feat(protocol): add THP encoding/decoding logic

- only one message exchange is supported ThpCreateChannelRequest > ThpCreateChannelResponse
- without cryptography module. will be added in the next commit

Author: szymonlesisz

packages/protocol/src/protocol-thp/ThpState.ts

@@ -1,13 +1,25 @@
-import { ThpCredentials, ThpDeviceProperties } from './messages';
+import { ThpCredentials, ThpDeviceProperties, ThpMessageSyncBit } from './messages';
 
 export type ThpStateSerialized = {
     properties?: ThpDeviceProperties;
     credentials: ThpCredentials[];
+    channel: string; // 2 bytes as hex
+    sendBit: ThpMessageSyncBit; // host synchronization bit
+    recvBit: ThpMessageSyncBit; // device synchronization bit
+    sendNonce: number; // host nonce
+    recvNonce: number; // device nonce
+    expectedResponses: number[]; // expected responses from the device
 };
 
 export class ThpState {
     private _properties?: ThpDeviceProperties;
     private _pairingCredentials: ThpCredentials[] = [];
+    private _channel: Buffer = Buffer.alloc(0);
+    private _sendBit: ThpMessageSyncBit = 0;
+    private _sendNonce: number = 0;
+    private _recvBit: ThpMessageSyncBit = 0;
+    private _recvNonce: number = 1;
+    private _expectedResponses: number[] = [];
 
     get properties() {
         return this._properties;
@@ -29,10 +41,110 @@ export class ThpState {
         }
     }
 
+    get channel() {
+        return this._channel;
+    }
+
+    setChannel(channel: Buffer) {
+        this._channel = channel;
+    }
+
+    get sendBit() {
+        return this._sendBit;
+    }
+
+    get sendNonce() {
+        return this._sendNonce;
+    }
+
+    get recvBit() {
+        return this._recvBit;
+    }
+
+    get recvNonce() {
+        return this._recvNonce;
+    }
+
+    updateSyncBit(type: 'send' | 'recv') {
+        if (type === 'send') {
+            this._sendBit = this._sendBit > 0 ? 0 : 1;
+        } else {
+            this._recvBit = this._recvBit > 0 ? 0 : 1;
+        }
+    }
+
+    updateNonce(type: 'send' | 'recv') {
+        if (type === 'send') {
+            this._sendNonce += 1;
+        } else {
+            this._recvNonce += 1;
+        }
+    }
+
     serialize(): ThpStateSerialized {
         return {
             properties: this._properties,
+            channel: this.channel.toString('hex'),
+            sendBit: this.sendBit,
+            recvBit: this.recvBit,
+            sendNonce: this.sendNonce,
+            recvNonce: this.recvNonce,
+            expectedResponses: this._expectedResponses,
             credentials: this._pairingCredentials,
         };
     }
+
+    deserialize(json: ReturnType<(typeof this)['serialize']>) {
+        // simple fields validation
+        const error = new Error('ThpState.deserialize invalid state');
+        if (!json || typeof json !== 'object') {
+            throw error;
+        }
+        if (!Array.isArray(json.expectedResponses)) {
+            throw error;
+        }
+        if (typeof json.channel !== 'string') {
+            throw error;
+        }
+        [
+            json.sendBit,
+            json.recvBit,
+            json.sendNonce,
+            json.recvNonce,
+            ...json.expectedResponses,
+        ].forEach(nr => {
+            if (typeof nr !== 'number') {
+                throw error;
+            }
+        });
+
+        this._channel = Buffer.from(json.channel, 'hex');
+        this._expectedResponses = json.expectedResponses;
+        this._sendBit = json.sendBit;
+        this._recvBit = json.recvBit;
+        this._sendNonce = json.sendNonce;
+        this._recvNonce = json.recvNonce;
+    }
+
+    get expectedResponses() {
+        return this._expectedResponses;
+    }
+
+    setExpectedResponses(expected: number[]) {
+        this._expectedResponses = expected;
+    }
+
+    resetState() {
+        this._channel = Buffer.alloc(0);
+        this._sendBit = 0;
+        this._sendNonce = 0;
+        this._recvBit = 0;
+        this._recvNonce = 1;
+        this._expectedResponses = [];
+        this._pairingCredentials = [];
+    }
+
+    toString() {
+        return JSON.stringify(this.serialize());
+    }
 }

packages/protocol/src/protocol-thp/constants.ts

@@ -0,0 +1,16 @@
+export const THP_CREATE_CHANNEL_REQUEST = 0x40;
+export const THP_CREATE_CHANNEL_RESPONSE = 0x41;
+export const THP_HANDSHAKE_INIT_REQUEST = 0x00;
+export const THP_HANDSHAKE_INIT_RESPONSE = 0x01;
+export const THP_HANDSHAKE_COMPLETION_REQUEST = 0x02;
+export const THP_HANDSHAKE_COMPLETION_RESPONSE = 0x03;
+export const THP_ERROR_HEADER_BYTE = 0x42;
+export const THP_READ_ACK_HEADER_BYTE = 0x20; // [0x20, 0x30];
+export const THP_CONTROL_BYTE_ENCRYPTED = 0x04; // [0x04, 0x14];
+export const THP_CONTROL_BYTE_DECRYPTED = 0x05; // [0x05, 0x15];
+export const THP_CONTINUATION_PACKET = 0x80;
+
+export const THP_DEFAULT_CHANNEL = Buffer.from([0xff, 0xff]);
+
+export const CRC_LENGTH = 4;
+export const TAG_LENGTH = 16;

packages/protocol/src/protocol-thp/crypto/crc32.ts

@@ -0,0 +1,63 @@
+// inspired by
+// https://github.com/brianloveswords/buffer-crc32/blob/master/index.js
+// optimized by
+// https://stackoverflow.com/a/18639975
+
+// we don't want to have dependency in @trezor/protocol package + our implementation is simpler and faster
+
+const getCrcTable = () =>
+    new Int32Array([
+        0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419, 0x706af48f, 0xe963a535,
+        0x9e6495a3, 0x0edb8832, 0x79dcb8a4, 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd,
+        0xe7b82d07, 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de, 0x1adad47d,
+        0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856, 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec,
+        0x14015c4f, 0x63066cd9, 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
+        0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b, 0x35b5a8fa, 0x42b2986c,
+        0xdbbbc9d6, 0xacbcf940, 0x32d86ce3, 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac,
+        0x51de003a, 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599, 0xb8bda50f,
+        0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924, 0x2f6f7c87, 0x58684c11, 0xc1611dab,
+        0xb6662d3d, 0x76dc4190, 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
+        0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e, 0xe10e9818, 0x7f6a0dbb,
+        0x086d3d2d, 0x91646c97, 0xe6635c01, 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e,
+        0x6c0695ed, 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950, 0x8bbeb8ea,
+        0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3, 0xfbd44c65, 0x4db26158, 0x3ab551ce,
+        0xa3bc0074, 0xd4bb30e2, 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
+        0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5, 0xaa0a4c5f, 0xdd0d7cc9,
+        0x5005713c, 0x270241aa, 0xbe0b1010, 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409,
+        0xce61e49f, 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17, 0x2eb40d81,
+        0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6, 0x03b6e20c, 0x74b1d29a, 0xead54739,
+        0x9dd277af, 0x04db2615, 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
+        0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344, 0x8708a3d2, 0x1e01f268,
+        0x6906c2fe, 0xf762575d, 0x806567cb, 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0,
+        0x10da7a5a, 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5, 0xd6d6a3e8,
+        0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1, 0xa6bc5767, 0x3fb506dd, 0x48b2364b,
+        0xd80d2bda, 0xaf0a1b4c, 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
+        0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236, 0xcc0c7795, 0xbb0b4703,
+        0x220216b9, 0x5505262f, 0xc5ba3bbe, 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7,
+        0xb5d0cf31, 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c, 0x026d930a,
+        0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713, 0x95bf4a82, 0xe2b87a14, 0x7bb12bae,
+        0x0cb61b38, 0x92d28e9b, 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
+        0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1, 0x18b74777, 0x88085ae6,
+        0xff0f6a70, 0x66063bca, 0x11010b5c, 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45,
+        0xa00ae278, 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7, 0x4969474d,
+        0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66, 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5,
+        0x47b2cf7f, 0x30b5ffe9, 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
+        0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8, 0x5d681b02, 0x2a6f2b94,
+        0xb40bbe37, 0xc30c8ea1, 0x5a05df1b, 0x2d02ef8d,
+    ]);
+
+export const crc32 = (buf: Buffer): Buffer => {
+    if (!Buffer.isBuffer(buf)) {
+        throw new Error('Invalid crc input');
+    }
+
+    const table = getCrcTable();
+    let crc = -1;
+    for (let i = 0; i < buf.length; i++) {
+        crc = table[(crc ^ buf[i]) & 0xff] ^ (crc >>> 8);
+    }
+    const buffer = Buffer.alloc(4);
+    buffer.writeInt32BE(crc ^ -1, 0);
+
+    return buffer;
+};

packages/protocol/src/protocol-thp/decode.ts

@@ -0,0 +1,173 @@
+import { ThpState } from './ThpState';
+import {
+    CRC_LENGTH,
+    THP_CREATE_CHANNEL_RESPONSE,
+    THP_ERROR_HEADER_BYTE,
+    THP_READ_ACK_HEADER_BYTE,
+} from './constants';
+import { TransportProtocolDecode } from '../types';
+import { crc32 } from './crypto/crc32';
+import { ThpError, ThpMessageResponse } from './messages';
+import { clearControlBit, readThpHeader } from './utils';
+
+type ThpMessage = ReturnType<TransportProtocolDecode> & {
+    magic: number;
+    thpState: ThpState;
+};
+
+// @trezor/protobuf decodeMessage without direct reference to protobuf root
+type ProtobufDecoder = (
+    messageType: string | number,
+    payload: Buffer,
+) => {
+    type: string;
+    message: Record<string, unknown>;
+};
+
+type MessageV2 = ReturnType<TransportProtocolDecode>;
+
+// TODO: link-to-public-docs
+// https://www.notion.so/satoshilabs/THP-Specification-2-0-18fdc5260606806ab573d0a7cba1897a
+// example: 41ffff0020639ba57ff4e0c2343c830a0454335731180220002802280328042801c0171551
+// [magic | channel | len* | nonce               | protobuf: messageType + message          | crc     ]
+// [41    | ffff    | 0020 | 639ba57ff4e0c234    | 3c830a0454335731180220002802280328042801 | c0171551]
+// *len includes nonce+protobuf+crc
+const createChannelResponse = (
+    { payload }: ThpMessage,
+    protobufDecoder: ProtobufDecoder,
+): ThpMessageResponse => {
+    const nonce = payload.subarray(0, 8);
+    const channel = payload.subarray(8, 10);
+    const props = payload.subarray(10, payload.length - CRC_LENGTH);
+    const properties = protobufDecoder('ThpDeviceProperties', props).message;
+    // TODO: add-crypto
+    // const handshakeHash = handleCreateChannelResponse(props);
+
+    return {
+        type: 'ThpCreateChannelResponse',
+        message: {
+            nonce,
+            channel,
+            properties,
+            // TODO: add-crypto
+            // handshakeHash,
+        },
+    } as any;
+};
+
+const decodeReadAck = (): ThpMessageResponse => ({
+    type: 'ThpAck',
+    message: {},
+});
+
+// TODO: link-to-public-docs
+// https://www.notion.so/satoshilabs/THP-Specification-2-0-18fdc5260606806ab573d0a7cba1897a
+// example: 42122200050270303cfa
+// [magic | channel | len* | error | crc     ]
+// [42    | 1222    | 0005 | 02    | 70303cfa]
+// *len includes error+crc
+const decodeThpError = (payload: Buffer): ThpMessageResponse => {
+    const [errorType] = payload;
+
+    const error = (() => {
+        switch (errorType) {
+            case 0x01:
+                return 'ThpTransportBusy';
+            case 0x02:
+                return 'ThpUnallocatedChannel';
+            case 0x03:
+                return 'ThpDecryptionFailed';
+            case 0x04:
+                return 'ThpInvalidData';
+            case 0x05:
+                return 'ThpDeviceLocked';
+            default:
+                return 'ThpUnknownError';
+        }
+    })();
+
+    const message: ThpError = {
+        code: error,
+        message: error ?? `Unknown ThpError ${errorType}`,
+    };
+
+    return {
+        type: 'ThpError',
+        message,
+    };
+};
+
+const validateCrc = (decodedMessage: ReturnType<TransportProtocolDecode>) => {
+    // payload length without crc
+    const payloadLen = decodedMessage.length - CRC_LENGTH;
+    const length = Buffer.alloc(2);
+    length.writeUInt16BE(decodedMessage.length);
+    // build crc locally
+    const expectedCrc = crc32(
+        Buffer.concat([
+            decodedMessage.header,
+            length,
+            decodedMessage.payload.subarray(0, payloadLen),
+        ]),
+    );
+    // get crc from the message
+    const crc = decodedMessage.payload.subarray(payloadLen, decodedMessage.length);
+
+    // compare both crc
+    if (expectedCrc.compare(crc) !== 0) {
+        throw new Error(
+            `Invalid CRC. expected: ${expectedCrc.toString('hex')} received: ${crc.toString('hex')}`,
+        );
+    }
+};
+
+// Decode protocol-v2 message from thp send process: ThpAck or ThpError
+export const decodeSendAck = (decodedMessage: MessageV2) => {
+    validateCrc(decodedMessage);
+
+    const header = readThpHeader(decodedMessage.header);
+    const magic = clearControlBit(header.magic);
+    if (magic === THP_ERROR_HEADER_BYTE) {
+        return decodeThpError(decodedMessage.payload);
+    }
+    if (magic === THP_READ_ACK_HEADER_BYTE) {
+        return decodeReadAck();
+    }
+
+    throw new Error('Unexpected send response: ' + magic);
+};
+
+// Decode protocol-v2 message from thp receive process
+export const decode = (
+    decodedMessage: MessageV2,
+    protobufDecoder: ProtobufDecoder,
+    thpState?: ThpState,
+): ThpMessageResponse => {
+    if (!thpState) {
+        throw new Error('Cannot decode THP message without ThpState');
+    }
+
+    validateCrc(decodedMessage);
+
+    const header = readThpHeader(decodedMessage.header);
+    const message: ThpMessage = {
+        ...decodedMessage,
+        ...header,
+        thpState,
+    };
+
+    const magic = clearControlBit(message.magic);
+    if (magic === THP_ERROR_HEADER_BYTE) {
+        return decodeThpError(message.payload);
+    }
+
+    if (magic === THP_READ_ACK_HEADER_BYTE) {
+        return decodeReadAck();
+    }
+
+    if (magic === THP_CREATE_CHANNEL_RESPONSE) {
+        return createChannelResponse(message, protobufDecoder);
+    }
+
+    throw new Error('Unknown message type: ' + magic);
+};