MARKUS

using System;

using System.Diagnostics;

using System.Linq;

using System.IO;

using System.Reflection;

using System.Security.Cryptography;

using NetSparkleUpdater.Enums;

using NetSparkleUpdater.Interfaces;

namespace NetSparkleUpdater.SignatureVerifiers

{

    /// <summary>

    /// Class to verify a DSA signature

    /// </summary>

    public class DSAChecker : ISignatureVerifier

    {

        private DSACryptoServiceProvider _cryptoProvider;

        /// <summary>

        /// Determines if a public key exists

        /// </summary>

        /// <returns><c>bool</c></returns>

        public bool HasValidKeyInformation()

        {

            return _cryptoProvider != null;

        }

        /// <summary>

        /// Create a DSAChecker object from the given parameters

        /// </summary>

        /// <param name="mode">The security mode of the validator. Controls what needs to be set in order to validate

        /// an app cast and its items.</param>

        /// <param name="publicKey">the public key as string (will be preferred before the file)</param>

        /// <param name="publicKeyFile">the public key file</param>

        public DSAChecker(SecurityMode mode, string publicKey = null, string publicKeyFile = "NetSparkle_DSA.pub")

        {

            SecurityMode = mode;

            string key = publicKey;

            if (string.IsNullOrEmpty(key))

            {

                Stream data = TryGetResourceStream(publicKeyFile);

                if (data == null)

                {

                    data = TryGetFileResource(publicKeyFile, data);

                }

                if (data != null)

                {

                    using (StreamReader reader = new StreamReader(data))

                    {

                        key = reader.ReadToEnd();

                    }

                }

            }

            if (!string.IsNullOrEmpty(key))

            {

                try

                {

                    _cryptoProvider = new DSACryptoServiceProvider();

                    _cryptoProvider.FromXmlString(key);

                }

                catch

                {

                    _cryptoProvider = null;

                }

            }

        }

        /// <summary>

        /// <inheritdoc/>

        /// </summary>

        public SecurityMode SecurityMode { get; set; }

        private bool CheckSecurityMode(string signature, ref ValidationResult result)

        {

            switch (SecurityMode)

            {

                case SecurityMode.UseIfPossible:

                    // if we have a DSA key, we only accept non-null signatures

                    if (HasValidKeyInformation() && string.IsNullOrEmpty(signature))

                    {

                        result = ValidationResult.Invalid;

                        return false;

                    }

                    // if we don't have an dsa key, we accept any signature

                    if (!HasValidKeyInformation())

                    {

                        result = ValidationResult.Unchecked;

                        return false;

                    }

                    break;

                case SecurityMode.Strict:

                    // only accept if we have both a public key and a non-null signature

                    if (!HasValidKeyInformation() || string.IsNullOrEmpty(signature))

                    {

                        result = ValidationResult.Invalid;

                        return false;

                    }

                    break;

                case SecurityMode.Unsafe:

                    // always accept anything

                    // If we don't have a signature, make sure to note this as "Unchecked" since we

                    // didn't end up checking anything due to a lack of public key/signature

                    if (!HasValidKeyInformation() || string.IsNullOrEmpty(signature))

                    {

                        result = ValidationResult.Unchecked;

                        return false;

                    }

                    break;

                case SecurityMode.OnlyVerifySoftwareDownloads:

                    // If we don't have a signature, make sure to note this as "Unchecked" since we

                    // didn't end up checking anything due to a lack of public key/signature

                    if (!HasValidKeyInformation() || string.IsNullOrEmpty(signature))

                    {

                        result = ValidationResult.Unchecked;

                        return false;

                    }

                    break;

            }

            return true;

        }

        /// <inheritdoc/>

        public ValidationResult VerifySignature(string signature, byte[] dataToVerify)

        {

            ValidationResult res = ValidationResult.Invalid;

            if (!CheckSecurityMode(signature, ref res))

            {

                return res;

            }

            // convert signature

            byte[] bHash = Convert.FromBase64String(signature);

            // verify

            return _cryptoProvider.VerifyData(dataToVerify, bHash) ? ValidationResult.Valid : ValidationResult.Invalid;

        }

        /// <inheritdoc/>

        public ValidationResult VerifySignatureOfFile(string signature, string binaryPath)

        {

            using (Stream inputStream = File.OpenRead(binaryPath))

            {

                return VerifySignature(signature, Utilities.ConvertStreamToByteArray(inputStream));

            }

        }

        /// <inheritdoc/>

        public ValidationResult VerifySignatureOfString(string signature, string data)

        {

            // creating stream from string

            using (var stream = new MemoryStream())

            using (var writer = new StreamWriter(stream))

            {

                writer.Write(data);

                writer.Flush();

                stream.Position = 0;

                return VerifySignature(signature, Utilities.ConvertStreamToByteArray(stream));

            }

        }

        /// <summary>

        /// Gets a file resource

        /// </summary>

        /// <param name="publicKey">the public key</param>

        /// <param name="data">the data stream</param>

        /// <returns>the data stream</returns>

        private static Stream TryGetFileResource(string publicKey, Stream data)

        {

            if (File.Exists(publicKey))

            {

                data = File.OpenRead(publicKey);

            }

            return data;

        }

        /// <summary>

        /// Get a resource stream

        /// </summary>

        /// <param name="publicKey">the public key</param>

        /// <returns>a stream</returns>

        private static Stream TryGetResourceStream(string publicKey)

        {

            Stream data = null;

            foreach (Assembly asm in AppDomain.CurrentDomain.GetAssemblies())

            {

                string[] resources;

                try

                {

                    resources = asm.GetManifestResourceNames();

                }

                catch (NotSupportedException)

                {

                    continue;

                }

                var resourceName = resources.FirstOrDefault(s => s.IndexOf(publicKey, StringComparison.OrdinalIgnoreCase) > -1);

                if (!string.IsNullOrEmpty(resourceName))

                {

                    data = asm.GetManifestResourceStream(resourceName);

                    if (data != null)

                    {

                        break;

                    }

                }

            }

            return data;

        }

    }

}