@nteract/messaging/lib/wire-protocol.js

Messaging mechanics for nteract apps (jupyter spec)

"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
exports.encode = exports.decode = void 0;
const crypt = require("crypto");
const WIRE_PROTOCOL_DELIMITER = "<IDS|MSG>";
// There must be at least 5 frames after the delimiter:
// HMAC signature, serialized header, serialized parent header,
// serialized metadata, serialized content
const REQUIRED_NUMBER_OF_MESSAGE_FRAMES = 5;
function toJSON(value) {
    return JSON.parse(value.toString());
}
function initializeMessage(_message) {
    const message = Object.assign({}, {
        header: {},
        parent_header: {},
        metadata: {},
        content: {},
        idents: [],
        buffers: []
    }, _message);
    return message;
}
/**
 * Convert from Pythonic HMAC scheme string to node.js compatible name.
 *
 * Only support sha256 at the moment, which is all Jupyter uses nowadays anyhow.
 *
 * @param _scheme Examples: "hmac-sha256", "sha256"
 */
function identifyHMACScheme(_scheme) {
    let scheme = _scheme;
    switch (_scheme) {
        case "hmac-sha256":
            scheme = "sha256";
            break;
    }
    return scheme;
}
/**
 * Convert raw message frames from a Jupyter ZeroMQ connection to the object based JupyterMessage format
 *
 * @param messageFrames individual components of a message
 * @param _scheme only sha256 is supported at the moment
 * @param key HMAC key for frames 2+
 */
function decode(messageFrames, key, _scheme = "sha256") {
    var i = 0;
    const idents = [];
    for (i = 0; i < messageFrames.length; i++) {
        var frame = messageFrames[i];
        if (frame.toString() === WIRE_PROTOCOL_DELIMITER) {
            break;
        }
        idents.push(frame);
    }
    if (messageFrames.length - i < REQUIRED_NUMBER_OF_MESSAGE_FRAMES) {
        throw new Error("Message Decoding: Not enough message frames");
    }
    if (messageFrames[i].toString() !== WIRE_PROTOCOL_DELIMITER) {
        throw new Error("Message Decoding: Missing delimiter");
    }
    if (key) {
        const scheme = identifyHMACScheme(_scheme);
        var obtainedSignature = messageFrames[i + 1].toString();
        var hmac = crypt.createHmac(scheme, key);
        hmac.update(messageFrames[i + 2]);
        hmac.update(messageFrames[i + 3]);
        hmac.update(messageFrames[i + 4]);
        hmac.update(messageFrames[i + 5]);
        var expectedSignature = hmac.digest("hex");
        if (expectedSignature !== obtainedSignature) {
            throw new Error(`Message Decoding: Incorrect;
Obtained "${obtainedSignature}"
Expected "${expectedSignature}"`);
        }
    }
    var message = initializeMessage({
        idents: idents,
        header: toJSON(messageFrames[i + 2]),
        parent_header: toJSON(messageFrames[i + 3]),
        content: toJSON(messageFrames[i + 5]),
        metadata: toJSON(messageFrames[i + 4]),
        buffers: Array.prototype.slice.apply(messageFrames, [i + 6])
    });
    return message;
}
exports.decode = decode;
/**
 * Convert from the object based jupyter message to raw message frames
 */
function encode(_message, key, _scheme = "sha256") {
    // Ensure defaults are set for the message
    const message = initializeMessage(_message);
    const scheme = identifyHMACScheme(_scheme);
    const idents = message.idents;
    const header = Buffer.from(JSON.stringify(message.header), "utf-8");
    const parent_header = Buffer.from(JSON.stringify(message.parent_header), "utf-8");
    const metadata = Buffer.from(JSON.stringify(message.metadata), "utf-8");
    const content = Buffer.from(JSON.stringify(message.content), "utf-8");
    let signature = "";
    if (key) {
        const hmac = crypt.createHmac(scheme, key);
        hmac.update(header);
        hmac.update(parent_header);
        hmac.update(metadata);
        hmac.update(content);
        signature = hmac.digest("hex");
    }
    var response = idents
        .concat([
        // idents
        Buffer.from(WIRE_PROTOCOL_DELIMITER),
        Buffer.from(signature),
        header,
        parent_header,
        metadata,
        content // content
    ])
        .concat(message.buffers);
    return response;
}
exports.encode = encode;
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