feat(crypto): Introduce new (experimental) rust_native_crypto featu…

…re (#850)

Move ed25519-dalek support from WASM (synchronous) to rust_native module.

Document which crypto implementation is used when.

internal/crypto/Cargo.toml

@@ -31,6 +31,7 @@ rustdoc-args = ["--cfg", "docsrs"]
 
 [features]
 json_schema = ["dep:schemars"]
+rust_native_crypto = ["dep:ed25519-dalek"]
 
 [dependencies]
 asn1-rs = "0.6.2"
@@ -43,6 +44,7 @@ c2pa-status-tracker = { path = "../status-tracker", version = "0.2.0" }
 ciborium = "0.2.2"
 const-hex = "1.14"
 coset = "0.3.1"
+ed25519-dalek = { version = "2.1.1", features = ["alloc", "digest", "pem", "pkcs8"], optional = true }
 getrandom = { version = "0.2.7", features = ["js"] }
 hex = "0.4.3"
 nom = "7.1.3"
@@ -101,8 +103,12 @@ web-sys = { version = "0.3.58", features = [
 getrandom = { version = "0.2.7", features = ["js"] }
 js-sys = "0.3.58"
 
+[dev-dependencies]
+ed25519-dalek = { version = "2.1.1", features = ["alloc", "digest", "pem", "pkcs8"] }
+
 [target.'cfg(not(target_arch = "wasm32"))'.dev-dependencies]
 actix = "0.13.1"
+ed25519-dalek = { version = "2.1.1", features = ["alloc", "digest", "pem", "pkcs8"] }
 
 [target.'cfg(target_arch = "wasm32")'.dev-dependencies]
 wasm-bindgen-test = "0.3.31"

internal/crypto/README.md

@@ -4,6 +4,61 @@
 
 This crate contains some of the internal cryptography implementation that is shared between the [c2pa crate](https://crates.io/crates/c2pa) and the [CAWG identity SDK crate](https://crates.io/crates/cawg-identity). It is not intended to be used directly in most cases.
 
+## Crate features
+
+This crate has two features, neither of which are enabled by default:
+
+* `json_schema`: Used by c2pa-rs documentation code to generate JSON schema for types defined in this crate.
+* `rust_native_crypto`: Where available, prefer Rust-native cryptography libraries for raw signature and validation implementations. (Experimental)
+
+## Cryptographic library support
+
+`c2pa-crypto` will use different cryptography libraries depending on which platform and feature flags are used:
+
+### Signing (synchronous or asynchronous)
+
+| C2PA `SigningAlg` | Default (*) | `feature = "rust_native_crypto"` (*) | WASM |
+| --- | --- | --- | --- |
+| `es256` | OpenSSL | OpenSSL | ❌ |
+| `es384` | OpenSSL | OpenSSL | ❌ |
+| `es512` | OpenSSL | OpenSSL | ❌ |
+| `ed25519` | OpenSSL | `ed25519-dalek` | `ed25519-dalek` |
+| `ps256` | OpenSSL | OpenSSL | ❌ |
+| `ps384` | OpenSSL | OpenSSL | ❌ |
+| `ps512` | OpenSSL | OpenSSL | ❌ |
+
+(*) Applies to all supported platforms except WASM <br />
+❌ = not supported
+
+### Validation (synchronous)
+
+| C2PA `SigningAlg` | Default (*) | `feature = "rust_native_crypto"` (*) | WASM |
+| --- | --- | --- | --- |
+| `es256` | OpenSSL | OpenSSL | `p256` |
+| `es384` | OpenSSL | OpenSSL | `p384` |
+| `es512` | OpenSSL | OpenSSL | ❌ |
+| `ed25519` | OpenSSL | `ed25519-dalek` | `ed25519-dalek` |
+| `ps256` | OpenSSL | OpenSSL | `rsa` |
+| `ps384` | OpenSSL | OpenSSL | `rsa` |
+| `ps512` | OpenSSL | OpenSSL | `rsa` |
+
+(*) Applies to all supported platforms except WASM <br />
+❌ = not supported
+
+### Validation (asynchronous)
+
+| C2PA `SigningAlg` | Default (*) | `feature = "rust_native_crypto"` (*) | WASM |
+| --- | --- | --- | --- |
+| `es256` | OpenSSL | OpenSSL | WebCrypto |
+| `es384` | OpenSSL | OpenSSL | WebCrypto |
+| `es512` | OpenSSL | OpenSSL | WebCrypto |
+| `ed25519` | OpenSSL | `ed25519-dalek` | `ed25519-dalek` |
+| `ps256` | OpenSSL | OpenSSL | `rsa` |
+| `ps384` | OpenSSL | OpenSSL | `rsa` |
+| `ps512` | OpenSSL | OpenSSL | `rsa` |
+
+(*) Applies to all supported platforms except WASM
+
 ### Contributions and feedback
 
 We welcome contributions to this project. For information on contributing, providing feedback, and about ongoing work, see [Contributing](https://github.com/contentauth/c2pa-rs/blob/main/CONTRIBUTING.md). For additional information on nightly builds and testing, see [Contributing to the project](docs/project-contributions.md).

internal/crypto/src/raw_signature/mod.rs

@@ -18,6 +18,9 @@ pub(crate) mod oids;
 #[cfg(not(target_arch = "wasm32"))]
 pub(crate) mod openssl;
 
+#[cfg(any(target_arch = "wasm32", feature = "rust_native_crypto", test))]
+pub(crate) mod rust_native;
+
 pub(crate) mod signer;
 pub use signer::{
     async_signer_from_cert_chain_and_private_key, signer_from_cert_chain_and_private_key,

internal/crypto/src/raw_signature/openssl/mod.rs

@@ -21,8 +21,8 @@
 mod cert_chain;
 
 mod ffi_mutex;
-pub use ffi_mutex::{OpenSslMutex, OpenSslMutexUnavailable};
+pub(crate) use ffi_mutex::{OpenSslMutex, OpenSslMutexUnavailable};
 
 pub(crate) mod check_certificate_trust;
 pub(crate) mod signers;
-pub mod validators;
+pub(crate) mod validators;

internal/crypto/src/raw_signature/rust_native/mod.rs

@@ -0,0 +1,24 @@
+// Copyright 2025 Adobe. All rights reserved.
+// This file is licensed to you under the Apache License,
+// Version 2.0 (http://www.apache.org/licenses/LICENSE-2.0)
+// or the MIT license (http://opensource.org/licenses/MIT),
+// at your option.
+
+// Unless required by applicable law or agreed to in writing,
+// this software is distributed on an "AS IS" BASIS, WITHOUT
+// WARRANTIES OR REPRESENTATIONS OF ANY KIND, either express or
+// implied. See the LICENSE-MIT and LICENSE-APACHE files for the
+// specific language governing permissions and limitations under
+// each license.
+
+#![allow(unused)] // Not used on all platforms or all configs
+
+//! Experimental support for synchronous raw signatures using Rust-native
+//! crates. Intended mostly for the synchronous use cases on WASM, but may
+//! eventually be used on all platforms.
+//!
+//! At the moment, does not offer support for all C2PA-supported cryptography
+//! algorithms.
+
+pub(crate) mod signers;
+pub(crate) mod validators;

internal/crypto/src/raw_signature/webcrypto/signers/mod.rs → internal/crypto/src/raw_signature/rust_native/signers/mod.rs

@@ -1,4 +1,4 @@
-// Copyright 2024 Adobe. All rights reserved.
+// Copyright 2025 Adobe. All rights reserved.
 // This file is licensed to you under the Apache License,
 // Version 2.0 (http://www.apache.org/licenses/LICENSE-2.0)
 // or the MIT license (http://opensource.org/licenses/MIT),
@@ -11,6 +11,9 @@
 // specific language governing permissions and limitations under
 // each license.
 
+//! This module binds Rust native logic for generating raw signatures to this
+//! crate's [`RawSigner`] trait.
+
 use crate::raw_signature::{RawSigner, RawSignerError, SigningAlg};
 
 mod ed25519_signer;
@@ -39,7 +42,7 @@ pub(crate) fn signer_from_cert_chain_and_private_key(
         )),
 
         _ => Err(RawSignerError::InternalError(format!(
-            "unsupported algorithm: {alg}"
+            "unsupported signing algorithm {alg}"
         ))),
     }
 }

internal/crypto/src/raw_signature/webcrypto/validators/ed25519_validator.rs → internal/crypto/src/raw_signature/rust_native/validators/ed25519_validator.rs

@@ -27,7 +27,7 @@ impl RawSignatureValidator for Ed25519Validator {
         data: &[u8],
         public_key: &[u8],
     ) -> Result<(), RawSignatureValidationError> {
-        let (_, public_key) = SubjectPublicKeyInfo::from_der(&public_key)
+        let (_, public_key) = SubjectPublicKeyInfo::from_der(public_key)
             .map_err(|_| RawSignatureValidationError::InvalidPublicKey)?;
 
         let public_key = public_key
@@ -43,15 +43,15 @@ impl RawSignatureValidator for Ed25519Validator {
         }
 
         let mut public_key_slice: [u8; PUBLIC_KEY_LENGTH] = Default::default();
-        public_key_slice.copy_from_slice(&public_key);
+        public_key_slice.copy_from_slice(public_key);
 
         let vk = VerifyingKey::from_bytes(&public_key_slice)
             .map_err(|_| RawSignatureValidationError::InvalidPublicKey)?;
 
         let ed_sig = Signature::from_slice(sig)
             .map_err(|_| RawSignatureValidationError::InvalidSignature)?;
 
-        match vk.verify(&data, &ed_sig) {
+        match vk.verify(data, &ed_sig) {
             Ok(_) => Ok(()),
             Err(_) => Err(RawSignatureValidationError::SignatureMismatch),
         }

internal/crypto/src/raw_signature/rust_native/validators/mod.rs

@@ -0,0 +1,30 @@
+// Copyright 2025 Adobe. All rights reserved.
+// This file is licensed to you under the Apache License,
+// Version 2.0 (http://www.apache.org/licenses/LICENSE-2.0)
+// or the MIT license (http://opensource.org/licenses/MIT),
+// at your option.
+
+// Unless required by applicable law or agreed to in writing,
+// this software is distributed on an "AS IS" BASIS, WITHOUT
+// WARRANTIES OR REPRESENTATIONS OF ANY KIND, either express or
+// implied. See the LICENSE-MIT and LICENSE-APACHE files for the
+// specific language governing permissions and limitations under
+// each license.
+
+//! This module binds Rust native logic for generating raw signatures to this
+//! crate's [`RawSignatureValidator`] trait.
+
+use bcder::Oid;
+
+use crate::raw_signature::{oids::*, RawSignatureValidator, SigningAlg};
+
+mod ed25519_validator;
+pub use ed25519_validator::Ed25519Validator;
+
+/// Return a validator for the given signing algorithm.
+pub fn validator_for_signing_alg(alg: SigningAlg) -> Option<Box<dyn RawSignatureValidator>> {
+    match alg {
+        SigningAlg::Ed25519 => Some(Box::new(Ed25519Validator {})),
+        _ => None,
+    }
+}

internal/crypto/src/raw_signature/signer.rs

@@ -165,19 +165,23 @@ pub fn signer_from_cert_chain_and_private_key(
     alg: SigningAlg,
     time_stamp_service_url: Option<String>,
 ) -> Result<Box<dyn RawSigner + Send + Sync>, RawSignerError> {
-    #[cfg(not(target_arch = "wasm32"))]
+    #[cfg(any(target_arch = "wasm32", feature = "rust_native_crypto"))]
     {
-        return crate::raw_signature::openssl::signers::signer_from_cert_chain_and_private_key(
+        match crate::raw_signature::rust_native::signers::signer_from_cert_chain_and_private_key(
             cert_chain,
             private_key,
             alg,
-            time_stamp_service_url,
-        );
+            time_stamp_service_url.clone(),
+        ) {
+            Ok(signer) => return Ok(signer),
+            Err(RawSignerError::InternalError(_)) => (),
+            Err(err) => return Err(err),
+        }
     }
 
-    #[cfg(all(target_arch = "wasm32", not(target_os = "wasi")))]
+    #[cfg(not(target_arch = "wasm32"))]
     {
-        return crate::raw_signature::webcrypto::signers::signer_from_cert_chain_and_private_key(
+        return crate::raw_signature::openssl::signers::signer_from_cert_chain_and_private_key(
             cert_chain,
             private_key,
             alg,

internal/crypto/src/raw_signature/validator.rs

@@ -65,6 +65,15 @@ pub trait AsyncRawSignatureValidator {
 /// Which validators are available may vary depending on the platform and
 /// which crate features were enabled.
 pub fn validator_for_signing_alg(alg: SigningAlg) -> Option<Box<dyn RawSignatureValidator>> {
+    #[cfg(any(target_arch = "wasm32", feature = "rust_native_crypto"))]
+    {
+        if let Some(validator) =
+            crate::raw_signature::rust_native::validators::validator_for_signing_alg(alg)
+        {
+            return Some(validator);
+        }
+    }
+
     #[cfg(not(target_arch = "wasm32"))]
     if let Some(validator) =
         crate::raw_signature::openssl::validators::validator_for_signing_alg(alg)

internal/crypto/src/raw_signature/webcrypto/async_validators/ed25519_validator.rs

@@ -31,7 +31,7 @@ impl AsyncRawSignatureValidator for Ed25519Validator {
     ) -> Result<(), RawSignatureValidationError> {
         // Sync and async cases are identical for Ed25519.
 
-        let sync_validator = crate::raw_signature::webcrypto::validators::Ed25519Validator {};
+        let sync_validator = crate::raw_signature::rust_native::validators::Ed25519Validator {};
         sync_validator.validate(sig, data, public_key)
     }
 }

internal/crypto/src/raw_signature/webcrypto/mod.rs

@@ -25,8 +25,7 @@ pub(crate) use async_validators::{
 };
 
 pub(crate) mod check_certificate_trust;
-pub(crate) mod signers;
-pub mod validators;
+pub(crate) mod validators;
 
 mod window_or_worker;
 pub use window_or_worker::{WasmCryptoError, WindowOrWorker};

internal/crypto/src/raw_signature/webcrypto/validators/mod.rs

@@ -21,9 +21,6 @@ use crate::raw_signature::{oids::*, RawSignatureValidator, SigningAlg};
 mod ecdsa_validator;
 pub use ecdsa_validator::EcdsaValidator;
 
-mod ed25519_validator;
-pub use ed25519_validator::Ed25519Validator;
-
 mod rsa_legacy_validator;
 pub(crate) use rsa_legacy_validator::RsaLegacyValidator;
 
@@ -36,10 +33,10 @@ pub fn validator_for_signing_alg(alg: SigningAlg) -> Option<Box<dyn RawSignature
         SigningAlg::Es256 => Some(Box::new(EcdsaValidator::Es256)),
         SigningAlg::Es384 => Some(Box::new(EcdsaValidator::Es384)),
         SigningAlg::Es512 => None, /* why is this unimplemented? */
-        SigningAlg::Ed25519 => Some(Box::new(Ed25519Validator {})),
         SigningAlg::Ps256 => Some(Box::new(RsaValidator::Ps256)),
         SigningAlg::Ps384 => Some(Box::new(RsaValidator::Ps384)),
         SigningAlg::Ps512 => Some(Box::new(RsaValidator::Ps512)),
+        _ => None,
     }
 }
 

internal/crypto/src/tests/raw_signature/mod.rs

@@ -13,5 +13,6 @@
 
 mod async_signers;
 mod async_validators;
+mod rust_native;
 mod signers;
 mod validators;

internal/crypto/src/tests/raw_signature/rust_native/mod.rs

@@ -0,0 +1,15 @@
+// Copyright 2025 Adobe. All rights reserved.
+// This file is licensed to you under the Apache License,
+// Version 2.0 (http://www.apache.org/licenses/LICENSE-2.0)
+// or the MIT license (http://opensource.org/licenses/MIT),
+// at your option.
+
+// Unless required by applicable law or agreed to in writing,
+// this software is distributed on an "AS IS" BASIS, WITHOUT
+// WARRANTIES OR REPRESENTATIONS OF ANY KIND, either express or
+// implied. See the LICENSE-MIT and LICENSE-APACHE files for the
+// specific language governing permissions and limitations under
+// each license.
+
+mod signers;
+mod validators;