265 lines
9.1 KiB
JavaScript
265 lines
9.1 KiB
JavaScript
// GPG4Browsers - An OpenPGP implementation in javascript
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// Copyright (C) 2011 Recurity Labs GmbH
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//
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// This library is free software; you can redistribute it and/or
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// modify it under the terms of the GNU Lesser General Public
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// License as published by the Free Software Foundation; either
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// version 2.1 of the License, or (at your option) any later version.
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//
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// This library 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 GNU
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// Lesser General Public License for more details.
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//
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// You should have received a copy of the GNU Lesser General Public
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// License along with this library; if not, write to the Free Software
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// Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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/**
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* @requires enums
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* @requires util
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* @module packet/packet
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*/
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var enums = require('../enums.js'),
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util = require('../util');
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module.exports = {
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readSimpleLength: function(bytes) {
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var len = 0,
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offset,
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type = bytes.charCodeAt(0);
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if (type < 192) {
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len = bytes.charCodeAt(0);
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offset = 1;
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} else if (type < 255) {
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len = ((bytes.charCodeAt(0) - 192) << 8) + (bytes.charCodeAt(1)) + 192;
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offset = 2;
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} else if (type == 255) {
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len = util.readNumber(bytes.substr(1, 4));
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offset = 5;
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}
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return {
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len: len,
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offset: offset
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};
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},
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/**
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* Encodes a given integer of length to the openpgp length specifier to a
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* string
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*
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* @param {Integer} length The length to encode
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* @return {String} String with openpgp length representation
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*/
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writeSimpleLength: function(length) {
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var result = "";
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if (length < 192) {
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result += String.fromCharCode(length);
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} else if (length > 191 && length < 8384) {
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/*
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* let a = (total data packet length) - 192 let bc = two octet
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* representation of a let d = b + 192
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*/
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result += String.fromCharCode(((length - 192) >> 8) + 192);
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result += String.fromCharCode((length - 192) & 0xFF);
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} else {
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result += String.fromCharCode(255);
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result += util.writeNumber(length, 4);
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}
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return result;
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},
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/**
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* Writes a packet header version 4 with the given tag_type and length to a
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* string
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*
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* @param {Integer} tag_type Tag type
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* @param {Integer} length Length of the payload
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* @return {String} String of the header
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*/
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writeHeader: function(tag_type, length) {
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/* we're only generating v4 packet headers here */
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var result = "";
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result += String.fromCharCode(0xC0 | tag_type);
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result += this.writeSimpleLength(length);
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return result;
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},
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/**
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* Writes a packet header Version 3 with the given tag_type and length to a
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* string
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*
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* @param {Integer} tag_type Tag type
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* @param {Integer} length Length of the payload
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* @return {String} String of the header
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*/
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writeOldHeader: function(tag_type, length) {
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var result = "";
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if (length < 256) {
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result += String.fromCharCode(0x80 | (tag_type << 2));
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result += String.fromCharCode(length);
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} else if (length < 65536) {
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result += String.fromCharCode(0x80 | (tag_type << 2) | 1);
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result += util.writeNumber(length, 2);
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} else {
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result += String.fromCharCode(0x80 | (tag_type << 2) | 2);
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result += util.writeNumber(length, 4);
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}
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return result;
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},
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/**
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* Generic static Packet Parser function
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*
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* @param {String} input Input stream as string
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* @param {integer} position Position to start parsing
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* @param {integer} len Length of the input from position on
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* @return {Object} Returns a parsed module:packet/packet
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*/
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read: function(input, position, len) {
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// some sanity checks
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if (input === null || input.length <= position || input.substring(position).length < 2 || (input.charCodeAt(position) &
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0x80) === 0) {
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throw new Error("Error during parsing. This message / key is probably not containing a valid OpenPGP format.");
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}
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var mypos = position;
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var tag = -1;
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var format = -1;
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var packet_length;
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format = 0; // 0 = old format; 1 = new format
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if ((input.charCodeAt(mypos) & 0x40) !== 0) {
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format = 1;
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}
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var packet_length_type;
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if (format) {
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// new format header
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tag = input.charCodeAt(mypos) & 0x3F; // bit 5-0
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} else {
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// old format header
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tag = (input.charCodeAt(mypos) & 0x3F) >> 2; // bit 5-2
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packet_length_type = input.charCodeAt(mypos) & 0x03; // bit 1-0
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}
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// header octet parsing done
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mypos++;
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// parsed length from length field
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var bodydata = null;
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// used for partial body lengths
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var real_packet_length = -1;
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if (!format) {
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// 4.2.1. Old Format Packet Lengths
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switch (packet_length_type) {
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case 0:
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// The packet has a one-octet length. The header is 2 octets
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// long.
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packet_length = input.charCodeAt(mypos++);
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break;
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case 1:
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// The packet has a two-octet length. The header is 3 octets
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// long.
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packet_length = (input.charCodeAt(mypos++) << 8) | input.charCodeAt(mypos++);
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break;
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case 2:
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// The packet has a four-octet length. The header is 5
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// octets long.
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packet_length = (input.charCodeAt(mypos++) << 24) | (input.charCodeAt(mypos++) << 16) | (input.charCodeAt(mypos++) <<
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8) | input.charCodeAt(mypos++);
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break;
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default:
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// 3 - The packet is of indeterminate length. The header is 1
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// octet long, and the implementation must determine how long
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// the packet is. If the packet is in a file, this means that
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// the packet extends until the end of the file. In general,
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// an implementation SHOULD NOT use indeterminate-length
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// packets except where the end of the data will be clear
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// from the context, and even then it is better to use a
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// definite length, or a new format header. The new format
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// headers described below have a mechanism for precisely
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// encoding data of indeterminate length.
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packet_length = len;
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break;
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}
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} else // 4.2.2. New Format Packet Lengths
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{
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// 4.2.2.1. One-Octet Lengths
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if (input.charCodeAt(mypos) < 192) {
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packet_length = input.charCodeAt(mypos++);
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util.print_debug("1 byte length:" + packet_length);
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// 4.2.2.2. Two-Octet Lengths
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} else if (input.charCodeAt(mypos) >= 192 && input.charCodeAt(mypos) < 224) {
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packet_length = ((input.charCodeAt(mypos++) - 192) << 8) + (input.charCodeAt(mypos++)) + 192;
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util.print_debug("2 byte length:" + packet_length);
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// 4.2.2.4. Partial Body Lengths
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} else if (input.charCodeAt(mypos) > 223 && input.charCodeAt(mypos) < 255) {
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packet_length = 1 << (input.charCodeAt(mypos++) & 0x1F);
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util.print_debug("4 byte length:" + packet_length);
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// EEEK, we're reading the full data here...
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var mypos2 = mypos + packet_length;
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bodydata = input.substring(mypos, mypos + packet_length);
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var tmplen;
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while (true) {
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if (input.charCodeAt(mypos2) < 192) {
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tmplen = input.charCodeAt(mypos2++);
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packet_length += tmplen;
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bodydata += input.substring(mypos2, mypos2 + tmplen);
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mypos2 += tmplen;
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break;
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} else if (input.charCodeAt(mypos2) >= 192 && input.charCodeAt(mypos2) < 224) {
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tmplen = ((input.charCodeAt(mypos2++) - 192) << 8) + (input.charCodeAt(mypos2++)) + 192;
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packet_length += tmplen;
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bodydata += input.substring(mypos2, mypos2 + tmplen);
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mypos2 += tmplen;
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break;
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} else if (input.charCodeAt(mypos2) > 223 && input.charCodeAt(mypos2) < 255) {
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tmplen = 1 << (input.charCodeAt(mypos2++) & 0x1F);
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packet_length += tmplen;
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bodydata += input.substring(mypos2, mypos2 + tmplen);
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mypos2 += tmplen;
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} else {
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mypos2++;
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tmplen = (input.charCodeAt(mypos2++) << 24) | (input.charCodeAt(mypos2++) << 16) | (input[mypos2++]
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.charCodeAt() << 8) | input.charCodeAt(mypos2++);
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bodydata += input.substring(mypos2, mypos2 + tmplen);
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packet_length += tmplen;
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mypos2 += tmplen;
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break;
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}
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}
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real_packet_length = mypos2;
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// 4.2.2.3. Five-Octet Lengths
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} else {
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mypos++;
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packet_length = (input.charCodeAt(mypos++) << 24) | (input.charCodeAt(mypos++) << 16) | (input.charCodeAt(mypos++) <<
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8) | input.charCodeAt(mypos++);
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}
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}
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// if there was'nt a partial body length: use the specified
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// packet_length
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if (real_packet_length == -1) {
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real_packet_length = packet_length;
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}
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if (bodydata === null) {
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bodydata = input.substring(mypos, mypos + real_packet_length);
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}
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return {
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tag: tag,
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packet: bodydata,
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offset: mypos + real_packet_length
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};
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}
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};
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