fix(cms): reject malformed hex data in .look LUTs (#8657)

Co-authored-by: Lucenx9 <185146821+Lucenx9@users.noreply.github.com>

crates/cms/src/lutfile.rs

@@ -221,7 +221,14 @@ pub fn parse_look(text: &str) -> Result<LutFile, LutError> {
     };
     let size: usize = tag("size").and_then(|s| s.parse().ok()).ok_or_else(|| LutError("no <size> in .look".into()))?;
     let (entries, _) = checked_data_len(size)?;
-    let hex: Vec<u8> = tag("data").ok_or_else(|| LutError("no <data> in .look".into()))?.bytes().filter(u8::is_ascii_hexdigit).collect();
+    let hex: Vec<u8> = tag("data").ok_or_else(|| LutError("no <data> in .look".into()))?.bytes().filter(|b| !b.is_ascii_whitespace()).collect();
+    if hex.iter().any(|b| !b.is_ascii_hexdigit()) {
+        return err("invalid hexadecimal <data> in .look");
+    }
+    // Each float needs eight hex digits; as_chunks would silently discard a partial value.
+    if !hex.len().is_multiple_of(8) {
+        return err("incomplete float in .look <data>");
+    }
     let nib = |c: u8| (c as char).to_digit(16).unwrap_or(0) as u8;
     let bytes: Vec<u8> = hex.as_chunks::<2>().0.iter().map(|p| nib(p[0]) << 4 | nib(p[1])).collect();
     let floats: Vec<f32> = bytes.as_chunks::<4>().0.iter().map(|b| f32::from_le_bytes([b[0], b[1], b[2], b[3]])).collect();
@@ -456,6 +463,38 @@ DOMAIN_MAX 0.5 1 1
         assert_eq!(parse("a.look", xml.as_bytes()).unwrap().data, id.data);
     }
 
+    #[test]
+    fn look_rgb_and_rgba_allow_whitespace_in_hex_data() {
+        let id = LutFile::identity(2);
+        for channels in [3, 4] {
+            let mut hex = String::new();
+            for rgb in id.data.as_chunks::<3>().0 {
+                for value in rgb.iter().copied().chain((channels == 4).then_some(1.0)) {
+                    for byte in value.to_le_bytes() {
+                        hex.push_str(&format!("{byte:02x} \t\r\n"));
+                    }
+                }
+            }
+            let xml = format!("<look><size>2</size><data>\"{hex}\"</data></look>");
+            assert_eq!(parse("valid.look", xml.as_bytes()).unwrap().data, id.data);
+        }
+    }
+
+    #[test]
+    fn look_rejects_partial_floats_and_invalid_hex() {
+        let id = LutFile::identity(2);
+        let hex: String = id.data.iter().flat_map(|v| v.to_le_bytes()).map(|b| format!("{b:02X}")).collect();
+        for suffix in ["0", "00", "0000", "000000", "G", "é"] {
+            let xml = format!("<look><size>2</size><data>{hex}{suffix}</data></look>");
+            assert!(parse("bad.look", xml.as_bytes()).is_err(), "accepted malformed suffix {suffix:?}");
+        }
+        let invalid = hex.replacen('0', "G", 1);
+        let xml = format!("<look><size>2</size><data>{invalid}</data></look>");
+        assert!(parse("bad.look", xml.as_bytes()).unwrap_err().0.contains("invalid hexadecimal"));
+        let xml = format!("<look><size>2</size><data>{hex}00</data></look>");
+        assert!(parse("bad.look", xml.as_bytes()).unwrap_err().0.contains("incomplete float"));
+    }
+
     #[test]
     fn look_3d_size_exponent_overflow_is_rejected() {
         let text = format!("<look><size>{}</size><data>00</data></look>", usize::MAX);