commit 20cc2122a6b31075c0809988f65c6dd1dab1bbf8
parent b276d47adc82dbb94b5930b321d48ae0b4fb6b87
Author: Dylan ross <dylan.ssor@gmail.com>
Date: Wed, 1 Nov 2023 16:15:27 -0700
(PATCH) switches af relationship for a reference to the c2pa data to an array of references, one of which is the c2pa spec (#333)
* sets AF relationship of catalog to array instead of reference
* Add support for external manifest embedding of PDF
* adds error type
---------
Co-authored-by: Dylan Ross <dyross@adobe.com>
Co-authored-by: Maurice Fisher <mfisher@adobe.com>
Diffstat:
2 files changed, 101 insertions(+), 31 deletions(-)
diff --git a/sdk/src/asset_handlers/pdf.rs b/sdk/src/asset_handlers/pdf.rs
@@ -51,6 +51,11 @@ pub enum Error {
// the manifest bytes in the PDF's embedded files.
#[error("Unable to find C2PA manifest in the PDF's embedded files.")]
UnableToFindEmbeddedFileManifest,
+
+ /// This error occurs when we an error was encountered trying to find the PDF's C2PA embedded
+ /// file specification in the array of Associated Files defined in the catalog.
+ #[error("Unable to find a C2PA embedded file specification in PDF's associated files array")]
+ FindingC2PAFileSpec,
}
const C2PA_MIME_TYPE: &str = "application/x-c2pa-manifest-store";
@@ -98,16 +103,9 @@ impl C2paPdf for Pdf {
/// Determines if this PDF has a C2PA manifest embedded.
///
/// This is done by checking if the Associated File key of the catalog points to a
- /// [lopdf::Object::Dictionary] with an `AFRelationship` set to `C2PA_Manifest`.
+ /// [Object::Dictionary] with an `AFRelationship` set to `C2PA_Manifest`.
fn has_c2pa_manifest(&self) -> bool {
- self.document
- .catalog()
- .and_then(|catalog| catalog.get_deref(ASSOCIATED_FILE_KEY, &self.document))
- .and_then(Object::as_dict)
- .and_then(|dict| dict.get_deref(AF_RELATIONSHIP_KEY, &self.document))
- .and_then(Object::as_name)
- .map(|name| name == C2PA_RELATIONSHIP)
- .unwrap_or_default()
+ self.c2pa_file_spec_object_id().is_some()
}
/// Writes the provided `bytes` to the PDF as an `EmbeddedFile`.
@@ -116,7 +114,7 @@ impl C2paPdf for Pdf {
let file_stream_ref = self.add_c2pa_embedded_file_stream(bytes);
let file_spec_ref = self.add_embedded_file_specification(file_stream_ref);
- self.set_af_relationship(file_spec_ref)?;
+ self.push_associated_file(file_spec_ref)?;
let mut manifest_name_file_pair = vec![
Object::string_literal(CONTENT_CREDS),
@@ -194,7 +192,7 @@ impl C2paPdf for Pdf {
let file_stream_reference = self.add_c2pa_embedded_file_stream(bytes);
let file_spec_reference = self.add_embedded_file_specification(file_stream_reference);
- self.set_af_relationship(file_spec_reference)?;
+ self.push_associated_file(file_spec_reference)?;
self.add_file_attachment_annotation(file_spec_reference)?;
Ok(())
@@ -214,16 +212,15 @@ impl C2paPdf for Pdf {
/// separately, due to PDF's "Incremental Update" feature. See the spec for more details:
/// <https://c2pa.org/specifications/specifications/1.3/specs/C2PA_Specification.html#_embedding_manifests_into_pdfs>
fn read_manifest_bytes(&self) -> Result<Option<Vec<&[u8]>>, Error> {
- if !self.has_c2pa_manifest() {
+ let Some(id) = self.c2pa_file_spec_object_id() else {
return Ok(None);
};
Ok(Some(vec![
&self
.document
- .catalog()?
- .get_deref(ASSOCIATED_FILE_KEY, &self.document)?
- .as_dict()?
+ .get_object(id)
+ .and_then(Object::as_dict)?
.get_deref(b"EF", &self.document)?
.as_stream()?
.content,
@@ -237,10 +234,8 @@ impl C2paPdf for Pdf {
// Find the File Spec, which contains the reference to the manifest.
let file_spec_ref = self
- .document
- .catalog()?
- .get(ASSOCIATED_FILE_KEY)?
- .as_reference()?;
+ .c2pa_file_spec_object_id()
+ .ok_or_else(|| Error::NoManifest)?;
// Find the manifest's file stream.
let file_stream_ref = self
@@ -259,8 +254,8 @@ impl C2paPdf for Pdf {
self.remove_manifest_from_embedded_files()
.or_else(|_| self.remove_manifest_from_annotations())?;
- // Remove the AF_Relationship from the catalog.
- self.document.catalog_mut()?.remove(AF_RELATIONSHIP_KEY);
+ // Remove C2PA associated files from the `AF` key in the catalog.
+ self.remove_c2pa_file_spec_reference()?;
// Delete the manifest and its descriptor from the PDF
self.document.delete_object(file_stream_ref);
@@ -307,6 +302,58 @@ impl Pdf {
Ok(Self { document })
}
+ /// Returns a reference to the Associated Files array from the PDF's Catalog.
+ fn associated_files(&self) -> Result<&Vec<Object>, Error> {
+ Ok(self
+ .document
+ .catalog()?
+ .get_deref(ASSOCIATED_FILE_KEY, &self.document)?
+ .as_array()?)
+ }
+
+ /// Returns the [Object::ObjectId] of the C2PA File Spec Reference, if it is present in the
+ /// PDF's associated files array.
+ fn c2pa_file_spec_object_id(&self) -> Option<ObjectId> {
+ self.associated_files().ok()?.iter().find_map(|value| {
+ let Ok(reference) = value.as_reference() else {
+ return None;
+ };
+
+ let name = self
+ .document
+ .get_object(reference)
+ .and_then(Object::as_dict)
+ .and_then(|dict| dict.get_deref(AF_RELATIONSHIP_KEY, &self.document))
+ .and_then(Object::as_name)
+ .ok()?;
+
+ (name == C2PA_RELATIONSHIP).then_some(reference)
+ })
+ }
+
+ /// Removes the C2PA File Spec Reference if it exists in the Associated Files [Object::Array] of
+ /// PDF's catalog. This will return an [Err] if the PDF doesn't contain a C2PA File Spec
+ /// Reference.
+ fn remove_c2pa_file_spec_reference(&mut self) -> Result<(), Error> {
+ let c2pa_file_spec_reference = self
+ .c2pa_file_spec_object_id()
+ .ok_or_else(|| Error::FindingC2PAFileSpec)?;
+
+ self.document
+ .catalog_mut()?
+ .get_mut(ASSOCIATED_FILE_KEY)?
+ .as_array_mut()?
+ .retain(|v| {
+ let Ok(reference) = v.as_reference() else {
+ return true;
+ };
+
+ reference != c2pa_file_spec_reference
+ });
+
+ Ok(())
+ }
+
/// Adds the C2PA `Annotation` to the PDF.
///
/// ### Note:
@@ -361,16 +408,28 @@ impl Pdf {
Ok(())
}
- /// Sets the Associated File (/AF) key of the PDF to the provided embedded file spec reference.
- fn set_af_relationship(&mut self, embedded_file_spec_ref: ObjectId) -> Result<(), Error> {
- self.document
- .catalog_mut()?
- .set(ASSOCIATED_FILE_KEY, embedded_file_spec_ref);
+ /// Creates, or appends to, the Associated File (`AF`) array the embedded file spec reference of the
+ /// C2PA data.
+ fn push_associated_file(&mut self, embedded_file_spec_ref: ObjectId) -> Result<(), Error> {
+ let catalog = self.document.catalog_mut()?;
+ if catalog.get_mut(ASSOCIATED_FILE_KEY).is_err() {
+ // Add associated files array to catalog if it isn't already present.
+ catalog.set(ASSOCIATED_FILE_KEY, vec![]);
+ }
+
+ let associated_files = catalog.get_mut(ASSOCIATED_FILE_KEY)?;
+ let associated_files = match associated_files.as_reference() {
+ Ok(object_id) => self.document.get_object_mut(object_id)?,
+ _ => associated_files,
+ }
+ .as_array_mut()?;
+
+ associated_files.push(Reference(embedded_file_spec_ref));
Ok(())
}
- /// Adds the `Embedded File Specification` to the PDF document. Returns the [lopdf::Object::Reference]
+ /// Adds the `Embedded File Specification` to the PDF document. Returns the [Reference]
/// to the added `Embedded File Specification`.
fn add_embedded_file_specification(&mut self, file_stream_ref: ObjectId) -> ObjectId {
let embedded_file_stream = dictionary! {
@@ -386,7 +445,7 @@ impl Pdf {
}
/// Adds the provided `bytes` as a `StreamDictionary` to the PDF document. Returns the
- /// [lopdf::Object::Reference] of the added [lopdf::Object].
+ /// [Reference] of the added [Object].
fn add_c2pa_embedded_file_stream(&mut self, bytes: Vec<u8>) -> ObjectId {
let stream = Stream::new(
dictionary! {
@@ -651,7 +710,7 @@ mod tests {
pdf.document
.catalog_mut()
.unwrap()
- .set(ASSOCIATED_FILE_KEY, Object::Reference((100, 0)));
+ .set(ASSOCIATED_FILE_KEY, vec![Reference((100, 0))]);
assert!(matches!(pdf.read_manifest_bytes(), Ok(None)));
}
@@ -663,7 +722,7 @@ mod tests {
pdf.document
.catalog_mut()
.unwrap()
- .set(ASSOCIATED_FILE_KEY, Object::Reference((100, 0)));
+ .set(ASSOCIATED_FILE_KEY, Reference((100, 0)));
assert!(matches!(pdf.read_manifest_bytes(), Ok(None)));
}
diff --git a/sdk/src/asset_handlers/pdf_io.rs b/sdk/src/asset_handlers/pdf_io.rs
@@ -15,7 +15,7 @@ use std::{fs::File, path::Path};
use crate::{
asset_handlers::pdf::{C2paPdf, Pdf},
- asset_io::{AssetIO, CAIReader, CAIWriter, HashObjectPositions},
+ asset_io::{AssetIO, CAIReader, CAIWriter, ComposedManifestRef, HashObjectPositions},
CAIRead, Error,
Error::{JumbfNotFound, NotImplemented, PdfReadError},
};
@@ -108,6 +108,17 @@ impl AssetIO for PdfIO {
fn supported_types(&self) -> &[&str] {
&SUPPORTED_TYPES
}
+
+ fn composed_data_ref(&self) -> Option<&dyn ComposedManifestRef> {
+ Some(self)
+ }
+}
+
+impl ComposedManifestRef for PdfIO {
+ // Return entire CAI block as Vec<u8>
+ fn compose_manifest(&self, manifest_data: &[u8], _format: &str) -> Result<Vec<u8>, Error> {
+ Ok(manifest_data.to_vec())
+ }
}
#[cfg(test)]
