pkcs12: add PKCS12#set_mac

Add a binding for PKCS12_set_mac() to set MAC parameters and
(re-)calculate MAC for the content.

This allows generating PKCS #12 with consistent MAC parameters with
different OpenSSL versions. OpenSSL 3.0 changed the default hash
function used for HMAC and the KDF from SHA-1 to SHA-256.

Fixes: #772

ext/openssl/ossl_pkcs12.c

@@ -251,6 +251,48 @@ ossl_pkcs12_to_der(VALUE self)
     return str;
 }
 
+/*
+ * call-seq:
+ *    pkcs12.set_mac(pass, salt = nil, iter = nil, md_type = nil)
+ *
+ * Sets MAC parameters and generates MAC over the PKCS #12 structure.
+ *
+ * This method uses HMAC and the PKCS #12 specific password-based KDF as
+ * specified in the original PKCS #12.
+ *
+ * See also the man page PKCS12_set_mac(3).
+ *
+ * Added in version 3.3.0.
+ */
+static VALUE
+pkcs12_set_mac(int argc, VALUE *argv, VALUE self)
+{
+    PKCS12 *p12;
+    VALUE pass, salt, iter, md_name;
+    int iter_i = 0;
+    const EVP_MD *md_type = NULL;
+
+    rb_scan_args(argc, argv, "13", &pass, &salt, &iter, &md_name);
+    rb_check_frozen(self);
+    GetPKCS12(self, p12);
+
+    StringValue(pass);
+    if (!NIL_P(salt))
+        StringValue(salt);
+    if (!NIL_P(iter))
+        iter_i = NUM2INT(iter);
+    if (!NIL_P(md_name))
+        md_type = ossl_evp_get_digestbyname(md_name);
+
+    if (!PKCS12_set_mac(p12, RSTRING_PTR(pass), RSTRING_LENINT(pass),
+                        !NIL_P(salt) ? (unsigned char *)RSTRING_PTR(salt) : NULL,
+                        !NIL_P(salt) ? RSTRING_LENINT(salt) : 0,
+                        iter_i, md_type))
+        ossl_raise(ePKCS12Error, "PKCS12_set_mac");
+
+    return Qnil;
+}
+
 void
 Init_ossl_pkcs12(void)
 {
@@ -276,6 +318,7 @@ Init_ossl_pkcs12(void)
     rb_attr(cPKCS12, rb_intern("ca_certs"), 1, 0, Qfalse);
     rb_define_method(cPKCS12, "initialize", ossl_pkcs12_initialize, -1);
     rb_define_method(cPKCS12, "to_der", ossl_pkcs12_to_der, 0);
+    rb_define_method(cPKCS12, "set_mac", pkcs12_set_mac, -1);
 
     /* MSIE specific PKCS12 key usage extensions */
     rb_define_const(cPKCS12, "KEY_EX", INT2NUM(KEY_EX));

test/openssl/test_pkcs12.rb

@@ -337,6 +337,48 @@ def test_dup
       )
       assert_equal p12.to_der, p12.dup.to_der
     end
+
+    def test_set_mac_pkcs12kdf
+      p12 = OpenSSL::PKCS12.create(
+        "pass",
+        "name",
+        @mykey,
+        @mycert,
+        nil,
+        nil,
+        nil,
+        nil,
+        1234, # mac_iter
+        nil,
+      )
+      macdata = macdata(p12)
+      # Depends on the OpenSSL version: SHA256 in OpenSSL >= 3.0
+      assert_include ["SHA1", "SHA256"], macdata[:mac_algo]
+      assert_equal 1234, macdata[:iter]
+
+      p12.set_mac("pass", "macsalt", 2345, "SHA384")
+      macdata = macdata(p12)
+      assert_equal "SHA384", macdata[:mac_algo]
+      assert_equal "macsalt", macdata[:salt]
+      assert_equal 2345, macdata[:iter]
+      assert_equal @mykey.to_der, OpenSSL::PKCS12.new(p12.to_der, "pass").key.to_der
+    end
+
+    private
+
+    def macdata(p12)
+      # See RFC 7292
+      asn1 = OpenSSL::ASN1.decode(p12.to_der)
+      macdata = asn1.value[2]
+      mac = macdata.value[0]
+      mac_algo = mac.value[0].value[0].value
+      _mac_params = mac.value[0].value[1]
+      {
+        mac_algo: mac_algo,
+        salt: macdata.value[1].value,
+        iter: macdata.value[2]&.value,
+      }
+    end
   end
 end