fix: limit JPG and PNG pixels to prevent decompression bomb

backend/internal/utils/image/validation_test.go

@@ -0,0 +1,58 @@
+package profilepicture
+
+import (
+	"bytes"
+	"encoding/binary"
+	"hash/crc32"
+	"image"
+	"image/png"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestCreateProfilePictureRejectsOversizedPixelCountBeforeDecode(t *testing.T) {
+	_, err := CreateProfilePicture(bytes.NewReader(pngHeaderWithDimensions(12_000, 12_000)))
+
+	require.ErrorIs(t, err, ErrInvalidImage)
+	require.ErrorIs(t, err, errImageDimensionsTooLarge)
+}
+
+func TestCreateProfilePictureAcceptsImageWithinLimits(t *testing.T) {
+	var input bytes.Buffer
+	require.NoError(t, png.Encode(&input, image.NewNRGBA(image.Rect(0, 0, 400, 300))))
+
+	output, err := CreateProfilePicture(bytes.NewReader(input.Bytes()))
+	require.NoError(t, err)
+
+	config, format, err := image.DecodeConfig(output)
+	require.NoError(t, err)
+	require.Equal(t, "png", format)
+	require.Equal(t, 300, config.Width)
+	require.Equal(t, 300, config.Height)
+}
+
+func TestStripMetadataRejectsOversizedPixelCount(t *testing.T) {
+	_, err := StripMetadata(bytes.NewReader(pngHeaderWithDimensions(12_000, 12_000)), "png")
+
+	require.ErrorIs(t, err, ErrInvalidImage)
+	require.ErrorIs(t, err, errImageDimensionsTooLarge)
+}
+
+func pngHeaderWithDimensions(width, height uint32) []byte {
+	var out bytes.Buffer
+	out.Write([]byte("\x89PNG\r\n\x1a\n"))
+
+	const headerLength = 13
+	data := make([]byte, headerLength)
+	binary.BigEndian.PutUint32(data[0:4], width)
+	binary.BigEndian.PutUint32(data[4:8], height)
+	data[8] = 8
+
+	_ = binary.Write(&out, binary.BigEndian, uint32(headerLength))
+	out.WriteString("IHDR")
+	out.Write(data)
+	_ = binary.Write(&out, binary.BigEndian, crc32.ChecksumIEEE(append([]byte("IHDR"), data...)))
+
+	return out.Bytes()
+}