From 0651f72569f9f207acfc66091a83922fd032be5f Mon Sep 17 00:00:00 2001
From: Daniel McCarney <daniel@binaryparadox.net>
Date: Thu, 7 Sep 2023 12:57:29 -0400
Subject: [PATCH] error: add is_fatal helper, use in verify_cert

This commit adds a method to `Error` for testing whether an error should
be considered fatal, e.g. should stop any further path building
progress. The existing consideration of fatal errors in
`loop_while_non_fatal_error` is updated to use the `is_fatal` fn.

Having this in a central place means we can avoid duplicating the match
arms in multiple places, where they are likely to fall out-of-sync.
---
 src/error.rs       | 14 ++++++++++++++
 src/verify_cert.rs |  6 +++---
 2 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/src/error.rs b/src/error.rs
index 2b7183a4..c450b89f 100644
--- a/src/error.rs
+++ b/src/error.rs
@@ -115,6 +115,20 @@ pub enum Error {
     UnsupportedSignatureAlgorithmForPublicKey,
 }
 
+impl Error {
+    /// Returns true for errors that should be considered fatal during path building. Errors of
+    /// this class should halt any further path building and be returned immediately.
+    #[inline]
+    pub(crate) fn is_fatal(&self) -> bool {
+        matches!(
+            self,
+            Error::MaximumSignatureChecksExceeded
+                | Error::MaximumPathBuildCallsExceeded
+                | Error::MaximumNameConstraintComparisonsExceeded
+        )
+    }
+}
+
 impl fmt::Display for Error {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         write!(f, "{:?}", self)
diff --git a/src/verify_cert.rs b/src/verify_cert.rs
index c77c8e5f..cc977cf1 100644
--- a/src/verify_cert.rs
+++ b/src/verify_cert.rs
@@ -464,9 +464,9 @@ where
         // If the error is not fatal, then keep going.
         match f(v) {
             Ok(()) => return Ok(()),
-            err @ Err(Error::MaximumSignatureChecksExceeded)
-            | err @ Err(Error::MaximumPathBuildCallsExceeded)
-            | err @ Err(Error::MaximumNameConstraintComparisonsExceeded) => return err,
+            // Fatal errors should halt further looping.
+            res @ Err(err) if err.is_fatal() => return res,
+            // Non-fatal errors should allow looping to continue.
             _ => {}
         }
     }