如何计算sftp文件的Sha256哈希？

Question

我的代码从SFTP服务器下载文件，而下载时我想计算即将要下载的文件的Sha256哈希代码。这样我就不会下载重复的文件。

我目前正在Renci.SshNet和Renci.SshNet.sftp上进行SFTP下载操作。它们成功完成。唯一的问题是计算哈希 我已经有一个主哈希表可以交叉检查我的数据库。

请建议使用a来计算哈希值。

我将代码放置如下。

 namespace DownloadFromFTP
    {
    class Program
    {

        string sqlcon = ConfigurationManager.ConnectionStrings["sqlConn"].ToString();
        static void Main(string[] args)
        {
            try
            {
                Program program = new Program();

                SqlConnection scon = new SqlConnection(program.sqlcon);

                string command = ConfigurationManager.AppSettings["GethashTable"].ToString();

                SqlDataAdapter sql = new SqlDataAdapter(command, scon);
                DataTable hashtable = new DataTable();
                sql.Fill(hashtable);

                var localPath = @"C:\Users\user1\Desktop\Working Copy\imagefromftp\hash\";

                var keyFile = new PrivateKeyFile(@"C:\Users\user1\Desktop\Working Copy\imagefromftp\openssh", "SecretKey");
                var keyFiles = new[] { keyFile };
                var username = "username";

                var methods = new List<AuthenticationMethod>();
                methods.Add(new PasswordAuthenticationMethod(username, "password"));
                methods.Add(new PrivateKeyAuthenticationMethod(username, keyFiles));

                var con = new ConnectionInfo("xx.xxx.xx.xxx", 21, username, methods.ToArray());
                using (var client = new SftpClient(con))
                {
                    client.Connect();

                    var files = client.ListDirectory("/my/mypath1/mypath2/docs/master/files");




                    foreach (var file in files)
                    {




                        if (file.Name != "." && file.Name != ".." & !file.IsSymbolicLink)
                        {




                            string remoteHash = program.Gethash(file.FullName).ToString();



                            bool result = hashtable.AsEnumerable().Where(c => c.Field<string>("sha_hash").Equals(remoteHash)).Count() < 0;


                            if (result == true )

                            {


                                string tblFileName = string.Empty;

                                string tblRemotePath = string.Empty;

                                string tblhaschcode = string.Empty;

                                tblhaschcode = file.GetHashCode().ToString();

                                tblFileName = file.Name.ToString();
                                tblRemotePath = file.FullName.ToString();


                                using (var fs = new FileStream(localPath + file.Name, FileMode.Create, FileAccess.Write))
                                {
                                    if (!file.IsDirectory && !file.IsSymbolicLink)
                                    {
                                        client.DownloadFile(file.FullName, fs);



                                        program.InsertIntoTable(tblFileName, tblhaschcode, tblRemotePath);
                                    }
                                    else if (file.Name != "." && file.Name != "..")
                                    {
                                        var dir = Directory.CreateDirectory(Path.Combine(localPath, file.Name));
                                    }


                                }
                            }

                        }


                    }
                }


            }
            catch (Exception)
            {

                throw;
            }

        }

 protected virtual byte[] Gethash(byte[] hashData)
        {
            using (var sha1 = new Renci.SshNet.Security.Cryptography.SHA1Hash())
            {
                return sha1.ComputeHash(hashData, 0, hashData.Length);
            }
        }


public void InsertIntoTable(string _imageName, string _hashcode, string _remotePath)
        {

            string sqlcon = ConfigurationManager.ConnectionStrings["sqlConn"].ToString();

            string insertCommand = ConfigurationManager.AppSettings["InsertintoImagetable"].ToString();

            using (SqlConnection conn = new SqlConnection(sqlcon))
            using (SqlCommand sql = new SqlCommand(insertCommand, conn))

            {
                sql.Parameters.AddWithValue("@_imagename", _imageName);
                sql.Parameters.AddWithValue("@_hashcode", _hashcode);
                sql.Parameters.AddWithValue("@_remotepath", _remotePath);

                foreach( SqlParameter parameter in sql.Parameters)
                {
                    if(parameter.Value == null)
                    {
                        parameter.Value = DBNull.Value;
                    }


                    conn.Open();
                    sql.ExecuteNonQuery();
                    conn.Close();

                    break;
               }

           }

       }

    }
}

我试图将文件传递给一种方法来计算我在处理sftp文件时遇到的困难。我找不到将sftp文件转换为字节或普通文件的方法。

public static string Gethash(SftpFile file)
{

    using (FileStream stream = File.OpenRead(actual))
    {
        var sha = new SHA256Managed();
        byte[] checksum = sha.ComputeHash(stream);
        return BitConverter.ToString(checksum).Replace("-", string.Empty);
    }
}

我的目标是从远程sftp服务器获取要下载的文件的哈希码，并与哈希表进行比较，仅当哈希表中没有哈希表时才下载。