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authorPetteri Hintsanen <petterih@iki.fi>2021-02-21 18:52:55 +0200
committerPetteri Hintsanen <petterih@iki.fi>2021-02-21 18:52:55 +0200
commit7bb5f7fde2f9917ea3753b09d86cb181ef71cf7a (patch)
tree8a99d93ed41d6e552b014f6b344345c016e9f4fc
parent0fe61009c5e00790a180e13021050f92b0916cd0 (diff)
Improve id3v2 validity checks
- Remove id3v2 size checks agains emms-info-native--max-peek-size. Decoded sizes do not guide memory reservation anymore so checks are in that sense redundant. Trigger errors on zero-sized elements though, because they are always wrong. - Verify frame identifiers.
-rw-r--r--emms-info-native.el88
1 files changed, 48 insertions, 40 deletions
diff --git a/emms-info-native.el b/emms-info-native.el
index 039738c..bca21b1 100644
--- a/emms-info-native.el
+++ b/emms-info-native.el
@@ -519,11 +519,13 @@ outside itself.")
(revision u8)
(flags bits 1)
(size-bytes vec 4)
- (size eval (emms-info-native--decode-id3v2-size last t)))
+ (size eval (emms-info-native--checked-id3v2-size 'tag last)))
"id3v2 header specification.")
(defconst emms-info-native--id3v2-frame-header-bindat-spec
'((id str (eval (if (= emms-info-native--id3v2-version 2) 3 4)))
+ (eval (unless (emms-info-native--valid-id3v2-frame-id-p last)
+ (error "id3v2 frame id ‘%s’ is invalid" last)))
(size-bytes vec (eval (if (= emms-info-native--id3v2-version 2) 3 4)))
(size eval (emms-info-native--checked-id3v2-size 'frame last))
(flags bits (eval (if (= emms-info-native--id3v2-version 2) 0 2))))
@@ -569,7 +571,7 @@ in case of errors or if there were no known fields in FILENAME.
See ‘emms-info-native--id3v2-frame-to-info’ for recognized
fields."
- (condition-case-unless-debug nil
+ (condition-case nil
(let* (emms-info-native--id3v2-version
(header (emms-info-native--decode-id3v2-header filename))
(tag-size (bindat-get-field header 'size))
@@ -578,7 +580,7 @@ fields."
(when (memq 6 (bindat-get-field header 'flags))
;; Skip the extended header.
(cl-incf offset
- (emms-info-native--decode-id3v2-ext-header-size filename)))
+ (emms-info-native--checked-id3v2-ext-header-size filename)))
(emms-info-native--decode-id3v2-frames filename
offset
(+ tag-size 10)
@@ -593,10 +595,9 @@ fields."
(bindat-unpack emms-info-native--id3v2-header-bindat-spec
(buffer-string))))
-(defun emms-info-native--decode-id3v2-ext-header-size (filename)
+(defun emms-info-native--checked-id3v2-ext-header-size (filename)
"Read and decode id3v2 extended header size from FILENAME.
-Return the size. Signal an error if the size exceeds
-‘emms-info-native--max-peek-size’."
+Return the size. Signal an error if the size is zero."
(with-temp-buffer
(set-buffer-multibyte nil)
(insert-file-contents-literally filename nil 10 14)
@@ -604,18 +605,18 @@ Return the size. Signal an error if the size exceeds
(defun emms-info-native--checked-id3v2-size (elt bytes)
"Calculate id3v2 element ELT size from BYTES.
-ELT must be either 'tag or 'frame. Check the validity of size.
-Return the size."
- (let (size)
- (cond ((eq elt 'tag)
- (setq size (emms-info-native--decode-id3v2-size bytes t)))
- ((eq elt 'frame)
- (if (= emms-info-native--id3v2-version 4)
- (setq size (emms-info-native--decode-id3v2-size bytes t))
- (setq size (emms-info-native--decode-id3v2-size bytes nil)))))
- (when (> size emms-info-native--max-peek-size)
- (error "id3v2 tag or frame size %s is invalid" size))
- size))
+ELT must be either 'tag or 'frame.
+
+Return the size. Signal an error if the size is zero."
+ (let ((size (cond ((eq elt 'tag)
+ (emms-info-native--decode-id3v2-size bytes t))
+ ((eq elt 'frame)
+ (if (= emms-info-native--id3v2-version 4)
+ (emms-info-native--decode-id3v2-size bytes t)
+ (emms-info-native--decode-id3v2-size bytes nil))))))
+ (if (zerop size)
+ (error "id3v2 tag/frame size is zero")
+ size)))
(defun emms-info-native--decode-id3v2-size (bytes syncsafe)
"Decode id3v2 element size from BYTES.
@@ -641,33 +642,40 @@ Return metadata in a list of (FIELD . VALUE) cons cells."
(let ((offset begin)
(limit (- end (emms-info-native--id3v2-frame-header-size)))
comments)
- (catch 'eof
- (while (< offset limit)
- (let* ((header (emms-info-native--decode-id3v2-frame-header filename
- offset))
- (info-id (emms-info-native--id3v2-frame-info-id header))
- (decoded-size (bindat-get-field (cdr header) 'size)))
- (when (= decoded-size 0) (throw 'eof t))
- (setq offset (car header)) ;advance to frame data begin
- (if (or unsync info-id)
- ;; Note that if unsync is t, we have to always read a
- ;; frame to gets its true size so that we can adjust
- ;; offset correctly.
- (let ((data (emms-info-native--read-id3v2-frame-data filename
- offset
- decoded-size
- unsync)))
- (setq offset (car data))
- (when info-id
- (let ((value (emms-info-native--decode-id3v2-string (cdr data))))
- (push (cons info-id value) comments))))
- ;; Skip the frame.
- (cl-incf offset decoded-size)))))
+ (condition-case nil
+ (while (< offset limit)
+ (let* ((header (emms-info-native--decode-id3v2-frame-header filename
+ offset))
+ (info-id (emms-info-native--id3v2-frame-info-id header))
+ (decoded-size (bindat-get-field (cdr header) 'size)))
+ (setq offset (car header)) ;advance to frame data begin
+ (if (or unsync info-id)
+ ;; Note that if unsync is t, we have to always read a
+ ;; frame to gets its true size so that we can adjust
+ ;; offset correctly.
+ (let ((data (emms-info-native--read-id3v2-frame-data filename
+ offset
+ decoded-size
+ unsync)))
+ (setq offset (car data))
+ (when info-id
+ (let ((value (emms-info-native--decode-id3v2-string (cdr data))))
+ (push (cons info-id value) comments))))
+ ;; Skip the frame.
+ (cl-incf offset decoded-size))))
+ (error nil))
comments))
(defun emms-info-native--id3v2-frame-header-size ()
+ "Return the last decoded header size in bytes."
(if (= emms-info-native--id3v2-version 2) 6 10))
+(defun emms-info-native--valid-id3v2-frame-id-p (id)
+ "Return t if ID is a proper id3v2 frame identifier, nil otherwise."
+ (if (= emms-info-native--id3v2-version 2)
+ (string-match "[A-Z0-9]\\{3\\}" id)
+ (string-match "[A-Z0-9]\\{4\\}" id)))
+
(defun emms-info-native--decode-id3v2-frame-header (filename begin)
"Read and decode id3v2 frame header from FILENAME.
Start reading from offset BEGIN.