No issues with the exceptions as such.
Whilst this does make things better I still have some reservations about the
result of the fix since remember the bug says "JPEG with embedded
thumbnail".
If I apply your patch and use the original file I get two images but neither
reports any thumbnails .. using either metadata or
ImageReader.getNumThumbnails(int)
One image is 3968x2976, the other is 640x480 (vga resolution).
This seems a little big for a thumbnail but still a lot smaller than the
original
and a nice size for say using on a camera display.
So my suspicion is the latter is an EXIF embedded thumbnail - since it
is JPEG
compressed and that ideally what we should return here is one image with
one thumbnail.
But since we aren't properly parsing the EXIF APP1 data .. we just find
it as another
image using the 'brute force' method of looking for the marker sequence.
I am a bit surprised though that this hasn't been a more common complaint.
We now have the TIFF code so if this really is the case then a fuller fix
would return this as a thumbnail. If it really is a follow-on second image
in the stream then the fix would seem OK. I just want to know which we
have here
Then we get to the image you used in the test. Yes, this throws an exception
with 8ux .. but it is a different complaint.
With the original file :-
Exception in thread "main" javax.imageio.IIOException: Not a JPEG file:
starts with 0xff 0xff
With the test file :-
Exception in thread "main" javax.imageio.IIOException: Not a JPEG file:
starts with 0xff 0xe2
That's an APP2 marker .. which may mean an embedded ICC Profile.
The code is supposed to be able to handle that
https://docs.oracle.com/javase/8/docs/api/javax/imageio/metadata/doc-files/jpeg_metadata.html#color
.. so perhaps its something else but it would be nice to know this is
being handled
properly.
Also - back to thumbnails - this one reports zero thumbnails too !
So with the test and the fix being all about embedded thumbnails it
is weird that there aren't any :-)
I think we need to break down the exact contents/structure of these files
to be sure what we have here.
-phil.
On 06/14/2016 09:30 PM, Jim Graham wrote:
Hi Jay,
Thanks for explaining all of the details. It seems that constantly
being in scan mode simplifies things because we have to be in scan
mode for entropy data anyway, but it still allows errant bytes outside
of the entropy data to be accepted by this parser. I'm not sure if
that is a problem in the long run, but it is not a new issue (since
the existing code already was doing that) so we can live with it for
purposes of fixing this particular bug.
One simplification of what you say below, it appears that among all of
those cases none of them really impact the fact that un-sized entropy
encoded data only appears inside the SOS marker and the only markers
found inside the entropy data itself are the RSTn markers. Ideally we
could limit our scanning to just the data following the SOS marker and
its sized header and only allow RSTn markers to appear inside that
manual scan, reverting to a non-scanning mode when we reach another
marker (DNL it looks like). But, that would be the subject of a
different bug fix.
It looks OK to me as long as Phil is OK with the types of exceptions
that you are throwing in the various new exceptional cases, and with
the change to now assume that skipImage always being called at an SOI
marker. Phil?
...jim
On 6/14/16 9:36 AM, Jayathirth D V wrote:
Hi Jim,
I have updated the code to add check for EOF even in case of reading
length. Also I have updated the code such that in all the cases where
we find EOF before EOI we are throwing IndexOutOfBoundsException and
in other failed cases we are throwing IOException.
More analysis :
All the length markers that we are checking in our case have
valid length data except SOS marker in which always the length value
will be 12 and it is the value only for the length of Scan header.
After Scan header(SOS) we have compressed data for which we have
no parameter which gives the length so that we can skip it completely.
Once we get to the initial SOS header it can take 3 paths based
on how the data follows:
a) If we don't have Restart enabled and if we scan
continuously through compressed data we will find EOI otherwise we
will find RST markers and then EOI marker.
b) If we have multiple scan headers(Multi-scan scenario) we
have to follow point 'a' in loop with each scan header separated by
DNL and other miscellaneous tables.
c) If we have multiple frame headers(Multi-frame scenario) we
have to follow point 'b' in loop with different markers coming in
between.
Above information is taken from page 52 of
https://www.w3.org/Graphics/JPEG/itu-t81.pdf
Since we can't rely on length specified in SOS header and there is
possibility of having multiple SOS headers, we need to search for
FF(foundFF). It means even if we jump for the length specified is SOS
header the next byte is not promised to be '0xff'.
For all the remaining markers we will get proper information related
to the length and we will skip all data part(which might contain data
similar to EOI/SOI/or any other marker). While propagating through
the 'for' loop we are following the same approach.
Please find updated webrev for review :
http://cr.openjdk.java.net/~jdv/8152672/webrev.02/
Thanks,
Jay
-----Original Message-----
From: Jim Graham
Sent: Tuesday, June 14, 2016 12:44 AM
To: Jayathirth D V
Cc: 2d-dev@openjdk.java.net; Philip Race
Subject: Re: [OpenJDK 2D-Dev] Review Request for JDK-8152672 :
Exception while getting second image properties for JPEG with
embedded thumbnail
Hi Jay,
You still don't check the read() calls in the length case to see if
you reached EOF (-1). The potential for an infinite loop is still
there.
Also, you still search for an FF, even if you require the function to
start at an SOI marker - all subsequent markers are still subject to
a search rather than a deterministic requirement that we encounter
markers with no gaps between them.
Why do we have the foundFF variable in the first place? If we just
saw an SOI marker then the next byte *must be* a 0xff (shouldn't it?
Am I missing something?). We shouldn't read a byte and check if it
is a 0xff and then try again, we should expect a single 0xff byte
followed by a marker type byte, as in:
while (true) {
int byteval == iis.read();
// if (byteval < 0) then what?
if (byteval != 0xff) { exception }
byteval = iis.read();
switch (byteval) {
}
}
The only question is if we get a -1 on the first read if we treat
that as an implicit EOI as we do now, or if we treat it as an exception.
Note that if we get a -1 in the second read, then we have a
half-formed tag and that should fall into the default and be declared
a bad file.
...jim
On 6/13/2016 10:00 AM, Jayathirth D V wrote:
Hi Jim,
Thanks for your valuable inputs.
I have updated the code with your inputs:
1) We should check for complete SOI marker and not just "FF" at
start of skipImage().
2) There is no need of iis.read() which was happening in default
case. iis.read() present in for loop check will take care of
checking EOF.
3) I have added case condition for all the markers having length
and added default case where we get invalid marker starting with FF.
Apart from above changes, after going more through
https://www.w3.org/Graphics/JPEG/itu-t81.pdf got to know following
things:
1) TEM is also one more marker without length so added case for
that.
2) Since we have all unique conditions checked, we should not
find any SOI marker after the initial SOI marker before we find EOI.
Made changes to throw IOException in this case.
Please find updated webrev for review:
http://cr.openjdk.java.net/~jdv/8152672/webrev.01/
Thanks,
Jay
-----Original Message-----
From: Jim Graham
Sent: Saturday, June 11, 2016 3:07 AM
To: Jayathirth D V; Philip Race
Cc: 2d-dev@openjdk.java.net
Subject: Re: [OpenJDK 2D-Dev] Review Request for JDK-8152672 :
Exception while getting second image properties for JPEG with embedded
thumbnail
Thanks for the response Jay, I think I was misreading some of the
code as now that I look back at it, it's mostly written as I was
suggesting with respect to skipping over data sections, however it
is still doing some scanning to find the initial 0xFF. Some thoughts:
- If we can be sure that we are located at where a tag should be,
then shouldn't we just read a byte and assert that it is 0xFF and
report the file as invalid if it isn't? The current code will just
ignore the byte and continue reading until it finds a 0xFF, but the
fact that the first byte we read isn't 0xFF means we have wandered
into data that isn't following the file format (or, possibly, that
this was called from a case where we hadn't completely read a
section of data, but that should be fixed as we could be in the
middle of a section that isn't entropy encoded and our search for
0xFF might have invalid assumptions).
- The bytes read in the default section to get the length and the
tag for the next block aren't tested for EOF (-1). This may even
get us into an infinite loop if we hit EOF at the right time (just
after a sized block tag) as the size bytes will read and combine
into a -1 size, back up three bytes, and then reread the same tag
and try to compute a length again which will send us back 3 bytes, etc.
- default assumes that all other markers that are created will be
sized, but can we assert that? Shouldn't we specifically list all
known sized markers and have the default case reject the file as not
being of a format that we recognize?
...jim
On 6/9/2016 11:21 PM, Jayathirth D V wrote:
Hi Jim,
I think the harmless byte that you are referring to will be applied
only for image data(Between SOS(Start of Scan) marker and EOI). For
example, any "FF" data present in Jpeg image will be represented as
"FF 00". But I think application headers or comments section can
contain data which will be similar to EOI,SOI or other markers(FF XX).
Thanks,
Jay
-----Original Message-----
From: Jim Graham
Sent: Friday, June 10, 2016 5:28 AM
To: Jayathirth D V; Philip Race
Cc: 2d-dev@openjdk.java.net
Subject: Re: [OpenJDK 2D-Dev] Review Request for JDK-8152672 :
Exception while getting second image properties for JPEG with
embedded thumbnail
It looks like JPEG files have protection for scanning for an FF and
assuming it is a marker by making sure that all FF bytes that
appear in data are followed by a harmless byte, so a brute force
search is probably fine. But it still seems wasteful when we know
we are at a tag and we know the sizes of all of the tags, we should
be able to skip around the file looking for the SOI directly...
...jim
On 6/2/2016 5:10 AM, Jayathirth D V wrote:
Fixed typo.
*From:*Jayathirth D V
*Sent:* Thursday, June 02, 2016 5:08 PM
*To:* Philip Race
*Cc:* Jim Graham; 2d-dev@openjdk.java.net
*Subject:* RE: Review Request for JDK-8152672 : Exception while
getting second image properties for JPEG with embedded thumbnail
Hi Phil,
We have two kind of images with which we are able to reproduce the
issue:
1) sample.jpg present in JBS bug(We can't use this image
because it
is licensed ).
2) JpegEmbedThumbnail.jpg taken using Prasanta's camera and
used in
webrev.
_ _
_sample.jpg : _
_ _
If we do getNumImages() it will return 2. getNumImages() follows the
same logic of skipping markers with length and registering SOI to
get number of images.
sample.jpg has markers as follows :
SOI -> APP1 - > SOI -> EOI -> APP1 End -> EOI -> SOI -> EOI
I have dumped first image its SOI is first one in the above list and
for second image it is third one in the list. getNumImages() counts
first and third SOI for number of images. But in case of skipImage()
we are getting inside APP1 marker and considering its SOI.
_JpegEmbedThumbnail.jpg :_
_ _
If we do getNumImages() it will return 1.
JpegEmbedThumbnail.jpg has markers as follows :
SOI -> APP1 -> SOI -> EOI -> APP1 End -> APP2 -> SOI -> APP2 End ->
APP2
-> EOI -> APP2 End -> EOI
getNumImages() counts only first SOI for number of images. But in
case of skipImage() we will are getting inside APP1 and APP2
markers also.
Thanks,
Jay
*From:*Phil Race
*Sent:* Thursday, June 02, 2016 4:05 AM
*To:* Jayathirth D V
*Cc:* Jim Graham; 2d-dev@openjdk.java.net
<mailto:2d-dev@openjdk.java.net>
*Subject:* Re: Review Request for JDK-8152672 : Exception while
getting second image properties for JPEG with embedded thumbnail
I am bit doubtful about this. Are you sure we are correct in
reporting two images to begin with ?
Thumbnails should not get counted ..
-phil.
On 06/01/2016 01:06 AM, Jayathirth D V wrote:
Updated bug title in JBS as it was misleading.
*From:* Jayathirth D V
*Sent:* Wednesday, June 01, 2016 12:48 PM
*To:* Philip Race; Jim Graham
*Cc:* 2d-dev@openjdk.java.net <mailto:2d-dev@openjdk.java.net>
*Subject:* Review Request for JDK-8152672 : Exception getting
thumbnail size for JPEG with embedded thumbnail
Hi,
_Please review the following fix in JDK9:_
Bug : https://bugs.openjdk.java.net/browse/JDK-8152672
Webrev : http://cr.openjdk.java.net/~jdv/8152672/webrev.00/
<http://cr.openjdk.java.net/%7Ejdv/8152672/webrev.00/>
Issue : When we are trying to get properties related to second
image
in JPEG file we are getting IIOException mentioning that it is
not a
JPEG file.
Root cause : When we are skipping first image to reach second
image
header, we are just trying to find next available EOI marker.
But if
first image has embedded thumbnail in APP1 marker, we will
reach to
EOI of this thumbnail and not EOI of first image. So after we
reach
EOI of embedded thumbnail we try to access second image SOI
marker
which will fail.
Solution : We have to change the logic of how we skip to
consecutive
images in JPEG file. We know that application markers,
comments or
other markers can contain data same as SOI & EOI. Instead of just
checking for EOI marker serially, we should read length of these
markers and skip them.
Thanks,
Jay
