Fix KeyUsage/KeyUsages (#30)

I misread and/or misinterpreted information from RFC5280, describing the KeyUsage extension. This PR properly implements the KeyUsage extension as intended in RFC5280 (closes #28), closes #29, re-exports `der` and `spki` and makes errors a little nicer.

examples/ed25519_cert.rs

@@ -56,9 +56,7 @@ fn main() {
         &Capabilities::default_actor(),
     )
     .unwrap();
-
     let data = csr.clone().to_der().unwrap();
-    dbg!(&data);
     let file_name_with_extension = "cert.csr";
     #[cfg(not(target_arch = "wasm32"))]
     std::fs::write(file_name_with_extension, &data).unwrap();

examples/ed25519_from_der.rs

@@ -0,0 +1,229 @@
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+#![allow(unused)]
+
+use std::str::FromStr;
+use std::time::Duration;
+
+use der::asn1::{BitString, Ia5String, Uint, UtcTime};
+use der::{Decode, Encode};
+use ed25519_dalek::{Signature as Ed25519DalekSignature, Signer, SigningKey, VerifyingKey};
+use polyproto::certs::capabilities::Capabilities;
+use polyproto::certs::idcert::IdCert;
+use polyproto::certs::PublicKeyInfo;
+use polyproto::key::{PrivateKey, PublicKey};
+use polyproto::signature::Signature;
+use rand::rngs::OsRng;
+use spki::{AlgorithmIdentifierOwned, ObjectIdentifier, SignatureBitStringEncoding};
+use thiserror::Error;
+use x509_cert::attr::Attributes;
+use x509_cert::name::RdnSequence;
+use x509_cert::request::CertReq;
+use x509_cert::time::{Time, Validity};
+use x509_cert::Certificate;
+
+/// The following example uses the same setup as in ed25519_basic.rs, but in its main method, it
+/// creates a certificate signing request (CSR) and writes it to a file. The CSR is created from a
+/// polyproto ID CSR, which is a wrapper around a PKCS #10 CSR.
+///
+/// If you have openssl installed, you can inspect the CSR by running:
+///
+/// ```sh
+/// openssl req -in cert.csr -verify -inform der
+/// ```
+///
+/// After that, the program creates an ID-Cert from the given ID-CSR. The `cert.der` file can also
+/// be validated using openssl:
+///
+/// ```sh
+/// openssl x509 -in cert.der -text -noout -inform der
+/// ```
+
+#[cfg_attr(target_arch = "wasm32", wasm_bindgen_test::wasm_bindgen_test)]
+#[cfg_attr(not(target_arch = "wasm32"), test)]
+fn main() {
+    let mut csprng = rand::rngs::OsRng;
+    let priv_key = Ed25519PrivateKey::gen_keypair(&mut csprng);
+    println!("Private Key is: {:?}", priv_key.key.to_bytes());
+    println!("Public Key is: {:?}", priv_key.public_key.key.to_bytes());
+    println!();
+
+    let csr = polyproto::certs::idcsr::IdCsr::new(
+        &RdnSequence::from_str("CN=flori,DC=www,DC=polyphony,DC=chat,UID=flori@polyphony.chat,uniqueIdentifier=client1").unwrap(),
+        &priv_key,
+        &Capabilities::default_actor(),
+    )
+    .unwrap();
+
+    let data = csr.clone().to_der().unwrap();
+    let file_name_with_extension = "cert.csr";
+    #[cfg(not(target_arch = "wasm32"))]
+    std::fs::write(file_name_with_extension, &data).unwrap();
+
+    let cert = IdCert::from_actor_csr(
+        csr,
+        &priv_key,
+        Uint::new(&8932489u64.to_be_bytes()).unwrap(),
+        RdnSequence::from_str(
+            "CN=root,DC=www,DC=polyphony,DC=chat,UID=root@polyphony.chat,uniqueIdentifier=root",
+        )
+        .unwrap(),
+        Validity {
+            not_before: Time::UtcTime(
+                UtcTime::from_unix_duration(Duration::from_secs(10)).unwrap(),
+            ),
+            not_after: Time::UtcTime(
+                UtcTime::from_unix_duration(Duration::from_secs(1000)).unwrap(),
+            ),
+        },
+    )
+    .unwrap();
+    let data = cert.clone().to_der().unwrap();
+    let cert_from_der = IdCert::from_der(data).unwrap();
+    assert_eq!(cert_from_der, cert)
+}
+
+#[cfg(not(target_arch = "wasm32"))]
+#[cfg(not(test))]
+fn main() {}
+
+// As mentioned in the README, we start by implementing the signature trait.
+
+// Here, we start by defining the signature type, which is a wrapper around the signature type from
+// the ed25519-dalek crate.
+#[derive(Debug, PartialEq, Eq, Clone)]
+struct Ed25519Signature {
+    signature: Ed25519DalekSignature,
+    algorithm: AlgorithmIdentifierOwned,
+}
+
+// We implement the Signature trait for our signature type.
+impl Signature for Ed25519Signature {
+    // We define the signature type from the ed25519-dalek crate as the associated type.
+    type Signature = Ed25519DalekSignature;
+
+    // This is straightforward: we return a reference to the signature.
+    fn as_signature(&self) -> &Self::Signature {
+        &self.signature
+    }
+
+    // The algorithm identifier for a given signature implementation is constant. We just need
+    // to define it here.
+    fn algorithm_identifier() -> AlgorithmIdentifierOwned {
+        AlgorithmIdentifierOwned {
+            // This is the OID for Ed25519. It is defined in the IANA registry.
+            oid: ObjectIdentifier::from_str("1.3.101.112").unwrap(),
+            // For this example, we don't need or want any parameters.
+            parameters: None,
+        }
+    }
+
+    fn from_bitstring(signature: &[u8]) -> Self {
+        let mut signature_vec = signature.to_vec();
+        signature_vec.resize(64, 0);
+        let signature_array: [u8; 64] = {
+            let mut array = [0; 64];
+            array.copy_from_slice(&signature_vec[..]);
+            array
+        };
+        Self {
+            signature: Ed25519DalekSignature::from_bytes(&signature_array),
+            algorithm: Self::algorithm_identifier(),
+        }
+    }
+}
+
+// The `SignatureBitStringEncoding` trait is used to convert a signature to a bit string. We implement
+// it for our signature type.
+impl SignatureBitStringEncoding for Ed25519Signature {
+    fn to_bitstring(&self) -> der::Result<der::asn1::BitString> {
+        BitString::from_bytes(&self.as_signature().to_bytes())
+    }
+}
+
+// Next, we implement the key traits. We start by defining the private key type.
+#[derive(Debug, Clone, PartialEq, Eq)]
+struct Ed25519PrivateKey {
+    // Defined below
+    public_key: Ed25519PublicKey,
+    // The private key from the ed25519-dalek crate
+    key: SigningKey,
+}
+
+impl PrivateKey<Ed25519Signature> for Ed25519PrivateKey {
+    type PublicKey = Ed25519PublicKey;
+
+    // Return a reference to the public key
+    fn pubkey(&self) -> &Self::PublicKey {
+        &self.public_key
+    }
+
+    // Signs a message. The beauty of having to wrap the ed25519-dalek crate is that we can
+    // harness all of its functionality, such as the `sign` method.
+    fn sign(&self, data: &[u8]) -> Ed25519Signature {
+        let signature = self.key.sign(data);
+        Ed25519Signature {
+            signature,
+            algorithm: self.algorithm_identifier(),
+        }
+    }
+}
+
+impl Ed25519PrivateKey {
+    // Let's also define a handy method to generate a key pair.
+    pub fn gen_keypair(csprng: &mut OsRng) -> Self {
+        let key = SigningKey::generate(csprng);
+        let public_key = Ed25519PublicKey {
+            key: key.verifying_key(),
+        };
+        Self { public_key, key }
+    }
+}
+
+// Same thing as above for the public key type.
+#[derive(Debug, Clone, PartialEq, Eq)]
+struct Ed25519PublicKey {
+    // The public key type from the ed25519-dalek crate
+    key: VerifyingKey,
+}
+
+impl PublicKey<Ed25519Signature> for Ed25519PublicKey {
+    // Verifies a signature. We use the `verify_strict` method from the ed25519-dalek crate.
+    // This method is used to mitigate weak key forgery.
+    fn verify_signature(
+        &self,
+        signature: &Ed25519Signature,
+        data: &[u8],
+    ) -> Result<(), polyproto::errors::composite::PublicKeyError> {
+        match self.key.verify_strict(data, signature.as_signature()) {
+            Ok(_) => Ok(()),
+            Err(_) => Err(polyproto::errors::composite::PublicKeyError::BadSignature),
+        }
+    }
+
+    // Returns the public key info. Public key info is used to encode the public key in a
+    // certificate or a CSR. It is named after the `SubjectPublicKeyInfo` type from the X.509
+    // standard, and thus includes the information needed to encode the public key in a certificate
+    // or a CSR.
+    fn public_key_info(&self) -> PublicKeyInfo {
+        PublicKeyInfo {
+            algorithm: Ed25519Signature::algorithm_identifier(),
+            public_key_bitstring: BitString::from_bytes(&self.key.to_bytes()).unwrap(),
+        }
+    }
+
+    fn from_public_key_info(public_key_info: PublicKeyInfo) -> Self {
+        let mut key_vec = public_key_info.public_key_bitstring.raw_bytes().to_vec();
+        key_vec.resize(32, 0);
+        let signature_array: [u8; 32] = {
+            let mut array = [0; 32];
+            array.copy_from_slice(&key_vec[..]);
+            array
+        };
+        Self {
+            key: VerifyingKey::from_bytes(&signature_array).unwrap(),
+        }
+    }
+}