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bug#40354: [PATCH] Fix Libravatar federation handling
From: |
Philip K |
Subject: |
bug#40354: [PATCH] Fix Libravatar federation handling |
Date: |
Tue, 31 Mar 2020 20:03:24 +0200 |
Previous implementation didn't correctly handle the result of
dns-query, and didn't implement the necessary record selection
algorithm as specified on the wiki (https://wiki.libravatar.org/api/,
"Federated servers").
* lisp/image/gravatar.el (gravatar--service-libravatar): Fix
libravatar image host resolver algorithm.
---
lisp/image/gravatar.el | 34 +++++++++++++++++++++++++++++-----
1 file changed, 29 insertions(+), 5 deletions(-)
diff --git a/lisp/image/gravatar.el b/lisp/image/gravatar.el
index ff59a72ac8..a2207af962 100644
--- a/lisp/image/gravatar.el
+++ b/lisp/image/gravatar.el
@@ -149,13 +149,36 @@ gravatar--service-libravatar
(dolist (record '(("_avatars-sec" . "https")
("_avatars" . "http")))
(let* ((query (concat (car record) "._tcp." domain))
- (result (dns-query query 'SRV)))
+ (result (dns-query query 'SRV t)))
(when result
- (throw 'found (format "%s://%s/avatar"
- (cdr record)
- result)))))
- "https://seccdn.libravatar.org/avatar")))))
+ (let* ((res (mapcar (lambda (rec)
+ (dns-get 'data (cdr rec)))
+ (dns-get 'answers result)))
+ (prio
+ (mapcar (lambda (r) (dns-get 'priority r)) res))
+ (max (apply #'max prio))
+ (sum 0) top)
+ ;; Attempt to find all records with the same maximal
+ ;; priority, and calculate the sum of their weights.
+ (dolist (rec res)
+ (when (= max (dns-get 'priority rec))
+ (setq sum (+ sum (dns-get 'weight rec)))
+ (push rec top)))
+ ;; In case there is more than one maximal priority
+ ;; record, choose one at random, while taking the
+ ;; individual record weights into consideration.
+ (dolist (rec top)
+ (when (and (<= (if (= 0 sum) -1 (random sum))
+ (dns-get 'weight rec))
+ (<= 1 (dns-get 'port rec) 65535)
+ (string-match-p "\\`[-.0-9A-Za-z]+\\'"
+ (dns-get 'target rec)))
+ (throw 'found (format "%s://%s:%s/avatar"
+ (cdr record)
+ (dns-get 'target rec)
+ (dns-get 'port rec))))
+ (setq sum (- sum (dns-get 'weight rec)))))))
+ "https://seccdn.libravatar.org/avatar"))))))
(defun gravatar-hash (mail-address)
"Return the Gravatar hash for MAIL-ADDRESS."
--
2.20.1
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