Bug:
The DGN compound-file reader walked FAT chains with a fixed
1,000,000-iteration guard - a step budget, not a byte budget. A
self-referential FAT entry (fat[s] = s) burns the whole budget reading
the same sector: 4.1 GB per call at 4 KiB sectors. Directory, mini
stream and miniFAT chains are alive simultaneously (about 12 GB peak) ->
allocator abort while merely selecting the file in the attach dialog.
Separately, models() inflated every model directory's streams (512 MB
each) with no total, and directory entries can all point at one shared
payload - 1.2 GB retained from a 4.3 MB file.
Reproduce:
1. Craft a ~1.5 KB CFB (sector shift 9) whose directory start sector's
FAT entry points at itself (zeroed FAT sector).
2. ATTACH and pick the file (any listing path parses the CFB).
3. Before: the directory chain grows to 4,000,000 entries from a
1536-byte file, then abort.
4. After: every chain is bounded by the file's own sector count -
instant, memory at most the file size.
5. For the models path: a file with 300 model dirs sharing a 4 MB
payload inflated to 1,258,291,200 bytes before; now it stops at the
file-scaled budget (max(file x 64, 256 MiB)).
Fix:
chain bounds itself by file bytes / sector size: a chain can only read
in-file sectors, and after that many steps it must have repeated one -
the walk is deterministic, so a repeat is a cycle that yields nothing
new. That is the strongest bound the format allows and it never
truncates a legitimate chain (each sector is read at most once). The
mini-stream loop uses the same argument over mini.len() / 64. models()
checks a file-scaled total budget before inflating each dir; later dirs
are dropped (earlier ones still load, name/table discovery degrades
gracefully). Tests: the hostile 1.5 KB file keeps all bytes <= file
size; the 300-model file stays within budget.
The byte count at 110 was read with direct indexing; a truncated element
now skips like every other field read does.
Co-Authored-By: Claude Opus 5.5 <[email protected]>
- V8 models are placed relative to their global origin (model header).
- A V8 model's extent is the union of its elements' stored ranges; a V7
model's text box is one text height tall.
- Files without a colour table use the standard DGN default table; colour
255 is read from the table's background entry.
- Colours from a file's colour table follow the background: near-white
colours swap with it, and over non-black backgrounds some shades drop a
step.
- DGN contrast pulls towards a pivot taken from the model's own colours,
after the fade, which is blended into the background first.
- Shared cells are read through their full 3D placement, so tilted
instances and 3D definitions are drawn in plan.
- Deleted V8 elements are skipped; lines along the model's extent stay in
the raster.
Co-Authored-By: Claude Opus 5.5 <[email protected]>
The DWF package reader, the DGN stream inflater and the new DGN
ExtendedColors scan each read a zlib/zip payload to its end, so a
crafted or corrupt file could inflate until memory ran out. Cap them:
1 GiB for a whole DWF package, 512 MiB per DGN stream, 4 MiB per
ExtendedColors record candidate - far above real files.
Co-Authored-By: Claude Opus 5.5 <[email protected]>
- Insert > Reference: the PDF Attach button becomes an Attach Underlay menu
(PDF / DWF / DGN); its face runs the last one chosen.
- DWFATTACH, DGNATTACH and ATTACH on a .dwf/.dwfx/.dgn open the Attach
dialog for that kind: sheets or models with thumbnails (one chosen),
placement, path type, file details with the sheet / model size, and for
DGN the conversion units (sub units offer 1 / sub units per master as the
scale).
- DGN V8 true colours come from the ExtendedColors record packed in the
non-model attributes stream; the colour word's high part numbers them.
- A DGN model's extent includes each text's box (its length along the
baseline and 1.5 x its height), as the reference sizes a model.
- DWFx text uses the family named in its embedded (deobfuscated) font.
- DWF contrast pivots at 0.73 once colours are turned over for a dark
background.
- Hairline strokes are drawn solid one pixel wide, and underlay rasters are
made at or below their size on screen so those lines stay unbroken.
Co-Authored-By: Claude Opus 5.5 <[email protected]>
- W2D: a stream cut off right after an extended opcode's '(' sliced its
body backwards and panicked.
- DGN V8: the compound-file header was indexed before its length was
known (a short file with the signature panicked), the sector shift was
taken on trust (0 or 1 underflowed `sector / 4 - 1` into an endless
loop), and the DIFAT chain count was unbounded. The header must now be
complete, the shift 9 or 12, and the chain no longer than the file.
Found fuzzing the #1514 readers with truncated and random input.
Co-Authored-By: Claude Opus 5.5 <[email protected]>
- PDFOSNAP, DWFOSNAP and DGNOSNAP are separate; UOSNAP sets them all and
reads 2 while they differ. Enable Snap switches the selected kind's.
- DWFCLIP / DGNCLIP clip their own kind with the kind's prompts and message;
CLIP routes DWF and DGN underlays there; Enter at a corner asks again.
- The right-edge underlay tools show for DWF and DGN too (import is PDF
only).
- Underlay layers: DGN levels (V8 level table, "Default" listed as "0"; V7
used levels named from the level name table), hidden through the layer
override data with the DGN placeholder string first; a plotted DWF has
none.
- V8 colour read from its colour word (by level, index, or a true colour
drawn as its nearest index); 3D V8 elements drawn in plan (lines, line
strings, ellipses and arcs by their orientation, text); a model's extent
includes its text.
- DWF 6 TrueType text (font, height, rotation from the font opcode) and DWFx
glyph runs are drawn; the default W2D colour map is the measured one.
- Contrast pulls lightness towards a per-kind pivot as measured (PDF 0.5,
DWF 0.243, DGN 0.65).
- Zoom extents includes raster images and underlays whose frames are hidden.
Co-Authored-By: Claude Opus 5.5 <[email protected]>
DWFATTACH / -DWFATTACH and DGNATTACH / -DGNATTACH attach a DWF / DWFx sheet
or a DGN (V7 or V8) model with the reference's prompts; ATTACH routes the
file types to them. The sheet or model is read into vector paths, drawn as a
transparent underlay raster (contrast, fade, monochrome and background
adjustment apply) and offers its geometry to object snaps. Definitions are
kept in ACAD_DWFDEFINITIONS / ACAD_DGNDEFINITIONS, the External References
palette lists and reloads them, and image textures get line-keeping mip
levels so thin underlay lines stay visible when zoomed out.
Co-Authored-By: Claude Opus 5.5 <[email protected]>
Karim Jerbi