[FFmpeg-devel] [PATCH] libavutil/encryption_info: Add NULL checks.

[Jacob Trimble]

On Fri, Jun 1, 2018 at 5:03 PM Michael Niedermayer
<michael at niedermayer.cc> wrote:
>
> On Thu, May 31, 2018 at 09:33:36AM -0700, Jacob Trimble wrote:
> > Found by Chrome's ClusterFuzz: http://crbug.com/846662.
> >
> > Signed-off-by: Jacob Trimble <modmaker at google.com>
> > ---
> >  libavutil/encryption_info.c | 7 +++++--
> >  1 file changed, 5 insertions(+), 2 deletions(-)
> >
> > diff --git a/libavutil/encryption_info.c b/libavutil/encryption_info.c
> > index 20a752d6b4..a48ded922c 100644
> > --- a/libavutil/encryption_info.c
> > +++ b/libavutil/encryption_info.c
> > @@ -64,6 +64,8 @@ AVEncryptionInfo *av_encryption_info_clone(const AVEncryptionInfo *info)
> >  {
> >      AVEncryptionInfo *ret;
> >
> > +    if (!info)
> > +        return NULL;
> >      ret = av_encryption_info_alloc(info->subsample_count, info->key_id_size, info->iv_size);
> >      if (!ret)
> >          return NULL;
>
> > @@ -127,7 +129,7 @@ uint8_t *av_encryption_info_add_side_data(const AVEncryptionInfo *info, size_t *
> >      uint8_t *buffer, *cur_buffer;
> >      uint32_t i;
> >
> > -    if (UINT32_MAX - FF_ENCRYPTION_INFO_EXTRA < info->key_id_size ||
> > +    if (!info || !size || UINT32_MAX - FF_ENCRYPTION_INFO_EXTRA < info->key_id_size ||
> >          UINT32_MAX - FF_ENCRYPTION_INFO_EXTRA - info->key_id_size < info->iv_size ||
> >          (UINT32_MAX - FF_ENCRYPTION_INFO_EXTRA - info->key_id_size - info->iv_size) / 8 < info->subsample_count) {
> >          return NULL;
> > @@ -260,7 +262,8 @@ uint8_t *av_encryption_init_info_add_side_data(const AVEncryptionInitInfo *info,
> >      uint8_t *buffer, *cur_buffer;
> >      uint32_t i, max_size;
> >
> > -    if (UINT32_MAX - FF_ENCRYPTION_INIT_INFO_EXTRA < info->system_id_size ||
> > +    if (!info || !side_data_size ||
> > +        UINT32_MAX - FF_ENCRYPTION_INIT_INFO_EXTRA < info->system_id_size ||
> >          UINT32_MAX - FF_ENCRYPTION_INIT_INFO_EXTRA - info->system_id_size < info->data_size) {
> >          return NULL;
> >      }
>
> in which valid case would these be called with NULL input ?
> iam asking as this feels as if it might be a bug in teh caller
>

This was found by Chrome's ClusterFuzz, which I am not that familiar
with.  I think it was just running fuzz tests directly on FFmpeg code,
so it wasn't in production code.  But since this is a public method,
we should validate the input in any case.

> thx
>
> [...]
> --
> Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
>
> In a rich man's house there is no place to spit but his face.
> -- Diogenes of Sinope
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