Added a little documentation and finetuning for cases where parameters cannot be fetched from the underlying library

Author: anakinj

ext/openssl/ossl_pkey.c

@@ -544,11 +544,18 @@ pkey_from_parameters(int argc, VALUE *argv, VALUE self)
 
     from_params_args.param_bld = OSSL_PARAM_BLD_new();
 
-    if (from_params_args.param_bld == NULL)
+    if (from_params_args.param_bld == NULL) {
+        EVP_PKEY_CTX_free(ctx);
         ossl_raise(ePKeyError, "OSSL_PARAM_BLD_new");
+    }
 
     from_params_args.settable_params = EVP_PKEY_fromdata_settable(ctx, EVP_PKEY_KEYPAIR);
 
+    if (from_params_args.settable_params == NULL) {
+        EVP_PKEY_CTX_free(ctx);
+        ossl_raise(ePKeyError, "EVP_PKEY_fromdata_settable");
+    }
+
     if (strcmp("RSA", algorithm) == 0) {
         from_params_args.aliases = rsa_aliases;
         from_params_args.nAliases = sizeof(rsa_aliases)/sizeof((rsa_aliases)[0]);
@@ -638,6 +645,22 @@ ossl_pkey_s_generate_key(int argc, VALUE *argv, VALUE self)
     return pkey_generate(argc, argv, self, 0);
 }
 
+/*
+ * call-seq:
+ *    OpenSSL::PKey.from_parameters(algo_name, parameters) -> pkey
+ *
+ * Generates a new key based on given key parameters.
+ *
+ * The first parameter is the type of the key to create, given as a String, for example RSA, DSA, EC etc.
+ * Second parameter is the parameters to be used for the key.
+ *
+ * For details algorithms and parameters see https://www.openssl.org/docs/man3.0/man3/EVP_PKEY_fromdata.html
+ *
+ * == Example
+ *   pkey = OpenSSL::PKey.from_parameters("RSA", n: 3161751493, e: 65537, d: 2064855961)
+ *   pkey.private? #=> true
+ *   pkey.public_key #=> #<OpenSSL::PKey::RSA...
+ */
 static VALUE
 ossl_pkey_s_from_parameters(int argc, VALUE *argv, VALUE self)
 {

test/openssl/test_pkey.rb

@@ -324,6 +324,11 @@ def test_s_from_parameters_ec_with_invalid_parameter
       assert_match(/Invalid parameter "invalid"/, e.message)
     end
 
+    def test_s_from_parameters_scrypt
+      e = assert_raise(OpenSSL::PKey::PKeyError) { OpenSSL::PKey.from_parameters("SCRYPT", {}) }
+      assert_match("EVP_PKEY_fromdata_settable", e.message)
+    end
+
     def test_s_from_parameters_dsa_with_all_supported_parameters
       source  = OpenSSL::PKey::DSA.generate(2048)