fix: better error for setting bad quic policy

docs/usage-guide/topics/ch06-security-policies.md

@@ -51,6 +51,8 @@ In contrast, numbered or dated versions are fixed and will never change. The num
 * "default_tls13": "20240503"
 For previous defaults, see the "Default Policy History" section below.
 
+"default_fips" does not currently support TLS1.3. If you need a policy that supports both FIPS and TLS1.3, choose "20230317". We plan to add TLS1.3 support to both "default" and "default_fips" in the future.
+
 "rfc9151" is derived from [Commercial National Security Algorithm (CNSA) Suite Profile for TLS and DTLS 1.2 and 1.3](https://datatracker.ietf.org/doc/html/rfc9151). This policy restricts the algorithms allowed for signatures on certificates in the certificate chain to RSA or ECDSA with sha384, which may require you to update your certificates.
 Like the default policies, this policy may also change if the source RFC definition changes.
 

tests/unit/s2n_quic_support_test.c

@@ -300,5 +300,30 @@ int main(int argc, char **argv)
         EXPECT_SUCCESS(s2n_config_free(config));
     };
 
+    /* Test: setting policies without TLS1.3 is not allowed when quic is enabled */
+    {
+        /* On config */
+        {
+            DEFER_CLEANUP(struct s2n_config *config = s2n_config_new(),
+                    s2n_config_ptr_free);
+            EXPECT_SUCCESS(s2n_config_enable_quic(config));
+            EXPECT_FAILURE_WITH_ERRNO(
+                    s2n_config_set_cipher_preferences(config, "test_all_tls12"),
+                    S2N_ERR_UNSUPPORTED_WITH_QUIC);
+            EXPECT_SUCCESS(s2n_config_set_cipher_preferences(config, "test_all_tls13"));
+        };
+
+        /* On connection */
+        {
+            DEFER_CLEANUP(struct s2n_connection *conn = s2n_connection_new(S2N_SERVER),
+                    s2n_connection_ptr_free);
+            EXPECT_SUCCESS(s2n_connection_enable_quic(conn));
+            EXPECT_FAILURE_WITH_ERRNO(
+                    s2n_connection_set_cipher_preferences(conn, "test_all_tls12"),
+                    S2N_ERR_UNSUPPORTED_WITH_QUIC);
+            EXPECT_SUCCESS(s2n_connection_set_cipher_preferences(conn, "test_all_tls13"));
+        };
+    };
+
     END_TEST();
 }

tls/s2n_security_policies.c

@@ -1268,6 +1268,11 @@ int s2n_config_set_cipher_preferences(struct s2n_config *config, const char *ver
     /* If the security policy's minimum version is higher than what libcrypto supports, return an error. */
     POSIX_ENSURE((security_policy->minimum_protocol_version <= s2n_get_highest_fully_supported_tls_version()), S2N_ERR_PROTOCOL_VERSION_UNSUPPORTED);
 
+    /* If the security policy isn't compatible with quic settings, return an error */
+    if (config->quic_enabled) {
+        POSIX_ENSURE(s2n_security_policy_supports_tls13(security_policy), S2N_ERR_UNSUPPORTED_WITH_QUIC);
+    }
+
     config->security_policy = security_policy;
     return 0;
 }
@@ -1290,6 +1295,11 @@ int s2n_connection_set_cipher_preferences(struct s2n_connection *conn, const cha
      * policy's certificate preferences, return an error. */
     POSIX_GUARD_RESULT(s2n_config_validate_loaded_certificates(conn->config, security_policy));
 
+    /* If the security policy isn't compatible with quic settings, return an error */
+    if (s2n_connection_is_quic_enabled(conn)) {
+        POSIX_ENSURE(s2n_security_policy_supports_tls13(security_policy), S2N_ERR_UNSUPPORTED_WITH_QUIC);
+    }
+
     conn->security_policy_override = security_policy;
     return 0;
 }