[Pkg-phototools-devel] Bug#734238: Fix for CVE-2013-6045 breaks decoding of chroma-subsampled images

[Benjamin Gilbert]

The slide file at [1] contains 4,569 chroma-subsampled J2K images, and 
the file at [2] contains 25,120.  The below program will decode every 
image into memory via OpenSlide.  It executes Valgrind-clean against 
both slides on 1.3+dfsg-4.6.

The functionality does work, and people use it.  Please consider 
applying a more nuanced patch that fixes the real problem, rather than 
disabling the entire feature.

Thanks,
--Benjamin Gilbert

[1]: 
http://openslide.cs.cmu.edu/download/openslide-testdata/Aperio/JP2K-33003-1.svs
[2]: 
http://openslide.cs.cmu.edu/download/openslide-testdata/Aperio/JP2K-33003-2.svs


/* gcc -O2 $(pkg-config --cflags --libs openslide) \
    -o walk-slide walk-slide.c */

#include <stdio.h>
#include <stdint.h>
#include <stdlib.h>
#include <openslide.h>

#define DIMENSION 1024

int main(int argc, char **argv)
{
     uint32_t *buf;
     int64_t x, y, w, h;
     int32_t levels, level;
     double downsample;
     openslide_t *osr;
     const char *error;

     if (argc < 2) {
         printf("specify slide file\n");
         return 1;
     }
     buf = malloc(DIMENSION * DIMENSION * sizeof(*buf));
     osr = openslide_open(argv[1]);
     if (!osr) {
         printf("failed to open\n");
         return 1;
     }
     levels = openslide_get_level_count(osr);
     openslide_get_level0_dimensions(osr, &w, &h);
     for (level = 0; level < levels; level++) {
         downsample = openslide_get_level_downsample(osr, level);
         for (y = 0; y < h; y += DIMENSION * downsample) {
             for (x = 0; x < w; x += DIMENSION * downsample) {
                 printf("%d %llu %llu\n", level, x, y);
                 openslide_read_region(osr, buf, x, y, level,
                         DIMENSION, DIMENSION);
                 error = openslide_get_error(osr);
                 if (error) {
                     printf("%s\n", error);
                     return 1;
                 }
             }
         }
     }
     openslide_close(osr);
     free(buf);
     return 0;
}