jwt/OsslJWS: basic JWS definitions for OpenSSL

src/jwt/OsslJWS.cxx

@@ -0,0 +1,27 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright CM4all GmbH
+// author: Max Kellermann <[email protected]>
+
+#include "OsslJWS.hxx"
+
+#include <openssl/evp.h>
+
+#include <stdexcept>
+
+using std::string_view_literals::operator""sv;
+
+namespace JWS {
+
+std::string_view
+GetAlg(const EVP_PKEY &key)
+{
+	switch (EVP_PKEY_get_base_id(&key)) {
+	case EVP_PKEY_RSA:
+		return "RS256"sv;
+
+	default:
+		throw std::invalid_argument{"Unsupported key type"};
+	}
+}
+
+} // namespace JWS

src/jwt/OsslJWS.hxx

@@ -0,0 +1,24 @@
+// SPDX-License-Identifier: BSD-2-Clause
+// Copyright CM4all GmbH
+// author: Max Kellermann <[email protected]>
+
+#pragma once
+
+#include <openssl/ossl_typ.h>
+
+#include <string_view>
+
+namespace JWS {
+
+/**
+ * Returns the "alg" (Algorithm) Header Parameter Values for JWS for
+ * the specified key.  The digest algorithm is assumed to be SHA2-256.
+ *
+ * Throws on error.
+ *
+ * @see RFC 7518 section 3.1
+ */
+std::string_view
+GetAlg(const EVP_PKEY &key);
+
+} // namespace JWS

src/jwt/meson.build

@@ -8,6 +8,7 @@ jwt = static_library(
   'RS256.cxx',
   'EdDSA.cxx',
   'OsslJWK.cxx',
+  'OsslJWS.cxx',
   include_directories: inc,
   dependencies: [
     crypto_dep,