Add X509::get_ext

This function allows retrieving extensions from X509 certificates.

openssl/src/x509/mod.rs

@@ -425,6 +425,35 @@ impl X509Ref {
         }
     }
 
+    /// Returns this certificate's extensions for the given [Nid].
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use openssl::nid::Nid;
+    /// use openssl::x509::X509;
+    ///
+    /// let cert = X509::from_pem(include_bytes!("../../test/extensions.pem")).unwrap();
+    /// let nid = Nid::create(&"1.3.6.1.4.1.41482.5.3", &"fw", &"firmware").unwrap();
+    /// let extension = cert.get_ext(nid).unwrap().unwrap();
+    /// let value = extension.data().as_slice();
+    /// assert_eq!(value, [4, 3, 5, 2, 7]);
+    /// ```
+    #[corresponds(X509_get_ext_by_NID)]
+    pub fn get_ext(&self, nid: Nid) -> Result<Option<&X509ExtensionRef>, ErrorStack> {
+        unsafe {
+            let loc = ffi::X509_get_ext_by_NID(self.as_ptr(), nid.as_raw(), -1);
+            Ok(if loc >= 0 {
+                Some(X509ExtensionRef::from_ptr(cvt_p(ffi::X509_get_ext(
+                    self.as_ptr(),
+                    loc,
+                ))?))
+            } else {
+                None
+            })
+        }
+    }
+
     /// Returns this certificate's subject alternative name entries, if they exist.
     #[corresponds(X509_get_ext_d2i)]
     pub fn subject_alt_names(&self) -> Option<Stack<GeneralName>> {

openssl/test/extensions.pem

@@ -0,0 +1,20 @@
+-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----