[FFmpeg-devel] [PATCH][RFC] nsv seeking

[Jai Menon]

On Wed, Apr 22, 2009 at 7:03 PM, Michael Niedermayer <michaelni at gmx.at> wrote:
> On Wed, Apr 22, 2009 at 12:27:20PM +0530, Jai Menon wrote:
>> On Wed, Apr 22, 2009 at 5:10 AM, Michael Niedermayer <michaelni at gmx.at> wrote:
>> > On Tue, Apr 21, 2009 at 09:43:16PM +0530, Jai Menon wrote:
>> >> On Mon, Apr 20, 2009 at 11:48 PM, Michael Niedermayer <michaelni at gmx.at> wrote:
>> >> > On Mon, Apr 20, 2009 at 08:03:40PM +0530, Jai Menon wrote:
>> >> >> On Mon, Apr 20, 2009 at 6:24 PM, Michael Niedermayer <michaelni at gmx.at> wrote:
>> >> >> > On Sun, Apr 19, 2009 at 04:46:48PM +0530, Jai Menon wrote:
>> >> >> >> On 4/18/09, Fran?ois Revol <revol at free.fr> wrote:
>> >> >> > [...]
>> >> >> >> @@ -348,12 +349,22 @@ static int nsv_parse_NSVf_header(AVFormatContext *s, AVFormatParameters *ap)
>> >> >> >> ? ? ?PRINT(("NSV got infos; filepos %"PRId64"\n", url_ftell(pb)));
>> >> >> >>
>> >> >> >> ? ? ?if (table_entries_used > 0) {
>> >> >> >> + ? ? ? ?int i;
>> >> >> >> ? ? ? ? ?nsv->index_entries = table_entries_used;
>> >> >> >> ? ? ? ? ?if((unsigned)table_entries >= UINT_MAX / sizeof(uint32_t))
>> >> >> >> ? ? ? ? ? ? ?return -1;
> [...]
>> >> >> >> + ? ? ? ?nsv->nsvs_file_offset = av_malloc((unsigned)table_entries_used * sizeof(uint32_t));
>> >> >> >> +
>> >> >> >> + ? ? ? ?for(i=0;i<table_entries_used;i++)
>> >> >> >> + ? ? ? ? ? ?nsv->nsvs_file_offset[i] = get_le32(pb) + size;
>
>
>
>> >> >> >
>> >> >> > exploitable
>> >> >>
>> >> >> I can't think of any feasible attack vector here. Could you be a little verbose.
>> >> >
>> >> > table_entries_used * 4 overflows
>> >>
>> >> So you want the file offset table entries to be 64 bit?
>> >
>> > no i want you to make sure you allocate a table that is capable to
>> > hold the number of entries you write into it
>>
>> Sorry, I don't quite understand. There are table_entries_used no.of
>> entries in the file offset table. And I'm writing exactly those amount
>> to the buffer.
>
> example:
> table_entries_used= 0x4FFFFFFF
>
> table_entries_used * sizeof(uint32_t) = 0x4FFFFFFF * 4 = 0x3FFFFFFC
>
> nsv->nsvs_file_offset= av_malloc(0x3FFFFFFC)
>
> for(i=0; i<0x4FFFFFFF; i++)
> ? ?write 4 bytes to nsv->nsvs_file_offset[i]

Thanks for the example. Is attached patch better?

-- 
Regards,

Jai
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