[FFmpeg-devel] [PATCH] Fix issue when invalid nb_index_entries value is read - SPONSORED BY INA (Institut National de l'Audiovisuel)
Marton Balint
cus at passwd.hu
Mon Mar 27 00:06:10 EEST 2023
On Fri, 24 Mar 2023, Cédric Le Barz wrote:
>
> Hi Marton,
>
> The previous link was not OK, sorry. The good link that will make you
> possible to download the sample is the following :
> https://estendirectapi.ektacom.com/download/ffmpeg/Sample.mxf
Ok, so I checked this, and the problem is that the muxer dumps some
garbarge after the intended end of file (after the random index
pack). The garbage is most likely some part of the MXF file already
written, and our parser fails to parse it because of the
truncation.
Overall I think it is better if we fully skip all data after a random
index pack, because, if it exists, it has to be the last KLV item after a
footer partition.
I will send a patch for that shortly.
Regards,
Marton
>
> Regards,
>
> Cédric
>
>
> Le 24/03/2023 à 10:13, Cédric Le Barz a écrit :
>> Hi Marton,
>>
>> A sample can be downloaded from here :
>> https://estendirectapi.ektacom.com/download/ffmpeg/
>>
>> Regards,
>>
>> Cédric
>>
>>
>> Le 20/03/2023 à 21:03, Marton Balint a écrit :
>>>
>>>
>>> On Mon, 20 Mar 2023, Cédric Le Barz wrote:
>>>
>>>> We have several samples but these are big files: about 7 GB. Is it OK to
>>>> share such a file size ?
>>>
>>> I kind of hoped you have access to the broken muxer and can remux a
>>> small file which can be made public.
>>>
>>> If not, then simply upload it somewhere so I can take a look. If the
>>> sample can't be made public, just share it with me privately.
>>>
>>> Thanks,
>>> Marton
>>>
>>>>
>>>> Thanks for you answer,
>>>>
>>>> Regards,
>>>>
>>>> Cédric
>>>>
>>>> Le 16/03/2023 à 21:28, Marton Balint a écrit :
>>>>>
>>>>>
>>>>> On Thu, 16 Mar 2023, Cédric Le Barz wrote:
>>>>>
>>>>>> Hi,
>>>>>>
>>>>>> By "invalid", I mean that the written nb_index_entries value does not
>>>>>> match with the real number of entries in the table. The number of
>>>>>> entries in the table is lower than the specified one. This is a bug
>>>>>> in
>>>>>> commercial MXFTk software (at least version V 2.8.0.0.1). It exists a
>>>>>> lot a MXF files with this problem.
>>>>>
>>>>> Please share a sample. Or better yet, open a ticket for this issue and
>>>>> attach a sample there for future reference.
>>>>>
>>>>> Thanks,
>>>>> Marton
>>>>>
>>>>>>
>>>>>> Best regards,
>>>>>>
>>>>>> Cédric
>>>>>>
>>>>>> -----Message d'origine-----
>>>>>> De : ffmpeg-devel <ffmpeg-devel-bounces at ffmpeg.org> De la part de
>>>>>> Marton
>>>>>> Balint
>>>>>> Envoyé : mercredi 8 mars 2023 23:06
>>>>>> À : FFmpeg development discussions and patches
>>>>>> <ffmpeg-devel at ffmpeg.org>
>>>>>> Objet : Re: [FFmpeg-devel] [PATCH] Fix issue when invalid
>>>>>> nb_index_entries value is read - SPONSORED BY INA (Institut National
>>>>>> de
>>>>>> l'Audiovisuel)
>>>>>>
>>>>>>
>>>>>>
>>>>>> On Wed, 8 Mar 2023, Cédric Le Barz wrote:
>>>>>>
>>>>>>>
>>>>>>> Fix issue when invalid nb_index_entries value is read : in case of
>>>>>>> false nb_index_entries value, ffmpeg exit. This patch fix this
>>>>>>> problem.
>>>>>>
>>>>>> What do you mean invalid? Is the value wrong, or is the file
>>>>>> truncated in
>>>>>> the middle of the index segment? From the patch it looks like the
>>>>>> latter.
>>>>>>
>>>>>> Is there a single unluckily truncated file that you want to fix with
>>>>>> this
>>>>>> patch, or multiple files can be affected by this fix because e.g.
>>>>>> they
>>>>>> are written by the same broken muxer?
>>>>>>
>>>>>> Overall I am not sure if we want this applied, the user can also opt
>>>>>> to
>>>>>> avoid parsing all partitions with -seekable 0 and read / remux the
>>>>>> file
>>>>>> sequentially ignoring any index, so if somebody wants to rescue the
>>>>>> data,
>>>>>> it can be done as is.
>>>>>>
>>>>>> Regards,
>>>>>> Marton
>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> Signed-off-by: Cedric Le Barz <clebarz at ektacom.com>
>>>>>>> ---
>>>>>>> ffmpeg/libavformat/mxfdec.c | 14 ++++++++++++--
>>>>>>> 1 file changed, 12 insertions(+), 2 deletions(-)
>>>>>>>
>>>>>>> diff --git a/ffmpeg/libavformat/mxfdec.c
>>>>>>> b/ffmpeg/libavformat/mxfdec.c
>>>>>>> index 4530617..ffc8987 100644
>>>>>>> --- a/ffmpeg/libavformat/mxfdec.c
>>>>>>> +++ b/ffmpeg/libavformat/mxfdec.c
>>>>>>> @@ -1221,8 +1221,18 @@ static int
>>>>>>> mxf_read_index_entry_array(AVIOContext *pb, MXFIndexTableSegment
>>>>>>> *seg
>>>>>>> }
>>>>>>> for (i = 0; i < segment->nb_index_entries; i++) {
>>>>>>> - if(avio_feof(pb))
>>>>>>> - return AVERROR_INVALIDDATA;
>>>>>>> +
>>>>>>> + if(avio_feof(pb)) {
>>>>>>> + if (i == 0) {
>>>>>>> + return AVERROR_INVALIDDATA;
>>>>>>> + } else {
>>>>>>> + /* To be more robust to invalid nb_index_entries
>>>>>>> value,
>>>>>>> + fix the index entry number according to read
>>>>>>> entries
>>>>>>> */
>>>>>>> + segment->nb_index_entries = i;
>>>>>>> + return 0;
>>>>>>> + }
>>>>>>> + }
>>>>>>> +
>>>>>>> segment->temporal_offset_entries[i] = avio_r8(pb);
>>>>>>> avio_r8(pb); /*
>>>>>>> KeyFrameOffset */
>>>>>>> segment->flag_entries[i] = avio_r8(pb);
>>>>>>> --
>>>>>>> 2.34.1
>>>>>>>
>>>>>>> _______________________________________________
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>>>>>>>
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