2018-01-19 18:51 GMT+01:00 Michael Niedermayer <mich...@niedermayer.cc>: > On Thu, Jan 18, 2018 at 09:28:40PM +0100, Carl Eugen Hoyos wrote: >> Hi! >> >> The probe score for swf files (with uncompressed headers) is currently >> very high after testing a little more than 24bit, attached patch >> reduces the score. > > hmm > the first 24 bits are tested and all but 2 values are rejected > > thats 23 bits that must match
Ok. > then 4 values are tested which can be from 1 to 31 bits each > the tests are each either == 0 or != 0 so they are a bit weak > but its at least adding 4 bits that must match and also len I was sure this is not equivalent to four bits on a specific position (but for the patch I assumed a "best case scenario" where this actually were the case). > itself has to be smallish so we could argue that this gets us to > about 28 bits > and then buf[3] is checked to be < 20 > at this point we need about 32bits to be matching, still not huge but > id think this is stronger than what file extensions prove which are > MAX/2 We return MAX/2 for many "initial 32 bits" tests and I believe we made good experience (and for MAX/2 the extension is ignored or do I misremember?) > The test is weakened by using 0 / not 0 / ascii as values though > > Have you seen an actual probe failure ? No, I was looking at another issue. Carl Eugen _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-devel