.NET 8使用SFTP传文件时遇ECDiffieHellman算法不支持异常

此前SFTP文件传输功能正常，迁移至.NET 8后触发以下异常：

Negotiation failed. Unsupported instance of ECDiffieHellman algorithm.

请问在.NET 8环境下使用SFTP是否需要特定配置来修复该问题？

参考代码片段 #

using (var client = new Sftp())
{
    var privateKey = KeyFromString(Configuration.KeyString);
    var stream = StreamFromString(contents);
    client.Connect(Configuration.Url, Configuration.Port);
    client.Login(Configuration.User, Configuration.Password, privateKey);
    client.PutFile(stream, filename);
}

已尝试查找.NET 8下SFTP的相关指南，但未找到有效解决信息。

脱敏后的堆栈跟踪信息 #

Inner exception Rebex.Net.SftpException handled at PutFile:
   at Rebex.Net.Sftp.viema (Rebex.Sftp undefined, Version=5.0.7733.0 undefined, Culture=neutral undefined, PublicKeyToken=1c4638788972655d undefined)
   at Rebex.Net.Sftp.mksfi (Rebex.Sftp undefined, Version=5.0.7733.0 undefined, Culture=neutral undefined, PublicKeyToken=1c4638788972655d undefined)
   at Rebex.Net.Sftp.Connect (Rebex.Sftp undefined, Version=5.0.7733.0 undefined, Culture=neutral undefined, PublicKeyToken=1c4638788972655d undefined)
   at PutFile 
Inner exception Rebex.Net.SshException handled at Rebex.Net.Sftp.viema:
   at Rebex.Net.SshSession.lawoz (Rebex.Networking undefined, Version=5.0.7733.0 undefined, Culture=neutral undefined, PublicKeyToken=1c4638788972655d undefined)
   at Rebex.Net.SshSession.Negotiate (Rebex.Networking undefined, Version=5.0.7733.0 undefined, Culture=neutral undefined, PublicKeyToken=1c4638788972655d undefined)
   at Rebex.Net.Sftp+ymnzg.zbkwa.igvda (Rebex.Sftp undefined, Version=5.0.7733.0 undefined, Culture=neutral undefined, PublicKeyToken=1c4638788972655d undefined)
   at Rebex.Net.Sftp.viema (Rebex.Sftp undefined, Version=5.0.7733.0 undefined, Culture=neutral undefined, PublicKeyToken=1c4638788972655d undefined)
Inner exception System.Security.Cryptography.CryptographicException handled at Rebex.Net.SshSession.lawoz:
   at ymnzg.aoqsw.kaxgn (Rebex.Common undefined, Version=5.0.7733.0 undefined, Culture=neutral undefined, PublicKeyToken=1c4638788972655d undefined)
   at ymnzg.aoqsw.kiovp (Rebex.Common undefined, Version=5.0.7733.0 undefined, Culture=neutral undefined, PublicKeyToken=1c4638788972655d undefined)
   at ymnzg.lmfzi.bltdt (Rebex.Common undefined, Version=5.0.7733.0 undefined, Culture=neutral undefined, PublicKeyToken=1c4638788972655d undefined)
   at Rebex.Security.Cryptography.AsymmetricKeyAlgorithm.scqfy (Rebex.Common undefined, Version=5.0.7733.0 undefined, Culture=neutral undefined, PublicKeyToken=1c4638788972655d undefined)
   at ymnzg.yajog.dlafz (Rebex.Networking undefined, Version=5.0.7733.0 undefined, Culture=neutral undefined, PublicKeyToken=1c4638788972655d undefined)
   at Rebex.Net.SshSession.lawoz (Rebex.Networking undefined, Version=5.0.7733.0 undefined, Culture=neutral undefined, PublicKeyToken=1c4638788972655d undefined)

解决方案 #

从堆栈信息看，你使用的是Rebex SFTP库（版本5.0.7733），这个版本在.NET 8下存在ECDiffieHellman算法兼容问题，可通过以下两种方式修复：

1. 升级Rebex SFTP库版本
   Rebex在2023 R3及后续版本中已适配.NET 8的密码学API变更，升级到最新版本可直接解决该兼容性问题。

2. 显式配置密钥交换算法或强制使用内置加密实现

• 方式一：指定兼容的密钥交换算法，在Connect调用前添加配置：

// 配置使用兼容的密钥交换算法
client.Settings.SshParameters.KeyExchangeAlgorithms = new[] { 
    "diffie-hellman-group-exchange-sha256", 
    "ecdh-sha2-nistp256" 
};

• 方式二：强制Rebex使用自身内置的加密实现，绕过系统的ECDiffieHellman API：

// 在初始化客户端前设置
Rebex.Security.Cryptography.CryptoHelper.UseManagedProviders = true;

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