src/RSAPublicKey.js

import * as asn1js from "asn1js";
import { getParametersValue, toBase64, arrayBufferToString, stringToArrayBuffer, fromBase64, nearestPowerOf2, clearProps } from "pvutils";
//**************************************************************************************
/**
 * Class from RFC3447
 */
export default class RSAPublicKey
{
	//**********************************************************************************
	/**
	 * Constructor for RSAPublicKey class
	 * @param {Object} [parameters={}]
	 * @property {Object} [schema] asn1js parsed value
	 * @property {Integer} [modulus]
	 * @property {Integer} [publicExponent]
	 */
	constructor(parameters = {})
	{
		//region Internal properties of the object
		/**
		 * @type {Integer}
		 * @description Modulus part of RSA public key
		 */
		this.modulus = getParametersValue(parameters, "modulus", RSAPublicKey.defaultValues("modulus"));
		/**
		 * @type {Integer}
		 * @description Public exponent of RSA public key
		 */
		this.publicExponent = getParametersValue(parameters, "publicExponent", RSAPublicKey.defaultValues("publicExponent"));
		//endregion

		//region If input argument array contains "schema" for this object
		if("schema" in parameters)
			this.fromSchema(parameters.schema);
		//endregion
		//region If input argument array contains "json" for this object
		if("json" in parameters)
			this.fromJSON(parameters.json);
		//endregion
	}
	//**********************************************************************************
	/**
	 * Return default values for all class members
	 * @param {string} memberName String name for a class member
	 */
	static defaultValues(memberName)
	{
		switch(memberName)
		{
			case "modulus":
				return new asn1js.Integer();
			case "publicExponent":
				return new asn1js.Integer();
			default:
				throw new Error(`Invalid member name for RSAPublicKey class: ${memberName}`);
		}
	}
	//**********************************************************************************
	/**
	 * Return value of asn1js schema for current class
	 * @param {Object} parameters Input parameters for the schema
	 * @returns {Object} asn1js schema object
	 */
	static schema(parameters = {})
	{
		//RSAPublicKey ::= Sequence {
		//    modulus           Integer,  -- n
		//    publicExponent    Integer   -- e
		//}

		/**
		 * @type {Object}
		 * @property {string} utcTimeName Name for "utcTimeName" choice
		 * @property {string} generalTimeName Name for "generalTimeName" choice
		 */
		const names = getParametersValue(parameters, "names", {});

		return (new asn1js.Sequence({
			name: (names.blockName || ""),
			value: [
				new asn1js.Integer({ name: (names.modulus || "") }),
				new asn1js.Integer({ name: (names.publicExponent || "") })
			]
		}));
	}
	//**********************************************************************************
	/**
	 * Convert parsed asn1js object into current class
	 * @param {!Object} schema
	 */
	fromSchema(schema)
	{
		//region Clear input data first
		clearProps(schema, [
			"modulus",
			"publicExponent"
		]);
		//endregion
		
		//region Check the schema is valid
		const asn1 = asn1js.compareSchema(schema,
			schema,
			RSAPublicKey.schema({
				names: {
					modulus: "modulus",
					publicExponent: "publicExponent"
				}
			})
		);

		if(asn1.verified === false)
			throw new Error("Object's schema was not verified against input data for RSAPublicKey");
		//endregion

		//region Get internal properties from parsed schema
		this.modulus = asn1.result.modulus.convertFromDER(256);
		this.publicExponent = asn1.result.publicExponent;
		//endregion
	}
	//**********************************************************************************
	/**
	 * Convert current object to asn1js object and set correct values
	 * @returns {Object} asn1js object
	 */
	toSchema()
	{
		//region Construct and return new ASN.1 schema for this object
		return (new asn1js.Sequence({
			value: [
				this.modulus.convertToDER(),
				this.publicExponent
			]
		}));
		//endregion
	}
	//**********************************************************************************
	/**
	 * Convertion for the class to JSON object
	 * @returns {Object}
	 */
	toJSON()
	{
		return {
			n: toBase64(arrayBufferToString(this.modulus.valueBlock.valueHex), true, true, true),
			e: toBase64(arrayBufferToString(this.publicExponent.valueBlock.valueHex), true, true, true)
		};
	}
	//**********************************************************************************
	/**
	 * Convert JSON value into current object
	 * @param {Object} json
	 */
	fromJSON(json)
	{
		if("n" in json)
		{
			const array = stringToArrayBuffer(fromBase64(json.n, true));
			this.modulus = new asn1js.Integer({ valueHex: array.slice(0, Math.pow(2, nearestPowerOf2(array.byteLength))) });
		}
		else
			throw new Error("Absent mandatory parameter \"n\"");

		if("e" in json)
			this.publicExponent = new asn1js.Integer({ valueHex: stringToArrayBuffer(fromBase64(json.e, true)).slice(0, 3) });
		else
			throw new Error("Absent mandatory parameter \"e\"");
	}
	//**********************************************************************************
}
//**************************************************************************************