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202 lines
6.2 KiB
Markdown
202 lines
6.2 KiB
Markdown
[#]: collector: (lujun9972)
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[#]: translator: (geekpi)
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[#]: reviewer: (wxy)
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[#]: publisher: (wxy)
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[#]: url: (https://linux.cn/article-10945-1.html)
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[#]: subject: (Securing telnet connections with stunnel)
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[#]: via: (https://fedoramagazine.org/securing-telnet-connections-with-stunnel/)
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[#]: author: (Curt Warfield https://fedoramagazine.org/author/rcurtiswarfield/)
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使用 stunnel 保护 telnet 连接
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======
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![][1]
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Telnet 是一种客户端-服务端协议，通过 TCP 的 23 端口连接到远程服务器。Telnet 并不加密数据，因此它被认为是不安全的，因为数据是以明文形式发送的，所以密码很容易被嗅探。但是，仍有老旧系统需要使用它。这就是用到 **stunnel** 的地方。
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stunnel 旨在为使用不安全连接协议的程序增加 SSL 加密。本文将以 telnet 为例介绍如何使用它。
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### 服务端安装
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[使用 sudo][2] 安装 stunnel 以及 telnet 的服务端和客户端：
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```
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sudo dnf -y install stunnel telnet-server telnet
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```
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添加防火墙规则，在提示时输入你的密码：
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```
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firewall-cmd --add-service=telnet --perm
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firewall-cmd --reload
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```
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接下来，生成 RSA 私钥和 SSL 证书：
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```
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openssl genrsa 2048 > stunnel.key
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openssl req -new -key stunnel.key -x509 -days 90 -out stunnel.crt
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```
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系统将一次提示你输入以下信息。当询问 `Common Name` 时，你必须输入正确的主机名或 IP 地址，但是你可以按回车键跳过其他所有内容。
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```
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You are about to be asked to enter information that will be
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incorporated into your certificate request.
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What you are about to enter is what is called a Distinguished Name or a DN.
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There are quite a few fields but you can leave some blank
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For some fields there will be a default value,
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If you enter '.', the field will be left blank.
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-----
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Country Name (2 letter code) [XX]:
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State or Province Name (full name) []:
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Locality Name (eg, city) [Default City]:
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Organization Name (eg, company) [Default Company Ltd]:
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Organizational Unit Name (eg, section) []:
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Common Name (eg, your name or your server's hostname) []:
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Email Address []
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```
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将 RSA 密钥和 SSL 证书合并到单个 `.pem` 文件中，并将其复制到 SSL 证书目录：
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```
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cat stunnel.crt stunnel.key > stunnel.pem
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sudo cp stunnel.pem /etc/pki/tls/certs/
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```
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现在可以定义服务和用于加密连接的端口了。选择尚未使用的端口。此例使用 450 端口进行隧道传输 telnet。编辑或创建 `/etc/stunnel/telnet.conf`：
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```
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cert = /etc/pki/tls/certs/stunnel.pem
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sslVersion = TLSv1
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chroot = /var/run/stunnel
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setuid = nobody
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setgid = nobody
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pid = /stunnel.pid
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socket = l:TCP_NODELAY=1
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socket = r:TCP_NODELAY=1
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[telnet]
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accept = 450
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connect = 23
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```
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`accept` 选项是服务器将监听传入 telnet 请求的接口。`connect` 选项是 telnet 服务器的内部监听接口。
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接下来，创建一个 systemd 单元文件的副本来覆盖原来的版本：
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```
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sudo cp /usr/lib/systemd/system/stunnel.service /etc/systemd/system
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```
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编辑 `/etc/systemd/system/stunnel.service` 来添加两行。这些行在启动时为服务创建 chroot 监狱。
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```
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[Unit]
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Description=TLS tunnel for network daemons
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After=syslog.target network.target
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[Service]
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ExecStart=/usr/bin/stunnel
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Type=forking
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PrivateTmp=true
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ExecStartPre=-/usr/bin/mkdir /var/run/stunnel
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ExecStartPre=/usr/bin/chown -R nobody:nobody /var/run/stunnel
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[Install]
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WantedBy=multi-user.target
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```
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接下来，配置 SELinux 以在你刚刚指定的新端口上监听 telnet：
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```
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sudo semanage port -a -t telnetd_port_t -p tcp 450
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```
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最后，添加新的防火墙规则：
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```
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firewall-cmd --add-port=450/tcp --perm
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firewall-cmd --reload
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```
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现在你可以启用并启动 telnet 和 stunnel。
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```
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systemctl enable telnet.socket stunnel@telnet.service --now
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```
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要注意 `systemctl` 命令是有顺序的。systemd 和 stunnel 包默认提供额外的[模板单元文件][3]。该模板允许你将 stunnel 的多个配置文件放到 `/etc/stunnel` 中，并使用文件名启动该服务。例如，如果你有一个 `foobar.conf` 文件，那么可以使用 `systemctl start stunnel@foobar.service` 启动该 stunnel 实例，而无需自己编写任何单元文件。
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如果需要，可以将此 stunnel 模板服务设置为在启动时启动：
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```
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systemctl enable stunnel@telnet.service
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```
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### 客户端安装
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本文的这部分假设你在客户端系统上以普通用户（[拥有 sudo 权限][2]）身份登录。安装 stunnel 和 telnet 客户端：
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```
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dnf -y install stunnel telnet
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```
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将 `stunnel.pem` 从远程服务器复制到客户端的 `/etc/pki/tls/certs` 目录。在此例中，远程 telnet 服务器的 IP 地址为 `192.168.1.143`。
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```
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sudo scp myuser@192.168.1.143:/etc/pki/tls/certs/stunnel.pem
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/etc/pki/tls/certs/
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```
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创建 `/etc/stunnel/telnet.conf`：
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```
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cert = /etc/pki/tls/certs/stunnel.pem
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client=yes
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[telnet]
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accept=450
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connect=192.168.1.143:450
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```
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`accept` 选项是用于 telnet 会话的端口。`connect` 选项是你远程服务器的 IP 地址以及监听的端口。
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接下来，启用并启动 stunnel：
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```
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systemctl enable stunnel@telnet.service --now
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```
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测试你的连接。由于有一条已建立的连接，你会 `telnet` 到 `localhost` 而不是远程 telnet 服务器的主机名或者 IP 地址。
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```
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[user@client ~]$ telnet localhost 450
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Trying ::1...
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telnet: connect to address ::1: Connection refused
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Trying 127.0.0.1...
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Connected to localhost.
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Escape character is '^]'.
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Kernel 5.0.9-301.fc30.x86_64 on an x86_64 (0)
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server login: myuser
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Password: XXXXXXX
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Last login: Sun May 5 14:28:22 from localhost
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[myuser@server ~]$
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```
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--------------------------------------------------------------------------------
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via: https://fedoramagazine.org/securing-telnet-connections-with-stunnel/
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作者：[Curt Warfield][a]
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选题：[lujun9972][b]
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译者：[geekpi](https://github.com/geekpi)
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校对：[wxy](https://github.com/wxy)
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本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出
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[a]: https://fedoramagazine.org/author/rcurtiswarfield/
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[b]: https://github.com/lujun9972
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[1]: https://fedoramagazine.org/wp-content/uploads/2019/05/stunnel-816x345.jpg
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[2]: https://fedoramagazine.org/howto-use-sudo/
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[3]: https://fedoramagazine.org/systemd-template-unit-files/
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