bitmessage-js/lib/structs.js

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/**
* Implements common structures.
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* @see {@link https://bitmessage.org/wiki/Protocol_specification#Common_structures}
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* @module bitmessage/structs
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*/
"use strict";
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require("object.assign").shim();
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var bufferEqual = require("buffer-equal");
var assert = require("./util").assert;
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var bmcrypto = require("./crypto");
function isAscii(str) {
for (var i = 0; i < str.length; i++) {
if (str.charCodeAt(i) > 127) {
return false;
}
}
return true;
}
function getchecksum(data) {
return bmcrypto.sha512(data).slice(0, 4);
}
/**
* Message structure.
* @see {@link https://bitmessage.org/wiki/Protocol_specification#Message_structure}
* @namespace
* @static
*/
var message = exports.message = {
/** Bitmessage magic value. */
MAGIC: 0xE9BEB4D9,
/**
* Decode message structure.
* @param {Buffer} buf - Buffer that starts with encoded message
* structure
* @return {{command: string, payload: Buffer, length: number, rest: Buffer}}
* Decoded message structure.
*/
decode: function(buf) {
assert(buf.length >= 24, "Buffer is too small");
assert(buf.readUInt32BE(0, true) === message.MAGIC, "Wrong magic");
var command = buf.slice(4, 16);
var firstNonNull;
for (var i = 11; i >=0; i--) {
assert(command[i] <= 127, "Non-ASCII characters in command");
if (firstNonNull === undefined && command[i] !== 0) {
firstNonNull = i;
}
}
command = command.slice(0, firstNonNull + 1).toString("ascii");
var payloadLength = buf.readUInt32BE(16, true);
assert(payloadLength <= 262144, "Payload is too big");
var checksum = buf.slice(20, 24);
var length = 24 + payloadLength;
var payload = buf.slice(24, length);
assert(bufferEqual(checksum, getchecksum(payload)), "Bad checkum");
var rest = buf.slice(length);
return {command: command, payload: payload, length: length, rest: rest};
},
/**
* Encode message structure.
* @param {string} command - ASCII string identifying the packet
* content
* @param {Buffer} payload - The actual data, a message or an object
* @return {Buffer} Encoded message structure.
*/
encode: function(command, payload) {
assert(command.length <= 12, "Command is too long");
assert(isAscii(command), "Non-ASCII characters in command");
assert(payload.length <= 262144, "Payload is too big");
var buf = new Buffer(24 + payload.length);
buf.fill(0);
buf.writeUInt32BE(message.MAGIC, 0, true);
buf.write(command, 4);
buf.writeUInt32BE(payload.length, 16, true);
getchecksum(payload).copy(buf, 20);
payload.copy(buf, 24);
return buf;
},
};
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/**
* var_int.
* @see {@link https://bitmessage.org/wiki/Protocol_specification#Variable_length_integer}
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* @namespace
* @static
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*/
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var var_int = exports.var_int = {
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/**
* Decode var_int.
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* @param {Buffer} buf - A buffer that starts with encoded var_int
* @return {{value: number, length: number, rest: Buffer}}
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* Decoded var_int structure.
*/
decode: function(buf) {
var value, length;
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assert(buf.length > 0, "Empty buffer");
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switch (buf[0]) {
case 253:
value = buf.readUInt16BE(1);
assert(value >= 253, "Impractical var_int");
length = 3;
break;
case 254:
value = buf.readUInt32BE(1);
assert(value >= 65536, "Impractical var_int");
length = 5;
break;
case 255:
var hi = buf.readUInt32BE(1);
assert(hi !== 0, "Impractical var_int");
// Max safe number = 2^53 - 1 =
// 0b0000000000011111111111111111111111111111111111111111111111111111
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// = 2097151*(2^32) + (2^32 - 1).
// So it's safe until hi <= 2097151. See
// <http://mdn.io/issafeinteger>,
// <https://stackoverflow.com/q/307179> for details.
// TODO(Kagami): We may want to return raw Buffer for
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// 2^53 <= value <= 2^64 - 1 range. Possibly using the optional
// argument because most of the code expect to get a number when
// calling `var_int.decode`.
assert(hi <= 2097151, "Unsafe integer");
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var lo = buf.readUInt32BE(5);
value = hi * 4294967296 + lo;
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length = 9;
break;
default:
value = buf[0];
length = 1;
}
var rest = buf.slice(length);
return {value: value, length: length, rest: rest};
},
/**
* Encode number into var_int.
* @param {(number|Buffer)} value - Input number
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* @return {Buffer} Encoded var_int.
*/
encode: function(value) {
var buf, targetStart;
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if (typeof value === "number") {
assert(value >= 0, "Value cannot be less than zero");
if (value < 253) {
buf = new Buffer([value]);
} else if (value < 65536) {
buf = new Buffer(3);
buf[0] = 253;
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buf.writeUInt16BE(value, 1, true);
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} else if (value < 4294967296) {
buf = new Buffer(5);
buf[0] = 254;
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buf.writeUInt32BE(value, 1, true);
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} else {
assert(value <= 9007199254740991, "Unsafe integer");
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buf = new Buffer(9);
buf[0] = 255;
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buf.writeUInt32BE(Math.floor(value / 4294967296), 1, true); // high32
buf.writeUInt32BE(value % 4294967296, 5, true); // low32
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}
} else if (Buffer.isBuffer(value)) {
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assert(value.length <= 8, "Buffer is too big");
buf = new Buffer(9);
buf.fill(0);
buf[0] = 255;
targetStart = 1 + (8 - value.length);
value.copy(buf, targetStart);
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} else {
throw new Error("Value encode error");
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}
return buf;
},
};
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/**
* var_str.
* @see {@link https://bitmessage.org/wiki/Protocol_specification#Variable_length_string}
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* @namespace
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*/
exports.var_str = {
/**
* Decode var_str.
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* @param {Buffer} buf - A buffer that starts with encoded var_str
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* @return {{str: string, length: number, rest: Buffer}}
* Decoded var_str structure.
*/
decode: function(buf) {
var decoded = var_int.decode(buf);
var strLength = decoded.value;
// XXX(Kagami): Spec doesn't mention encoding, using UTF-8.
var str = decoded.rest.slice(0, strLength).toString();
var rest = decoded.rest.slice(strLength);
return {str: str, length: decoded.length + strLength, rest: rest};
},
/**
* Encode string into var_str.
* @param {string} str - A string
* @return {Buffer} Encoded var_str.
*/
encode: function(str) {
// XXX(Kagami): Spec doesn't mention encoding, using UTF-8.
var strBuf = new Buffer(str);
return Buffer.concat([var_int.encode(strBuf.length), strBuf]);
},
};
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/**
* var_int_list.
* @see {@link https://bitmessage.org/wiki/Protocol_specification#Variable_length_list_of_integers}
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* @namespace
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*/
exports.var_int_list = {
/**
* Decode var_int_list.
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* @param {Buffer} buf - A buffer that starts with encoded
* var_int_list
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* @return {{list: number[], length: number, rest: Buffer}}
* Decoded var_int_list structure.
*/
decode: function(buf) {
var decoded = var_int.decode(buf);
var listLength = decoded.value;
var list = new Array(listLength);
var rest = decoded.rest;
var sumLength = decoded.length;
for (var i = 0; i < listLength; i++) {
decoded = var_int.decode(rest);
list[i] = decoded.value;
rest = decoded.rest;
sumLength += decoded.length;
}
return {list: list, length: sumLength, rest: rest};
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},
/**
* Encode list of numbers into var_int_list.
* @param {number[]} list - A number list
* @return {Buffer} Encoded var_int_list.
*/
encode: function(list) {
var listBuf = Buffer.concat(list.map(var_int.encode));
return Buffer.concat([var_int.encode(list.length), listBuf]);
},
};
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/**
* Message encodings. Extends {@link var_int} by adding known encoding type
* constants.
* @see {@link https://bitmessage.org/wiki/Protocol_specification#Message_Encodings}
*/
exports.messageEncodings = Object.assign(Object.create(var_int), {
/**
* Any data with this number may be ignored. The sending node might
* simply be sharing its public key with you.
*/
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IGNORE: 0,
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/**
* UTF-8. No 'Subject' or 'Body' sections. Useful for simple strings
* of data, like URIs or magnet links.
*/
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TRIVIAL: 1,
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/**
* UTF-8. Uses 'Subject' and 'Body' sections. No MIME is used.
*/
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SIMPLE: 2,
});
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// Creates bitfield class of the specified size.
var bitfield = function(size) {
var bytesize = size / 8;
return {
decode: function(buf) {
assert(buf.length === bytesize, "Bad buffer size");
var features = [];
var index;
for (var i = 0; i < size; i++) {
index = bytesize - Math.floor(i / 8) - 1;
if ((buf[index] & (1 << (i % 8))) !== 0) { // jshint ignore:line
features.push(i);
}
}
return features;
},
encode: function(features) {
var buf = new Buffer(bytesize);
buf.fill(0);
features.forEach(function(feature) {
assert(feature >= 0, "Bad feature");
assert(feature <= (size - 1), "Bad feature");
var index = bytesize - Math.floor(feature / 8) - 1;
buf[index] |= 1 << (feature % 8); // jshint ignore:line
});
return buf;
},
};
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};
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/**
* Service bitfield features. Implements encoding/decoding for a 8-byte
* buffer object.
* @see {@link https://bitmessage.org/wiki/Protocol_specification#version}
*/
exports.serviceFeatures = Object.assign(bitfield(64), {
/** This is a normal network node. */
NODE_NETWORK: 0,
});
/**
* Pubkey bitfield features. Implements encoding/decoding for a 4-byte
* buffer object.
* @see {@link https://bitmessage.org/wiki/Protocol_specification#Pubkey_bitfield_features}
*/
exports.pubkeyFeatures = Object.assign(bitfield(32), {
/**
* Receiving node expects that the RIPE hash encoded in their address
* preceedes the encrypted message data of msg messages bound for
* them.
*/
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INCLUDE_DESTINATION: 30,
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/**
* If true, the receiving node does send acknowledgements (rather than
* dropping them).
*/
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DOES_ACK: 31,
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});