Make SigningKey::from use Self::new() (#498)

This matches #472.

Author: marshallpierce

src/pkcs1v15/signing_key.rs

@@ -197,10 +197,10 @@ where
 
 impl<D> From<RsaPrivateKey> for SigningKey<D>
 where
-    D: Digest,
+    D: Digest + AssociatedOid,
 {
     fn from(key: RsaPrivateKey) -> Self {
-        Self::new_unprefixed(key)
+        Self::new(key)
     }
 }
 

tests/pkcs1v15.rs

@@ -21,3 +21,60 @@ fn signature_stringify() {
     assert_eq!(format!("{:X}", signature), expected);
     assert_eq!(signature.to_string(), expected);
 }
+
+#[cfg(feature = "pem")]
+#[test]
+fn signing_key_new_same_as_from() {
+    use pkcs1::DecodeRsaPrivateKey;
+    use rsa::RsaPrivateKey;
+    use signature::{Keypair, Signer, Verifier};
+
+    // randomly generated key, hardcoded for test repeatability
+    const PRIV_KEY_PKCS1_PEM: &str = "-----BEGIN RSA PRIVATE KEY-----
+MIIEowIBAAKCAQEAwQe5brkkpxrwR/5TJ6JXsUyBzYtbEL/w8u8P6NnxQ8sL4KYp
+MzzTB6aq1gq7bieYXChg0PIWeTukGaOzZe96KxhT0GbhhYRlukktM/quRrM7nYdm
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+Rmb665iB5fwpqmbE/hYKIn7asYQE+V0dkgt8M3qvlJJ5JJbCrJx3
+-----END RSA PRIVATE KEY-----";
+
+    let priv_key = RsaPrivateKey::from_pkcs1_pem(PRIV_KEY_PKCS1_PEM).unwrap();
+
+    let msg = b"1234";
+
+    let key_via_new = rsa::pkcs1v15::SigningKey::<sha2::Sha256>::new(priv_key.clone());
+    let key_via_from = rsa::pkcs1v15::SigningKey::<sha2::Sha256>::from(priv_key.clone());
+    let sig_via_new = key_via_new.sign(msg);
+    let sig_via_from = key_via_from.sign(msg);
+    assert_eq!(sig_via_new, sig_via_from);
+
+    // each verifies the other
+    assert!(key_via_new
+        .verifying_key()
+        .verify(msg, &sig_via_from)
+        .is_ok());
+    assert!(key_via_from
+        .verifying_key()
+        .verify(msg, &sig_via_new)
+        .is_ok());
+}