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Diffstat (limited to 'lisp/gnus/gnus-util.el')
| -rw-r--r-- | lisp/gnus/gnus-util.el | 47 |
1 files changed, 47 insertions, 0 deletions
diff --git a/lisp/gnus/gnus-util.el b/lisp/gnus/gnus-util.el index aa9f137e203..f8126906b87 100644 --- a/lisp/gnus/gnus-util.el +++ b/lisp/gnus/gnus-util.el @@ -1343,6 +1343,53 @@ forbidden in URL encoding." (setq tmp (concat tmp str)) tmp)) +(defun gnus-base64-repad (str &optional reject-newlines line-length) + "Take a base 64-encoded string and return it padded correctly. +Existing padding is ignored. + +If any combination of CR and LF characters are present and +REJECT-NEWLINES is nil, remove them; otherwise raise an error. +If LINE-LENGTH is set and the string (or any line in the string +if REJECT-NEWLINES is nil) is longer than that number, raise an +error. Common line length for input characters are 76 plus CRLF +(RFC 2045 MIME), 64 plus CRLF (RFC 1421 PEM), and 1000 including +CRLF (RFC 5321 SMTP)." + ;; RFC 4648 specifies that: + ;; - three 8-bit inputs make up a 24-bit group + ;; - the 24-bit group is broken up into four 6-bit values + ;; - each 6-bit value is mapped to one character of the base 64 alphabet + ;; - if the final 24-bit quantum is filled with only 8 bits the output + ;; will be two base 64 characters followed by two "=" padding characters + ;; - if the final 24-bit quantum is filled with only 16 bits the output + ;; will be three base 64 character followed by one "=" padding character + ;; + ;; RFC 4648 section 3 considerations: + ;; - if reject-newlines is nil (default), concatenate multi-line + ;; input (3.1, 3.3) + ;; - if line-length is set, error on input exceeding the limit (3.1) + ;; - reject characters outside base encoding (3.3, also section 12) + (let ((splitstr (split-string str "[\r\n]" t))) + (when (and reject-newlines (> (length splitstr) 1)) + (error "Invalid Base64 string")) + (dolist (substr splitstr) + (when (and line-length (> (length substr) line-length)) + (error "Base64 string exceeds line-length")) + (when (string-match "[^A-Za-z0-9+/=]" substr) + (error "Invalid Base64 string"))) + (let* ((str (string-join splitstr)) + (len (length str))) + (when (string-match "=" str) + (setq len (match-beginning 0))) + (concat + (substring str 0 len) + (make-string (/ + (- 24 + (pcase (mod (* len 6) 24) + (`0 24) + (n n))) + 6) + ?=))))) + (defun gnus-make-predicate (spec) "Transform SPEC into a function that can be called. SPEC is a predicate specifier that contains stuff like `or', `and', |