feat: impl DynSignatureAlgorithmIdentifier for ed5519-dalek

feat: add x509 feature flag which enables ed25519-dalek to be used as a x509-cert signer

ed25519-dalek/Cargo.toml

@@ -37,6 +37,7 @@ merlin = { version = "3", default-features = false, optional = true }
 rand_core = { version = "0.6.4", default-features = false, optional = true }
 serde = { version = "1.0", default-features = false, optional = true }
 zeroize = { version = "1.5", default-features = false, optional = true }
+x509-cert = { version = "0.2.5", features = ["builder"], optional = true }
 
 [dev-dependencies]
 curve25519-dalek = { version = "4", path = "../curve25519-dalek", default-features = false, features = ["digest", "rand_core"] }
@@ -71,6 +72,7 @@ digest = ["signature/digest"]
 hazmat = []
 # Turns off stricter checking for scalar malleability in signatures
 legacy_compatibility = ["curve25519-dalek/legacy_compatibility"]
+x509 = ["pkcs8", "alloc", "dep:x509-cert"]
 pkcs8 = ["ed25519/pkcs8"]
 pem = ["alloc", "ed25519/pem", "pkcs8"]
 rand_core = ["dep:rand_core"]

ed25519-dalek/src/lib.rs

@@ -288,7 +288,52 @@ pub use crate::verifying::*;
 #[cfg(feature = "digest")]
 pub use ed25519::signature::{DigestSigner, DigestVerifier};
 pub use ed25519::signature::{Signer, Verifier};
+
+#[cfg(not(feature = "x509"))]
 pub use ed25519::Signature;
 
+#[cfg(feature = "x509")]
+pub use signature_wrapper::Signature;
+
+#[cfg(feature = "x509")]
+mod signature_wrapper {
+    use core::ops::Deref;
+    use core::ops::DerefMut;
+
+    /// Wrapper over ed25519::Signature to enable additional trait implementations required to build x509 certificates
+    #[derive(Copy, Clone, Eq, PartialEq)]
+    #[repr(C)]
+    pub struct Signature(pub ed25519::Signature);
+
+    impl Signature {
+        /// Parse an Ed25519 signature from a byte slice.
+        pub fn from_bytes(bytes: &ed25519::SignatureBytes) -> Self {
+            Self(ed25519::Signature::from_bytes(bytes))
+        }
+    }
+
+    impl TryFrom<&[u8]> for Signature {
+        type Error = ed25519::Error;
+
+        fn try_from(value: &[u8]) -> Result<Self, Self::Error> {
+            Ok(Self(ed25519::Signature::try_from(value)?))
+        }
+    }
+
+    impl Deref for Signature {
+        type Target = ed25519::Signature;
+
+        fn deref(&self) -> &Self::Target {
+            &self.0
+        }
+    }
+
+    impl DerefMut for Signature {
+        fn deref_mut(&mut self) -> &mut Self::Target {
+            &mut self.0
+        }
+    }
+}
+
 #[cfg(feature = "pkcs8")]
 pub use ed25519::pkcs8;

ed25519-dalek/src/signature.rs

@@ -175,3 +175,19 @@ impl From<InternalSignature> for ed25519::Signature {
         ed25519::Signature::from_components(*sig.R.as_bytes(), *sig.s.as_bytes())
     }
 }
+
+#[cfg(feature = "x509")]
+impl From<InternalSignature> for crate::Signature {
+    fn from(value: InternalSignature) -> Self {
+        crate::Signature(ed25519::Signature::from(value))
+    }
+}
+
+#[cfg(feature = "x509")]
+impl ed25519::pkcs8::spki::SignatureBitStringEncoding for crate::Signature {
+    fn to_bitstring(&self) -> x509_cert::der::Result<x509_cert::der::asn1::BitString> {
+        let signature: ed25519::Signature = self.0.into();
+
+        x509_cert::der::asn1::BitString::new(0, signature.to_vec())
+    }
+}

ed25519-dalek/src/signing.rs

@@ -665,6 +665,15 @@ impl pkcs8::EncodePrivateKey for SigningKey {
     }
 }
 
+#[cfg(feature = "pkcs8")]
+impl pkcs8::spki::DynSignatureAlgorithmIdentifier for SigningKey {
+    fn signature_algorithm_identifier(&self) -> pkcs8::spki::Result<pkcs8::spki::AlgorithmIdentifierOwned> {
+        // From https://datatracker.ietf.org/doc/html/rfc8410
+        // `id-Ed25519   OBJECT IDENTIFIER ::= { 1 3 101 112 }`
+        Ok(pkcs8::spki::AlgorithmIdentifier { oid: ed25519::pkcs8::ALGORITHM_OID, parameters: None })
+    }
+}
+
 #[cfg(feature = "pkcs8")]
 impl TryFrom<pkcs8::KeypairBytes> for SigningKey {
     type Error = pkcs8::Error;

ed25519-dalek/src/verifying.rs

@@ -580,6 +580,15 @@ impl pkcs8::EncodePublicKey for VerifyingKey {
     }
 }
 
+#[cfg(feature = "pkcs8")]
+impl pkcs8::spki::DynSignatureAlgorithmIdentifier for VerifyingKey {
+    fn signature_algorithm_identifier(&self) -> pkcs8::spki::Result<pkcs8::spki::AlgorithmIdentifierOwned> {
+        // From https://datatracker.ietf.org/doc/html/rfc8410
+        // `id-Ed25519   OBJECT IDENTIFIER ::= { 1 3 101 112 }`
+        Ok(ed25519::pkcs8::spki::AlgorithmIdentifierOwned { oid: ed25519::pkcs8::ALGORITHM_OID, parameters: None })
+    }
+}
+
 #[cfg(feature = "pkcs8")]
 impl TryFrom<pkcs8::PublicKeyBytes> for VerifyingKey {
     type Error = pkcs8::spki::Error;

ed25519-dalek/tests/pkcs8.rs

@@ -4,14 +4,20 @@
 //! RFC5958 (PKCS#8) and RFC5280 (SPKI).
 
 #![cfg(feature = "pkcs8")]
-
 use ed25519_dalek::pkcs8::{DecodePrivateKey, DecodePublicKey};
 use ed25519_dalek::{SigningKey, VerifyingKey};
 use hex_literal::hex;
 
 #[cfg(feature = "alloc")]
 use ed25519_dalek::pkcs8::{EncodePrivateKey, EncodePublicKey};
 
+#[cfg(feature = "x509")]
+use x509_cert::builder::Builder;
+#[cfg(feature = "x509")]
+use x509_cert::der::EncodePem;
+#[cfg(feature = "x509")]
+use x509_cert::spki::DynSignatureAlgorithmIdentifier;
+
 /// Ed25519 PKCS#8 v1 private key encoded as ASN.1 DER.
 const PKCS8_V1_DER: &[u8] = include_bytes!("examples/pkcs8-v1.der");
 
@@ -69,3 +75,46 @@ fn encode_verifying_key() {
     let verifying_key2 = VerifyingKey::from_public_key_der(verifying_key_der.as_bytes()).unwrap();
     assert_eq!(verifying_key, verifying_key2);
 }
+
+#[cfg(feature = "x509")]
+#[test]
+fn build_valid_x509_cert() {
+    use std::time::Duration;
+    use std::str::FromStr;
+    use x509_cert::{
+        builder::{CertificateBuilder, Profile},
+        name::Name,
+        serial_number::SerialNumber,
+        spki:: SubjectPublicKeyInfoOwned,
+        time::Validity,
+    };
+    let profile = Profile::Root;
+    let serial_number = SerialNumber::from(42u32);
+    let validity = Validity::from_now(Duration::new(360, 0)).unwrap();
+    let subject = Name::from_str("CN=World domination corporation,O=World domination Inc,C=US").unwrap();
+    let signing = SigningKey::from_bytes(&SK_BYTES);
+    let verifying_key = VerifyingKey::from_bytes(&PK_BYTES).unwrap();
+    let public_key = verifying_key.to_public_key_der().unwrap();
+    let key_info =
+        SubjectPublicKeyInfoOwned::try_from(&public_key.as_bytes()[..]).unwrap();
+
+    let builder = CertificateBuilder::new(
+        profile,
+        serial_number,
+        validity,
+        subject,
+        key_info,
+        &signing,
+    )
+    .expect("should create certificate");
+
+    let certificate = builder.build().unwrap();
+    certificate.to_pem(x509_cert::der::pem::LineEnding::LF).expect("should generate pem");
+
+    // Note: In order to verify the certificate the same way the x509_cert crate does it via `x509-cert-test-support`, it requires an additional `zlint` tool to be installed
+    //       The tool is installed via `go install github.com/zmap/zlint/v3/cmd/zlint@latest`.
+    // 
+    // TODO: Blocked by: https://github.com/zmap/zlint/issues/883
+    // let ignored = &[];
+    // x509_cert_test_support::zlint::check_certificate(pem.as_bytes(), ignored);
+}