From a50e1491a4d0138fd7fca936407d7716450db6ed Mon Sep 17 00:00:00 2001 From: mtlcl410 <2368091+mtlcl410@users.noreply.github.com> Date: Fri, 30 Oct 2026 08:59:03 +0800 Subject: [PATCH] M12: a picture an XFA form links is drawn from the PDF's XFAImages name tree MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit A template's without inline data is now found in the catalog's /Names /XFAImages tree, keyed by the URI the template writes (XFA 3.3 pp. 257-258, "Storing Images Inside PDF"). Only that tree is looked in; a link is never followed outside the file. The tree walk is bounded (depth, nodes, names, a seen-set), and so are the bytes read. Co-Authored-By: Claude Opus 5.5 Claude-Session: https://claude.ai/code/session_01Pq7HyCfwzyRXj4VfQAVVdv --- crates/xfa/src/fixtures.rs | 39 ++++++++ crates/xfa/src/layout/draw.rs | 2 +- crates/xfa/src/layout/field.rs | 2 +- crates/xfa/src/lib.rs | 4 +- crates/xfa/src/linked_images.rs | 158 ++++++++++++++++++++++++++++++++ crates/xfa/src/model.rs | 3 + crates/xfa/src/parse.rs | 3 +- crates/xfa/src/script.rs | 4 +- crates/xfa/src/tests.rs | 57 ++++++++++++ 9 files changed, 267 insertions(+), 5 deletions(-) create mode 100644 crates/xfa/src/linked_images.rs diff --git a/crates/xfa/src/fixtures.rs b/crates/xfa/src/fixtures.rs index 8f6e0f7ee8..3fe12b7af0 100644 --- a/crates/xfa/src/fixtures.rs +++ b/crates/xfa/src/fixtures.rs @@ -739,3 +739,42 @@ if (this.rawValue == "1") { "## .to_string() } + +/// A form whose two draws link their pictures instead of embedding them: `.\logo.png`, which the +/// PDF keeps in its `XFAImages` name tree (a [`tiny_png`], under a `Kids` node, as producers +/// split the tree), and `.\missing.png`, which it doesn't (XFA 3.3 pp. 257–258). +pub fn linked_image_shell() -> Vec { + linked_image_shell_with(b"<< /Kids [7 0 R] >>", br"<< /Limits [(.\\logo.png) (.\\logo.png)] /Names [(.\\logo.png) 8 0 R] >>") +} + +/// [`linked_image_shell`] with its own name tree: `root` is object 6 (the tree the catalog names), +/// `kid` object 7, and object 8 the PNG. +pub fn linked_image_shell_with(root: &[u8], kid: &[u8]) -> Vec { + let xdp = r##" + + + +"##; + let mut png = format!("<< /Length {} >>\nstream\n", TINY_PNG.len()).into_bytes(); + png.extend_from_slice(TINY_PNG); + png.extend_from_slice(b"\nendstream"); + let objs: Vec> = vec![ + b"<< /Type /Catalog /Pages 2 0 R /NeedsRendering true /AcroForm << /XFA 5 0 R /Fields [] >> /Names << /XFAImages 6 0 R >> >>".to_vec(), + b"<< /Type /Pages /Kids [3 0 R] /Count 1 >>".to_vec(), + b"<< /Type /Page /Parent 2 0 R /MediaBox [0 0 612 792] /Contents 4 0 R >>".to_vec(), + b"<< /Length 44 >>\nstream\nBT /F1 12 Tf 72 700 Td (Please wait...) Tj ET\nendstream".to_vec(), + format!("<< /Length {} >>\nstream\n{xdp}\nendstream", xdp.len()).into_bytes(), + root.to_vec(), + kid.to_vec(), + png, + ]; + assemble(objs) +} diff --git a/crates/xfa/src/layout/draw.rs b/crates/xfa/src/layout/draw.rs index f6520c1628..eb04fd934e 100644 --- a/crates/xfa/src/layout/draw.rs +++ b/crates/xfa/src/layout/draw.rs @@ -233,7 +233,7 @@ impl Layouter<'_> { let inner = rect.inset(&d.common.margin); match &d.value { Value::Text(_) | Value::Rich(_) => self.draw_value_text(&d.value, inner, &ctx.font, &ctx.para), - Value::Image { content_type, data } => self.draw_image(data, content_type, inner), + Value::Image { content_type, data, .. } => self.draw_image(data, content_type, inner), Value::Line { slope_up, edge } => { if !edge.visible() { return Ok(()); diff --git a/crates/xfa/src/layout/field.rs b/crates/xfa/src/layout/field.rs index cc15f16788..991eed63d1 100644 --- a/crates/xfa/src/layout/field.rs +++ b/crates/xfa/src/layout/field.rs @@ -95,7 +95,7 @@ impl Layouter<'_> { let box_ = ui.inset(&f.ui_margin); match (&from_data, &f.value) { (Some(d), _) => self.draw_image(d, "", box_)?, - (None, Value::Image { content_type, data }) => self.draw_image(data, content_type, box_)?, + (None, Value::Image { content_type, data, .. }) => self.draw_image(data, content_type, box_)?, _ => {} } // Then the field itself, which clicking gives a new picture. diff --git a/crates/xfa/src/lib.rs b/crates/xfa/src/lib.rs index 7e63218c90..0927325fd5 100644 --- a/crates/xfa/src/lib.rs +++ b/crates/xfa/src/lib.rs @@ -11,6 +11,7 @@ pub mod data; pub mod fixtures; pub mod image; pub mod layout; +pub mod linked_images; pub mod model; pub mod packets; pub mod parse; @@ -156,7 +157,8 @@ pub fn render_into(doc: &mut Document) -> Result { if packets.xdp.trim().is_empty() { return Err(XfaError::Malformed("the XFA packets hold no template".into())); } - let (tpl, parse_warnings) = parse(&packets.xdp)?; + let (mut tpl, mut parse_warnings) = parse(&packets.xdp)?; + parse_warnings.extend(linked_images::resolve(&mut tpl, doc)); let data = parse_datasets(&packets.xdp); let laid = apply_overrides(&tpl, &overrides(doc)); let mut form = layout(&laid, data.as_ref())?; diff --git a/crates/xfa/src/linked_images.rs b/crates/xfa/src/linked_images.rs new file mode 100644 index 0000000000..8dd66f36ff --- /dev/null +++ b/crates/xfa/src/linked_images.rs @@ -0,0 +1,158 @@ +//! Pictures a template links instead of embedding (``). Since XFA 2.6 a form +//! keeps them in its PDF: each image file is a stream holding the file's bytes, named in the +//! `XFAImages` name tree of the catalog's `Names` dictionary by the URI the template writes (XFA +//! 3.3 pp. 257–258, "Storing Images Inside PDF"). Only that tree is looked in: as the spec warns, +//! a form that isn't trusted must not have its links followed outside the file. + +use std::collections::{HashMap, HashSet}; + +use pdfcraft_cos::{Document, ObjRef, Object}; + +use crate::model::{Field, Node, Subform, Template, Value}; + +/// Most nodes of the name tree visited, and most names kept from it. +const MAX_TREE_NODES: usize = 4096; +const MAX_NAMES: usize = 4096; +/// Deepest the name tree is followed. +const MAX_DEPTH: usize = 32; +/// Largest picture taken from the file, as for a picture written into the template. +const MAX_IMAGE: usize = 32 << 20; +/// Most bytes of pictures taken from the file in all. +const MAX_TOTAL: usize = 128 << 20; +/// Deepest the template is walked. +const MAX_TEMPLATE_DEPTH: usize = 256; + +/// The `XFAImages` name tree: each name, as text, and the object it names. +fn names(doc: &Document) -> HashMap { + let mut out = HashMap::new(); + let Some(root) = doc.root() else { return out }; + let catalog = doc.get(root); + let tree = + catalog.as_dict().and_then(|c| c.get(b"Names")).map(|n| doc.resolve(n)).and_then(|n| n.as_dict().and_then(|d| d.get(b"XFAImages")).cloned()); + let Some(tree) = tree else { return out }; + let mut seen: HashSet = HashSet::new(); + let mut visited = 0usize; + let mut stack = vec![(tree, 0usize)]; + while let Some((node, depth)) = stack.pop() { + if depth > MAX_DEPTH || visited >= MAX_TREE_NODES || out.len() >= MAX_NAMES { + break; + } + visited += 1; + if let Some(r) = node.as_ref() + && !seen.insert(r) + { + continue; + } + let node = doc.resolve(&node); + let Some(d) = node.as_dict() else { continue }; + if let Some(pairs) = d.get(b"Names").map(|n| doc.resolve(n)).and_then(|n| n.as_array().cloned()) { + for pair in pairs.chunks(2) { + if let [key, value] = pair + && let Some(key) = doc.resolve(key).as_string() + { + out.entry(key.to_text()).or_insert_with(|| value.clone()); + if out.len() >= MAX_NAMES { + break; + } + } + } + } + if let Some(kids) = d.get(b"Kids").map(|k| doc.resolve(k)).and_then(|k| k.as_array().cloned()) { + stack.extend(kids.into_iter().map(|k| (k, depth + 1))); + } + } + out +} + +/// Pictures found so far by their link, read from the file once each. +struct Found<'a> { + doc: &'a Document, + names: HashMap, + read: HashMap>>, + total: usize, + warnings: Vec, +} + +impl Found<'_> { + /// The bytes of the picture linked as `href`, when the file holds it. + fn get(&mut self, href: &str) -> Option> { + if let Some(data) = self.read.get(href) { + return data.clone(); + } + let data = self.load(href); + self.read.insert(href.to_string(), data.clone()); + data + } + + fn load(&mut self, href: &str) -> Option> { + let object = self.names.get(href)?; + let object = self.doc.resolve(object); + let Object::Stream(s) = &*object else { return None }; + let data = match s.decoded_within(MAX_IMAGE) { + Ok(d) => d, + Err(_) => { + self.warnings.push(format!("a picture the form keeps in the file ({href}) could not be read; it is left out")); + return None; + } + }; + if self.total.saturating_add(data.len()) > MAX_TOTAL { + self.warnings.push("the pictures the form keeps in the file are larger than 128 MB in all; the rest are left out".into()); + return None; + } + self.total = self.total.saturating_add(data.len()); + Some(data) + } + + fn value(&mut self, v: &mut Value) { + if let Value::Image { data, href: Some(href), .. } = v + && data.is_empty() + && let Some(found) = self.get(href) + { + *data = found; + } + } + + fn field(&mut self, f: &mut Field) { + self.value(&mut f.value); + if let Some(c) = f.caption.as_mut() { + self.value(&mut c.value); + } + } + + fn nodes(&mut self, nodes: &mut [Node], depth: usize) { + if depth > MAX_TEMPLATE_DEPTH { + return; + } + for n in nodes { + match n { + Node::Subform(s) => self.subform(s, depth + 1), + Node::Area(a) => self.nodes(&mut a.children, depth + 1), + Node::Field(f) => self.field(f), + Node::Draw(d) => self.value(&mut d.value), + Node::ExclGroup(g) => g.fields.iter_mut().for_each(|f| self.field(f)), + } + } + } + + fn subform(&mut self, s: &mut Subform, depth: usize) { + if let Some(set) = s.page_set.as_mut() { + for area in &mut set.areas { + self.nodes(&mut area.items, depth + 1); + } + } + self.nodes(&mut s.children, depth); + } +} + +/// Give the pictures `tpl` links to (and doesn't embed) the data `doc` keeps for them. A link +/// the file holds nothing for stays empty. What couldn't be read is returned as warnings. +pub fn resolve(tpl: &mut Template, doc: &Document) -> Vec { + let names = names(doc); + if names.is_empty() { + return Vec::new(); + } + let mut found = Found { doc, names, read: HashMap::new(), total: 0, warnings: Vec::new() }; + found.subform(&mut tpl.root, 0); + found.warnings.dedup(); + found.warnings +} diff --git a/crates/xfa/src/model.rs b/crates/xfa/src/model.rs index 0fac8db18e..70db1615af 100644 --- a/crates/xfa/src/model.rs +++ b/crates/xfa/src/model.rs @@ -598,6 +598,9 @@ pub enum Value { Image { content_type: String, data: Vec, + /// Where the template links the picture from (`href`), when it does: its data is then + /// found in the PDF ([`crate::linked_images`]). + href: Option, }, /// A diagonal line through the box: `\` (top-left to bottom-right) or `/`. Line { diff --git a/crates/xfa/src/parse.rs b/crates/xfa/src/parse.rs index 838d1730ea..2527311fd3 100644 --- a/crates/xfa/src/parse.rs +++ b/crates/xfa/src/parse.rs @@ -401,7 +401,8 @@ fn parse_value(n: Option, warnings: &mut Vec) -> Value { warnings.push("an image is larger than 32 MB; it is left out".into()); return Value::Empty; } - return Value::Image { content_type: c.attribute("contentType").unwrap_or("").to_string(), data }; + let href = c.attribute("href").map(str::trim).filter(|h| !h.is_empty()).map(str::to_string); + return Value::Image { content_type: c.attribute("contentType").unwrap_or("").to_string(), data, href }; } "line" => { return Value::Line { slope_up: c.attribute("slope") == Some("/"), edge: child(c, "edge").map(parse_edge).unwrap_or_default() }; diff --git a/crates/xfa/src/script.rs b/crates/xfa/src/script.rs index 6946aa9b1c..005f56a640 100644 --- a/crates/xfa/src/script.rs +++ b/crates/xfa/src/script.rs @@ -656,7 +656,9 @@ pub fn template_of(doc: &Document) -> Result { if packets.xdp.trim().is_empty() { return Err(XfaError::Malformed("the XFA packets hold no template".into())); } - crate::parse(&packets.xdp).map(|(t, _)| t) + let (mut tpl, _) = crate::parse(&packets.xdp)?; + crate::linked_images::resolve(&mut tpl, doc); + Ok(tpl) } /// Whether the template field at `som` is multiline text without a fixed height. diff --git a/crates/xfa/src/tests.rs b/crates/xfa/src/tests.rs index e424be5441..bd359d5ac8 100644 --- a/crates/xfa/src/tests.rs +++ b/crates/xfa/src/tests.rs @@ -4145,3 +4145,60 @@ fn clear_password_values_clears_static_xfa_password_fields() { let packets = read_packets(&doc).unwrap().unwrap(); assert!(!packets.xdp.contains("hunter2"), "{}", packets.xdp); } + +/// A picture the template links (`href`) is drawn from the `XFAImages` name tree the PDF keeps +/// it in (XFA 3.3 pp. 257–258), through the tree's `Kids`. A link the file holds nothing for +/// stays out, as before, and is never looked for outside the file. +#[test] +fn a_linked_picture_is_drawn_from_the_pdfs_xfa_images() { + let mut doc = Document::open(Arc::new(crate::fixtures::linked_image_shell())).unwrap(); + let mut tpl = crate::script::template_of(&doc).unwrap(); + let mut pictures = Vec::new(); + let mut walk = |nodes: &[Node]| { + for n in nodes { + if let Node::Subform(s) = n { + for c in &s.children { + if let Node::Draw(d) = c + && let Value::Image { data, href, .. } = &d.value + { + pictures.push((href.clone(), data.len())); + } + } + } + } + }; + walk(&tpl.root.children); + assert_eq!(pictures, vec![(Some(r".\logo.png".into()), crate::fixtures::tiny_png().len()), (Some(r".\missing.png".into()), 0)]); + assert!(crate::linked_images::resolve(&mut tpl, &doc).is_empty(), "nothing to say of a link the file doesn't hold"); + let report = render_into(&mut doc).unwrap(); + let doc = Document::open(Arc::new(write_incremental(&doc, &SaveOptions::default()).unwrap())).unwrap(); + let images = doc + .object_numbers() + .into_iter() + .filter( + |n| matches!(&*doc.get(pdfcraft_cos::ObjRef { num: *n, generation: 0 }), Object::Stream(s) if s.dict.name(b"Subtype") == Some(b"Image")), + ) + .count(); + assert_eq!(images, 2, "the linked PNG and its soft mask"); + assert_eq!(report.warnings.iter().filter(|w| w.contains("not a JPEG, PNG")).count(), 1, "only the missing one: {:?}", report.warnings); +} + +/// A hostile `XFAImages` tree neither hangs nor panics: `Kids` that lead back to themselves, a +/// name that isn't a string, and a name for something that isn't a stream. The picture is then +/// left out, as a link the file holds nothing for. +#[test] +fn a_hostile_xfa_images_tree_is_walked_once_and_gives_nothing() { + for (root, kid) in [ + (&b"<< /Kids [6 0 R 7 0 R] >>"[..], &b"<< /Kids [6 0 R 7 0 R] /Names [42 8 0 R] >>"[..]), + (&b"<< /Names [(.\\logo.png) 7 0 R] >>"[..], &b"<< /Kids [6 0 R] >>"[..]), + (&b"<< /Kids 7 0 R >>"[..], &b"[6 0 R]"[..]), + ] { + let mut doc = Document::open(Arc::new(crate::fixtures::linked_image_shell_with(root, kid))).unwrap(); + let mut tpl = crate::script::template_of(&doc).unwrap(); + assert!(crate::linked_images::resolve(&mut tpl, &doc).is_empty()); + let report = render_into(&mut doc).unwrap(); + assert!(report.warnings.iter().any(|w| w.contains("not a JPEG, PNG")), "{:?}", report.warnings); + let images = doc.object_numbers().into_iter().filter(|n| matches!(&*doc.get(pdfcraft_cos::ObjRef { num: *n, generation: 0 }), Object::Stream(s) if s.dict.name(b"Subtype") == Some(b"Image"))).count(); + assert_eq!(images, 0, "no picture drawn"); + } +}