73 lines
2.2 KiB
Ruby
73 lines
2.2 KiB
Ruby
require 'digest/md5'
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module EventMachine::WebSocket
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module Handshake76
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class << self
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def handshake(headers, path, secure)
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challenge_response = solve_challenge(
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headers['sec-websocket-key1'],
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headers['sec-websocket-key2'],
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headers['third-key']
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)
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scheme = (secure ? "wss" : "ws")
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location = "#{scheme}://#{headers['host']}#{path}"
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upgrade = "HTTP/1.1 101 WebSocket Protocol Handshake\r\n"
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upgrade << "Upgrade: WebSocket\r\n"
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upgrade << "Connection: Upgrade\r\n"
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upgrade << "Sec-WebSocket-Location: #{location}\r\n"
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upgrade << "Sec-WebSocket-Origin: #{headers['origin']}\r\n"
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if protocol = headers['sec-websocket-protocol']
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validate_protocol!(protocol)
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upgrade << "Sec-WebSocket-Protocol: #{protocol}\r\n"
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end
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upgrade << "\r\n"
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upgrade << challenge_response
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return upgrade
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end
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private
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def solve_challenge(first, second, third)
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# Refer to 5.2 4-9 of the draft 76
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sum = [numbers_over_spaces(first)].pack("N*") +
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[numbers_over_spaces(second)].pack("N*") +
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third
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Digest::MD5.digest(sum)
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end
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def numbers_over_spaces(string)
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unless string
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raise HandshakeError, "WebSocket key1 or key2 is missing"
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end
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numbers = string.scan(/[0-9]/).join.to_i
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spaces = string.scan(/ /).size
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# As per 5.2.5, abort the connection if spaces are zero.
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raise HandshakeError, "Websocket Key1 or Key2 does not contain spaces - this is a symptom of a cross-protocol attack" if spaces == 0
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# As per 5.2.6, abort if numbers is not an integral multiple of spaces
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if numbers % spaces != 0
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raise HandshakeError, "Invalid Key #{string.inspect}"
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end
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quotient = numbers / spaces
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if quotient > 2**32-1
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raise HandshakeError, "Challenge computation out of range for key #{string.inspect}"
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end
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return quotient
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end
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def validate_protocol!(protocol)
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raise HandshakeError, "Invalid WebSocket-Protocol: empty" if protocol.empty?
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# TODO: Validate characters
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end
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end
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end
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end
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