Skip to content

Commit b33b491

Browse files
committed
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
1 parent c883e60 commit b33b491

File tree

12 files changed

+1009
-2
lines changed

12 files changed

+1009
-2
lines changed

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

Lines changed: 113 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -1,13 +1,25 @@
1-
import { ThpCredentials, ThpDeviceProperties } from './messages';
1+
import { ThpCredentials, ThpDeviceProperties, ThpMessageSyncBit } from './messages';
22

33
export type ThpStateSerialized = {
44
properties?: ThpDeviceProperties;
55
credentials: ThpCredentials[];
6+
channel: string; // 2 bytes as hex
7+
sendBit: ThpMessageSyncBit; // host synchronization bit
8+
recvBit: ThpMessageSyncBit; // device synchronization bit
9+
sendNonce: number; // host nonce
10+
recvNonce: number; // device nonce
11+
expectedResponses: number[]; // expected responses from the device
612
};
713

814
export class ThpState {
915
private _properties?: ThpDeviceProperties;
1016
private _pairingCredentials: ThpCredentials[] = [];
17+
private _channel: Buffer = Buffer.alloc(0);
18+
private _sendBit: ThpMessageSyncBit = 0;
19+
private _sendNonce: number = 0;
20+
private _recvBit: ThpMessageSyncBit = 0;
21+
private _recvNonce: number = 1;
22+
private _expectedResponses: number[] = [];
1123

1224
get properties() {
1325
return this._properties;
@@ -29,10 +41,110 @@ export class ThpState {
2941
}
3042
}
3143

44+
get channel() {
45+
return this._channel;
46+
}
47+
48+
setChannel(channel: Buffer) {
49+
this._channel = channel;
50+
}
51+
52+
get sendBit() {
53+
return this._sendBit;
54+
}
55+
56+
get sendNonce() {
57+
return this._sendNonce;
58+
}
59+
60+
get recvBit() {
61+
return this._recvBit;
62+
}
63+
64+
get recvNonce() {
65+
return this._recvNonce;
66+
}
67+
68+
updateSyncBit(type: 'send' | 'recv') {
69+
if (type === 'send') {
70+
this._sendBit = this._sendBit > 0 ? 0 : 1;
71+
} else {
72+
this._recvBit = this._recvBit > 0 ? 0 : 1;
73+
}
74+
}
75+
76+
updateNonce(type: 'send' | 'recv') {
77+
if (type === 'send') {
78+
this._sendNonce += 1;
79+
} else {
80+
this._recvNonce += 1;
81+
}
82+
}
83+
3284
serialize(): ThpStateSerialized {
3385
return {
3486
properties: this._properties,
87+
channel: this.channel.toString('hex'),
88+
sendBit: this.sendBit,
89+
recvBit: this.recvBit,
90+
sendNonce: this.sendNonce,
91+
recvNonce: this.recvNonce,
92+
expectedResponses: this._expectedResponses,
3593
credentials: this._pairingCredentials,
3694
};
3795
}
96+
97+
deserialize(json: ReturnType<(typeof this)['serialize']>) {
98+
// simple fields validation
99+
const error = new Error('ThpState.deserialize invalid state');
100+
if (!json || typeof json !== 'object') {
101+
throw error;
102+
}
103+
if (!Array.isArray(json.expectedResponses)) {
104+
throw error;
105+
}
106+
if (typeof json.channel !== 'string') {
107+
throw error;
108+
}
109+
[
110+
json.sendBit,
111+
json.recvBit,
112+
json.sendNonce,
113+
json.recvNonce,
114+
...json.expectedResponses,
115+
].forEach(nr => {
116+
if (typeof nr !== 'number') {
117+
throw error;
118+
}
119+
});
120+
121+
this._channel = Buffer.from(json.channel, 'hex');
122+
this._expectedResponses = json.expectedResponses;
123+
this._sendBit = json.sendBit;
124+
this._recvBit = json.recvBit;
125+
this._sendNonce = json.sendNonce;
126+
this._recvNonce = json.recvNonce;
127+
}
128+
129+
get expectedResponses() {
130+
return this._expectedResponses;
131+
}
132+
133+
setExpectedResponses(expected: number[]) {
134+
this._expectedResponses = expected;
135+
}
136+
137+
resetState() {
138+
this._channel = Buffer.alloc(0);
139+
this._sendBit = 0;
140+
this._sendNonce = 0;
141+
this._recvBit = 0;
142+
this._recvNonce = 1;
143+
this._expectedResponses = [];
144+
this._pairingCredentials = [];
145+
}
146+
147+
toString() {
148+
return JSON.stringify(this.serialize());
149+
}
38150
}
Lines changed: 16 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,16 @@
1+
export const THP_CREATE_CHANNEL_REQUEST = 0x40;
2+
export const THP_CREATE_CHANNEL_RESPONSE = 0x41;
3+
export const THP_HANDSHAKE_INIT_REQUEST = 0x00;
4+
export const THP_HANDSHAKE_INIT_RESPONSE = 0x01;
5+
export const THP_HANDSHAKE_COMPLETION_REQUEST = 0x02;
6+
export const THP_HANDSHAKE_COMPLETION_RESPONSE = 0x03;
7+
export const THP_ERROR_HEADER_BYTE = 0x42;
8+
export const THP_READ_ACK_HEADER_BYTE = 0x20; // [0x20, 0x30];
9+
export const THP_CONTROL_BYTE_ENCRYPTED = 0x04; // [0x04, 0x14];
10+
export const THP_CONTROL_BYTE_DECRYPTED = 0x05; // [0x05, 0x15];
11+
export const THP_CONTINUATION_PACKET = 0x80;
12+
13+
export const THP_DEFAULT_CHANNEL = Buffer.from([0xff, 0xff]);
14+
15+
export const CRC_LENGTH = 4;
16+
export const TAG_LENGTH = 16;
Lines changed: 63 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,63 @@
1+
// inspired by
2+
// https://github.com/brianloveswords/buffer-crc32/blob/master/index.js
3+
// optimized by
4+
// https://stackoverflow.com/a/18639975
5+
6+
// we don't want to have dependency in @trezor/protocol package + our implementation is simpler and faster
7+
8+
const getCrcTable = () =>
9+
new Int32Array([
10+
0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419, 0x706af48f, 0xe963a535,
11+
0x9e6495a3, 0x0edb8832, 0x79dcb8a4, 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd,
12+
0xe7b82d07, 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de, 0x1adad47d,
13+
0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856, 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec,
14+
0x14015c4f, 0x63066cd9, 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
15+
0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b, 0x35b5a8fa, 0x42b2986c,
16+
0xdbbbc9d6, 0xacbcf940, 0x32d86ce3, 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac,
17+
0x51de003a, 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599, 0xb8bda50f,
18+
0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924, 0x2f6f7c87, 0x58684c11, 0xc1611dab,
19+
0xb6662d3d, 0x76dc4190, 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
20+
0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e, 0xe10e9818, 0x7f6a0dbb,
21+
0x086d3d2d, 0x91646c97, 0xe6635c01, 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e,
22+
0x6c0695ed, 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950, 0x8bbeb8ea,
23+
0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3, 0xfbd44c65, 0x4db26158, 0x3ab551ce,
24+
0xa3bc0074, 0xd4bb30e2, 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
25+
0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5, 0xaa0a4c5f, 0xdd0d7cc9,
26+
0x5005713c, 0x270241aa, 0xbe0b1010, 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409,
27+
0xce61e49f, 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17, 0x2eb40d81,
28+
0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6, 0x03b6e20c, 0x74b1d29a, 0xead54739,
29+
0x9dd277af, 0x04db2615, 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
30+
0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344, 0x8708a3d2, 0x1e01f268,
31+
0x6906c2fe, 0xf762575d, 0x806567cb, 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0,
32+
0x10da7a5a, 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5, 0xd6d6a3e8,
33+
0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1, 0xa6bc5767, 0x3fb506dd, 0x48b2364b,
34+
0xd80d2bda, 0xaf0a1b4c, 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
35+
0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236, 0xcc0c7795, 0xbb0b4703,
36+
0x220216b9, 0x5505262f, 0xc5ba3bbe, 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7,
37+
0xb5d0cf31, 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c, 0x026d930a,
38+
0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713, 0x95bf4a82, 0xe2b87a14, 0x7bb12bae,
39+
0x0cb61b38, 0x92d28e9b, 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
40+
0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1, 0x18b74777, 0x88085ae6,
41+
0xff0f6a70, 0x66063bca, 0x11010b5c, 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45,
42+
0xa00ae278, 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7, 0x4969474d,
43+
0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66, 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5,
44+
0x47b2cf7f, 0x30b5ffe9, 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
45+
0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8, 0x5d681b02, 0x2a6f2b94,
46+
0xb40bbe37, 0xc30c8ea1, 0x5a05df1b, 0x2d02ef8d,
47+
]);
48+
49+
export const crc32 = (buf: Buffer): Buffer => {
50+
if (!Buffer.isBuffer(buf)) {
51+
throw new Error('Invalid crc input');
52+
}
53+
54+
const table = getCrcTable();
55+
let crc = -1;
56+
for (let i = 0; i < buf.length; i++) {
57+
crc = table[(crc ^ buf[i]) & 0xff] ^ (crc >>> 8);
58+
}
59+
const buffer = Buffer.alloc(4);
60+
buffer.writeInt32BE(crc ^ -1, 0);
61+
62+
return buffer;
63+
};
Lines changed: 173 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,173 @@
1+
import { ThpState } from './ThpState';
2+
import {
3+
CRC_LENGTH,
4+
THP_CREATE_CHANNEL_RESPONSE,
5+
THP_ERROR_HEADER_BYTE,
6+
THP_READ_ACK_HEADER_BYTE,
7+
} from './constants';
8+
import { TransportProtocolDecode } from '../types';
9+
import { crc32 } from './crypto/crc32';
10+
import { ThpError, ThpMessageResponse } from './messages';
11+
import { clearControlBit, readThpHeader } from './utils';
12+
13+
type ThpMessage = ReturnType<TransportProtocolDecode> & {
14+
magic: number;
15+
thpState: ThpState;
16+
};
17+
18+
// @trezor/protobuf decodeMessage without direct reference to protobuf root
19+
type ProtobufDecoder = (
20+
messageType: string | number,
21+
payload: Buffer,
22+
) => {
23+
type: string;
24+
message: Record<string, unknown>;
25+
};
26+
27+
type MessageV2 = ReturnType<TransportProtocolDecode>;
28+
29+
// TODO: link-to-public-docs
30+
// https://www.notion.so/satoshilabs/THP-Specification-2-0-18fdc5260606806ab573d0a7cba1897a
31+
// example: 41ffff0020639ba57ff4e0c2343c830a0454335731180220002802280328042801c0171551
32+
// [magic | channel | len* | nonce | protobuf: messageType + message | crc ]
33+
// [41 | ffff | 0020 | 639ba57ff4e0c234 | 3c830a0454335731180220002802280328042801 | c0171551]
34+
// *len includes nonce+protobuf+crc
35+
const createChannelResponse = (
36+
{ payload }: ThpMessage,
37+
protobufDecoder: ProtobufDecoder,
38+
): ThpMessageResponse => {
39+
const nonce = payload.subarray(0, 8);
40+
const channel = payload.subarray(8, 10);
41+
const props = payload.subarray(10, payload.length - CRC_LENGTH);
42+
const properties = protobufDecoder('ThpDeviceProperties', props).message;
43+
// TODO: add-crypto
44+
// const handshakeHash = handleCreateChannelResponse(props);
45+
46+
return {
47+
type: 'ThpCreateChannelResponse',
48+
message: {
49+
nonce,
50+
channel,
51+
properties,
52+
// TODO: add-crypto
53+
// handshakeHash,
54+
},
55+
} as any;
56+
};
57+
58+
const decodeReadAck = (): ThpMessageResponse => ({
59+
type: 'ThpAck',
60+
message: {},
61+
});
62+
63+
// TODO: link-to-public-docs
64+
// https://www.notion.so/satoshilabs/THP-Specification-2-0-18fdc5260606806ab573d0a7cba1897a
65+
// example: 42122200050270303cfa
66+
// [magic | channel | len* | error | crc ]
67+
// [42 | 1222 | 0005 | 02 | 70303cfa]
68+
// *len includes error+crc
69+
const decodeThpError = (payload: Buffer): ThpMessageResponse => {
70+
const [errorType] = payload;
71+
72+
const error = (() => {
73+
switch (errorType) {
74+
case 0x01:
75+
return 'ThpTransportBusy';
76+
case 0x02:
77+
return 'ThpUnallocatedChannel';
78+
case 0x03:
79+
return 'ThpDecryptionFailed';
80+
case 0x04:
81+
return 'ThpInvalidData';
82+
case 0x05:
83+
return 'ThpDeviceLocked';
84+
default:
85+
return 'ThpUnknownError';
86+
}
87+
})();
88+
89+
const message: ThpError = {
90+
code: error,
91+
message: error ?? `Unknown ThpError ${errorType}`,
92+
};
93+
94+
return {
95+
type: 'ThpError',
96+
message,
97+
};
98+
};
99+
100+
const validateCrc = (decodedMessage: ReturnType<TransportProtocolDecode>) => {
101+
// payload length without crc
102+
const payloadLen = decodedMessage.length - CRC_LENGTH;
103+
const length = Buffer.alloc(2);
104+
length.writeUInt16BE(decodedMessage.length);
105+
// build crc locally
106+
const expectedCrc = crc32(
107+
Buffer.concat([
108+
decodedMessage.header,
109+
length,
110+
decodedMessage.payload.subarray(0, payloadLen),
111+
]),
112+
);
113+
// get crc from the message
114+
const crc = decodedMessage.payload.subarray(payloadLen, decodedMessage.length);
115+
116+
// compare both crc
117+
if (expectedCrc.compare(crc) !== 0) {
118+
throw new Error(
119+
`Invalid CRC. expected: ${expectedCrc.toString('hex')} received: ${crc.toString('hex')}`,
120+
);
121+
}
122+
};
123+
124+
// Decode protocol-v2 message from thp send process: ThpAck or ThpError
125+
export const decodeSendAck = (decodedMessage: MessageV2) => {
126+
validateCrc(decodedMessage);
127+
128+
const header = readThpHeader(decodedMessage.header);
129+
const magic = clearControlBit(header.magic);
130+
if (magic === THP_ERROR_HEADER_BYTE) {
131+
return decodeThpError(decodedMessage.payload);
132+
}
133+
if (magic === THP_READ_ACK_HEADER_BYTE) {
134+
return decodeReadAck();
135+
}
136+
137+
throw new Error('Unexpected send response: ' + magic);
138+
};
139+
140+
// Decode protocol-v2 message from thp receive process
141+
export const decode = (
142+
decodedMessage: MessageV2,
143+
protobufDecoder: ProtobufDecoder,
144+
thpState?: ThpState,
145+
): ThpMessageResponse => {
146+
if (!thpState) {
147+
throw new Error('Cannot decode THP message without ThpState');
148+
}
149+
150+
validateCrc(decodedMessage);
151+
152+
const header = readThpHeader(decodedMessage.header);
153+
const message: ThpMessage = {
154+
...decodedMessage,
155+
...header,
156+
thpState,
157+
};
158+
159+
const magic = clearControlBit(message.magic);
160+
if (magic === THP_ERROR_HEADER_BYTE) {
161+
return decodeThpError(message.payload);
162+
}
163+
164+
if (magic === THP_READ_ACK_HEADER_BYTE) {
165+
return decodeReadAck();
166+
}
167+
168+
if (magic === THP_CREATE_CHANNEL_RESPONSE) {
169+
return createChannelResponse(message, protobufDecoder);
170+
}
171+
172+
throw new Error('Unknown message type: ' + magic);
173+
};

0 commit comments

Comments
 (0)