From 20bafea414bcc08bfcb5b669ecbf9a3438ff7b78 Mon Sep 17 00:00:00 2001
From: Alex Gaynor <alex.gaynor@gmail.com>
Date: Thu, 3 Mar 2022 15:44:02 -0500
Subject: [PATCH 3/5] fixes #6927 -- handle negative return values from openssl
 (#6928)

---
 src/cryptography/hazmat/backends/openssl/rsa.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/cryptography/hazmat/backends/openssl/rsa.py b/src/cryptography/hazmat/backends/openssl/rsa.py
index 9bef49d24..dd5d4990b 100644
--- a/src/cryptography/hazmat/backends/openssl/rsa.py
+++ b/src/cryptography/hazmat/backends/openssl/rsa.py
@@ -208,7 +208,7 @@ def _rsa_sig_setup(backend, padding, algorithm, key, init_func):
     if algorithm is not None:
         evp_md = backend._evp_md_non_null_from_algorithm(algorithm)
         res = backend._lib.EVP_PKEY_CTX_set_signature_md(pkey_ctx, evp_md)
-        if res == 0:
+        if res <= 0:
             backend._consume_errors()
             raise UnsupportedAlgorithm(
                 "{} is not supported by this backend for RSA signing.".format(
-- 
2.35.1