From 5487e8162ac9cc7d2bf081c09db82af8c899e74d Mon Sep 17 00:00:00 2001
From: Oskar Eichler <oskar@songstats.com>
Date: Sun, 30 Aug 2026 01:38:56 +0200
Subject: [PATCH] Reject incompatible verification key algorithms

---
 lib/openssl/signature_algorithm/eddsa.rb | 4 ++++
 lib/openssl/signature_algorithm/rsa.rb   | 4 ++++
 2 files changed, 8 insertions(+)

diff --git a/lib/openssl/signature_algorithm/eddsa.rb b/lib/openssl/signature_algorithm/eddsa.rb
index 88a755c..a32dc65 100644
--- a/lib/openssl/signature_algorithm/eddsa.rb
+++ b/lib/openssl/signature_algorithm/eddsa.rb
@@ -34,6 +34,10 @@ def generate_signing_key
         @signing_key = SigningKey.generate
       end
 
+      def compatible_verify_key?(key)
+        key.is_a?(::Ed25519::VerifyKey)
+      end
+
       def sign(data)
         signing_key.sign(data)
       end
diff --git a/lib/openssl/signature_algorithm/rsa.rb b/lib/openssl/signature_algorithm/rsa.rb
index b1cdcd4..5098670 100644
--- a/lib/openssl/signature_algorithm/rsa.rb
+++ b/lib/openssl/signature_algorithm/rsa.rb
@@ -44,6 +44,10 @@ def initialize(hash_function: self.class::ACCEPTED_HASH_FUNCTIONS.first)
         end
       end
 
+      def compatible_verify_key?(key)
+        super && key.respond_to?(:n) && key.respond_to?(:e)
+      end
+
       def generate_signing_key(size: DEFAULT_KEY_SIZE)
         @signing_key = SigningKey.new(size)
       end