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Validate property allocation size in avifImageCopyProperties() #3226

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6 changes: 4 additions & 2 deletions src/avif.c
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Original file line number Diff line number Diff line change
Expand Up @@ -234,9 +234,11 @@ static avifResult avifImageCopyProperties(avifImage * dstImage, const avifImage
dstImage->numProperties = 0;

if (srcImage->numProperties != 0) {
dstImage->properties = (avifImageItemProperty *)avifAlloc(srcImage->numProperties * sizeof(srcImage->properties[0]));
AVIF_CHECKERR(srcImage->numProperties <= SIZE_MAX / sizeof(srcImage->properties[0]), AVIF_RESULT_INVALID_ARGUMENT);
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@wantehchang wantehchang May 26, 2026

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This check is not necessary. The API contract requires that srcImage points to a valid avifImage.

const size_t propertiesSize = srcImage->numProperties * sizeof(srcImage->properties[0]);
dstImage->properties = (avifImageItemProperty *)avifAlloc(propertiesSize);
AVIF_CHECKERR(dstImage->properties != NULL, AVIF_RESULT_OUT_OF_MEMORY);
memset(dstImage->properties, 0, srcImage->numProperties * sizeof(srcImage->properties[0]));
memset(dstImage->properties, 0, propertiesSize);
dstImage->numProperties = srcImage->numProperties;
for (size_t i = 0; i < srcImage->numProperties; ++i) {
memcpy(dstImage->properties[i].boxtype, srcImage->properties[i].boxtype, sizeof(srcImage->properties[i].boxtype));
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22 changes: 22 additions & 0 deletions tests/gtest/avifimagetest.cc
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Expand Up @@ -49,5 +49,27 @@ TEST(AvifImageTest, WriteImage) {
image.get(), (testing::TempDir() + "/avifimagetest.png").c_str()));
}

TEST(AvifImageTest, CopyRejectsTooManyProperties) {
ImagePtr src(avifImageCreateEmpty());
ImagePtr dst(avifImageCreateEmpty());
ASSERT_NE(src, nullptr);
ASSERT_NE(dst, nullptr);

const uint8_t property_type[4] = {'a', 'b', 'c', 'd'};
const uint8_t property_payload = 0;
ASSERT_EQ(avifImageAddOpaqueProperty(src.get(), property_type,
&property_payload,
sizeof(property_payload)),
AVIF_RESULT_OK);

src->numProperties =
std::numeric_limits<size_t>::max() / sizeof(avifImageItemProperty) + 1;
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@wantehchang wantehchang May 26, 2026

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This changes src to an invalid avifImage. (This is why the test has to change src->numProperties back to 1 at line 69 before the destructor of src is called.) This violates the API contract that src points to a valid avifImage.

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@wantehchang wantehchang May 26, 2026

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To drive home the necessity of this kind of API contract (whether explicit or implicit), suppose we change this line to the following instead:

    src->numProperties = 2;

It will also make src an invalid avifImage, but the avifImageCopy() function cannot possibly detect this kind of invalid input. So at some point a function has to require that the caller pass a valid input.

EXPECT_EQ(avifImageCopy(dst.get(), src.get(), AVIF_PLANES_ALL),
AVIF_RESULT_INVALID_ARGUMENT);
src->numProperties = 1;
EXPECT_EQ(dst->properties, nullptr);
EXPECT_EQ(dst->numProperties, 0u);
}

} // namespace
} // namespace avif