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87 lines
2.4 KiB
87 lines
2.4 KiB
# frozen_string_literal: true
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# Implemented according to HTTP signatures (Draft 6)
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# <https://tools.ietf.org/html/draft-cavage-http-signatures-06>
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module SignatureVerification
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extend ActiveSupport::Concern
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def signed_request?
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request.headers['Signature'].present?
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end
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def signed_request_account
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return @signed_request_account if defined?(@signed_request_account)
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unless signed_request?
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@signed_request_account = nil
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return
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end
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raw_signature = request.headers['Signature']
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signature_params = {}
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raw_signature.split(',').each do |part|
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parsed_parts = part.match(/([a-z]+)="([^"]+)"/i)
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next if parsed_parts.nil? || parsed_parts.size != 3
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signature_params[parsed_parts[1]] = parsed_parts[2]
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end
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if incompatible_signature?(signature_params)
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@signed_request_account = nil
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return
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end
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account = ResolveRemoteAccountService.new.call(signature_params['keyId'].gsub(/\Aacct:/, ''))
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if account.nil?
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@signed_request_account = nil
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return
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end
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signature = Base64.decode64(signature_params['signature'])
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compare_signed_string = build_signed_string(signature_params['headers'])
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if account.keypair.public_key.verify(OpenSSL::Digest::SHA256.new, signature, compare_signed_string)
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@signed_request_account = account
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@signed_request_account
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else
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@signed_request_account = nil
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end
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end
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private
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def build_signed_string(signed_headers)
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signed_headers = 'date' if signed_headers.blank?
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signed_headers.split(' ').map do |signed_header|
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if signed_header == Request::REQUEST_TARGET
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"#{Request::REQUEST_TARGET}: #{request.method.downcase} #{request.path}"
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else
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"#{signed_header}: #{request.headers[to_header_name(signed_header)]}"
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end
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end.join("\n")
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end
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def matches_time_window?
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begin
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time_sent = DateTime.httpdate(request.headers['Date'])
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rescue ArgumentError
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return false
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end
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(Time.now.utc - time_sent).abs <= 30
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end
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def to_header_name(name)
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name.split(/-/).map(&:capitalize).join('-')
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end
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def incompatible_signature?(signature_params)
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signature_params['keyId'].blank? ||
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signature_params['signature'].blank? ||
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signature_params['algorithm'].blank? ||
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signature_params['algorithm'] != 'rsa-sha256' ||
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!signature_params['keyId'].start_with?('acct:')
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end
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end
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