CVE-2023-36307: Program crashes when processing certain maliciously crafted images by pic4xiu · Pull Request #6 · SimonWaldherr/zplgfa

I found that in the ConvertToGraphicField function, in the first layer of for loop, if the width is 0, the calculation of line[lineIndex] will cause the program to go out of bounds. Because the line definition statement is line := make([]uint8, width), the program directly crashes.

func ConvertToGraphicField(source image.Image, graphicType GraphicType) string {
    var gfType string
    var lastLine string
    size := source.Bounds().Size()
    width := size.X / 8
    height := size.Y
    if size.Y%8 != 0 {
        width = width + 1
    }

    var GraphicFieldData string

    for y := 0; y < size.Y; y++ {
        line := make([]uint8, width)
        lineIndex := 0
        index := uint8(0)
        currentByte := line[lineIndex]//line[0] is out of bounds
        ...

The reason why did not choose to introduce error to indicate that the program went wrong is that it seems reasonable to return an empty string, because the image width is 0.