MTSC/MTSC/HelperFunctions.cs

using System;
using System.IO;
using System.Security.Cryptography;
using System.Xml;

namespace MTSC
{
    static class HelperFunctions
    {
        #region XML

        public static void FromXmlString(this RSA rsa, string xmlString)
        {
            RSAParameters parameters = new RSAParameters();

            XmlDocument xmlDoc = new XmlDocument();
            xmlDoc.LoadXml(xmlString);

            if (xmlDoc.DocumentElement.Name.Equals("RSAKeyValue"))
            {
                foreach (XmlNode node in xmlDoc.DocumentElement.ChildNodes)
                {
                    switch (node.Name)
                    {
                        case "Modulus": parameters.Modulus = (string.IsNullOrEmpty(node.InnerText) ? null : Convert.FromBase64String(node.InnerText)); break;
                        case "Exponent": parameters.Exponent = (string.IsNullOrEmpty(node.InnerText) ? null : Convert.FromBase64String(node.InnerText)); break;
                        case "P": parameters.P = (string.IsNullOrEmpty(node.InnerText) ? null : Convert.FromBase64String(node.InnerText)); break;
                        case "Q": parameters.Q = (string.IsNullOrEmpty(node.InnerText) ? null : Convert.FromBase64String(node.InnerText)); break;
                        case "DP": parameters.DP = (string.IsNullOrEmpty(node.InnerText) ? null : Convert.FromBase64String(node.InnerText)); break;
                        case "DQ": parameters.DQ = (string.IsNullOrEmpty(node.InnerText) ? null : Convert.FromBase64String(node.InnerText)); break;
                        case "InverseQ": parameters.InverseQ = (string.IsNullOrEmpty(node.InnerText) ? null : Convert.FromBase64String(node.InnerText)); break;
                        case "D": parameters.D = (string.IsNullOrEmpty(node.InnerText) ? null : Convert.FromBase64String(node.InnerText)); break;
                    }
                }
            }
            else
            {
                throw new Exception("Invalid XML RSA key.");
            }

            rsa.ImportParameters(parameters);
        }

        public static string ToXmlString(this RSA rsa, bool includePrivateParameters)
        {
            RSAParameters parameters = rsa.ExportParameters(includePrivateParameters);

            return string.Format("<RSAKeyValue><Modulus>{0}</Modulus><Exponent>{1}</Exponent><P>{2}</P><Q>{3}</Q><DP>{4}</DP><DQ>{5}</DQ><InverseQ>{6}</InverseQ><D>{7}</D></RSAKeyValue>",
                  parameters.Modulus != null ? Convert.ToBase64String(parameters.Modulus) : null,
                  parameters.Exponent != null ? Convert.ToBase64String(parameters.Exponent) : null,
                  parameters.P != null ? Convert.ToBase64String(parameters.P) : null,
                  parameters.Q != null ? Convert.ToBase64String(parameters.Q) : null,
                  parameters.DP != null ? Convert.ToBase64String(parameters.DP) : null,
                  parameters.DQ != null ? Convert.ToBase64String(parameters.DQ) : null,
                  parameters.InverseQ != null ? Convert.ToBase64String(parameters.InverseQ) : null,
                  parameters.D != null ? Convert.ToBase64String(parameters.D) : null);
        }
        /// <summary>
        /// Returns true if <paramref name="path"/> starts with the path <paramref name="baseDirPath"/>.
        /// The comparison is case-insensitive, handles / and \ slashes as folder separators and
        /// only matches if the base dir folder name is matched exactly ("c:\foobar\file.txt" is not a sub path of "c:\foo").
        /// </summary>
        public static bool IsSubPathOf(this string path, string baseDirPath)
        {
            string normalizedPath = Path.GetFullPath(path.Replace('/', '\\')
                .WithEnding("\\"));

            string normalizedBaseDirPath = Path.GetFullPath(baseDirPath.Replace('/', '\\')
                .WithEnding("\\"));

            return normalizedPath.StartsWith(normalizedBaseDirPath, StringComparison.OrdinalIgnoreCase);
        }
        /// <summary>
        /// Returns <paramref name="str"/> with the minimal concatenation of <paramref name="ending"/> (starting from end) that
        /// results in satisfying .EndsWith(ending).
        /// </summary>
        /// <example>"hel".WithEnding("llo") returns "hello", which is the result of "hel" + "lo".</example>
        public static string WithEnding(this string str, string ending)
        {
            if (str == null)
                return ending;

            string result = str;

            // Right() is 1-indexed, so include these cases
            // * Append no characters
            // * Append up to N characters, where N is ending length
            for (int i = 0; i <= ending.Length; i++)
            {
                string tmp = result + ending.Right(i);
                if (tmp.EndsWith(ending))
                    return tmp;
            }

            return result;
        }
        /// <summary>Gets the rightmost <paramref name="length" /> characters from a string.</summary>
        /// <param name="value">The string to retrieve the substring from.</param>
        /// <param name="length">The number of characters to retrieve.</param>
        /// <returns>The substring.</returns>
        public static string Right(this string value, int length)
        {
            if (value == null)
            {
                throw new ArgumentNullException("value");
            }
            if (length < 0)
            {
                throw new ArgumentOutOfRangeException("length", length, "Length is less than zero");
            }

            return (length < value.Length) ? value.Substring(value.Length - length) : value;
        }
        #endregion

        public static byte[] ReadRemainingBytes(this MemoryStream ms)
        {
            byte[] buffer = new byte[ms.Length - ms.Position];
            ms.Read(buffer, 0, buffer.Length);
            return buffer;
        }

        public static byte[] TrimTrailingNullBytes(this byte[] bytes)
        {
            int trimSize = 0;
            for(int i = bytes.Length - 1; i >= 0; i--)
            {
                if(bytes[i] == 0)
                {
                    trimSize++;
                }
                else
                {
                    break;
                }
            }
            byte[] newBytes = new byte[bytes.Length - trimSize];
            Array.Copy(bytes, 0, newBytes, 0, newBytes.Length);
            return newBytes;
        }
    }
}