CyberChef/src/js/operations/QuotedPrintable.js

/** @license
========================================================================
  mimelib: http://github.com/andris9/mimelib
  Copyright (c) 2011-2012 Andris Reinman
  
  Permission is hereby granted, free of charge, to any person obtaining a copy
  of this software and associated documentation files (the "Software"), to deal
  in the Software without restriction, including without limitation the rights
  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  copies of the Software, and to permit persons to whom the Software is
  furnished to do so, subject to the following conditions:
  
  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  SOFTWARE.
*/

/**
 * Quoted Printable operations.
 * Some parts taken from mimelib (http://github.com/andris9/mimelib)
 *
 * @author Andris Reinman
 * @author n1474335 [n1474335@gmail.com]
 * @copyright Crown Copyright 2016
 * @license Apache-2.0
 *
 * @namespace
 */
var QuotedPrintable = {
    
    /**
     * To Quoted Printable operation.
     *
     * @param {byte_array} input
     * @param {Object[]} args
     * @returns {string}
     */
    run_to: function (input, args) {
        var mimeEncodedStr = QuotedPrintable.mimeEncode(input);
        
        // fix line breaks
        mimeEncodedStr = mimeEncodedStr.replace(/\r?\n|\r/g, function() {
            return "\r\n";
        }).replace(/[\t ]+$/gm, function(spaces) {
            return spaces.replace(/ /g, "=20").replace(/\t/g, "=09");
        });

        return QuotedPrintable._addSoftLinebreaks(mimeEncodedStr, "qp");
    },
    
    
    /**
     * From Quoted Printable operation.
     *
     * @param {string} input
     * @param {Object[]} args
     * @returns {byte_array}
     */
    run_from: function (input, args) {
        var str = input.replace(/\=(?:\r?\n|$)/g, "");
        return QuotedPrintable.mimeDecode(str);
    },
    
    
    /**
     * Decodes mime-encoded data.
     *
     * @param {string} str
     * @returns {byte_array}
     */
    mimeDecode: function(str) {
        var encodedBytesCount = (str.match(/\=[\da-fA-F]{2}/g) || []).length,
            bufferLength = str.length - encodedBytesCount * 2,
            chr, hex,
            buffer = new Array(bufferLength),
            bufferPos = 0;

        for (var i = 0, len = str.length; i < len; i++) {
            chr = str.charAt(i);
            if (chr === "=" && (hex = str.substr(i + 1, 2)) && /[\da-fA-F]{2}/.test(hex)) {
                buffer[bufferPos++] = parseInt(hex, 16);
                i += 2;
                continue;
            }
            buffer[bufferPos++] = chr.charCodeAt(0);
        }

        return buffer;
    },
    
    
    /**
     * Encodes mime data.
     *
     * @param {byte_array} buffer
     * @returns {string}
     */
    mimeEncode: function(buffer) {
        var ranges = [
                [0x09],
                [0x0A],
                [0x0D],
                [0x20],
                [0x21],
                [0x23, 0x3C],
                [0x3E],
                [0x40, 0x5E],
                [0x60, 0x7E]
            ],
            result = "";

        for (var i = 0, len = buffer.length; i < len; i++) {
            if (this._checkRanges(buffer[i], ranges)) {
                result += String.fromCharCode(buffer[i]);
                continue;
            }
            result += "=" + (buffer[i] < 0x10 ? "0" : "") + buffer[i].toString(16).toUpperCase();
        }

        return result;
    },
    
    
    /**
     * Checks if a given number falls within a given set of ranges.
     *
     * @private
     * @param {number} nr
     * @param {byte_array[]} ranges
     * @returns {bolean}
     */
    _checkRanges: function(nr, ranges) {
        for (var i = ranges.length - 1; i >= 0; i--) {
            if (!ranges[i].length)
                continue;
            if (ranges[i].length === 1 && nr === ranges[i][0])
                return true;
            if (ranges[i].length === 2 && nr >= ranges[i][0] && nr <= ranges[i][1])
                return true;
        }
        return false;
    },

    
    /**
     * Adds soft line breaks to a string.
     * Lines can't be longer that 76 + <CR><LF> = 78 bytes
     * http://tools.ietf.org/html/rfc2045#section-6.7
     *
     * @private
     * @param {string} str
     * @param {string} encoding
     * @returns {string}
     */
    _addSoftLinebreaks: function(str, encoding) {
        var lineLengthMax = 76;

        encoding = (encoding || "base64").toString().toLowerCase().trim();

        if (encoding === "qp") {
            return this._addQPSoftLinebreaks(str, lineLengthMax);
        } else {
            return this._addBase64SoftLinebreaks(str, lineLengthMax);
        }
    },

    
    /**
     * Adds soft line breaks to a base64 string.
     *
     * @private
     * @param {string} base64EncodedStr
     * @param {number} lineLengthMax
     * @returns {string}
     */
    _addBase64SoftLinebreaks: function(base64EncodedStr, lineLengthMax) {
        base64EncodedStr = (base64EncodedStr || "").toString().trim();
        return base64EncodedStr.replace(new RegExp(".{" + lineLengthMax + "}", "g"), "$&\r\n").trim();
    },

    
    /**
     * Adds soft line breaks to a quoted printable string.
     *
     * @private
     * @param {string} mimeEncodedStr
     * @param {number} lineLengthMax
     * @returns {string}
     */
    _addQPSoftLinebreaks: function(mimeEncodedStr, lineLengthMax) {
        var pos = 0,
            len = mimeEncodedStr.length,
            match, code, line,
            lineMargin = Math.floor(lineLengthMax / 3),
            result = "";

        // insert soft linebreaks where needed
        while (pos < len) {
            line = mimeEncodedStr.substr(pos, lineLengthMax);
            if ((match = line.match(/\r\n/))) {
                line = line.substr(0, match.index + match[0].length);
                result += line;
                pos += line.length;
                continue;
            }

            if (line.substr(-1) === "\n") {
                // nothing to change here
                result += line;
                pos += line.length;
                continue;
            } else if ((match = line.substr(-lineMargin).match(/\n.*?$/))) {
                // truncate to nearest line break
                line = line.substr(0, line.length - (match[0].length - 1));
                result += line;
                pos += line.length;
                continue;
            } else if (line.length > lineLengthMax - lineMargin && (match = line.substr(-lineMargin).match(/[ \t\.,!\?][^ \t\.,!\?]*$/))) {
                // truncate to nearest space
                line = line.substr(0, line.length - (match[0].length - 1));
            } else if (line.substr(-1) === "\r") {
                line = line.substr(0, line.length - 1);
            } else {
                if (line.match(/\=[\da-f]{0,2}$/i)) {

                    // push incomplete encoding sequences to the next line
                    if ((match = line.match(/\=[\da-f]{0,1}$/i))) {
                        line = line.substr(0, line.length - match[0].length);
                    }

                    // ensure that utf-8 sequences are not split
                    while (line.length > 3 && line.length < len - pos && !line.match(/^(?:=[\da-f]{2}){1,4}$/i) && (match = line.match(/\=[\da-f]{2}$/ig))) {
                        code = parseInt(match[0].substr(1, 2), 16);
                        if (code < 128) {
                            break;
                        }

                        line = line.substr(0, line.length - 3);

                        if (code >= 0xC0) {
                            break;
                        }
                    }

                }
            }

            if (pos + line.length < len && line.substr(-1) !== "\n") {
                if (line.length === 76 && line.match(/\=[\da-f]{2}$/i)) {
                    line = line.substr(0, line.length - 3);
                } else if (line.length === 76) {
                    line = line.substr(0, line.length - 1);
                }
                pos += line.length;
                line += "=\r\n";
            } else {
                pos += line.length;
            }

            result += line;
        }

        return result;
    },
    
};