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Bug 1117406 - Fix handling of out-of-range PNG tRNS values. r=jmuizelaar

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This commit is contained in:
Glenn Randers-Pehrson 2015-01-24 12:43:49 -05:00
parent 14017f7761
commit 05455fdadb
1 changed files with 15 additions and 12 deletions
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27
image/decoders/nsPNGDecoder.cpp
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@ -551,22 +551,25 @@ nsPNGDecoder::info_callback(png_structp png_ptr, png_infop info_ptr)
}
if (png_get_valid(png_ptr, info_ptr, PNG_INFO_tRNS)) {
int sample_max = (1 << bit_depth);
png_color_16p trans_values;
png_get_tRNS(png_ptr, info_ptr, &trans, &num_trans, &trans_values);
// libpng doesn't reject a tRNS chunk with out-of-range samples
// so we check it here to avoid setting up a useless opacity
// channel or producing unexpected transparent pixels when using
// libpng-1.2.19 through 1.2.26 (bug #428045)
if ((color_type == PNG_COLOR_TYPE_GRAY &&
(int)trans_values->gray > sample_max) ||
(color_type == PNG_COLOR_TYPE_RGB &&
((int)trans_values->red > sample_max ||
(int)trans_values->green > sample_max ||
(int)trans_values->blue > sample_max))) {
// clear the tRNS valid flag and release tRNS memory
png_free_data(png_ptr, info_ptr, PNG_FREE_TRNS, 0);
} else {
// channel or producing unexpected transparent pixels (bug #428045)
if (bit_depth < 16) {
png_uint_16 sample_max = (1 << bit_depth) - 1;
if ((color_type == PNG_COLOR_TYPE_GRAY &&
trans_values->gray > sample_max) ||
(color_type == PNG_COLOR_TYPE_RGB &&
(trans_values->red > sample_max ||
trans_values->green > sample_max ||
trans_values->blue > sample_max))) {
// clear the tRNS valid flag and release tRNS memory
png_free_data(png_ptr, info_ptr, PNG_FREE_TRNS, 0);
num_trans = 0;
}
}
if (num_trans != 0) {
png_set_expand(png_ptr);
}
}