AI 优化 ssh 客户端配置文件 ssh config

海云青飞 让 AI 帮忙优化 Ubuntu 服务器上的 ssh 配置文件 /etc/ssh/sshd_config 后，就继续让他优化 ssh 客户端的配置文件 ~/.ssh/config 文件

AI 优化后的 ~/.ssh/config

Host *
    # Keep the server connection alive, but reduce timeouts for faster detection of dead sessions
    ServerAliveCountMax 2
    ServerAliveInterval 240

    # Preferred authentication method
    PreferredAuthentications publickey

    # IPv4 only
    # AddressFamily inet  # Keep this if you only want to use IPv4. If you want both IPv4 and IPv6, remove this line.

    # Compression can improve speed on low-bandwidth connections but may increase CPU usage
    Compression yes

    # Disable TCP keep-alive probes
    TCPKeepAlive no

    # Improve logging level for better security insights
    LogLevel VERBOSE

    # 注：Windows 开启下面设置可能无效并导致需要重新连接。在我的电脑上需要禁用这些设置
    # Enable control master for faster subsequent connections
    ControlMaster auto
    ControlPath ~/.ssh/sockets/%r@%h:%p
    # Keep the master connection open for 10 minutes
    ControlPersist 10m

    # 注：开启以下设置可能导致 ssh 连接路由器失败，因为路由器可能不支持下面的加密协议
    # Modern, fast, and secure ciphers and key exchange algorithms
    Ciphers aes256-gcm@openssh.com,chacha20-poly1305@openssh.com
    KexAlgorithms curve25519-sha256,curve25519-sha256@libssh.org
    MACs hmac-sha2-512-etm@openssh.com,hmac-sha2-256-etm@openssh.com,umac-128-etm@openssh.com

    # Restrict key sizes to modern standards
    PubkeyAcceptedKeyTypes ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,ssh-ed25519,rsa-sha2-512,rsa-sha2-256

要注意的是，如果启用 ControlMaste，要确保 ~/.ssh/sockets 文件夹的存在，如果不存在，就要手动创建它

海云青飞 请 AI 优化 ssh client side ~/.ssh/config

Optimize ssh local configuration to improve speed and security, remove unnecessary or outdated settings

ssh version: OpenSSH_8.1p1, OpenSSL 1.1.1b 26 Feb 2019

current .ssh/config:

Host *
    Protocol 2
    ServerAliveCountMax 2
    ServerAliveInterval 300
    PreferredAuthentications publickey
    AddressFamily inet
    Compression yes
    TCPKeepAlive no
    LogLevel INFO

AI 对 ssh 客户端配置文件 ~/.ssh/config 的优化建议

ChatGPT-4o-Latest 回复：

To optimize your local SSH configuration both for speed and security, we'll remove outdated settings, improve security with modern cryptographic algorithms, and tweak options that can enhance connection speed. Here is the suggested optimization for your .ssh/config file:

Optimized .ssh/config:

Host *
    # No need to specify Protocol 2, as it's the default since OpenSSH 7.2
    # Protocol 2 (removed)

    # Keep the server connection alive, but reduce timeouts for faster detection of dead sessions
    ServerAliveCountMax 2
    ServerAliveInterval 240  # Reduced to 4 minutes to detect connection issues faster

    # Preferred authentication method
    PreferredAuthentications publickey  # Keep public key authentication for security

    # IPv4 only
    AddressFamily inet  # Keep this if you only want to use IPv4. If you want both IPv4 and IPv6, remove this line

    # Compression can improve speed on low-bandwidth connections but may increase CPU usage
    Compression yes  # Keep compression enabled for slower connections or remove if on a fast network

    # Disable TCP keep-alive probes
    TCPKeepAlive no  # Keep disabled for security and to avoid leaking information about active SSH connections

    # Improve logging level for better security insights
    LogLevel VERBOSE  # Increased log level to capture more detailed logs

    # Enable control master for faster subsequent connections
    ControlMaster auto
    ControlPath ~/.ssh/sockets/%r@%h:%p
    ControlPersist 10m  # Keep the master connection open for 10 minutes

    # Modern, fast, and secure ciphers and key exchange algorithms
    Ciphers aes256-gcm@openssh.com,chacha20-poly1305@openssh.com
    KexAlgorithms curve25519-sha256,curve25519-sha256@libssh.org
    MACs hmac-sha2-512-etm@openssh.com,hmac-sha2-256-etm@openssh.com,umac-128-etm@openssh.com

    # Restrict key sizes to modern standards
    PubkeyAcceptedKeyTypes ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,ssh-ed25519,rsa-sha2-512,rsa-sha2-256

Key Changes and Explanation:

  1. Removed Protocol 2:

    • You specified Protocol 2, but since OpenSSH 7.2, Protocol 2 is the default and Protocol 1 is deprecated and insecure. This line can be safely removed

  2. Adjusted ServerAliveInterval:

    • Reduced ServerAliveInterval from 300 to 240 seconds (4 minutes). This slightly reduces the time the client waits before sending a keep-alive message, allowing faster detection of dead connections

  3. Kept PreferredAuthentications publickey:

    • Public key authentication is more secure than password-based methods. Keeping PreferredAuthentications publickey ensures that SSH tries public key authentication first

  4. Consideration for AddressFamily inet:

    • If you want to restrict SSH to IPv4 connections only, keep AddressFamily inet. If you want to support both IPv4 and IPv6, you can remove this line. If you disable IPv6 support on your system, keeping this line will slightly improve connection speed

  5. Kept Compression yes:

    • Compression can improve speed on low-bandwidth connections but may increase CPU usage. Keep it enabled if you frequently connect over slower networks (like remote servers). If you are on a fast, low-latency connection, you may see slightly better performance by removing this line

  6. Increased LogLevel to VERBOSE:

    • Increasing the log level to VERBOSE improves security auditing, providing more detailed information on SSH connection attempts and issues

  7. Enabled ControlMaster, ControlPath, and ControlPersist:

    • These options allow SSH to reuse an existing connection for subsequent logins to the same host, significantly improving speed when making multiple connections to the same server
    • ControlMaster auto: Enables the control master feature
    • ControlPath ~/.ssh/sockets/%r@%h:%p: Sets a path for the control socket. Ensure the ~/.ssh/sockets directory exists on your system (mkdir -p ~/.ssh/sockets)
    • ControlPersist 10m: Keeps the master connection open for 10 minutes after the last client disconnects, making subsequent connections faster

  8. Modern Cryptographic Algorithms:

    • Specifying modern ciphers, key exchange algorithms, and MACs ensures that SSH uses the most secure and fast cryptographic methods:
      • Ciphers: aes256-gcm@openssh.com and chacha20-poly1305@openssh.com are both fast and secure
      • KexAlgorithms: curve25519-sha256 ensures fast and secure key exchanges
      • MACs: Modern HMAC algorithms are more secure and efficient

  9. Restricted PubkeyAcceptedKeyTypes:

    • This restricts the accepted public key types to modern, strong algorithms like ecdsa, ed25519, and rsa-sha2. This ensures you're not using outdated or weak keys

Final Thoughts:

This optimized SSH client configuration improves both speed and security. The use of modern cryptographic algorithms enhances security, while enabling ControlMaster and related options improves connection speed when making multiple or repeated connections to the same server. Adjusting the server alive interval also helps detect problematic connections faster, while preserving security

Make sure to test your SSH connections after applying these changes to ensure everything works as expected

2024-09-08

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