如何在不回显的情况下从套接字获取输入？

Question

我正在用 Ruby 创建一个 TCP 服务器，需要从用户那里获取密码。此密码不应回显。不幸的是，当我 telnet 到 8080 端口并输入：My password is echoed.

@server_socket = TCPServer.open(8080, localhost)
conn = @server_socket.accept
conn.write "Password: "
conn.gets.chomp # <-- This should not be visible

当我输入 telnet localhost 8080 时，我可以在屏幕上看到我的密码。

Answer 1

你必须向客户端发送正确的字节序列，告诉它抑制本地回显。这些在RFC857 中有描述。

我看着通过a 987654323 of 987654325 on 987654327 to 987654329 this 987654331 it's 987654333 very简单。不过，这就是最终的工作：

require 'socket'

server = TCPServer.open(2000)
client = server.accept

# Send the IAC DONT ECHO byte sequence
client.write "#{255.chr}#{254.chr}#{1.chr}"
# Send the IAC WILL ECHO byte sequence
client.write "#{255.chr}#{251.chr}#{1.chr}"

client.write 'Enter any text and it will not echo locally: '
text = client.gets.chomp
client.write "\r\n"
client.write "The text entered while echo was suppressed was #{text}\r\n"

# Send the IAC DO ECHO byte sequence
client.write "#{255.chr}#{253.chr}#{1.chr}"
# Send the IAC WONT ECHO byte sequence
client.write "#{255.chr}#{252.chr}#{1.chr}"

client.write 'Local echo has been re-enabled, enter any text: '
client.gets.chomp

client.close

telnet客户端的输出是：

telnet localhost 2000
Trying ::1...
Connected to localhost.
Escape character is '^]'.
Enter any text and it will not echo locally:
The text entered while echo was suppressed was foo
Local echo has been re-enabled, enter any text: bar
Connection closed by foreign host.

此解决方案取决于支持这些模式的客户端 telnet 应用程序，并在请求时尊重它们。不能保证客户会尊重他们。