使用SSH.NET连接服务器遇Connection reset by peer异常求助

使用SSH.NET连接两台服务器时，其中一台可正常运行，但连接另一台时抛出Connection reset by peer异常。已通过CLI执行ssh user@host命令，用相同密钥可正常连接两台服务器。

错误信息 #

Unhandled exception. Renci.SshNet.Common.SshConnectionException: Connection reset by peer
 ---> System.Net.Sockets.SocketException (104): Connection reset by peer
   at System.Net.Sockets.Socket.Receive(Byte[] buffer, Int32 offset, Int32 size, SocketFlags socketFlags)
   at Renci.SshNet.Abstractions.SocketAbstraction.Read(Socket socket, Byte[] buffer, Int32 offset, Int32 size, TimeSpan timeout)
   at Renci.SshNet.Session.TrySocketRead(Byte[] buffer, Int32 offset, Int32 length)
   at Renci.SshNet.Session.ReceiveMessage()
   at Renci.SshNet.Session.MessageListener()
   --- End of inner exception stack trace ---
   at Renci.SshNet.Session.WaitOnHandle(WaitHandle waitHandle, TimeSpan timeout)
   at Renci.SshNet.Session.WaitOnHandle(WaitHandle waitHandle)
   at Renci.SshNet.Session.Connect()
   at Renci.SshNet.BaseClient.CreateAndConnectSession()
   at Renci.SshNet.BaseClient.Connect()

代码示例 #

var keyStr = File.ReadAllText("/home/me/.ssh/id_rsa");

PrivateKeyFile privateKey = null;

using (var keystrm = new MemoryStream(Encoding.ASCII.GetBytes(keyStr)))
{
     privateKey = new PrivateKeyFile(keystrm);
}

var keyFiles = new[] { privateKey };


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

var con = new ConnectionInfo("...", 22, "root", methods.ToArray());

using var sshClient = new SshClient(con);
sshClient.Connect();

• 修正用户名不匹配问题：代码中PrivateKeyAuthenticationMethod使用的用户名是"me"，但ConnectionInfo里的用户名是"root"，而CLI连接用的是user@host。SSH密钥认证与用户绑定，服务器端authorized_keys通常存储在对应用户的.ssh目录下，需确保代码中ConnectionInfo的用户名和CLI连接时一致。
• 修复密钥编码问题：用Encoding.ASCII读取密钥文件可能导致编码错误，建议直接读取字节流避免编码问题：

  var keyBytes = File.ReadAllBytes("/home/me/.ssh/id_rsa");
  using (var keystrm = new MemoryStream(keyBytes))
  {
       privateKey = new PrivateKeyFile(keystrm);
  }
  

• 添加超时与调试日志：设置连接超时并启用错误日志，便于排查连接过程中的细节：

  con.Timeout = TimeSpan.FromSeconds(30);
  sshClient.ErrorOccurred += (sender, e) => Console.WriteLine($"SSH Error: {e.Exception.Message}");
  

• 检查服务器SSH配置：
  • 确认目标服务器sshd_config中PermitRootLogin是否允许root用户登录，若CLI用非root用户，代码中也需保持一致。
  • 若服务器限制了SSH算法，可手动指定支持的密钥交换算法：

    var con = new ConnectionInfo("...", 22, "me", new[] {
        new PrivateKeyAuthenticationMethod("me", keyFiles)
    })
    {
        KeyExchangeAlgorithms = new List<string> { "diffie-hellman-group-exchange-sha256" }
    };
    

内容的提问来源于stack exchange，提问作者user5405648