Reject signed numbers in Content-Range parsing

Found while testing crates/fetch/src/lib.rs:465 (parse_content_range)

Co-Authored-By: Claude Haiku 5.5 <noreply@anthropic.com>
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

crates/fetch/src/lib.rs

@@ -466,16 +466,25 @@ fn parse_content_range(v: &str) -> Option<(u64, Option<u64>)> {
     let v = v.trim().strip_prefix("bytes")?.trim();
     let (range, total) = v.split_once('/')?;
     let (a, b) = range.split_once('-')?;
-    let (a, b) = (a.trim().parse::<u64>().ok()?, b.trim().parse::<u64>().ok()?);
+    let (a, b) = (digits(a)?, digits(b)?);
     if b < a {
         return None;
     }
     let total = match total.trim() {
         "*" => None,
-        t => Some(t.parse::<u64>().ok()?),
+        t => Some(digits(t)?),
     };
     Some((a, total))
 }
 
+/// A non-empty run of ASCII digits as a `u64` (no sign, unlike `str::parse`).
+fn digits(s: &str) -> Option<u64> {
+    let s = s.trim();
+    if s.is_empty() || !s.bytes().all(|b| b.is_ascii_digit()) {
+        return None;
+    }
+    s.parse().ok()
+}
+
 #[cfg(test)]
 mod tests;

crates/fetch/src/tests.rs

@@ -335,6 +335,10 @@ fn content_ranges() {
     assert_eq!(parse_content_range("bytes 0-0/*"), Some((0, None)));
     assert_eq!(parse_content_range("bytes 9-1/300"), None);
     assert_eq!(parse_content_range("items 1-2/3"), None);
+    assert_eq!(parse_content_range("bytes +100-+299/+300"), None);
+    assert_eq!(parse_content_range("bytes 100-+299/300"), None);
+    assert_eq!(parse_content_range("bytes 100-299/+300"), None);
+    assert_eq!(parse_content_range("bytes 1-/3"), None);
 }
 
 /// A bearer token goes only to https, only to the host the download began at, and only when there is one.