefaultChannel(ChannelIndex chIndex);

    // Returns true if this channel's effective key is publicly decryptable (open or well-known/default PSK).
    bool usesPublicKey(ChannelIndex chIndex);
    // Returns true if the channel is "well known": its PSK is absent or a
    // single-byte well-known key index, AND its name is any modem-preset
    // display name (e.g. a channel named "LongFast" counts even while the
    // radio runs MediumFast). Broader than isDefaultChannel, which only
    // matches the current preset's name and PSK byte 1.
    bool isWellKnownChannel(ChannelIndex chIndex);

    // Returns true if we can be reached via a channel with the default settings given a region and modem preset
    bool hasDefaultChannel();

    // Returns true if any of our channels have enabled MQTT uplink or downlink
    bool anyMqttEnabled();

    bool ensureLicensedOperation();

    bool setDefaultPresetCryptoForHash(ChannelHash channelHash);

    /**
     * Validate a channel, fixing any errors as needed
     */
    meshtastic_Channel &fixupChannel(ChannelIndex chIndex);

    int16_t getHash(ChannelIndex i) { return hashes[i]; }

  private:
    /** Given a channel index, change to use the crypto key specified by that index
     *
     * @eturn the (0 to 255) hash for that channel - if no suitable channel could be found, return -1
     */
    int16_t setCrypto(ChannelIndex chIndex);

    /** Return the channel index for the specified channel hash, or -1 for not found */
    int8_t getIndexByHash(ChannelHash channelHash);

    /** Given a channel number, return the (0 to 255) hash for that channel
     * If no suitable channel could be found, return -1
     *
     * called by fixupChannel when a new channel is set
     */
    int16_t generateHash(ChannelIndex channelNum);

    /**
     * Writes the default lora config
     */
    void initDefaultLoraConfig();

    /**
     * Write default channels defined in UserPrefs
     */
    void initDefaultChannel(ChannelIndex chIndex);

    /**
     * Return the key used for encrypting this channel (if channel is secondary and no key provided, use the primary channel's
     * PSK)
     */
    CryptoKey getKey(ChannelIndex chIndex);
};

/// Singleton channel table
extern Channels channels;

/// 16 bytes of random PSK for our _public_ default channel that all devices power up on (AES128)
static const uint8_t defaultpsk[] = {0xd4, 0xf1, 0xbb, 0x3a, 0x20, 0x29, 0x07, 0x59,
                                     0xf0, 0xbc, 0xff, 0xab, 0xcf, 0x4e, 0x69, 0x01};

/// True if a getKey()-resolved key offers no privacy: length 0 (off) or the public defaultpsk family. Pure; for tests.
bool cryptoKeyIsPublic(const CryptoKey &key);

static const uint8_t eventpsk[] = {0x38, 0x4b, 0xbc, 0xc0, 0x1d, 0xc0, 0x22, 0xd1, 0x81, 0xbf, 0x36,
                                   0xb8, 0x61, 0x21, 0xe1, 0xfb, 0x96, 0xb7, 0x2e, 0x55, 0xbf, 0x74,
                                   0x22, 0x7e, 0x9d, 0x6a, 0xfb, 0x48, 0xd6, 0x4c, 0xb1, 0xa1};