validation: use an extension trait

Signed-off-by: William Woodruff <[email protected]>

src/rust/cryptography-x509-validation/src/certificate.rs

@@ -0,0 +1,22 @@
+// This file is dual licensed under the terms of the Apache License, Version
+// 2.0, and the BSD License. See the LICENSE file in the root of this repository
+// for complete details.
+
+/// Extensional traits and functionality for certificates.
+use cryptography_x509::{certificate::Certificate, extensions::Extensions};
+
+pub(crate) trait CertificateExt: private::Sealed {
+    fn extensions<'a>(&'a self) -> Result<Option<Extensions<'a>>, asn1::ObjectIdentifier>;
+}
+
+impl CertificateExt for Certificate<'_> {
+    fn extensions<'a>(&'a self) -> Result<Option<Extensions<'a>>, asn1::ObjectIdentifier> {
+        self.tbs_cert.extensions()
+    }
+}
+
+mod private {
+    pub(crate) trait Sealed {}
+
+    impl Sealed for cryptography_x509::certificate::Certificate<'_> {}
+}

src/rust/cryptography-x509-validation/src/lib.rs

@@ -4,6 +4,7 @@
 
 #![forbid(unsafe_code)]
 
+pub mod certificate;
 pub mod extensions;
 pub mod policy;
 pub mod trust_store;