🛡️ Sentinel: [MEDIUM] Add size safety limit for 3MF slice_info.config extraction

.jules/sentinel.md

@@ -0,0 +1,4 @@
+## 2026-08-19 - Bounded member decompression for 3MF zip archives
+**Vulnerability:** `read_3mf_estimate` extracted `slice_info.config` from `.3mf` zip packages using unbounded `zf.read()`, risking memory exhaustion / Zip Bomb DoS when reading untrusted models.
+**Learning:** Even internal helper methods like `read_3mf_estimate` process user-provided or network-downloaded 3MF files.
+**Prevention:** Check `info.file_size` against a safety limit (10MB) and use explicit read bounds (`fh.read(limit)`) before parsing XML/JSON from zip archives.

bambu_cli/slicer/estimate.py

@@ -11,6 +11,7 @@
 _MAX_GRAMS = 10000.0
 
 GCODE_READ_BYTES = 65536  # 64 KB
+SLICE_INFO_READ_BYTES = 10 * 1024 * 1024  # 10 MB safety limit for XML config (Zip Bomb protection)
 
 
 @dataclass(frozen=True)
@@ -22,8 +23,7 @@ class Estimate:
 def _parse_slice_info(xml_text: str) -> tuple[int | None, float | None]:
     """Parse prediction (seconds) and weight (grams) from slice_info.config XML.
 
-    Uses xml.etree.ElementTree which is safe for local files we produced;
-    this is not parsing untrusted network XML.
+    Uses xml.etree.ElementTree to parse bounded metadata XML from .3mf packages.
     """
     try:
         root = ET.fromstring(xml_text)  # nosec B314 — local file produced by OrcaSlicer, not network input
@@ -114,10 +114,15 @@ def read_3mf_estimate(path: str) -> Estimate:
                     break
 
             if slice_info_name is not None:
-                xml_text = zf.read(slice_info_name).decode("utf-8", errors="replace")
-                seconds, grams = _parse_slice_info(xml_text)
-                if seconds is not None or grams is not None:
-                    return Estimate(seconds, grams)
+                info = zf.getinfo(slice_info_name)
+                # Security: Enforce size limit to prevent memory exhaustion / Zip Bomb DoS on untrusted .3mf files
+                if info.file_size <= SLICE_INFO_READ_BYTES:
+                    with zf.open(slice_info_name) as fh:
+                        xml_bytes = fh.read(SLICE_INFO_READ_BYTES)
+                    xml_text = xml_bytes.decode("utf-8", errors="replace")
+                    seconds, grams = _parse_slice_info(xml_text)
+                    if seconds is not None or grams is not None:
+                        return Estimate(seconds, grams)
                 # slice_info.config was present but yielded nothing usable
                 # (malformed XML, or only implausible values).  Fall through to
                 # the gcode header rather than reporting "unknown" -- a truncated

tests/test_slicer_estimate.py

@@ -71,6 +71,19 @@ def test_unparseable_slice_info_falls_back_to_gcode(tmp_path):
     assert read_3mf_estimate(path).seconds == 2700
 
 
+def test_oversized_slice_info_falls_back_to_gcode(tmp_path):
+    """An oversized slice_info.config (>10MB limit) must be skipped and fall back to gcode header."""
+    oversized_data = b"a" * (10 * 1024 * 1024 + 1)
+    path = _write_zip(
+        tmp_path / "oversized.3mf",
+        {
+            "Metadata/slice_info.config": oversized_data,
+            "Metadata/plate_1.gcode": b"; model printing time: 20m 0s\n",
+        },
+    )
+    assert read_3mf_estimate(path).seconds == 1200
+
+
 def test_slice_info_with_only_implausible_values_falls_back_to_gcode(tmp_path):
     """A well-formed config carrying junk must not shadow a good gcode header."""
     bad_config = (