c2pa-zip 0.2.0

Overview

Implements the ZIP embedding method from the C2PA Technical Specification. Many document formats are ZIP archives with a fixed internal layout — EPUB, Office Open XML (DOCX/XLSX/PPTX), OpenDocument (ODT/ODS/ODP) and OpenXPS — and all embed a C2PA Manifest Store through this single transport.

The Manifest Store is stored as a dedicated ZIP entry at a fixed location:

Embedding appends the manifest entry before the central directory, so existing entries keep their byte offsets; the central directory and end-of-central-directory record are then rebuilt. All parsing is bounds-checked against untrusted input, and ZIP64 archives are rejected (fail-closed) rather than mis-parsed.

Zero dependencies.

Quick Start

[dependencies]
c2pa-zip = "0.1"

Embed a manifest

use c2pa_zip::embed_manifest;

let doc: &[u8] = /* .epub / .docx / .odt / .oxps bytes */;
let manifest: &[u8] = /* C2PA Manifest Store bytes */;

// Insert (or replace) the manifest entry; existing entries stay byte-stable.
let signed = embed_manifest(doc, manifest).unwrap();

Read a manifest

use c2pa_zip::read_manifest;

// Some(bytes) when a manifest is present, None when the archive has none.
let manifest = read_manifest(&signed).unwrap();

Remove a manifest

use c2pa_zip::remove_manifest;

let stripped = remove_manifest(&signed).unwrap();

Verify structurally

use c2pa_zip::verify;

let report = verify(&signed).unwrap();
// report.has_manifest, report.manifest_len, report.is_valid_zip

Design

• The Manifest Store is a single stored (uncompressed) ZIP entry at META-INF/content_credential.c2pa
• embed_manifest replaces any existing manifest entry, so the archive always carries at most one; when none is present the existing entries keep their exact byte offsets
• remove_manifest rebuilds the archive without the manifest entry, recomputing local-header offsets and the central directory
• verify reports transport-level structure only: whether the archive parses and whether a manifest is present
• ZIP64 archives (identified by sentinel values in the EOCD or central directory) are rejected; a trailing ZIP comment is tolerated when locating the EOCD

Scope

This crate is the ZIP transport only: it reads, writes, and removes a C2PA Manifest Store stored as a ZIP entry. Manifest construction, signing, and hard/soft binding (the collection-data-hash) are out of scope; use the c2pa SDK for those. verify performs structural checks (presence + parseability), not hard-binding validation.

Related Crates

Part of a family of single-purpose crates, one per C2PA embedding method. Each is standalone and independently versioned.

Security

Found a vulnerability? Please report it privately — see SECURITY.md.

License

Licensed under either of Apache License, Version 2.0 or MIT License at your option.

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