[FFmpeg-devel] [PATCH] avcodec/xpmdec: Fix multiple pointer/memory issues
wm4
nfxjfg at googlemail.com
Sat May 13 09:38:52 EEST 2017
On Fri, 12 May 2017 20:55:13 +0200
Michael Niedermayer <michael at niedermayer.cc> wrote:
> On Fri, May 12, 2017 at 03:29:52PM +0200, Paul B Mahol wrote:
> > On 5/12/17, Michael Niedermayer <michael at niedermayer.cc> wrote:
> > > On Thu, May 11, 2017 at 11:17:33AM +0200, Michael Niedermayer wrote:
> > >> On Thu, May 11, 2017 at 09:01:57AM +0200, Paul B Mahol wrote:
> > >> > On 5/11/17, Michael Niedermayer <michael at niedermayer.cc> wrote:
> > >> > > Most of these were found through code review in response to
> > >> > > fixing 1466/clusterfuzz-testcase-minimized-5961584419536896
> > >> > > There is thus no testcase for most of this.
> > >> > > The initial issue was Found-by: continuous fuzzing process
> > >> > > https://github.com/google/oss-fuzz/tree/master/targets/ffmpeg
> > >> > >
> > >> > > Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
> > >> > > ---
> > >> > > libavcodec/xpmdec.c | 37 ++++++++++++++++++++++++++++++-------
> > >> > > 1 file changed, 30 insertions(+), 7 deletions(-)
> > >> > >
> > >> > > diff --git a/libavcodec/xpmdec.c b/libavcodec/xpmdec.c
> > >> > > index 9112d4cb5e..03172e4aad 100644
> > >> > > --- a/libavcodec/xpmdec.c
> > >> > > +++ b/libavcodec/xpmdec.c
> > >> > > @@ -29,6 +29,8 @@
> > >> > > typedef struct XPMContext {
> > >> > > uint32_t *pixels;
> > >> > > int pixels_size;
> > >> > > + uint8_t *buf;
> > >> > > + int buf_size;
> > >> > > } XPMDecContext;
> > >> > >
> > >> > > typedef struct ColorEntry {
> > >> > > @@ -233,6 +235,8 @@ static uint32_t color_string_to_rgba(const char
> > >> > > *p, int
> > >> > > len)
> > >> > > const ColorEntry *entry;
> > >> > > char color_name[100];
> > >> > >
> > >> > > + len = FFMIN(FFMAX(len, 0), sizeof(color_name) - 1);
> > >> > > +
> > >> > > if (*p == '#') {
> > >> > > p++;
> > >> > > len--;
> > >> > > @@ -299,18 +303,25 @@ static int xpm_decode_frame(AVCodecContext
> > >> > > *avctx,
> > >> > > void *data,
> > >> > > {
> > >> > > XPMDecContext *x = avctx->priv_data;
> > >> > > AVFrame *p=data;
> > >> > > - const uint8_t *end, *ptr = avpkt->data;
> > >> > > + const uint8_t *end, *ptr;
> > >> > > int ncolors, cpp, ret, i, j;
> > >> > > int64_t size;
> > >> > > uint32_t *dst;
> > >> > >
> > >> > > avctx->pix_fmt = AV_PIX_FMT_BGRA;
> > >> > >
> > >> > > - end = avpkt->data + avpkt->size;
> > >> > > - while (memcmp(ptr, "/* XPM */", 9) && ptr < end - 9)
> > >> > > + av_fast_padded_malloc(&x->buf, &x->buf_size, avpkt->size);
> > >> > > + if (!x->buf)
> > >> > > + return AVERROR(ENOMEM);
> > >> > > + memcpy(x->buf, avpkt->data, avpkt->size);
> > >> > > + x->buf[avpkt->size] = 0;
> > >> > > +
> > >> > > + ptr = x->buf;
> > >> > > + end = x->buf + avpkt->size;
> > >> > > + while (end - ptr > 9 && memcmp(ptr, "/* XPM */", 9))
> > >> > > ptr++;
> > >> > >
> > >> > > - if (ptr >= end) {
> > >> > > + if (end - ptr <= 9) {
> > >> > > av_log(avctx, AV_LOG_ERROR, "missing signature\n");
> > >> > > return AVERROR_INVALIDDATA;
> > >> > > }
> > >> > > @@ -335,7 +346,7 @@ static int xpm_decode_frame(AVCodecContext *avctx,
> > >> > > void
> > >> > > *data,
> > >> > >
> > >> > > size = 1;
> > >> > > for (i = 0; i < cpp; i++)
> > >> > > - size *= 94;
> > >> > > + size *= 95;
> > >> > >
> > >> > > if (ncolors <= 0 || ncolors > size) {
> > >> > > av_log(avctx, AV_LOG_ERROR, "invalid number of colors:
> > >> > > %d\n",
> > >> > > ncolors);
> > >> > > @@ -349,12 +360,15 @@ static int xpm_decode_frame(AVCodecContext
> > >> > > *avctx,
> > >> > > void *data,
> > >> > > return AVERROR(ENOMEM);
> > >> > >
> > >> > > ptr += mod_strcspn(ptr, ",") + 1;
> > >> > > + if (end - ptr < 1)
> > >> > > + return AVERROR_INVALIDDATA;
> > >> > > +
> > >> > > for (i = 0; i < ncolors; i++) {
> > >> > > const uint8_t *index;
> > >> > > int len;
> > >> > >
> > >> > > ptr += mod_strcspn(ptr, "\"") + 1;
> > >> > > - if (ptr + cpp > end)
> > >> > > + if (end - ptr < cpp)
> > >> > > return AVERROR_INVALIDDATA;
> > >> > > index = ptr;
> > >> > > ptr += cpp;
> > >> > > @@ -373,14 +387,20 @@ static int xpm_decode_frame(AVCodecContext
> > >> > > *avctx,
> > >> > > void *data,
> > >> > >
> > >> > > x->pixels[ret] = color_string_to_rgba(ptr, len);
> > >> > > ptr += mod_strcspn(ptr, ",") + 1;
> > >> > > + if (end - ptr < 1)
> > >> > > + return AVERROR_INVALIDDATA;
> > >> > > }
> > >> > >
> > >> > > for (i = 0; i < avctx->height; i++) {
> > >> > > dst = (uint32_t *)(p->data[0] + i * p->linesize[0]);
> > >> > > + if (end - ptr < 1)
> > >> > > + return AVERROR_INVALIDDATA;
> > >> > > ptr += mod_strcspn(ptr, "\"") + 1;
> > >> > > + if (end - ptr < 1)
> > >> > > + return AVERROR_INVALIDDATA;
> > >> > >
> > >> > > for (j = 0; j < avctx->width; j++) {
> > >> > > - if (ptr + cpp > end)
> > >> > > + if (end - ptr < cpp)
> > >> > > return AVERROR_INVALIDDATA;
> > >> > >
> > >> > > if ((ret = ascii2index(ptr, cpp)) < 0)
> > >> > > @@ -405,6 +425,9 @@ static av_cold int
> > >> > > xpm_decode_close(AVCodecContext
> > >> > > *avctx)
> > >> > > XPMDecContext *x = avctx->priv_data;
> > >> > > av_freep(&x->pixels);
> > >> > >
> > >> > > + av_freep(&x->buf);
> > >> > > + x->buf_size = 0;
> > >> > > +
> > >> > > return 0;
> > >> > > }
> > >> > >
> > >> > > --
> > >> > > 2.11.0
> > >> > >
> > >> > > _______________________________________________
> > >> > > ffmpeg-devel mailing list
> > >> > > ffmpeg-devel at ffmpeg.org
> > >> > > http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
> > >> > >
> > >> >
> > >> > This is suboptimal solution.
> > >>
> > >> That comment isnt helpfull in improving the patch. It doesnt say
> > >> what it is that you would like changed.
> > >>
> > >> I could probably replace string functions and avoid copying the whole
> > >> packet if thats what you suggest ?
> > >> it makes this bugfix more complex though
> > >
> > > ping, this is a security issue and needs to be fixed
> >
> >
> > I told you that its unacceptable.
> >
>
> > Do this: avpkt->data[avpkt->size] = 0;
>
> packet input to a decoder is not writable,
> in fact it could be part of a memory maped file and litterally be in
> non writable memory.
You don't seem to know our API. You can make it writable.
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