pkey: have PKey.read parse PEM-encoded DHParameter

Try PEM_read_bio_Parameters(). Only PEM format is supported at the
moment since corresponding d2i_* functions are not provided by OpenSSL.

Author: rhenium

ext/openssl/ossl_pkey.c

@@ -178,6 +178,9 @@ ossl_pkey_new_from_data(int argc, VALUE *argv, VALUE self)
     OSSL_BIO_reset(bio);
     if ((pkey = PEM_read_bio_PUBKEY(bio, NULL, NULL, NULL)))
 	goto ok;
+    OSSL_BIO_reset(bio);
+    if ((pkey = PEM_read_bio_Parameters(bio, NULL)))
+	goto ok;
 
     BIO_free(bio);
     ossl_raise(ePKeyError, "Could not parse PKey");

test/openssl/test_pkey_dh.rb

@@ -36,6 +36,8 @@ def test_DHparams
     EOF
     key = OpenSSL::PKey::DH.new(pem)
     assert_same_dh dup_public(dh1024), key
+    key = OpenSSL::PKey.read(pem)
+    assert_same_dh dup_public(dh1024), key
 
     assert_equal asn1.to_der, dh1024.to_der
     assert_equal pem, dh1024.export

test/openssl/utils.rb

@@ -42,9 +42,6 @@ module Fixtures
 
     def pkey(name)
       OpenSSL::PKey.read(read_file("pkey", name))
-    rescue OpenSSL::PKey::PKeyError
-      # TODO: DH parameters can be read by OpenSSL::PKey.read atm
-      OpenSSL::PKey::DH.new(read_file("pkey", name))
     end
 
     def read_file(category, name)