On 2021-12-21 03:06 am, Michael Niedermayer wrote:
On Mon, Dec 20, 2021 at 10:21:53PM +0100, Michael Niedermayer wrote:
On Tue, Dec 21, 2021 at 02:31:33AM +0530, Gyan Doshi wrote:
On 2021-12-21 02:24 am, Andreas Rheinhardt wrote:
Gyan Doshi:
On 2021-12-21 02:18 am, Andreas Rheinhardt wrote:
Gyan Doshi:
Avoids overreading the box and ingesting absurd values into stts_data
---
libavformat/mov.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/libavformat/mov.c b/libavformat/mov.c
index 2aed6e80ef..5a7209837f 100644
--- a/libavformat/mov.c
+++ b/libavformat/mov.c
@@ -2935,6 +2935,11 @@ static int mov_read_stts(MOVContext *c,
AVIOContext *pb, MOVAtom atom)
avio_rb24(pb); /* flags */
entries = avio_rb32(pb);
+ if (atom.size < 8 + (int64_t)entries*8) {
+ av_log(c->fc, AV_LOG_ERROR, "Truncated STTS box for st
%d.\n", c->fc->nb_streams-1);
+ return AVERROR_INVALIDDATA;
+ }
+
av_log(c->fc, AV_LOG_TRACE, "track[%u].stts.entries = %u\n",
c->fc->nb_streams-1, entries);
This might fix the issue with the fuzzer sample Michael gave you, but
what would stop the fuzzer (or a malicious adversary) from simply using
a gigantic atom size?
Do you want the comparison to switch to a strict inequality?
No, because it might be that the adversary just uses the expected size,
so this would not fix anything.
There are real world multi-hour files with large stts boxes, so there is no
robust solution for that, only heuristics.
lets take a closer look at the loop you are adding
sample_count = avio_rb32(pb);
sample_duration = avio_rb32(pb);
sc->stts_data[i].count= sample_count;
sc->stts_data[i].duration= sample_duration;
for (int j = 0; j < sample_count; j++) {
This also adds undefined behavior as j overflows when sample_count > INT_MAX
I'll try to optimize by getting rid of the loop if I can, but this
discussion belongs to the patch for max_stts_delta.
How's this patch?
Regards,
Gyan
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