PDF export: bound a colorized image's color channel

A colorized image's color channel is the paint's samples repeated once a
pixel, and nothing bounded its size: an image colorized in Registration in
a document with many spot swatches could allocate without limit, and an
overflowing length panicked inside repeat. The length is now computed with
checked arithmetic and refused above MAX_RASTER_ALLOC, the image's own
decode budget, and the export leaves such an image out with the existing
"an image couldn't be decoded" warning instead of drawing it uncolored.

crates/pdf/src/export/images.rs

@@ -3,6 +3,12 @@ use super::{Arc, BlendMode, Color, Exporter, Image, NodeKind, Paint, Rect, Size,
 use krilla::color::device_n::{Colorant, DeviceNSpace, Process};
 use krilla::image::{BitsPerComponent, CustomImage, ImageColorspace};
 
+/// The byte count of a repeated color channel, within [`vectorcraft_doc::MAX_RASTER_ALLOC`].
+fn tinted_color_len(samples: usize, pixels: usize) -> Option<usize> {
+    let bytes = samples.checked_mul(pixels)?;
+    (u64::try_from(bytes).ok()? <= vectorcraft_doc::MAX_RASTER_ALLOC).then_some(bytes)
+}
+
 /// A colorized image's pixels: one color in every pixel, shown as much as its soft mask says.
 #[derive(Clone, Hash)]
 struct Tinted {
@@ -52,8 +58,9 @@ impl Exporter<'_> {
     /// every process ink and every spot ink of the document, other colors in gray, RGB or CMYK as
     /// the Output settings write them. The coverage is resampled as the Compression settings ask
     /// ([`crate::images::coverage_sized`]). `None` when the paint isn't a solid color or the pixels
-    /// can't be decoded; cached like [`Self::load_image`]. With `interpolate` (and the export's own
-    /// setting), viewers may smooth it.
+    /// can't be decoded or its color channel exceeds [`vectorcraft_doc::MAX_RASTER_ALLOC`]; cached
+    /// like [`Self::load_image`]. With `interpolate` (and the export's own setting), viewers may
+    /// smooth it.
     pub(super) fn colorized_image(&mut self, im: &vectorcraft_doc::ImageObject, paint: &Paint, interpolate: bool) -> Option<Image> {
         let Paint::Solid { color, swatch, tint } = paint else { return None };
         let size = placed_size(im);
@@ -96,6 +103,7 @@ impl Exporter<'_> {
                 other => (other.to_rgb().map(q).to_vec(), ImageColorspace::Rgb),
             },
         };
+        tinted_color_len(samples.len(), n)?;
         let color = Arc::new(samples.repeat(n));
         let img = Image::from_custom(Tinted { color, alpha: Arc::new(alpha), width, height, space, device_n }, interpolate).ok();
         self.images.insert(cache, img.clone());
@@ -245,3 +253,16 @@ pub(super) fn embed(blob: &vectorcraft_doc::ImageBlob, interpolate: bool, sixtee
         Some(Image::from_rgba8(rgba.into_raw(), w, h))
     })
 }
+
+#[cfg(test)]
+mod tests {
+    use super::tinted_color_len;
+
+    #[test]
+    fn tinted_color_rejects_oversized_and_overflowing_buffers() {
+        let max = usize::try_from(vectorcraft_doc::MAX_RASTER_ALLOC).unwrap_or(usize::MAX);
+        assert_eq!(tinted_color_len(4, max / 4), Some(max));
+        assert_eq!(tinted_color_len(4, max / 4 + 1), None);
+        assert_eq!(tinted_color_len(4, usize::MAX), None);
+    }
+}

crates/pdf/src/export/nodes.rs

@@ -1,4 +1,4 @@
-use super::exporter::{address, blend, color, constant_mask, cover, in_range, norm, rects_overlap, rule, to_path, writable, xf};
+use super::exporter::{UNDECODED, address, blend, color, constant_mask, cover, in_range, norm, rects_overlap, rule, to_path, writable, xf};
 use super::{
     Affine, AppearanceItem, BezPath, BlendMode, Exporter, Fill, FillRule, LineCap, LineJoin, Mark, Node, NodeKind, NormalizedF32, Paint, Path, Rect,
     Shape, Stroke, StrokeAlign, StrokeDash, StrokeLayer, Surface, WrittenShape, krilla, stroke,
@@ -182,10 +182,18 @@ impl Exporter<'_> {
                 self.shape(s, n, &bp, *rule, page);
             }
             NodeKind::Text(t) => self.text(s, n, t, page),
-            NodeKind::Image(im) => {
-                let colorized = n.extras().colorize.as_deref().and_then(|p| self.colorized_image(im, p, !n.extras().pixelated));
-                self.image(s, im, colorized.or(alpha), n.extras().pixelated)
-            }
+            NodeKind::Image(im) => match n.extras().colorize.as_deref() {
+                Some(p @ Paint::Solid { .. }) => {
+                    if writable(s, im.xf, Rect::new(0.0, 0.0, im.width.max(1).into(), im.height.max(1).into())) {
+                        if let Some(colorized) = self.colorized_image(im, p, !n.extras().pixelated) {
+                            self.image(s, im, Some(colorized), n.extras().pixelated);
+                        } else {
+                            self.warn(UNDECODED);
+                        }
+                    }
+                }
+                _ => self.image(s, im, alpha, n.extras().pixelated),
+            },
             NodeKind::SymbolInstance { symbol, xf } => {
                 // Within the objects a frame may draw of symbol instances, as on screen: nested
                 // instances multiply.