Struct CallbackSigner 

pub struct CallbackSigner {
    pub context: *const (),
    pub callback: Box<CallbackFunc>,
    pub alg: SigningAlg,
    pub certs: Vec<u8>,
    pub reserve_size: usize,
    pub tsa_url: Option<String>,
}

Defines a signer that uses a callback to sign data.

The private key should only be known by the callback.

Fields

context: *const ()

An opaque context for the signer, used to store any necessary state.

callback: Box<CallbackFunc>

The callback to use to sign data.

alg: SigningAlg

The signing algorithm to use.

certs: Vec<u8>

The public certificates to use in PEM format.

reserve_size: usize

A max size to reserve for the signature.

tsa_url: Option<String>

The optional URL of a Time Stamping Authority.

Implementations

impl CallbackSigner

pub fn new<F, T>(callback: F, alg: SigningAlg, certs: T) -> Self

where F: Fn(*const (), &[u8]) -> Result<Vec<u8>, Error> + Send + Sync + 'static, T: Into<Vec<u8>>,

Create a new callback signer.

pub fn set_tsa_url<S: Into<String>>(self, url: S) -> Self

Set a time stamping authority URL to call when signing.

pub fn set_context(self, context: *const ()) -> Self

Set a context value for the signer.

This can be used to store any necessary state for the callback. Safety: The context must be valid for the lifetime of the signer. There is no Rust memory management for the context since it may also come from FFI.

pub fn ed25519_sign(data: &[u8], private_key: &[u8]) -> Result<Vec<u8>>

Sign data using an Ed25519 private key. This static function is provided for testing with CallbackSigner. For a released product the private key should be stored securely. The signing should be done in a secure environment. The private key should not be exposed to the client. Example: (only for testing)

use c2pa::{CallbackSigner, SigningAlg};

const CERTS: &[u8] = include_bytes!("../tests/fixtures/certs/ed25519.pub");
const PRIVATE_KEY: &[u8] = include_bytes!("../tests/fixtures/certs/ed25519.pem");

let ed_signer =
    |_context: *const _, data: &[u8]| CallbackSigner::ed25519_sign(data, PRIVATE_KEY);
let signer = CallbackSigner::new(ed_signer, SigningAlg::Ed25519, CERTS);

Trait Implementations

impl AsyncSigner for CallbackSigner

fn sign<'life0, 'async_trait>( &'life0 self, data: Vec<u8>, ) -> Pin<Box<dyn Future<Output = Result<Vec<u8>>> + Send + 'async_trait>>

where Self: 'async_trait, 'life0: 'async_trait,

Returns a new byte array which is a signature over the original.

fn alg(&self) -> SigningAlg

Returns the algorithm of the Signer.

fn certs(&self) -> Result<Vec<Vec<u8>>>

Returns the certificates as a Vec containing a Vec of DER bytes for each certificate.

fn reserve_size(&self) -> usize

Returns the size in bytes of the largest possible expected signature. Signing will fail if the result of the sign function is larger than this value.

fn time_authority_url(&self) -> Option<String>

URL for time authority to time stamp the signature

fn timestamp_request_headers(&self) -> Option<Vec<(String, String)>>

Additional request headers to pass to the time stamp authority.

fn timestamp_request_body(&self, message: &[u8]) -> Result<Vec<u8>>

fn send_timestamp_request<'life0, 'life1, 'async_trait>( &'life0 self, message: &'life1 [u8], ) -> Pin<Box<dyn Future<Output = Option<Result<Vec<u8>>>> + Send + 'async_trait>>

where Self: Sync + 'async_trait, 'life0: 'async_trait, 'life1: 'async_trait,

Request RFC 3161 timestamp to be included in the manifest data structure.

fn ocsp_val<'life0, 'async_trait>( &'life0 self, ) -> Pin<Box<dyn Future<Output = Option<Vec<u8>>> + Send + 'async_trait>>

where Self: Sync + 'async_trait, 'life0: 'async_trait,

OCSP response for the signing cert if available This is the only C2PA supported cert revocation method. By pre-querying the value for a your signing cert the value can be cached taking pressure off of the CA (recommended by C2PA spec)

fn direct_cose_handling(&self) -> bool

If this returns true the sign function is responsible for for direct handling of the COSE structure.

fn dynamic_assertions(&self) -> Vec<Box<dyn AsyncDynamicAssertion>>

Returns a list of dynamic assertions that should be included in the manifest.

fn async_raw_signer(&self) -> Option<Box<&dyn AsyncRawSigner>>

If this struct also implements or wraps AsyncRawSigner, it should return a reference to that trait implementation.

impl Default for CallbackSigner

fn default() -> Self

Returns the “default value” for a type.

impl Signer for CallbackSigner

fn sign(&self, data: &[u8]) -> Result<Vec<u8>>

Returns a new byte array which is a signature over the original.

fn alg(&self) -> SigningAlg

Returns the algorithm of the Signer.

fn certs(&self) -> Result<Vec<Vec<u8>>>

Returns the certificates as a Vec containing a Vec of DER bytes for each certificate.

fn reserve_size(&self) -> usize

Returns the size in bytes of the largest possible expected signature. Signing will fail if the result of the sign function is larger than this value.

fn time_authority_url(&self) -> Option<String>

URL for time authority to time stamp the signature

fn timestamp_request_headers(&self) -> Option<Vec<(String, String)>>

Additional request headers to pass to the time stamp authority.

fn timestamp_request_body(&self, message: &[u8]) -> Result<Vec<u8>>

fn send_timestamp_request(&self, message: &[u8]) -> Option<Result<Vec<u8>>>

Request RFC 3161 timestamp to be included in the manifest data structure.

fn ocsp_val(&self) -> Option<Vec<u8>>

OCSP response for the signing cert if available This is the only C2PA supported cert revocation method. By pre-querying the value for a your signing cert the value can be cached taking pressure off of the CA (recommended by C2PA spec)

fn direct_cose_handling(&self) -> bool

If this returns true the sign function is responsible for for direct handling of the COSE structure.

fn dynamic_assertions(&self) -> Vec<Box<dyn DynamicAssertion>>

Returns a list of dynamic assertions that should be included in the manifest.

fn raw_signer(&self) -> Option<Box<&dyn RawSigner>>

If this struct also implements or wraps RawSigner, it should return a reference to that trait implementation.

impl Send for CallbackSigner

impl Sync for CallbackSigner