[ruby/openssl] pkey: change PKey::{RSA,DSA,DH}#params to use nil for missing parameters

The returned Hash from these methods contain 0 in place of a missing
parameter in the key, for example:

	pkey = OpenSSL::PKey.read(OpenSSL::PKey::RSA.new(2048).public_to_pem)
	pp pkey.params
	#=>
	# {"n"=>#<OpenSSL::BN https://github.com/ruby/openssl/commit/286934673421[...snip]>,
	#  "e"=>#<OpenSSL::BN 65537>,
	#  "d"=>#<OpenSSL::BN 0>,
	#  "p"=>#<OpenSSL::BN 0>,
	#  "q"=>#<OpenSSL::BN 0>,
	#  "dmp1"=>#<OpenSSL::BN 0>,
	#  "dmq1"=>#<OpenSSL::BN 0>,
	#  "iqmp"=>#<OpenSSL::BN 0>}

Let's use nil instead, which is more appropriate for indicating a
missing value.

https://github.com/ruby/openssl/commit/f247ec3dec

ext/openssl/lib/openssl/pkey.rb

@@ -42,7 +42,7 @@ module OpenSSL::PKey
     # The hash has keys 'p', 'q', 'g', 'pub_key', and 'priv_key'.
     def params
       %w{p q g pub_key priv_key}.map { |name|
-        [name, send(name) || 0.to_bn]
+        [name, send(name)]
       }.to_h
     end
 
@@ -174,7 +174,7 @@ module OpenSSL::PKey
     # The hash has keys 'p', 'q', 'g', 'pub_key', and 'priv_key'.
     def params
       %w{p q g pub_key priv_key}.map { |name|
-        [name, send(name) || 0.to_bn]
+        [name, send(name)]
       }.to_h
     end
 
@@ -360,7 +360,7 @@ module OpenSSL::PKey
     # The hash has keys 'n', 'e', 'd', 'p', 'q', 'dmp1', 'dmq1', and 'iqmp'.
     def params
       %w{n e d p q dmp1 dmq1 iqmp}.map { |name|
-        [name, send(name) || 0.to_bn]
+        [name, send(name)]
       }.to_h
     end
 

test/openssl/test_pkey_dh.rb

@@ -137,9 +137,9 @@ class OpenSSL::TestPKeyDH < OpenSSL::PKeyTestCase
     assert_kind_of(OpenSSL::BN, dh.g)
     assert_equal(dh.g, dh.params["g"])
     assert_nil(dh.pub_key)
-    assert_equal(0, dh.params["pub_key"])
+    assert_nil(dh.params["pub_key"])
     assert_nil(dh.priv_key)
-    assert_equal(0, dh.params["priv_key"])
+    assert_nil(dh.params["priv_key"])
 
     dhkey = OpenSSL::PKey.generate_key(dh)
     assert_equal(dh.params["p"], dhkey.params["p"])

test/openssl/test_pkey_dsa.rb

@@ -248,7 +248,7 @@ fWLOqqkzFeRrYMDzUpl36XktY6Yq8EJYlW9pCMmBVNy/dQ==
     assert_equal(key.pub_key, pubkey.pub_key)
     assert_equal(key.pub_key, pubkey.params["pub_key"])
     assert_nil(pubkey.priv_key)
-    assert_equal(0, pubkey.params["priv_key"])
+    assert_nil(pubkey.params["priv_key"])
   end
 
   def test_dup

test/openssl/test_pkey_rsa.rb

@@ -595,7 +595,7 @@ class OpenSSL::TestPKeyRSA < OpenSSL::PKeyTestCase
     assert_equal(key.e, pubkey.e)
     [:d, :p, :q, :dmp1, :dmq1, :iqmp].each do |name|
       assert_nil(pubkey.send(name))
-      assert_equal(0, pubkey.params[name.to_s])
+      assert_nil(pubkey.params[name.to_s])
     end
   end