pkey: add OpenSSL::PKey::PKey#get_param

Expose EVP_PKEY_get_params(), added in OpenSSL 3.0, for retrieving
various parameters from an EVP_PKEY object.

Author: rhenium

ext/openssl/extconf.rb

@@ -161,6 +161,7 @@ def find_openssl_library
 have_func("BN_check_prime(NULL, NULL, NULL)", "openssl/bn.h")
 have_func("EVP_MD_CTX_get0_md(NULL)", evp_h)
 have_func("EVP_MD_CTX_get_pkey_ctx(NULL)", evp_h)
+have_func("EVP_PKEY_get_params(NULL, NULL)", evp_h)
 have_func("EVP_PKEY_eq(NULL, NULL)", evp_h)
 have_func("EVP_PKEY_dup(NULL)", evp_h)
 have_func("EVP_PKEY_encapsulate_init(NULL, NULL)", evp_h)

ext/openssl/ossl_pkey.c

@@ -771,6 +771,96 @@ ossl_pkey_inspect(VALUE self)
     return str;
 }
 
+#ifdef HAVE_EVP_PKEY_GET_PARAMS
+/*
+ * call-seq:
+ *    pkey.get_param(key) -> String or OpenSSL::BN
+ *
+ * Gets a parameter from the key. This is a low-level interface to OpenSSL's
+ * EVP_PKEY_get_params() function, available in OpenSSL 3.0 or later.
+ *
+ * Check the relevant EVP_PKEY-* man page, or the documentation for the OpenSSL
+ * provider in use, for the supported parameter keys and their return types.
+ *
+ * See the man page EVP_PKEY_get_params(3) for details.
+ */
+static VALUE
+ossl_pkey_get_param(VALUE self, VALUE keyv)
+{
+    EVP_PKEY *pkey;
+    const OSSL_PARAM *gettable_params, *p;
+    OSSL_PARAM params[] = {
+        { NULL, 0, NULL, 0, OSSL_PARAM_UNMODIFIED },
+        OSSL_PARAM_END,
+    };
+    VALUE ret, tmp = 0;
+
+    GetPKey(self, pkey);
+    gettable_params = EVP_PKEY_gettable_params(pkey);
+    if (!gettable_params)
+        ossl_raise(ePKeyError, "EVP_PKEY_gettable_params");
+    p = OSSL_PARAM_locate_const(gettable_params, StringValueCStr(keyv));
+    if (!p)
+        ossl_raise(ePKeyError, "unrecognized OSSL_PARAM key: %"PRIsVALUE, keyv);
+
+    params[0].key = p->key;
+    params[0].data_type = p->data_type;
+    if (!EVP_PKEY_get_params(pkey, params))
+        ossl_raise(ePKeyError, "EVP_PKEY_get_params");
+    if (!OSSL_PARAM_modified(&params[0]))
+        ossl_raise(ePKeyError, "OSSL_PARAM_modified");
+
+    switch (p->data_type) {
+      case OSSL_PARAM_INTEGER:
+      case OSSL_PARAM_UNSIGNED_INTEGER:
+        ret = ossl_bn_new(BN_value_one());
+        params[0].data_size =
+            params[0].return_size > 0 ? params[0].return_size : 1;
+        params[0].data = ALLOCV(tmp, params[0].data_size);
+        break;
+      case OSSL_PARAM_UTF8_STRING:
+      case OSSL_PARAM_OCTET_STRING:
+        ret = rb_str_new(NULL, params[0].return_size);
+        if (p->data_type == OSSL_PARAM_UTF8_STRING)
+            rb_enc_associate_index(ret, rb_utf8_encindex());
+        params[0].data_size = params[0].return_size;
+        params[0].data = RSTRING_PTR(ret);
+        break;
+      default:
+        /*
+         * As of OpenSSL 4.0, the following data types are defined, but are
+         * not actually used in EVP_PKEY_gettable_params(). So leave them
+         * unimplemented for now:
+         *   - OSSL_PARAM_REAL (double)
+         *   - OSSL_PARAM_UTF8_PTR (C string)
+         *   - OSSL_PARAM_OCTET_PTR (arbitrary pointer?)
+         */
+        ossl_raise(ePKeyError, "unsupported OSSL_PARAM data type %d for key %s",
+                   p->data_type, p->key);
+    }
+    if (!EVP_PKEY_get_params(pkey, params))
+        ossl_raise(ePKeyError, "EVP_PKEY_get_params");
+
+    switch (p->data_type) {
+      case OSSL_PARAM_INTEGER:
+      case OSSL_PARAM_UNSIGNED_INTEGER: {
+        BIGNUM *bn = GetBNPtr(ret);
+        if (!OSSL_PARAM_get_BN(&params[0], &bn))
+            ossl_raise(eOSSLError, "OSSL_PARAM_get_BN");
+        break;
+      }
+      case OSSL_PARAM_UTF8_STRING:
+      case OSSL_PARAM_OCTET_STRING:
+        rb_str_set_len(ret, params[0].return_size);
+        break;
+    }
+    ALLOCV_END(tmp);
+    return ret;
+}
+#else
+#define ossl_pkey_get_param rb_f_notimplement
+#endif
+
 /*
  * call-seq:
  *    pkey.to_text -> string
@@ -1868,6 +1958,7 @@ Init_ossl_pkey(void)
 #endif
     rb_define_method(cPKey, "oid", ossl_pkey_oid, 0);
     rb_define_method(cPKey, "inspect", ossl_pkey_inspect, 0);
+    rb_define_method(cPKey, "get_param", ossl_pkey_get_param, 1);
     rb_define_method(cPKey, "to_text", ossl_pkey_to_text, 0);
     rb_define_method(cPKey, "private_to_der", ossl_pkey_private_to_der, -1);
     rb_define_method(cPKey, "private_to_pem", ossl_pkey_private_to_pem, -1);

test/openssl/test_pkey.rb

@@ -182,6 +182,10 @@ def test_ed25519
     omit_on_fips
 
     # Test vector from RFC 8032 Section 7.1 TEST 2
+    secret_key = ["4ccd089b28ff96da9db6c346ec114e0f" \
+                  "5b8a319f35aba624da8cf6ed4fb8a6fb"].pack("H*")
+    public_key = ["3d4017c3e843895a92b70aa74d1b7ebc" \
+                  "9c982ccf2ec4968cc0cd55f12af4660c"].pack("H*")
     priv_pem = <<~EOF
     -----BEGIN PRIVATE KEY-----
     MC4CAQAwBQYDK2VwBCIEIEzNCJso/5banbbDRuwRTg9bijGfNaumJNqM9u1PuKb7
@@ -200,14 +204,14 @@ def test_ed25519
     assert_equal pub_pem, priv.public_to_pem
     assert_equal pub_pem, pub.public_to_pem
 
-    assert_equal "4ccd089b28ff96da9db6c346ec114e0f5b8a319f35aba624da8cf6ed4fb8a6fb",
-      priv.raw_private_key.unpack1("H*")
-    assert_equal OpenSSL::PKey.new_raw_private_key("ED25519", priv.raw_private_key).private_to_pem,
-      priv.private_to_pem
-    assert_equal "3d4017c3e843895a92b70aa74d1b7ebc9c982ccf2ec4968cc0cd55f12af4660c",
-      priv.raw_public_key.unpack1("H*")
-    assert_equal OpenSSL::PKey.new_raw_public_key("ED25519", priv.raw_public_key).public_to_pem,
-      pub.public_to_pem
+    assert_equal secret_key, priv.raw_private_key
+    assert_equal secret_key, priv.get_param("priv") if openssl?(3, 0, 0)
+    assert_equal priv.private_to_pem,
+      OpenSSL::PKey.new_raw_private_key("ED25519", secret_key).private_to_pem
+    assert_equal public_key, priv.raw_public_key
+    assert_equal public_key, priv.get_param("pub") if openssl?(3, 0, 0)
+    assert_equal pub.public_to_pem,
+      OpenSSL::PKey.new_raw_public_key("ED25519", public_key).public_to_pem
 
     sig = [<<~EOF.gsub(/[^0-9a-f]/, "")].pack("H*")
     92a009a9f0d4cab8720e820b5f642540
@@ -272,6 +276,7 @@ def test_ml_dsa
 
     pkey = OpenSSL::PKey.generate_key("ML-DSA-44")
     assert_match(/type_name=ML-DSA-44/, pkey.inspect)
+    assert_equal(32, pkey.get_param("seed").bytesize)
     sig = pkey.sign(nil, "data")
     assert_equal(2420, sig.bytesize)
     assert_equal(true, pkey.verify(nil, sig, "data"))

test/openssl/test_pkey_ec.rb

@@ -80,6 +80,17 @@ def test_marshal
     assert_equal key.to_der, deserialized.to_der
   end
 
+  def test_get_param
+    unless openssl?(3, 0, 0) || OpenSSL::PKey::PKey.method_defined?(:get_param)
+      omit "EVP_PKEY_get_params() is not supported"
+    end
+    key = Fixtures.pkey("p256")
+    assert_equal("prime256v1", key.get_param("group"))
+    assert_equal(Encoding::UTF_8, key.get_param("group").encoding)
+    assert_equal(key.group.order, key.get_param("order"))
+    assert_kind_of(OpenSSL::BN, key.get_param("order"))
+  end
+
   def test_check_key
     omit_on_fips
 

test/openssl/test_pkey_rsa.rb

@@ -532,6 +532,22 @@ def test_params
     end
   end
 
+  def test_get_param
+    unless openssl?(3, 0, 0) || OpenSSL::PKey::PKey.method_defined?(:get_param)
+      omit "EVP_PKEY_get_params() is not supported"
+    end
+    key = Fixtures.pkey("rsa2048")
+    assert_kind_of(OpenSSL::BN, key.get_param("n"))
+    assert_equal(key.n, key.get_param("n"))
+    assert_equal(key.e, key.get_param("e"))
+    assert_equal(key.d, key.get_param("d"))
+    assert_equal(key.p, key.get_param("rsa-factor1"))
+    assert_equal(key.q, key.get_param("rsa-factor2"))
+    assert_equal(key.dmp1, key.get_param("rsa-exponent1"))
+    assert_equal(key.dmq1, key.get_param("rsa-exponent2"))
+    assert_equal(key.iqmp, key.get_param("rsa-coefficient1"))
+  end
+
   def test_dup
     key = Fixtures.pkey("rsa-1")
     key2 = key.dup