[FFmpeg-devel] [PATCH 1/2] avformat/aaxdec: Check for overlaping segments

[FFmpeg-devel] [PATCH 1/2] avformat/aaxdec: Check for overlaping segments

[Michael Niedermayer]

Fixes: Timeout
Fixes: 45875/clusterfuzz-testcase-minimized-ffmpeg_dem_AAX_fuzzer-6121689903136768

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
---
 libavformat/aaxdec.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/libavformat/aaxdec.c b/libavformat/aaxdec.c
index 0ae4057a53..baa405bb17 100644
--- a/libavformat/aaxdec.c
+++ b/libavformat/aaxdec.c
@@ -251,6 +251,10 @@ static int aax_read_header(AVFormatContext *s)
                 size  = avio_rb32(pb);
                 a->segments[r].start = start + a->data_offset;
                 a->segments[r].end   = a->segments[r].start + size;
+                if (r &&
+                    a->segments[r].start < a->segments[r-1].end &&
+                    a->segments[r].end   > a->segments[r-1].start)
+                    return AVERROR_INVALIDDATA;
             } else
                 return AVERROR_INVALIDDATA;
         }
-- 
2.17.1

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[FFmpeg-devel] [PATCH 2/2] avformat/aiffdec: check allocated size for overflow

[Michael Niedermayer]

Fixes: signed integer overflow: 2147483647 + 1 cannot be represented in type 'int'
Fixes: 45891/clusterfuzz-testcase-minimized-ffmpeg_dem_AIFF_fuzzer-6159183893889024

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
---
 libavformat/aiffdec.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/libavformat/aiffdec.c b/libavformat/aiffdec.c
index 3634bb4960..c2b8e0dede 100644
--- a/libavformat/aiffdec.c
+++ b/libavformat/aiffdec.c
@@ -72,7 +72,12 @@ static int get_tag(AVIOContext *pb, uint32_t * tag)
 /* Metadata string read */
 static void get_meta(AVFormatContext *s, const char *key, int size)
 {
-    uint8_t *str = av_malloc(size+1);
+    uint8_t *str;
+
+    if (size == INT_MAX)
+        return;
+
+    str = av_malloc(size+1);
 
     if (str) {
         int res = avio_read(s->pb, str, size);
-- 
2.17.1

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Re: [FFmpeg-devel] [PATCH 2/2] avformat/aiffdec: check allocated size for overflow

[Andreas Rheinhardt]

Michael Niedermayer:
> Fixes: signed integer overflow: 2147483647 + 1 cannot be represented in type 'int'
> Fixes: 45891/clusterfuzz-testcase-minimized-ffmpeg_dem_AIFF_fuzzer-6159183893889024
> 
> Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
> Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
> ---
>  libavformat/aiffdec.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/libavformat/aiffdec.c b/libavformat/aiffdec.c
> index 3634bb4960..c2b8e0dede 100644
> --- a/libavformat/aiffdec.c
> +++ b/libavformat/aiffdec.c
> @@ -72,7 +72,12 @@ static int get_tag(AVIOContext *pb, uint32_t * tag)
>  /* Metadata string read */
>  static void get_meta(AVFormatContext *s, const char *key, int size)
>  {
> -    uint8_t *str = av_malloc(size+1);
> +    uint8_t *str;
> +
> +    if (size == INT_MAX)
> +        return;
> +
> +    str = av_malloc(size+1);
>  
>      if (str) {
>          int res = avio_read(s->pb, str, size);

If a size of INT_MAX is legal, then you can just use "size + 1U" to
avoid the wraparound. (The allocation will then fail with the default
value of max_alloc_size and in this case the avio_skip() will be
executed, so that we don't lose sync (your patch does that).)
Looking at get_tag() shows that the size actually comes from a uint32_t
which gets truncated to INT_MAX if it is not representable in an int. I
don't know whether the specs mandate this behaviour (probably not, so
one loses sync). If one wanted to impose an arbitrary limit, I will use
something much smaller than INT_MAX.

- Andreas
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Re: [FFmpeg-devel] [PATCH 2/2] avformat/aiffdec: check allocated size for overflow

[Michael Niedermayer]

[-- Attachment #1.1: Type: text/plain, Size: 2115 bytes --]

On Wed, Mar 23, 2022 at 12:07:25PM +0100, Andreas Rheinhardt wrote:
> Michael Niedermayer:
> > Fixes: signed integer overflow: 2147483647 + 1 cannot be represented in type 'int'
> > Fixes: 45891/clusterfuzz-testcase-minimized-ffmpeg_dem_AIFF_fuzzer-6159183893889024
> > 
> > Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
> > Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
> > ---
> >  libavformat/aiffdec.c | 7 ++++++-
> >  1 file changed, 6 insertions(+), 1 deletion(-)
> > 
> > diff --git a/libavformat/aiffdec.c b/libavformat/aiffdec.c
> > index 3634bb4960..c2b8e0dede 100644
> > --- a/libavformat/aiffdec.c
> > +++ b/libavformat/aiffdec.c
> > @@ -72,7 +72,12 @@ static int get_tag(AVIOContext *pb, uint32_t * tag)
> >  /* Metadata string read */
> >  static void get_meta(AVFormatContext *s, const char *key, int size)
> >  {
> > -    uint8_t *str = av_malloc(size+1);
> > +    uint8_t *str;
> > +
> > +    if (size == INT_MAX)
> > +        return;
> > +
> > +    str = av_malloc(size+1);
> >  
> >      if (str) {
> >          int res = avio_read(s->pb, str, size);
> 
> If a size of INT_MAX is legal, then you can just use "size + 1U" to
> avoid the wraparound. (The allocation will then fail with the default
> value of max_alloc_size and in this case the avio_skip() will be
> executed, so that we don't lose sync (your patch does that).)

> Looking at get_tag() shows that the size actually comes from a uint32_t
> which gets truncated to INT_MAX if it is not representable in an int. I
> don't know whether the specs mandate this behaviour (probably not, so
> one loses sync). If one wanted to impose an arbitrary limit, I will use
> something much smaller than INT_MAX.

The goal of my patch was to fix the undefined behavior.
You are very correct that aiffdec has other bugs.

ill send a more complete set of fixes 

thx

[...]
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Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

There will always be a question for which you do not know the correct answer.

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Re: [FFmpeg-devel] [PATCH 1/2] avformat/aaxdec: Check for overlaping segments

[Michael Niedermayer]

[-- Attachment #1.1: Type: text/plain, Size: 635 bytes --]

On Wed, Mar 23, 2022 at 10:30:32AM +0100, Michael Niedermayer wrote:
> Fixes: Timeout
> Fixes: 45875/clusterfuzz-testcase-minimized-ffmpeg_dem_AAX_fuzzer-6121689903136768
> 
> Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
> Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
> ---
>  libavformat/aaxdec.c | 4 ++++
>  1 file changed, 4 insertions(+)

will apply

[...]
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Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

If you think the mosad wants you dead since a long time then you are either
wrong or dead since a long time.

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