Crate c2pa_http 

C2PA manifest discovery over HTTP: the c2pa-manifest Link header.

When an asset is served over HTTP, a validator that finds no embedded Manifest Store should look for a Link header carrying rel="c2pa-manifest". This crate parses and emits that header, and provides a Tower middleware that attaches it to every response.

Scope

• link — parse and serialise the header per {RFC 8288}. No dependencies, operates on &str, usable under any HTTP stack.
• layer — the Tower Layer, behind the default tower feature.

Retrieving the manifest is left to the caller: this crate performs no network I/O, so it makes no decisions about timeouts, redirects, or trust. Error::Inaccessible exists so a caller that does fetch can report manifest.inaccessible through the same error type.

Examples

Advertise a manifest on every response:

use c2pa_http::ManifestLinkLayer;
use tower::ServiceBuilder;

let layer = ManifestLinkLayer::new("https://fabrikam.example/m.c2pa").unwrap();
let _service = ServiceBuilder::new().layer(layer);

Read one from a response you received:

use c2pa_http::link;

let header = r#"</style.css>; rel=preload, <https://a.example/m.c2pa>; rel="c2pa-manifest""#;
let found = link::extract([header]).unwrap();
assert_eq!(found.uri, "https://a.example/m.c2pa");

A target may also name a Manifest Store already embedded in the asset, through a JUMBF fragment. A reference to a specific manifest inside the store is not permitted, and the childlabel portion is discarded:

use c2pa_http::link;

let header = r#"<https://a.example/i.jpg#jumbf=c2pa/urn:uuid:1234>; rel="c2pa-manifest""#;
let found = link::extract([header]).unwrap();
assert!(found.is_embedded());
assert_eq!(found.uri, "https://a.example/i.jpg#jumbf=c2pa");

Precedence

For an HTML document that carries both an in-document manifest element and a Link header, the specification gives the header precedence. Discovery inside the document itself is c2pa-html’s job.

Re-exports

pub use error::Error;

pub use link::ManifestLink;

pub use link::REL;

pub use layer::append_to;

pub use layer::extract_from;

pub use layer::ManifestLinkLayer;

pub use layer::ManifestLinkService;

Modules

error

layer

A Tower Layer that advertises a C2PA Manifest Store on every response.

link

The c2pa-manifest link relation, parsed and serialised per {RFC 8288}.