85 lines
		
	
	
	
		
			3.3 KiB
		
	
	
	
		
			Common Lisp
		
	
	
	
	
	
			
		
		
	
	
			85 lines
		
	
	
	
		
			3.3 KiB
		
	
	
	
		
			Common Lisp
		
	
	
	
	
	
;; Implementation of a DoH-client, see RFC 8484 (DNS Queries over
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;; HTTPS (DoH))
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(in-package #:dns)
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(defvar *doh-base-url* "https://dns.google/resolve"
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  "Base URL of the service providing DNS-over-HTTP(S). Defaults to the
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  Google-hosted API.")
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(define-condition doh-error (error)
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  ((query-name :initarg :query-name
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               :reader doh-error-query-name
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               :type string)
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   (query-type :initarg :query-type
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               :reader doh-error-query-type
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               :type string)
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   (doh-url :initarg :doh-url
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            :reader doh-error-doh-url
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            :type string)
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   (status-code :initarg :status-code
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                :reader doh-error-status-code
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                :type integer)
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   (response-body :initarg :response-body
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                  :reader doh-error-response-body
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                  :type (or nil (vector (unsigned-byte 8)) string)))
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  (:report (lambda (condition stream)
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             (let ((url (doh-error-doh-url condition))
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                   (status (doh-error-status-code condition))
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                   (body (doh-error-response-body condition)))
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               (format stream "DoH service at '~A' responded with non-success (~A): ~%~%~A"
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                       url status body)))))
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(defun lookup-generic (name type doh-url)
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  (multiple-value-bind (body status)
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      (drakma:http-request doh-url
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                           :decode-content t
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                           ;; TODO(tazjin): Figure out why 'want-stream' doesn't work
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                           :parameters `(("type" . ,type)
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                                         ("name" . ,name)
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                                         ("ct" . "application/dns-message")))
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    (if (= 200 status)
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        (dns-message-answer
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         (read-binary 'dns-message (flexi-streams:make-in-memory-input-stream body)))
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        (restart-case (error 'doh-error
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                             :query-name name
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                             :query-type type
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                             :doh-url doh-url
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                             :status-code status
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                             :response-body body)
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          (call-with-other-name (new-name)
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            :interactive (lambda () (list (the string (read))))
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            :test (lambda (c) (typep c 'doh-error))
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            (lookup-generic new-name type doh-url))
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          (call-with-other-type (new-type)
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            :interactive (lambda () (list (the string (read))))
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            :test (lambda (c) (typep c 'doh-error))
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            (lookup-generic name new-type doh-url))
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          (call-with-other-url (new-url)
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            :interactive (lambda () (list (the string (read))))
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            :test (lambda (c) (typep c 'doh-error))
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            (lookup-generic name type new-url))))))
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(defun lookup-a (name &key (doh-url *doh-base-url*))
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  "Look up the A records at NAME."
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  (lookup-generic name "A" doh-url))
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(defun lookup-txt (name &key (doh-url *doh-base-url*))
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  "Look up the TXT records at NAME."
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  (lookup-generic name "TXT" doh-url))
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(defun lookup-mx (name &key (doh-url *doh-base-url*))
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  "Look up the MX records at NAME."
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  (lookup-generic name "MX" doh-url))
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(defun lookup-cname (name &key (doh-url *doh-base-url*))
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  "Look up the CNAME records at NAME."
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  (lookup-generic name "CNAME" doh-url))
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(defun lookup-ns (name &key (doh-url *doh-base-url*))
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  "Look up the NS records at NAME."
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  (lookup-generic name "NS" doh-url))
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