Grzegorz MartensandClaude Opus 5.5
0a00862e91
Main's #1143 (863af864a), merged in77b9cfa31, makes cos read a reference whose generation isn't its object's as null. The walk that finds what shares a /JBIG2Globals dictionary with what left fetched through `Document::get`, but remembered what it read by object number alone, so a reference of another generation and the object's own one shared what the first of them read: - What a parameters value names (`Run::names_in`): `/DecodeParms [10 1 R 10 0 R]` on an image that left, object 10 naming dictionary 9, read 10 1 R as null, named nothing, and remembered that for object 10. The 10 0 R after it found it, so nothing named 9, and the dictionary stayed in the file with the image another page kept. - A size, filters or parameters an image is stored again with (`Run::follow`): an image whose `/Width 11 1 R` reads as null can't be stored again, and refused the run alone. Once another image had read 11 0 R, it took that width and was stored with it. What an image names is now read by object number, whatever generation the reference gives (`Run::fetch_numbered`), in `names_in` and in the `/JBIG2Globals` chain alike: a reader that doesn't compare generations draws with that object, so what an image that left names this way may hold its shapes. That is how the chain already named `9 1 R` (the "another generation" way out), and how both read before #1143. What is read by number is remembered by number. The values an image is stored again with are read as cos reads them, and remembered by number and generation, so a reference of another generation reads its own way. `kept`'s comment said a reference reads the object of its number whatever its generation, which is no longer so for a full save. It says how `reachable_objects` reads one now. The README and `Run`'s comments say which reads take the number and which the generation too. Tests: - `a_redacted_scans_shared_jbig2_dictionary_leaves_the_file` gains three ways out: - parameters through another generation, then their own; - parameters through another generation alone; - a `/JBIG2Globals` reference to a reference of another generation. - `a_size_through_another_generation_isnt_the_one_its_own_reference_reads` stores no image with the width another reference read. It refuses instead. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01AmsdeUCdTaD72jkDw2pJKY
pdfcraft-redact
Layer L4 (may use edit): redaction, architecture §11.2.
// Marks are Redact annotations (pdfcraft-annot: Shape::Redact { quads, overlay }).
let marks: Vec<Mark> = marks(&doc); // page, areas (user space), fill, overlay text
let report = apply(&mut doc, None)?; // everything, or Some(&[pages])
clear_marks(&mut doc, None)?; // remove marks without applying
apply removes, under every marked area:
- text: glyphs are cut out of
Tj/TJ/'/"and replaced by aTJdisplacement of the same advance, so the rest of the line keeps its exact position. Widths come from/Widths,/W//DW(composite fonts, embedded CMaps with codespace and CID ranges), Type 3 font matrices, and approximations for the standard 14. A glyph goes when it overlaps an area by more than a fifth of its size (or a point) both ways; zero-size text goes when its origin is inside; - images: fully covered → removed; partly covered → a copy with the covered pixels cleared
(8/16-bit and 1/2/4-bit images, image masks; Flate/LZW/RL/A85/AHx, and CCITT fax or JBIG2 as
the last filter, decoded through
ImageBudget::decode, a JBIG2 image with its/JBIG2Globals;/DecodeParmsgiven by reference, numbers inside included, count). The copy is Flate, or for a one-bit image of one component (a scan as a rule) CCITT Group 4, or JBIG2 when it was JBIG2, whichever is smallest as stored, coded from the cleared samples; it refers to no globals. Globals hold the shapes of every image that shares them (a scan's pages, often), those of marks under the area included, so whatever left the document, by any route, takes its globals with it on the full rewrite: anything else the save would keep that names them, or a copy of them (the same bytes once decoded), is stored again without them, as a copy is (Flate, Group 4 or JBIG2, whichever is smallest;Report::images_restored). When one can't be (it isn't JBIG2, its colour space is known to have more than one component, it has no size or one past what redaction clears, its data is in another file, or it can't be decoded), or something else refers to them,applyrefuses and changes nothing (RedactError::SharedJbig2Globals).remove_hiddentakes them out the same way, but it has changed the document by the time it refuses: a caller passes a copy it can drop. Another dictionary holding the same shapes in other bytes isn't found, nor is a copy nothing names, and an image that hasn't left keeps its globals with its pixels: one another page still draws, or one something that doesn't draw it still refers to. What an image names as globals is read by object number, whatever generation a reference gives, as a reader that doesn't compare generations draws it (cos reads such a reference as null); what one is stored again with, its size, filters and parameters, is read as cos reads it. Finding what to store again reads each object at most once for each way it is read (a/JBIG2Globalschain named part way, or a ring of references or a chain of more than 32, may be read again), and what it fetches, remembers and decodes (a decode that fails counting as much as it was allowed, and an image the dictionaries it names) counts against one budget for the run; past it the redaction is refused (RedactError::SharedJbig2Budget). The images stored again, and the dictionaries read to know copies of them, are decoded within the run's image allowance, every filter stage and the JBIG2 decoder's own work included, after what clearing spent: past itapplyis refused as one clearing too many images is (RedactError::ImagesPastAllowance), andremove_hidden, which chose no pages, as one past the run's budget. Codecs redaction doesn't decode (DCT, JPX) are removed whole (fail-closed), and so is a JBIG2 image whose page isn't its size (the renderer draws the whole page into the image, so the rows cleared wouldn't be the ones shown) or of more than one bit or component, and Group 3 on bytes (/K0 or more,/EncodedByteAlign): PdfCraft's renderer draws some of its layouts (the fill ending each end-of-line code on a byte) as other rows than the decoder reads, so a mark over what is shown needn't cover what is cleared; inline images under an area are removed. Images with separate/SMaskor/Maskdata, and images whose data decodes to more than three times their declared raster and a byte per row, plus 4 KiB (ASCIIHex text broken into lines under Flate is a little over twice; for a fax image's code, about a byte per pixel), are removed whole; cleared copies drop/Alternatesso alternate pixels cannot survive; A run that would decode more of its images than one redaction may (pdfcraft_cos::ImageBudget, filters, decoders and pixels alike) is refused and changes nothing: such an image can't be cleared, and removing it whole would take what no mark covers with it. - vectors: covered paths are removed; partly covered paths and shadings are clipped so nothing paints inside the areas;
- form XObjects: rewritten recursively into new objects (pages sharing the original keep it);
- annotations whose rectangle overlaps (with their pop-ups and their replies,
/IRT), and form fields with a widget under a mark; - the marks themselves, replaced by boxes in their fill colour (and overlay text) drawn into the
page as a
/PCMark /Redactionstream.
A verification pass re-reads each redacted page and fails the operation if any glyph or inline
image is still under an area. It checks every content stream the page had, whatever its
dictionary calls it; only the overlay streams this apply added (Report::overlays) are skipped.
Text is placed with the font and size set by Tf or by an ExtGState's /Font through gs, and a
form XObject starts from the text state of the content that draws it. Content that can't be
decoded makes the operation fail rather than leave it unredacted, and so does an inline image the
renderer's tokenizer reads no image for (RedactError::Unreadable): where the page's operators
resume after it would be a guess. A Redact annotation with neither a usable /QuadPoints array nor a usable
/Rect makes it fail with RedactError::UnreadableMark before anything changes, instead of
skipping that mark. The count covers the marks on the pages being applied.
Tiling-pattern cells are separate streams. Applying a mark removes a pattern resource when no
surviving paint uses it. If a cell remains reachable after rewriting the selected pages and may
contain text, images, replacement descriptions, or unreadable content, Apply refuses with a
RedactError::Pattern and restores the document and pending marks. This includes patterns owned
by Forms and patterns inherited by Forms. Vector-only retained cells remain supported. The
bounded check is conservative: an unrelated retained pattern on a selected page can also cause
refusal when its content cannot be proven safe. If a selected page had a pattern resource, the
check covers all pages after rewriting so another page cannot keep the same cell in the saved PDF.
Before changing any page, apply prepares the redaction appearances with a shared 8 MiB
budget for their uncompressed PDF content across the selected pages. It bounds repeated-text
counts and working line buffers before allocating them, and measures and encodes each repeated
line once. Invalid or excessive appearances return RedactError::OverlayLimit without changing
the document. Reduce the marked area, disable repeated text, or apply fewer pages at a time.
This limits appearance generation; it is not a limit on the input PDF or the whole process's memory.
Structure cleanup resolves named MCIDs and indirect content references. Form content
references are updated to the cleaned copy; unchanged sibling descriptions remain. The structure
tree's object references (/OBJR) to the annotations and form fields apply removes are dropped,
as Sanitize drops them, so a full rewrite of a tagged PDF can't keep a removed comment or field value.
A tree where that can't be done (an element written in place, or one too large to walk) makes
apply fail with RedactError::Tags rather than leave the annotation reachable.
Replacement descriptions (/Alt, /ActualText, /E) are removed from marked-content spans
changed by cleanup, from every structure element above them (found through both /P and /K),
and from elements that lose an annotation reference, which also lose /T. An element written in
place above one whose descriptions go makes apply fail with RedactError::Tags. Unchanged
spans retain their descriptions; unused property entries are retired during redaction
and hidden-content cleanup, including aliases in shared/inherited resources. Descriptions still
used by surviving pages or forms are kept.
A redacted page that inherits /Resources from the page tree gets them pinned (by reference;
a direct inherited dictionary is made one shared object first) before it is rewritten. The parent's
/Resources is then retired unless another page still inherits it, so it cannot keep a removed
XObject reachable. Surviving form XObjects lose the resource entries for removed XObjects their own
content doesn't draw, for the same reason. Pages that aren't redacted are left untouched.
Remove hidden information / Sanitize
let found = sanitize::scan(&doc); // [(Hidden, count)] per category
sanitize::remove_hidden(&mut doc, &[Hidden::Comments])?; // chosen categories
sanitize::sanitize(&mut doc)?; // all of them
Categories: metadata (/Info, XMP), file attachments, comments, form fields (flattened so the
values stay visible), hidden text (render modes 3 and 7, or wholly off the page), hidden layers
(content of off optional-content groups, then the groups), bookmarks, links/actions/JavaScript,
and /PieceInfo private data. XMP metadata, private data, associated files (/AF) and
additional actions (/AA) are removed from every object reachable from the catalog that owns
them (images, fonts, Forms, annotations and fields as well as the catalog and pages), never from
name maps such as resource dictionaries. Content is read strictly: a page whose content can't be
read in full is refused, not cleaned in part. Both make the next save a full rewrite.
patterns finds phone numbers, e-mail addresses, credit card numbers (Luhn-checked), US Social
Security numbers and dates for Search & Redact.
A phone label such as Tel. or Fax: also enables Italian international geographic numbers with a slash, such as Tel. +39 0426/123456 or Fax: +390426/123456 (#3205 follow-up).
The country code and national number are matched together, with the significant initial 0 and 6 to 11 national digits described in the AGCOM numbering plan published by ITU.
This narrow case accepts at most one space after +39 and one slash immediately after the area code; international slash numbers without a phone label, or with country codes other than +39, remain unsupported.
Patterns are heuristic: dates, protocol identifiers and longer number runs are retained, and users still need to review the marks before applying them.
codes holds the redaction code sets (U.S. FOIA and U.S. Privacy Act exemptions):
CodeSet::from_id("foia")?.overlay(&["(b)(6)"]) gives the overlay text for the picked codes.
Custom code sets aren't supported yet.
Not yet: pattern locales, struct-tree/alt-text cleanup, re-encoding of DCT images (they are removed instead).