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Fix thumbnail generation for mis-detected file types #769

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Fix thumbnail generation for mis-detected file types #769

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@glubsy glubsy commented Nov 28, 2020 •
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  • If a file failed to be detected via filename extension by the javascript frontend, try to detect its type to generate a thumbnail.
  • Use mime type detection to determine the actual file type (if FileInfo module is indeed loaded, otherwise skip detection).
  • Don't write capture file to hard drive disk anymore, but keep it in memory until final thumbnails have been generated.
  • Fix SWF files not having thumbnails generated when they could (usually they can be handled by ffmpeg).
  • Various performance improvements by reducing superfluous or redundant checks.

Fixes #770.

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glubsy commented Nov 28, 2020 •
edited

Note:

  • This is based off of the base branch in Fix short videos thumbnail generation #765, this is a continuation/extension of that work.
  • I don't see the point in keeping capture files on disk, since they are only used once or twice, and then just sit there wasting disk space forever. Instead, I chose to keep the capture data in memory until the final thumbnails have been generated, after which it will be discarded.
  • I tried to make the code as clear as possible, had to refactor things to that end.
  • Even if the thumbnail is generated for a file, the javascript front-end still doesn't know the actual file type. This might need an update to the javascript code for "previews".
    It should not be too hard to send back the detected file type in the response to the request and use the proper player.

@glubsy
Remove redundant variable assignment
e77958d 
Keep the default assignment in case there are more types.
@glubsy
Fix generation of thumbnails for video files under 10 seconds
03fd6dc 
* Use ffprobe/avprobe to get the total duration of each video file first.
* Compute a desired optimal timestamp of 15% of the total duration to seek for and get the thumbnail from.
* Fix capture of ffmpeg's output (from stderr) in exec_cmdv() by using an optional redirection to stdout.
* Capture of sub-process output is optional (possible slight performance gain).
@glubsy
Fix updated files not updating thumbnail as well
9ac1417 
Overwrite already existing thumbnails if the source file's mtime is more recent
@glubsy
Fix getting output from subprocess
a5ea2d0 
* Return stdout as expected from ffprobe to get duration.
* Avoid throwing an exception in favour of a default value for potential
malformed total duration got from ffprobe.
@glubsy
Remove obsolete argument check
7cf18b6 
* Conflict with the newly added boolean arguments if they are
explicitely passed by the caller.
* cmdv has to be an array.
@glubsy
Add seek-in value option for video thumbnails
5a0c630 
* Allows users to specify which percentage of the total video duration
to seek in instead of hardcoding 15%.
* Now defaults to 50%.
@glubsy
Limit thumbnail generation
8ac7f6a 
* This fixes a denial-of-service exploit that would allow the client to
generate an infinite number of thumbnails and fill up the storage completely.
Since the client had control over the requested thumbnail sizes, it could make arbitrary requests for thumbnails, and every time the backend did not find an already generated thumbnail with the specified sizes, it would happily generate a new one.
* Remove the ability of the client to decide thumbnail dimensions and
only let the back-end do this by reading the configuration.
* Limit the number of generated thumbnails per file to only one, with
"landscape" dimensions (4/3).
* Use CSS "object-fit" property to adjust displaying of landscape thumbnails into squares. Ref: https://developer.mozilla.org/en-US/docs/Web/CSS/object-fit
@glubsy
Fix thumbnail generation for mis-detected file types
40ff56e 
* Generate thumbnail despite wrong detected filetype

When a file has the wrong extension, fall back to other types
available until one works.
For unsupported files, get the mime type to determine if we truly cannot
support thumbnail generation.
Cache the type detected for further requests with different sizes.

* Test whether server has Fileinfo extension active

Only check mime types with fileinfo extension if it is active.
If not, avoid brute forcing type detection by rolling over the various
thumbnail generation methods and simply return no thumbnail.

* Keep capture file in memory instead of writing to disk

Keep the capture data in the Image class if the capture data is valid,
otherwise destroy the Image object.
Image doesn't read files from disk directly anymore.
@glubsy
Limit thumbnail generation
2582d22 
* This fixes a denial-of-service exploit that would allow the client to
generate an infinite number of thumbnails and fill up the storage completely.
Since the client had control over the requested thumbnail sizes, it could make arbitrary requests for thumbnails, and every time the backend did not find an already generated thumbnail with the specified sizes, it would happily generate a new one.
* Remove the ability of the client to decide thumbnail dimensions and
only let the back-end do this by reading the configuration.
* Limit the number of generated thumbnails per file to only one, with
"landscape" dimensions (4/3).
* Use CSS "object-fit" property to adjust displaying of landscape thumbnails into squares. Ref: https://developer.mozilla.org/en-US/docs/Web/CSS/object-fit
@glubsy
Remove redundant request for square thumb
a2d21cf 
* We now use only one thumbnail file src for both square and rational
thumbnails so remove superfluous requests.
* Set the same src for both square and landscape dom classes.
@glubsy
Merge branch 'reduce_thumbnails' into thumbnail_wrong_filetype
8f5410c
@glubsy
Rename variable
db110d2 
The href is converted to path.
@glubsy
Reduce superfluous computations
e876184 
Only compute thumbnail configured dimensions on thumbnail API requests.
@glubsy
Merge branch 'reduce_thumbnails' into thumbnail_wrong_filetype
0d93996
@glubsy
Fix typo.
ba6b01a
@glubsy
Merge branch 'reduce_thumbnails' into thumbnail_wrong_filetype
39f75b8
@glubsy
Add file-type blocklist
e25793e 
* In order to handle file types that we don't want to generate
thumbnails for, be explicit about it in the options.
We cannot rely on just removing the unwanted file-types from the
arrays of strings in the options, as the backend will generate
thumbnails for files it detects the actual type for anyway.
@glubsy
Auto-generate thumbnail blocklist
5bcd9af 
When a value is removed from a default array of strings in the
options, the removed value should be considered explicitly blocked by
the user: thumbnails should not be generated, actual underlying file type should
not be checked for. Thus the blocklist should be updated with the
missing string.
@glubsy
Remove client-side sample request for img
4a3dd10 
* Down-sampling should only be requested by the backend.
* For now remove the client-side logic entirely since it is both
superfluous and vulnerable. This can be implemented again on the
back-end if necessary.
@glubsy
Merge branch 'reduce_thumbnails' into thumbnail_wrong_filetype
cb551a1
@glubsy glubsy mentioned this pull request Feb 8, 2021
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