* bug#43441: 27.1; [PATCH] Fix incorrectly base64-padded faces in gnus-convert-face-to-png
2020-09-17 15:31 ` Lars Ingebrigtsen
@ 2020-09-28 6:05 ` Alex Bochannek
2020-09-28 12:10 ` Lars Ingebrigtsen
0 siblings, 1 reply; 5+ messages in thread
From: Alex Bochannek @ 2020-09-28 6:05 UTC (permalink / raw)
To: Lars Ingebrigtsen; +Cc: 43441
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Lars Ingebrigtsen <larsi@gnus.org> writes:
> Alex Bochannek <alex@bochannek.com> writes:
>
>> I don't suspect this problem is widespread in other uses of the base64
>> decoder, so it seems appropriate to me to just patch
>> gnus-convert-face-to-png to generate the right amount of padding.
>
> Hm... I think it would be nice to have a utility function to fix up
> base64 padding, and then gnus-convert-face-to-png could just use that?
>
> It should work for both base64 that has newlines inserted and not.
Took me a little while, but I broke this out into a utility function as
you suggested. I also wrote some tests for it. As part of me getting
familiar with ERT, I added a bunch of tests for gnus-string< and
gnus-string>, which I hope are useful. They should probably be in a
separate commit, but I leave that up to you.
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diff --git a/lisp/gnus/gnus-fun.el b/lisp/gnus/gnus-fun.el
index c95449762e..2461fd45fd 100644
--- a/lisp/gnus/gnus-fun.el
+++ b/lisp/gnus/gnus-fun.el
@@ -205,11 +205,12 @@ gnus-face-encode
(defun gnus-convert-face-to-png (face)
"Convert FACE (which is base64-encoded) to a PNG.
The PNG is returned as a string."
- (mm-with-unibyte-buffer
- (insert face)
- (ignore-errors
- (base64-decode-region (point-min) (point-max)))
- (buffer-string)))
+ (let ((face (gnus-base64-repad face)))
+ (mm-with-unibyte-buffer
+ (insert face)
+ (ignore-errors
+ (base64-decode-region (point-min) (point-max)))
+ (buffer-string))))
;;;###autoload
(defun gnus-convert-png-to-face (file)
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[-- Attachment #3: Implement gnus-base64-repad utility function to create properly base64-padded strings --]
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diff --git a/lisp/gnus/gnus-util.el b/lisp/gnus/gnus-util.el
index aa9f137e20..7e8dcaa47c 100644
--- a/lisp/gnus/gnus-util.el
+++ b/lisp/gnus/gnus-util.el
@@ -1343,6 +1343,58 @@ gnus-url-unhex-string
(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,
+regardless of what padding the input string alread had.
+
+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)))
+ (progn
+ (if (and reject-newlines (> (length splitstr) 1))
+ (error "Invalid Base64 string"))
+ (dolist (substr splitstr)
+ (if (and line-length (> (length substr) line-length))
+ (error "Base64 string exceeds line-length"))
+ (if (string-match "[^A-Za-z0-9+/=]" substr)
+ (error "Invalid Base64 string")))
+ (let* ((str (string-join splitstr))
+ (len (length str))
+ (padding nil))
+ (if (string-match "=" str)
+ (setq len (match-beginning 0)))
+ (progn (setq padding
+ (/
+ (- 24
+ (pcase (mod (* len 6) 24)
+ (`0 24)
+ (n n)))
+ 6))
+ (concat
+ (substring str 0 len)
+ (make-string padding ?=)))))))
+
(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',
[-- Attachment #4: Implement test cases of gnus-string>, gnus-string<, and gnus-base64-repad --]
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diff --git a/test/lisp/gnus/gnus-util-tests.el b/test/lisp/gnus/gnus-util-tests.el
index 7eadb0de71..ed33be46a3 100644
--- a/test/lisp/gnus/gnus-util-tests.el
+++ b/test/lisp/gnus/gnus-util-tests.el
@@ -25,6 +25,65 @@
(require 'ert)
(require 'gnus-util)
+(ert-deftest gnus-string> ()
+ ;; Failure paths
+ (should-error (gnus-string> "" 1)
+ :type 'wrong-type-argument)
+ (should-error (gnus-string> "")
+ :type 'wrong-number-of-arguments)
+
+ ;; String tests
+ (should (gnus-string> "def" "abc"))
+ (should (gnus-string> 'def 'abc))
+ (should (gnus-string> "abc" "DEF"))
+ (should (gnus-string> "abc" 'DEF))
+ (should (gnus-string> "αβγ" "abc"))
+ (should (gnus-string> "אבג" "αβγ"))
+ (should (gnus-string> nil ""))
+ (should (gnus-string> "abc" ""))
+ (should (gnus-string> "abc" "ab"))
+ (should-not (gnus-string> "abc" "abc"))
+ (should-not (gnus-string> "abc" "def"))
+ (should-not (gnus-string> "DEF" "abc"))
+ (should-not (gnus-string> 'DEF "abc"))
+ (should-not (gnus-string> "123" "abc"))
+ (should-not (gnus-string> "" "")))
+
+(ert-deftest gnus-string< ()
+ ;; Failure paths
+ (should-error (gnus-string< "" 1)
+ :type 'wrong-type-argument)
+ (should-error (gnus-string< "")
+ :type 'wrong-number-of-arguments)
+
+ ;; String tests
+ (setq case-fold-search nil)
+ (should (gnus-string< "abc" "def"))
+ (should (gnus-string< 'abc 'def))
+ (should (gnus-string< "DEF" "abc"))
+ (should (gnus-string< "DEF" 'abc))
+ (should (gnus-string< "abc" "αβγ"))
+ (should (gnus-string< "αβγ" "אבג"))
+ (should (gnus-string< "" nil))
+ (should (gnus-string< "" "abc"))
+ (should (gnus-string< "ab" "abc"))
+ (should-not (gnus-string< "abc" "abc"))
+ (should-not (gnus-string< "def" "abc"))
+ (should-not (gnus-string< "abc" "DEF"))
+ (should-not (gnus-string< "abc" 'DEF))
+ (should-not (gnus-string< "abc" "123"))
+ (should-not (gnus-string< "" ""))
+
+ ;; gnus-string< checks case-fold-search
+ (setq case-fold-search t)
+ (should (gnus-string< "abc" "DEF"))
+ (should (gnus-string< "abc" 'GHI))
+ (should (gnus-string< 'abc "DEF"))
+ (should (gnus-string< 'GHI 'JKL))
+ (should (gnus-string< "abc" "ΑΒΓ"))
+ (should-not (gnus-string< "ABC" "abc"))
+ (should-not (gnus-string< "def" "ABC")))
+
(ert-deftest gnus-subsetp ()
;; False for non-lists.
(should-not (gnus-subsetp "1" "1"))
@@ -73,4 +132,43 @@ gnus-setdiff
(should (equal '("1") (gnus-setdiff '(2 "1" 2) '(2))))
(should (equal '("1" "1") (gnus-setdiff '(2 "1" 2 "1") '(2)))))
+(ert-deftest gnus-base64-repad ()
+ (should-error (gnus-base64-repad "" nil nil nil)
+ :type 'wrong-number-of-arguments)
+ (should-error (gnus-base64-repad 1)
+ :type 'wrong-type-argument)
+
+ ;; RFC4648 test vectors
+ (should (equal "" (gnus-base64-repad "")))
+ (should (equal "Zg==" (gnus-base64-repad "Zg==")))
+ (should (equal "Zm8=" (gnus-base64-repad "Zm8=")))
+ (should (equal "Zm9v" (gnus-base64-repad "Zm9v")))
+ (should (equal "Zm9vYg==" (gnus-base64-repad "Zm9vYg==")))
+ (should (equal "Zm9vYmE=" (gnus-base64-repad "Zm9vYmE=")))
+ (should (equal "Zm9vYmFy" (gnus-base64-repad "Zm9vYmFy")))
+
+ (should (equal "Zm8=" (gnus-base64-repad "Zm8")))
+ (should (equal "Zg==" (gnus-base64-repad "Zg")))
+ (should (equal "Zg==" (gnus-base64-repad "Zg====")))
+
+ (should-error (gnus-base64-repad " ")
+ :type 'error)
+ (should-error (gnus-base64-repad "Zg== ")
+ :type 'error)
+ (should-error (gnus-base64-repad "Z?\x00g==")
+ :type 'error)
+ ;; line-length
+ (should-error (gnus-base64-repad "Zg====" nil 4)
+ :type 'error)
+ ;; reject-newlines
+ (should-error (gnus-base64-repad "Zm9v\r\nYmFy" t)
+ :type 'error)
+ (should (equal "Zm9vYmFy" (gnus-base64-repad "Zm9vYmFy" t)))
+ (should (equal "Zm9vYmFy" (gnus-base64-repad "Zm9v\r\nYmFy" nil)))
+ (should (equal "Zm9vYmFy" (gnus-base64-repad "Zm9v\r\nYmFy\n" nil)))
+ (should-error (gnus-base64-repad "Zm9v\r\n YmFy\r\n" nil)
+ :type 'error)
+ (should-error (gnus-base64-repad "Zm9v\r\nYmFy" nil 3)
+ :type 'error))
+
;;; gnustest-gnus-util.el ends here
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--
Alex.
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