112 lines
2.8 KiB
JavaScript
112 lines
2.8 KiB
JavaScript
/*
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* Copyright (c) 2014-2015 Sylvain Peyrefitte
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*
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* This file is part of node-rdpjs.
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*
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* node-rdpjs is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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var type = require('../core').type;
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var log = require('../core').log;
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var error = require('../core').error;
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/**
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* Parse tag(T) field of BER TLV
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* And check with expected tag
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* @param s {type.Stream}
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* @param tag {spec.tag}
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* @returns {Boolean} True for valid tag matching
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*/
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function decodeTag(s, tag) {
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var nextTag = new type.UInt8().read(s).value;
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if (tag.tagNumber > 30) {
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nextTagNumber = new type.UInt8().read(s).value;
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}
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else {
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nextTagNumber = nextTag & 0x1F;
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}
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return ((nextTag & 0xE0) === (tag.tagClass | tag.tagFormat)) && (nextTagNumber === tag.tagNumber);
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};
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/**
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* Parse length(L) field of BER TLV
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* @param s {type.Stream}
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* @returns {integer}
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*/
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function decodeLength(s) {
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var size = new type.UInt8().read(s).value;
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if(size & 0x80) {
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size &= ~0x80;
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if(size === 1) {
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size = new type.UInt8().read(s).value;
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}
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else if(size === 2) {
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size = new type.UInt16Be().read(s).value;
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}
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else{
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throw new error.ProtocolError('NODE_RDP_ASN1_BER_INVALID_LENGTH');
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}
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}
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return size;
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};
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/**
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* Decode tuple TLV (Tag Length Value) of BER
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* @param s {type.Stream}
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* @param tag {spec.Asn1Tag} expected tag
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* @returns {type.BinaryString} Value of tuple
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*/
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function decode(s, tag) {
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if (!decodeTag(s, tag)) {
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throw new error.ProtocolError('NODE_RDP_ASN1_BER_INVALID_TAG');
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}
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var length = decodeLength(s);
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if (length === 0) {
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return new type.Stream(0);
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}
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return new type.BinaryString(null,{ readLength : new type.CallableValue(length) }).read(s);
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};
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function encodeTag(tag) {
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if(tag.tagNumber > 30) {
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return new type.Component([new type.UInt8(tag.tagClass | tag.tagFormat | 0x1F), new type.UInt8(tag.tagNumber)]);
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}
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else {
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return new type.UInt8((tag.tagClass | tag.tagFormat) | (tag.tagNumber & 0x1F));
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}
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}
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function encodeLength(length) {
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if(length > 0x7f) {
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return new type.Component([new type.UInt8(0x82), new type.UInt16Be(length)]);
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}
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else {
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return new type.UInt8(length);
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}
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}
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function encode(tag, buffer) {
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return new type.Component([encodeTag(tag), encodeLength(buffer.size()), buffer]);
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}
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/**
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* Module Export
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*/
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module.exports = {
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decode : decode,
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encode : encode
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};
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