[FFmpeg-devel] [PATCH] avcodec/xpmdec: Fix multiple pointer/memory issues
Paul B Mahol
onemda at gmail.com
Fri May 12 22:13:51 EEST 2017
On 5/12/17, Paul B Mahol <onemda at gmail.com> wrote:
> On 5/12/17, 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.
>
> In theory and/or practice?
>
Feel free to commit this until I came with better solution.
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